Chip parts

1. Field of the Invention

The present invention relates to chip parts.

2. Description of the Related Art

Japanese Patent Application Publication No. 2001-76912 discloses a chip resistor that includes an insulating substrate and an electrode formed on one surface of the insulating substrate. The chip resistor is mounted on a mounting substrate by soldering with the one surface of the insulating substrate directed downward.

The inventor of preferred embodiments of the present invention described and claimed in the present application conducted an extensive study and research regarding chip parts, such as the one described above, and in doing so, discovered and first recognized new unique challenges and previously unrecognized possibilities for improvements as described in greater detail below.

In order to prevent the peeling of an electrode in a chip resistor, the adhesion strength of the electrode to a substrate is preferably maximized. This is also a common problem not only to a chip resistor but also to chip parts such as a chip capacitor, a chip diode, and a chip fuse.

Since the surface of the electrode is flat, when a chip part is mounted on a mounting substrate, the chip part is held to a mounter device while being inclined, and thus the electrode may not be recognized. Consequently, the front and rear of the chip part may be erroneously recognized.

An object of the present invention is to provide a chip part that can enhance the adhesion strength of an electrode to a substrate and that can satisfactorily distinguish the front from the rear.

In order to overcome the previously unrecognized and unsolved challenges described above, a chip part according to the present invention includes: a substrate in which an element region and an electrode region are set; an insulating film which is formed on the substrate and which selectively includes an internal concave/convex structure in the electrode region on a surface; an electrode which includes, at a bottom portion, an anchor portion that enters a concave portion of the internal concave/convex structure and which includes an external concave/convex structure in a surface on an opposite side; and a circuit element which is disposed in the element region and which is electrically connected to the electrode.

In this arrangement, since a bonding area of the electrode and the insulating film is increased by the anchor portion, it is possible to enhance the adhesion strength of the electrode to the substrate (the insulating film).

Since the external concave/convex structure is formed in the surface of the electrode, when the chip part is mounted on the mounting substrate, even if the chip part is held to a mounter device while being inclined, it is possible to reflect light from a light source in all directions. Hence, since it is possible to satisfactorily detect the electrode with a part recognizing camera, it is possible to enhance an electrode recognition rate in the mounter device. Consequently, it is possible to reduce the erroneous recognition of the front and rear of the chip part, and thus it is possible to stably mount the chip part.

The external concave/convex structure may include a concave portion in a position opposite the concave portion of the internal concave/convex structure.

The amount of recess of the concave portion in the external concave/convex structure may be less than that of the concave portion in the internal concave/convex structure.

The chip part may further include a wiring film in contact with the circuit element, and the anchor portion may be formed with an extending portion of the wiring film.

In this arrangement, in the same step of the wiring film, the anchor portion can be formed, and thus it is possible to prevent the number of steps from being increased due to the formation of the anchor portion.

The anchor portion may include an intermediate concave/convex structure in a surface thereof.

The anchor portion may integrally include an embedding portion which fills the concave portion in the internal concave/convex structure and a surface layer portion which is disposed along a surface of the insulating film to cover the internal concave/convex structure, and the intermediate concave/convex structure may be formed in a surface of the surface layer portion.

In this arrangement, since the concave portion in the internal concave/convex structure is filled with the embedding portion, and no interface of a different metal is present in the concave portion, it is possible to enhance the strength of the anchor portion itself within the concave portion.

The anchor portion may be formed along a recess and a projection in the internal concave/convex structure.

The electrode may include an external connection portion which is formed on the anchor portion and which is formed of a material different from the anchor portion.

The anchor portion may be formed of an Al—Cu alloy, and the external connection portion may be formed with a Ni—Pd—Au laminated structure.

The insulating film may include a first insulating film and a second insulating film, the chip part may further include: a first wiring film disposed between the first insulating film and the second insulating film; and a second wiring film formed on the second insulating film, the circuit element may be a resistor element which includes a resistor body formed with the first wiring film and the wiring film forming the anchor portion may include at least a pair of resistor wiring films which are formed with the second wiring film and which are connected to the resistor body via the second insulating film.

The concave portion in the internal concave/convex structure may penetrate the second insulating film and may be formed part-way along a direction of thickness of the first insulating film.

In this arrangement, since the bonding area of the electrode to the film on the substrate is further increased by the depth of the through hole, it is possible to further enhance the adhesion strength of the electrode to the substrate (the insulating film).

The insulating film may include a first insulating film and a second insulating film, the chip part may further include: a first wiring film disposed between the first insulating film and the second insulating film; and a second wiring film formed on the second insulating film, the circuit element may be a capacitor which includes a lower electrode formed with the first wiring film, a dielectric film formed with the second insulating film, and an upper electrode formed with the second wiring film and the wiring film forming the anchor portion may include a lower wiring film which is formed with the second wiring film and which is connected to the lower electrode via the second insulating film.

The concave portion in the internal concave/convex structure entered by the lower wiring film may penetrate the second insulating film and may be formed part-way along a direction of thickness of the first insulating film.

In this arrangement, since the bonding area of the electrode to the film on the substrate is further increased by the depth of the through hole of the second insulating film, it is possible to further enhance the adhesion strength of the electrode to the substrate (the insulating film).

The insulating film may further include a third insulating film formed on the second wiring film, the chip part may further include a third wiring film formed on the third insulating film and the wiring film forming the anchor portion may include an upper wiring film which is formed with the third wiring film and which is connected to the upper electrode via the third insulating film.

The concave portion in the internal concave/convex structure entered by the upper wiring film may penetrate the third insulating film and the second insulating film and may be formed part-way along a direction of thickness of the first insulating film.

In this arrangement, since the bonding area of the electrode to the film on the substrate is further increased by the depth of the through hole of the second and third insulating films, it is possible to further enhance the adhesion strength of the electrode to the substrate (the insulating film).

The chip part may further include: a pn bonding portion formed on the substrate; and a first wiring film which is formed on the insulating film and which includes a p-side film and an n-side film connected to the pn bonding portion via the insulating film, the circuit element is a diode which includes the pn bonding portion and the wiring film forming the anchor portion includes at least a pair of films formed with the p-side film and the n-side film.

The concave portions in the external concave/convex structure may be regularly arrayed in plan view.

The concave portions in the external concave/convex structure may be arrayed, in plan view, in a matrix.

The concave portions in the external concave/convex structure may be arrayed, in plan view, in a staggered shape.

The external concave/convex structure may be formed substantially over the entire region of a surface of the electrode.

The external concave/convex structure may be formed along the peripheral edge of the electrode, and the electrode may include, in a region surrounded by the external concave/convex structure, a flat portion formed with a smooth surface.

In this arrangement, when an electrical test is performed on the circuit element, the flat portion is selected as a contact target of the probe, and thus it is possible to satisfactorily prevent the probe from being damaged at the time of contact with the electrode.

The electrode may include the flat portion formed with a smooth surface along the peripheral edge of the electrode, and the external concave/convex structure may be formed in a region surrounded by the flat portion.

In this arrangement, when an electrical test is performed on the circuit element, the flat portion is selected as a contact target of the probe, and thus it is possible to satisfactorily prevent the probe from being damaged at the time of contact with the electrode.

A circuit assembly of the present invention includes the chip part of the present invention and a mounting substrate having a land solder-bonded to the electrode.

An electronic device of the present invention includes the circuit assembly of the present invention and a housing holding the circuit assembly.

A method of manufacturing a chip part according to one aspect of the present invention includes: a step of forming an insulating film on a substrate in which an element region and an electrode region are set; a step of forming a circuit element in the element region; a step of selectively forming an internal concave/convex structure in the electrode region on the surface of the insulating film; and a step of depositing an electrode material on the insulating film to have, at a bottom portion, an anchor portion entering the concave portion of the internal concave/convex structure and to form an electrode having an external concave/convex structure on the surface on the opposite side.

In this method, it is possible to manufacture the chip part according to the present invention.

A method of manufacturing a chip part according to another aspect of the present invention includes: a step of forming a first insulating film on a substrate in which an element region and an electrode region are set; a step of forming, on the first insulating film, a first wiring film used in a part of a circuit element of the element region such that the first wiring film is spread to the element region and the electrode region; a step of selectively removing the part of the first wiring film on the electrode region; a step of forming, after the removal step, a second insulating film covering the first wiring film such that the first wiring film is spread to the element region and the electrode region; a step of selectively forming a through hole in the second insulating film and cutting away a surface portion of the first insulating film by etching via the through hole to form an internal concave/convex structure formed with a plurality of concave portions communicating with the first insulating film and the second insulating film; and a step of depositing an electrode material on the second insulating film to have, at a bottom portion, an anchor portion entering the concave portion of the internal concave/convex structure and to form an electrode having an external concave/convex structure on the surface on the opposite side.

In this method, it is also possible to manufacture the chip part according to the present invention.

The second insulating film may be formed of a material having an etching selection ratio for the first insulating film.

The first insulating film may be formed of SiO 2 , and the second insulating film may be formed of SiN.

The step of forming the internal concave/convex structure may further include a step of forming, in the second insulating film, a second through hole which exposes the first wiring film serving as a part of the circuit element, and the step of forming the electrode may include a step of forming the second wiring film on the second insulating film to form an anchor portion entering the concave portion of the internal concave/convex structure and a via contact embedded in the second through hole.

The step of forming the electrode may include a step of forming the second wiring film by a sputtering method and thereafter growing, from the anchor portion, the plating of a material different from the anchor portion to form an external connection portion.

The step of forming the circuit element may include a step of forming a part of the first wiring film as a resistor body to form a resistor element.

The step of forming the circuit element may include a step of forming a part of the first wiring film as a lower electrode, forming a part of the second insulating film as a dielectric film, and forming a part of the second wiring film as an upper electrode to form a capacitor.

The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings.

FIG. 1 is a schematic perspective view of a chip resistor according to a first preferred embodiment of a first invention.

FIG. 2 is a schematic plan view of the chip resistor shown in FIG. 1 .

FIG. 3 is a partially enlarged view of the resistor portion of FIG. 2 .

FIG. 4 is a cross-sectional view of the resistor portion taken along line IV-IV in FIG. 3 .

FIG. 5 is a cross-sectional view of the resistor portion taken along line V-V in FIG. 3 .

FIG. 6A is a circuit diagram showing the electrical characteristics of a resistor body film line and a first wiring film.

FIG. 6B is a circuit diagram showing the electrical characteristics of the resistor body film line and the first wiring film.

FIG. 7 is a circuit diagram showing the electrical characteristics of the resistor body film line and the first wiring film.

FIG. 8 is a partially enlarged view of the chip resistor of FIG. 2 .

FIG. 9 is a cross-sectional view of the chip resistor taken along line IX-IX in FIG. 8 .

FIG. 10 is an example of a circuit diagram arranged with the resistor body film line and the first wiring film.

FIG. 11 is another example of the circuit diagram arranged with the resistor body film line and the first wiring film.

FIG. 12 is yet another example of the circuit diagram arranged with the resistor body film line and the first wiring film.

FIG. 13 is a schematic cross-sectional view of the chip resistor of FIG. 1 .

FIG. 14 is a partially enlarged view of the chip resistor of FIG. 13 .

FIG. 15A is a diagram showing part of a manufacturing step of the chip resistor of FIG. 13 .

FIG. 15B is a diagram showing the step subsequent to FIG. 15A .

FIG. 15C is a diagram showing the step subsequent to FIG. 15B .

FIG. 15D is a diagram showing the step subsequent to FIG. 15C .

FIG. 15E is a diagram showing the step subsequent to FIG. 15D .

FIG. 15F is a diagram showing the step subsequent to FIG. 15E .

FIG. 15G is a diagram showing the step subsequent to FIG. 15F .

FIG. 15H is a diagram showing the step subsequent to FIG. 15G .

FIG. 15I is a diagram showing the step subsequent to FIG. 15H .

FIG. 15J is a diagram showing the step subsequent to FIG. 15I .

FIG. 15K is a diagram showing the step subsequent to FIG. 15J .

FIG. 15L is a diagram showing the step subsequent to FIG. 15K .

FIG. 15M is a diagram showing the step subsequent to FIG. 15L .

FIG. 16 is a schematic plan view of a resist pattern used to form a groove in the step of FIG. 15I .

FIG. 17 is a diagram for illustrating the manufacturing step of an external connection portion.

FIG. 18A is a diagram for illustrating the recovery step of the chip resistor after the step of FIG. 15M .

FIG. 18B is a diagram showing the step subsequent to FIG. 18A .

FIG. 18C is a diagram showing the step subsequent to FIG. 18B .

FIG. 18D is a diagram showing the step subsequent to FIG. 18C .

FIG. 19A is a diagram for illustrating the recovery step (modification example) of the chip resistor after the step of FIG. 15M .

FIG. 19B is a diagram showing the step subsequent to FIG. 19A .

FIG. 19C is a diagram showing the step subsequent to FIG. 19B .

FIG. 20 is a diagram for illustrating a front/rear judgement step of the chip resistor according to the first invention.

FIG. 21 is a diagram for illustrating a front/rear judgement step of a chip resistor according to a reference example.

FIG. 22 is a diagram showing a circuit assembly in a state where the chip resistor is mounted on a mounting substrate.

FIG. 23 is a diagram of the chip resistor mounted on the mounting substrate when seen from the side of an element formation surface.

FIG. 24 is a schematic cross-sectional view of a chip capacitor according to a second preferred embodiment of the first invention.

FIG. 25 is a schematic cross-sectional view of a chip diode according to a third preferred embodiment of the first invention.

FIG. 26 is a diagram showing a modification example of an external concave/convex structure.

FIG. 27 is a diagram showing another modification example of the external concave/convex structure.

FIG. 28 is a diagram showing a modification example of an anchor portion.

FIG. 29 is a diagram showing a modification example of an internal concave/convex structure.

FIG. 30 is a diagram showing another modification example of the anchor portion.

FIG. 31 is an external view of a smartphone according to a preferred embodiment of the first invention.

FIG. 32 is a diagram for illustrating the internal structure of the smartphone of FIG. 31 .

FIG. 33A is a partially cut perspective view of the chip inductor according to the first preferred embodiment of a second invention.

FIG. 33B is a perspective view showing a coil formed within the chip inductor.

FIG. 34 is a plan view of the chip inductor.

FIG. 35 is a cross-sectional view taken along line XXXV-XXXV in FIG. 34 .

FIG. 36 is a partially enlarged cross-sectional view of FIG. 35 .

FIG. 37 is a cross-sectional view taken along line XXXVII-XXXVII in FIG. 34 .

FIG. 38 is a cross-sectional view taken along line XXXVIII-XXXVIII in FIG. 34 .

FIG. 39 is a plan view showing a structure of the surface of a substrate by removing an arrangement formed on the surface of the substrate.

FIG. 40 is an electrical circuit diagram showing an electrical structure within the chip inductor.

FIG. 41 is a cross-sectional view showing the arrangement of a circuit assembly in which the chip inductor is flip-chip connected on the mounting substrate.

FIG. 42A is a cross-sectional view for illustrating an example of the manufacturing step of the chip inductor.

FIG. 42B is a cross-sectional view showing the step subsequent to FIG. 42A .

FIG. 42C is a cross-sectional view showing the step subsequent to FIG. 42B .

FIG. 42D is a cross-sectional view showing the step subsequent to FIG. 42C .

FIG. 42E is a cross-sectional view showing the step subsequent to FIG. 42D .

FIG. 42F is a cross-sectional view showing the step subsequent to FIG. 42E .

FIG. 42G is a cross-sectional view showing the step subsequent to FIG. 42F .

FIG. 42H is a cross-sectional view showing the step subsequent to FIG. 42G .

FIG. 42I is a cross-sectional view showing the step subsequent to FIG. 42H .

FIG. 42J is a cross-sectional view showing the step subsequent to FIG. 42I .

FIG. 42K is a cross-sectional view showing the step subsequent to FIG. 42J .

FIG. 42L is a cross-sectional view showing the step subsequent to FIG. 42K .

FIG. 43A is a partially enlarged cross-sectional view showing the details of the manufacturing step of a coil.

FIG. 43B is a partially enlarged cross-sectional view showing the step subsequent to FIG. 43A .

FIG. 43C is a partially enlarged cross-sectional view showing the step subsequent to FIG. 43B .

FIG. 43D is a partially enlarged cross-sectional view showing the step subsequent to FIG. 43C .

FIG. 43E is a partially enlarged cross-sectional view showing the step subsequent to FIG. 43D .

FIG. 44 is a plan view of an original substrate that is an original of a substrate main body of the chip inductor, and shows an enlarged view of a region.

FIG. 45A is a cross-sectional view schematically showing the recovery step of the chip inductor after the step of FIG. 42L .

FIG. 45B is a cross-sectional view showing the step subsequent to FIG. 45A .

FIG. 45C is a cross-sectional view showing the step subsequent to FIG. 45B .

FIG. 45D is a cross-sectional view showing the step subsequent to FIG. 45C .

FIG. 46A is a cross-sectional view schematically showing another example of the recovery step of the chip inductor after the step of FIG. 42L .

FIG. 46B is a cross-sectional view showing the step subsequent to FIG. 46A .

FIG. 46C is a cross-sectional view showing the step subsequent to FIG. 46B .

FIG. 47A is a cross-sectional view showing a modification example of an external connection electrode, and shows a cut surface corresponding to FIG. 35 .

FIG. 47B is a cross-sectional view showing the modification example of the external connection electrode, and shows a cut surface corresponding to FIG. 38 .

FIG. 48A is a diagram showing a modification example of a conductive member embedded within a coil formation trench, and is a partially enlarged cross-sectional view corresponding to FIG. 36 .

FIG. 48B is a partially enlarged cross-sectional view of FIG. 48A .

FIG. 49A is a partially enlarged cross-sectional view showing a step of embedding the conductive member of FIG. 48A into the coil formation trench.

FIG. 49B is a partially enlarged cross-sectional view showing the step subsequent to FIG. 49A .

FIG. 49C is a partially enlarged cross-sectional view showing the step subsequent to FIG. 49B .

FIG. 49D is a partially enlarged cross-sectional view showing the step subsequent to FIG. 49C .

FIG. 49E is a partially enlarged cross-sectional view showing the step subsequent to FIG. 49D .

FIG. 49F is a partially enlarged cross-sectional view showing the step subsequent to FIG. 49E .

FIG. 49G is a partially enlarged cross-sectional view showing the step subsequent to FIG. 49F .

FIG. 49H is a partially enlarged cross-sectional view showing the step subsequent to FIG. 49G .

FIG. 49I is a partially enlarged cross-sectional view showing the step subsequent to FIG. 49H .

FIG. 49J is a partially enlarged cross-sectional view showing the step subsequent to FIG. 49I .

FIG. 49K is a partially enlarged cross-sectional view showing the step subsequent to FIG. 49J .

FIG. 50A is a partially cut perspective view of a chip inductor (chip inductor according to a preferred embodiment of a third invention) according to the second preferred embodiment of the second invention.

FIG. 50B is a perspective view showing a coil formed within the chip inductor.

FIG. 51A is a plan view showing the appearance of the chip inductor when seen from the side of the electrode.

FIG. 51B is a plan view showing the internal structure of the chip inductor.

FIG. 52 is a cross-sectional view taken along line LII-LII in FIG. 51B .

FIG. 53 is a partially enlarged cross-sectional view of FIG. 52 .

FIG. 54 is a cross-sectional view taken along line LIV-LIV in FIG. 51B .

FIG. 55 is a cross-sectional view taken along line LV-LV in FIG. 51B .

FIG. 56 is a partially enlarged cross-sectional view of FIG. 55 .

FIG. 57 is a plan view showing a structure of the surface of a substrate by removing a structure formed on the surface of the substrate.

FIG. 58 is an electrical circuit diagram showing an electrical structure within the chip inductor.

FIG. 59 is a cross-sectional view showing the arrangement of a circuit assembly in which the chip inductor is flip-chip connected on the mounting substrate.

FIG. 60A is a cross-sectional view for illustrating an example of the manufacturing step of the chip inductor.

FIG. 60B is a cross-sectional view showing the step subsequent to FIG. 60A .

FIG. 60C is a cross-sectional view showing the step subsequent to FIG. 60B .

FIG. 60D is a cross-sectional view showing the step subsequent to FIG. 60C .

FIG. 60E is a cross-sectional view showing the step subsequent to FIG. 60D .

FIG. 60F is a cross-sectional view showing the step subsequent to FIG. 60E .

FIG. 60G is a cross-sectional view showing the step subsequent to FIG. 60F .

FIG. 60H is a cross-sectional view showing the step subsequent to FIG. 60G .

FIG. 60I is a cross-sectional view showing the step subsequent to FIG. 60H .

FIG. 60J is a cross-sectional view showing the step subsequent to FIG. 60I .

FIG. 60K is a cross-sectional view showing the step subsequent to FIG. 60J .

FIG. 60L is a cross-sectional view showing the step subsequent to FIG. 60K .

FIG. 61A is a partially enlarged cross-sectional view showing the details of the manufacturing step of a coil.

FIG. 61B is a partially enlarged cross-sectional view showing the step subsequent to FIG. 61A .

FIG. 61C is a partially enlarged cross-sectional view showing the step subsequent to FIG. 61B .

FIG. 61D is a partially enlarged cross-sectional view showing the step subsequent to FIG. 61C .

FIG. 61E is a partially enlarged cross-sectional view showing the step subsequent to FIG. 61D .

FIG. 62A is an enlarged cross-sectional view showing the details of the manufacturing step of a concave portion of a first electrode.

FIG. 62B is a partially enlarged cross-sectional view showing the step subsequent to FIG. 62A .

FIG. 62C is a partially enlarged cross-sectional view showing the step subsequent to FIG. 62B .

FIG. 62D is a partially enlarged cross-sectional view showing the step subsequent to FIG. 62 C.

FIG. 62E is a partially enlarged cross-sectional view showing the step subsequent to FIG. 62D .

FIG. 62F is a partially enlarged cross-sectional view showing the step subsequent to FIG. 62E .

FIG. 63 is a plan view of an original substrate that is an original of a substrate main body of the chip inductor, and shows an enlarged view of a region.

FIG. 64A is a partially cut perspective view of a chip inductor according to the third preferred embodiment of the second invention.

FIG. 64B is a perspective view showing a coil formed within the chip inductor.

FIG. 65A is a plan view showing the appearance of the chip inductor when seen from the side of the electrode.

FIG. 65B is a plan view showing the internal structure of the chip inductor.

FIG. 66 is a cross-sectional view taken along line LXVI-LXVI in FIG. 65B .

FIG. 67 is a partially enlarged cross-sectional view of FIG. 66 .

FIG. 68 is a cross-sectional view taken along line LXVIII-LXVIII in FIG. 65B .

FIG. 69 is a cross-sectional view taken along line LXIX-LXIX in FIG. 65B .

FIG. 70 is a partially enlarged cross-sectional view of FIG. 69 .

FIG. 71 is a cross-sectional view taken along line LXXI-LXXI in FIG. 65B .

FIG. 72 is a plan view showing a structure of the surface of a substrate by removing an arrangement formed on the surface of the substrate.

FIG. 73 is an electrical circuit diagram showing an electrical structure within the chip inductor.

FIG. 74 is a cross-sectional view showing the arrangement of a circuit assembly in which the chip inductor is flip-chip connected on the mounting substrate.

FIG. 75A is a cross-sectional view showing a modification example of the external connection electrode for the chip inductor of the second preferred embodiment and the third preferred embodiment of the second invention, and shows a cut surface corresponding to FIG. 52 ( FIG. 66 ).

FIG. 75B is a cross-sectional view showing the modification example of the external connection electrode for the chip inductor of the second preferred embodiment and the third preferred embodiment of the second invention, and shows a cut surface corresponding to FIG. 55 ( FIG. 69 ).

FIG. 76A is a partially cut perspective view of a chip inductor according to a fourth preferred embodiment of the second invention.

FIG. 76B is a perspective view showing a coil formed within the chip inductor.

FIG. 77 is a plan view of the chip inductor.

FIG. 78 is a cross-sectional view taken along line LXXVIII-LXXVIII in FIG. 77 .

FIG. 79 is a partially enlarged cross-sectional view of FIG. 78 .

FIG. 80 is a cross-sectional view taken along line LXXX-LXXX in FIG. 77 .

FIG. 81 is a cross-sectional view taken along line LXXXI-LXXXI in FIG. 77 .

FIG. 82 is a plan view showing a structure of the surface of a substrate by removing an arrangement formed on the surface of the substrate.

FIG. 83 is an electrical circuit diagram showing an electrical structure within the chip inductor.

FIG. 84 is a cross-sectional view showing the arrangement of a circuit assembly in which the chip inductor is flip-chip connected on the mounting substrate.

FIG. 85A is a cross-sectional view for illustrating an example of the manufacturing step of the chip inductor.

FIG. 85B is a cross-sectional view showing the step subsequent to FIG. 85A .

FIG. 85C is a cross-sectional view showing the step subsequent to FIG. 85B .

FIG. 85D is a cross-sectional view showing the step subsequent to FIG. 85C .

FIG. 85E is a cross-sectional view showing the step subsequent to FIG. 85D .

FIG. 85F is a cross-sectional view showing the step subsequent to FIG. 85E .

FIG. 85G is a cross-sectional view showing the step subsequent to FIG. 85F .

FIG. 85H is a cross-sectional view showing the step subsequent to FIG. 85G .

FIG. 85I is a cross-sectional view showing the step subsequent to FIG. 85H .

FIG. 85J is a cross-sectional view showing the step subsequent to FIG. 85I .

FIG. 85K is a cross-sectional view showing the step subsequent to FIG. 85J .

FIG. 85L is a cross-sectional view showing the step subsequent to FIG. 85K .

FIG. 85M is a cross-sectional view showing the step subsequent to FIG. 85L .

FIG. 86A is a partially enlarged cross-sectional view showing the details of the manufacturing step of a coil.

FIG. 86B is a partially enlarged cross-sectional view showing the step subsequent to FIG. 86A .

FIG. 86C is a partially enlarged cross-sectional view showing the step subsequent to FIG. 86B .

FIG. 86D is a partially enlarged cross-sectional view showing the step subsequent to FIG. 86C .

FIG. 86E is a partially enlarged cross-sectional view showing the step subsequent to FIG. 86D .

FIG. 86F is a partially enlarged cross-sectional view showing the step subsequent to FIG. 86E .

FIG. 87 is a plan view of an original substrate that is an original of a substrate main body of the chip inductor, and shows an enlarged view of a partial region.

FIG. 88A is a cross-sectional view showing a modification example of an external connection electrode, and shows a cut surface corresponding to FIG. 78 .

FIG. 88B is a cross-sectional view showing the modification example of the external connection electrode, and shows a cut surface corresponding to FIG. 81 .

FIG. 89 is a plan view showing a modification example of the coil.

FIG. 90 is an electrical circuit diagram showing an electrical structure within the chip inductor of FIG. 89 .

FIG. 91 is a plan view showing another modification example of the coil.

FIG. 92 is a plan view showing yet another modification example of the coil.

FIG. 93A is a partially cut perspective view of a chip transformer according to a first preferred embodiment of a fourth invention.

FIG. 93B is a perspective view showing a primary coil and a secondary coil formed within the chip transformer.

FIG. 94 is a plan view of the chip transformer.

FIG. 95A is a cross-sectional view taken along line XCVA-XCVA in FIG. 94 .

FIG. 95B is a partially enlarged cross-sectional view of FIG. 95A .

FIG. 96A is a cross-sectional view taken along line XCVIA-XCVIA in FIG. 94 .

FIG. 96B is a partially enlarged cross-sectional view of FIG. 96A .

FIG. 97 is a cross-sectional view taken along line XCVII-XCVII in FIG. 94 .

FIG. 98 is a cross-sectional view taken along line XCVIII-XCVIII in FIG. 94 .

FIG. 99 is a plan view showing a structure of the surface of a substrate by removing a structure formed on the surface of the substrate.

FIG. 100 is an electrical circuit diagram showing an electrical structure within the chip transformer.

FIG. 101 is a cross-sectional view showing the arrangement of a circuit assembly in which the chip transformer is flip-chip connected on the mounting substrate.

FIG. 102A is a cross-sectional view for illustrating an example of the manufacturing step of the chip transformer, and is a cut surface corresponding to FIG. 95A .

FIG. 102B is a cross-sectional view showing the step subsequent to FIG. 102A .

FIG. 102C is a cross-sectional view showing the step subsequent to FIG. 102B .

FIG. 102D is a cross-sectional view showing the step subsequent to FIG. 102C .

FIG. 102E is a cross-sectional view showing the step subsequent to FIG. 102D .

FIG. 102F is a cross-sectional view showing the step subsequent to FIG. 102E .

FIG. 102G is a cross-sectional view showing the step subsequent to FIG. 102F .

FIG. 102H is a cross-sectional view showing the step subsequent to FIG. 102G .

FIG. 102I is a cross-sectional view showing the step subsequent to FIG. 102H .

FIG. 102J is a cross-sectional view showing the step subsequent to FIG. 102I .

FIG. 102K is a cross-sectional view showing the step subsequent to FIG. 102J .

FIG. 102L is a cross-sectional view showing the step subsequent to FIG. 102K .

FIG. 103A is a partially enlarged cross-sectional view showing the details of the manufacturing step of a coil.

FIG. 103B is a partially enlarged cross-sectional view showing the step subsequent to FIG. 103A .

FIG. 103C is a partially enlarged cross-sectional view showing the step subsequent to FIG. 103B .

FIG. 103D is a partially enlarged cross-sectional view showing the step subsequent to FIG. 103C .

FIG. 103E is a partially enlarged cross-sectional view showing the step subsequent to FIG. 103D .

FIG. 104A is a cross-sectional view for illustrating an example of the manufacturing step of the chip transformer, and is a cut surface corresponding to FIG. 96A .

FIG. 104B is a cross-sectional view showing the step subsequent to FIG. 104A .

FIG. 104C is a cross-sectional view showing the step subsequent to FIG. 104B .

FIG. 104D is a cross-sectional view showing the step subsequent to FIG. 104C .

FIG. 104E is a cross-sectional view showing the step subsequent to FIG. 104D .

FIG. 104F is a cross-sectional view showing the step subsequent to FIG. 104E .

FIG. 104G is a cross-sectional view showing the step subsequent to FIG. 104F .

FIG. 104H is a cross-sectional view showing the step subsequent to FIG. 104G .

FIG. 104I is a cross-sectional view showing the step subsequent to FIG. 104H .

FIG. 104J is a cross-sectional view showing the step subsequent to FIG. 104I .

FIG. 104K is a cross-sectional view showing the step subsequent to FIG. 104J .

FIG. 104L is a cross-sectional view showing the step subsequent to FIG. 104K .

FIG. 105 is a plan view of an original substrate that is an original of a substrate main body of the chip transformer, and shows an enlarged view of a partial region.

FIG. 106A is a partially cut perspective view of a chip transformer according to a second preferred embodiment of the fourth invention.

FIG. 106B is a perspective view showing a primary coil and a secondary coil formed within the chip transformer.

FIG. 107A is a plan view showing the appearance of the chip transformer when seen from the side of the electrode.

FIG. 107B is a plan view showing the internal structure of the chip transformer.

FIG. 108A is a cross-sectional view taken along line CVIIIA-CVIIIA in FIG. 107B .

FIG. 108B is a partially enlarged cross-sectional view of FIG. 108A .

FIG. 109A is a cross-sectional view taken along line CIXA-CIXA in FIG. 107B .

FIG. 109B is a partially enlarged cross-sectional view of FIG. 109A .

FIG. 110 is a cross-sectional view taken along line CX-CX in FIG. 107B .

FIG. 111 is a cross-sectional view taken along line CXI-CXI in FIG. 107B .

FIG. 112 is a partially enlarged cross-sectional view of FIG. 111 .

FIG. 113 is a cross-sectional view taken along line CXIII-CXIII in FIG. 107B .

FIG. 114 is a plan view showing a structure of the surface of a substrate by removing an arrangement formed on the surface of the substrate.

FIG. 115 is an electrical circuit diagram showing an electrical structure within the chip transformer.

FIG. 116 is a cross-sectional view showing the structure of a circuit assembly in which the chip transformer is flip-chip connected on the mounting substrate.

FIG. 117A is an enlarged cross-sectional view showing the details of the manufacturing step of a first concave portion.

FIG. 117B is a cross-sectional view showing the step subsequent to FIG. 117A .

FIG. 117C is a cross-sectional view showing the step subsequent to FIG. 117B .

FIG. 117D is a cross-sectional view showing the step subsequent to FIG. 117C .

FIG. 117E is a cross-sectional view showing the step subsequent to FIG. 117D .

FIG. 117F is a cross-sectional view showing the step subsequent to FIG. 117E .

FIG. 118 is a partially cut perspective view of a chip transformer according to a third preferred embodiment of the fourth invention.

FIG. 119 is a plan view of a chip transformer.

FIG. 120 is a cross-sectional view taken along line CXX-CXX in FIG. 119 .

FIG. 121 is a partially enlarged cross-sectional view of FIG. 120 .

FIG. 122 is a cross-sectional view taken along line CXXII-CXXII in FIG. 119 .

FIG. 123 is a cross-sectional view taken along line CXXIII-CXXIII in FIG. 119 .

FIG. 124 is a cross-sectional view taken along line CXXIV-CXXIV in FIG. 119 .

FIG. 125 is a cross-sectional view taken along line CXXV-CXXV in FIG. 119 .

FIG. 126 is a plan view showing a structure of the surface of a substrate by removing an arrangement formed on the surface of the substrate.

FIG. 127 is an electrical circuit diagram showing an electrical structure within the chip transformer.

FIG. 128 is a cross-sectional view showing the structure of a circuit assembly in which the chip transformer is flip-chip connected on the mounting substrate.

FIG. 129A is a cross-sectional view for illustrating an example of the manufacturing step of the chip transformer, and is a cut surface corresponding to FIG. 120 .

FIG. 129B is a cross-sectional view showing the step subsequent to FIG. 129A .

FIG. 129C is a cross-sectional view showing the step subsequent to FIG. 129B .

FIG. 129D is a cross-sectional view showing the step subsequent to FIG. 129C .

FIG. 129E is a cross-sectional view showing the step subsequent to FIG. 129D .

FIG. 129F is a cross-sectional view showing the step subsequent to FIG. 129E .

FIG. 129G is a cross-sectional view showing the step subsequent to FIG. 129F .

FIG. 129H is a cross-sectional view showing the step subsequent to FIG. 129G .

FIG. 129I is a cross-sectional view showing the step subsequent to FIG. 129H .

FIG. 129J is a cross-sectional view showing the step subsequent to FIG. 129I .

FIG. 129K is a cross-sectional view showing the step subsequent to FIG. 129J .

FIG. 129L is a cross-sectional view showing the step subsequent to FIG. 129K .

FIG. 130A is a partially enlarged cross-sectional view showing the details of the manufacturing step of a coil.

FIG. 130B is a partially enlarged cross-sectional view showing the step subsequent to FIG. 130A .

FIG. 130C is a partially enlarged cross-sectional view showing the step subsequent to FIG. 130 B.

FIG. 130D is a partially enlarged cross-sectional view showing the step subsequent to FIG. 130C .

FIG. 130E is a partially enlarged cross-sectional view showing the step subsequent to FIG. 130D .

FIG. 131 is a plan view of an original substrate that is an original of a substrate main body of the chip transformer, and shows an enlarged view of a partial region.

FIG. 132 is a partially cut perspective view of a chip transformer according to a fourth preferred embodiment of the fourth invention.

FIG. 133A is a plan view showing the appearance of the chip transformer when seen from the side of the electrode.

FIG. 133B is a plan view showing the internal structure of the chip transformer.

FIG. 134 is a cross-sectional view taken along line CXXXIV-CXXXIV in FIG. 133B .

FIG. 135 is a partially enlarged cross-sectional view of FIG. 134 .

FIG. 136 is a cross-sectional view taken along line CXXXVI-CXXXVI in FIG. 133B .

FIG. 137 is a cross-sectional view taken along line CXXXVII-CXXXVII in FIG. 133B .

FIG. 138 is a cross-sectional view taken along line CXXXVIII-CXXXVIII in FIG. 133B .

FIG. 139 is a cross-sectional view taken along line CXXXIX-CXXXIX in FIG. 133B .

FIG. 140 is a partially enlarged cross-sectional view of FIG. 139 .

FIG. 141 is a plan view showing a structure of the surface of a substrate by removing an arrangement formed on the surface of the substrate.

FIG. 142 is an electrical circuit diagram showing an electrical structure within the chip transformer.

FIG. 143 is a cross-sectional view showing the arrangement of a circuit assembly in which the chip transformer is flip-chip connected on the mounting substrate.

FIG. 144A is an enlarged cross-sectional view showing the details of the manufacturing step of the first concave portion.

FIG. 144B is a cross-sectional view showing the step subsequent to FIG. 144A .

FIG. 144C is a cross-sectional view showing the step subsequent to FIG. 144B .

FIG. 144D is a cross-sectional view showing the step subsequent to FIG. 144C .

FIG. 144E is a cross-sectional view showing the step subsequent to FIG. 144D .

FIG. 144F is a cross-sectional view showing the step subsequent to FIG. 144E .

FIG. 145 is a partially cut perspective view of a chip capacitor according to a preferred embodiment of a fifth invention.

FIG. 146 is a plan view of the chip capacitor.

FIG. 147 is a cross-sectional view taken along line CXLVII-CXLVII in FIG. 146 .

FIG. 148 is a cross-sectional view taken along line CXLVIII-CXLVIII in FIG. 146 .

FIG. 149 is a partially enlarged cross-sectional view of FIG. 148 .

FIG. 150 is a cross-sectional view taken along line CL-CL in FIG. 146 .

FIG. 151 is a cross-sectional view taken along line CLI-CLI in FIG. 146 .

FIG. 152 is a plan view showing a structure of the surface of a substrate by removing an arrangement formed on the surface of the substrate.

FIG. 153 is an electrical circuit diagram showing an electrical structure within the chip capacitor.

FIG. 154 is a cross-sectional view showing the structure of a circuit assembly in which the chip capacitor is flip-chip connected on the mounting substrate.

FIG. 155A is a cross-sectional view for illustrating an example of the manufacturing step of the chip capacitor, and is a cut surface corresponding to FIG. 147 .

FIG. 155B is a cross-sectional view showing the step subsequent to FIG. 155A .

FIG. 155C is a cross-sectional view showing the step subsequent to FIG. 155B .

FIG. 155D is a cross-sectional view showing the step subsequent to FIG. 155C .

FIG. 155E is a cross-sectional view showing the step subsequent to FIG. 155D .

FIG. 155F is a cross-sectional view showing the step subsequent to FIG. 155E .

FIG. 155G is a cross-sectional view showing the step subsequent to FIG. 155F .

FIG. 155H is a cross-sectional view showing the step subsequent to FIG. 155G .

FIG. 155I is a cross-sectional view showing the step subsequent to FIG. 155H .

FIG. 155J is a cross-sectional view showing the step subsequent to FIG. 155I .

FIG. 155K is a cross-sectional view showing the step subsequent to FIG. 155J .

FIG. 155L is a cross-sectional view showing the step subsequent to FIG. 155K .

FIG. 156A is a cross-sectional view for illustrating an example of the manufacturing step of the chip capacitor, and is a cross-sectional view corresponding to FIG. 148 .

FIG. 156B is a cross-sectional view showing the step subsequent to FIG. 156A .

FIG. 156C is a cross-sectional view showing the step subsequent to FIG. 156B .

FIG. 156D is a cross-sectional view showing the step subsequent to FIG. 156C .

FIG. 156E is a cross-sectional view showing the step subsequent to FIG. 156D .

FIG. 156F is a cross-sectional view showing the step subsequent to FIG. 156E .

FIG. 156G is a cross-sectional view showing the step subsequent to FIG. 156F .

FIG. 156H is a cross-sectional view showing the step subsequent to FIG. 156G .

FIG. 156I is a cross-sectional view showing the step subsequent to FIG. 156H .

FIG. 156J is a cross-sectional view showing the step subsequent to FIG. 156I .

FIG. 156K is a cross-sectional view showing the step subsequent to FIG. 156J .

FIG. 156L is a cross-sectional view showing the step subsequent to FIG. 156K .

FIG. 157A is a partially enlarged cross-sectional view showing the details of the manufacturing step of a first internal electrode and a second internal electrode.

FIG. 157B is a partially enlarged cross-sectional view showing the step subsequent to FIG. 157 A.

FIG. 157C is a partially enlarged cross-sectional view showing the step subsequent to FIG. 157B .

FIG. 157D is a partially enlarged cross-sectional view showing the step subsequent to FIG. 157C .

FIG. 157E is a partially enlarged cross-sectional view showing the step subsequent to FIG. 157D .

FIG. 158 is a plan view of an original substrate that is an original of a substrate main body of the chip capacitor, and shows an enlarged view of a partial region.

FIG. 159A is a cross-sectional view showing a modification example of an external connection electrode, and shows a cut surface corresponding to FIG. 147 .

FIG. 159B is a cross-sectional view showing the modification example of the external connection electrode, and shows a cut surface corresponding to FIG. 148 .

FIG. 160A is a diagram showing a modification example of a conductive member embedded within an internal electrode formation trench, and is a partially enlarged cross-sectional view corresponding to FIG. 148 .

FIG. 160B is a partially enlarged cross-sectional view of FIG. 160A .

FIG. 161 is a partially cut perspective view of an LC composite element chip according to a first preferred embodiment of a sixth invention.

FIG. 162 is a plan view of the LC composite element chip.

FIG. 163A is a cross-sectional view taken along line CLXIIIA-CLXIIIA in FIG. 162 .

FIG. 163B is a partially enlarged cross-sectional view of FIG. 163A .

FIG. 164A is a cross-sectional view taken along line CLXIVA-CLXIVA in FIG. 162 .

FIG. 164B is a partially enlarged cross-sectional view of FIG. 164A .

FIG. 165 is a cross-sectional view taken along line CLXV-CLXV in FIG. 162 .

FIG. 166 is a cross-sectional view taken along line CLXVI-CLXVI in FIG. 162 .

FIG. 167 is a cross-sectional view taken along line CLXVII-CLXVII in FIG. 162 .

FIG. 168 is a cross-sectional view taken along line CLXVIII-CLXVIII in FIG. 162 .

FIG. 169 is a plan view showing a structure of the surface of a substrate by removing an arrangement formed on the surface of the substrate.

FIG. 170 is an electrical circuit diagram showing an electrical structure within the LC composite element chip.

FIG. 171 is a cross-sectional view showing the arrangement of a circuit assembly in which the LC composite element chip is flip-chip connected on the mounting substrate.

FIG. 172A is a cross-sectional view for illustrating an example of the manufacturing step of the LC composite element chip, and is a cross-sectional view corresponding to FIG. 163A .

FIG. 172B is a cross-sectional view showing the step subsequent to FIG. 172A .

FIG. 172C is a cross-sectional view showing the step subsequent to FIG. 172B .

FIG. 172D is a cross-sectional view showing the step subsequent to FIG. 172C .

FIG. 172E is a cross-sectional view showing the step subsequent to FIG. 172D .

FIG. 172F is a cross-sectional view showing the step subsequent to FIG. 172E .

FIG. 172G is a cross-sectional view showing the step subsequent to FIG. 172F .

FIG. 172H is a cross-sectional view showing the step subsequent to FIG. 172G .

FIG. 172I is a cross-sectional view showing the step subsequent to FIG. 172H .

FIG. 172J is a cross-sectional view showing the step subsequent to FIG. 172I .

FIG. 172K is a cross-sectional view showing the step subsequent to FIG. 172J .

FIG. 172L is a cross-sectional view showing the step subsequent to FIG. 172K .

FIG. 173A is a cross-sectional view for illustrating an example of the manufacturing step of the LC composite element chip, and is a cross-sectional view corresponding to FIG. 164A .

FIG. 173B is a cross-sectional view showing the step subsequent to FIG. 173A .

FIG. 173C is a cross-sectional view showing the step subsequent to FIG. 173B .

FIG. 173D is a cross-sectional view showing the step subsequent to FIG. 173C .

FIG. 173E is a cross-sectional view showing the step subsequent to FIG. 173D .

FIG. 173F is a cross-sectional view showing the step subsequent to FIG. 173E .

FIG. 173G is a cross-sectional view showing the step subsequent to FIG. 173F .

FIG. 173H is a cross-sectional view showing the step subsequent to FIG. 173G .

FIG. 173I is a cross-sectional view showing the step subsequent to FIG. 173H .

FIG. 173J is a cross-sectional view showing the step subsequent to FIG. 173I .

FIG. 173K is a cross-sectional view showing the step subsequent to FIG. 173J .

FIG. 173L is a cross-sectional view showing the step subsequent to FIG. 173K .

FIG. 174A is a partially enlarged cross-sectional view showing the details of the manufacturing step of the first internal electrode and the second internal electrode, and is a cross-sectional view corresponding to FIG. 164B .

FIG. 174B is a partially enlarged cross-sectional view showing the step subsequent to FIG. 174A .

FIG. 174C is a partially enlarged cross-sectional view showing the step subsequent to FIG. 174B .

FIG. 174D is a partially enlarged cross-sectional view showing the step subsequent to FIG. 174C .

FIG. 174E is a partially enlarged cross-sectional view showing the step subsequent to FIG. 174D .

FIG. 175 is a plan view of an original substrate that is an original of a substrate main body of the LC composite element chip, and shows an enlarged view of a partial region.

FIG. 176A is a diagram showing a modification example of a conductive member embedded within a coil formation trench, and is a partially enlarged cross-sectional view corresponding to FIG. 163 A.

FIG. 176B is a partially enlarged cross-sectional view of FIG. 176A .

FIG. 177A is a diagram showing a modification example of a conductive member embedded within each of internal electrode formation trenches, and is a partially enlarged cross-sectional view corresponding to FIG. 164A .

FIG. 177B is a partially enlarged cross-sectional view of FIG. 177A .

FIG. 178 is a partially cut perspective view of an LC composite element chip according to a second preferred embodiment of the sixth invention.

FIG. 179 is a plan view of the LC composite element chip.

FIG. 180 is a cross-sectional view taken along line CLXXX-CLXXX in FIG. 179 .

FIG. 181A is a cross-sectional view taken along line CLXXXIA-CLXXXIA in FIG. 179 .

FIG. 181B is a partially enlarged cross-sectional view of FIG. 181A .

FIG. 182A is a cross-sectional view taken along line CLXXXIIA-CLXXXIIA in FIG. 179 .

FIG. 182B is a partially enlarged cross-sectional view of FIG. 182A .

FIG. 183 is a cross-sectional view taken along line CLXXXIII-CLXXXIII in FIG. 179 .

FIG. 184 is a cross-sectional view taken along line CLXXXIV-CLXXXIV in FIG. 179 .

FIG. 185 is a cross-sectional view taken along line CLXXXV-CLXXXV in FIG. 179 .

FIG. 186 is a plan view showing a structure of the surface of a substrate by removing an arrangement formed on the surface of the substrate.

FIG. 187 is an electrical circuit diagram showing an electrical structure within the LC composite element chip.

FIG. 188 is a cross-sectional view showing the structure of a circuit assembly in which the LC composite element chip is flip-chip connected on the mounting substrate.

FIG. 189A is a cross-sectional view for illustrating an example of the manufacturing step of the LC composite element chip, and is a cross-sectional view corresponding to FIG. 180 .

FIG. 189B is a cross-sectional view showing the step subsequent to FIG. 189A .

FIG. 189C is a cross-sectional view showing the step subsequent to FIG. 189B .

FIG. 189D is a cross-sectional view showing the step subsequent to FIG. 189C .

FIG. 189E is a cross-sectional view showing the step subsequent to FIG. 189D .

FIG. 189F is a cross-sectional view showing the step subsequent to FIG. 189E .

FIG. 189G is a cross-sectional view showing the step subsequent to FIG. 189F .

FIG. 189H is a cross-sectional view showing the step subsequent to FIG. 189G .

FIG. 189I is a cross-sectional view showing the step subsequent to FIG. 189H .

FIG. 189J is a cross-sectional view showing the step subsequent to FIG. 189I .

FIG. 189K is a cross-sectional view showing the step subsequent to FIG. 189J .

FIG. 189L is a cross-sectional view showing the step subsequent to FIG. 189K .

FIG. 190A is a cross-sectional view for illustrating an example of the manufacturing step of the LC composite element chip, and is a cross-sectional view corresponding to FIG. 181A .

FIG. 190B is a cross-sectional view showing the step subsequent to FIG. 190A .

FIG. 190C is a cross-sectional view showing the step subsequent to FIG. 190B .

FIG. 190D is a cross-sectional view showing the step subsequent to FIG. 190C .

FIG. 190E is a cross-sectional view showing the step subsequent to FIG. 190D .

FIG. 190F is a cross-sectional view showing the step subsequent to FIG. 190E .

FIG. 190G is a cross-sectional view showing the step subsequent to FIG. 190F .

FIG. 190H is a cross-sectional view showing the step subsequent to FIG. 190G .

FIG. 190I is a cross-sectional view showing the step subsequent to FIG. 190H .

FIG. 190J is a cross-sectional view showing the step subsequent to FIG. 190I .

FIG. 190K is a cross-sectional view showing the step subsequent to FIG. 190J .

FIG. 190L is a cross-sectional view showing the step subsequent to FIG. 190K .

FIG. 191A is a cross-sectional view for illustrating an example of the manufacturing step of the LC composite element chip, and is a cross-sectional view corresponding to FIG. 182A .

FIG. 191B is a cross-sectional view showing the step subsequent to FIG. 191A .

FIG. 191C is a cross-sectional view showing the step subsequent to FIG. 191B .

FIG. 191D is a cross-sectional view showing the step subsequent to FIG. 191C .

FIG. 191E is a cross-sectional view showing the step subsequent to FIG. 191D .

FIG. 191F is a cross-sectional view showing the step subsequent to FIG. 191E .

FIG. 191G is a cross-sectional view showing the step subsequent to FIG. 191F .

FIG. 191H is a cross-sectional view showing the step subsequent to FIG. 191G .

FIG. 191I is a cross-sectional view showing the step subsequent to FIG. 191H .

FIG. 191J is a cross-sectional view showing the step subsequent to FIG. 191I .

FIG. 191K is a cross-sectional view showing the step subsequent to FIG. 191J .

FIG. 191L is a cross-sectional view showing the step subsequent to FIG. 191K .

FIG. 192A is a partially enlarged cross-sectional view showing the details of the manufacturing step of the first internal electrode and the second internal electrode, and is a cross-sectional view corresponding to FIG. 182B .

FIG. 192B is a partially enlarged cross-sectional view showing the step subsequent to FIG. 192A .

FIG. 192C is a partially enlarged cross-sectional view showing the step subsequent to FIG. 192B .

FIG. 192D is a partially enlarged cross-sectional view showing the step subsequent to FIG. 192C .

FIG. 192E is a partially enlarged cross-sectional view showing the step subsequent to FIG. 192D .

FIG. 193A is a diagram showing a modification example of a conductive member embedded within a coil formation trench, and is a partially enlarged cross-sectional view corresponding to FIG. 181 A.

FIG. 193B is a partially enlarged cross-sectional view of FIG. 193A .

FIG. 194A is a diagram showing a modification example of a conductive member embedded within each of internal electrode formation trenches, and is a partially enlarged cross-sectional view corresponding to FIG. 182A .

FIG. 194B is a partially enlarged cross-sectional view of FIG. 194A .

FIG. 195 is a partially cut perspective view of an LC composite element chip according to a third preferred embodiment of the sixth invention.

FIG. 196 is a plan view of the LC composite element chip.

FIG. 197 is an electrical circuit diagram showing an electrical structure within the LC composite element chip.

FIG. 198 is a plan view showing a modification example of the coil.

FIG. 199 is a partially enlarged cross-sectional view showing an arrangement when a seed layer cannot be visually recognized in the conductive member shown in FIG. 48A .

FIG. 200 is a schematic perspective view of a chip capacitor according to a preferred embodiment of an eighth invention.

FIG. 201 is a schematic plan view of the chip capacitor shown in FIG. 200 .

FIG. 202 is a cross-sectional view taken along line CCII-CCII in FIG. 201 .

FIG. 203 is an equivalent circuit diagram of the chip capacitor shown in FIG. 200 .

FIG. 204 is a table showing the specifications of an evaluation element of the chip capacitor shown in FIG. 200 .

FIG. 205 is a graph showing the frequency characteristics of the evaluation element shown in FIG. 204 , and is a graph showing the resistivity versus equivalent series resistance of the substrate.

FIG. 206 is a graph showing the frequency characteristics of the evaluation element shown in FIG. 204 , and is a graph showing the resistivity versus Q value (Quality Factor) of the substrate.

FIG. 207A is a cross-sectional view for illustrating an example of the manufacturing step of the chip capacitor shown in FIG. 200 .

FIG. 207B is a cross-sectional view showing the step subsequent to FIG. 207A .

FIG. 207C is a cross-sectional view showing the step subsequent to FIG. 207B .

FIG. 207D is a cross-sectional view showing the step subsequent to FIG. 207C .

FIG. 207E is a cross-sectional view showing the step subsequent to FIG. 207D .

FIG. 207F is a cross-sectional view showing the step subsequent to FIG. 207E .

FIG. 207G is a cross-sectional view showing the step subsequent to FIG. 207F .

FIG. 207H is a cross-sectional view showing the step subsequent to FIG. 207G .

FIG. 207I is a cross-sectional view showing the step subsequent to FIG. 207H .

FIG. 208 is a schematic plan view of part of a base substrate where an insulating film is formed on the surface.

FIG. 209A is a cross-sectional view schematically showing the recovery step of the chip capacitor after the step of FIG. 207I .

FIG. 209B is a cross-sectional view showing the step subsequent to FIG. 209A .

FIG. 209C is a cross-sectional view showing the step subsequent to FIG. 209B .

FIG. 209D is a cross-sectional view showing the step subsequent to FIG. 209C .

FIG. 210A is a cross-sectional view schematically showing another example of the recovery step of the chip capacitor after the step of FIG. 207I .

FIG. 210B is a cross-sectional view showing the step subsequent to FIG. 210A .

FIG. 210C is a cross-sectional view showing the step subsequent to FIG. 210B .

FIG. 211 is a cross-sectional view showing the arrangement of a circuit assembly in which the chip capacitor shown in FIG. 200 is flip-chip connected on the mounting substrate.

FIG. 212 is a schematic cross-sectional view of a chip capacitor according to a first modification example.

FIG. 213 is a schematic cross-sectional view of a chip capacitor according to a second modification example.

FIG. 214 is a schematic plan view of a chip capacitor according to a third modification example.

FIG. 215 is a schematic perspective view of a chip capacitor according to a fourth modification example.

FIG. 216 is a schematic perspective view of a chip capacitor according to a fifth modification example.

Preferred embodiments of first to eighth inventions will be described in detail below with reference to accompanying drawings.

[1] First Invention

FIG. 1 is a schematic perspective view of a chip resistor 1 according to the first preferred embodiment of the first invention.

The chip resistor 1 is a minute chip part. The chip resistor 1 is formed in the shape of a rectangular parallelepiped. The planar shape of the chip resistor 1 may be either rectangular or square. For example, the chip resistor 1 may be a rectangle (0103 chip) with its long and short sides perpendicular to each other respectively having 0.6 mm or less and 0.3 mm or less or may be a rectangle (0402 chip) with the long and short sides respectively having 0.4 mm or less and 0.2 mm or less. In the preferred embodiment, the chip resistor 1 is formed with a 03015 size having a length L 1 of about 0.3 mm, a width W 1 of about 0.15 mm and a thickness T 1 of about 0.1 mm.

The chip resistor 1 mainly includes a substrate 2 that forms the main body of the chip resistor 1 , a first connection electrode 3 and a second connection electrode 4 serving as external connection electrodes and an element region 5 .

The substrate 2 is formed substantially in the shape of a rectangular parallelepiped (chip shape). In the substrate 2 , one surface forming the upper surface in FIG. 1 is an element formation surface 2 A. The element formation surface 2 A is a surface where circuit elements are formed in the substrate 2 . The surface on the opposite side to the element formation surface 2 A in the direction of thickness of the substrate 2 is a rear surface 2 B. The element formation surface 2 A and the rear surface 2 B have substantially the same dimensions and the same shapes and are parallel to each other. As the material of the substrate 2 , a semiconductor substrate such as a silicon substrate may be used, a glass substrate may be used or a resin film may be used.

The substrate 2 has, as the surfaces other than the element formation surface 2 A and the rear surface 2 B, a plurality of side surfaces (a side surface 2 C, a side surface 2 D, a side surface 2 E and a side surface 2 F). The side surfaces extend and intersect (specifically, are perpendicular to) the element formation surface 2 A and the rear surface 2 B, and connect the element formation surface 2 A and the rear surface 2 B. In the preferred embodiment, the four side surfaces of the substrate 2 are formed as the side surface 2 C, the side surface 2 D, the side surface 2 E, and the side surface 2 F sequentially clockwise from the side surface including one short side of the substrate 2 .

The first connection electrode 3 and the second connection electrode 4 are disposed at both end portions of the substrate 2 in the longitudinal direction on the element formation surface 2 A of the substrate 2 . The first connection electrode 3 and the second connection electrode 4 are exposed to the uppermost surface of the chip resistor 1 , and are formed so as to cover the corner portions of the substrate 2 on the front surface side and to cross the boundaries between the element formation surface 2 A and the side surfaces 2 C to 2 F from the element formation surface 2 A. Specifically, the first connection electrode 3 and the second connection electrode integrally cover, at each of the end portions of the substrate 2 , the three side surfaces in the element formation surface 2 A and the end portions. Hence, each of corner portions 11 where the side surfaces intersect each other at both end portions of the substrate 2 in the longitudinal direction is individually covered with the first connection electrode 3 or the second connection electrode 4 .

The first connection electrode 3 and the second connection electrode 4 are formed in the shape of a quadrangle in plan view when seen in a direction normal to the element formation surface 2 A. More specifically, the substrate 2 is formed in the shape of a rectangle having a short side along the longitudinal direction of the substrate 2 and a long side along the lateral direction of the substrate.

Furthermore, in the main surfaces 3 A and 4 A of the first connection electrode 3 and the second connection electrode 4 , external concave/convex structures 6 and 7 are formed, respectively. The main surfaces 3 A and 4 A are, when the chip resistor 1 is mounted on a mounting substrate (for example, a mounting substrate 54 , which will be described later), surfaces opposite the mounting substrate. In the preferred embodiment, the external concave/convex structures 6 and 7 are formed substantially over the entire region of the main surfaces 3 A and 4 A, and regions where they are not formed are only the peripheral portions of the first connection electrode 3 and the second connection electrode 4 .

The element region 5 is formed, in the element formation surface 2 A of the substrate 2 , between the first connection electrode 3 and the second connection electrode 4 . In the element region 5 , circuit elements are formed.

FIG. 2 is a schematic plan view of the chip resistor 1 of FIG. 1 . FIG. 2 mainly shows a positioning relationship between the first connection electrode 3 , the second connection electrode 4 and the circuit element (resistor portion 8 ) and the planar arrangement of the resistor portion 8 .

In the element region 5 of the chip resistor 1 , as an example of the circuit element of the first invention, the resistor portion 8 is formed. The resistor portion 8 is formed with a resistor network where a plurality of (unit) resistor bodies R having equal resistance values are disposed in a matrix on the element formation surface 2 A. The resistor body R is formed of TiN (titanium nitride), TiON (titanium oxide nitride), or TiSiON. The resistor portion 8 is, in the region on the substrate 2 , connected between the first connection electrode 3 and the second connection electrode 4 .

More specifically, the resistor portion 8 has a total of 352 resistor bodies R that are formed with 8 resistor bodies R arrayed along the row direction (the longitudinal direction of the substrate 2 ) and 44 resistor bodies R arrayed along the column direction (the width direction of the substrate 2 . These resistor bodies R are a plurality of element components that form the resistor network of the resistor portion 8 .

Among a large number of resistor bodies R described above, every predetermined number from 1 to 64 pieces, the resistor bodies R are connected collectively and electrically, and thus a plurality of types of resistor circuits are formed. The plurality of types of resistor circuits formed are connected with a conductor film D (wiring film formed with a conductor) into a predetermined aspect. Furthermore, on the element formation surface 2 A of the substrate 2 , a plurality of fuses F are provided which can be cut (blown) so that the resistor circuits are electrically incorporated into the resistor portion 8 or are electrically separated from the resistor portion 8 . The plurality of fuses F and the conductor films D are arrayed along the inner side of the first connection electrode 3 such that the positioning region is formed in the shape of a straight line. More specifically, the plurality of fuses F and the conductor films D are disposed so as to be adjacent, and the direction of the alignment is formed in the shape of a straight line. The plurality of fuses F are connected such that a plurality of types of resistor circuits (a plurality of resistor bodies R per resistor circuit) can be cut (separated) from the first connection electrode 3 .

FIG. 3 is a partially enlarged view of the resistor portion 8 of FIG. 2 . FIG. 4 is a cross-sectional view of the resistor portion 8 taken along line IV-IV in FIG. 3 . FIG. 5 is a cross-sectional view of the resistor portion 8 taken along line V-V in FIG. 3 .

The chip resistor 1 includes a first insulating film 9 , a resistor body film 10 , a first wiring film 12 , a second insulating film 13 , a passivation film 14 , and a resin film 15 formed on the element formation surface 2 A of the substrate 2 .

The first insulating film 9 is formed of, for example, an insulating material such as SiO 2 (silicon oxide). The thickness of the first insulating film 9 is, for example, 1.5 to 3.0 μm. The first insulating film 9 covers the entire region of the element formation surface 2 A of the substrate 2 . Although in the preferred embodiment, an example where the first insulating film 9 is formed with a single layer will be described, the insulating film may be formed with a plurality of layers.

The resistor body film 10 is formed on the first insulating film 9 . The resistor body film 10 is formed of TiN, TiON, or TiSiON. The thickness of the resistor body film 10 is, for example, about 2000 angstroms. The resistor body film 10 forms a plurality of resistor body films (hereinafter referred to as “resistor body film lines 10 A”) that extend parallel in a straight line between the first connection electrode 3 and the second connection electrode 4 . As shown in FIG. 3 , the resistor body film line 10 A may be cut at a predetermined position in a line direction.

On the resistor body film line 10 A, the first wiring film 12 is formed. The first wiring film 12 is formed of Al (aluminum) or an alloy (Al—Cu alloy) of Al and Cu (copper). The thickness of the first wiring film 12 is about 8000 angstroms. The first wiring films 12 are laminated at a fixed interval R in the line direction on the resistor body film line 10 A, and are in contact with the resistor body film line 10 A.

The second insulating film 13 is formed on the first insulating film 9 so as to cover the first wiring film 12 . The second insulating film 13 is formed of, for example, an insulating material such as SiN (silicon nitride). The thickness of the second insulating film 13 is, for example, 0.2 to 0.7 μm.

The passivation film 14 is formed on the second insulating film 13 . The passivation film 14 is formed of, for example, an insulating material such as SiN (silicon nitride). The thickness of the passivation film 14 is, for example, 0.7 to 1.6 μm.

The resin film 15 is formed on the passivation film 14 . The resin film 15 is formed of, for example, polyimide. The thickness of the resin film 15 is, for example, 3 to 10 μm.

FIG. 6A is a circuit diagram showing the electrical characteristics of the resistor body film line 10 A and the first wiring film 12 . FIG. 6B is a circuit diagram showing the electrical characteristics of the resistor body film line 10 A and the first wiring film 12 . FIG. 7 is a circuit diagram showing the electrical characteristics of the resistor body film line 10 A and the first wiring film 12 .

As shown in FIG. 6A , the region having the fixed interval R in the resistor body film line 10 A individually forms one resistor body R having a predetermined resistance value r. On the other hand, in the region where the first wiring film 12 is laminated in the resistor body film line 10 A, the first wiring film 12 electrically connects the resistor bodies R adjacent to each other, and thus the resistor body film line 10 A is short-circuited by the first wiring film 12 . Hence, the resistor circuit that is formed with the resistor bodies R of the resistance value r shown in FIG. 6B and connected in series is formed.

Since the adjacent resistor body film lines 10 A are connected with the resistor body film 10 and the first wiring film 12 , the resistor network of the resistor portions 8 shown in FIG. 3 forms the resistor circuit shown in FIG. 7 (formed with the unit resistors of the resistor bodies R described above). As described above, the resistor body film 10 and the first wiring film 12 form the resistor bodies R and the resistor circuit (that is, the resistor portion 8 ). The resistor bodies R include the resistor body film lines 10 A (resistor body films 10 ) and a plurality of first wiring films 12 that are laminated on the resistor body film line 10 A at the fixed interval R in the line direction, and a part of the resistor body film line 10 A in the fixed interval R where the first wiring film 12 is not laminated forms one resistor body R. The parts of the resistor body film line 10 A forming the resistor bodies R are all equal in shape and size. Hence, a large number of resistor bodies R arrayed in the matrix on the substrate 2 have equal resistance values.

The first wiring films 12 laminated on the resistor body film line 10 A form the resistor bodies R and also function as the conductor films D that connect a plurality of resistor bodies R to form the resistor circuit (see FIG. 2 ).

FIG. 8 is a partially enlarged view of the chip resistor 1 of FIG. 2 . FIG. 9 is a cross-sectional view of the chip resistor 1 taken along line IX-IX in FIG. 8 . It should be noted that FIG. 9 does not show the external concave/convex structure 6 of the first connection electrode 3 and the external concave/convex structure 7 of the second connection electrode 4 .

The fuse F and the conductor film D described above are also formed with the first wiring film 12 laminated on the resistor body film 10 forming the resistor bodies R. In other words, in the same layer as the first wiring film 12 laminated on the resistor body film line 10 A forming the resistor bodies R, the fuse F and the conductor film D are formed of Al, which is the same metal material as the first wiring film 12 , or an Al—Cu alloy. Since as described above, the first wiring film 12 forms the resistor circuit, the first wiring film 12 is also used as the conductor film D that electrically connects the plurality of resistor bodies R.

In other words, in the same layer laminated on the resistor body film 10 , the wiring film for forming the resistor bodies R, the fuses F, and the conductor films D are formed, as the first wiring film 12 , of the same metal material (Al or an Al—Cu alloy). The fuse F differs (is distinguished) from the first wiring film 12 in that the fuse F is formed to be thin so as to be easily cut and that other circuit elements are not disposed around the fuse F.

The region of the first wiring film 12 where the fuses F are disposed is referred to as a trimming region X (see FIGS. 2 and 8 ). The trimming region X is a region in the shape of a straight line along the inner side of the first connection electrode 3 , and in the trimming region X, not only the fuses F but also the conductor films D are disposed. The resistor body film 10 is also formed below the first wiring film 12 in the trimming region X (see FIG. 9 ). The fuse F is a wiring (separated from the surrounding) in which as compared with the parts of the first wiring film 12 other than the trimming region X, the wiring-to-wiring distance is large.

The fuses F may indicate not only the part of the first wiring film 12 but also a combination (fuse element) of the part of the resistor bodies R (the resistor body film 10 ) and the part of the first wiring film 12 .

Although only the case where the same layer as the conductor film D is used for the fuse F is described, another conductor film may be further laminated on the conductor film D to lower the resistance value of the entire conductor film D. Even in this case, the fusing property of the fuse F is not degraded as long as a conductor film is not laminated on the fuse F.

FIG. 10 is an example of a circuit diagram arranged with the resistor body film line 10 A and the first wiring film 12 .

In FIG. 10 , the resistor portion 8 is formed by connecting a reference resistor circuit R 8 , a resistor circuit R 64 , two resistor circuits R 32 , a resistor circuit R 16 , a resistor circuit R 8 , a resistor circuit R 4 , a resistor circuit R 2 , a resistor circuit R 1 , a resistor circuit R/ 2 , a resistor circuit R/ 4 , a resistor circuit R/ 8 , a resistor circuit R/ 16 , and a resistor circuit R/ 32 , in series, in this order. Each of the reference resistor circuit R 8 and the resistor circuits R 64 to R 2 is formed by connecting, in series, the same number of resistor bodies R as the number at the end of itself (in the case of R 64 , the number is “64”). The resistor circuit R 1 is formed with one resistor body R. Each of the resistor circuits R/ 2 to R/ 32 is formed by connecting, in parallel, the same number of resistor bodies R as the number at the end of itself (in the case of R/ 32 , the number is “32”). The meaning of the number at the end of the resistor circuit is the same as in FIGS. 11 and 12 , which will be described later.

One fuse F is provided for each of the resistor circuits R 64 to R/ 32 other than the reference resistor circuit R 8 , and those fuses F are connected in parallel to those resistor circuits. The fuses F are mutually connected in series either directly or through the conductor film D (see FIG. 8 ).

As shown in FIG. 10 , in a state where no fuses F are blown, the resistor portion 8 forms the resistor circuit of the reference resistor circuit R 8 formed with 8 resistor bodies R provided between the first connection electrode 3 and the second connection electrode 4 and connected in series. For example, when it is assumed that the resistance value r of one resistor body R is r=8Ω, the chip resistor 1 to which the first connection electrode 3 and the second connection electrode 4 are connected is formed by the resistor circuit (reference resistor circuit R 8 ) of 8r=64Ω.

In a state where no fuses F are blown, a plurality of types of resistor circuits other than the reference resistor circuit R 8 are short-circuited. Specifically, although the 13 resistor circuits R 64 to R/ 32 of 12 types are connected in series to the reference resistor circuit R 8 , since the resistor circuits are short-circuited by the fuses F connected in parallel, the resistor circuits are not incorporated into the resistor portion 8 in terms of electricity.

In the chip resistor 1 according to the preferred embodiment, the fuses F are selectively blown by, for example, laser light according to the required resistance value. In this way, the resistor circuits in which the fuses F connected in parallel are blown are incorporated into the resistor portion 8 . Hence, the entire resistance value of the resistor portion 8 can be set at a resistance value that is obtained by connecting in series and incorporating the resistor circuits corresponding to the blown fuses F.

In particular, a plurality of types of resistor circuits include a plurality of types of serial resistor circuits in which the resistor bodies R having equal resistance values are connected while the number of resistor bodies R is being increased geometrically with a geometric ratio of 2 such that 1 piece, 2 pieces, 4 pieces, 8 pieces, 16 pieces, 32 pieces . . . are connected in series and a plurality of types of parallel resistor circuits in which the resistor bodies R having equal resistance values are connected while the number of resistor bodies R is being increased geometrically with a geometric ratio of 2 such that 2 pieces, 4 pieces, 8 pieces, 16 pieces . . . are connected in parallel. Hence, the fuses F (including the fuse element described above) are selectively blown, and thus the resistance value of the entire resistor portion 8 is finely and digitally adjusted to be an arbitrary resistance value, with the result that the resistor portion of a desired value can be produced in the chip resistor 1 .

FIG. 11 is another example of the circuit diagram arranged with the resistor body film line 10 A and the first wiring film 12 .

Instead of forming the resistor portion 8 by connecting, in series, the reference resistor circuit R 8 and the resistor circuits R 64 to R/ 32 as shown in FIG. 10 , as shown in FIG. 11 , the resistor portion 8 may be formed. Specifically, between the first connection electrode 3 and the second connection electrode 4 , the resistor portion 8 may be formed with a serial connection circuit of a reference resistor circuit R/ 16 and a parallel connection circuit of 12 types of resistor circuits R/ 16 , R/ 8 , R/ 4 , R/ 2 , R 1 , R 2 , R 4 , R 8 , R 16 , R 32 , R 64 , and R 128 .

In this case, the fuse F is connected in series to each of the 12 types of resistor circuits other than the reference resistor circuit R/ 16 . In a state where no fuses F are blown, the resistor circuits are electrically incorporated into the resistor portion 8 . The fuses F are selectively blown by, for example, laser light according to the required resistance value, and thus the resistor circuits (the resistor circuits to which the fuses F are connected in series) corresponding to the blown fuses F are electrically separated from the resistor portion 8 , with the result that the resistance value of the entire chip resistor 1 can be adjusted.

FIG. 12 is yet another example of the circuit diagram arranged with the resistor body film line 10 A and the first wiring film 12 .

The feature of the resistor portion 8 shown in FIG. 12 is a circuit arrangement in which a serial connection of a plurality of types of resistor circuits and a parallel connection of a plurality of types of resistor circuits are connected in series. In the plurality of types of resistor circuits connected in series, as in the form described previously, the fuse F is connected in parallel to each of the resistor circuits, and all the types of the plurality of resistor circuits connected in series are short-circuited by the fuses F. Hence, when the fuse F is blown, the resistor circuit short-circuited by the blown fuse F is electrically incorporated into the resistor portion 8 .

On the other hand, the fuse F is connected in series to each of the plurality of types of resistor circuits connected in parallel. Hence, the fuse F is blown, and thus it is possible to electrically separate the resistor circuit to which the blown fuse F is connected in series from the parallel connection of the resistor circuits.

In the arrangement described above, for example, small resistors of 1 kΩ or less are produced on the side of the parallel connection, and the resistor circuits of 1 kΩ or more are produced on the side of the serial connection, and thus the resistor circuits in a wide range from small resistors of a few ohms to large resistors of a few mega ohms can be produced with a resistor network formed with the same basic design. That is, in the chip resistor 1 , one or a plurality of fuses F are selectively cut, and thus it is possible to easily and quickly cope with a plurality of types of resistor values. In other words, a plurality of resistor bodies R having different resistance values are combined, and thus it is possible to realize the chip resistors 1 of various resistance values with the common design.

As described above, in the chip resistor 1 , the state of the connection of a plurality of resistor bodies R (resistor circuit) can be changed in the trimming region X.

The cross-sectional structure (in particular, the structure of an electrode region 16 ) of the chip resistor 1 will then be described in further detail with reference to FIGS. 13 and 14 .

FIG. 13 is a schematic cross-sectional view of the chip resistor 1 of FIG. 1 . FIG. 14 is a partially enlarged view of the chip resistor 1 of FIG. 13 . FIG. 13 fragmentally shows the cross-sectional structure of the characteristic part of the chip resistor 1 , and it should be noted that FIG. 13 does not show a cross section taken along a specific line of the chip resistor 1 .

In the chip resistor 1 , in the electrode region 16 immediately below the first connection electrode 3 and the second connection electrode 4 , a plurality of concave portions 17 are formed that pass through the second insulating film 13 and that extend halfway along the direction of thickness of the first insulating film 9 . In other words, one concave portion 17 is defined by continuously forming the concave portion of the first insulating film 9 and the through hole of the second insulating film 13 . In the preferred embodiment, the plurality of concave portions 17 are arranged in a matrix in plan view when seen in a direction normal to the element formation surface 2 A. In this way, in each electrode region 16 , an internal concave/convex structure 18 formed by the aggregation of a plurality of concave portions 17 is formed. Each of the concave portions 17 is formed in the shape of a square having a planar size of 4 μm×4 μm, and is disposed at an interval of 4 μm from the adjacent concave portion 17 . The depth of each of the concave portions 17 is, for example, 0.5 to 1.5 μm (preferably, about 0.8 μm). The concave portion 17 does not need to be formed in the shape of a square, and may be formed in the shape of, for example, a rectangle, a triangle, a circle, an ellipse, a polygon or the like.

On the second insulating film 13 , a second wiring film 19 is formed. The second wiring film 19 is formed of Al (aluminum) or an alloy (Al—Cu alloy) of Al and Cu (copper). The thickness of the second wiring film 19 is about 8000 angstroms. In the preferred embodiment, the second wiring film 19 includes a resistor wiring film 20 that electrically connects the first connection electrode 3 and the resistor body films 10 and that electrically connects the second connection electrode 4 and the resistor body films 10 .

The resistor wiring film 20 is formed so as to extend from the element region 5 through the boundary between the element region 5 and the electrode region 16 to the electrode region 16 .

In the element region 5 , the resistor wiring film 20 is connected as a via through a through hole 21 formed in the second insulating film 13 to the first wiring film 12 . By the connection, an electrical connection between the resistor wiring film 20 and the resistor body film 10 is achieved.

On the other hand, in the electrode region 16 , the resistor wiring film 20 is extended into the concave portion 17 of the internal concave/convex structure 18 . More specifically, as shown in FIG. 14 , the resistor wiring film 20 integrally includes an embedding portion 22 that is completely embedded in the concave portion 17 (that is, that completely fills the concave portion 17 ) and a surface layer portion 23 that covers the internal concave/convex structure 18 along the surface of the second insulating film 13 . In other words, the resistor wiring film 20 includes, as parts of the first connection electrode 3 and the second connection electrode 4 , an anchor portion 24 that is embedded in the direction of thickness of an insulating film (in the preferred embodiment, the first insulating film 9 and the second insulating film 13 ) and that is fixed.

In the surface of the anchor portion 24 , an intermediate concave/convex structure 26 formed with a plurality of concave portions 25 is formed. The concave portions 25 are disposed in positions opposite the concave portions 17 of the internal concave/convex structure 18 in a one-to-one manner. In other words, the plurality of concave portions 25 are also disposed in a matrix in plan view, and are disposed immediately above the concave portions 17 . In the preferred embodiment, the plurality of concave portions 25 are formed in the surface portion of the surface layer portion 23 of the anchor portion 24 , and its bottom portion is located in a position higher than the surface of the second insulating film 13 .

The passivation film 14 and the resin film 15 are formed on the second wiring film 19 . The passivation film 14 selectively covers the part on the element region 5 of the second wiring film 19 . In the electrode region 16 , the second wiring film 19 (the anchor portion 24 ) is exposed.

As with the passivation film 14 , the resin film 15 is selectively formed on the element region 5 such that the anchor portion 24 is exposed. The end surface of the resin film 15 and the end surface of the passivation film 14 form an end surface 27 that is continuously flat. The anchor portion 24 is exposed to a region between the end surface 27 , and the side surfaces 2 C and 2 E of the substrate 2 in a state where the anchor portion 24 is drawn from the passivation film 14 and the resin film 15 . The anchor portion 24 is disposed in a position displaced inwardly of the substrate 2 with respect to the side surfaces 2 C to 2 F of the substrate 2 , and a constant clearance 36 (for example, 3 to 6 μm) is provided between the end surface of the anchor portion 24 and the side surfaces 2 C to 2 F.

Furthermore, the chip resistor 1 includes a passivation film 28 that is formed on the end surface 27 of the resin film 15 and the side surfaces 2 C to 2 F of the substrate 2 . The passivation film 28 is formed of, for example, an insulating material such as SiN (silicon nitride). The thickness of the passivation film 28 is, for example, 0.2 to 1.5 μm.

Each of the first connection electrode 3 and the second connection electrode 4 includes not only the anchor portion 24 but also an external connection portion 29 . The external connection portion 29 is formed so as to cover the end portion of the resin film 15 and the side surfaces 2 C to 2 F of the substrate 2 . In the side surfaces 2 C to 2 F, the passivation film 28 prevents the external connection portion 29 and the substrate 2 from being short-circuited.

The external connection portion 29 includes a Ni layer 30 , a Pd layer 31 , and an Au layer 32 from the side of the substrate 2 in this order. The external connection portion 29 includes a laminated structure formed with the Ni layer 30 , the Pd layer 31 , and the Au layer 32 not only in a region on the element formation surface 2 A but also in a region on the side surfaces 2 C to 2 F. In the external connection portion 29 , the Ni layer 30 covers a large proportion thereof, and the Pd layer 31 and the Au layer 32 are formed so as to be much thinner than the Ni layer 30 .

As described above, since in the external connection portion 29 , the surface of the Ni layer 30 is covered by the Au layer 32 , the Ni layer 30 can be prevented from being oxidized. Even if the Au layer 32 is thinned, and thus a through hole (pin hole) is formed in the Au layer 32 , since the Pd layer 31 inserted between the Ni layer 30 and the Au layer 32 blocks the through hole, it is possible to prevent the Ni layer 30 from being exposed through the through hole to the outside and oxidized.

In the surface of the external connection portion 29 , external concave/convex structures 6 and 7 formed with a plurality of concave portions 33 are formed. The concave portions 33 are disposed in positions opposite the concave portions 17 of the internal concave/convex structure 18 in a one-to-one manner. In other words, the plurality of concave portions 33 are also arrayed in a matrix in plan view, and are disposed immediately above the concave portions 17 . When as in the preferred embodiment, the electrode (the external connection portion 29 ) is formed with a plurality of metal layers, the plurality of concave portions 33 are not selectively formed only on the metal layer (in the preferred embodiment, the Au layer 32 ) of the uppermost surface. The concave portions 33 are formed by stacking, in a plurality of stages, the concave portions of substantially the same shape from the surface of the metal layer (in the preferred embodiment, the Ni layer 30 ) of the lowermost layer.

In the external connection portion 29 , between the external concave/convex structures 6 and 7 , and the peripheral edge of the external connection portion 29 (the peripheral edge of the electrode), a constant clearance 35 is provided (see FIG. 14 ). As described later, the external concave/convex structures 6 and 7 are not formed in such a concave/convex shape by etching processing on the uppermost surface, but is formed in a concave/concave shape by using the shapes of the internal concave/convex structure 18 and the intermediate concave/convex structure 26 previously formed (see FIG. 15L ). The anchor portion 24 having the intermediate concave/convex structure 26 has a clearance 36 between itself and the side surfaces 2 C to 2 F of the substrate 2 in terms of preventing contact with the substrate 2 . Hence, in the external connection portion 29 , the clearance 35 (peripheral portion) whose surface is flat is formed in a region on the clearance 36 where at least a concave/convex shape is not formed. Since the concave portions are decreased in size as the concave/convex shape is received from the internal concave/convex structure 18 , the amount of recess of the concave portions 33 in the external concave/convex structures 6 and 7 is less than the amount of recess of the internal concave/convex structure 18 .

FIGS. 15A to 15M are diagrams showing part of a manufacturing step of the chip resistor 1 of FIG. 13 .

As shown in FIG. 15A , a substrate 37 that is an original of the substrate 2 is first prepared. In this case, the surface 37 A of the substrate 37 is the element formation surface 2 A of the substrate 2 , and the rear surface 37 B of the substrate 37 is the rear surface 2 B of the substrate 2 . Then, the surface 37 A of the substrate 37 is thermally oxidized, and thus the first insulating film 9 formed of SiO 2 and the like is formed on the surface 37 A.

Then, as shown in FIG. 15B , on the first insulating film 9 , the resistor portion 8 (the resistor bodies R and the first wiring films 12 connected to the resistor bodies R) is formed. Specifically, by sputtering, on the first insulating film 9 , the resistor body film 10 of TiN, TiON, or TiSiON is first formed on the entire surface, and furthermore, on the resistor body film 10 , the first wiring film 12 of aluminum (Al) is laminated so as to make contact with the resistor body film 10 . Thereafter, a photolithography process is used, and for example, by dry etching such as RIE (Reactive Ion Etching), the resistor body film 10 and the first wiring film 12 are selectively removed to perform patterning. Here, the resistor body film 10 and the first wiring film 12 on the electrode region 16 are completely removed. In this way, it is possible to obtain the following arrangement: as shown in FIG. 3 , in plan view, the resistor body film lines 10 A in which the resistor body film 10 is laminated and which has a constant width are arrayed at a fixed interval in the column direction.

Here, a region where the resistor body film line 10 A and the first wiring film 12 are partially cut is also formed, and in the trimming region X described previously, the fuses F and the conductor films D are formed (see FIG. 2 ). Then, for example, by wet etching, the first wiring film 12 laminated on the resistor body film line 10 A is selectively removed. Consequently, it is possible to obtain the resistor portion 8 in which on the resistor body film line 10 A, the first wiring films 12 are laminated at a fixed interval R. Here, the resistance value of the entire resistor portion 8 may be measured so that whether or not the resistor body film 10 and the first wiring film 12 are formed to have target dimensions is checked.

Then, as shown in FIG. 15C , by a CVD (Chemical Vapor Deposition) method, the second insulating film 13 formed of SiN is formed over the entire region of the surface 37 A of the substrate 37 . The second insulating film 13 covers all of the first insulating film 9 and the resistor portion 8 (the resistor body film 10 and the first wiring film 12 ) on the first insulating film 9 , and is in contact with them. Hence, the second insulating film 13 also covers the first wiring film 12 in the trimming region X (see FIG. 2 ) described previously.

Then, as shown in FIG. 15D , a photolithography process is used, and for example, by dry etching such as RIE (Reactive Ion Etching), the second insulating film 13 is selectively removed to perform patterning. In this way, through holes 38 are formed in the electrode region 16 , and simultaneously, the through holes 21 are formed in the element region 5 .

Then, as shown in FIG. 15E , an etching gas for SiO 2 is supplied, and thus the first insulating film 9 below the through holes 38 is selectively removed (cut away). In this way, it is possible to obtain the internal concave/convex structure 18 formed with a plurality of concave portions 17 .

Then, as shown in FIG. 15F , the resistor wiring film 20 (the anchor portion 24 ) is formed on the second insulating film 13 . Specifically, by sputtering, on the second insulating film 13 , the second wiring film 19 of aluminum (Al) is first laminated, and thereafter a photolithography process is used, and for example, by dry etching such as RIE (Reactive Ion Etching), the second wiring film 19 is selectively removed to perform patterning. In this way, it is possible to obtain the resistor wiring film 20 (the anchor portion 24 ). Here, on the surface of the anchor portion 24 on the internal concave/convex structure 18 , the intermediate concave/convex structure 26 formed with a plurality of concave portions 25 are formed by continuation of the concave/convex shape of the internal concave/convex structure 18 (the concave/convex shape where the positions opposite the concave portions 17 are recessed). In order for the embedding portion 22 and the surface layer portion 23 (see FIG. 14 ) to be formed, the second wiring film 19 is preferably formed to have a relatively large thickness such that the concave portions 17 are completely refilled in aluminum.

Then, as shown in FIG. 15G , by a CVD (Chemical Vapor Deposition) method, the passivation film 14 formed of SiN is formed over the entire region of the surface 37 A of the substrate 37 . Then, a liquid of a light-sensitive resin formed of polyimide is sprayed on the substrate 37 from above the passivation film 14 to form the resin film 15 of the light-sensitive resin. The surface of the resin film 15 on the surface 37 A is flat along the surface 37 A. Then, heat treatment (curing) is performed on the resin film 15 . In this way, the thickness of the resin film 15 is thermally contracted, and the resin film 15 is cured, with the result that the film quality is stabilized. Then, the resin film 15 and the passivation film 14 are patterned, and thus parts on the electrode region 16 of these films 14 and 15 are selectively removed, and the end surface 27 of the resin film 15 is formed.

Then, as shown in FIG. 15H , the probes 39 of a resistance measuring apparatus (not shown) are brought into contact with the anchor portion 24 to detect the resistance value of the entire resistor portion 8 . Then, laser light (not shown) is applied to an arbitrary fuse F (see FIG. 2 ) beyond the second insulating film 13 , and thus the first wiring film 12 in the trimming region X described previously is trimmed with the laser light, with the result that the fuse F is blown. In this way, the fuse F is blown (trimmed) such that the necessary resistance value is obtained, and thus the resistance value of the entire semi-finished product 40 (in other words, the chip resistor 1 ) can be adjusted as described above.

Here, the second insulating film 13 serves as a cover film that covers the resistor portion 8 , and thus it is possible to prevent a short circuit by the adherence of the resistor portion 8 with broken pieces or the like produced by the blowing. Moreover, since the second insulating film 13 covers the fuse F (the resistor body film 10 ), the energy of the laser light is stored in the fuse F, and thus the fuse F can be reliably blown.

Then, as shown in FIG. 15I , a resist pattern 41 is formed over the entire region of the surface 37 A of the substrate 37 . In the resist pattern 41 , an opening 42 is formed.

FIG. 16 is a schematic plan view of the resist pattern 41 used to form a groove 44 in the step of FIG. 15I .

With reference to FIG. 16 , when a large number of chip resistors 1 (chip part region Y) are disposed in a matrix, in plan view, the opening 42 of the resist pattern 41 coincides with a region (a hatched part of FIG. 16 ) between the outlines of adjacent chip resistors 1 . Hence, the overall shape of the opening 42 is the shape of a lattice that has a plurality of rectilinear portions 42 A and rectilinear portions 42 B perpendicular to each other.

In the resist pattern 41 , the rectilinear portions 42 A and the rectilinear portions 42 B perpendicular to each other in the opening 42 are connected while the state where they are perpendicular to each other is being maintained (without being curved). Hence, an intersection portion 43 between the rectilinear portion 42 A and the rectilinear portion 42 B is pointed so as to form an angle of about 90° in plan view.

With reference to FIG. 15I , by plasma etching using the resist pattern 41 as a mask, the substrate 37 is selectively removed. In this way, the material of the substrate 37 is removed in a position a distance apart from the second wiring film 19 in the boundary region between the adjacent resistor portions 8 . Consequently, in plan view, in the position coinciding with the opening 42 of the resist pattern 41 , the groove 44 that has a predetermined depth extending from the surface 37 A of the substrate 37 halfway through the thickness of the substrate 37 is formed. In the preferred embodiment, in the substrate 37 having a thickness of about 725 μm, the depth of the groove 44 is about 100 μm, the width of the groove 44 is about 20 μm and is constant over the entire region in the direction of the depth.

In plan view, the overall shape of the groove 44 in the substrate 37 is formed in the shape of a lattice coinciding with the opening 42 of the resist pattern 41 . Each of the semi-finished products 40 is located in the chip part region Y surrounded by the groove 44 , and these semi-finished products 40 are disposed orderly in a matrix. The groove 44 is formed as described above, and thus the substrate 37 is separated into the substrates 2 for a plurality of chip part regions Y. After the formation of the groove 44 , the resist pattern 41 is removed.

Then, as shown in FIG. 15J , by a CVD method, the passivation film 28 formed of SiN is formed over the entire region of the surface 37 A of the substrate 37 . Here, the passivation film 28 is also formed over the entire region of the inner peripheral surface of the groove 44 .

Then, as shown in FIG. 15K , the passivation film 28 is selectively etched. Specifically, the part of the passivation film 28 parallel to the surface 37 A is selectively etched. In this way, the part of the passivation film 28 on the electrode region 16 is selectively removed, and thus the anchor portion 24 is exposed.

Then, by electroless plating, Ni, Pd, and Au are sequentially grown from the anchor portion 24 by plating. The plating is continued until each plating film is grown in the lateral direction along the surface 37 A to cover the passivation film 28 on the side surface of the groove 44 . In this way, as shown in FIG. 15L , the external connection portion 29 formed with a Ni/Pd/Au laminated film is formed.

FIG. 17 is a diagram for illustrating the manufacturing step of the external connection portion 29 .

Specifically, with reference to FIG. 17 , the surface of the anchor portion 24 is first purified, and thus organic substances (including smut such as a stain of carbon and greasy dirt) are removed (degreased) (step S 1 ). Then, the oxide film on the surface is removed (step S 2 ). Then, zincate treatment is performed on the surface, and thus Al on the surface (of the second wiring film 19 ) is replaced by Zn (step S 3 ). Then, Zn on the surface is peeled off with nitric acid etc., and in the anchor portion 24 , new Al is exposed (step S 4 ).

Then, the anchor portion 24 is immersed in a plating solution, and thus Ni plating is performed on the surface of the new Al in the anchor portion 24 . In this way, Ni in the plating solution is chemically reduced and deposited, and thus the Ni layer 30 is formed on the surface (step S 5 ).

Then, the Ni layer 30 is immersed in another plating solution, and thus Pd plating is performed on the surface of the Ni layer 30 . In this way, Pd in the plating solution is chemically reduced and deposited, and thus the Pd layer 31 is formed on the surface of the Ni layer 30 (step S 6 ).

Then, the Pd layer 31 is immersed in another plating solution, and thus Au plating is performed on the surface of the Pd layer 31 . In this way, Au in the plating solution is chemically reduced and deposited, and thus the Au layer 32 is formed on the surface of the Pd layer 31 (step S 7 ). In this way, the first connection electrode 3 and the second connection electrode 4 are formed, and when the formed first connection electrode 3 and the formed second connection electrode 4 are dried (step S 8 ), the manufacturing step of the first connection electrode 3 and the second connection electrode 4 is completed. Between the successive steps, a step of washing the semi-finished product 40 with water is performed as necessary. The zincate treatment may be performed at a plurality of times.

FIG. 15L shows a state where in each semi-finished product 40 , the first connection electrode 3 and the second connection electrode 4 have already been formed.

As described above, the first connection electrode 3 and the second connection electrode 4 (the external connection portion 29 ) are formed on the anchor portion 24 having the intermediate concave/convex structure 26 . Hence, in the main surfaces 3 A and 4 A of the first connection electrode 3 and the second connection electrode 4 , the external concave/convex structures 6 and 7 formed with a plurality of concave portions 33 are formed by continuation of the concave/convex shape (the concave/convex shape where the positions opposite the concave portions 25 are recessed) of the intermediate concave/convex structure 26 .

Since the first connection electrode 3 and the second connection electrode 4 (the external connection portion 29 ) are formed by electroless plating, Ni, Pd, and Al serving as electrode materials can be satisfactorily grown on the passivation film 28 by plating. As compared with a case where the first connection electrode 3 and the second connection electrode 4 are formed by electrolytic plating, the number of steps (for example, a lithography step and a resist mask peeling step necessary in electrolytic plating) in the step of forming the first connection electrode 3 and the second connection electrode 4 is reduced, with the result that it is possible to enhance the productivity of the chip resistor 1 . Furthermore, since in electroless plating, the resist mask necessary in electrolytic plating is not needed, the position of the formation of the first connection electrode 3 and the second connection electrode 4 is prevented from being displaced by the displacement of the position of the resist mask, and thus the formation position accuracy of the first connection electrode 3 and the second connection electrode 4 is enhanced, with the result that it is possible to enhance the yield.

In this method, the anchor portion 24 is exposed from the end surface 27 of the resin film 15 , and there is no obstruction of the plating growth in a region from the anchor portion 24 to the groove 44 . In other words, since the resistor portion 8 is covered by the resin film 15 , the region where the resistor portion 8 is formed is not grown by plating. Hence, it is possible to perform plating growth rectilinearly from the anchor portion 24 to the groove 44 . Consequently, it is possible to reduce the time necessary to form the electrode.

The first connection electrode 3 and the second connection electrode 4 are formed as described above, and then a conduction test is performed between the first connection electrode 3 and the second connection electrode 4 . In the conduction test between the first connection electrode 3 and the second connection electrode 4 , for example, by the same method as described previously with reference to FIG. 15 , the probes 45 of the resistance measuring apparatus (not shown) are brought into contact with the first connection electrode 3 and the second connection electrode 4 , and the resistance value of the entire resistor portion 8 is detected. Then, after the conduction test is performed between the first connection electrode 3 and the second connection electrode 4 , the substrate 37 is ground from the rear surface 37 B.

Specifically, after the formation of the groove 44 , as shown in FIG. 15M , a supporting tape 47 that is formed of PET (polyethylene terephthalate), that is formed in the shape of a thin plate and that has an adhesive surface 46 is adhered, in the adhesive surface 46 , to the side (that is, the surface 37 A) of the first connection electrode 3 and the second connection electrode 4 . In this way, each semi-finished product 40 is supported by the supporting tape 47 . Here, as the supporting tape 47 , for example, a laminated tape can be used.

With each semi-finished product 40 supported by the supporting tape 47 , the substrate 37 is grounded from the side of the rear surface 37 B. When by the grinding, the substrate 37 is thinned so as to reach the bottom surface of the groove 44 , since there is nothing that couples the adjacent semi-finished products 40 , the substrate 37 is separated with the groove 44 being a boundary and the semi-finished products 40 are individually separated, with the result that the finished product of the chip resistor 1 is formed. In other words, the substrate 37 is cut in the groove 44 , and thus the chip resistors 1 are individually cut out. By etching the substrate 37 from the side of the rear surface 37 B to the bottom surface of the groove 44 , the chip resistors 1 may be cut out.

As described above, the groove 44 is formed, and then the substrate 37 is ground from the side of the rear surface 37 B, and thus it is possible to separate, all at once, a plurality of chip part regions Y formed in the substrate 37 into individual chip resistors 1 (it is possible to obtain pieces of the chip resistors 1 at a time). Hence, by reducing the time necessary to manufacture the chip resistors 1 , it is possible to enhance the productivity of the chip resistor 1 .

By polishing or etching the rear surface 2 B of the substrate 2 in the finished chip resistor 1 into a mirror surface, the rear surface 2 B may be cleaned.

The recovery step of the chip resistor 1 will be described in detail below with reference to FIGS. 18A to 18D .

FIGS. 18A to 18D are diagrams for illustrating the recovery step of the chip resistor 1 after the step of FIG. 15M .

FIG. 18A shows a state where a plurality of chip resistors 1 separated into pieces still stick to the supporting tape 47 . In this state, as shown in FIG. 18B , a thermally foaming sheet 48 is adhered to the rear surface 2 B of the substrate 2 of each chip resistor 1 . The thermally foaming sheet 48 includes a sheet main body 49 in the shape of a sheet and a large number of foaming particles 50 kneaded into the sheet main body 49 .

The adhesive force of the sheet main body 49 is greater than that of the adhesive surface 46 of the supporting tape 47 . Hence, after the thermally foaming sheet 48 is adhered to the rear surface 2 B of the substrate 2 of each chip resistor 1 , as shown in FIG. 18C , the supporting tape 47 is peeled off from each chip resistor 1 , and the chip resistor 1 is transferred onto the thermally foaming sheet 48 . Here, since the adhesive property of the adhesive surface 46 is lowered by the application of ultraviolet rays to the supporting tape 47 (see dotted arrows in FIG. 18B ), the supporting tape 47 is easily peeled off from each chip resistor 1 .

Then, the thermally foaming sheet 48 is heated. In this way, as shown in FIG. 18D , in the thermally foaming sheet 48 , the foaming particles 50 within the sheet main body 49 are foamed and are expanded out of the surface of the sheet main body 49 . Consequently, the contact area between the thermally foaming sheet 48 and the rear surface 2 B of the substrate 2 of each chip resistor 1 is decreased, and thus all the chip resistors 1 are naturally peeled off from the thermally foaming sheet 48 (falling off). The chip resistors 1 recovered in this way are stored in a storage space formed by an embossed carrier tape (not shown). In this case, as compared with a case where the chip resistors 1 are peeled off from the supporting tape 47 or the thermally foaming sheet 48 one by one, it is possible to reduce the processing time. As a matter of course, with a plurality of chip resistors 1 sticking to the supporting tape 47 (see FIG. 18A ), without use of the thermally foaming sheet 48 , the chip resistors 1 may be directly peeled off from the supporting tape 47 by a predetermined number of pieces. Thereafter, the embossed carrier tape storing the chip resistors 1 stored in an automatic mounting machine 60 , is sucked by a suction nozzle 61 included in the automatic mounting machine 60 and is individually recovered (see FIGS. 20 and 21 ). On the chip resistor 1 recovered in this way, a front/rear judgement step using a part recognizing camera 62 is performed.

The recovery step of each chip resistor 1 can be performed with another method shown in FIGS. 19A to 19C .

FIGS. 19A to 19C are diagrams showing the recovery step (modification example) of the chip resistor 1 after the step of FIG. 15M .

As with FIG. 18A , FIG. 19A shows a state where a plurality of chip resistors 1 separated into pieces still stick to the supporting tape 47 . In this state, as shown in FIG. 19B , a transfer tape 51 is adhered to the rear surface 2 B of the substrate 2 of each chip resistor 1 . The transfer tape 51 has an adhesive force greater than that of the adhesive surface 46 of the supporting tape 47 . Hence, as shown in FIG. 19C , after the transfer tape 51 is adhered to each chip resistor 1 , the supporting tape 47 is peeled off from each chip resistor 1 . Here, as described previously, ultraviolet rays (see dotted arrows in FIG. 19B ) may be applied to the supporting tape 47 so that the adhesive property of the adhesive surface 46 is lowered.

Frames 63 installed in the automatic mounting machine 60 are adhered to both ends of the transfer tape 51 . The frames 63 on both sides can be moved either in a direction in which they approach each other or in a direction in which they are separated. After the supporting tape 47 is peeled off from each chip resistor 1 , the frames 63 on both sides are moved in the direction in which they are separated, and thus the transfer tape 51 is extended so as to become thin. In this way, the adhesive force of the transfer tape 51 is lowered, and thus each chip resistor 1 is easily peeled off from the transfer tape 51 . When in this state, the suction nozzle 61 of the automatic mounting machine 60 is directed to the side of the element formation surface 2 A of the chip resistor 1 , the chip resistor 1 is peeled off from the transfer tape 51 by the adhesive force produced by the automatic mounting machine 60 (the suction nozzle 61 ) and is sucked by the suction nozzle 61 . Here, the chip resistor 1 is pushed up by a projection 52 shown in FIG. 19C from the side opposite to the suction nozzle 61 through the transfer tape 51 to the side of the suction nozzle 61 , and thus the chip resistor 1 can be smoothly peeled off from the transfer tape 51 . On the chip resistor 1 recovered in this way, the front/rear judgement step using the part recognizing camera 62 is performed.

FIG. 20 is a diagram for illustrating the front/rear judgement step of the chip resistor 1 according to the first invention. FIG. 21 is a diagram for illustrating the front/rear judgement step of a chip resistor 53 according to a reference example.

FIGS. 20 and 21 respectively show a state where the chip resistor 1 of the first invention is sucked by the suction nozzle 61 and a state where the chip resistor 53 according to the reference example is sucked by the suction nozzle 61 . Here, the chip resistor 53 according to the reference example refers to a chip part in which the external concave/convex structures 6 and 7 are not formed in the surfaces of the first connection electrode 3 and the second connection electrode 4 .

As shown in FIG. 20 , while the chip resistor 1 is being sucked by the suction nozzle 61 , the chip resistor 1 is conveyed by the automatic mounting machine 60 to a part detection position P where the front and rear of the chip resistor 1 are determined by the part recognizing camera 62 . Here, the suction nozzle 61 sucks an approximate center part of the rear surface 2 B in the longitudinal direction. Since as described previously, the first connection electrode 3 and the second connection electrode 4 are provided only on the side of the element formation surface 2 A of the chip resistor 1 , in the chip resistor 1 , the rear surface 2 B is a flat surface without the electrodes (recesses and projections). Hence, when the suction nozzle 61 is moved while sucked to the chip resistor 1 , the suction nozzle 61 can be sucked to the flat rear surface 2 B. In other words, with the flat rear surface 2 B, it is possible to increase a margin of the part which can be sucked by the suction nozzle 61 . In this way, the suction nozzle 61 is reliably sucked to the chip resistor 1 , and the chip resistor 1 can be reliably transported to the part detection position P by the part recognizing camera 62 and onto the mounting substrate 54 without falling off from the suction nozzle 61 halfway through.

As shown in FIG. 20 , when the chip resistor 1 reaches the part detection position P, a light source 64 (for example, a light application machine including a plurality of LEDs) installed around the part recognizing camera 62 applies light to the element formation surface 2 A of the chip resistor 1 in an oblique direction. The part recognizing camera 62 detects the reflection light reflected by the element formation surface 2 A, thereby distinguishes between light and dark of a region where the first connection electrode 3 and the second connection electrode 4 are formed from a region where they are not formed and determines the front and rear of the chip resistor 1 .

The chip resistor 1 is not always sucked by the suction nozzle 61 in a horizontal position, and may be sucked by the suction nozzle 61 in an oblique position.

Here, as shown in FIG. 21 , in the chip resistor 53 according to the reference example, when in an oblique position, light is applied from the light source 64 to the element formation surface 2 A (see incident light λ 3 in FIG. 21 ), the light is reflected off (total reflection: see incident light λ 4 in FIG. 21 ) the first connection electrode 3 and the second connection electrode 4 toward the outside of the region where the part recognizing camera 62 is disposed, with the result that the light may not be detected by the part recognizing camera 62 . In this case, according to the image information by the part recognizing camera 62 , part or the whole of the first connection electrode 3 and the second connection electrode 4 in the chip resistor 53 appears dark. Hence, the automatic mounting machine 60 erroneously recognizes the region where the first connection electrode 3 and the second connection electrode 4 are formed as the region where they are not formed to stop the conveyance of the chip resistor 53 to the mounting substrate 54 . Hence, in the chip resistor 53 according to the reference example, the occurrence of such erroneous recognition prevents the chip part from being smoothly mounted.

By contrast, in the chip resistor 1 of the first invention, as shown in FIG. 20 , in the main surfaces 3 A and 4 A of the first connection electrode 3 and the second connection electrode 4 formed on the uppermost surface of the chip resistor 1 , the external concave/convex structures 6 and 7 are respectively formed. Hence, even when the chip resistor 1 is sucked in an oblique position, light (see incident light λ 1 in FIG. 20 ) applied from the light source 64 to the element formation surface 2 A is diffusely reflected by the external concave/convex structures 6 and 7 (see incident light λ 2 in FIG. 20 ). Hence, even when the chip resistor 1 is sucked in an oblique position as shown in FIG. 21 , the incident light λ 1 from the light source 64 can be reflected in all directions. Hence, even when the part recognizing camera 62 is disposed with respect to the part detection position P, the first connection electrode 3 and the second connection electrode 4 (the chip resistor 1 ) can be satisfactorily detected with the part recognizing camera 62 . Since in this way, the automatic mounting machine 60 can reduce the erroneous recognition (enhance an electrode recognition rate) due to the specifications of the chip resistor 1 , the chip resistor 1 can be stably mounted on the mounting substrate 54 .

Moreover, since it suffices to perform the processing in which the external concave/convex structures 6 and 7 are formed in the first connection electrode 3 and the second connection electrode 4 of the chip resistor 1 , it can be applied to chip parts of different specifications. Hence, it is not necessary to change the conditions (specifications) of the light source 64 disposed around the part recognizing camera 62 depending on the specifications of the chip part.

In the chip resistor 1 , since the bonding area of the first connection electrode 3 , and the second connection electrode 4 and the insulating films (the first insulating film 9 and the second insulating film 13 ) is increased by the anchor portion 24 , it is possible to enhance the adhesion strength of the electrode to the substrate 2 (insulating film). For example, the present inventors have verified that as compared with a conventional chip resistor which had no anchor portion 24 , the shear strength was enhanced by about 15%. In particular, in the preferred embodiment, as shown in FIG. 14 , the concave portions 17 of the internal concave/convex structure 18 are filled with the embedding portion 22 , and the interface (for example, the interface between the anchor portion 24 and the external connection portion 29 ) between different types of metals are not present in the concave portions 17 . In other words, since the interface between different types of metals in which its bonding force is lower than metal bonding in a metal crystal is not present, it is possible to enhance the strength of the anchor portion 24 itself within the concave portion 17 .

The anchor portion 24 is formed with a wiring film (in the preferred embodiment, the second wiring film 19 ) that is normally used in a chip part, and can be formed in the same step as in the wiring film. Hence, it is possible to prevent the number of steps from being increased due to the formation of the anchor portion 24 .

The chip resistor 1 that undergoes the steps described above is thereafter mounted on the mounting substrate 54 shown in FIGS. 22 and 23 .

FIG. 22 is a diagram showing a circuit assembly 55 in a state where the chip resistor 1 is mounted on the mounting substrate 54 . FIG. 23 is a diagram of the chip resistor 1 mounted on the mounting substrate 54 when seen from the side of the element formation surface 2 A.

As shown in FIG. 22 , the chip resistor 1 is mounted on the mounting substrate 54 . The chip resistor 1 and the mounting substrate 54 in this state form the circuit assembly 55 . The upper surface of the mounting substrate 54 in FIG. 22 is a mounting surface 54 A. In the mounting surface 54 A, a pair (two) of lands 56 that are connected to the internal circuit (not shown) of the mounting substrate 54 are formed. Each land 56 is formed of, for example, Cu. On the surface of each land 56 , a solder 57 is provided so as to protrude from the surface.

After the front/rear judgement step, the automatic mounting machine 60 moves the suction nozzle 61 to the mounting substrate 54 while sucking the chip resistor 1 . Here, the element formation surface 2 A of the chip resistor 1 and the mounting surface 54 A of the mounting substrate 54 are opposite each other. In this state, the suction nozzle 61 is moved to be pressed onto the mounting substrate 54 , in the chip resistor 1 , the first connection electrode 3 is brought into contact with the solder 57 on one of the lands 56 and the second connection electrode 4 is brought into contact with the solder 57 on the other land 56 . Then, when the solder 57 is heated, the solder 57 is melted. Thereafter, when the solder 57 is cooled to be solidified, the first connection electrode 3 and the one land 56 are bonded to each other via the solder 57 , and the second connection electrode 4 and the other land 56 are bonded to each other via the solder 57 . In other words, the two lands 56 are individually solder-bonded to the corresponding electrodes in the first connection electrode 3 and the second connection electrode 4 . In this way, the mounting (the flip-chip connection) of the chip resistor 1 to the mounting substrate 54 is completed, and the circuit assembly 55 is finished. Here, on the upper most surfaces of the first connection electrode 3 and the second connection electrode 4 functioning as the external connection electrodes of the chip resistor 1 , the Au layer 32 (gold plating) is formed. Hence, when the chip resistor 1 is mounted on the mounting substrate 54 , it is possible to achieve excellent solder wettability and high reliability.

In the finished circuit assembly 55 , the element formation surface 2 A of the chip resistor 1 and the mounting surface 54 A of the mounting substrate 54 are opposite each other with a gap therebetween and are extended parallel to each other (also see FIG. 23 ). The dimension of the gap corresponds to the total of the thickness of a part protruding from the element formation surface 2 A in the first connection electrode 3 or the second connection electrode 4 and the thickness of the solder 57 .

As shown in FIG. 22 , in cross section, for example, the first connection electrode 3 and the second connection electrode 4 are formed in the shape of the letter L by integrally forming the surface part on the element formation surface 2 A and the side surface parts on the side surfaces 2 C and 2 E. Hence, as shown in FIG. 23 , when the circuit assembly 55 (to be exact, the part where the chip resistor 1 and the mounting substrate 54 are bonded) is seen in a direction normal to the mounting surface 54 A (the element formation surface 2 A) (the direction orthogonal to these surfaces), the solder 57 bonding the first connection electrode 3 and the one land 56 is sucked not only to the surface part of the first connection electrode 3 but also to the side surface parts. Likewise, the solder 57 bonding the second connection electrode 4 and the other land 56 is sucked not only to the surface part of the second connection electrode 4 but also to the side surface parts.

As described above, in the chip resistor 1 , the first connection electrode 3 is formed so as to integrally cover the three side surfaces 2 C, 2 D, and 2 F of the substrate 2 , and the second connection electrode 4 is formed so as to integrally cover the three side surfaces 2 E, 2 D, and 2 F of the substrate 2 . In other words, since the electrodes are formed not only on the element formation surface 2 A but also on the side surfaces 2 C to 2 F of the substrate 2 , the adhesion area when the chip resistor 1 is soldered to the mounting substrate 54 can be increased. Consequently, since the amount of adsorption of the solder 57 to the first connection electrode 3 and the second connection electrode 4 can be increased, the adhesion strength can be enhanced.

As shown in FIG. 23 , the solder 57 is adsorbed so as to extend from the element formation surface 2 A to the side surfaces 2 C to 2 F of the substrate 2 . Hence, in the mounted state, the first connection electrode 3 is held with the three side surfaces 2 C, 2 D, and 2 F by the solder 57 , and the second connection electrode 4 is held with the three side surfaces 2 E, 2 D, and 2 F by the solder 57 , with the result that all the side surfaces 2 C to 2 F of the rectangular chip resistor 1 can be fixed by the solder 57 . In this way, it is possible to stabilize the mounting shape of the chip resistor 1 .

FIG. 24 is a schematic cross-sectional view of a chip capacitor 58 according to a second preferred embodiment of the first invention. In FIG. 24 , the elements corresponding to those in FIG. 13 described previously are provided with the same reference symbols.

In the chip capacitor 58 , as an example of the circuit element of the first invention, a capacitor 59 is formed in the element region 5 . The capacitor 59 includes a lower electrode 65 formed with the first wiring film 12 , a dielectric film 66 formed with the second insulating film 13 and an upper electrode 67 formed with the second wiring film 19 . The lower electrode 65 and the upper electrode 67 are opposite each other via the dielectric film 66 , and thus the capacitor 59 is formed.

The lower electrode 65 includes a contact portion 68 that is drawn from a region opposite the upper electrode 67 to the side of the second connection electrode 4 . The second wiring film 19 (lower wiring film 69 ) forming the anchor portion 24 of the second connection electrode 4 is connected via the through holes 21 to the contact portion 68 .

As with the lower wiring film 69 , the upper electrode 67 is formed on the second insulating film 13 . In other words, in the preferred embodiment, in a region on the second insulating film 13 , the upper electrode 67 and the lower wiring film 69 are disposed at an interval left therebetween.

The chip capacitor 58 further includes a third insulating film 70 and a third wiring film 71 between the second insulating film 13 and the passivation film 14 .

The third insulating film 70 is formed of, for example, an insulating material such as SiO 2 (silicon oxide). The thickness of the third insulating film 70 is, for example, 0.15 to 1.5 μm. Although the third insulating film 70 is formed substantially over the entire region on the second insulating film 13 so as to cover the second insulating film 19 , the anchor portion 24 of the second connection electrode 4 is selectively exposed. Hence, the end surface of the third insulating film 70 coincides with the end surface 27 of the resin film 15 on the side of the second connection electrode 4 .

In the chip capacitor 58 , in the electrode region 16 immediately below the first connection electrode 3 , a plurality of concave portions 72 are formed that pass through the third insulating film 70 and the second insulating film 13 and that extends halfway along the direction of the thickness of the first insulating film 9 . In other words, one concave portion 72 is defined by continuously forming the concave portion of the first insulating film 9 and the through holes of the second insulating film 13 and the third insulating film 70 . In the preferred embodiment, as with the plurality of concave portions 17 , the plurality of concave portions 72 are arrayed in a matrix in plan view when seen in a direction normal to the element formation surface 2 A. In this way, in the electrode region 16 of the first connection electrode 3 , an internal concave/convex structure 73 formed by the aggregation of a plurality of concave portions 72 is formed. The depth of the plurality of concave portions 72 is greater than that of the plurality of concave portions 17 due to the depth of the third insulating film 70 . On the other hand, in the first preferred embodiment of the first invention described previously, a plurality of concave portions 17 having the same depth is formed in the electrode region 16 of the first connection electrode 3 and the second connection electrode 4 .

The third wiring film 71 is formed of Al (aluminum) or an alloy (Al—Cu alloy) of Al and Cu (copper). The thickness of the third wiring film 71 is about 8000 angstroms. In the preferred embodiment, the third wiring film 71 includes an upper wiring film 74 that electrically connects the first connection electrode 3 and the upper electrode 67 .

The upper wiring film 74 is formed so as to extend from the element region 5 through the boundary between the element region 5 and the electrode region 16 of the first connection electrode 3 to the electrode region 16 .

In the element region 5 , the upper wiring film 74 is connected as a via through a through hole 75 formed in the third insulating film 70 to the upper electrode 67 .

On the other hand, in the electrode region 16 of the first connection electrode 3 , the upper wiring film 74 is extended into the concave portion 72 of the internal concave/convex structure 73 . In other words, the upper wiring film 74 includes, as parts of the first connection electrode 3 , an anchor portion 76 that is embedded in the direction of thickness of an insulating film (in the preferred embodiment, the first insulating film 9 , the second insulating film 13 , and the third insulating film 70 ) and that is fixed. Since the depth of a plurality of concave portions 72 >the depth of a plurality of concave portions 17 , in the chip capacitor 58 , for the amount of embedding of the anchor portion in the insulating film (corresponding to the amount of embedding of the portion 22 in FIG. 14 ), the side of the first connection electrode 3 (the upper electrode 67 )>the side of the second connection electrode 4 (the lower electrode 65 ) holds true.

In the surface of the anchor portion 76 , as in the anchor portion 24 , an intermediate concave/convex structure 78 formed with a plurality of concave portions 77 receiving the concave/convex shape of the internal concave/convex structure 73 is formed. The internal concave/convex structure 73 and the intermediate concave/convex structure 78 described above are present, and thus in the main surface 3 A of the first connection electrode 3 , the external concave/convex structure 6 is formed.

In the chip capacitor 58 , the anchor portions 24 and 76 and the external concave/convex structures 6 and 7 are formed, and thus it is possible to realize the same actions and effects as the chip resistor 1 .

FIG. 25 is a schematic cross-sectional view of a chip diode 79 according to a third preferred embodiment of the first invention. In FIG. 25 , the elements corresponding to those in FIG. 13 described previously are provided with the same reference symbols.

In the chip diode 79 , as an example of the circuit element of the first invention, a diode 80 is formed in the element region 5 . The diode 80 is formed with a pn bonding portion of a p + type substrate 2 and an n + type region 81 formed on the surface portion of the substrate 2 . In the surface portion of the substrate 2 , a p + type region 82 is formed while being separated at an interval from the n + type region 81 .

The chip diode 79 includes, as an example of the p-side film of the first invention formed with the first wiring film 12 , an anode wiring film 83 , and includes, as an example of the n-side film of the first invention, a cathode wiring film 84 .

The anode wiring film 83 is connected via the first insulating film 9 to the p + type region 82 , and the end portion on the side opposite thereto forms the anchor portion 24 in the electrode region 16 of the first connection electrode 3 . Likewise the cathode wiring film 84 is connected via the first insulating film 9 to the n + type region 81 , and the end portion on the side opposite thereto forms the anchor portion 24 in the electrode region 16 of the second connection electrode 4 .

In the chip diode 79 , the passivation film 14 and the resin film 15 are formed substantially over the entire region of the element formation surface 2 A, and in each electrode region 16 , an opening 85 that exposes part of the anchor portion 24 is included therein. The external connection portion 29 embedded in the opening 85 is formed so as to cover the peripheral portion of the opening 85 . In other words, in the surface of the resin film 15 , the first connection electrode 3 and the second connection electrode 4 are disposed in a position displaced inwardly with respect to the end surface (the end surface of the chip) of the resin film 15 , and a constant clearance is provided between the end surface of the resin film 15 and the peripheral edge of the first connection electrode 3 and the second connection electrode 4 .

In the chip diode 79 , the anchor portion 24 and the external concave/convex structures 6 and 7 are formed, and thus it is possible to realize the same actions and effects as the chip resistor 1 .

Although the example of the chip part according to the preferred embodiment of the first invention (the chip resistor 1 , the chip capacitor 58 , and the chip diode 79 ) is described above, the first invention can be carried out with other preferred embodiments.

For example, the first invention can be applied to other chip parts such as a chip inductor, a chip fuse, a bidirectional Zener diode chip. When the first invention is applied to a chip resistor, a chip capacitor and a chip diode, the arrangement of the element region 5 is not limited to the arrangement described above. For example, unlike the arrangement described above, the resistor portion formed in the element region 5 may be formed such that the resistance value cannot be adjusted by the blowing of the fuses F.

For example, as shown in FIG. 26 , the external concave/convex structures 6 and 7 may be formed along the peripheral edge of the first connection electrode 3 and the second connection electrode 4 such that a flat portion 86 is formed in the center portion of the first connection electrode 3 and the second connection electrode 4 . The flat portion 86 is formed with a smooth surface in which the external concave/convex structures 6 and 7 are not formed. When the flat portion 86 is formed, for example, in the step of FIG. 15L , the flat portion 86 is selected as a contact target of the probes 45 , and thus it is possible to satisfactorily prevent the probes 45 from being damaged at the time of contact with the first connection electrode 3 and the second connection electrode 4 .

As shown in FIG. 27 , the flat portion 86 described above may be formed along the peripheral edge of the first connection electrode 3 and the second connection electrode 4 or can be applied with other various patterns. In the case of FIG. 27 , in the center portion of the first connection electrode 3 and the second connection electrode 4 , the external concave/convex structures 6 and 7 surrounded by the flat portion 86 are formed. Furthermore, a plurality of flat portions 86 may be formed in one electrode.

The anchor portion 24 does not need to completely fill the concave portions 17 of the internal concave/convex structure 18 , and as shown in FIG. 28 , may be formed along the recesses and projections of the internal concave/convex structure 18 . In this case, in the concave portions 17 , the external connection portion 29 may be embedded in the space within the anchor portion 24 . For example, unlike the preferred embodiment described previously, the anchor portion 24 can be formed by forming the second wiring film 19 so as to have a relatively small thickness such that the concave portions 17 are prevented from being completely refilled in the second wiring film 19 . This arrangement can be applied to the anchor portion 76 .

As a regular pattern, the alignment pattern of a plurality of concave portions 17 may be a staggered pattern as shown in FIG. 29 or may be an irregular pattern.

The anchor portion does not need to be formed with a wiring film, and as shown in FIG. 30 , the external connection portion 29 may integrally include an anchor portion 87 .

Various design changes can be made in the scope indicated by the scope of claims.

FIG. 31 is an external view of a smartphone 101 according to a preferred embodiment of the first invention.

In the smartphone 101 , electronic parts are stored within a housing 102 in the shape of a flat rectangular parallelepiped.

In the housing 102 , a pair of rectangular main surfaces are provided on the front side and the rear side, and the pair of main surfaces are coupled by four side surfaces. The display surface of a display panel 103 formed with a liquid crystal panel, an organic EL or the like is exposed to one of the main surfaces of the housing 102 . The display surface of the display panel 103 forms a touch panel, and provides an input interface for a user.

The display panel 103 is formed in the shape of a rectangle that covers a large proportion of the one main surface of the housing 102 . Operation buttons 104 are disposed along one short side of the display panel 103 . In the preferred embodiment, a plurality of (three) operation buttons 104 are arrayed along the short side of the display panel 103 . The user operates the operation buttons 104 and the touch panel to operate smartphone 101 and thereby can call and perform the necessary function.

In the vicinity of the other short side of the display panel 103 , a speaker 105 is disposed. The speaker 105 provides an earpiece for a telephone function, and is also used as an acoustic unit for reproducing music data and the like. On the other hand, near the operation buttons 104 , a microphone 106 is disposed on one side surface of the housing 102 . The microphone 106 provides a mouthpiece for the telephone function, and can also be used as a recording microphone.

FIG. 32 is a diagram for illustrating the internal structure of the smartphone 101 of FIG. 31 .

The circuit assembly 55 includes the mounting substrate 54 and circuit parts mounted on the mounting surface 54 A of the mounting substrate 54 . A plurality of circuit parts include a plurality of integrated circuit elements (IC) 112 to 120 and a plurality of chip parts. The plurality of ICs include a transmission processing IC 112 , a one-segment TV receiving IC 113 , a GPS receiving IC 114 , an FM tuner IC 115 , a power supply IC 116 , a flash memory 117 , a microcomputer 118 , a power supply IC 119 and a baseband IC 120 .

The plurality of chip parts include chip inductors 121 , 125 , and 135 , chip resistors 122 , 124 , and 133 , chip capacitors 127 , 130 , and 134 , chip diodes 128 and 131 and bidirectional Zener diode chips 141 to 148 . These chip parts correspond to the chip parts described in the preferred embodiment described previously, and are mounted by, for example, flip-chip bonding to the mounting surface 54 A of the mounting substrate 54 .

The bidirectional Zener diode chips 141 to 148 are provided to perform absorbing positive and negative surges, etc., in signal input lines to the one-segment TV receiving IC 113 , the GPS receiving IC 114 , the FM tuner IC 115 , the power supply IC 116 , the flash memory 117 , the microcomputer 118 , the power supply IC 119 and the baseband IC 120 .

The transmission processing IC 112 incorporates an electronic circuit for generating a display control signal for the display panel 103 and receiving an input signal from the touch panel on the surface of the display panel 103 . For connection to the display panel 103 , a flexible wiring 609 is connected to the transmission processing IC 112 .

The one-segment TV receiving IC 113 incorporates an electronic circuit of a receiver for receiving radio waves of the one-segment broadcast (digital terrestrial TV broadcasting having a portable device as a reception target). In the vicinity of the one-segment TV receiving IC 113 , a plurality of chip inductors 121 , a plurality of chip resistors 122 , and a plurality of bidirectional Zener diode chips 141 are disposed. The one-segment TV receiving IC 113 , the chip inductor 121 , the chip resistor 122 , and the bidirectional Zener diode chip 141 form a one-segment broadcast receiving circuit 123 . The chip inductor 121 and the chip resistor 122 respectively have an inductance and a resistance adjusted accurately, and provide a highly accurate circuit constant to the one-segment broadcast receiving circuit 123 .

The GPS receiving IC 114 incorporates an electronic circuit that receives radio waves from the GPS satellites to output positional information to the smartphone 101 . In the vicinity of GPS receiving IC 114 , a plurality of bidirectional Zener diode chips 142 are disposed.

The FM tuner IC 115 forms an FM broadcast receiving circuit 126 together with a plurality of chip resistors 124 , a plurality of chip inductors 125 , and a plurality of bidirectional Zener diode chips 143 mounted on the mounting substrate 54 in the vicinity thereof. The chip resistor 124 and the chip inductor 125 respectively have a resistance value and an inductance adjusted accurately, and provide a highly accurate circuit constant to the FM broadcast receiving circuit 126 .

In the vicinity of the power supply IC 116 , a plurality of chip capacitors 127 , a plurality of chip diodes 128 , and a plurality of bidirectional Zener diode chips 144 are mounted on the mounting surface 54 A of the mounting substrate 54 . The power supply IC 116 forms a power supply circuit 129 together with the chip capacitor 127 , the chip diode 128 , and the bidirectional Zener diode chip 144 .

The flash memory 117 is a storage device for recording an operating system program, data generated within the smartphone 101 , data and programs acquired by a communication function from the outside and the like. In the vicinity of the flash memory 117 , a plurality of bidirectional Zener diode chips 145 are disposed.

The microcomputer 118 is a computation processing circuit that incorporates a CPU, a ROM, and a RAM and that performs various types of computation processing to realize a plurality of functions in the smartphone 101 . More specifically, image processing and computation processing for various types of application programs are realized by the function of the microcomputer 118 . In the vicinity of the microcomputer 118 , a plurality of bidirectional Zener diode chips 146 are disposed.

Near the power supply IC 119 , a plurality of chip capacitors 130 , a plurality of chip diodes 131 , and a plurality of bidirectional Zener diode chips 147 are mounted on the mounting surface 54 A of the mounting substrate 54 . The power supply IC 119 forms a power supply circuit 132 together with the chip capacitor 130 , the chip diode 131 , and the bidirectional Zener diode chip 147 .

Near the baseband IC 120 , a plurality of chip resistors 133 , a plurality of chip capacitors 134 , a plurality of chip inductors 135 , and a plurality of bidirectional Zener diode chips 148 are mounted on the mounting surface 54 A of the mounting substrate 54 . The baseband IC 120 forms a baseband communication circuit 136 together with the chip resistor 133 , the chip capacitor 134 , the chip inductor 135 , and a plurality of bidirectional Zener diode chips 148 . The baseband communication circuit 136 provides a communication function for telephone communication and data communication.

In the arrangement described above, power appropriately adjusted by the power supply circuits 129 and 132 is supplied to the transmission processing IC 112 , the GPS receiving IC 114 , the one-segment broadcast receiving circuit 123 , the FM broadcast receiving circuit 126 , the baseband communication circuit 136 , the flash memory 117 , and the microcomputer 118 . The microcomputer 118 performs computation processing in response to an input signal input via the transmission processing IC 112 , and outputs a display control signal from the transmission processing IC 112 to the display panel 103 to make the display panel 103 produce various types of display.

When an instruction to receive the one-segment broadcast is provided by the operation of the touch panel or the operation buttons 104 , the one-segment broadcast is received by the function of the one-segment broadcast receiving circuit 123 . Then, computation processing for outputting an image received to the display panel 103 and converting sound received into acoustic sound from the speaker 105 is performed by the microcomputer 118 .

When the positional information of the smartphone 101 is needed, the microcomputer 118 acquires the positional information output by the GPS receiving IC 114 , and performs computation processing using the positional information.

Furthermore, when an instruction to receive FM broadcast is input by the operation of the touch panel or the operation buttons 104 , the microcomputer 118 starts up the FM broadcast receiving circuit 126 , and performs computation processing for outputting the received sound from the speaker 105 .

The flash memory 117 is used to store data acquired by communication, to compute the microcomputer 118 , and to store data produced by an input from the touch panel. As necessary, the microcomputer 118 writes data into the flash memory 117 and reads data from the flash memory 117 .

The function of telephone communication or data communication is realized by the baseband communication circuit 136 . The microcomputer 118 controls the baseband communication circuit 136 to perform processing for receiving and transmitting sound or data.

[2] Second Invention and Third Invention

An object of the second invention is to provide a chip inductor in which the Q (Quality Factor) value of a coil is high and a circuit assembly that includes it.

Another object of the second invention is to provide a method of manufacturing a chip inductor in which the Q value of a coil is high.

The second invention has the following features.

A1. A chip inductor including: a substrate that has an element formation surface; a coil formation trench that is formed in the substrate by digging down from the element formation surface and that is formed in the shape of a spiral in plan view when seen in a normal direction perpendicular to the element formation surface; and a coil that is formed with a conductive member embedded within the coil formation trench.

Since in this arrangement, it is possible to increase the cross-sectional area of the coil (cross-sectional area perpendicular to a direction in which the coil is extended in the spiral direction), it is possible to decrease the internal resistance of the coil. In this way, it is possible to increase the Q value of the coil, with the result that it is possible to provide a high performance chip inductor.

Since the coil formation trench is formed in the substrate, the conductive member is embedded within the coil formation trench and thus the coil can be formed, it is easy to manufacture the coil. In this way, it is possible to provide a chip inductor that is easily manufactured.

A2. The chip inductor described in “A1” further including: a first electrode which is disposed on the element formation surface and to which one end portion of the coil is electrically connected; and a second electrode which is disposed on the element formation surface and to which the other end portion of the coil is electrically connected.

A3. The chip inductor described in “A2,” where the element formation surface is rectangular in plan view, the first electrode is disposed on an end portion of the element formation surface, the second electrode is disposed on the other end portion of the element formation surface, and the coil formation trench is formed in a region between the first electrode and the second electrode in the element formation surface.

A4. The chip inductor described in “A2” or “A3” further including: a first insulating film which is formed on the element formation surface so as to cover the coil and which includes, in regions corresponding to the one end portion and the other end portion of the coil, a first contact hole and a second contact hole, respectively, where the first electrode and the second electrode are formed on the first insulating film, the first electrode is connected via the first contact hole to the one end portion of the coil and the second electrode is connected via the second contact hole to the other end portion of the coil.

A5. The chip inductor described in “A2” or “A3” further including: a spiral wiring which is formed on the element formation surface so as to be along the coil and to make contact with the coil; and a first insulating film which is formed on the element formation surface so as to cover the spiral wiring and which includes, in regions corresponding to one end portion and the other end portion of the spiral wiring, a first contact hole and a second contact hole, respectively, where the first electrode and the second electrode are formed on the first insulating film, the first electrode is connected via the first contact hole to the one end portion of the spiral wiring and the second electrode is connected via the second contact hole to the other end portion of the spiral wiring.

In this arrangement, even when an area is produced where the conductive member is unsatisfactorily embedded within the coil formation trench, it is possible to compensate for the area with the spiral wiring. In this way, even when the conductive member is unsatisfactorily embedded within the coil formation trench, and thus a break is produced halfway along the coil, the break can be connected by the spiral wiring.

A6. The chip inductor described in any one of “A2” to “A5” further including: a plurality of first electrode-side trenches which are formed, in the region corresponding to the first electrode in the element formation surface, in the substrate by digging down from the element formation surface; and a plurality of second electrode-side trenches which are formed, in the region corresponding to the second electrode in the element formation surface, in the substrate by digging down from the element formation surface, where a surrounding wall of each of the first electrode-side trenches in the substrate is formed on an insulator portion having insulation, and a surrounding wall of each of the second electrode-side trenches in the substrate is formed on an insulator portion having insulation.

In this arrangement, at least a part of a part opposite the first electrode and a part opposite the second electrode in the substrate can be formed with the insulator portion having insulation. In this way, a parasitic capacitance formed between the substrate and the first electrode and a parasitic capacitance formed between the substrate and the second electrode can be reduced as compared with a case where a main body substrate (semiconductor substrate) having no insulator portion is used.

A7. The chip inductor described in “A6,” where the plurality of first electrode-side trenches are formed, in plan view, in a shape of a rectangle which is long in one direction, and are disposed at an interval in a direction perpendicular to the one direction, the plurality of second electrode-side trenches are formed, in plan view, in a shape of a rectangle which is long in one direction, and are disposed at an interval in a direction perpendicular to the one direction, an entire region of a wall between the first electrode-side trenches adjacent in the substrate is formed as an insulator portion and an entire region of a wall between the second electrode-side trenches adjacent in the substrate is formed as an insulator portion. In this arrangement, it is possible to more effectively reduce the parasitic capacitance formed between the substrate and the first electrode and the parasitic capacitance formed between the substrate and the second electrode.

A8. The chip inductor described in “A6” or “A7,” where a second insulating film is formed on an inner surface of each of the first electrode-side trenches and on an inner surface of each of the second electrode-side trenches. In this arrangement, it is possible to more effectively reduce the parasitic capacitance formed between the substrate and the first electrode and the parasitic capacitance formed between the substrate and the second electrode.

A9. The chip inductor described in “A8,” where a substantially entire region within each of the first electrode-side trenches and a substantially entire region within each of the second electrode-side trenches are filled by the second insulating film. In this arrangement, it is possible to more effectively reduce the parasitic capacitance formed between the substrate and the first electrode and the parasitic capacitance formed between the substrate and the second electrode.

A10. The chip inductor described in any one of “A6” to “A9,” where the plurality of first electrode-side trenches and the plurality of second electrode-side trenches are formed in the same step as the coil formation trench. In this arrangement, it is possible to manufacture the first and second electrode-side trenches in the same step as the coil formation trench, and thus it is possible to reduce the number of manufacturing steps.

A11. The chip inductor described in any one of “A2” to “A10,” where the coil formation trench is formed with a plurality of parallel trenches disposed at an interval from and parallel to each other, the coil is formed with a plurality of parallel coils embedded in the parallel trenches, one end portion of the plurality of parallel coils is connected to the first electrode and the other end portion of the plurality of parallel coils is connected to the second electrode.

In this arrangement, though as compared with a case where the coil is formed with one coil, the number of windings is reduced, a plurality of parallel coils are connected in parallel and thus the inductance is reduced, since the internal resistance of the entire coil is also reduced, it is possible to obtain a satisfactory Q value.

A12. The chip inductor described in any one of “A1” to “A11,” where the coil formation trench is formed, in plan view, in a shape of a polygonal spiral.

A13. The chip inductor described in any one of “A1” to “A11,” where the coil formation trench is formed, in plan view, in a shape of a circular spiral.

A14. The chip inductor described in any one of “A1” to “A13,” where a depth of the coil formation trench is 10 μm or more. In this arrangement, it is possible to increase the cross-sectional area of the coil, and thus it is possible to decrease the internal resistance of the coil. In this way, it is possible to increase the Q value of the coil.

A15. The chip inductor described in any one of “A1” to “A13,” where a depth of the coil formation trench is 10 μm or more and 82 μm or less.

A16. The chip inductor described in any one of “A1” to “A15,” where a width of the coil formation trench is 1 μm or more and 3 μm or less.

A17. A circuit assembly including: a mounting substrate; and the chip inductor described in any one of “A1” to “A16” mounted in the mounting substrate. In this arrangement, it is possible to provide a circuit assembly using a chip inductor having a high Q value.

A18. The circuit assembly described in “A17,” where the chip inductor is connected to the mounting substrate by wireless bonding. In this arrangement, it is possible to decrease the occupied space of the chip inductor on the mounting substrate, and thus it is possible to contribute to the high-density mounting of electronic parts.

A19. A method of manufacturing a chip inductor, the method including: a first step of forming, on a substrate having an element formation surface, by digging down from the element formation surface, a coil formation trench that is formed in the shape of a spiral in plan view when seen in a normal direction perpendicular to the element formation surface; and a second step of embedding a conductive member within the coil formation trench to form a coil within the coil formation trench.

With this manufacturing method, it is possible to form the coil within the coil formation trench formed in the substrate. Hence, it is possible to provide a chip inductor having the same effects as described in “A1.”

A20. The method of manufacturing a chip inductor described in “A19,” the method further including: a third step of forming an insulating layer on the element formation surface so as to coat the coil; a fourth step of forming, in the insulating layer, a first contact hole which exposes one end portion of the coil and simultaneously forming a second contact hole which exposes the other end portion of the coil; and a fifth step of forming, on the insulating film, the first electrode in contact with the one end portion of the coil via the first contact hole and the second electrode in contact with the other end portion of the coil via the second contact hole.

With this manufacturing method, it is possible to form, on the insulating film formed on the element formation surface, the first electrode to which the one end portion of the coil is connected and the second electrode to which the other end portion of the coil is connected.

An object of the third invention is to provide a chip inductor in which the Q (Quality Factor) value of the coil is high and in which it is easy to determine the polarity direction and a circuit assembly that includes it.

Another object of the third invention is to provide a method of manufacturing a chip inductor in which the Q value of the coil is high and in which it is easy to determine the polarity direction.

The third invention has the following features.

B1. A chip inductor including: a substrate that has an element formation surface; a coil formation trench that is formed in the substrate by digging down from the element formation surface and that is formed in the shape of a spiral in plan view when seen in a normal direction perpendicular to the element formation surface; a coil that is formed with a conductive member embedded within the coil formation trench; a first electrode which is disposed on the element formation surface of the substrate and to which one end portion of the coil is electrically connected; and a second electrode which is disposed on the element formation surface of the substrate and to which the other end portion of the coil is electrically connected, where in only the surface of any one of the first electrode and the second electrode, a plurality of concave portions are formed.

Since in this arrangement, it is possible to increase the cross-sectional area of the coil (cross-sectional area perpendicular to a direction in which the coil is extended in the spiral direction), it is possible to decrease the internal resistance of the coil. In this way, it is possible to increase the Q value of the coil, with the result that it is possible to provide a high performance chip inductor.

Since the coil formation trench is formed in the substrate, the conductive member is embedded within the coil formation trench and thus the coil can be formed, it is easy to manufacture the coil. In this way, it is possible to provide a chip inductor that is easily manufactured.

When image inspection is performed on the chip inductor, light from a light source is applied to the surfaces of the first electrode and the second electrode, and images of the surfaces are imaged with a camera. In this arrangement, in only the surface of any one of the first electrode and the second electrode, a plurality of concave portions are formed. The light incident on the surface of the electrode where the concave portions are formed is diffusely reflected off the concave portions. By contrast, the light incident on the surface of the electrode where the concave portions are not formed is unlikely to be diffusely reflected off the concave portions. Hence, a large difference is produced between image information (for example, brightness information) on the first electrode and image information on the second electrode obtained with the camera. In this way, based on the image information obtained with the camera, it is possible to clearly identify the first electrode and the second electrode. In other words, in this arrangement, at the time of the image inspection, it is possible to determine the polarity direction of the chip inductor without forming a mark indicating the polarity direction on the outer surface of the substrate.

B2. The chip inductor described in “B1,” where the element formation surface is rectangular in plan view, the first electrode is disposed on an end portion of the element formation surface, the second electrode is disposed on the other end portion of the element formation surface and the coil formation trench is formed in a region between the first electrode and the second electrode in the element formation surface.

B3. The chip inductor described in “B1” or “B2,” where in the element formation surface of the substrate, in plan view, a first underlying concave portion is formed in the same position as a position in which the concave portion is formed.

In this arrangement, with the first underlying concave portion formed in the element formation surface of the substrate, it is possible to form the concave portion in the surface of any one of the first electrode and the second electrode formed on the element formation surface. In other words, the first underlying concave portion is previously formed in the element formation surface of the substrate, and thus without addition of a step of separately forming the concave portion in the surface of any one of the first electrode and the second electrode, it is possible to form the concave portion in the surface of any one of the first electrode and the second electrode.

B4. The chip inductor described in “B3” further including: an insulating film formed between the first electrode and the second electrode in the element formation surface, where in the surface of the insulating film, in plan view, a second underlying concave portion is formed in the same position as the position in which the first underlying concave portion is formed.

In this arrangement, with the first underlying concave portion formed in the element formation surface of the substrate, it is possible to form the second underlying concave portion in the surface of the insulating film formed on the element formation surface. Then, with the second underlying concave portion formed in the surface of the insulating film, it is possible to form the concave portion in the surface of any one of the first electrode and the second electrode formed on the insulating film.

B5. The chip inductor described in “B4,” where the insulating film is formed on the element formation surface so as to cover the coil and includes, in regions corresponding to the one end portion and the other end portion of the coil, a first contact hole and a second contact hole formed respectively, the first electrode and the second electrode are formed on the insulating film, the first electrode is connected via the first contact hole to the one end portion of the coil and the second electrode is connected via the second contact hole to the other end portion of the coil.

B6. The chip inductor described in any one of “B3” to “B5,” where each of the plurality of concave portions is formed, in plan view, in the shape of a straight line extending in one direction, the concave portions are disposed at an interval in a direction perpendicular to the one direction and include a plurality of concave portion formation trenches that are formed, in plan view, in the same positions as the positions in which the concave portions are formed in the substrate by digging down from the element formation surface and conductive members embedded within the concave portion formation trenches and the first underlying concave portion is formed in the surface of the conductive member within each of the concave portion formation trenches.

In this arrangement, a plurality of concave portion formation trenches are formed in the substrate, the conductive members are embedded within the concave portion formation trenches and thus the first underlying concave portions can be formed.

B7. The chip inductor described in “B6,” where the plurality of concave portion formation trenches are formed in the same step as the coil formation trench. In this arrangement, it is possible to manufacture the concave portion formation trenches in the same step as the coil formation trench, and thus it is possible to reduce the number of manufacturing steps.

B8. The chip inductor described in any one of “B1” to “B7,” where the coil formation trench is formed with a plurality of parallel trenches disposed at an interval from and parallel to each other, the coil is formed with a plurality of parallel coils embedded in the plurality of parallel trenches, one end portion of the plurality of parallel coils is connected to the first electrode and the other end portion of the plurality of parallel coils is connected to the second electrode.

In this arrangement, though as compared with a case where the coil is formed with one coil, the number of windings is reduced, a plurality of parallel coils are connected in parallel and thus the inductance is reduced, since the internal resistance of the entire coil is also reduced, it is possible to obtain a satisfactory Q value.

B9. The chip inductor described in any one of “B1” to “B8,” where the coil formation trench is formed, in plan view, in a shape of a polygonal spiral.

B10. The chip inductor described in any one of “B1” to “B8,” where the coil formation trench is formed, in plan view, in a shape of a circular spiral.

B11. The chip inductor described in any one of “B1” to “B10,” where a depth of the coil formation trench is 10 μm or more. In this arrangement, it is possible to increase the cross-sectional area of the coil, and thus it is possible to decrease the internal resistance of the coil. In this way, it is possible to increase the Q value of the coil.

B12. The chip inductor described in any one of “B1” to “B10,” where a depth of the coil formation trench is 10 μm or more and 80 μm or less.

B13. The chip inductor described in any one of “B1” to “B12,” where a width of the coil formation trench is 1 μm or more and 3 μm or less.

B14. A circuit assembly including: a mounting substrate; and the chip inductor described in any one of “B1” to “B13,” mounted in the mounting substrate. In this arrangement, it is possible to provide a circuit assembly using a chip inductor in which the Q value is high and in which it is easy to determine the polarity direction.

B15. The circuit assembly described in “B14,” where the chip inductor is connected to the mounting substrate by wireless bonding. In this arrangement, it is possible to decrease the occupied space of the chip inductor on the mounting substrate, and thus it is possible to contribute to the high-density mounting of electronic parts.

B16. A method of manufacturing a chip inductor, the method including: a first step of preparing a substrate having an element formation surface including a first electrode formation region, a second electrode formation region and a coil formation region; a second step of forming, in the coil formation region, a coil formation trench in the shape of a spiral in plan view when seen in a normal direction perpendicular to the element formation surface by digging down from the element formation surface in the substrate and simultaneously forming a plurality of concave formation trenches in any one of the first electrode formation region and the second electrode formation region; a third step of depositing a conductive member on the element formation surface, thereafter the conductive member is smoothed and thus the conductive member is embedded in inner surfaces of the coil formation trench and each of the concave formation trenches and simultaneously forming a first underlying concave portion on the surface of the conductive member within each of the concave formation trenches; a fourth step of forming an insulating film on the element formation surface to form a second underlying concave portion in a position of the first underlying concave portion in the surface of the insulating film; a fifth step of forming a first electrode and a second electrode in positions corresponding to the first electrode formation region and the second electrode formation region on the insulating film respectively, to form a concave portion in a position of the second underlying concave portion in the surface of one of the electrodes.

In the manufacturing method in the invention, it is possible to form the concave portion in the surface of any one of the first electrode and the second electrode. Hence, it is possible to provide a chip inductor having the same effects as those described in “B1” described previously.

B17. The method of manufacturing a chip inductor described in “B16,” the method further including: a step of forming, between the second step and the third step, an insulating film on the inner surfaces of the coil formation trench and each of the concave formation trenches and thereafter forming a barrier metal film on the insulating film.

Preferred embodiments of the second invention and preferred embodiments of the third invention will be described in detail with reference to FIGS. 33A to 92 . The symbols in FIGS. 33A to 92 are not related to the symbols in FIGS. 1 to 32 used in the description of the first invention.

FIG. 33A is a partially cut perspective view of the chip inductor according to the first preferred embodiment of the second invention. FIG. 33B is a perspective view showing a coil formed within the chip inductor.

The chip inductor 1 is a minute chip part and is formed in the shape of a rectangular parallelepiped. The planar shape of the chip inductor 1 may be rectangular, the length L in the longitudinal direction may be about 0.4 mm and the length W in the lateral direction may be about 0.2 mm. The thickness T of the entire chip inductor 1 may be about 0.15 mm.

The chip inductor 1 includes a substrate 2 , a coil 3 that is formed within the substrate 2 , a first electrode 4 that is connected to one end portion of the coil 3 and a second electrode 5 that is connected to the other end portion of the coil 3 .

FIG. 34 is a plan view of the chip inductor, FIG. 35 is a cross-sectional view taken along line XXXV-XXXV in FIG. 34 , FIG. 36 is a partially enlarged cross-sectional view of FIG. 35 , FIG. 37 is a cross-sectional view taken along line XXXVII-XXXVII in FIG. 34 , FIG. 38 is a cross-sectional view taken along line XXXVIII-XXXVIII in FIG. 34 and FIG. 39 is a plan view showing a structure of the surface of the substrate by removing an arrangement formed on the surface of the substrate.

The substrate 2 is formed in the shape of a rectangular parallelepiped, and includes a pair of main surfaces 2 a and 2 b and four side surfaces 2 c . One (the main surface 2 a on the upper surface side in FIG. 33A ) of the pair of main surfaces 2 a and 2 b is an element formation surface. In the following description, the main surface 2 a is referred to as an “element formation surface 2 a ,” and the main surface 2 b on the side opposite to the element formation surface 2 a is referred to as a “rear surface 2 b .” In the preferred embodiment, the substrate 2 is formed with a substrate main body 6 and an insulating film 7 formed on the surface thereof, and the surface of the insulating film 7 on the side opposite to the side of the substrate main body 6 is the element formation surface 2 a . In the preferred embodiment (the same is true in the other preferred embodiments of the second invention), the substrate main body 6 is formed with a silicon substrate, and the insulating film 7 is formed with a thermal oxide film (SiO 2 ). The element formation surface 2 a is formed in the shape of a rectangle in plan view when seen in a normal direction perpendicular to the element formation surface 2 a . The surface (element formation surface 2 a ) of the substrate 2 is covered by an insulating film 8 . The four side surfaces 2 c of the substrate 2 and the outer peripheral surface of the insulating film 8 are covered by a passivation film 9 such as a nitride film.

With reference to FIG. 34 , in the element formation surface 2 a , a first electrode formation region 10 A for the formation of the first electrode 4 is provided at one end portion thereof, and a second electrode formation region 10 B for the formation of the second electrode 5 is provided at the other end portion. These regions 10 A and 10 B are rectangular in plan view. In the element formation surface 2 a between the first electrode formation region 10 A and the second electrode formation region 10 B, a coil formation region 10 C is provided. In the preferred embodiment, the coil formation region 10 C is formed in the shape of a rectangle.

In the first electrode formation region 10 A, the external connection electrode (first external connection electrode) 4 B of the first electrode 4 is disposed, and in the second electrode formation region 10 B, the external connection electrode (second external connection electrode) 5 B of the second electrode 5 is disposed. The first external connection electrode 4 B is rectangular in plan view, and covers the entire region of the first electrode formation region 10 A. The second external connection electrode 5 B is rectangular in plan view, and covers the entire region of the second electrode formation region 10 B.

In the substrate 2 , a coil formation trench 11 is formed by digging down, in the coil formation region 10 C, to a predetermined depth from the element formation surface 2 a . The coil formation trench 11 is formed, in plan view, in the shape of a spiral. In the preferred embodiment, the coil formation trench 11 is formed, in plan view, in the shape of a quadrilateral spiral, and has a plurality of rectilinear portions parallel to the side surfaces 2 c of the substrate 2 . The cross section (cross section in a direction perpendicular to a direction in which the coil formation trench 11 is extended in the spiral direction) of the coil formation trench 11 is formed in the shape of a rectangle which is long in the direction of the thickness of the substrate 2 . For example, the width of the coil formation trench 11 may be 1 μm or more and 3 μm or less. For example, the depth of the coil formation trench 11 may be 10 μm or more and 82 μm or less. The depth of the coil formation trench 11 is preferably 10 μm or more so that the internal resistance of the coil 3 formed within the coil formation trench 11 is decreased.

As shown in FIG. 36 , the coil formation trench 11 is formed with a first trench part 11 a that is formed in the insulating film 7 and a second trench part 11 b that is formed in the substrate main body 6 and that communicates with the first trench part 11 a . On the inner surface of the coil formation trench 11 (the second trench part 11 b ) in the substrate main body 6 , an insulating film 12 formed with an oxide film or the like is formed. In the preferred embodiment, the insulating film 12 is formed with a thermal oxide film (SiO 2 ), and when the thermal oxide film is formed on the inner surface of the coil formation trench 11 , the surrounding wall (the side wall and the bottom wall) of the coil formation trench 11 (the second trench part 11 b ) in the substrate main body 6 is thermally oxidized into an insulator portion (thermal oxide film) 30 having insulation. In the preferred embodiment, an example is described where the entire wall sandwiched by the coil formation trench 11 (the second trench part 11 b ) in the shape of a spiral in the substrate main body 6 is a thermal oxide film.

On the surface of the insulating film 12 within the coil formation trench 11 (the second trench part 11 b ) and on the inner surface of the coil formation trench 11 (the first trench part 11 a ) in the insulating film 7 , a barrier metal film 13 is formed. The barrier metal film 13 is formed of, for example, TiN. The thickness of the barrier metal film 13 is about 400 to 500 angstroms. Within the coil formation trench 11 , a conductive member 51 is embedded while being in contact with the barrier metal film 13 . In the preferred embodiment, the conductive member 51 is formed of tungsten (W). The coil 3 is formed with the conductive member 51 embedded within the coil formation trench 11 . Hence, the coil 3 is formed, in plan view, in the shape of a spiral (in the shape of a quadrilateral spiral) of the same pattern as the coil formation trench 11 . Specifically, the coil 3 includes a plurality of plate-shaped parts parallel to the side surfaces 2 c of the substrate 2 .

On the element formation surface 2 a (the surface of the insulating film 7 ) of the substrate 2 , an insulating film 8 is formed so as to coat the element formation surface 2 a and the conductive member 51 (the coil 3 ). The insulating film 8 is formed, in plan view, in the shape of a rectangle matching with the element formation surface 2 a . The insulating film 8 is formed with, for example, a USG (Undoped Silicate Glass) film. In the insulating film 8 , a first contact hole 14 (see FIGS. 34 and 37 ) that exposes one end portion (outer peripheral side end portion) of the coil 3 and a second contact hole 15 (see FIGS. 34 and 35 ) that exposes the other end portion (inner peripheral side end portion) of the coil 3 are formed. As described above, in the side surfaces 2 c of the substrate 2 and the outer peripheral surface of the insulating film 8 , the passivation film 9 formed with a nitride film or the like is formed.

On the surface of the insulating film 8 , the first electrode 4 and the second electrode 5 are formed. The first electrode 4 includes a first electrode film 4 A that is formed on the surface of the insulating film 8 and a first external connection electrode 4 B that is bonded to the first electrode film 4 A. As shown in FIG. 34 , the first electrode film 4 A includes a drawing electrode 4 Aa that is connected to one end portion of the coil 3 and a first pad 4 Ab that is formed integrally with the drawing electrode 4 Aa. The first pad 4 Ab is formed to be rectangular at one end portion of the element formation surface 2 a . The first external connection electrode 4 B is connected to the first pad 4 Ab. As shown in FIGS. 34 and 37 , the drawing electrode 4 Aa enters the first contact hole 14 from the surface of the insulating film 8 , and is connected to one end portion of the coil 3 within the first contact hole 14 . The drawing electrode 4 Aa is formed straight along a straight line that passes above one end portion of the coil 3 to reach the first pad 4 Ab.

By extending one end portion of the coil formation trench 11 to a position below the first pad 4 Ab, one end portion of the coil 3 may be located in a position below the first pad 4 Ab. In this way, since the first contact hole 14 can be formed in a position below the first pad 4 Ab, one end portion of the coil 3 can be connected to the first pad 4 Ab. In this case, since the first electrode film 4 A can be formed with only the first pad 4 Ab, the drawing electrode 4 Aa is not needed.

The second electrode 5 includes a second electrode film 5 A that is formed on the surface of the insulating film 8 and a second external connection electrode 5 B that is bonded to the second electrode film 5 A. As shown in FIG. 34 , the second electrode film 5 A includes a drawing electrode 5 Aa that is connected to the other end portion of the coil 3 and a second pad 5 Ab that is formed integrally with the drawing electrode 5 Aa. The second pad 5 Ab is formed to be rectangular at the other end portion of the element formation surface 2 a . The second external connection electrode 5 B is connected to the second pad 5 Ab. As shown in FIGS. 34 and 35 , the drawing electrode 5 Aa enters the second contact hole 15 from the surface of the insulating film 8 , and is connected to the other end portion of the coil 3 within the second contact hole 15 . The drawing electrode 5 Aa is formed straight along a straight line that passes above the other end portion of the coil 3 to reach the second pad 5 Ab. In the preferred embodiment, as the electrode films 4 A and 5 A, Al films are used.

The first electrode film 4 A and the second electrode film 5 A are covered by a passivation film 16 formed with a nitride film (SiN) etc., and furthermore, on the passivation film 16 , a resin film 17 such as polyimide is formed. In the passivation film 16 and the resin film 17 , two cutout portions 18 and 19 are formed that respectively expose a region other than an edge portion on the inner side of the surface of the first pad 4 Ab of the first electrode film 4 A and a region other than an edge portion on the inner side of the surface of the second pad 5 Ab of the second electrode film 5 A. In other words, the passivation film 16 and the resin film 17 are formed, in plan view, in a region corresponding to the coil formation region 10 C of the element formation surface 2 a , and cover the insulating film 8 , the edge portion on the inner side of the surface of the first pad 4 Ab, and the edge portion on the inner side of the surface of the second pad 5 Ab.

The first external connection electrode 4 B is filled in the cutout portion 18 , and the second external connection electrode 5 B is filled in the cutout portion 19 . The first external connection electrode 4 B and the second external connection electrode 5 B are formed so as to protrude from the resin film 17 , and include a drawing portion 20 that is drawn inwardly of the substrate 2 along the surface of the resin film 17 . In the preferred embodiment, the first external connection electrode 4 B is formed so as to cover not only the surface of the first electrode film 4 A (the first pad 4 Ab) and the insulating film 8 exposed within the cutout portion 18 but also the upper end surface of the passivation film 9 on the side of one end portion of the substrate 2 . The three side surfaces other than the side surface on the inner side of the first external connection electrode 4 B are formed so as to be flush with the surface of the passivation film 9 covering the peripheral surface of the insulating film 8 on the side of one end portion of the substrate 2 .

Likewise, the second external connection electrode 5 B is formed so as to cover not only the surface of the second electrode film 5 A (the pad 5 Ab) and the insulating film 8 exposed within the cutout portion 19 but also the upper end surface of the passivation film 9 on the side of the other end portion of the substrate 2 . The three side surfaces other than the side surface on the inner side of the second external connection electrode 5 B are formed so as to be flush with the surface of the passivation film 9 covering the peripheral surface of the insulating film 8 on the side of the other end portion of the substrate 2 . The external connection electrodes 4 B and 5 B may be formed with a Ni/Pd/Au laminated film having a Ni film in contact with the electrode films 4 A and 5 A, a Pd film formed thereon, and an Au film formed thereon. The laminated film described above can be formed by a plating method.

The passivation film 16 and the resin film 17 coat, from the surface, the coil 3 , the insulating film 8 , the first electrode film 4 A, and the second electrode film 5 A in the coil formation region 10 C of the element formation surface 2 a , and function as a protective film to protect them. On the other hand, the passivation film 9 formed on the side surfaces 2 c of the substrate 2 and the outer peripheral surface of the insulating film 8 function as a protective film to protect the side surfaces 2 c of the substrate 2 and the outer peripheral surface of the insulating film 8 .

FIG. 40 is an electrical circuit diagram showing an electrical structure within the chip inductor. One end of the coil 3 (represented by a symbol L in FIG. 40 ) is connected to the first electrode 4 , and the other end of the coil 3 is connected to the second electrode 5 . In this way, the chip inductor functions as an inductor having a predetermined inductance.

As a parameter indicating the performance (quality) of the coil, the Q (Quality Factor) value of the coil is present. As the Q value is increased, its loss is decreased, and an excellent characteristic is provided as a high-frequency inductance.

The Q value of the coil 3 is represented by formula (1) below.

Q= 2π fL/R   (1)

In formula (1) above, f represents the frequency of a current flowing through the coil, L represents the inductance of the coil 3 , and R represents the internal resistance of the coil 3 .

In the arrangement of the first preferred embodiment of the second invention, in the substrate 2 , the coil formation trench 11 obtained by digging down from the element formation surface 2 a is formed, in plan view, in the shape of a spiral, the conductive member 51 is embedded within the coil formation trench 11 and thus the coil 3 is formed. Hence, it is possible to increase the cross-sectional area of the coil 3 (the cross-sectional area of the coil 3 perpendicular to the direction in which the coil 3 is extended in the spiral direction), and thus it is possible to decrease the internal resistance (R in formula (1) above) of the coil 3 . In this way, since the Q value of the coil 3 can be increased, it is possible to provide a high performance chip inductor.

The coil formation trench 11 is formed in the substrate 2 , the conductive member 51 is embedded within the coil formation trench 11 and thus it is possible to form the coil 3 , with the result that the coil 3 is easily manufactured. In this way, it is possible to provide a chip inductor that is easily manufactured.

Furthermore, on the element formation surface 2 a , which is one surface of the substrate 2 , both the external connection electrodes 4 B and 5 B of the first electrode 4 and the second electrode 5 are formed. Hence, as shown in FIG. 41 , the element formation surface 2 a is made to face a mounting substrate 91 , the external connection electrodes 4 B and 5 B are bonded on the mounting substrate 91 by a solder 92 and thus it is possible to form a circuit assembly in which the chip inductor 1 is surface-mounted on the mounting substrate 91 . In other words, it is possible to provide a flip-chip connection-type chip inductor 1 , and it is possible to connect the chip inductor 1 to the mounting substrate 91 by a face-down bonding in which the element formation surface 2 a is made to face the mounting substrate 91 and wireless bonding. In this way, it is possible to decrease the occupied space of the chip inductor 1 on the mounting substrate 91 . In particular, it is possible to realize a low profile chip inductor 1 on the mounting substrate 91 . In this way, it is possible to effectively utilize the space within the housing of a small-sized electronic device or the like and to contribute to high-density mounting and miniaturization.

FIGS. 42A to 42L are cross-sectional views for illustrating an example of the manufacturing step of the chip inductor, and show cut surfaces corresponding to FIG. 35 . FIGS. 43A to 43E are partially enlarged cross-sectional views showing the details of the manufacturing step of a coil, and show cut surfaces corresponding to FIG. 36 .

As shown in FIG. 42A , an original substrate (base substrate) 50 that is an original of the substrate main body 6 is prepared. On the surface of the original substrate 50 , the insulating film 7 such as a thermal oxide film or a CVD oxide film is formed. In the preferred embodiment, the insulating film 7 is a thermal oxide film. The surface of the insulating film 7 corresponds to the element formation surface 2 a of the substrate 2 .

FIG. 44 is a schematic plan view of part of the original substrate 50 in which the insulating film 7 is formed on the surface. As shown in FIG. 44 , in the element formation surface 2 a , chip inductor regions X corresponding to a plurality of chip inductors 1 are disposed in a matrix. Between the chip inductor regions X adjacent to each other, a boundary region Y is provided. The boundary region Y is a region in the shape of a band having a substantially constant width, extends in two directions perpendicular to each other and is formed in a lattice shape. After necessary steps are performed on the original substrate 50 in which the insulating film 7 is formed on the surface, the original substrate 50 is separated along the boundary region Y, and thus it is possible to obtain a plurality of chip inductors 1 .

The steps performed on the original substrate 50 in which the insulating film 7 is formed on the surface are as follows. First, as shown in FIG. 42A , by photolithography and etching, a part of the insulating film 7 that corresponds to a region to form the coil formation trench 11 is removed. In this way, in the insulating film 7 , a first trench part 11 a is formed. Then, a hard mask formed with the insulating film 7 is used, and thus the original substrate 50 is etched. In this way, as shown in FIGS. 42B and 43A , a second trench part 11 b is formed in the original substrate 50 . In this way, in the insulating film 7 and the original substrate 50 , the coil formation trench 11 formed with the first trench part 11 a and the second trench part 11 b is formed. The coil formation trench 11 may be formed with, for example, a so-called BOSCH process. The BOSCH process is a process that is used to make a hollow part in a MEMS (Micro Electro Mechanical System).

Then, as shown in FIGS. 42B and 43B , on the inner surface of the coil formation trench 11 , the insulating film (thermal oxide film) 12 is formed by a thermal oxidization method. Here, the surrounding wall (the side wall and the bottom wall) of the coil formation trench 11 (the second trench part 11 b ) in the original substrate 50 is thermally oxidized into an insulator portion (thermal oxide film) 30 having insulation. In FIG. 42B , the insulating film 12 is omitted but the insulator portion 30 is shown. In the preferred embodiment, the entire wall sandwiched by the coil formation trench 11 (the second trench part 11 b ) in the shape of a spiral in the original substrate 50 is formed into the thermal oxide film.

Then, for example, by a sputtering method, the barrier metal film 13 made of TiN is formed on the element formation surface 2 a including the interior of the coil formation trench 11 . In this way, then, as shown in FIG. 43C , the barrier metal film 13 is formed on the surfaces of the insulating film 12 and the insulating film 7 within the coil formation trench 11 , and the surface of the insulating film 7 outside the coil formation trench 11 . Thereafter, annealing processing is performed. Thereafter, as shown in FIGS. 42C and 43D , for example, by a CVD method, on the element formation surface 2 a including the interior of the coil formation trench 11 , the conductive member 51 formed of tungsten (W) is deposited.

Then, for example, by an etch back method, overall etching is performed on the conductive member 51 from its surface. The overall etching is continued until the surface of the conductive member 51 is flush with the surface of the insulating film 7 . In this way, as shown in FIGS. 42D and 43E , the conductive member 51 is embedded within the coil formation trench 11 while in contact with the barrier metal film 13 . By the conductive member 51 embedded within the coil formation trench 11 , the coil 3 in the shape of a spiral when seen in plan view is formed.

Then, as shown in FIG. 42E , on the insulating film 7 , the insulating film 8 formed with a USG (Undoped Silicate Glass) film or the like is formed so as to coat the insulating film 7 (the element formation surface 2 a ) and the coil 3 . The insulating film 8 is formed by, for example, a CVD method. Thereafter, by photolithography and etching, in regions of the insulating film 8 corresponding to one end portion and the other end portion of the coil 3 , the first contact hole 14 (see FIG. 37 ) and the second contact hole 15 (see FIG. 42E ) penetrating the insulating film 8 are respectively formed.

Then, for example, by sputtering, on the insulating film 8 including the interiors of the contact holes 14 and 15 , an electrode film forming the first electrode 4 and the second electrode 5 is formed. In the preferred embodiment, the electrode film made of Al is formed. Thereafter, by photolithography and etching, the electrode film is patterned, and thus as shown in FIG. 42F , the electrode film is separated into the first electrode film 4 A and the second electrode film 5 A.

Then, as shown in FIG. 42G , for example, by a CVD method, the passivation film 16 such as a nitride film is formed, and furthermore, polyimide is applied to form the resin film 17 . For example, polyimide to which photosensitivity is added is applied, and the polyimide is developed after exposure with a pattern corresponding to the cutout portions 18 and 19 . In this way, the resin film 17 having a cutout portion corresponding to the cutout portions 18 and 19 is formed. Thereafter, as necessary, heat treatment for curing the resin film is performed. Then, by dry etching using the resin film 17 as a mask, the cutout portions 18 and 19 are formed in the passivation film 16 .

Then, as shown in FIG. 42H , a resist mask 52 having an opening 52 a in a lattice shape matching with the boundary region Y (see FIG. 44 ) is formed. Plasma etching is performed via the resist mask 52 , and thus as shown in FIG. 42H , the original substrate 50 , the insulating film 7 , and the insulating film 8 are etched from the surface of the insulating film 8 to a predetermined depth. In this way, along the boundary region Y, a groove (scribe groove) 53 for cutting is formed.

Then, the resist mask 52 is peeled off. Thereafter, as shown in FIG. 42I , for example, by a CVD method, an insulating film 54 formed with a nitride film etc., serving as the material for the passivation film 9 is formed over the entire region of the surface of the original substrate 50 . Here, the insulating film 54 is also formed over the entire region of the inner surface (the side wall surface and the bottom wall surface) of the groove 53 .

Then, as shown in FIG. 42J , the insulating film 54 is selectively etched. Specifically, a part of the insulating film 54 other than the insulating film 54 (the passivation film 9 ) on the side wall surface of the groove 53 is removed. In this way, a part of the electrode films 4 A and 5 A that is not covered by the passivation film 16 and the resin film 17 is exposed. The insulating film 54 on the bottom surface of the groove 53 is removed.

Then, as shown in FIG. 42K , on the first electrode film 4 A (the first pad 4 Ab) and the second electrode film 5 A (the second pad 5 Ab) exposed from the cutout portions 18 and 19 , for example, by plating (preferably, electroless plating), plating growth is performed in the following order: for example, Ni, Pd, and Au. In this way, the first external connection electrode 4 B and the second external connection electrode 5 B are formed.

Thereafter, by a DBG (Dicing Before Grinding) method, a plurality of chip inductor regions X are divided into pieces. Specifically, as shown in FIG. 42L , first, on the side of the surface of the original substrate 50 (the side of the external connection electrode), a supporting tape 71 having an adhesive surface 72 is adhered. Then, the original substrate 50 is polished from the rear surface to the bottom surface of the groove 53 . In this way, the chip inductor regions X are separated into individual chip inductors 1 .

FIGS. 45A to 45D are cross-sectional views schematically showing the recovery step of the chip inductor 1 after the step of FIG. 42L .

FIG. 45A shows a state where the separated chip inductors 1 are held by the supporting tape 71 . In this state, as shown in FIG. 45B , a thermally foaming sheet 73 is adhered to the rear surface 2 b of each of the chip inductors 1 . The thermally foaming sheet 73 includes a sheet main body 74 in the shape of a sheet and a large number of foaming particles 75 kneaded into the sheet main body 74 .

The adhesive force of the sheet main body 74 is greater than that of the adhesive surface 72 of the supporting tape 71 . Hence, after the thermally foaming sheet 73 is adhered to the rear surface 2 b of each of the chip inductors 1 , as shown in FIG. 45C , the supporting tape 71 is peeled off from each chip inductor 1 , and the chip inductor 1 is transferred to the thermally foaming sheet 73 . Here, since the adhesive property of the adhesive surface 72 is lowered by the application of ultraviolet rays to the supporting tape 71 (see dotted arrows in FIG. 45B ), the supporting tape 71 is easily peeled off from each chip inductor 1 .

Then, the thermally foaming sheet 73 is heated. In this way, as shown in FIG. 45D , in the thermally foaming sheet 73 , the foaming particles 75 within the sheet main body 74 are foamed and are expanded out of the surface of the sheet main body 74 . Consequently, the contact area between the thermally foaming sheet 73 and the rear surface 2 b of each chip inductor 1 is decreased, and thus all the chip inductors 1 are naturally peeled off from the thermally foaming sheet 73 . The chip inductors 1 recovered in this way are mounted on the mounting substrate 91 (see FIG. 41 ), and are stored in a storage space formed by an embossed carrier tape (not shown). In this case, as compared with a case where the chip inductors 1 are peeled off from the supporting tape 71 or the thermally foaming sheet 73 one by one, it is possible to reduce the processing time. As a matter of course, with a plurality of chip inductors 1 held by the supporting tape 71 (see FIG. 45A ), without use of the thermally foaming sheet 73 , the chip inductors 1 may be directly peeled off from the supporting tape 71 by a predetermined number of pieces.

FIGS. 46A to 46C are schematic cross-sectional views showing another example of the recovery step of the chip inductor after the step of FIG. 42L .

As with FIG. 45A , FIG. 46A shows a state where a plurality of chip inductors 1 separated into pieces are held by the supporting tape 71 . In this state, as shown in FIG. 46B , a transfer tape 77 is adhered to the rear surface 2 b of each chip inductor 1 . The transfer tape 77 has an adhesive force greater than that of the adhesive surface 72 of the supporting tape 71 . Hence, as shown in FIG. 46C , after the transfer tape 77 is adhered to each chip inductor 1 , the supporting tape 71 is peeled off from each chip inductor 1 . Here, as described previously, ultraviolet rays (see dotted arrows in FIG. 46B ) may be applied to the supporting tape 71 so that the adhesive property of the adhesive surface 72 is lowered.

The frames 78 of the recovery device (not shown) are adhered to both ends of the transfer tape 77 . The frames 78 on both sides can be moved either in a direction in which they approach each other or in a direction in which they are separated. After the supporting tape 71 is peeled off from each chip inductor 1 , the frames 78 on both sides are moved in the direction in which they are separated, and thus the transfer tape 77 is extended so as to become thin. In this way, the adhesive force of the transfer tape 77 is lowered, and thus each chip inductor 1 is easily peeled off from the transfer tape 77 . When in this state, the suction nozzle 76 of the conveying device (not shown) is directed to the side of the element formation surface 2 a of the chip inductor 1 , the chip inductor 1 is peeled off from the transfer tape 77 by the adhesive force produced by the conveying device and is sucked by the suction nozzle 76 . Here, the chip inductor 1 is pushed up by a projection 79 shown in FIG. 46C from the side opposite to the suction nozzle 76 through the transfer tape 77 to the side of the suction nozzle 76 , and thus the chip inductor 1 can be smoothly peeled off from the transfer tape 77 . The chip inductor 1 recovered in this way is conveyed by the conveying device while being sucked by the anchor portion 76 .

FIGS. 47A and 47B are cross-sectional views showing a modification example of the external connection electrode of the chip inductor 1 . FIG. 47A shows a cut surface corresponding to FIG. 35 , and FIG. 47B shows a cut surface corresponding to FIG. 38 . In FIGS. 47A and 47B , the portions corresponding to the portions of FIGS. 35 and 38 described previously are provided with the same symbols of FIGS. 35 and 38 .

The first external connection electrode 4 B is filled in one cutout portion 18 in the passivation film 16 and the resin film 17 , and the second external connection electrode 5 B is filled in the other cutout portion 19 .

The first external connection electrode 4 B is formed so as to cover the upper portion of the passivation film 9 on the side of one end portion of the substrate 2 and to straddle, from the peripheral portion of the surface of the insulating film 8 , the surface of the passivation film 9 covering the three side surfaces 2 c on the side of one end portion of the substrate 2 . In other words, the first external connection electrode 4 B is formed so as to cover not only the surface of the first electrode film 4 A (the pad 4 Ab) and the insulating film 8 exposed within the cutout portion 18 but also the passivation film 9 on the three side surfaces 2 c of the substrate 2 .

Likewise, the second external connection electrode 5 B is formed so as to cover the upper portion of the passivation film 9 on the side of the other end portion of the substrate 2 and to straddle, from the peripheral portion of the surface of the insulating film 8 , the surface of the passivation film 9 covering the three side surfaces 2 c on the side of the other end portion of the substrate 2 . In other words, the second external connection electrode 5 B is formed so as to cover not only the surface of the second electrode film 5 A (the pad 5 Ab) and the insulating film 8 exposed within the cutout portion 19 but also the passivation film 9 on the three side surfaces 2 c on the side of the other end portion of the substrate 2 .

As described above, in the chip inductor 1 , the first external connection electrode 4 B is formed so as to cover the three side surfaces 2 c on the side of one end portion of the substrate 2 , and the second external connection electrode 5 B is formed so as to cover the three side surfaces 2 c on the side of the other end portion of the substrate 2 . In other words, the external connection electrodes 4 B and 5 B are formed not only on the element formation surface 2 a on the substrate 2 but also on the side surfaces 2 c of the substrate 2 . In this way, in the form shown in FIG. 41 described previously, when the external connection electrodes 4 B and 5 B of the chip inductor 1 are soldered to the mounting substrate, it is possible to increase the bonding area between the external connection electrodes 4 B and 5 B, and the mounting substrate. Consequently, it is possible to enhance the bonding strength of the external connection electrodes 4 B and 5 B on the mounting substrate.

FIG. 48A is a diagram showing a modification example of the conductive member embedded within the coil formation trench 11 , and is a partially enlarged cross-sectional view corresponding to FIG. 36 . FIG. 48B is a partially enlarged cross-sectional view of FIG. 48A .

As shown in FIG. 48A , the width W 2 of the coil formation trench 11 may be, for example, 10 μm or less, and more specifically, may be 3 μm or more and 9 μm or less. The depth D of the coil formation trench 11 may be, for example, 10 μm or more, and more specifically, may be 30 μm or more and 80 μm or less.

As shown in FIG. 48A , within the coil formation trench 11 , the conductive member 51 is embedded. The conductive member 51 includes first, second, and third conductor layers 51 a , 51 b and 51 c . The first and second conductor layers 51 a and 51 b are partitioned by a crystal boundary portion B 1 . The second and third conductor layers 51 b and 51 c are partitioned by a crystal boundary portion B 2 .

Although in the preferred embodiment, an example where the conductive member 51 is partitioned by the two crystal boundary portions B 1 and B 2 into the three conductor layers (the first to third conductor layers 51 a to 51 c ) will be described, the conductive member 51 may be partitioned by one crystal boundary portion into two conductor layers. The conductive member 51 may be partitioned by three or more crystal boundary portions into four or more conductor layers.

As shown in FIGS. 48A and 48B , the conductive member 51 further includes a first seed layer 13 a that intervenes between the coil formation trench 11 and the first conductor layer 51 a , a second seed layer 13 b that intervenes between the first and second conductor layers 51 a and 51 b and a third seed layer 13 c that intervenes between the second and third conductor layers 51 b and 51 c.

In a modification example of the conductive member, the crystal boundary portion B 1 is defined by the second seed layer 13 b intervening between the first and second conductor layers 51 a and 51 b . The crystal boundary portion B 2 is defined by the third seed layer 13 c intervening between the second and third conductor layers 51 b and 51 c . In other words, the crystal boundary portion B 1 includes the crystal boundary surface formed by bringing the first and second conductor layers 51 a and 51 b into contact with the second seed layer 13 b . The crystal boundary portion B 2 includes the crystal boundary surface formed by bringing the second and third conductor layers 51 b and 51 c into contact with the third seed layer 13 c.

The first seed layer 13 a is formed such that the front surface and the rear surface (the surface on the side of the substrate 2 ) are along the inner surface (the side portion and the bottom portion) of the coil formation trench 11 . More specifically, the first seed layer 13 a is formed such that within the coil formation trench 11 , the front surface and the rear surface (the surface on the side of the substrate 2 ) are along the surface of the insulating film 12 and the surface of the insulating film 7 . On the first seed layer 13 a , the first conductor layer 51 a is formed.

The first conductor layer 51 a is formed such that the front surface and the rear surface (the surface on the side of the substrate 2 ) are along the surface of the first seed layer 13 a . On the first conductor layer 51 a , the second seed layer 13 b is formed. The second seed layer 13 b is formed such that the front surface and the rear surface (the surface on the side of the substrate 2 ) are along the surface of the first conductor layer 51 a . In other words, the second seed layer 13 b is formed along the inner surface (the side portion and the bottom portion) of the coil formation trench 11 in the shape of the letter U in cross section, and partitions the first conductor layer 51 a into a concave shape in cross section. On the second seed layer 13 b , the second conductor layer 51 b is formed.

The second conductor layer 51 b is formed such that the front surface and the rear surface (the surface on the side of the substrate 2 ) are along the surface of the second seed layer 13 b . On the second conductor layer 51 b , the third seed layer 13 c is formed. The third seed layer 13 c is formed such that the front surface and the rear surface (the surface on the side of the substrate 2 ) are along the surface of the second conductor layer 51 b . In other words, the third seed layer 13 c is formed along the side portion and the bottom portion of the coil formation trench 11 in the shape of the letter U in cross section, and partitions the second conductor layer 51 b into a concave shape in cross section. On the third seed layer 13 c , the third conductor layer 51 c is formed. The third conductor layer 51 c is formed such that the groove in the recess shape in cross section partitioned by the third seed layer 13 c is refilled therein.

The first to third conductor layers 51 a to 51 c and the first to third seed layers 13 a to 13 c are formed of different conductive materials. The first to third conductor layers 51 a to 51 c are formed of, for example, tungsten (W) or aluminum (Al). On the other hand, the first to third seed layers 13 a to 13 c are formed of, for example, titanium nitride (TiN).

Each thickness W 3 of the first to third conductor layers 51 a to 51 c is, for example, 1 μm or less, and more specifically is 0.1 to 0.6 μm. Each thickness W 4 of the first to third seed layers 13 a to 13 c is, for example, 500 angstroms or less, and more specifically is 300 to 500 angstroms.

FIGS. 49A to 49K are partially enlarged cross-sectional views showing a step of embedding the conductive member 51 of FIG. 48A in the coil formation trench 11 , and show cut surfaces corresponding to FIG. 36A . FIG. 49A shows a state where the step of FIG. 42A described previously has been performed, and FIG. 49B shows a state where the step of FIG. 42B described previously has been performed.

After the step of FIG. 49B ( FIG. 42B ), in order for the conductive member 51 to be embedded in the coil formation trench 11 , first, as shown in FIG. 49C , by a CVD method or a LTS (Long Throw Sputtering) method, the first seed layer 13 a made of titanium nitride is formed so as to cover the surface of the original substrate 50 . More specifically, the first seed layer 13 a is formed such that the front surface and the rear surface (the surface on the side of the original substrate 50 ) are along the inner surface (the side portion and the bottom portion) of the coil formation trench 11 and the surface of the insulating film 7 . The first seed layer 13 a is formed such that its thickness is, for example, 300 to 500 angstroms (in this step, 400 angstroms).

Then, as shown in FIG. 49D , by a CVD method in which the temperature conditions are 1000° C. or less (in this step, about 800° C.), the first conductor layer 51 a made of tungsten is formed so as to cover the surface of the original substrate 50 . More specifically, the first conductor layer 51 a is formed such that the front surface and the rear surface (the surface on the side of the original substrate 50 ) are along the surface of the first seed layer 13 a . The first conductor layer 51 a is formed such that its thickness is, for example, 1 μm or less (in this step, 0.6 μm).

Then, as shown in FIG. 49E , by etch back, a unnecessary part of the first conductor layer 51 a formed in a region outside the coil formation trench 11 (the first trench part 11 a and the second trench part 11 b ) is removed. In this way, the first conductor layer 51 a is embedded in the coil formation trench 11 . The first seed layer 13 a is exposed on the insulating film 7 outside the coil formation trench 11 .

Then, as shown in FIG. 49F , by a CVD method or a LTS method, the second seed layer 13 b made of titanium nitride is formed so as to cover the surface of the original substrate 50 . More specifically, the second seed layer 13 b is formed such that the front surface and the rear surface (the surface on the side of the original substrate 50 ) are along the surface of the first conductor layer 51 a and the surface of the first seed layer 13 a formed on the insulating film 7 . The second seed layer 13 b is formed such that its thickness is, for example, 300 to 500 angstroms (in this step, 400 angstroms).

Then, as shown in FIG. 49G , by a CVD method in which the temperature conditions are 1000° C. or less (in this step, about 800° C.), the second conductor layer 51 b made of tungsten is formed so as to cover the surface of the original substrate 50 . More specifically, the second conductor layer 51 b is formed such that the front surface and the rear surface (the surface on the side of the original substrate 50 ) are along the surface of the second seed layer 13 b . The second conductor layer 51 b is formed such that its thickness is, for example, 4 μm or less (in this step, 0.6 μm).

Then, as shown in FIG. 49H , by etch back, a unnecessary part of the second conductor layer 51 b formed in the region outside the coil formation trench 11 (the first trench part 11 a and the second trench part 11 b ) is removed. In this way, the second conductor layer 51 b is embedded in the coil formation trench 11 . On the insulating film 7 outside the coil formation trench 11 , laminated members of the first seed layer 13 a and the second seed layer 13 b are left.

Then, as shown in FIG. 49I , by a CVD method or a LTS method, the third seed layer 13 c made of titanium nitride is formed so as to cover the surface of the original substrate 50 . More specifically, the third seed layer 13 c is formed such that the front surface and the rear surface (the surface on the side of the original substrate 50 ) are along the surface of the second conductor layer 51 b exposed from the coil formation trench 11 and the surface of the second seed layer 13 b formed on the insulating film 7 . The third seed layer 13 c is formed such that its thickness is, for example, 300 to 500 angstroms (in this step, 400 angstroms).

Then, as shown in FIG. 49J , by a CVD method in which the temperature conditions are 1000° C. or less (in this step, about 800° C.), the third conductor layer 51 c made of tungsten is formed so as to cover the surface of the original substrate 50 . More specifically, the third conductor layer 51 c is formed such that the groove in a concave shape in cross section partitioned by the third seed layer 13 c is refilled therein. The third conductor layer 51 c is formed such that its thickness is, for example, 1 μm or less (in this step, 0.6 μm).

Then, as shown in FIG. 49K , by etch back, a unnecessary part of the third conductor layer 51 c formed in the region outside the coil formation trench 11 (the first trench part 11 a and the second trench part 11 b ) is removed. In this way, the third conductor layer 51 c is embedded in the coil formation trench 11 . On the insulating film 7 outside the coil formation trench 11 , a laminated member of the first to third seed layers 13 a , 13 b , and 13 c made of titanium nitride is left.

Thereafter, for example, by etching, the laminated member of the first to third seed layers 13 a , 13 b , and 13 c formed on the insulating film 7 is removed, and as shown in FIG. 42C , it is possible to obtain the arrangement in which the conductive member 51 is embedded in the coil formation trench 11 .

It is considered that as in the first preferred embodiment of the second invention described above, for example, by a CVD method in which the temperature conditions are 1000° C. or less, in one step, tungsten is embedded in the coil formation trench 11 to form the conductive member 51 . In this case, the surface of the original substrate 50 is covered with a relatively thick conductor film. The original substrate 50 is cooled after the conductive member 51 is embedded in the coil formation trench 11 .

However, the conductor film (the conductive member 51 ) has a thermal expansion rate different from that of the original substrate 50 , and the cooling rate of the conductor film (the conductive member 51 ) is higher than that of the original substrate 50 . Hence, at the time of cooling, such a stress that the original substrate 50 is warped may be produced by the volume shrinkage of the relatively thick conductor film. The warp of the original substrate 50 refers to a state where a difference in height (for example, about 3 mm) is produced between the center portion and the edge portion of the original substrate 50 . Each occurrence of the warp of the original substrate 50 described above may cause a suction/adherence failure or the like when a suction device which sucks the main surface (for example, the rear surface) of the original substrate 50 to convey the original substrate 50 is used or when as shown in FIG. 42L described previously, the supporting tape 71 is adhered to the original substrate 50 etc. The occurrence of a suction/adherence failure or the like lowers the yield.

By contrast, by the method shown in FIGS. 49A to 49K , after the formation of the coil formation trench 11 in the original substrate 50 , the conductor layers (the first to third conductor layers 51 a , 51 b , and 51 c ) are embedded several times. Hence, the stress that is originally to be received by the original substrate 50 in one step is divided into a plurality of times.

Each thickness of the first to third conductor layers 51 a , 51 b , and 51 c is small as compared with the case where in one step, the conductive member 51 is embedded in the coil formation trench 11 . The first to third conductor layers 51 a , 51 b , and 51 c formed on the original substrate 50 outside the coil formation trench 11 and more specifically on the insulating film 7 outside the coil formation trench 11 are removed each time. Hence, on the original substrate 50 outside the coil formation trench 11 , the thickness of the first to third conductor layers 51 a , 51 b , and 51 c is not increased. In this way, it is possible to reduce the individual stress applied by the first to third conductor layers 51 a , 51 b , and 51 c to the original substrate 50 .

Furthermore, according to the method shown in FIGS. 49A to 49K , by a CVD method in which the temperature conditions are 1000° C. or less (in the modification example, about 800° C.), the first to third conductor layers 51 a , 51 b , and 51 c made of tungsten are formed such that the individual thickness is 1 μm or less (in the modification example, 0.6 μm). Each stress of the first to third conductor layers 51 a , 51 b , and 51 c is increased as each thickness of the first to third conductor layers 51 a , 51 b , and 51 c is increased (for example, thickness>1 μm). Hence, the first to third conductor layers 51 a , 51 b , and 51 c are formed to have a thickness of 1 μm or less, and thus it is possible to effectively reduce each stress of the first to third conductor layers 51 a , 51 b and 51 c.

In this way, it is possible to effectively reduce the occurrence of the warp of the original substrate 50 . Consequently, it is possible to effectively reduce the occurrence of a suction/adherence failure or the like such as when a suction device which sucks and processes the original substrate 50 is used or when as shown in FIG. 42L described previously, the supporting tape 71 is adhered, with the result that it is possible to enhance the yield of the chip inductor 1 .

Since in the method shown in FIGS. 49A to 49K , it is possible to effectively reduce the occurrence of the warp of the original substrate 50 , it is possible to effectively enhance the film formation property of the first electrode 4 , the second electrode 5 , the insulating film 7 , the insulating film 8 , the passivation film 16 , and the resin film 17 . In other words, it is possible to effectively reduce the film formation failure or the like of the first electrode 4 , the second electrode 5 , the insulating film 7 , the insulating film 8 , the passivation film 16 and the resin film 17 . It is also possible to effectively enhance the embedding of the conductive member 51 in the coil formation trench 11 .

In the method shown in FIGS. 49A to 49K , on the first to third seed layers 13 a to 13 c , the first to third conductor layers 51 a to 51 c are formed. Hence, the first to third conductor layers 51 a to 51 c can be satisfactorily embedded within the coil formation trench 11 .

FIG. 50A is a partially cut perspective view of a chip inductor (chip inductor according to a preferred embodiment of the third invention) according to the second preferred embodiment of the second invention. FIG. 50B is a perspective view showing a coil formed within the chip inductor.

The chip inductor 1 A is a minute chip part and is formed in the shape of a rectangular parallelepiped. The planar shape of the chip inductor 1 A may be rectangular, the length L in the longitudinal direction may be about 0.4 mm and the length W in the lateral direction may be about 0.2 mm. The thickness T of the entire chip inductor 1 A may be about 0.15 mm.

The chip inductor 1 A includes a substrate 2 , a coil 3 that is formed within the substrate 2 , a first electrode 4 that is connected to one end portion of the coil 3 and a second electrode 5 that is connected to the other end portion of the coil 3 .

FIG. 51A is a plan view showing the appearance of the chip inductor when seen from the side of the electrode, FIG. 51B is a plan view showing the internal structure of the chip inductor, FIG. 52 is a cross-sectional view taken along line LII-LII in FIG. 51B , FIG. 53 is a partially enlarged cross-sectional view of FIG. 52 , FIG. 54 is a cross-sectional view taken along line LIV-LIV in FIG. 51B and FIG. 55 is a cross-sectional view taken along line LV-LV in FIG. 51B . FIG. 56 is a partially enlarged cross-sectional view of FIG. 55 . FIG. 57 is a plan view showing a structure of the surface of a substrate by removing an arrangement formed on the surface of the substrate.

The substrate 2 is formed in the shape of a rectangular parallelepiped, and includes a pair of main surfaces 2 a and 2 b and four side surfaces 2 c . One (the main surface 2 a on the upper surface side in FIG. 50A ) of the pair of main surfaces 2 a and 2 b is an element formation surface. In the following description, the main surface 2 a is referred to as an “element formation surface 2 a ,” and the main surface 2 b on the side opposite to the element formation surface 2 a is referred to as a “rear surface 2 b .” In the preferred embodiment, the substrate 2 is formed with a substrate main body 6 and an insulating film 7 formed on the surface thereof, and the surface of the insulating film 7 on the side opposite to the side of the substrate main body 6 is the element formation surface 2 a . The element formation surface 2 a is formed in the shape of a rectangle in plan view when seen in a normal direction perpendicular to the element formation surface 2 a . The surface (element formation surface 2 a ) of the substrate 2 is covered by an insulating film 8 . The four side surfaces 2 c of the substrate 2 and the outer peripheral surface of the insulating film 8 are covered by a passivation film 9 such as a nitride film.

With reference to FIG. 51B , in the element formation surface 2 a , a first electrode formation region 10 A for the formation of the first electrode 4 is provided at one end portion thereof, and a second electrode formation region 10 B for the formation of the second electrode 5 is provided at the other end portion. These regions 10 A and 10 B are rectangular in plan view. In the element formation surface 2 a between the first electrode formation region 10 A and the second electrode formation region 10 B, a coil formation region 10 C is provided. In the preferred embodiment, the coil formation region 10 C is formed in the shape of a rectangle.

In the first electrode formation region 10 A, the external connection electrode (first external connection electrode) 4 B of the first electrode 4 is disposed, and in the second electrode formation region 10 B, the external connection electrode (second external connection electrode) 5 B of the second electrode 5 is disposed. The first external connection electrode 4 B is rectangular in plan view, and covers the entire region of the first electrode formation region 10 A. The second external connection electrode 5 B is rectangular in plan view, and covers the entire region of the second electrode formation region 10 B.

In the surface of one (in the preferred embodiment, the first external connection electrode 4 B) of the first external connection electrode 4 B and the second external connection electrode 5 B, a plurality of concave portions 84 are formed. The plurality of concave portions 84 are formed, in plan view, in the shape of a straight line extending in the longitudinal direction of the substrate 2 , and are formed at an interval in the lateral direction of the substrate 2 . The cross-sectional shape of the concave portion 84 is the shape of the letter V. In the surface of the other external connection electrode (in the preferred embodiment, the second external connection electrode 5 B), the concave portions 84 are not formed.

In the substrate 2 , a coil formation trench 11 is formed by digging down, in the coil formation region 10 C, to a predetermined depth from the element formation surface 2 a . The coil formation trench 11 is formed, in plan view, in the shape of a spiral. In the preferred embodiment, the coil formation trench 11 is formed, in plan view, in the shape of a quadrilateral spiral, and has a plurality of rectilinear portions parallel to the side surfaces 2 c of the substrate 2 . The cross section (cross section in a direction perpendicular to a direction in which the coil formation trench 11 is extended in the spiral direction) of the coil formation trench 11 is formed in the shape of a rectangle which is long in the direction of the thickness of the substrate 2 . For example, the width of the coil formation trench 11 may be 1 μm or more and 3 μm or less. For example, the depth of the coil formation trench 11 may be 10 μm or more and 82 μm or less. The depth of the coil formation trench 11 is preferably 10 μm or more so that the internal resistance of the coil 3 formed within the coil formation trench 11 is decreased.

Furthermore, in a region (the first electrode formation region 10 A) of the element formation surface 2 a opposite the first external connection electrode 4 B, in the substrate 2 , a plurality of electrode-side trenches (concave portion formation trenches) 21 are formed by digging down from the element formation surface 2 a to a predetermined depth. The plurality of electrode-side trenches 21 are formed in positions opposite the plurality of concave portions 84 . Hence, the plurality of electrode-side trenches 21 are formed, in plan view, in the shape of a straight line extending in the longitudinal direction of the substrate 2 , and are formed at an interval in the lateral direction of the substrate 2 . The cross section of the electrode-side trench 21 is the shape of a rectangle that is long in the direction of the thickness of the substrate 2 . In the preferred embodiment, the width of the electrode-side trench 21 is narrower than that of the coil formation trench 11 . The depth of the electrode-side trench 21 may be the same as that of the coil formation trench 11 or may be shallower that of the coil formation trench 11 . In the preferred embodiment, the depth of the electrode-side trench 21 is the same as that of the coil formation trench 11 .

As shown in FIG. 53 , the coil formation trench 11 is formed with a first trench part 11 a that is formed in the insulating film 7 and a second trench part 11 b that is formed in the substrate main body 6 and that communicates with the first trench part 11 a . On the inner surface of the coil formation trench 11 (the second trench part 11 b ) in the substrate main body 6 , an insulating film 12 formed with an oxide film or the like is formed. On the surface of the insulating film 12 within the coil formation trench 11 (the second trench part 11 b ) and on the inner surface of the coil formation trench 11 (the first trench part 11 a ) in the insulating film 7 , a barrier metal film 13 is formed. The barrier metal film 13 is formed of, for example, TiN. The thickness of the barrier metal film 13 is about 400 to 500 angstroms.

Within the coil formation trench 11 , a conductive member 51 is embedded while being in contact with the barrier metal film 13 . In the preferred embodiment, the conductive member 51 is formed of tungsten (W). The coil 3 is formed with the conductive member 51 embedded within the coil formation trench 11 . Hence, the coil 3 is formed, in plan view, in the shape of a spiral (in the shape of a quadrilateral spiral) of the same pattern as the coil formation trench 11 . Specifically, the coil 3 includes a plurality of plate-shaped parts parallel to the side surfaces 2 c of the substrate 2 .

As shown in FIG. 56 , the electrode-side trench 21 is formed with a first trench part 21 a that is formed in the insulating film 7 and a second trench part 21 b that is formed in the substrate main body 6 and that communicates with the first trench part 21 a . On the inner surface of the electrode-side trenches 21 (the second trench part 21 b ) in the substrate main body 6 , an insulating film 12 formed with an oxide film or the like is formed. In the preferred embodiment, the insulating film 12 formed on the inner surface of the electrode-side trenches 21 (the second trench part 21 b ) in the substrate main body 6 fills within the second trench part 21 b.

On the inner surface of each electrode-side trench 21 (the first trench part 21 a ) in the insulating film 7 , the barrier metal film 13 is formed. Within the electrode-side trench 21 (the first trench part 21 a ) in the insulating film 7 , the conductive member 51 is embedded while being in contact with the barrier metal film 13 . In the surface of the conductive member 51 within the electrode-side trench 21 , a concave portion (first underlying concave portion) 81 is formed. In other words, in a region of the element formation surface 2 a opposite the first external connection electrode 4 B, a plurality of concave portion 81 are formed. The plurality of concave portions 81 are formed in positions opposite the plurality of concave portions 84 of the first external connection electrode 4 B. Hence, the plurality of concave portions 81 are formed, in plan view, in the shape of a straight line extending in the longitudinal direction of the substrate 2 , and are formed at an interval in the lateral direction of the substrate 2 . The cross-sectional shape of the concave portion 81 is the shape of the letter V. As will be described later, the concave portions 81 are formed due to the electrode-side trenches 21 formed in the substrate 2 .

In the preferred embodiment, the insulating film 12 formed on the inner surfaces of the coil formation trench 11 and the electrode-side trench 21 is formed with a thermal oxide film (SiO 2 ). When the thermal oxide film is formed on the inner surface of the trenches 11 and 21 , the surrounding wall (the side wall and the bottom wall) of the trenches 11 and 21 in the substrate main body 6 is thermally oxidized into an insulator portion (thermal oxide film) 30 having insulation. In the preferred embodiment, an example is described where the entire wall sandwiched by the coil formation trench 11 (the second trench part 11 b ) in the shape of a spiral in the substrate main body 6 and the entire wall between the adjacent two electrode-side trenches 21 (the second trench parts 21 b ) are thermal oxide films.

On the element formation surface 2 a (the surface of the insulating film 7 ) of the substrate 2 , the insulating film 8 is formed so as to coat the element formation surface 2 a and the conductive member 51 . The insulating film 8 is formed, in plan view, in the shape of a rectangle matching with the element formation surface 2 a . The insulating film 8 is formed with, for example, a USG (Undoped Silicate Glass) film. In the insulating film 8 , a first contact hole 14 (see FIGS. 51B and 54 ) that exposes one end portion (outer peripheral side end portion) of the coil 3 and a second contact hole 15 (see FIGS. 51B and 52 ) that exposes the other end portion (inner peripheral side end portion) of the coil 3 are formed.

Furthermore, in the surface of the insulating film 8 , as shown in FIGS. 55 and 56 , in a region opposite the first external connection electrode 4 B, a plurality of concave portions (second underlying concave portions) 82 are formed. The plurality of concave portions 82 are formed in positions opposite the plurality of concave portions 84 (concave portions 81 ). Hence, the concave portions 82 are formed, in plan view, in the shape of a straight line extending in the longitudinal direction of the substrate 2 , and are formed at an interval in the lateral direction of the substrate 2 . The cross-sectional shape of the concave portion 82 is the shape of the letter V. As will be described later, the concave portions 82 are formed due to the concave portion 81 in the surface (the element formation surface 2 a ) of the substrate 2 , which is its underlying layer. As described previously, in the side surfaces 2 c of the substrate 2 and the outer peripheral surface of the insulating film 8 , the passivation film 9 formed with a nitride film or the like is formed.

On the surface of the insulating film 8 , the first electrode 4 and the second electrode 5 are formed. The first electrode 4 includes a first electrode film 4 A that is formed on the surface of the insulating film 8 and a first external connection electrode 4 B that is bonded to the first electrode film 4 A. As shown in FIG. 51B , the first electrode film 4 A includes a drawing electrode 4 Aa that is connected to one end portion of the coil 3 and a first pad 4 Ab that is formed integrally with the drawing electrode 4 Aa. The first pad 4 Ab is formed to be rectangular at one end portion of the element formation surface 2 a . The first external connection electrode 4 B is connected to the first pad 4 Ab. As shown in FIGS. 51B and 54 , the drawing electrode 4 Aa enters the first contact hole 14 from the surface of the insulating film 8 , and is connected to one end portion of the coil 3 within the first contact hole 14 . The drawing electrode 4 Aa is formed straight along a straight line that passes above one end portion of the coil 3 to reach the first pad 4 Ab.

By extending one end portion of the coil formation trench 11 to a position below the first pad 4 Ab, one end portion of the coil 3 may be located in a position below the first pad 4 Ab. In this way, since the first contact hole 14 can be formed in a position below the first pad 4 Ab, one end portion of the coil 3 can be connected to the first pad 4 Ab. In this case, since the first electrode film 4 A can be formed with only the first pad 4 Ab, the drawing electrode 4 Aa is not needed.

In the surface of the first pad 4 Ab, as shown in FIGS. 55 and 56 , a plurality of concave portions (third underlying concave portions) 83 are formed. The plurality of concave portions 83 are formed in positions opposite the concave portions 84 (the concave portions 82 ). Hence, the plurality of concave portions 83 are formed, in plan view, in the shape of a straight line extending in the longitudinal direction of the substrate 2 , and are formed at an interval in the lateral direction of the substrate 2 . The cross-sectional shape of the concave portion 83 is the shape of the letter V. The concave portions 83 are formed due to the concave portion 82 in the surface of the insulating film 8 , which is its underlying layer.

The second electrode 5 includes a second electrode film 5 A that is formed on the surface of the insulating film 8 and a second external connection electrode 5 B that is bonded to the second electrode film 5 A. As shown in FIG. 51B , the second electrode film 5 A includes a drawing electrode 5 Aa that is connected to the other end portion of the coil 3 and a second pad 5 Ab that is formed integrally with the drawing electrode 5 Aa. The second pad 5 Ab is formed to be rectangular at the other end portion of the element formation surface 2 a . The second external connection electrode 5 B is connected to the second pad 5 Ab. As shown in FIGS. 51B and 52 , the drawing electrode 5 Aa enters the second contact hole 15 from the surface of the insulating film 8 , and is connected to the other end portion of the coil 3 within the second contact hole 15 . The drawing electrode 5 Aa is formed straight along a straight line that passes above the other end portion of the coil 3 to reach the second pad 5 Ab. In the preferred embodiment, as the electrode films 4 A and 5 A, Al films are used.

The first electrode film 4 A and the second electrode film 5 A are covered by a passivation film 16 formed with a nitride film or the like, and furthermore, on the passivation film 16 , a resin film 17 such as polyimide is formed. In the passivation film 16 and the resin film 17 , two cutout portions 18 and 19 are formed that respectively expose a region other than an edge portion on the inner side of the surface of the first pad 4 Ab of the first electrode film 4 A and a region other than an edge portion on the inner side of the surface of the second pad 5 Ab of the second electrode film 5 A. In other words, the passivation film 16 and the resin film 17 are formed, in plan view, in a region corresponding to the coil formation region 10 C of the element formation surface 2 a , and cover the insulating film 8 , the edge portion on the inner side of the surface of the first pad 4 Ab, and the edge portion on the inner side of the surface of the second pad 5 Ab.

The first external connection electrode 4 B fills the cutout portion 18 , and the second external connection electrode 5 B fills the cutout portion 19 . The first external connection electrode 4 B and the second external connection electrode 5 B are formed so as to protrude from the resin film 17 , and include a drawing portion 20 that is drawn inwardly of the substrate 2 along the surface of the resin film 17 . In the preferred embodiment, the first external connection electrode 4 B is formed so as to cover not only the surface of the first electrode film 4 A (the first pad 4 Ab) and the insulating film 8 exposed within the cutout portion 18 but also the upper end surface of the passivation film 9 on the side of one end portion of the substrate 2 . The three side surfaces other than the side surface on the inner side of the first external connection electrode 4 B are formed so as to be flush with the surface of the passivation film 9 covering the peripheral surface of the insulating film 8 on the side of one end portion of the substrate 2 .

Likewise, the second external connection electrode 5 B is formed so as to cover not only the surface of the second electrode film 5 A (the pad 5 Ab) and the insulating film 8 exposed within the cutout portion 19 but also the upper end surface of the passivation film 9 on the side of the other end portion of the substrate 2 . The three side surfaces other than the side surface on the inner side of the second external connection electrode 5 B are formed so as to be flush with the surface of the passivation film 9 covering the peripheral surface of the insulating film 8 on the side of the other end portion of the substrate 2 . The external connection electrodes 4 B and 5 B may be formed with, for example, a Ni/Pd/Au laminated film having a Ni film in contact with the electrode films 4 A and 5 A, a Pd film formed thereon and an Au film formed thereon. The laminated film described above can be formed by a plating method.

With reference to FIGS. 50A, 51A, 55 and 56 , as described previously, in the surface of the first external connection electrode 4 B, a plurality of concave portions 84 are formed. The concave portions 84 are formed due to the concave portions 83 in the surface of the first pad 4 Ab, which is its underlying layer. Since the concave portions 83 are formed due to the concave portions 82 , which is its underlying layer, and the concave portions 82 are formed due to the concave portions 81 , which is its underlying layer, the concave portions 84 are formed due to the concave portions 81 . As will be described later, the concave portions 81 are formed due to the electrode-side trenches 21 . Hence, the concave portions 84 in the first external connection electrode 4 B are formed due to the electrode-side trenches 21 .

The passivation film 16 and the resin film 17 coat, from the surface, the coil 3 , the insulating film 8 , the first electrode film 4 A, and the second electrode film 5 A in the coil formation region 10 C of the element formation surface 2 a , and function as a protective film to protect them. On the other hand, the passivation film 9 formed on the side surfaces 2 c of the substrate 2 and the outer peripheral surface of the insulating film 8 function as a protective film to protect the side surfaces 2 c of the substrate 2 and the outer peripheral surface of the insulating film 8 .

FIG. 58 is an electrical circuit diagram showing an electrical structure within the chip inductor 1 A. One end of the coil 3 (represented by a symbol L in FIG. 58 ) is connected to the first electrode 4 , and the other end of the coil 3 is connected to the second electrode. In this way, the chip inductor functions as an inductor having a predetermined inductance.

As a parameter indicating the performance (quality) of the coil, the Q (Quality Factor) value of the coil is present. As the Q value is increased, its loss is decreased, and an excellent characteristic is provided as a high-frequency inductance.

The Q value of the coil 3 is represented by formula (2) below.

Q= 2π fL/R   (2)

In the formula (2) above, f represents the frequency of a current flowing through the coil, L represents the inductance of the coil 3 and R represents the internal resistance of the coil 3 .

In the arrangement of the second preferred embodiment of the second invention (a preferred embodiment of the third invention), in the substrate 2 , the coil formation trench 11 obtained by digging down from the element formation surface 2 a is formed, in plan view, in the shape of a spiral, the conductive member 51 is embedded within the coil formation trench 11 and thus the coil 3 is formed. Hence, it is possible to increase the cross-sectional area of the coil 3 (the cross-sectional area of the coil 3 perpendicular to the direction in which the coil 3 is extended in the spiral direction), and thus it is possible to decrease the internal resistance (R in the formula (2) above) of the coil 3 . In this way, since the Q value of the coil 3 can be increased, it is possible to provide a high performance chip inductor.

The coil formation trench 11 is formed in the substrate 2 , the conductive member 51 is embedded within the coil formation trench 11 and thus it is possible to form the coil 3 , with the result that the coil 3 is easily manufactured. In this way, it is possible to provide a chip transformer that is easily manufactured.

When image inspection is performed on the chip inductor 1 A, light from a light source is applied to the surfaces of the first electrode 4 and the second electrode 5 , and images of the surfaces are imaged with a camera. In the second preferred embodiment of the second invention, in only the surface of any one (in the preferred embodiment, the first external connection electrode 4 B) of the first external connection electrode 4 B of the first electrode 4 and the second external connection electrode 5 B of the second electrode 5 , a plurality of concave portions 84 are formed. Since in the surface of the first external connection electrode 4 B, the concave portions 84 are formed, the light incident on the surface of the first external connection electrode 4 B is diffusely reflected off the concave portions 84 . By contrast, since the concave portion is not formed on the surface of the second external connection electrode 5 B, the light incident on the surface of the second external connection electrode 5 B is unlikely to be diffusely reflected off. Hence, a large difference is produced between image information (for example, brightness information) on the first external connection electrode 4 B and image information on the first external connection electrode 4 B obtained with the camera. In this way, based on the image information obtained with the camera, it is possible to clearly identify the first electrode 4 and the second electrode 5 . In other words, in the second preferred embodiment of the second invention, at the time of the image inspection, it is possible to determine the polarity direction of the chip inductor 1 A without forming a mark indicating the polarity direction on the outer surface of the substrate 2 .

Furthermore, on the element formation surface 2 a , which is one surface of the substrate 2 , both the external connection electrodes 4 B and 5 B of the first electrode 4 and the second electrode 5 are formed. Hence, as shown in FIG. 59 , the element formation surface 2 a is made to face a mounting substrate 91 , the external connection electrodes 4 B and 5 B are bonded on the mounting substrate 91 by a solder 92 and thus it is possible to form a circuit assembly in which the chip inductor 1 A is surface-mounted on the mounting substrate 91 . In other words, it is possible to provide a flip-chip connection-type chip inductor 1 A, and it is possible to connect the chip inductor 1 A to the mounting substrate 91 by a face-down bonding in which the element formation surface 2 a is made to face the mounting substrate 91 and wireless bonding. In this way, it is possible to decrease the occupied space of the chip inductor 1 A on the mounting substrate 91 . In particular, it is possible to realize a low profile chip inductor 1 A on the mounting substrate 91 . In this way, it is possible to effectively utilize the space within the housing of a small-sized electronic device or the like and to contribute to high-density mounting and miniaturization.

FIGS. 60A to 60L are cross-sectional views for illustrating an example of the manufacturing step of the chip inductor 1 A, and show cut surfaces corresponding to FIG. 52 . FIGS. 61A to 61E are partially enlarged cross-sectional views showing the details of the manufacturing step of a coil, and show cut surfaces corresponding to FIG. 53 . FIGS. 62A to 62F are enlarged cross-sectional views showing the details of the manufacturing step of the concave portion of the first electrode and show cut surfaces corresponding to FIG. 56 .

As shown in FIG. 60A , an original substrate 50 that is an original of the substrate main body 6 is prepared. On the surface of the original substrate 50 , the insulating film 7 such as a thermal oxide film or a CVD oxide film is formed. In the preferred embodiment, the insulating film 7 is a thermal oxide film. The surface of the insulating film 7 corresponds to the element formation surface 2 a of the substrate 2 .

FIG. 63 is a schematic plan view of part of the original substrate 50 in which the insulating film 7 is formed on the surface. As shown in FIG. 63 , in the element formation surface 2 a , chip inductor regions X corresponding to a plurality of chip inductors 1 A are disposed in a matrix. Between the chip inductor regions X adjacent to each other, a boundary region Y is provided. The boundary region Y is a region in the shape of a band having a substantially constant width, extends in two directions perpendicular to each other and is formed in a lattice shape. After necessary steps are performed on the original substrate 50 in which the insulating film 7 is formed on the surface, the original substrate 50 is separated along the boundary region Y, and thus it is possible to obtain a plurality of chip inductors 1 A.

The steps performed on the original substrate 50 in which the insulating film 7 is formed on the surface are as follows. First, as shown in FIGS. 60A, 61A, and 62A , by photolithography and etching, a part of the insulating film 7 that corresponds to a region in which the coil formation trench 11 needs to be formed and a part of the insulating film 7 corresponding to the electrode-side trenches 21 are removed. In this way, in the insulating film 7 , the first trench part 11 a of the coil formation trench 11 and the first trench part 21 a of the electrode-side trenches 21 are formed. Then, a hard mask formed with the insulating film 7 is used, and thus the original substrate 50 is etched. In this way, as shown in FIGS. 60B, 61A, and 62A , the second trench part 11 b of the coil formation trench 11 and the second trench part 21 b of the electrode-side trench 21 are formed in the original substrate 50 . In this way, in the insulating film 7 and the original substrate 50 , the coil formation trench 11 and the electrode-side trench 21 are formed. The coil formation trench 11 and the electrode-side trench 21 may be formed with, for example, a so-called BOSCH process. The BOSCH process is a process that is generally used to make a hollow part in a MEMS (Micro Electro Mechanical System).

Then, as shown in FIGS. 61B and 62B , on the inner surface of the coil formation trench 11 and the electrode-side trench 21 , the insulating film (thermal oxide film) 12 is formed by a thermal oxidization method. Here, the surrounding wall (the side wall and the bottom wall) of the trenches 11 and 21 (the second trench parts 11 b and 21 b ) in the original substrate 50 is thermally oxidized into an insulator portion (thermal oxide film) 30 having insulation. In FIG. 60B , the insulating film 12 is omitted but the insulator portion 30 is shown. In the preferred embodiment, the entire wall sandwiched by the coil formation trench 11 (the second trench part 11 b ) in the shape of a spiral in the original substrate 50 and the entire wall between the two adjacent electrode-side trenches 21 (the second trench parts 21 b ) are formed into the thermal oxide film. The insulating film 12 formed on the inner surface of the electrode-side trench 21 (the second trench part 21 b ) fills the electrode-side trench 21 .

Then, for example, by a sputtering method, the barrier metal film 13 made of TiN is formed on the element formation surface 2 a including the interiors of the trenches 11 and 21 . In this way, then, as shown in FIG. 61C , the barrier metal film 13 is formed on the surfaces of the insulating film 12 and the insulating film 7 within the coil formation trench 11 and the surface of the insulating film 7 outside the coil formation trench 11 . As shown in FIG. 62C , the barrier metal film 13 is formed on the surfaces of the insulating film 12 and the insulating film 7 within the electrode-side trench 21 and the surface of the insulating film 7 outside the electrode-side trench 21 . Thereafter, annealing processing is performed.

Then, as shown in FIGS. 60C, 61D, and 62D , for example, by a CVD method, on the element formation surface 2 a including the interiors of the trenches 11 and 21 , the conductive member 51 formed of tungsten (W) is deposited. Since on the entire surface of the element formation surface 2 a including the interiors of the trenches 11 and 21 , the conductive member 51 is deposited at the same rate, in the surface of the conductive member 51 , concave portions 80 are formed in positions opposite the trenches 11 and 21 .

Then, for example, by an etch back method, overall etching is performed on the conductive member 51 from its surface. The overall etching is continued until the surface of the conductive member 51 is flush with the surface of the insulating film 7 . In this way, as shown in FIGS. 60D, 61E, and 62E , the conductive member 51 is embedded within the coil formation trench 11 and the electrode-side trench 21 while in contact with the barrier metal film 13 . By the conductive member 51 embedded within the coil formation trench 11 , the coil 3 in the shape of a spiral when seen in plan view is formed. Since the conductive member 51 is etched from the entire surface thereof at the same rate, on the surface of the conductive member 51 after the etching, the concave portions 81 are formed in positions opposite the concave portions 80 before the etching. However, although for ease of description, the concave portions 81 are shown in FIG. 62E , the concave portions are omitted in FIG. 61E .

Then, as shown in FIGS. 60E and 62F , on the insulating film 7 , the insulating film 8 formed with a USG (Undoped Silicate Glass) film or the like is formed so as to coat the insulating film 7 (the element formation surface 2 a ) and the conductive member 51 . The insulating film 8 is formed by, for example, a CVD method. In the surface of the insulating film 8 formed as described above, as shown in FIG. 62F , in positions opposite the concave portions 81 , the concave portions 82 are formed. Thereafter, by photolithography and etching, in regions of the insulating film 8 corresponding to one end portion and the other end portion of the coil 3 , the first contact hole 14 (see FIG. 54 ) and the second contact hole 15 (see FIG. 60E ) penetrating the insulating film 8 are respectively formed.

Then, for example, by sputtering, on the insulating film 8 including the interiors of the contact holes 14 and 15 , an electrode film forming the first electrode 4 and the second electrode 5 is formed. In the preferred embodiment, the electrode film made of Al is formed. Thereafter, by photolithography and etching, the electrode film is patterned, and thus as shown in FIGS. 60F and 62F , the electrode film is separated into the first electrode film 4 A and the second electrode film 5 A. In the surface of the first electrode film 4 A formed as described above, as shown in FIG. 62F , in positions opposite the concave portions 82 , the concave portions 83 are formed.

Then, as shown in FIG. 60G , for example, by a CVD method, the passivation film 16 such as a nitride film is formed, and furthermore, polyimide is applied to form the resin film 17 . For example, polyimide to which photosensitivity is added is applied, and the polyimide is developed after exposure with a pattern corresponding to the cutout portions 18 and 19 . In this way, the resin film 17 having a cutout portion corresponding to the cutout portions 18 and 19 is formed. Thereafter, as necessary, heat treatment for curing the resin film is performed. Then, by dry etching using the resin film 17 as a mask, the cutout portions 18 and 19 are formed in the passivation film 16 .

Then, as shown in FIG. 60H , a resist mask 52 having an opening 52 a in a lattice shape matching with the boundary region Y (see FIG. 63 ) is formed. Plasma etching is performed via the resist mask 52 , and thus as shown in FIG. 60H , the original substrate 50 , the insulating film 7 , and the insulating film 8 are etched from the surface of the insulating film 8 to a predetermined depth. In this way, along the boundary region Y, a groove (scribe groove) 53 for cutting is formed.

Then, the resist mask 52 is peeled off. Thereafter, as shown in FIG. 60I , for example, by a CVD method, an insulating film 54 such as a nitride film serving as the material of the passivation film 9 is formed over the entire region of the surface of the original substrate 50 . Here, the insulating film 54 is also formed over the entire region of the inner surface (the side wall surface and the bottom wall surface) of the groove 53 .

Then, as shown in FIG. 60J , the insulating film 54 is selectively etched. Specifically, a part of the insulating film 54 other than the insulating film 54 (the passivation film 9 ) on the side wall surface of the groove 53 is removed. In this way, a part of the electrode films 4 A and 5 A that is not covered by the passivation film 16 and the resin film 17 is exposed. The insulating film 54 on the bottom surface of the groove 53 is removed.

Then, as shown in FIGS. 60K and 62F , on the first electrode film 4 A (the first pad 4 Ab) and the second electrode film 5 A (the second pad 5 Ab) exposed from the cutout portions 18 and 19 , for example, by plating (preferably, electroless plating), plating growth is performed in the following order: for example, Ni, Pd, and Au. In this way, the first external connection electrode 4 B and the second external connection electrode 5 B are formed. In the surface of the first external connection electrode 4 B formed as described above, as shown in FIG. 62F , in positions opposite the concave portions 83 , the concave portions 84 are formed.

Thereafter, by a DBG (Dicing Before Grinding) method, a plurality of chip inductor regions X are divided into pieces. Specifically, as shown in FIG. 60L , first, on the side of the surface of the original substrate 50 (the side of the external connection electrode), a supporting tape 71 having an adhesive surface 72 is adhered. Then, the original substrate 50 is polished from the rear surface to the bottom surface of the groove 53 . In this way, the plurality of chip inductor regions X are separated into individual chip inductors 1 A. Thereafter, on a plurality of chip inductors 1 A, the recovery step shown in FIGS. 45A to 45D and the recovery step shown in FIGS. 46A to 46C described in the first preferred embodiment of the second invention may be performed.

Even in the second preferred embodiment of the second invention (a preferred embodiment of the third invention), the structure of the conductive member 51 embedded within the coil formation trench 11 may be the structure shown in FIGS. 48A and 48B described as the modification example of the conductive member 51 of the first preferred embodiment of the second invention.

FIG. 64A is a partially cut perspective view of a chip inductor according to the third preferred embodiment of the second invention, and FIG. 64B is a perspective view showing a coil formed within the chip inductor.

The chip inductor 1 B is a minute chip part and is formed in the shape of a rectangular parallelepiped. The planar shape of the chip inductor 1 B may be rectangular, the length L in the longitudinal direction may be about 0.4 mm and the length W in the lateral direction may be about 0.2 mm. The thickness T of the entire chip inductor 1 B may be about 0.15 mm.

The chip inductor 1 B includes a substrate 2 , a coil 3 that is formed within the substrate 2 , a first electrode 4 that is connected to one end portion of the coil 3 , and a second electrode 5 that is connected to the other end portion of the coil 3 .

FIG. 65A is a plan view showing the appearance of the chip inductor when seen from the side of the electrode, FIG. 65B is a plan view showing the internal structure of the chip inductor, FIG. 66 is a cross-sectional view taken along line LXVI-LXVI in FIG. 65B , FIG. 67 is a partially enlarged cross-sectional view of FIG. 66 , FIG. 68 is a cross-sectional view taken along line LXVIII-LXVIII in FIG. 65B , FIG. 69 is a cross-sectional view taken along line LXIX-LXIX in FIG. 65B , FIG. 70 is a partially enlarged cross-sectional view of FIG. 69 , FIG. 71 is a cross-sectional view taken along line LXXI-LXXI in FIG. 65B , and FIG. 72 is a plan view showing a structure of the surface of a substrate by removing an arrangement formed on the surface of the substrate.

The substrate 2 is formed in the shape of a rectangular parallelepiped, and includes a pair of main surfaces 2 a and 2 b and four side surfaces 2 c . One (the main surface 2 a on the upper surface side in FIG. 64A ) of the pair of main surfaces 2 a and 2 b is an element formation surface. In the following description, the main surface 2 a is referred to as an “element formation surface 2 a ,” and the main surface 2 b on the side opposite to the element formation surface 2 a is referred to as a “rear surface 2 b .” In the preferred embodiment, the substrate 2 is formed with a substrate main body 6 and an insulating film 7 formed on the surface thereof, and the surface of the insulating film 7 on the side opposite to the side of the substrate main body 6 is the element formation surface 2 a . The element formation surface 2 a is formed in the shape of a rectangle in plan view when seen in a normal direction perpendicular to the element formation surface 2 a . The surface (element formation surface 2 a ) of the substrate 2 is covered by an insulating film 8 . The four side surfaces 2 c of the substrate 2 and the outer peripheral surface of the insulating film 8 are covered by a passivation film 9 such as a nitride film.

With reference to FIG. 65B , in the element formation surface 2 a , a first electrode formation region 10 A for the formation of the first electrode 4 is provided at one end portion thereof, and a second electrode formation region 10 B for the formation of the second electrode 5 is provided at the other end portion. These regions 10 A and 10 B are rectangular in plan view. In the element formation surface 2 a between the first electrode formation region 10 A and the second electrode formation region 10 B, a coil formation region 10 C is provided. In the preferred embodiment, the coil formation region 10 C is formed in the shape of a rectangle.

In the first electrode formation region 10 A, the external connection electrode (first external connection electrode) 4 B of the first electrode 4 is disposed, and in the second electrode formation region 10 B, the external connection electrode (second external connection electrode) 5 B of the second electrode 5 is disposed. The first external connection electrode 4 B is rectangular in plan view, and covers the entire region of the first electrode formation region 10 A. The second external connection electrode 5 B is rectangular in plan view, and covers the entire region of the second electrode formation region 10 B.

In the surface of the first external connection electrode 4 B, a plurality of first concave portions 84 A are formed, and in the surface of the second external connection electrode 4 B, a plurality of second concave portions 84 B are formed. The first concave portions 84 A are formed, in plan view, in the shape of a straight line extending in the longitudinal direction of the substrate 2 , and are formed at an interval in the lateral direction of the substrate 2 . Likewise, the plurality of second concave portions 84 are formed, in plan view, in the shape of a straight line extending in the longitudinal direction of the substrate 2 , and are formed at an interval in the lateral direction of the substrate 2 . The cross-sectional shape of the concave portions 84 A and 84 B is the shape of the letter V. The first concave portions 84 A are formed in the same method as the concave portions 84 in the second preferred embodiment described previously. The second concave portions 84 B are formed in the same method as the first concave portions 84 A.

In the substrate 2 , a coil formation trench 11 is formed by digging down, in the coil formation region 10 C, to a predetermined depth from the element formation surface 2 a . The coil formation trench 11 is formed, in plan view, in the shape of a spiral. In the preferred embodiment, the coil formation trench 11 is formed, in plan view, in the shape of a quadrilateral spiral, and has a plurality of rectilinear portions parallel to the side surfaces 2 c of the substrate 2 . The cross section (cross section in a direction perpendicular to a direction in which the coil formation trench 11 is extended in the spiral direction) of the coil formation trench 11 is formed in the shape of a rectangle which is long in the direction of the thickness of the substrate 2 . For example, the width of the coil formation trench 11 may be 1 μm or more and 3 μm or less. For example, the depth of the coil formation trench 11 may be 10 μm or more and 82 μm or less. The depth of the coil formation trench 11 is preferably 10 μm or more so that the internal resistance of the coil 3 formed within the coil formation trench 11 is decreased.

Furthermore, in a region (the first electrode formation region 10 A) of the element formation surface 2 a opposite the first external connection electrode 4 B, in the substrate 2 , a plurality of first electrode-side trenches 21 A are formed by digging down from the element formation surface 2 a to a predetermined depth. The plurality of first electrode-side trenches 21 A are formed in positions opposite the plurality of first concave portions 84 A. Hence, the first electrode-side trenches 21 A are formed, in plan view, in the shape of a straight line extending in the longitudinal direction of the substrate 2 , and are formed at an interval in the lateral direction of the substrate 2 .

Likewise, in a region (the second electrode formation region 10 B) of the element formation surface 2 a opposite the second external connection electrode 5 B, in the substrate 2 , a plurality of second electrode-side trenches 21 B are formed by digging down from the element formation surface 2 a to a predetermined depth. The plurality of second electrode-side trenches 21 B are formed in positions opposite the plurality of second concave portions 84 B. Hence, the plurality of second electrode-side trenches 21 B are formed, in plan view, in the shape of a straight line extending in the longitudinal direction of the substrate 2 , and are formed at an interval in the lateral direction of the substrate 2 .

The cross sections of the electrode-side trenches 21 A and 21 B are the shape of a rectangle that is long in the direction of the thickness of the substrate 2 . In the preferred embodiment, the width of the electrode-side trenches 21 A and 21 B is narrower than that of the coil formation trench 11 . The depth of the electrode-side trenches 21 A and 21 B may be the same as that of the coil formation trench 11 or may be shallower than that of the coil formation trench 11 . In the preferred embodiment, the depth of the electrode-side trenches 21 A and 21 B is the same as that of the coil formation trench 11 .

As shown in FIG. 67 , the coil formation trench 11 is formed with a first trench part 11 a that is formed in the insulating film 7 and a second trench part 11 b that is formed in the substrate main body 6 and that communicates with the first trench part 11 a . On the inner surface of the coil formation trench 11 (the second trench part 11 b ) in the substrate main body 6 , an insulating film 12 formed with an oxide film or the like is formed. On the surface of the insulating film 12 within the coil formation trench 11 (the second trench part 11 b ) and on the inner surface of the coil formation trench 11 (the first trench part 11 a ) in the insulating film 7 , a barrier metal film 13 is formed. The barrier metal film 13 is formed of, for example, TiN. The thickness of the barrier metal film 13 is about 400 to 500 angstroms.

Within the coil formation trench 11 , a conductive member 51 is embedded while being in contact with the barrier metal film 13 . In the preferred embodiment, the conductive member 51 is formed of tungsten (W). The coil 3 is formed with the conductive member 51 embedded within the coil formation trench 11 . Hence, the coil 3 is formed, in plan view, in the shape of a spiral (in the shape of a quadrilateral spiral) of the same pattern as the coil formation trench 11 . Specifically, the coil 3 includes a plurality of plate-shaped parts parallel to the side surfaces 2 c of the substrate 2 .

As shown in FIGS. 69, 70, and 71 , the electrode-side trenches 21 A and 21 B are formed with first trench parts 21 Aa and 21 Ba that are formed in the insulating film 7 and second trench parts 21 Ab and 21 Bb that are formed in the substrate main body 6 and that communicate with the first trench parts 21 Aa and 21 Ba. On the inner surface of the electrode-side trenches 21 A and 21 B (the second trench parts 21 Ab and 21 Bb) in the substrate main body 6 , an insulating film 12 formed with an oxide film or the like is formed. In the preferred embodiment, the insulating film 12 formed on the inner surface of the electrode-side trenches 21 A and 21 B (the second trench parts 21 Ab and 21 Bb) in the substrate main body 6 fills the second trench parts 21 Ab and 21 Bb.

On the inner surface of the first electrode-side trench 21 A (the first trench part 21 Aa) in the insulating film 7 , the barrier metal film 13 is formed. Within the first electrode-side trench 21 A (the first trench part 21 Aa) in the insulating film 7 , the conductive member 51 is embedded while being in contact with the barrier metal film 13 . In the surface of the conductive member 51 within the first electrode-side trench 21 A, first concave portions 81 A are formed. In other words, in a region of the element formation surface 2 a opposite the first external connection electrode 4 B, a plurality of first concave portions 81 A are formed. The plurality of first concave portions 81 A are formed in positions of the first external connection electrode 4 B opposite the first concave portions 84 A. Hence, the plurality of first concave portions 81 A are formed, in plan view, in the shape of a straight line extending in the longitudinal direction of the substrate 2 , and are formed at an interval in the lateral direction of the substrate 2 . The cross-sectional shape of the first concave portion 81 A is the shape of the letter V. The plurality of first concave portions 81 A are formed due to the plurality of first electrode-side trenches 21 A formed in the substrate 2 .

Likewise, on the inner surface of the second electrode-side trench 21 B (the first trench part 21 Ba) in the insulating film 7 , the barrier metal film (not shown) is formed. Within the second electrode-side trench 21 B (the first trench part 21 Ba) in the insulating film 7 , the conductive member 51 is embedded while being in contact with the barrier metal film. In the surface of the conductive member 51 within the second electrode-side trench 21 B, second concave portions 81 B are formed. In other words, in a region of the element formation surface 2 a opposite the second external connection electrode 5 B, a plurality of second concave portions 81 B are formed. The plurality of second concave portions 81 B are formed in positions opposite the plurality of second concave portions 84 B of the second external connection electrode 5 B. Hence, the plurality of second concave portions 81 B are formed, in plan view, in the shape of a straight line extending in the longitudinal direction of the substrate 2 , and are formed at an interval in the lateral direction of the substrate 2 . The cross-sectional shape of the second concave portion 81 B is the shape of the letter V. The plurality of second concave portions 81 B are formed due to the plurality of second electrode-side trenches 21 B formed in the substrate 2 .

In the preferred embodiment, the insulating film 12 formed on the inner surfaces of the coil formation trench 11 and the electrode-side trenches 21 A and 21 B is formed with a thermal oxide film (SiO 2 ). When the thermal oxide film is formed on the inner surface of these trenches 11 , 21 A, and 21 B, the surrounding wall (the side wall and the bottom wall) of the trenches 11 , 21 A, and 21 B in the substrate main body 6 is thermally oxidized into an insulator portion (thermal oxide film) 30 having insulation. In the preferred embodiment, an example is described where the entire wall sandwiched by the coil formation trench 11 (the second trench part 11 b ) in the shape of a spiral in the substrate main body 6 , the entire wall between the adjacent two first electrode-side trenches 21 A (the second trench parts 21 Ab), and the entire wall between the adjacent two second electrode-side trenches 21 B (the second trench parts 21 Bb) are thermal oxide films.

On the element formation surface 2 a (the surface of the insulating film 7 ) of the substrate 2 , the insulating film 8 is formed so as to coat the element formation surface 2 a and the conductive member 51 . The insulating film 8 is formed, in plan view, in the shape of a rectangle matching with the element formation surface 2 a . The insulating film 8 is formed with, for example, a USG (Undoped Silicate Glass) film. In the insulating film 8 , a first contact hole 14 (see FIGS. 65B and 68 ) that exposes one end portion (outer peripheral side end portion) of the coil 3 and a second contact hole 15 (see FIGS. 65B and 66 ) that exposes the other end portion (inner peripheral side end portion) of the coil 3 are formed.

Furthermore, in the surface of the insulating film 8 , as shown in FIGS. 69 and 70 , in a region opposite the first external connection electrode 4 B, a plurality of first concave portions 82 A are formed. The plurality of first concave portions 82 A are formed in positions opposite the first concave portions 84 A (the first concave portions 81 A) of the first external connection electrode 4 B. Hence, the plurality of first concave portions 82 A are formed, in plan view, in the shape of a straight line extending in the longitudinal direction of the substrate 2 , and are formed at an interval in the lateral direction of the substrate 2 . The cross-sectional shape of the first concave portion 82 A is the shape of the letter V. The first concave portions 82 A are formed due to the first concave portions 81 A in the surface (the element formation surface 2 a ) of the substrate 2 , which is its underlying layer.

Likewise, in the surface of the insulating film 8 , as shown in FIG. 71 , in a region opposite the second external connection electrode 5 B, a plurality of second concave portions 82 B are formed. The plurality of second concave portions 82 B are formed in positions opposite the second concave portions 84 B (the second concave portions 81 B) of the second external connection electrode 5 B. Hence, the plurality of second concave portions 82 B are formed, in plan view, in the shape of a straight line extending in the longitudinal direction of the substrate 2 , and are formed at an interval in the lateral direction of the substrate 2 . The cross-sectional shape of the second concave portion 82 B is the shape of the letter V. The second concave portions 82 B are formed due to the second concave portions 81 B in the surface (the element formation surface 2 a ) of the substrate 2 , which is its underlying layer. As described previously, on the side surfaces 2 c of the substrate 2 and the outer peripheral surface of the insulating film 8 , a passivation film 9 such as a nitride film is formed.

On the surface of the insulating film 8 , the first electrode 4 and the second electrode 5 are formed. The first electrode 4 includes a first electrode film 4 A that is formed on the surface of the insulating film 8 and a first external connection electrode 4 B that is bonded to the first electrode film 4 A. As shown in FIG. 65B , the first electrode film 4 A includes a drawing electrode 4 Aa that is connected to one end portion of the coil 3 and a first pad 4 Ab that is formed integrally with the drawing electrode 4 Aa. The first pad 4 Ab is formed to be rectangular at one end portion of the element formation surface 2 a . The first external connection electrode 4 B is connected to the first pad 4 Ab. As shown in FIGS. 65B and 68 , the drawing electrode 4 Aa enters the first contact hole 14 from the surface of the insulating film 8 , and is connected to one end portion of the coil 3 within the first contact hole 14 . The drawing electrode 4 Aa is formed straight along a straight line that passes above one end portion of the coil 3 to reach the first pad 4 Ab.

By extending one end portion of the coil formation trench 11 to a position below the first pad 4 Ab, one end portion of the coil 3 may be disposed in a position below the first pad 4 Ab. In this way, since the first contact hole 14 can be formed in a position below the first pad 4 Ab, one end portion of the coil 3 can be connected to the first pad 4 Ab. In this case, since the first electrode film 4 A can be formed with only the first pad 4 Ab, the drawing electrode 4 Aa is not needed.

The second electrode 5 includes a second electrode film 5 A that is formed on the surface of the insulating film 8 and a second external connection electrode 5 B that is bonded to the second electrode film 5 A. As shown in FIG. 65B , the second electrode film 5 A includes a drawing electrode 5 Aa that is connected to the other end portion of the coil 3 and a second pad 5 Ab that is formed integrally with the drawing electrode 5 Aa. The second pad 5 Ab is formed to be rectangular at the other end portion of the element formation surface 2 a . The second external connection electrode 5 B is connected to the second pad 5 Ab. As shown in FIGS. 65B and 66 , the drawing electrode 5 Aa enters the second contact hole 15 from the surface of the insulating film 8 , and is connected to the other end portion of the coil 3 within the second contact hole 15 . The drawing electrode 5 Aa is formed straight along a straight line that passes above the other end portion of the coil 3 to reach the second pad 5 Ab. In the preferred embodiment, as the electrode films 4 A and 5 A, Al films are used.

In the surface of the first pad 4 Ab of the first electrode film 4 A, as shown in FIGS. 69 and 70 , a plurality of first concave portions 83 A are formed. The plurality of first concave portions 83 A are formed in positions opposite the first concave portions 84 A (the first concave portions 82 A) of the first external connection electrode 4 B. Hence, the plurality of first concave portions 83 A are formed, in plan view, in the shape of a straight line extending in the longitudinal direction of the substrate 2 , and are formed at an interval in the lateral direction of the substrate 2 . The cross-sectional shape of the first concave portion 83 A is the shape of the letter V. The first concave portions 83 A are formed due to the first concave portions 82 A in the surface of the insulating film 8 , which is its underlying layer.

Likewise, in the surface of the second pad 5 Ab of the second electrode film 5 A, as shown in FIG. 71 , a plurality of second concave portions 83 B are formed. The plurality of second concave portions 83 B are formed in positions opposite the second concave portions 84 B (the second concave portions 82 B) of the second external connection electrode 5 B. Hence, the plurality of second concave portions 83 B are formed, in plan view, in the shape of a straight line extending in the longitudinal direction of the substrate 2 , and are formed at an interval in the lateral direction of the substrate 2 . The cross-sectional shape of the second concave portion 83 B is the shape of the letter V. The second concave portions 83 B are formed due to the second concave portions 82 B in the surface of the insulating film 8 , which is its underlying layer.

The first electrode film 4 A and the second electrode film 5 A are covered by a passivation film 16 formed with, for example, a nitride film, and furthermore, on the passivation film 16 , a resin film 17 such as polyimide is formed. In the passivation film 16 and the resin film 17 , two cutout portions 18 and 19 are formed that respectively expose a region other than an edge portion on the inner side of the surface of the first pad 4 Ab of the first electrode film 4 A and a region other than an edge portion on the inner side of the surface of the second pad 5 Ab of the second electrode film 5 A. In other words, the passivation film 16 and the resin film 17 are formed, in plan view, in a region corresponding to the coil formation region 10 C of the element formation surface 2 a , and cover the insulating film 8 , the edge portion on the inner side of the surface of the first pad 4 Ab, and the edge portion on the inner side of the surface of the second pad 5 Ab.

The first external connection electrode 4 B fills the cutout portion 18 , and the second external connection electrode 5 B fills the cutout portion 19 . The first external connection electrode 4 B and the second external connection electrode 5 B are formed so as to protrude from the resin film 17 , and include a drawing portion 20 that is drawn inwardly of the substrate 2 along the surface of the resin film 17 . In the preferred embodiment, the first external connection electrode 4 B is formed so as to cover not only the surface of the first electrode film 4 A (the pad 4 Ab) and the insulating film 8 exposed within the cutout portion 18 but also the upper end surface of the passivation film 9 on the side of one end portion of the substrate 2 . The three side surfaces other than the side surface on the inner side of the first external connection electrode 4 B are formed so as to be flush with the surface of the passivation film 9 covering the peripheral surface of the insulating film 8 on the side of one end portion of the substrate 2 .

Likewise, the second external connection electrode 5 B is formed so as to cover not only the surfaces of the second electrode film 5 A (the pad 5 Ab) and the insulating film 8 exposed within the cutout portion 19 but also the upper end surface of the passivation film 9 on the side of the other end portion of the substrate 2 . The three side surfaces other than the side surface on the inner side of the second external connection electrode 5 B are formed so as to be flush with the surface of the passivation film 9 covering the peripheral surface of the insulating film 8 on the side of the other end portion of the substrate 2 . The external connection electrodes 4 B and 5 B may be formed with, for example, a Ni/Pd/Au laminated film having a Ni film in contact with the electrode films 4 A and 5 A, a Pd film formed thereon, and an Au film formed thereon. The laminated film described above can be formed by a plating method.

With reference to FIGS. 64A, 65A, 69, 70, and 71 , as described previously, in the surface of the first external connection electrode 4 B, a plurality of first concave portions 84 A are formed, and in the surface of the second external connection electrode 5 B, a plurality of second concave portions 84 B are formed. The first concave portions 84 A are formed due to the first concave portions 83 A in the surface of the first pad 4 Ab, which is its underlying layer. Since the first concave portions 83 A are formed due to the first concave portions 82 A, which is its underlying layer, and the first concave portions 82 A are formed due to the first concave portions 81 A, which is its underlying layer, the first concave portions 84 A are formed due to the first concave portions 81 A. As described in the second preferred embodiment of the second invention, the first concave portions 81 A (the concave portion 81 in the second preferred embodiment) are formed due to the first electrode-side trenches 21 A (the electrode-side trenches 21 in the second preferred embodiment). Hence, the first concave portions 84 A in the first external connection electrode 4 B are formed due to the first electrode-side trenches 21 A.

The second concave portions 84 B are formed due to the second concave portions 83 B in the surface of the second pad 5 Ab, which is its underlying layer. Since the second concave portions 83 B are formed due to the second concave portions 82 B, and the second concave portions 82 B are formed due to the second concave portions 81 B, the second concave portions 84 B are formed due to the second concave portions 81 B. As the first concave portions 81 A are formed due to the first electrode-side trenches 21 A, the second concave portions 81 B are formed due to the second electrode-side trenches 21 B. Hence, the second concave portions 84 B in the second external connection electrode 5 B are formed due to the second electrode-side trenches 21 B.

The passivation film 16 and the resin film 17 coat, from the surface, the coil 3 , the insulating film 8 , the first electrode film 4 A, and the second electrode film 5 A in the coil formation region 10 C of the element formation surface 2 a , and function as a protective film to protect them. On the other hand, the passivation film 9 formed on the side surfaces 2 c of the substrate 2 and the outer peripheral surface of the insulating film 8 function as a protective film to protect the side surfaces 2 c of the substrate 2 and the outer peripheral surface of the insulating film 8 .

The chip inductor 1 B of the third preferred embodiment of the second invention can be manufactured substantially in the same manufacturing method as in the second preferred embodiment of the second invention. The third preferred embodiment of the second invention only differs in the manufacturing step from the second preferred embodiment of the second invention in that in the formation of the coil formation trench 11 , not only the first electrode-side trenches 21 A but also the second electrode-side trenches 21 B are formed, and thus its description will be omitted.

FIG. 73 is an electrical circuit diagram showing an electrical structure within the chip inductor 1 B. One end of the coil 3 (represented by a symbol L in FIG. 73 ) is connected to the first electrode 4 , and the other end of the coil 3 is connected to the second electrode. In this way, the chip inductor functions as an inductor having a predetermined inductance.

As a parameter indicating the performance (quality) of the coil, the Q (Quality Factor) value of the coil is present. As the Q value is increased, its loss is decreased, and an excellent characteristic is provided as a high-frequency inductance.

The Q value of the coil 3 is represented by formula (3) below.

Q= 2π fL/R   (3)

In the formula (3) above, f represents the frequency of a current flowing through the coil, L represents the inductance of the coil 3 , and R represents the internal resistance of the coil 3 .

In the arrangement of the third preferred embodiment of the second invention, in the substrate 2 , the coil formation trench 11 obtained by digging down from the element formation surface 2 a is formed, in plan view, in the shape of a spiral, the conductive member 51 is embedded within the coil formation trench 11 and thus the coil 3 is formed. Hence, it is possible to increase the cross-sectional area of the coil 3 (the cross-sectional area of the coil 3 perpendicular to the direction in which the coil 3 is extended in the spiral direction), and thus it is possible to decrease the internal resistance (R in the formula (3) above) of the coil 3 . In this way, since the Q value of the coil 3 can be increased, it is possible to provide a high-performance chip inductor.

The coil formation trench 11 is formed in the substrate 2 , the conductive member 51 is embedded within the coil formation trench 11 and thus it is possible to form the coil 3 , with the result that the coil 3 is easily manufactured. In this way, it is possible to provide a chip transformer that is easily manufactured.

In the third preferred embodiment of the second invention, in the region (the first electrode formation region 10 A) opposite the first external connection electrode 4 B of the element formation surface 2 a , a plurality of first electrode-side trenches 21 A are formed, and in the region (the second electrode formation region 10 B) opposite the second external connection electrode 5 B of the element formation surface 2 a , a plurality of second electrode-side trenches 21 B are formed. The wall between the adjacent first electrode-side trenches 21 A and the wall between the adjacent second electrode-side trenches 21 B in the substrate main body 6 are formed in the insulator portion 30 having insulation. The insulating film 12 substantially fills the entire region within the electrode-side trenches 21 A and 21 B. In this way, substantially the entire region immediately below the pad 4 Ab of the first electrode 4 and the pad 5 Ab of the second electrode 5 in the substrate main body 6 is formed in the insulator portion 30 . Hence, it is possible to reduce the parasitic capacitance between the substrate main body 6 and the first electrode 4 and the second electrode 5 opposite each other through the insulating film 7 as compared with the case where a main body substrate (semiconductor substrate) having no insulator portion is used.

Furthermore, on the element formation surface 2 a , which is one surface of the substrate 2 , both the external connection electrodes 4 B and 5 B of the first electrode 4 and the second electrode 5 are formed. Hence, as shown in FIG. 74 , the element formation surface 2 a is made to face a mounting substrate 91 , the external connection electrodes 4 B and 5 B are bonded on the mounting substrate 91 by a solder 92 and thus it is possible to form a circuit assembly in which the chip inductor 1 B is surface-mounted on the mounting substrate 91 . In other words, it is possible to provide a flip-chip connection-type chip inductor 1 B, and it is possible to connect the chip inductor 1 B to the mounting substrate 91 by a face-down bonding in which the element formation surface 2 a is made to face the mounting substrate 91 and wireless bonding. In this way, it is possible to decrease the occupied space of the chip inductor 1 B on the mounting substrate 91 . In particular, it is possible to realize a low profile chip inductor 1 on the mounting substrate 91 . In this way, it is possible to effectively utilize the space within the housing of a small-sized electronic device or the like and to contribute to high-density mounting and miniaturization.

FIGS. 75A and 75B are cross-sectional views showing a modification example of the external connection electrode for the chip inductors 1 A and 1 B of the second preferred embodiment (a preferred embodiment of the third invention) and the third preferred embodiment of the second invention. FIG. 75A shows a cut surface corresponding to FIG. 52 ( FIG. 66 ), and FIG. 75B shows a cut surface corresponding to FIG. 55 ( FIG. 69 ). In FIGS. 75A and 75B , the portions corresponding to the portions of FIGS. 52 ( 66 ) and 55 ( 69 ) described previously are provided with the same symbols of FIGS. 52 ( 66 ) and 55 ( 69 ).

The first external connection electrode 4 B fills one cutout portion 18 in the passivation film 16 and the resin film 17 , and the second external connection electrode 5 B fills the other cutout portion 19 .

The first external connection electrode 4 B is formed so as to cover the upper portion of the passivation film 9 on the side of one end portion of the substrate 2 and to straddle, from the peripheral portion of the surface of the insulating film 8 , the surface of the passivation film 9 covering the three side surfaces 2 c on the side of one end portion of the substrate 2 . In other words, the first external connection electrode 4 B is formed so as to cover not only the surface of the first electrode film 4 A (the pad 4 Ab) and the insulating film 8 exposed within the cutout portion 18 but also the passivation film 9 on the three side surfaces 2 c of the substrate 2 .

Likewise, the second external connection electrode 5 B is formed so as to cover the upper portion of the passivation film 9 on the side of the other end portion of the substrate 2 and to straddle, from the peripheral portion of the surface of the insulating film 8 , the surface of the passivation film 9 covering the three side surfaces 2 c on the side of the other end portion of the substrate 2 . In other words, the second external connection electrode 5 B is formed so as to cover not only the surface of the second electrode film 5 A (the pad 5 Ab) and the insulating film 8 exposed within the cutout portion 19 but also the passivation film 9 on the three side surfaces 2 c on the side of the other end portion of the substrate 2 .

As described above, in the chip inductors 1 A and 1 B, the first external connection electrode 4 B is formed so as to cover the three side surfaces 2 c on the side of one end portion of the substrate 2 , and the second external connection electrode 5 B is formed so as to cover the three side surfaces 2 c on the side of the other end portion of the substrate 2 . In other words, the external connection electrodes 4 B and 5 B are formed not only on the element formation surface 2 a on the substrate 2 but also on the side surfaces 2 c of the substrate 2 . In this way, in the form shown in FIG. 59 or FIG. 74 described previously, when the external connection electrodes 4 B and 5 B of the chip inductors 1 A and 1 B are soldered to the mounting substrate, it is possible to increase the bonding area between the external connection electrodes 4 B and 5 B and the mounting substrate. Consequently, it is possible to enhance the bonding strength of the external connection electrodes 4 B and 5 B on the mounting substrate.

Even in the third preferred embodiment of the second invention, the structure of the conductive member 51 embedded within the coil formation trench 11 may be the structure shown in FIGS. 48A and 48B described as the modification example of the conductive member 51 of the first preferred embodiment of the second invention.

FIG. 76A is a partially cut perspective view of a chip inductor according to a fourth preferred embodiment of the second invention, and FIG. 76B is a perspective view showing a coil formed within the chip inductor.

The chip inductor 1 C is a minute chip part and is formed in the shape of a rectangular parallelepiped. The planar shape of the chip inductor 1 C may be rectangular, the length L in the longitudinal direction may be about 0.4 mm and the length W in the lateral direction may be about 0.2 mm. The thickness T of the entire chip inductor 1 C may be about 0.15 mm.

The chip inductor 1 C includes a substrate 2 , a coil 3 that is formed within the substrate 2 , a first electrode 4 that is connected to one end portion of the coil 3 and a second electrode 5 that is connected to the other end portion of the coil 3 .

FIG. 77 is a plan view of the chip inductor, FIG. 78 is a cross-sectional view taken along line LXXVIII-LXXVIII in FIG. 77 , FIG. 79 is a partially enlarged cross-sectional view of FIG. 78 , FIG. 80 is a cross-sectional view taken along line LXXX-LXXX in FIG. 77 , FIG. 81 is a cross-sectional view taken along line LXXXI-LXXXI in FIG. 77 and FIG. 82 is a plan view showing a structure of the surface of a substrate by removing an arrangement formed on the surface of the substrate.

The substrate 2 is formed in the shape of a rectangular parallelepiped, and includes a pair of main surfaces 2 a and 2 b and four side surfaces 2 c . One (the main surface 2 a on the upper surface side in FIG. 76A ) of the pair of main surfaces 2 a and 2 b is an element formation surface. In the following description, the main surface 2 a is referred to as an “element formation surface 2 a ,” and the main surface 2 b on the side opposite to the element formation surface 2 a is referred to as a “rear surface 2 b .” In the preferred embodiment, the substrate 2 is formed with a substrate main body 6 and an insulating film 7 formed on the surface thereof, and the surface of the insulating film 7 on the side opposite to the side of the substrate main body 6 is the element formation surface 2 a . The element formation surface 2 a is formed in the shape of a rectangle in plan view when seen in a normal direction perpendicular to the element formation surface 2 a . The surface (element formation surface 2 a ) of the substrate 2 is covered by an insulating film 32 . The four side surfaces 2 c of the substrate 2 and the outer peripheral surface of the insulating film 32 are covered by a passivation film 9 such as a nitride film.

With reference to FIG. 77 , in the element formation surface 2 a , a first electrode formation region 10 A for the formation of the first electrode 4 is provided at one end portion thereof, and a second electrode formation region 10 B for the formation of the second electrode 5 is provided at the other end portion. These regions 10 A and 10 B are rectangular in plan view. In the element formation surface 2 a between the first electrode formation region 10 A and the second electrode formation region 10 B, a coil formation region 10 C is provided. In the preferred embodiment, the coil formation region 10 C is formed in the shape of a rectangle.

In the first electrode formation region 10 A, the external connection electrode (first external connection electrode) 4 B of the first electrode 4 is disposed, and in the second electrode formation region 10 B, the external connection electrode (second external connection electrode) 5 B of the second electrode 5 is disposed. The first external connection electrode 4 B is rectangular in plan view, and covers the entire region of the first electrode formation region 10 A. The second external connection electrode 5 B is rectangular in plan view, and covers the entire region of the second electrode formation region 10 B.

In the substrate 2 , a coil formation trench 11 is formed by digging down, in the coil formation region 10 C, to a predetermined depth from the element formation surface 2 a . The coil formation trench 11 is formed, in plan view, in the shape of a spiral. In the preferred embodiment, the coil formation trench 11 is formed, in plan view, in the shape of a quadrilateral spiral, and has a plurality of rectilinear portions parallel to the side surfaces 2 c of the substrate 2 . The cross section (cross section in a direction perpendicular to a direction in which the coil formation trench 11 is extended in the spiral direction) of the coil formation trench 11 is formed in the shape of a rectangle which is long in the direction of the thickness of the substrate 2 . For example, the width of the coil formation trench 11 may be 1 μm or more and 3 μm or less. For example, the depth of the coil formation trench 11 may be 10 μm or more and 82 μm or less. The depth of the coil formation trench 11 is preferably 10 μm or more so that the internal resistance of the coil 3 formed within the coil formation trench 11 is decreased.

As shown in FIG. 79 , the coil formation trench 11 is formed with a first trench part 11 a that is formed in the insulating film 7 and a second trench part 11 b that is formed in the substrate main body 6 and that communicates with the first trench part 11 a . On the inner surface of the coil formation trench 11 (the second trench part 11 b ) in the substrate main body 6 , an insulating film 12 formed with an oxide film or the like is formed. In the preferred embodiment, the insulating film 12 is formed with a thermal oxide film (SiO 2 ), and when the thermal oxide film is formed on the inner surface of the coil formation trench 11 , the surrounding wall (the side wall and the bottom wall) of the coil formation trench 11 (the second trench part 11 b ) in the substrate main body 6 is thermally oxidized into an insulator portion (thermal oxide film) 30 having insulation. In the preferred embodiment, an example is described where the entire wall sandwiched by the coil formation trench 11 (the second trench part 11 b ) in the shape of a spiral in the substrate main body 6 is a thermal oxide film.

On the surface of the insulating film 12 within the coil formation trench 11 (the second trench part 11 b ) and on the inner surface of the coil formation trench 11 (the first trench part 11 a ) in the insulating film 7 , a barrier metal film 13 is formed. The barrier metal film 13 is formed of, for example, TiN. The thickness of the barrier metal film 13 is about 400 to 500 angstroms. Within the coil formation trench 11 , a conductive member 51 is embedded while being in contact with the barrier metal film 13 . In the preferred embodiment, the conductive member 51 is formed of tungsten (W). The coil 3 is formed with the conductive member 51 embedded within the coil formation trench 11 . Hence, the coil 3 is formed, in plan view, in the shape of a spiral (in the shape of a quadrilateral spiral) of the same pattern as the coil formation trench 11 . Specifically, the coil 3 includes a plurality of plate-shaped parts parallel to the side surfaces 2 c of the substrate 2 .

On the element formation surface 2 a (the surface of the insulating film 7 ) of the substrate 2 , a wiring 31 in the shape of a spiral in plan view that is formed so as to extend along the coil 3 and cover the coil 3 is formed. The width of the wiring 31 is greater than that of the coil 3 , and both side portions thereof are extended outward as compared with both sides of the coil 3 . The wiring 31 is in contact with the upper end portion of the coil 3 . The wiring 31 is formed of, for example, Al.

On the element formation surface 2 a of the substrate 2 , an insulating film 32 is formed so as to coat the element formation surface 2 a and the wiring 31 . The insulating film 32 is formed, in plan view, in the shape of a rectangle matching with the element formation surface 2 a . The insulating film 32 is formed with, for example, a USG (Undoped Silicate Glass) film. In the insulating film 32 , a first contact hole 14 (see FIGS. 77 and 80 ) that exposes one end portion (outer peripheral side end portion) of the wiring 31 and a second contact hole 15 (see FIGS. 77 and 78 ) that exposes the other end portion (inner peripheral side end portion) of the wiring 31 are formed. As described above, in the side surfaces 2 c of the substrate 2 and the outer peripheral surface of the insulating film 32 , the passivation film 9 formed with a nitride film or the like is formed.

On the surface of the insulating film 32 , the first electrode 4 and the second electrode 5 are formed. The first electrode 4 includes a first electrode film 4 A that is formed on the surface of the insulating film 32 and a first external connection electrode 4 B that is bonded to the first electrode film 4 A. As shown in FIG. 77 , the first electrode film 4 A includes a drawing electrode 4 Aa that is connected to one end portion of the wiring 31 and a first pad 4 Ab that is formed integrally with the drawing electrode 4 Aa. The first pad 4 Ab is formed to be rectangular at one end portion of the element formation surface 2 a . The first external connection electrode 4 B is connected to the first pad 4 Ab. As shown in FIGS. 77 and 80 , the drawing electrode 4 Aa enters the first contact hole 14 from the surface of the insulating film 32 , and is connected to one end portion of the wiring 31 within the first contact hole 14 . The drawing electrode 5 Aa is formed straight along a straight line that passes above one end portion of the wiring 31 to reach the first pad 4 Ab.

By extending one end portion of the coil formation trench 11 to a position below the first pad 4 Ab, one end portion of the coil 3 (the wiring 31 ) may be disposed in a position below the first pad 4 Ab. In this way, since the first contact hole 14 can be formed in a position below the first pad 4 Ab, one end portion of the coil 3 (the wiring 31 ) can be connected to the first pad 4 Ab. In this case, since the first electrode film 4 A can be formed with only the first pad 4 Ab, the drawing electrode 4 Aa is not needed.

The second electrode 5 includes a second electrode film 5 A that is formed on the surface of the insulating film 32 and a second external connection electrode 5 B that is bonded to the second electrode film 5 A. As shown in FIG. 77 , the second electrode film 5 A includes a drawing electrode 5 Aa that is connected to the other end portion of the wiring 31 and a second pad 5 Ab that is formed integrally with the drawing electrode 5 Aa. The second pad 5 Ab is formed to be rectangular at the other end portion of the element formation surface 2 a . The second external connection electrode 5 B is connected to the second pad 5 Ab. As shown in FIGS. 77 and 78 , the drawing electrode 5 Aa enters the second contact hole 15 from the surface of the insulating film 32 , and is connected to the other end portion of the wiring 31 within the second contact hole 15 . The drawing electrode 5 Aa is formed straight along a straight line that passes above the other end portion of the wiring 31 to reach the second pad 5 Ab. In the preferred embodiment, as the electrode films 4 A and 5 A, Al films are used.

The first electrode film 4 A and the second electrode film 5 A are covered by a passivation film 16 formed with, for example, a nitride film (SiN), and furthermore, on the passivation film 16 , a resin film 17 such as polyimide is formed. In the passivation film 16 and the resin film 17 , two cutout portions 18 and 19 are formed that respectively expose a region other than an edge portion on the inner side of the surface of the first pad 4 Ab of the first electrode film 4 A and a region other than an edge portion on the inner side of the surface of the second pad 5 Ab of the second electrode film 5 A. In other words, the passivation film 16 and the resin film 17 are formed, in plan view, in a region corresponding to the coil formation region 10 C of the element formation surface 2 a , and cover the insulating film 32 , the edge portion on the inner side of the surface of the first pad 4 Ab, and the edge portion on the inner side of the surface of the second pad 5 Ab.

The first external connection electrode 4 B fills the cutout portion 18 , and the second external connection electrode 5 B fills the cutout portion 19 . The first external connection electrode 4 B and the second external connection electrode 5 B are formed so as to protrude from the resin film 17 , and include a drawing portion 20 that is drawn inwardly of the substrate 2 along the surface of the resin film 17 . In the preferred embodiment, the first external connection electrode 4 B is formed so as to cover not only the surface of the first electrode film 4 A (the pad 4 Ab) and the insulating film 32 exposed within the cutout portion 18 but also the upper end surface of the passivation film 9 on the side of one end portion of the substrate 2 . The three side surfaces other than the side surface on the inner side of the first external connection electrode 4 B are formed so as to be flush with the surface of the passivation film 9 covering the peripheral surface of the insulating film 32 on the side of one end portion of the substrate 2 .

Likewise, the second external connection electrode 5 B is formed so as to cover not only the surface of the second electrode film 5 A (the pad 5 Ab) and the insulating film 32 exposed within the cutout portion 19 but also the upper end surface of the passivation film 9 on the side of the other end portion of the substrate 2 . The three side surfaces other than the side surface on the inner side of the second external connection electrode 5 B are formed so as to be flush with the surface of the passivation film 9 covering the peripheral surface of the insulating film 32 on the side of the other end portion of the substrate 2 . The external connection electrodes 4 B and 5 B may be, for example, formed with a Ni/Pd/Au laminated film having a Ni film in contact with the electrode films 4 A and 5 A, a Pd film formed thereon, and an Au film formed thereon. The laminated film described above can be formed by a plating method.

The passivation film 16 and the resin film 17 coat, from the surface, the coil 3 , the insulating film 32 , the first electrode film 4 A, and the second electrode film 5 A in the coil formation region 10 C of the element formation surface 2 a , and function as a protective film to protect them. On the other hand, the passivation film 9 formed on the side surfaces 2 c of the substrate 2 and the outer peripheral surface of the insulating film 32 function as a protective film to protect the side surfaces 2 c of the substrate 2 and the outer peripheral surface of the insulating film 32 .

FIG. 83 is an electrical circuit diagram showing an electrical structure within the chip inductor 1 C. One end of the coil 3 (represented by a symbol L in FIG. 83 ) is connected to the first electrode 4 , and the other end of the coil 3 is connected to the second electrode. In this way, the chip inductor functions as an inductor having a predetermined inductance.

As a parameter indicating the performance (quality) of the coil, the Q (Quality Factor) value of the coil is present. As the Q value is increased, its loss is decreased, and an excellent characteristic is provided as a high-frequency inductance.

The Q value of the coil 3 is represented by formula (4) below.

Q= 2π fL/R   (4)

In the formula (4) above, f represents the frequency of a current flowing through the coil, L represents the inductance of the coil 3 , and R represents the internal resistance of the coil 3 .

In the arrangement of the fourth preferred embodiment of the second invention, in the substrate 2 , the coil formation trench 11 obtained by digging down from the element formation surface 2 a is formed, in plan view, in the shape of a spiral, the conductive member 51 is embedded within the coil formation trench 11 and thus the coil 3 is formed. Hence, it is possible to increase the cross-sectional area of the coil 3 (the cross-sectional area of the coil 3 perpendicular to the direction in which the coil 3 is extended in the spiral direction), and thus it is possible to decrease the internal resistance (R in the formula (4) above) of the coil 3 . In this way, since the Q value of the coil 3 can be increased, it is possible to provide a high-performance chip inductor.

The coil formation trench 11 is formed in the substrate 2 , the conductive member 51 is embedded within the coil formation trench 11 and thus it is possible to form the coil 3 , with the result that the coil 3 is easily manufactured. In this way, it is possible to provide a chip transformer that is easily manufactured.

In the fourth preferred embodiment of the second invention, the chip inductor 1 C is formed on the element formation surface 2 along the coil 3 , and includes the wiring 31 in contact with the upper end portion of the coil 3 . Hence, even when an area is produced where the conductive member 51 is unsatisfactorily embedded within the coil formation trench 11 , it is possible to compensate for the area with the wiring 31 . In this way, even when the conductive member 51 is unsatisfactorily embedded within the coil formation trench 11 , and thus a break is produced halfway along the coil 3 , the break can be connected by the wiring 31 .

Furthermore, on the element formation surface 2 a , which is one surface of the substrate 2 , both the external connection electrodes 4 B and 5 B of the first electrode 4 and the second electrode 5 are formed. Hence, as shown in FIG. 84 , the element formation surface 2 a is made to face a mounting substrate 91 , the external connection electrodes 4 B and 5 B are bonded on the mounting substrate 91 by a solder 92 and thus it is possible to form a circuit assembly in which the chip inductor 1 C is surface-mounted on the mounting substrate 91 . In other words, it is possible to provide a flip-chip connection-type chip inductor 1 C, and it is possible to connect the chip inductor 1 C to the mounting substrate 91 by a face-down bonding in which the element formation surface 2 a is made to face the mounting substrate 91 and wireless bonding. In this way, it is possible to decrease the occupied space of the chip inductor 1 C on the mounting substrate 91 . In particular, it is possible to realize a low profile chip inductor 1 C on the mounting substrate 91 . In this way, it is possible to effectively utilize the space within the housing of a small-sized electronic device or the like and to contribute to high-density mounting and miniaturization.

FIGS. 85A to 85M are cross-sectional views for illustrating an example of the manufacturing step of the chip inductor 1 C, and show cut surfaces corresponding to FIG. 78 . FIGS. 86A to 86F are partially enlarged cross-sectional views showing the details of the manufacturing step of a coil, and show cut surfaces corresponding to FIG. 79 .

As shown in FIG. 85A , first, an original substrate 50 that is an original of the substrate main body 6 is prepared. On the surface of the original substrate 50 , the insulating film 7 such as a thermal oxide film or a CVD oxide film is formed. In the preferred embodiment, the insulating film 7 is a thermal oxide film. The surface of the insulating film 7 corresponds to the element formation surface 2 a of the substrate 2 .

FIG. 87 is a schematic plan view of part of the original substrate 50 in which the insulating film 7 is formed on the surface. As shown in FIG. 87 , in the element formation surface 2 a , chip inductor regions X corresponding to a plurality of chip inductors 1 C are disposed in a matrix. Between the chip inductor regions X adjacent to each other, a boundary region Y is provided. The boundary region Y is a region in the shape of a band having a substantially constant width, extends in two directions perpendicular to each other and is formed in a lattice shape. After necessary steps are performed on the original substrate 50 in which the insulating film 7 is formed on the surface, the original substrate 50 is separated along the boundary region Y, and thus it is possible to obtain a plurality of chip inductors 1 C.

The steps performed on the original substrate 50 in which the insulating film 7 is formed on the surface are as follows. First, by photolithography and etching, a part of the insulating film 7 that corresponds to a region in which the coil formation trench 11 needs to be formed is removed. In this way, in the insulating film 7 , the first trench part 11 a is formed. Then, a hard mask formed with the insulating film 7 is used, and thus the original substrate 50 is etched. In this way, as shown in FIGS. 85B and 86A , the second trench part 11 b is formed in the original substrate 50 . In this way, in the insulating film 7 and the original substrate 50 , the coil formation trench 11 formed with the first trench part 11 a and the second trench part 11 b is formed. The coil formation trench 11 may be formed by, for example, a so-called BOSCH process. The BOSCH process is a process that is generally used to make a hollow part in a MEMS (Micro Electro Mechanical System).

Then, as shown in FIGS. 85B and 86B , on the inner surface of the coil formation trench 11 , the insulating film (thermal oxide film) 12 is formed by a thermal oxidization method. Here, the surrounding wall (the side wall and the bottom wall) of the coil formation trench 11 (the second trench part 11 b ) in the original substrate 50 is thermally oxidized into an insulator portion (thermal oxide film) 30 having insulation. In FIG. 85B , the insulating film 12 is omitted but the insulator portion 30 is shown. In the preferred embodiment, the entire wall sandwiched by the coil formation trench 11 (the second trench part 11 b ) in the shape of a spiral in the original substrate 50 is formed into the thermal oxide film.

Then, for example, by a sputtering method, the barrier metal film 13 made of TiN is formed on the element formation surface 2 a including the interior of the coil formation trench 11 . In this way, then, as shown in FIG. 86C , the barrier metal film 13 is formed on the surfaces of the insulating film 12 and the insulating film 7 within the coil formation trench 11 and the surface of the insulating film 7 outside the coil formation trench 11 . Thereafter, annealing processing is performed. Thereafter, as shown in FIGS. 85C and 86D , for example, by a CVD method, on the element formation surface 2 a including the interior of the coil formation trench 11 , the conductive member 51 formed of tungsten (W) is deposited.

Then, for example, by an etch back method, overall etching is performed on the conductive member 51 from its surface. The overall etching is continued until the surface of the conductive member 51 is flush with the surface of the insulating film 7 . In this way, as shown in FIGS. 85D and 86E , the conductive member 51 is embedded within the coil formation trench 11 while in contact with the barrier metal film 13 . By the conductive member 51 embedded within the coil formation trench 11 , the coil 3 in the shape of a spiral when seen in plan view is formed.

Then, for example, by sputtering, on the insulating film 7 (the element formation surface 2 a ), a wiring film for the formation of the wiring 31 is formed. In the preferred embodiment, the wiring film made of Al is formed. Thereafter, by photolithography and etching, the wiring film is patterned, and thus as shown in FIGS. 85E and 86F , the wiring 31 is formed on the coil 3 . The wiring 31 is formed, in plan view, in the shape of a spiral of substantially the same pattern as the coil 3 and is in contact with the upper end portion of the coil 3 .

Then, as shown in FIG. 85F , on the element formation surface 2 a , the insulating film 32 formed with a USG (Undoped Silicate Glass) film or the like is formed so as to coat the element formation surface 2 a and the wiring 31 . The insulating film 32 is formed by, for example, a CVD method. Thereafter, by photolithography and etching, in regions of the insulating film 32 corresponding to one end portion and the other end portion of the wiring 31 , the first contact hole 14 (see FIG. 80 ) and the second contact hole 15 (see FIG. 85F ) penetrating the insulating film 32 are respectively formed.

Then, for example, by sputtering, on the insulating film 32 including the interiors of the contact holes 14 and 15 , an electrode film forming the first electrode 4 and the second electrode 5 is formed. In the preferred embodiment, the electrode film made of Al is formed. Thereafter, by photolithography and etching, the electrode film is patterned, and thus as shown in FIG. 85G , the electrode film is separated into the first electrode film 4 A and the second electrode film 5 A.

Then, as shown in FIG. 85H , for example, by a CVD method, the passivation film 16 such as a nitride film is formed, and furthermore, polyimide is applied to form the resin film 17 . For example, polyimide to which photosensitivity is added is applied, and the polyimide is developed after exposure with a pattern corresponding to the cutout portions 18 and 19 . In this way, the resin film 17 having a cutout portion corresponding to the cutout portions 18 and 19 is formed. Thereafter, as necessary, heat treatment for curing the resin film is performed. Then, by dry etching using the resin film 17 as a mask, the cutout portions 18 and 19 are formed in the passivation film 16 .

Then, as shown in FIG. 85I , a resist mask 52 having an opening 52 a in a lattice shape matching with the boundary region Y (see FIG. 87 ) is formed. Plasma etching is performed via the resist mask 52 , and thus as shown in FIG. 85I , the original substrate 50 , the insulating film 7 , and the insulating film 32 are etched from the surface of the insulating film 32 to a predetermined depth. In this way, along the boundary region Y, a groove (scribe groove) 53 for cutting is formed.

Then, the resist mask 52 is peeled off. Thereafter, as shown in FIG. 85J , for example, by a CVD method, an insulating film 54 formed with a nitride film or the like serving as the material of the passivation film 9 is formed over the entire region of the surface of the original substrate 50 . Here, the insulating film 54 is also formed over the entire region of the inner surface (the side wall surface and the bottom wall surface) of the groove 53 .

Then, as shown in FIG. 85K , the insulating film 54 is selectively etched. Specifically, a part of the insulating film 54 other than the insulating film 54 (the passivation film 9 ) on the side wall surface of the groove 53 is removed. In this way, a part of the electrode films 4 A and 5 A that is not covered by the passivation film 16 and the resin film 17 is exposed. The insulating film 54 on the bottom surface of the groove 53 is removed.

Then, as shown in FIG. 85L , on the first electrode film 4 A (the first pad 4 Ab) and the second electrode film 5 A (the second pad 5 Ab) exposed from the cutout portions 18 and 19 , for example, by plating (preferably, electroless plating), plating growth is performed in the following order: for example, Ni, Pd and Au. In this way, the first external connection electrode 4 B and the second external connection electrode 5 B are formed.

Thereafter, by a DBG (Dicing Before Grinding) method, a plurality of chip inductor regions X are divided into pieces. Specifically, as shown in FIG. 85M , first, on the side of the surface of the original substrate 50 (the side of the external connection electrode), a supporting tape 71 having an adhesive surface 72 is adhered. Then, the original substrate 50 is polished from the rear surface to the bottom surface of the groove 53 . In this way, the plurality of chip inductor regions X are separated into individual chip inductors 1 C. Thereafter, on a plurality of chip inductors 1 C, the recovery step shown in FIGS. 45A to 45D or the recovery step shown in FIGS. 46A to 46C described in the first preferred embodiment of the second invention may be performed.

FIGS. 88A and 88B are cross-sectional views showing a modification example of the external connection electrode for the chip inductor 1 C of the fourth preferred embodiment of the second invention. FIG. 88A shows a cut surface corresponding to FIG. 78 , and FIG. 88B shows a cut surface corresponding to FIG. 81 . In FIGS. 88A and 88B , the portions corresponding to the portions of FIGS. 78 and 81 described previously are provided with the same symbols of FIGS. 78 and 81 .

The first external connection electrode 4 B fills one cutout portion 18 in the passivation film 16 and the resin film 17 , and the second external connection electrode 5 B fills the other cutout portion 19 .

The first external connection electrode 4 B is formed so as to cover the upper portion of the passivation film 9 on the side of one end portion of the substrate 2 and to straddle, from the peripheral portion of the surface of the insulating film 32 , the surface of the passivation film 9 covering the three side surfaces 2 c on the side of one end portion of the substrate 2 . In other words, the first external connection electrode 4 B is formed so as to cover not only the surface of the first electrode film 4 A (the pad 4 Ab) and the insulating film 32 exposed within the cutout portion 18 but also the passivation film 9 on the three side surfaces 2 c of the substrate 2 .

Likewise, the second external connection electrode 5 B is formed so as to cover the upper portion of the passivation film 9 on the side of the other end portion of the substrate 2 and to straddle, from the peripheral portion of the surface of the insulating film 32 , the surface of the passivation film 9 covering the three side surfaces 2 c on the side of the other end portion of the substrate 2 . In other words, the second external connection electrode 5 B is formed so as to cover not only the surfaces of the second electrode film 5 A (the pad 5 Ab) and the insulating film 32 exposed within the cutout portion 19 but also the passivation film 9 on the three side surfaces 2 c on the side of the other end portion of the substrate 2 .

As described above, in the chip inductor 1 C, the first external connection electrode 4 B is formed so as to cover the three side surfaces 2 c on the side of one end portion of the substrate 2 , and the second external connection electrode 5 B is formed so as to cover the three side surfaces 2 c on the side of the other end portion of the substrate 2 . In other words, the external connection electrodes 4 B and 5 B are formed not only on the element formation surface 2 a on the substrate 2 but also on the side surfaces 2 c of the substrate 2 . In this way, in the form shown in FIG. 84 described previously, when the external connection electrodes 4 B and 5 b of the chip inductor 1 C are soldered to the mounting substrate, it is possible to increase the bonding area between the external connection electrodes 4 B, and 5 B and the mounting substrate. Consequently, it is possible to enhance the bonding strength of the external connection electrodes 4 B and 5 B on the mounting substrate.

Even in the fourth preferred embodiment of the second invention, as in the second preferred embodiment of the second invention, in the step of forming the coil formation trench 11 , the electrode-side trench (concave portion formation trench) 21 may be formed in only one of the first and second electrode formation regions 10 A and 10 B. Thus, in any one of the first electrode 4 (the first external connection electrode 4 B) and the second electrode 5 (the second external connection electrode 5 B), the concave portions 84 can be formed on the surface. In this way, it is possible to easily determine the polarity direction of the chip inductor.

Even in the fourth preferred embodiment of the second invention, as in the third preferred embodiment of the second invention, in the step of forming the coil formation trench 11 , the first and second electrode-side trenches 21 A and 21 B may be formed in the first and second electrode formation regions 10 A and 10 B. Thus, substantially the entire region of the part of the substrate 2 opposite the first electrode 4 and the part of the substrate 2 opposite the second electrode 5 can be formed into an insulator portion having insulation. In this way, it is possible to reduce the parasitic capacitance formed between the substrate main body 6 and the first electrode 4 , and the second electrode 5 opposite each other through the insulating film 7 as compared with the case where a main body substrate (semiconductor substrate) having no insulator portion is used.

Even in the fourth preferred embodiment of the second invention, the structure of the conductive member 51 embedded within the coil formation trench 11 may be the structure shown in FIGS. 48A and 48B described as the modification example of the conductive member 51 of the first preferred embodiment of the second invention.

Although the first to fourth preferred embodiments of the second invention and a preferred embodiment of the third invention are described above, the second invention and the third invention can be carried out with still other preferred embodiments. For example, although in the preferred embodiments described above, the coil 3 is formed with one coil formed in the shape of a spiral in plan view, the coil 3 may be formed with a plurality of coils parallel to each other (parallel coils). In this case, one end portion of the plurality of parallel coils is connected to the first electrode, and the other end portion of the plurality of parallel coils is connected to the second electrode.

FIG. 89 shows a chip inductor 1 D that is formed with two coils 3 A and 3 B parallel to each other. In FIG. 89 , portions corresponding to the portions of FIG. 34 described previously are provided with the same symbols of FIG. 34 .

In the chip inductor 1 D, in the substrate 2 , two coil formation trenches 11 A and 11 B parallel to each other are formed in the shape of a spiral. The coils 3 A and 3 B are formed with the conductive members 51 embedded in the coil formation trenches 11 A and 11 B. One end portion of the two coils 3 A and 3 B is connected to the first electrode film 4 A of the first electrode 4 , and the other end portion of the coils 3 A and 3 B is connected to the second electrode film 5 A of the second electrode 5 .

FIG. 90 is an electrical circuit diagram showing an electrical structure within the chip inductor 1 D. In FIG. 90 , one coil 3 A is represented by L 1 , and the other coil 3 B is represented by L 2 . One ends of the two coils 3 A and 3 B are connected together to the first electrode 4 , and the other ends of the two coils 3 A and 3 B are connected together to the second electrode 5 . In other words, between the first electrode 4 and the second electrode, the two coils 3 A and 3 B are connected in parallel. In this way, they collectively function as one inductor.

When it is assumed that the inductance of the one coil 3 A is L 1 and the inductance of the other coil 3 B is L 2 , the inductance L of the coil 3 is represented by formula (5) below.

L =( L 1× L 2)/( L 1+ L 2)  (5)

The Q value of the coil 3 is represented by formula (6) below.

Q= 2π fL/R   (6)

In the formula (6) above, f represents the frequency of a current flowing through the coil, L represents the inductance of the coil 3 , and R represents the internal resistance of the coil 3 .

In the chip inductor 1 D, as compared with a case where the coil 3 is formed with one coil, as the number of windings is reduced, the inductance L is reduced because the two coils are connected in parallel. However, since the internal resistance R is also reduced, it is possible to obtain a satisfactory Q value.

Although in the first to fourth preferred embodiments of the second invention and a preferred embodiment of the third invention described previously, the coil 3 (the coil formation trench 11 ) is formed, in plan view, in the shape of a quadrilateral spiral, as shown in FIG. 91 , the coil 3 (the coil formation trench 11 ) may be formed, in plan view, in the shape of a circular spiral. As shown in FIG. 92 , the coil 3 (the coil formation trench 11 ) may be formed in the shape of a polygonal spiral other than a quadrilateral such as an octagonal spiral in plan view.

The substrate 2 may be formed with a substrate made of a material having insulation.

[3] Fourth Invention

An object of the fourth invention is to provide a high performance chip transformer and a circuit assembly that includes it.

Another object of the fourth invention is to provide a method of manufacturing a high performance chip transformer.

The fourth invention has the following features.

C1. A chip transformer including: a substrate that has an element formation surface; a primary coil formation trench and a secondary coil formation trench that are formed in the substrate by digging down from the element formation surface and that are formed in the shape of a spiral in plan view when seen in a normal direction perpendicular to the element formation surface; a primary coil that is formed with a conductive member embedded within the primary coil formation trench; and a secondary coil that is formed with a conductive member embedded within the secondary coil formation trench.

Since in this arrangement, it is possible to increase the cross-sectional area of the primary coil (cross-sectional area perpendicular to a direction in which the primary coil is extended in the spiral direction), it is possible to decrease the internal resistance of the primary coil. Likewise, since it is possible to increase the cross-sectional area of the secondary coil (cross-sectional area perpendicular to a direction in which the secondary coil is extended in the spiral direction), it is possible to decrease the internal resistance of the secondary coil. In this way, it is possible to increase the Q (Quality Factor) value of the primary coil and the secondary coil, with the result that it is possible to provide a high performance chip transformer.

In the substrate, the primary coil formation trench and the secondary coil formation trench are formed, the conductive member is embedded within each of the coil formation trenches and thus it is possible to form the primary coil and the secondary coil, with the result that it is easy to manufacture the primary coil and the secondary coil. In this way, it is possible to provide a chip transformer that is easily manufactured.

C2. The chip transformer described in “C1” further including: a first electrode and a second electrode which are disposed on the element formation surface and to which one end portion and the other end portion of the primary coil are electrically connected; and a third electrode and a fourth electrode which are disposed on the element formation surface and to which one end portion and the other end portion of the secondary coil are electrically connected.

C3. A chip transformer described in “C1” or “C2,” where in the element formation surface, a primary side formation region and a secondary side formation region are provided and arrayed in one direction along the surface thereof, in the primary side formation region, the primary coil formation trench is formed and in the secondary formation region, the secondary coil formation trench is formed.

C4. A chip transformer described in “C3,” where the primary side formation region and the secondary side formation region are formed, in plan view, in the shape of a rectangle which is long in one direction, at one end portion of the primary side formation region, the first electrode is disposed, at the other end portion, the second electrode is disposed, at one end portion of the secondary side formation region, the third electrode is disposed, and at the other end portion, the fourth electrode is disposed.

C5. A chip transformer described in “C1” or “C2,” where the primary coil formation trench and the secondary coil formation trench are disposed, in plan view, such that in a gap of the one coil formation trench, the other coil formation trench is disposed. In this arrangement, the primary coil and the secondary coil can be disposed close to each other, and thus it is possible to provide a higher performance chip transformer.

C6. A chip transformer described in “C5,” where the element formation surface is formed, in plan view, in the shape of a rectangle, in a region between both side portions of the element formation surface, the primary coil formation trench and the secondary coil formation trench are formed, on the side of one end portion in one side portion of the element formation surface, the first electrode is disposed, on the side of the other end portion in the one side portion, the second electrode is disposed, on the side of one end portion in the other side portion of the element formation surface, the third electrode is disposed, and on the side of the other end portion in the other side portion, the fourth electrode is disposed.

C7. A chip transformer described in any one of “C2” to “C6” further including: an insulating film that is formed so as to cover the primary coil and the secondary coil on the element formation surface, that respectively includes a first contact hole and a second contact hole in regions corresponding to one end portion and the other end portion of the primary coil and that respectively includes a third contact hole and a fourth contact hole in regions corresponding to one end portion and the other end portion of the secondary coil, where the first electrode, the second electrode, the third electrode and the fourth electrode are formed on the insulating film, the first electrode is connected via the first contact hole to one end portion of the primary coil, the second electrode is connected via the second contact hole to the other end portion of the primary coil, the third electrode is connected via the third contact hole to one end portion of the secondary coil, and the fourth electrode is connected via the fourth contact hole to the other end portion of the secondary coil.

C8. A chip transformer described in any one of “C2” to “C7,” where a plurality of concave portions are formed in only the surface of any one of a primary side electrode pair formed with the first electrode and the second electrode and a secondary side electrode pair formed with the third electrode and the fourth electrode.

When image inspection is performed on the chip transformer, light from a light source is applied to the surfaces of the individual electrodes, and images of the surfaces are imaged with a camera. In this arrangement, although a plurality of concave portions are formed in the surface of one of the primary side electrode pair and the secondary side electrode pair, a plurality of concave portions are not formed in the surface of the other electrode pair. The light incident on the surface of the electrode pair where concave portions are formed is diffusely reflected off the concave portions. On the other hand, the light incident on the surface of the electrode pair where concave portions are not formed are unlikely to be diffusely reflected off. Hence, a large difference is produced between image information (for example, brightness information) on the primary side electrode pair and image information on the secondary side electrode pair obtained with the camera. In this way, based on the image information obtained with the camera, it is possible to clearly identify the primary side electrode pair and the secondary side electrode pair. In other words, in this arrangement, at the time of the image inspection, it is possible to easily determine the primary side electrode pair and the secondary side electrode pair.

C9. A chip transformer described in “C8,” where a first underlying concave portion is formed, in plan view, in the element formation surface of the substrate in the same position as the position in which the concave portion is formed.

In this arrangement, the first underlying concave portion is formed in the element formation surface of the substrate, and thus the concave portion can be formed in the surface of any one of the primary side electrode pair and the secondary side electrode pair formed on the element formation surface. In other words, the first underlying concave portion is formed in the element formation surface of the substrate, and thus the concave portion can be formed in the surface of any one of the primary side electrode pair and the secondary side electrode pair without adding a step separately forming the concave portion in the surface of any one of the primary side electrode pair and the secondary side electrode pair.

C10. A chip transformer described in “C9” further including an insulating film formed between the element formation surface and the first to fourth electrodes, where a second underlying concave portion is formed, in plan view, in the surface of the insulating film in the same position as the position in which the first underlying concave portion is formed.

In this arrangement, the first underlying concave portion is formed in the element formation surface of the substrate, and thus in the surface of the insulating film formed on the element formation surface, the second underlying concave portion can be formed. The second underlying concave portion is formed in the surface of the insulating film, and thus the concave portion can be formed in the surface of any one of the primary side electrode pair and the secondary side electrode pair formed on the insulating film.

C11. A chip transformer described in “C9” or “C10,” where the plurality of concave portions are formed, per electrode in which the plurality of concave portions are formed, in plan view, in the shape of a straight line extending in one direction, are disposed at an interval in a direction perpendicular to the one direction and includes, in plan view, in the same positions as the positions in which the concave portions are formed on the element formation surface, by digging down from the element formation surface, a plurality of concave portion formation trenches formed in the substrate and conductive members embedded within the concave formation trenches, and in the surface of the conductive member within the concave formation trenches, the first underlying concave portion is formed.

In this arrangement, the plurality of concave formation trenches are formed in the substrate, and the conductive member is embedded within the concave formation trenches, with the result that it is possible to form the first underlying concave portion.

C12. A chip transformer described in “C11,” where the plurality of concave formation trenches are formed in the same step as the coil formation trenches. In this arrangement, since the concave formation trenches can be formed in the same step as the coil formation trenches, it is possible to reduce the number of manufacturing steps.

C13. The chip transformer described in any one of “C1” to “C12,” where a depth of the coil formation trench is 10 μm or more. In this arrangement, it is possible to increase the cross-sectional areas of the primary coil and the secondary coil, and thus it is possible to decrease the internal resistance of the primary coil and the secondary coil. In this way, it is possible to increase the Q value of the primary coil and the secondary coil.

C14. The chip transformer described in any one of “C1” to “C12,” where a depth of the coil formation trench is 10 μm or more and 82 μm or less.

C15. The chip transformer described in any one of “C1” to “C14,” where a width of the coil formation trench is 1 μm or more and 3 μm or less.

C16. A circuit assembly including: a mounting substrate; and the chip transformer described in any one of “C1” to “C15” mounted in the mounting substrate. In this arrangement, it is possible to provide a circuit assembly using a high performance chip inductor.

C17. The circuit assembly described in “C16,” where the chip transformer is connected to the mounting substrate by wireless bonding. In this arrangement, it is possible to decrease the occupied space of the chip transformer on the mounting substrate, and thus it is possible to contribute to the high-density mounting of electronic parts.

C18. A method of manufacturing a chip transformer, the method including: a first step of forming, in a substrate having an element formation surface, by digging down from the element formation surface, a primary coil formation trench and a secondary coil formation trench in the shape of a spiral in plan view when seen in a normal direction perpendicular to the element formation surface; and a second step of embedding a conductive member within the primary coil formation trench and the secondary coil formation trench to form a primary coil within the primary coil formation trench and a secondary coil within the secondary coil formation trench.

In the manufacturing method of the present invention, within the primary coil formation trench and secondary coil formation trench formed in the substrate, the primary coil and the secondary coil can be respectively formed. Hence, it is possible to provide a chip transformer having the same effects as described in “C1” described previously.

C19. The method of manufacturing a chip transformer described in “C18,” the method further including: a third step of forming an insulating layer on the element formation surface so as to coat the primary coil and the secondary coil; a fourth step of forming, in the insulating layer, a first contact hole that exposes one end portion of the primary coil, a second contact hole that exposes the other end portion of the primary coil, a third contact hole that exposes one end portion of the secondary coil, and a fourth contact hole that exposes the other end portion of the secondary coil; and a fifth step of forming, on the insulating film, a first electrode that is in contact with the one end portion of the primary coil via the first contact hole, a second electrode that is in contact with the other end portion of the primary coil via the second contact hole, a third electrode that is in contact with the one end portion of the secondary coil via the third contact hole, and a fourth electrode that is in contact with the other end portion of the secondary coil via the fourth contact hole.

In this manufacturing method, it is possible to form, on the insulating film formed on the element formation surface, the first electrode to which the one end portion of the primary coil is connected, the second electrode to which the other end portion of the primary coil is connected, the third electrode to which the one end portion of the secondary coil is connected, and the fourth electrode to which the other end portion of the secondary coil is connected.

Preferred embodiments of the fourth invention will be described in detail with reference to FIGS. 93A to 144F . The symbols in FIGS. 93A to 144F are not related to the symbols in FIGS. 1 to 92 used in the description of the first to third inventions discussed previously.

FIG. 93A is a partially cut perspective view of a chip transformer according to a first preferred embodiment of the fourth invention, and FIG. 93B is a perspective view showing the primary coil and the secondary coil formed within the chip transformer.

The chip transformer 1 is a minute chip part and is formed in the shape of a rectangular parallelepiped. The planar shape of the chip transformer 1 may be rectangular, the length L of one of adjacent two sides may be about 0.4 mm, and the length W of the other side may be about 0.4 mm. The thickness T of the entire chip transformer 1 may be about 0.15 mm.

The chip transformer 1 includes a substrate 2 , a primary coil 3 A and a secondary coil 3 B that are formed within the substrate 2 , a first electrode 41 that is connected to one end portion of the primary coil 3 A, a second electrode 42 that is connected to the other end portion of the primary coil 3 A, a third electrode 43 that is connected to one end portion of the secondary coil 3 B, and a fourth electrode 44 that is connected to the other end of the secondary coil 3 B. The number of windings of the primary coil 3 A differs from the number of windings of the secondary coil 3 B. Although in the preferred embodiment, an example where the number of windings of the primary coil 3 A is greater than the number of windings of the secondary coil 3 B is described, the number of windings of the secondary coil 3 B may be greater than the number of windings of the primary coil 3 A.

FIG. 94 is a plan view of the chip transformer, FIG. 95A is a cross-sectional view taken along line XCVA-XCVA in FIG. 94 , FIG. 95B is a partially enlarged cross-sectional view of FIG. 95A . FIG. 96A is a cross-sectional view taken along line XCVIA-XCVIA in FIG. 94 , and FIG. 96B is a partially enlarged cross-sectional view of FIG. 96A . FIG. 97 is a cross-sectional view taken along line XCVII-XCVII in FIG. 94 , and FIG. 98 is a cross-sectional view taken along line XCVIII-XCVIII in FIG. 94 . FIG. 99 is a plan view showing a structure of the surface of a substrate by removing an arrangement formed on the surface of the substrate.

In the following description, the “front” refers to the lower side of the plane of FIG. 94 , the “back” refers to the upper side of the plane of FIG. 94 , the “left” refers to the left side of the plane of FIG. 94 , and the “right” refers to the right side of the plane of FIG. 94 .

The substrate 2 is formed in the shape of a rectangular parallelepiped, and includes a pair of main surfaces 2 a and 2 b and four side surfaces 2 c . One (the main surface 2 a on the upper surface side in FIG. 93A ) of the pair of main surfaces 2 a and 2 b is an element formation surface. In the following description, the main surface 2 a is referred to as an “element formation surface 2 a ,” and the main surface 2 b on the side opposite to the element formation surface 2 a is referred to as a “rear surface 2 b .” In the preferred embodiment, the substrate 2 is formed with a substrate main body 6 and an insulating film 7 formed on the surface thereof, and the surface of the insulating film 7 on the side opposite to the side of the substrate main body 6 is the element formation surface 2 a . In the preferred embodiment (the same is true in the other preferred embodiments of the fourth invention), the substrate main body 6 is formed with a silicon substrate, and the insulating film 7 is formed with a thermal oxide film (SiO 2 ). The element formation surface 2 a is formed in the shape of a rectangle in plan view when seen in a normal direction perpendicular to the element formation surface 2 a . The surface (element formation surface 2 a ) of the substrate 2 is covered by an insulating film 8 . The four side surfaces 2 c of the substrate 2 and the outer peripheral surface of the insulating film 8 are covered by a passivation film 9 such as a nitride film.

With reference to FIGS. 94 and 99 , in the front half of the element formation surface 2 a , a primary side formation region 45 for the formation of the primary side circuit of the transformer is provided, and in the back half, a secondary side formation region 46 for the formation of the secondary side circuit of the transformer is provided. Each of the regions 45 and 46 is formed, in plan view, in the shape of a rectangle which is long in a left/right direction. In one end portion (left side end portion) of the primary side formation region 45 , a first electrode formation region 45 A is provided, and in the other end portion (right side end portion), a second electrode formation region 45 B is provided. In one end portion (left side end portion) of the secondary side formation region 46 , a third electrode formation region 46 A is provided, and in the other end portion (right side end portion), a fourth electrode formation region 46 B is provided.

In the first electrode formation region 45 A, the external connection electrode (first external connection electrode) 41 B of the first electrode 41 is disposed, and in the second electrode formation region 45 B, the external connection electrode (second external connection electrode) 42 B of the second electrode 42 is disposed. The first external connection electrode 41 B is rectangular in plan view, and covers the region of the first electrode formation region 45 A other than an edge portion on the side of the third electrode formation region 46 A. The second external connection electrode 42 B is rectangular in plan view, and covers the region of the second electrode formation region 45 B other than an edge portion on the side of the fourth electrode formation region 46 B. On the element formation surface 2 a between the external connection electrodes 41 B and 42 B, a primary coil formation region 45 C is provided. In the preferred embodiment, the primary coil formation region 45 C is formed in the shape of a rectangle.

In the third electrode formation region 46 A, the external connection electrode (third external connection electrode) 43 B of the third electrode 43 is disposed, and in the fourth electrode formation region 46 B, the external connection electrode (fourth external connection electrode) 44 B of the fourth electrode 44 is disposed. The third external connection electrode 43 B is rectangular in plan view, and covers the region of the third electrode formation region 46 A other than an edge portion on the side of the first electrode formation region 45 A. The fourth external connection electrode 44 B is rectangular in plan view, and covers the region of the fourth electrode formation region 46 B other than an edge portion on the side of the second electrode formation region 45 B. On the element formation surface 2 a between the external connection electrodes 43 B and 44 B, a secondary coil formation region 46 C is provided. In the preferred embodiment, the secondary coil formation region 46 C is formed in the shape of a rectangle.

With reference to FIGS. 94, 95A, 95B, 97 and 99 , in the substrate 2 , the coil formation trench 11 A is formed by digging down, in the primary coil formation region 45 C, to a predetermined depth from the element formation surface 2 a . The primary coil formation trench 11 A is formed, in plan view, in the shape of a spiral. In the preferred embodiment, the primary coil formation trench 11 A is formed, in plan view, in the shape of a quadrilateral spiral, and has a plurality of rectilinear portions parallel to the side surfaces 2 c of the substrate 2 .

The cross section (cross section in a direction perpendicular to a direction in which the primary coil formation trench 11 A is extended in the spiral direction) of the primary coil formation trench 11 A is formed in the shape of a rectangle which is long in the direction of the thickness of the substrate 2 . For example, the width of the primary coil formation trench 11 A may be 1 μm or more and 3 μm or less. For example, the depth of the primary coil formation trench 11 A may be 10 μm or more and 82 μm or less. The depth of the primary coil formation trench 11 A is preferably 10 μm or more so that the internal resistance of the primary coil 3 A formed within the primary coil formation trench 11 A is decreased.

As shown in FIG. 95B , the primary coil formation trench 11 A is formed with a first trench part 11 Aa that is formed in the insulating film 7 and a second trench part 11 Ab that is formed in the substrate main body 6 and that communicates with the first trench part 11 Aa. On the inner surface of the primary coil formation trench 11 A (the second trench part 11 Ab) in the substrate main body 6 , an insulating film 12 formed with an oxide film or the like is formed. In the preferred embodiment, the insulating film 12 is formed with a thermal oxide film (SiO 2 ), and when the thermal oxide film is formed on the inner surface of the primary coil formation trench 11 A, the surrounding wall (the side wall and the bottom wall) of the primary coil formation trench 11 A (the second trench part 11 Ab) in the substrate main body 6 is thermally oxidized into an insulator portion (thermal oxide film) 30 having insulation. In the preferred embodiment, an example is described where the entire wall sandwiched by the primary coil formation trench 11 A (the second trench part 11 Ab) in the shape of a spiral in the substrate main body 6 is a thermal oxide film.

On the surface of the insulating film 12 within the primary coil formation trench 11 A (the second trench part 11 Ab) and on the inner surface of the primary coil formation trench 11 A (the first trench part 11 Aa) in the insulating film 7 , a barrier metal film 13 is formed. The barrier metal film 13 is formed of, for example, TiN. The thickness of the barrier metal film 13 is about 400 to 500 angstroms. Within the primary coil formation trench 11 A, a conductive member 51 is embedded while being in contact with the barrier metal film 13 . In the preferred embodiment, the conductive member 51 is formed of tungsten (W). The primary coil 3 A is formed with the conductive member 51 embedded within the primary coil formation trench 11 A. Hence, the primary coil 3 A is formed, in plan view, in the shape of a spiral (in the shape of a quadrilateral spiral) of the same pattern as the primary coil formation trench 11 A. Specifically, the primary coil 3 A includes a plurality of plate-shaped parts parallel to the side surfaces 2 c of the substrate 2 .

With reference to FIGS. 94, 96A, 96B, 97 and 99 , in the substrate 2 , the secondary coil formation trench 11 B is formed by digging down, in the secondary coil formation region 46 C, to a predetermined depth from the element formation surface 2 a . The secondary coil formation trench 11 B is formed, in plan view, in the shape of a spiral. In the preferred embodiment, the secondary coil formation trench 11 B is formed, in plan view, in the shape of a quadrilateral spiral, and has a plurality of rectilinear portions parallel to the side surfaces 2 c of the substrate 2 . The number of windings of the secondary coil formation trench 11 B is less than the number of windings of the primary coil formation trench 11 A.

The cross section (cross section in a direction perpendicular to a direction in which the secondary coil formation trench 11 B is extended in the spiral direction) of the secondary coil formation trench 11 B is formed in the shape of a rectangle which is long in the direction of the thickness of the substrate 2 . For example, the width of the secondary coil formation trench 11 B may be 1 μm or more and 3 μm or less. For example, the depth of the secondary coil formation trench 11 B may be 10 μm or more and 82 μm or less. The depth of the secondary coil formation trench 11 B is preferably 10 μm or more so that the internal resistance of the secondary coil 3 B formed within the secondary coil formation trench 11 B is decreased.

As shown in FIG. 96B , the secondary coil formation trench 11 B is formed with a first trench part 11 Ba that is formed in the insulating film 7 and a second trench part 11 Bb that is formed in the substrate main body 6 and that communicates with the first trench part 11 Ba. On the inner surface of the secondary coil formation trench 11 B (the second trench part 11 Bb) in the substrate main body 6 , an insulating film 12 formed with an oxide film or the like is formed. In the preferred embodiment, the insulating film 12 is formed with a thermal oxide film (SiO 2 ), and when the thermal oxide film is formed on the inner surface of the secondary coil formation trench 11 B, the surrounding wall (the side wall and the bottom wall) of the secondary coil formation trench 11 B (the second trench part 11 Bb) in the substrate main body 6 is thermally oxidized into an insulator portion (thermal oxide film) 30 having insulation. In the preferred embodiment, an example is described where the entire wall sandwiched by the secondary coil formation trench 11 B (the second trench part 11 Bb) in the shape of a spiral in the substrate main body 6 is a thermal oxide film.

On the surface of the insulating film 12 within the secondary coil formation trench 11 B (the second trench part 11 Bb) and on the inner surface of the secondary coil formation trench 11 B (the first trench part 11 Ba) in the insulating film 7 , a barrier metal film 13 is formed. The barrier metal film 13 is formed of, for example, TiN. The thickness of the barrier metal film 13 is about 400 to 500 angstroms. Within the secondary coil formation trench 11 B, a conductive member 51 is embedded while being in contact with the barrier metal film 13 . In the preferred embodiment, the conductive member 51 is formed of tungsten (W). The secondary coil 3 B is formed with the conductive member 51 embedded within the secondary coil formation trench 11 B. Hence, the secondary coil 3 B is formed, in plan view, in the shape of a spiral (in the shape of a quadrilateral spiral) of the same pattern as the secondary coil formation trench 11 B. Specifically, the secondary coil 3 B includes a plurality of plate-shaped parts parallel to the side surfaces 2 c of the substrate 2 . Hence, the number of windings of the secondary coil 3 B is less than the number of windings of the primary coil 3 A.

On the element formation surface 2 a (the surface of the insulating film 7 ) of the substrate 2 , an insulating film 8 is formed so as to coat the element formation surface 2 a and the conductive member 51 (the coils 3 A and 3 B). The insulating film 8 is formed, in plan view, in the shape of a rectangle matching with the element formation surface 2 a . The insulating film 8 is formed with, for example, a USG (Undoped Silicate Glass) film. In the insulating film 8 , a first contact hole 14 A (see FIGS. 94 and 97 ) that exposes one end portion (outer peripheral side end portion) of the primary coil 3 A and a second contact hole 15 A (see FIGS. 94 and 95A ) that exposes the other end portion (inner peripheral side end portion) of the primary coil 3 A are formed. Furthermore, in the insulating film 8 , a third contact hole 14 B (see FIGS. 94 and 97 ) that exposes one end portion (outer peripheral side end portion) of the secondary coil 3 B and a fourth contact hole 15 B (see FIGS. 94 and 96 A) that exposes the other end portion (inner peripheral side end portion) of the secondary coil 3 B are formed. As described above, in the side surfaces 2 c of the substrate 2 and the outer peripheral surface of the insulating film 8 , the passivation film 9 formed with a nitride film or the like is formed.

On the surface of the insulating film 8 , the first electrode 41 , the second electrode 42 , the third electrode 43 , and the fourth electrode 44 are formed. With reference to FIGS. 94, 95A, and 97 , the first electrode 41 includes a first electrode film 41 A that is formed on the surface of the insulating film 8 and a first external connection electrode 41 B that is bonded to the first electrode film 41 A. As shown in FIG. 94 , the first electrode film 41 A includes a drawing electrode 41 Aa that is connected to one end portion of the primary coil 3 A and a first pad 41 Ab that is formed integrally with the drawing electrode 41 Aa. The first pad 41 Ab is formed to be rectangular at one end portion of the primary side formation region 45 of the element formation surface 2 a . The first external connection electrode 41 B is connected to the first pad 41 Ab. As shown in FIGS. 94 and 97 , the drawing electrode 41 Aa enters the first contact hole 14 A from the surface of the insulating film 8 , and is connected to one end portion of the primary coil 3 A within the first contact hole 14 A. The drawing electrode 41 Aa is formed straight along a straight line that passes above one end portion of the primary coil 3 A to reach the first pad 41 Ab.

By extending one end portion of the primary coil formation trench 11 A to a position below the first pad 41 Ab, one end portion of the primary coil 3 A may be disposed in a position below the first pad 41 Ab. In this way, since the first contact hole 14 A can be formed in a position below the first pad 41 Ab, one end portion of the primary coil 3 A can be connected to the first pad 41 Ab. In this case, since the first electrode film 41 A can be formed with only the first pad 41 Ab, the drawing electrode 41 Aa is not needed.

The second electrode 42 includes a second electrode film 42 A that is formed on the surface of the insulating film 8 and a second external connection electrode 42 B that is bonded to the second electrode film 42 A. As shown in FIG. 94 , the second electrode film 42 A includes a drawing electrode 42 Aa that is connected to the other end portion of the primary coil 3 A and a second pad 42 Ab that is formed integrally with the drawing electrode 42 Aa. The second pad 42 Ab is formed to be rectangular at the other end portion of the primary side formation region 45 of the element formation surface 2 a . The second external connection electrode 42 B is connected to the second pad 42 Ab. As shown in FIGS. 94 and 95A , the drawing electrode 42 Aa enters the second contact hole 15 A from the surface of the insulating film 8 , and is connected to the other end portion of the primary coil 3 A within the second contact hole 15 A. The drawing electrode 42 Aa is formed straight along a straight line that passes above the other end portion of the primary coil 3 A to reach the second pad 42 Ab.

With reference to FIGS. 94, 96A and 97 , the third electrode 43 includes a third electrode film 43 A that is formed on the surface of the insulating film 8 and a third external connection electrode 43 B that is bonded to the third electrode film 43 A. As shown in FIG. 94 , the third electrode film 43 A includes a drawing electrode 43 Aa that is connected to one end portion of the secondary coil 3 B and a third pad 43 Ab that is formed integrally with the drawing electrode 43 Aa. The third pad 43 Ab is formed to be rectangular at one end portion of the secondary side formation region 46 of the element formation surface 2 a . The third external connection electrode 43 B is connected to the third pad 43 Ab. As shown in FIGS. 94 and 97 , the drawing electrode 43 Aa enters the third contact hole 14 B from the surface of the insulating film 8 , and is connected to one end portion of the secondary coil 3 B within the third contact hole 14 B. The drawing electrode 43 Aa is formed straight along a straight line that passes above one end portion of the secondary coil 3 B to reach the third pad 43 Ab.

By extending one end portion of the secondary coil formation trench 11 B to a position below the third pad 43 Ab, one end portion of the secondary coil 3 B may be disposed in a position below the third pad 43 Ab. In this way, since the third contact hole 14 B can be formed in a position below the third pad 43 Ab, one end portion of the secondary coil 3 B can be connected to the third pad 43 Ab. In this case, since the third electrode film 43 A can be formed with only the third pad 43 Ab, the drawing electrode 43 Aa is not needed.

The fourth electrode 44 includes a fourth electrode film 44 A that is formed on the surface of the insulating film 8 and a fourth external connection electrode 44 B that is bonded to the fourth electrode film 44 A. As shown in FIG. 94 , the fourth electrode film 44 A includes a drawing electrode 44 Aa that is connected to the other end portion of the secondary coil 3 B and a fourth pad 44 Ab that is formed integrally with the drawing electrode 44 Aa. The fourth pad 44 Ab is formed to be rectangular at the other end portion of the secondary side formation region 46 of the element formation surface 2 a . The second external connection electrode 42 B is connected to the second pad 42 Ab. As shown in FIGS. 94 and 96A , the drawing electrode 44 Aa enters the fourth contact hole 15 B from the surface of the insulating film 8 , and is connected to the other end portion of the secondary coil 3 B within the fourth contact hole 15 B. The drawing electrode 44 Aa is formed straight along a straight line that passes above the other end portion of the secondary coil 3 B to reach the fourth pad 44 Ab. In the preferred embodiment, as the electrode films 41 A to 44 A, Al films are used.

The first to fourth electrode films 41 A to 44 A are covered by a passivation film 16 formed with, for example, a nitride film (SiN), and furthermore, on the passivation film 16 , a resin film 17 such as polyimide is formed. In the passivation film 16 and the resin film 17 , in plan view, in regions corresponding to the vicinity of the first pad 41 Ab, the vicinity of the second pad 42 Ab, the vicinity of the third pad 43 Ab, and the vicinity of the fourth pad 44 Ab, first, second, third, and fourth cutout portions 18 A, 19 A, 18 B, and 19 B (see FIGS. 94, 95A, 96A, and 98 ) are respectively formed.

A region of the surface of the first pad 41 Ab other than an edge portion on the side of the second pad 42 Ab is exposed by the first cutout portion 18 A. A region of the surface of the second pad 42 Ab other than an edge portion on the side of the first pad 41 Ab is exposed by the second cutout portion 19 A. A region of the surface of the third pad 43 Ab other than an edge portion on the side of the fourth pad 44 Ab is exposed by the third cutout portion 18 B. A region of the surface of the fourth pad 44 Ab other than an edge portion on the side of the third pad 43 Ab is exposed by the fourth cutout portion 19 B. In other words, the passivation film 16 and the resin film 17 are formed, in plan view, in the primary coil formation region 45 C and the secondary coil formation region 46 C, and further in the region between the first pad 41 Ab and the third pad 43 Ab and the region between the second pad 42 Ab and the fourth pad 44 Ab, each which is the boundary portion region between the primary side formation region 45 and the secondary side formation region 46 .

The first, second, third, and fourth external connection electrodes 41 B, 42 B, 43 B, and 44 B fill the first, second, third, and fourth cutout portions 18 A, 19 A, 18 B, and 19 B. The first external connection electrode 41 B and the second external connection electrode 42 B are formed so as to protrude from the resin film 17 , and include a drawing portion 20 that is drawn to the side of the other external connection electrode along the surface of the resin film 17 . Likewise, the third external connection electrode 43 B and the fourth external connection electrode 44 B are formed so as to protrude from the resin film 17 , and include the drawing portion 20 that is drawn to the side of the other external connection electrode along the surface of the resin film 17 .

In the preferred embodiment, the first external connection electrode 41 B is formed so as to cover not only the surface of the first electrode film 41 A (the pad 41 Ab) and the insulating film 8 exposed within the first cutout portion 18 A but also the upper end surface of the passivation film 9 on the side of one end portion of the primary side formation region 45 . The two side surfaces other than the two side surfaces on the inner side of the first external connection electrode 41 B are formed so as to be flush with the surface of the passivation film 9 covering the peripheral surface of the insulating film 8 on the side of one end portion of the primary side formation region 45 .

The second external connection electrode 42 B is formed so as to cover not only the surface of the second electrode film 42 A (the pad 42 Ab) and the insulating film 8 exposed within the second cutout portion 19 A but also the upper end surface of the passivation film 9 on the side of the other end portion of the primary side formation region 45 . The two side surfaces other than the two side surfaces on the inner side of the second external connection electrode 42 B are formed so as to be flush with the surface of the passivation film 9 covering the peripheral surface of the insulating film 8 on the side of the other end portion of the primary side formation region 45 .

The third external connection electrode 43 B is formed so as to cover not only the surface of the third electrode film 43 A (the pad 43 Ab) and the insulating film 8 exposed within the third cutout portion 18 B but also the upper end surface of the passivation film 9 on the side of the one end portion of the secondary side formation region 46 . The two side surfaces other than the two side surfaces on the inner side of the third external connection electrode 43 B are formed so as to be flush with the surface of the passivation film 9 covering the peripheral surface of the insulating film 8 on the side of the one end portion of the secondary side formation region 46 .

The fourth external connection electrode 44 B is formed so as to cover not only the surface of the fourth electrode film 44 A (the pad 44 Ab) and the insulating film 8 exposed within the fourth cutout portion 19 B but also the upper end surface of the passivation film 9 on the side of the other end portion of the secondary side formation region 46 . The two side surfaces other than the two side surfaces on the inner side of the fourth external connection electrode 44 B are formed so as to be flush with the surface of the passivation film 9 covering the peripheral surface of the insulating film 8 on the side of the other end portion of the secondary side formation region 46 . The external connection electrodes 41 B, 42 B, 43 B, and 44 B may be formed with a Ni/Pd/Au laminated film having a Ni film in contact with the electrode films 41 A, 42 A, 43 A, and 44 A, a Pd film formed thereon, and an Au film formed thereon. The laminated film described above can be formed by a plating method.

The passivation film 16 and the resin film 17 coat, from the surface, the coils 3 A and 3 B, the insulating film 8 , the electrode films 41 A to 44 A in the coil formation region 45 C and 46 C on the element formation surface 2 a , a region between the first external connection electrode 41 B and the third external connection electrode 43 B and a region between the second external connection electrode 42 B and the fourth external connection electrode 44 B, and function as a protective film to protect them. On the other hand, the passivation film 9 formed on the side surfaces 2 c of the substrate 2 and the outer peripheral surface of the insulating film 8 functions as a protective film to protect the side surfaces 2 c of the substrate 2 and the outer peripheral surface of the insulating film 8 .

FIG. 100 is an electrical circuit diagram showing an electrical structure within the chip transformer. One end of the primary coil 3 A (represented by a symbol L 1 in FIG. 100 ) is connected to the first electrode 41 , and the other end of the primary coil 3 A is connected to the second electrode 42 . One end of the secondary coil 3 B (represented by a symbol L 2 in FIG. 100 ) is connected to the third electrode 43 , and the other end of the secondary coil 3 B is connected to the fourth electrode 44 . In this way, it functions as a transformer.

As a parameter indicating the performance (quality) of the transformer, the Q (Quality Factor) value of the coil is present. As the Q value of the coil is increased, its loss is decreased, and the coil has an excellent characteristic as a high-frequency inductance.

The Q value of the coils 3 A and 3 B is represented by formula (7) below.

Q= 2π fL/R   (7)

In the formula (7) above, f represents the frequency of a current flowing through the coil, L represents the inductance of the coils 3 A and 3 B, and R represents the internal resistance of the coils 3 A and 3 B.

In the arrangement of the first preferred embodiment of the fourth invention, in the substrate 2 , the primary coil formation trench 11 A and the secondary coil formation trench 11 B obtained by digging down from the element formation surface 2 a are formed, in plan view, in the shape of a spiral. The conductive member 51 is embedded within the primary coil formation trench 11 A and thus the primary coil 3 A is formed, and the conductive member 51 is embedded within the secondary coil formation trench 11 B and thus the secondary coil 3 B is formed. Hence, it is possible to increase the cross-sectional area of the coils 3 A and 3 B (the cross-sectional area of the coils 3 A and 3 B perpendicular to the direction in which the coils 3 A and 3 B are extended in the spiral direction), and thus it is possible to decrease the internal resistance (R in the formula (7) above) of the coils 3 A and 3 B. In this way, since the Q value of the coils 3 A and 3 B can be increased, it is possible to provide a high performance chip transformer.

The coil formation trenches 11 A and 11 B are formed in the substrate 2 , the conductive member 51 is embedded within the coil formation trenches 11 A and 11 B and thus it is possible to form the coils 3 A and 3 B, with the result that the coils 3 A and 3 B are easily manufactured. In this way, it is possible to provide a chip transformer that is easily manufactured.

Furthermore, on the element formation surface 2 a , which is one surface of the substrate 2 , the external connection electrodes 41 B to 44 B of the first to fourth electrodes 41 to 44 are formed. Hence, as shown in FIG. 101 , the element formation surface 2 a is made to face a mounting substrate 91 , the external connection electrodes 41 B to 44 B are bonded on the mounting substrate 91 by a solder 92 and thus it is possible to form a circuit assembly in which the chip transformer 1 is surface-mounted on the mounting substrate 91 . In other words, it is possible to provide a flip-chip connection-type chip transformer 1 , and it is possible to connect the chip transformer 1 to the mounting substrate 91 by a face-down bonding in which the element formation surface 2 a is made to face the mounting substrate 91 and wireless bonding. In this way, it is possible to decrease the occupied space of the chip transformer 1 on the mounting substrate 91 . In particular, it is possible to realize a low profile chip transformer 1 on the mounting substrate 91 . In this way, it is possible to effectively utilize the space within the housing of a small-sized electronic device or the like and to contribute to high-density mounting and miniaturization.

FIGS. 102A to 102L are cross-sectional views for illustrating an example of the manufacturing step of the chip transformer, and show cut surfaces corresponding to FIG. 95A . FIGS. 103 A to 103 E are partially enlarged cross-sectional views showing the details of the manufacturing step of a coil, and show cut surfaces corresponding to FIG. 95B . FIGS. 104A to 104L are cross-sectional views for illustrating an example of the manufacturing step of the chip transformer, and show cut surfaces corresponding to FIG. 96A .

As shown in FIGS. 102A and 104A , an original substrate 50 that is an original of the substrate main body 6 is prepared. On the surface of the original substrate 50 , the insulating film 7 such as a thermal oxide film or a CVD oxide film is formed. In the preferred embodiment, the insulating film 7 is a thermal oxide film. The surface of the insulating film 7 corresponds to the element formation surface 2 a of the substrate 2 .

FIG. 105 is a schematic plan view of part of the original substrate 50 in which the insulating film 7 is formed on the surface. As shown in FIG. 105 , in the element formation surface 2 a , chip transformer regions X corresponding to a plurality of chip transformers 1 are disposed in a matrix. Between the chip transformer regions X adjacent to each other, a boundary region Y is provided. The boundary region Y is a region in the shape of a band having a substantially constant width, extends in two directions perpendicular to each other and is formed in a lattice shape. After necessary steps are performed on the original substrate 50 in which the insulating film 7 is formed on the surface, the original substrate 50 is separated along the boundary region Y, and thus it is possible to obtain a plurality of chip transformers 1 .

The steps performed on the original substrate 50 in which the insulating film 7 is formed on the surface are as follows. First, as shown in FIGS. 102A and 104A , by photolithography and etching, a part of the insulating film 7 that corresponds to a region in which the coil formation trench 11 A and the secondary coil formation trench 11 B need to be formed is removed. In this way, in the insulating film 7 , the first trench part 11 Aa of the primary coil formation trench 11 A and the first trench part 11 Ba of the secondary coil formation trench 11 B are formed. Then, a hard mask formed with the insulating film 7 is used, and thus the original substrate 50 is etched. In this way, as shown in FIGS. 102B, 103A, and 104B , the second trench part 11 Ab of the primary coil formation trench 11 A and the second trench part 11 Bb of the secondary coil formation trench 11 B are formed in the original substrate 50 . In this way, in the insulating film 7 and the original substrate 50 , the primary coil formation trench 11 A and the secondary coil trench 11 B are formed. The coil formation trenches 11 A and 11 B may be formed by, for example, a so-called BOSCH process. The BOSCH process is a process that is generally used to make a hollow part in a MEMS (Micro Electro Mechanical System).

Then, as shown in FIGS. 102B, 103B, and 104B , on the inner surface of the coil formation trenches 11 A and 11 B, the insulating film (thermal oxide film) 12 is formed by a thermal oxidization method. Here, the surrounding wall (the side wall and the bottom wall) of the primary coil formation trench 11 A (the second trench part 11 Ab) in the original substrate 50 is thermally oxidized into an insulator portion (thermal oxide film) 30 having insulation. Likewise, the surrounding wall (the side wall and the bottom wall) of the secondary coil formation trench 11 B (the second trench part 11 Bb) in the substrate main body 6 is thermally oxidized into an insulator portion (thermal oxide film) 30 having insulation. In FIGS. 102B and 104B , the insulating film 12 is omitted but the insulator portion 30 is shown. In the preferred embodiment, the entire wall sandwiched by the primary coil formation trenches 11 A (the second trench parts 11 Ab) in the shape of a spiral and the entire wall sandwiched by the secondary coil formation trenches 11 B (the second trench parts 11 Bb) in the shape of a spiral in the substrate main body 6 are formed into the thermal oxide film.

Then, for example, by a sputtering method, the barrier metal film 13 made of TiN is formed on the element formation surface 2 a including the interiors of the trenches 11 A and 11 B. In this way, as shown in FIG. 103C , the barrier metal film 13 made of TiN is formed on the surfaces of the insulating film 12 and the insulating film 7 within the primary coil formation trench 11 and the surface of the insulating film 7 outside the primary coil formation trench 11 A. Likewise, the barrier metal film made of TiN is formed on the surfaces of the insulating film 12 and the insulating film 7 within the secondary coil formation trench 11 B and the surface of the insulating film 7 outside the secondary coil formation trench 11 B. Thereafter, annealing processing is performed.

Thereafter, as shown in FIGS. 102C, 103D, and 104C , for example, by a CVD method, on the element formation surface 2 a including the interiors of the coil formation trenches 11 A and 11 B, the conductive member 51 formed of tungsten (W) is deposited.

Then, for example, by an etch back method, overall etching is performed on the conductive member 51 from its surface. The overall etching is continued until the surface of the conductive member 51 is flush with the surface of the insulating film 7 . In this way, as shown in FIGS. 102D, 103E, and 104D , the conductive member 51 is embedded within the coil formation trenches 11 A and 11 B while in contact with the barrier metal film 13 . By the conductive member 51 embedded within the primary coil formation trench 11 A, the primary coil 3 A in the shape of a spiral when seen in plan view is formed, and by the conductive member 51 embedded within the secondary coil formation trench 11 B, the secondary coil 3 B in the shape of a spiral when seen in plan view is formed.

Then, as shown in FIGS. 102E and 104E , on the insulating film 7 , the insulating film 8 formed with a USG (Undoped Silicate Glass) film or the like is formed so as to coat the insulating film 7 (the element formation surface 2 a ) and the coils 3 A and 3 B. The insulating film 8 is formed by, for example, a CVD method. Thereafter, by photolithography and etching, in regions of the insulating film 8 corresponding to one end portion and the other end portion of the primary coil 3 A, the first contact hole 14 A (see FIG. 97 ) and the second contact hole 15 A (see FIG. 102E ) penetrating the insulating film 8 are respectively formed. Likewise, in regions of the insulating film 8 corresponding to one end portion and the other end portion of the secondary coil 3 B, the third contact hole 14 B (see FIG. 97 ) and the fourth contact hole 15 B (see FIG. 104E ) penetrating the insulating film 8 are respectively formed.

Then, for example, by sputtering, on the insulating film 8 including the interiors of the contact holes 14 A, 15 A, 14 B, and 15 B, an electrode film forming the first to fourth electrodes 41 to 44 is formed. In the preferred embodiment, the electrode film made of Al is formed. Thereafter, by photolithography and etching, the electrode film is patterned, and thus as shown in FIGS. 102F and 104F , the electrode film is separated into the first electrode film 41 A, the second electrode film 42 A, the third electrode film 43 A, and the fourth electrode film 44 A.

Then, as shown in FIGS. 102G and 104G , for example, by a CVD method, the passivation film 16 such as a nitride film is formed, and furthermore, polyimide is applied to form the resin film 17 . For example, polyimide to which photosensitivity is added is applied, and the polyimide is developed after exposure with a pattern corresponding to the first to fourth cutout portions 18 A, 19 A, 18 B, and 19 B. In this way, the resin film 17 having a cutout portion corresponding to the first to fourth cutout portions 18 A, 19 A, 18 B, and 19 B is formed. Thereafter, as necessary, heat treatment for curing the resin film is performed. Then, by dry etching using the resin film 17 as a mask, the first to fourth cutout portions 18 A, 19 A, 18 B, and 19 B are formed in the passivation film 16 .

Then, as shown in FIGS. 102H and 104H , a resist mask 52 having an opening 52 a in a lattice shape matching with the boundary region Y (see FIG. 105 ) is formed. Plasma etching is performed via the resist mask 52 , and thus as shown in FIGS. 102H and 104H , the original substrate 50 , the insulating film 7 , and the insulating film 8 are etched from the surface of the insulating film 8 to a predetermined depth. In this way, along the boundary region Y, a groove (scribe groove) 53 for cutting is formed.

Then, the resist mask 52 is peeled off. Thereafter, as shown in FIGS. 102I and 104I , for example, by a CVD method, an insulating film 54 such as a nitride film serving as the material of the passivation film 9 is formed over the entire region of the surface of the original substrate 50 . Here, the insulating film 54 is also formed over the entire region of the inner surface (the side wall surface and the bottom wall surface) of the groove 53 .

Then, as shown in FIGS. 102J and 104J , the insulating film 54 is selectively etched. Specifically, a part of the insulating film 54 other than the insulating film 54 (the passivation film 9 ) on the side wall surface of the groove 53 is removed. In this way, a part of the electrode films 41 A to 44 A that is not covered by the passivation film 16 and the resin film 17 is exposed. The insulating film 54 on the bottom surface of the groove 53 is removed.

Then, as shown in FIGS. 102K and 104K , on the first to fourth electrode films 41 A to 44 A exposed from the first to fourth cutout portions 18 A, 19 A, 18 B, and 19 B, for example, by plating (preferably, electroless plating), plating growth is performed in the following order: for example, Ni, Pd, and Au. In this way, the first to fourth external connection electrodes 41 B to 44 B are formed.

Thereafter, by a DBG (Dicing Before Grinding) method, a plurality of chip transformer regions X are divided into pieces. Specifically, as shown in FIGS. 102L and 104L , first, on the side of the surface of the original substrate 50 (the side of the external connection electrode), a supporting tape 71 having an adhesive surface 72 is adhered. Then, the original substrate 50 is polished from the rear surface to the bottom surface of the groove 53 . In this way, the chip transformer regions X are separated into individual chip transformers 1 . Thereafter, on a plurality of chip transformers 1 , the recovery step shown in FIGS. 45A to 45D or the recovery step shown in FIGS. 46A to 46C described in the first preferred embodiment of the second invention may be performed.

FIG. 106A is a partially cut perspective view of a chip transformer according to a second preferred embodiment of the fourth invention, and FIG. 106B is a perspective view showing a primary coil and a secondary coil formed within the chip transformer.

The chip transformer 1 A is a minute chip part and is formed in the shape of a rectangular parallelepiped. The planar shape of the chip transformer 1 A may be rectangular, the length L of one of adjacent two sides may be about 0.4 mm, and the length W of the other side may be about 0.4 mm. The thickness T of the entire chip transformer 1 may be about 0.15 mm.

The chip transformer 1 A includes a substrate 2 , a primary coil 3 A and a secondary coil 3 B that are formed within the substrate 2 , a first electrode 41 that is connected to one end portion of the primary coil 3 A, a second electrode 42 that is connected to the other end portion of the primary coil 3 A, a third electrode 43 that is connected to one end portion of the secondary coil 3 B, and a fourth electrode 44 that is connected to the other end of the secondary coil 3 B. The number of windings of the primary coil 3 A differs from the number of windings of the secondary coil 3 B. Although in the preferred embodiment, an example where the number of windings of the primary coil 3 A is greater than the number of windings of the secondary coil 3 B is described, the number of windings of the secondary coil 3 B may be greater than the number of windings of the primary coil 3 A.

The chip transformer 1 A in the second preferred embodiment of the fourth invention differs from the chip transformer 1 in the first preferred embodiment of the fourth invention in that in the surface of an electrode pair (the first electrode 41 and the second electrode 42 ) on the primary side, a plurality of concave portions 84 A and 84 B are respectively formed. In the surface of an electrode pair (the third electrode 43 and the fourth electrode 44 ) on the secondary side, the concave portions 84 A and 84 B are not formed.

FIG. 107A is a plan view showing the appearance of the chip transformer when seen from the side of the electrode, and FIG. 107B is a plan view showing the internal structure of the chip transformer. FIG. 108A is a cross-sectional view taken along line CVIIIA-CVIIIA in FIG. 107B , and FIG. 108B is a partially enlarged cross-sectional view of FIG. 108A . FIG. 109A is a cross-sectional view taken along line CIXA-CIXA in FIG. 107B , and FIG. 109B is a partially enlarged cross-sectional view of FIG. 109A . FIG. 110 is a cross-sectional view taken along line CX-CX in FIG. 107B . FIG. 111 is a cross-sectional view taken along line CXI-CXI in FIG. 107B , and FIG. 112 is a partially enlarged cross-sectional view of FIG. 111 . FIG. 113 is a cross-sectional view taken along line CXIII-CXIII in FIG. 107B , and FIG. 114 is a plan view showing a structure of the surface of a substrate by removing an arrangement formed on the surface of the substrate.

In the following description, the “front” refers to the lower side of the plane of FIG. 107B , the “back” refers to the upper side of the plane of FIG. 107B , the “left” refers to the left side of the plane of FIG. 107B , and the “right” refers to the right side of the plane of FIG. 107B .

The substrate 2 is formed in the shape of a rectangular parallelepiped, and includes a pair of main surfaces 2 a and 2 b and four side surfaces 2 c . One (the main surface 2 a on the upper surface side in FIG. 106A ) of the pair of main surfaces 2 a and 2 b is an element formation surface. In the following description, the main surface 2 a is referred to as an “element formation surface 2 a ,” and the main surface 2 b on the side opposite to the element formation surface 2 a is referred to as a “rear surface 2 b .” In the preferred embodiment, the substrate 2 is formed with a substrate main body 6 and an insulating film 7 formed on the surface thereof, and the surface of the insulating film 7 on the side opposite to the side of the substrate main body 6 is the element formation surface 2 a . In the preferred embodiment, the substrate main body 6 is formed with a silicon substrate, and the insulating film 7 is formed with a thermal oxide film (SiO 2 ). The element formation surface 2 a is formed in the shape of a rectangle in plan view when seen in a normal direction perpendicular to the element formation surface 2 a . The surface (element formation surface 2 a ) of the substrate 2 is covered by an insulating film 8 . The four side surfaces 2 c of the substrate 2 and the outer peripheral surface of the insulating film 8 are covered by a passivation film 9 such as a nitride film.

With reference to FIGS. 107B and 114 , in the front half of the element formation surface 2 a , a primary side formation region 45 for the formation of the primary side circuit of the transformer is provided, and in the back half, a secondary side formation region 46 for the formation of the secondary side circuit of the transformer is provided. Each of the regions 45 and 46 is formed, in plan view, in the shape of a rectangle which is long in a left/right direction. In one end portion (left side end portion) of the primary side formation region 45 , a first electrode formation region 45 A is provided, and in the other end portion (right side end portion), a second electrode formation region 45 B is provided. In one end portion (left side end portion) of the secondary side formation region 46 , a third electrode formation region 46 A is provided, and in the other end portion (right side end portion), a fourth electrode formation region 46 B is provided.

In the first electrode formation region 45 A, the external connection electrode (first external connection electrode) 41 B of the first electrode 41 is disposed, and in the second electrode formation region 45 B, the external connection electrode (second external connection electrode) 42 B of the second electrode 42 is disposed. The first external connection electrode 41 B is rectangular in plan view, and covers the region of the first electrode formation region 45 A other than an edge portion on the side of the third electrode formation region 46 A. The second external connection electrode 42 B is rectangular in plan view, and covers the region of the second electrode formation region 45 B other than an edge portion on the side of the fourth electrode formation region 46 B. On the element formation surface 2 a between the external connection electrodes 41 B and 42 B, a primary coil formation region 45 C is provided. In the preferred embodiment, the primary coil formation region 45 C is formed in the shape of a rectangle.

In the third electrode formation region 46 A, the external connection electrode (third external connection electrode) 43 B of the third electrode 43 is disposed, and in the fourth electrode formation region 46 B, the external connection electrode (fourth external connection electrode) 44 B of the fourth electrode 44 is disposed. The third external connection electrode 43 B is rectangular in plan view, and covers the region of the third electrode formation region 46 A other than an edge portion on the side of the first electrode formation region 45 A. The fourth external connection electrode 44 B is rectangular in plan view, and covers the region of the fourth electrode formation region 46 B other than an edge portion on the side of the second electrode formation region 45 B. On the element formation surface 2 a between the external connection electrodes 43 B and 44 B, a secondary coil formation region 46 C is provided. In the preferred embodiment, the secondary coil formation region 46 C is formed in the shape of a rectangle.

In the surface of the first external connection electrode 41 B and the surface of the second external connection electrode 42 B, a plurality of first concave portions 84 A and a plurality of second concave portions 84 B are respectively formed. The plurality of first concave portions 84 A are formed, in plan view, in the shape of a straight line extending in the longitudinal direction of the primary side formation region 45 , and are formed at an interval in the lateral direction of the primary side formation region 45 . Likewise, the plurality of second concave portions 84 B are formed, in plan view, in the shape of a straight line extending in the longitudinal direction of the primary side formation region 45 , and are formed at an interval in the lateral direction of the primary side formation region 45 . The cross-sectional shape of the concave portions 84 A and 84 B is the shape of the letter V. In the surfaces of the third external connection electrode 43 B and the fourth external connection electrode 44 B, the concave portions 84 A and 84 B are not formed.

With reference to FIGS. 107B, 108A, 108B, and 110 to 114 , in the substrate 2 the primary coil formation trench 11 A is formed by digging down, in the primary coil formation region 45 C, to a predetermined depth from the element formation surface 2 a . The primary coil formation trench 11 A is formed, in plan view, in the shape of a spiral. In the preferred embodiment, the primary coil formation trench 11 A is formed, in plan view, in the shape of a quadrilateral spiral, and has a plurality of rectilinear portions parallel to the side surfaces 2 c of the substrate 2 .

The cross section (cross section in a direction perpendicular to a direction in which the primary coil formation trench 11 A is extended in the spiral direction) of the primary coil formation trench 11 A is formed in the shape of a rectangle which is long in the direction of the thickness of the substrate 2 . For example, the width of the primary coil formation trench 11 A may be 1 μm or more and 3 μm or less. For example, the depth of the primary coil formation trench 11 A may be 10 μm or more and 82 μm or less. The depth of the primary coil formation trench 11 A is preferably 10 μm or more so that the internal resistance of the primary coil 3 A formed within the primary coil formation trench 11 A is decreased.

Furthermore, in a region opposite the first external connection electrode 41 B within the first electrode formation region 45 A, in the substrate 2 , a plurality of first electrode-side trenches (concave portion formation trenches) 21 A are formed by digging down from the element formation surface 2 a to a predetermined depth. The plurality of first electrode-side trenches 21 A are formed in positions opposite the plurality of first concave portions 84 A. Hence, the plurality of first electrode-side trenches 21 A are formed, in plan view, in the shape of a straight line extending in the longitudinal direction of the primary side formation region 45 , and are formed at an interval in the lateral direction of the primary side formation region 45 .

Likewise, in a region opposite the second external connection electrode 42 B within the second electrode formation region 45 B, in the substrate 2 , a plurality of second electrode-side trenches (concave portion formation trenches) 21 B are formed by digging down from the element formation surface 2 a to a predetermined depth. The plurality of second electrode-side trenches 21 B are formed in positions opposite the plurality of second concave portions 84 B. Hence, the plurality of second electrode-side trenches 21 B are formed, in plan view, in the shape of a straight line extending in the longitudinal direction of the primary side formation region 45 , and are formed at an interval in the lateral direction of the primary side formation region 45 .

The cross sections of the electrode-side trenches 21 A and 21 B are the shape of a rectangle that is long in the direction of the thickness of the substrate 2 . In the preferred embodiment, the width of the electrode-side trenches 21 A and 21 B is narrower than that of the primary coil formation trench 11 A. The depth of the electrode-side trenches 21 A and 21 B may be the same as that of the primary coil formation trench 11 A or may be shallower than that of the primary coil formation trench 11 A. In the preferred embodiment, the depth of the electrode-side trenches 21 A and 21 B is the same as that of the primary coil formation trench 11 A.

As shown in FIG. 108B , the primary coil formation trench 11 A is formed with a first trench part 11 Aa that is formed in the insulating film 7 and a second trench part 11 Ab that is formed in the substrate main body 6 and that communicates with the first trench part 11 Aa. On the inner surface of the primary coil formation trench 11 A (the second trench part 11 Ab) in the substrate main body 6 , an insulating film 12 formed with an oxide film or the like is formed. On the surface of the insulating film 12 within the primary coil formation trench 11 A (the second trench part 11 Ab) and on the inner surface of the primary coil formation trench 11 A (the first trench part 11 Aa) in the insulating film 7 , a barrier metal film 13 is formed. The barrier metal film 13 is formed of, for example, TiN. The thickness of the barrier metal film 13 is about 400 to 500 angstroms.

Within the primary coil formation trench 11 A, a conductive member 51 is embedded while being in contact with the barrier metal film 13 . In the preferred embodiment, the conductive member 51 is formed of tungsten (W). The primary coil 3 A is formed with the conductive member 51 embedded within the primary coil formation trench 11 A. Hence, the primary coil 3 A is formed, in plan view, in the shape of a spiral (in the shape of a quadrilateral spiral) of the same pattern as the primary coil formation trench 11 A. Specifically, the primary coil 3 A includes a plurality of plate-shaped parts parallel to the side surfaces 2 c of the substrate 2 .

As shown in FIGS. 111, 112, and 113 , the electrode-side trenches 21 A and 21 B are formed with first trench parts 21 Aa and 21 Ba that are formed in the insulating film 7 and second trench parts 21 Ab and 21 Bb that are formed in the substrate main body 6 and that communicate with the first trench parts 21 Aa and 21 Ba. On the inner surface of the electrode-side trenches 21 A and 21 B (the second trench parts 21 Ab and 21 Bb) in the substrate main body 6 , an insulating film 12 formed with an oxide film or the like is formed. In the preferred embodiment, the insulating film 12 formed on the inner surface of the electrode-side trenches 21 A and 21 B (the second trench parts 21 Ab and 21 Bb) in the substrate main body 6 fills the second trench parts 21 Ab and 21 Bb.

On the inner surface of the first electrode-side trench 21 A (the first trench part 21 Aa) in the insulating film 7 , the barrier metal film 13 is formed. Within the first electrode-side trench 21 A (the first trench part 21 Aa) in the insulating film 7 , the conductive member 51 is embedded while being in contact with the barrier metal film 13 . In the surface of the conductive member 51 within the first electrode-side trench 21 A, first concave portions 81 A (first underlying concave portions) are formed. In other words, in a region of the element formation surface 2 a opposite the first external connection electrode 41 B, a plurality of first concave portions 81 A are formed. The plurality of first concave portions 81 A are formed in positions opposite the first concave portions 84 A of the first external connection electrode 41 B. Hence, the plurality of first concave portions 81 A are formed, in plan view, in the shape of a straight line extending in the longitudinal direction of the primary side formation region 45 , and are formed at an interval in the lateral direction of the primary side formation region 45 . The cross-sectional shape of the first concave portion 81 A is the shape of the letter V. The plurality of first concave portions 81 A are formed due to the first electrode-side trenches 21 A formed in the substrate 2 .

Likewise, on the inner surface of the second electrode-side trench 21 B (the first trench part 21 Ba) in the insulating film 7 , the barrier metal film (not shown) is formed. Within the second electrode-side trench 21 B (the first trench part 21 Ba) in the insulating film 7 , the conductive member (not shown) is embedded while being in contact with the barrier metal film. In the surface of the conductive member within the second electrode-side trench 21 B, second concave portions 81 B (first underlying concave portions) are formed. In other words, in a region of the element formation surface 2 a opposite the second external connection electrode 42 B, a plurality of second concave portions 81 B are formed. The plurality of second concave portions 81 B are formed in positions opposite the second concave portions 84 B of the second external connection electrode 42 B. Hence, the plurality of second concave portions 81 B are formed, in plan view, in the shape of a straight line extending in the longitudinal direction of the primary side formation region 45 , and are formed at an interval in the lateral direction of the primary side formation region 45 . The cross-sectional shape of the second concave portion 81 B is the shape of the letter V. The plurality of second concave portions 81 B are formed due to the plurality of second electrode-side trenches 21 B formed in the substrate 2 .

In the preferred embodiment, the insulating film 12 formed on the inner surfaces of the primary coil formation trench 11 A and the electrode-side trenches 21 A and 21 B is formed with a thermal oxide film (SiO 2 ). When the thermal oxide film is formed on the inner surface of the trenches 11 A, 21 A, and 21 B, the surrounding wall (the side wall and the bottom wall) of the trenches 11 A, 21 A, and 21 B in the substrate main body 6 is thermally oxidized into an insulator portion (thermal oxide film) 30 having insulation. In the preferred embodiment, an example is described where the entire wall sandwiched by the primary coil formation trenches 11 A (the second trench part 11 Ab) in the shape of a spiral in the substrate main body 6 , the entire wall between the adjacent two first electrode-side trenches 21 A (the second trench parts 21 Ab), and the entire wall between the adjacent two second electrode-side trenches 21 B (the second trench parts 21 Bb) are thermal oxide films.

With reference to FIGS. 107B, 109A, 109B, and 110 , in the substrate 2 , the secondary coil formation trench 11 B is formed by digging down, in the secondary coil formation region 46 C, to a predetermined depth from the element formation surface 2 a . The secondary coil formation trench 11 B is formed, in plan view, in the shape of a spiral. In the preferred embodiment, the secondary coil formation trench 11 B is formed, in plan view, in the shape of a quadrilateral spiral, and has a plurality of rectilinear portions parallel to the side surfaces 2 c of the substrate 2 . The number of windings of the secondary coil formation trench 11 B is less than the number of windings of the primary coil formation trench 11 A.

The cross section (cross section in a direction perpendicular to a direction in which the secondary coil formation trench 11 B is extended in the spiral direction) of the secondary coil formation trench 11 B is formed in the shape of a rectangle which is long in the direction of the thickness of the substrate 2 . For example, the width of the secondary coil formation trench 11 B may be 1 μm or more and 3 μm or less. For example, the depth of the secondary coil formation trench 11 B may be 10 μm or more and 82 μm or less. The depth of the secondary coil formation trench 11 B is preferably 10 μm or more so that the internal resistance of the secondary coil 3 B formed within the secondary coil formation trench 11 B is decreased.

As shown in FIG. 109B , the secondary coil formation trench 11 B is formed with a first trench part 11 Ba that is formed in the insulating film 7 and a second trench part 11 Bb that is formed in the substrate main body 6 and that communicates with the first trench part 11 Ba. On the inner surface of the secondary coil formation trench 11 B (the second trench part 11 Bb) in the substrate main body 6 , an insulating film 12 formed with an oxide film or the like is formed. In the preferred embodiment, the insulating film 12 is formed with a thermal oxide film (SiO 2 ), and when the thermal oxide film is formed on the inner surface of the secondary coil formation trench 11 B, the surrounding wall (the side wall and the bottom wall) of the secondary coil formation trench 11 B (the second trench part 11 Bb) in the substrate main body 6 is thermally oxidized into an insulator portion (thermal oxide film) 30 having insulation. In the preferred embodiment, an example is described where the entire wall sandwiched by the secondary coil formation trenches 11 B (the second trench parts 11 Bb) in the shape of a spiral in the substrate main body 6 is a thermal oxide film.

On the surface of the insulating film 12 within the secondary coil formation trench 11 B (the second trench part 11 Bb) and on the inner surface of the secondary coil formation trench 11 B (the first trench part 11 Ba) in the insulating film 7 , a barrier metal film 13 is formed. The barrier metal film 13 is formed of, for example, TiN. The thickness of the barrier metal film 13 is about 400 to 500 angstroms. Within the secondary coil formation trench 11 B, a conductive member 51 is embedded while being in contact with the barrier metal film 13 . In the preferred embodiment, the conductive member 51 is formed of tungsten (W). The secondary coil 3 B is formed with the conductive member 51 embedded within the secondary coil formation trench 11 B. Hence, the secondary coil 3 B is formed, in plan view, in the shape of a spiral (in the shape of a quadrilateral spiral) of the same pattern as the secondary coil formation trench 11 B. Specifically, the secondary coil 3 B includes a plurality of plate-shaped parts parallel to the side surfaces 2 c of the substrate 2 . Hence, the number of windings of the secondary coil 3 B is less than the number of windings of the primary coil 3 A.

On the element formation surface 2 a (the surface of the insulating film 7 ) of the substrate 2 , an insulating film 8 is formed so as to coat the element formation surface 2 a and the conductive member 51 . The insulating film 8 is formed, in plan view, in the shape of a rectangle matching with the element formation surface 2 a . The insulating film 8 is formed with, for example, a USG (Undoped Silicate Glass) film. In the insulating film 8 , a first contact hole 14 A (see FIGS. 107B and 110 ) that exposes one end portion (outer peripheral side end portion) of the primary coil 3 A and a second contact hole 15 A (see FIGS. 107B and 108A ) that exposes the other end portion (inner peripheral side end portion) of the primary coil 3 A are formed. Furthermore, in the insulating film 8 , a third contact hole 14 B (see FIGS. 107B and 110 ) that exposes one end portion (outer peripheral side end portion) of the secondary coil 3 B and a fourth contact hole 15 B (see FIGS. 107B and 109A ) that exposes the other end portion (inner peripheral side end portion) of the secondary coil 3 B are formed.

Furthermore, in the surface of the insulating film 8 , as shown in FIGS. 111 and 112 , in the first electrode formation region 45 A, a plurality of first concave portions 82 A (second underlying concave portions) are formed. The plurality of first concave portions 82 A are formed in positions opposite the first concave portions 84 A (the first concave portions 81 A) of the first external connection electrode 41 B. Hence, the plurality of first concave portions 82 A are formed, in plan view, in the shape of a straight line extending in the longitudinal direction of the primary side formation region 45 , and are formed at an interval in the lateral direction of the primary side formation region 45 . The cross-sectional shape of the first concave portion 82 A is the shape of the letter V. The first concave portions 82 A are formed due to the first concave portion 81 A in the surface (the element formation surface 2 a ) of the substrate 2 , which is its underlying layer.

Likewise, in the surface of the insulating film 8 , as shown in FIG. 113 , in the second electrode formation region 45 B, a plurality of second concave portions 82 B (second underlying concave portions) are formed. The second concave portions 82 B are formed in positions opposite the second concave portions 84 B (the second concave portions 81 B) of the second external connection electrode 42 B. Hence, the plurality of second concave portions 82 B are formed, in plan view, in the shape of a straight line extending in the longitudinal direction of the primary side formation region 45 , and are formed at an interval in the lateral direction of the primary side formation region 45 . The cross-sectional shape of the second concave portion 82 B is the shape of the letter V. The second concave portions 82 B are formed due to the second concave portion 81 B in the surface (the element formation surface 2 a ) of the substrate 2 , which is its underlying layer. As described previously, in the side surfaces 2 c of the substrate 2 and the outer peripheral surface of the insulating film 8 , the passivation film 9 formed with a nitride film or the like is formed.

On the surface of the insulating film 8 , the first electrode 41 , the second electrode 42 , the third electrode 43 , and the fourth electrode 44 are formed. With reference to FIGS. 107B, 108A, and 110 , the first electrode 41 includes a first electrode film 41 A that is formed on the surface of the insulating film 8 and a first external connection electrode 41 B that is bonded to the first electrode film 41 A. As shown in FIG. 107B , the first electrode film 41 A includes a drawing electrode 41 Aa that is connected to one end portion of the primary coil 3 A and a first pad 41 Ab that is formed integrally with the drawing electrode 41 Aa. The first pad 41 Ab is formed to be rectangular at one end portion of the primary side formation region 45 of the element formation surface 2 a . The first external connection electrode 41 B is connected to the first pad 41 Ab. As shown in FIGS. 107B and 110 , the drawing electrode 41 Aa enters the first contact hole 14 A from the surface of the insulating film 8 , and is connected to one end portion of the primary coil 3 A within the first contact hole 14 A. The drawing electrode 41 Aa is formed straight along a straight line that passes above one end portion of the primary coil 3 A to reach the first pad 41 Ab.

By extending one end portion of the primary coil formation trench 11 A to a position below the first pad 41 Ab, one end portion of the primary coil 3 A may be disposed in a position below the first pad 41 Ab. In this way, since the first contact hole 14 A can be formed in a position below the first pad 41 Ab, one end portion of the primary coil 3 A can be connected to the first pad 41 Ab. In this case, since the first electrode film 41 A can be formed with only the first pad 41 Ab, the drawing electrode 41 Aa is not needed.

The second electrode 42 includes a second electrode film 42 A that is formed on the surface of the insulating film 8 and a second external connection electrode 42 B that is bonded to the second electrode film 42 A. As shown in FIG. 107B , the second electrode film 42 A includes a drawing electrode 42 Aa that is connected to the other end portion of the primary coil 3 A and a second pad 42 Ab that is formed integrally with the drawing electrode 42 Aa. The second pad 42 Ab is formed to be rectangular at the other end portion of the primary side formation region 45 of the element formation surface 2 a . The second external connection electrode 42 B is connected to the second pad 42 Ab. As shown in FIGS. 107B and 108A , the drawing electrode 42 Aa enters the second contact hole 15 A from the surface of the insulating film 8 , and is connected to the other end portion of the primary coil 3 A within the second contact hole 15 A. The drawing electrode 42 Aa is formed straight along a straight line that passes above the other end portion of the primary coil 3 A to reach the second pad 42 Ab.

With reference to FIGS. 107B, 109A, and 110 , the third electrode 43 includes a third electrode film 43 A that is formed on the surface of the insulating film 8 and a third external connection electrode 43 B that is bonded to the third electrode film 43 A. As shown in FIG. 107B , the third electrode film 43 A includes a drawing electrode 43 Aa that is connected to one end portion of the secondary coil 3 B and a third pad 43 Ab that is formed integrally with the drawing electrode 43 Aa. The third pad 43 Ab is formed to be rectangular at one end portion of the secondary side formation region 46 of the element formation surface 2 a . The third external connection electrode 43 B is connected to the third pad 43 Ab. As shown in FIGS. 107B and 110 , the drawing electrode 43 Aa enters the third contact hole 14 B from the surface of the insulating film 8 , and is connected to one end portion of the secondary coil 3 B within the third contact hole 14 B. The drawing electrode 43 Aa is formed straight along a straight line that passes above one end portion of the secondary coil 3 B to reach the third pad 43 Ab.

By extending one end portion of the secondary coil formation trench 11 B to a position below the third pad 43 Ab, one end portion of the secondary coil 3 B may be disposed in a position below the third pad 43 Ab. In this way, since the third contact hole 14 B can be formed in a position below the third pad 43 Ab, one end portion of the secondary coil 3 B can be connected to the third pad 43 Ab. In this case, since the third electrode film 43 A can be formed with only the third pad 43 Ab, the drawing electrode 43 Aa is not needed.

The fourth electrode 44 includes a fourth electrode film 44 A that is formed on the surface of the insulating film 8 and a fourth external connection electrode 44 B that is bonded to the fourth electrode film 44 A. As shown in FIG. 107B , the fourth electrode film 44 A includes a drawing electrode 44 Aa that is connected to the other end portion of the secondary coil 3 B and a fourth pad 44 Ab that is formed integrally with the drawing electrode 44 Aa. The fourth pad 44 Ab is formed to be rectangular at the other end portion of the secondary side formation region 46 of the element formation surface 2 a . The second external connection electrode 42 B is connected to the second pad 42 Ab. As shown in FIGS. 107B and 109A , the drawing electrode 44 Aa enters the fourth contact hole 15 B from the surface of the insulating film 8 , and is connected to the other end portion of the secondary coil 3 B within the fourth contact hole 15 B. The drawing electrode 44 Aa is formed straight along a straight line that passes above the other end portion of the secondary coil 3 B to reach the fourth pad 44 Ab. In the preferred embodiment, as the electrode films 41 A to 44 A, Al films are used.

In the surface of the first pad 41 Ab of the first electrode film 41 A, as shown in FIGS. 111 and 112 , a plurality of first concave portions 83 A (third underlying concave portions) are formed. The plurality of first concave portions 83 A are formed in positions opposite the first concave portions 84 A (the first concave portions 82 A) of the first external connection electrode 41 B. Hence, the first concave portions 83 A are formed, in plan view, in the shape of a straight line extending in the longitudinal direction of the primary side formation region 45 , and are formed at an interval in the lateral direction of the primary side formation region 45 . The cross-sectional shape of the first concave portion 83 A is the shape of the letter V. The first concave portions 83 A are formed due to the first concave portion 82 A in the surface of the insulating film 8 , which is its underlying layer.

Likewise, in the surface of the second pad 42 Ab of the second electrode film 42 A, as shown in FIG. 113 , a plurality of second concave portions 83 B (third underlying concave portions) are formed. The plurality of second concave portions 83 B are formed in positions opposite the second concave portions 84 B (the second concave portions 82 B) of the second external connection electrode 42 B. Hence, the second concave portions 83 B are formed, in plan view, in the shape of a straight line extending in the longitudinal direction of the primary side formation region 45 , and are formed at an interval in the lateral direction of the primary side formation region 45 . The cross-sectional shape of the second concave portion 83 B is the shape of the letter V. The second concave portions 83 B are formed due to the second concave portion 82 B in the surface of the insulating film 8 , which is its underlying layer.

The first to fourth electrode films 41 A to 44 A are covered by a passivation film 16 formed with, for example, a nitride film (SiN), and furthermore, on the passivation film 16 , a resin film 17 such as polyimide is formed. In the passivation film 16 and the resin film 17 , in plan view, in regions corresponding to the vicinity of the first pad 41 Ab, the vicinity of the second pad 42 Ab, the vicinity of the third pad 43 Ab, and the vicinity of the fourth pad 44 Ab, first, second, third, and fourth cutout portions 18 A, 19 A, 18 B, and 19 B (see FIGS. 108A, 109A, 111, and 113 ) are respectively formed.

A region of the surface of the first pad 41 Ab other than an edge portion on the side of the second pad 42 Ab is exposed by the first cutout portion 18 A. A region of the surface of the second pad 42 Ab other than an edge portion on the side of the first pad 41 Ab is exposed by the second cutout portion 19 A. A region of the surface of the third pad 43 Ab other than an edge portion on the side of the fourth pad 44 Ab is exposed by the third cutout portion 18 B. A region of the surface of the fourth pad 44 Ab other than an edge portion on the side of the third pad 43 Ab is exposed by the fourth cutout portion 19 B. In other words, the passivation film 16 and the resin film 17 are formed, in plan view, in the primary coil formation region 45 C and the secondary coil formation region 46 C, and further in the region between the first pad 41 Ab and the third pad 43 Ab and the region between the second pad 42 Ab and the fourth pad 44 Ab, each which is the boundary portion region between the primary side formation region 45 and the secondary side formation region 46 .

The first, second, third, and fourth external connection electrodes 41 B, 42 B, 43 B, and 44 B fill the first, second, third, and fourth cutout portions 18 A, 19 A, 18 B, and 19 B. The first external connection electrode 41 B and the second external connection electrode 42 B are formed so as to protrude from the resin film 17 , and include a drawing portion 20 that is drawn to the side of the other external connection electrode along the surface of the resin film 17 . Likewise, the third external connection electrode 43 B and the fourth external connection electrode 44 B are formed so as to protrude from the resin film 17 , and include the drawing portion 20 that is drawn to the side of the other external connection electrode along the surface of the resin film 17 .

In the preferred embodiment, the first external connection electrode 41 B is formed so as to cover not only the surface of the first electrode film 41 A (the pad 41 Ab) and the insulating film 8 exposed within the first cutout portion 18 A but also the upper end surface of the passivation film 9 on the side of one end portion of the primary side formation region 45 . The two side surfaces other than the two side surfaces on the inner side of the first external connection electrode 41 B are formed so as to be flush with the surface of the passivation film 9 covering the peripheral surface of the insulating film 8 on the side of one end portion of the primary side formation region 45 .

The second external connection electrode 42 B is formed so as to cover not only the surface of the second electrode film 42 A (the pad 42 Ab) and the insulating film 8 exposed within the second cutout portion 19 A but also the upper end surface of the passivation film 9 on the side of the other end portion of the primary side formation region 45 . The two side surfaces other than the two side surfaces on the inner side of the second external connection electrode 42 B are formed so as to be flush with the surface of the passivation film 9 covering the peripheral surface of the insulating film 8 on the side of the other end portion of the primary side formation region 45 .

The third external connection electrode 43 B is formed so as to cover not only the surface of the third electrode film 43 A (the pad 43 Ab) and the insulating film 8 exposed within the third cutout portion 18 B but also the upper end surface of the passivation film 9 on the side of the one end portion of the secondary side formation region 46 . The two side surfaces other than the two side surfaces on the inner side of the third external connection electrode 43 B are formed so as to be flush with the surface of the passivation film 9 covering the peripheral surface of the insulating film 8 on the side of the one end portion of the secondary side formation region 46 .

The fourth external connection electrode 44 B is formed so as to cover not only the surface of the fourth electrode film 44 A (the pad 44 Ab) and the insulating film 8 exposed within the fourth cutout portion 19 B but also the upper end surface of the passivation film 9 on the side of the other end portion of the secondary side formation region 46 . The two side surfaces other than the two side surfaces on the inner side of the fourth external connection electrode 44 B are formed so as to be flush with the surface of the passivation film 9 covering the peripheral surface of the insulating film 8 on the side of the other end portion of the secondary side formation region 46 . The external connection electrodes 41 B, 42 B, 43 B, and 44 B may be formed with, for example, a Ni/Pd/Au laminated film having a Ni film in contact with the electrode films 41 A, 42 A, 43 A, and 44 A, a Pd film formed thereon, and an Au film formed thereon. The laminated film described above can be formed by a plating method.

As described previously, in the surface of the first external connection electrode 41 B, a plurality of first concave portions 84 A are formed, and in the surface of the second external connection electrode 42 B, a plurality of second concave portions 84 B are formed. The first concave portions 84 A are formed due to the first concave portions 83 A in the surface of the first pad 41 Ab, which is its underlying layer. Since the first concave portions 83 A are formed due to the first concave portions 82 A, which is its underlying layer, and the first concave portions 82 A are formed due to the first concave portions 81 A, which is its underlying layer, the first concave portions 84 A are formed due to the first concave portions 81 A. As described later, the first concave portions 81 A are formed due to the first electrode-side trenches 21 A. Hence, the first concave portions 84 A in the first external connection electrode 41 B are formed due to the first electrode-side trenches 21 A.

The second concave portions 84 B are formed due to the second concave portions 83 B in the surface of the second pad 42 Ab, which is its underlying layer. Since the second concave portions 83 B are formed due to the second concave portions 82 B, and the second concave portions 82 B are formed due to the second concave portions 81 B, the second concave portions 84 B are formed due to the second concave portions 81 B. As the first concave portions 81 A are formed due to the first electrode-side trenches 21 A, the second concave portions 81 B are formed due to the second electrode-side trenches 21 B. Hence, the second concave portions 84 B in the second external connection electrode 42 B are formed due to the second electrode-side trenches 21 B.

The passivation film 16 and the resin film 17 coat, from the surface, the coils 3 A and 3 B, the insulating film 8 , the electrode films 41 A to 44 A in the coil formation regions 45 C and 46 C of the element formation surface 2 a , in a region between the first external connection electrode 41 B and the third external connection electrode 43 B, and a region between the second external connection electrode 42 B and the fourth external connection electrode 44 B, and function as a protective film to protect them. On the other hand, the passivation film 9 formed on the side surfaces 2 c of the substrate 2 and the outer peripheral surface of the insulating film 8 function as a protective film to protect the side surfaces 2 c of the substrate 2 and the outer peripheral surface of the insulating film 8 .

FIG. 115 is an electrical circuit diagram showing an electrical structure within the chip transformer. One end of the primary coil 3 A (represented by a symbol L 1 in FIG. 115 ) is connected to the first electrode 41 , and the other end of the primary coil 3 A is connected to the second electrode 42 . One end of the secondary coil 3 B (represented by a symbol L 2 in FIG. 115 ) is connected to the third electrode 43 , and the other end of the secondary coil 3 B is connected to the fourth electrode 44 . In this way, it functions as a transformer.

As a parameter indicating the performance (quality) of the transformer, the Q (Quality Factor) value of the coil is present. As the Q value of the coil is increased, its loss is decreased, and the coil has an excellent characteristic as a high-frequency inductance.

The Q value of the coils 3 A and 3 B is represented by formula (8) below.

Q= 2π fL/R   (8)

In the formula (8) above, f represents the frequency of a current flowing through the coil, L represents the inductance of the coils 3 A and 3 B and R represents the internal resistance of the coils 3 A and 3 B.

In the arrangement of the second preferred embodiment of the fourth invention, in the substrate 2 , the primary coil formation trench 11 A and the secondary coil formation trench 11 B obtained by digging down from the element formation surface 2 a are formed, in plan view, in the shape of a spiral. The conductive member 51 is embedded within the primary coil formation trench 11 A and thus the primary coil 3 A is formed, and the conductive member 51 is embedded within the secondary coil formation trench 11 B and thus the secondary coil 3 B is formed. Hence, it is possible to increase the cross-sectional area of the coils 3 A and 3 B (the cross-sectional area of the coils 3 A and 3 B perpendicular to the direction in which the coils 3 A and 3 B are extended in the spiral direction), and thus it is possible to decrease the internal resistance (R in the formula (8) above) of the coils 3 A and 3 B. In this way, since the Q value of the coils 3 A and 3 B can be increased, it is possible to provide a high performance chip transformer.

The coil formation trenches 11 A and 11 B are formed in the substrate 2 , the conductive member 51 is embedded within the coil formation trenches 11 A and 11 B and thus it is possible to form the coils 3 A and 3 B, with the result that the coils 3 A and 3 B are easily manufactured. In this way, it is possible to provide a chip transformer that is easily manufactured.

When image inspection is performed on the chip transformer 1 A, light from a light source is applied to the surfaces of the electrodes 41 to 44 , and images of the surfaces are imaged with a camera. In the second preferred embodiment of the fourth invention, in the surfaces of the first external connection electrode 41 B and the second external connection electrode 42 B on the primary side, a plurality of concave portions 84 A and 84 B are formed but in the surfaces of the third external connection electrode 43 B and the fourth external connection electrode 44 B on the secondary side, a plurality of concave portions 84 A and 84 B are not formed. Since in the surfaces of the external connection electrodes 41 B and 42 B on the primary side, the concave portions 84 A and 84 B are formed, the light incident on the surfaces of the external connection electrodes 41 B and 42 B is diffusely reflected off the concave portions 84 A and 84 B. By contrast, since the concave portions are not formed in the surfaces of the external connection electrodes 43 B and 44 B on the secondary side, the light incident on the surface of the external connection electrodes 43 B and 44 B is unlikely to be diffusely reflected off.

Hence, a large difference is produced between image information (for example, brightness information) on the external connection electrodes 41 B and 42 B on the primary side and image information on the external connection electrodes 43 B and 44 B on the secondary side obtained with the camera. In this way, based on the image information obtained with the camera, it is possible to clearly identify the primary side electrode pairs 41 and 42 and the secondary side electrode pairs 43 and 44 . In other words, in the second preferred embodiment of the fourth invention, at the time of the image inspection, it is possible to easily determine the primary side electrode pairs 41 and 42 and the secondary side electrode pairs 43 and 44 .

Furthermore, on the element formation surface 2 a , which is one surface of the substrate 2 , the external connection electrodes 41 B to 44 B of the first to fourth electrodes 41 to 44 are formed. Hence, as shown in FIG. 116 , the element formation surface 2 a is made to face a mounting substrate 91 , the external connection electrodes 41 B to 44 B are bonded on the mounting substrate 91 by a solder 92 and thus it is possible to form a circuit assembly in which the chip transformer 1 A is surface-mounted on the mounting substrate 91 . In other words, it is possible to provide a flip-chip connection-type chip transformer 1 A, and it is possible to connect the chip transformer 1 A to the mounting substrate 91 by a face-down bonding in which the element formation surface 2 a is made to face the mounting substrate 91 and wireless bonding. In this way, it is possible to decrease the occupied space of the chip transformer 1 A on the mounting substrate 91 . In particular, it is possible to realize a low profile chip transformer 1 A on the mounting substrate 91 . In this way, it is possible to effectively utilize the space within the housing of a small-sized electronic device or the like and to contribute to high-density mounting and miniaturization.

With reference to FIGS. 102A to 102L, 103A to 103E, 104A to 104L, and 117A to 117F , a method of manufacturing the chip transformer 1 A will be described. Here, FIGS. 102A to 102L used in the first preferred embodiment of the fourth invention are used as process charts corresponding to the cut surface of FIG. 108A , FIGS. 103A to 103E used in the first preferred embodiment of the fourth invention are used as process charts corresponding to the cut surface of FIG. 108B and FIGS. 104A to 104L used in the first preferred embodiment of the fourth invention are used as process charts corresponding to the cut surface of FIG. 109A . However, although FIGS. 102B to 102L do not show the insulator portions 30 formed on the surrounding wall of the electrode-side trenches 21 A and 21 B, in the second preferred embodiment of the fourth invention, the insulator portions 30 are represented by a symbol 30 in FIG. 108A . FIGS. 117A to 117F are enlarged cross-sectional views showing the details of the manufacturing step of the first concave portion, and show cut surfaces corresponding to FIG. 112 .

As shown in FIGS. 102A and 104A , an original substrate 50 that is an original of the substrate main body 6 is prepared. On the surface of the original substrate 50 , the insulating film 7 such as a thermal oxide film or a CVD oxide film is formed. In the preferred embodiment, the insulating film 7 is a thermal oxide film. The surface of the insulating film 7 corresponds to the element formation surface 2 a of the substrate 2 .

FIG. 105 is a schematic plan view of part of the original substrate 50 in which the insulating film 7 is formed on the surface. As shown in FIG. 105 , in the element formation surface 2 a , chip transformer regions X corresponding to a plurality of chip transformers 1 A are disposed in a matrix. Between the chip transformer regions X adjacent to each other, a boundary region Y is provided. The boundary region Y is a region in the shape of a band having a substantially constant width, extends in two directions perpendicular to each other and is formed in a lattice shape. After necessary steps are performed on the original substrate 50 in which the insulating film 7 is formed on the surface, the original substrate 50 is separated along the boundary region Y, and thus it is possible to obtain a plurality of chip transformers 1 A.

The steps performed on the original substrate 50 in which the insulating film 7 is formed on the surface are as follows. First, as shown in FIGS. 102A, 104A, and 117A , by photolithography and etching, a part of the insulating film 7 that corresponds to a region in which the coil formation trench 11 A and the secondary coil formation trench 11 B, the primary electrode-side trench 21 A, and the secondary electrode-side trench 21 B need to be formed is removed. In this way, in the insulating film 7 , the first trench part 11 Aa of the primary coil formation trench 11 A, the first trench part 11 Ba of the secondary coil formation trench 11 B, the first trench part 21 Aa of the first electrode-side trench 21 A and the first trench part 21 Ba (not shown) of the second electrode-side trench 21 B (not shown) are formed.

Then, a hard mask formed with the insulating film 7 is used, and thus the original substrate 50 is etched. In this way, as shown in FIGS. 102B, 103A, 104B, and 117A , the second trench part 11 Ab of the primary coil formation trench 11 A, the second trench part 11 Bb of the secondary coil formation trench 11 B, the second trench part 21 Ab of the first electrode-side trench 21 A, and the second trench part 21 Bb (not shown) of the second electrode-side trench 21 B (not shown) are formed in the original substrate 50 . In this way, in the insulating film 7 and the original substrate 50 , the primary coil formation trench 11 A, the secondary coil formation trench 11 B, the first electrode-side trench 21 A, and the second electrode-side trench 21 B are formed. The coil formation trenches 11 A and 11 B and electrode-side trenches 21 A and 21 B may be formed with, for example, a so-called BOSCH process. The BOSCH process is a process that is generally used to make a hollow part in a MEMS (Micro Electro Mechanical System).

Then, as shown in FIGS. 102B, 103B, 104B and 117B , on the inner surface of the coil formation trenches 11 A and 11 B and the electrode-side trenches 21 A and 21 B, the insulating film (thermal oxide film) 12 is formed by a thermal oxidization method. Here, the surrounding wall (the side wall and the bottom wall) of the trenches 11 A, 11 B, 21 A, and 21 B (the second trench parts 11 Ab, 11 Bb, 21 Ab, and 21 Bb) in the original substrate 50 is thermally oxidized into an insulator portion (thermal oxide film) 30 having insulation. In the preferred embodiment, the entire wall sandwiched by the primary coil formation trench 11 A (the second trench part 11 Ab) in the shape of a spiral and the entire wall sandwiched by the secondary coil formation trench 11 B (the second trench part 11 Bb) in the shape of a spiral in the substrate main body 6 are formed into the thermal oxide film. In the preferred embodiment, the entire wall between the adjacent two first electrode-side trenches 21 A (the second trench parts 21 Ab) and the entire wall between the adjacent two second electrode-side trenches 21 B (the second trench parts 21 Bb) are formed into the thermal oxide films. The insulating film 12 formed on the inner surface of the electrode-side trenches 21 A and 21 B (the second trench parts 21 Ab and 21 Bb) fills the electrode-side trenches 21 A and 21 B.

Then, for example, by a sputtering method, the barrier metal film 13 made of TiN is formed on the element formation surface 2 a including the interiors of the trenches 11 A, 11 B, 21 A, and 21 B. In this way, as shown in FIG. 103C , the barrier metal film 13 made of TiN is formed on the surfaces of the insulating film 12 and the insulating film 7 within the primary coil formation trench 11 A and the surface of the insulating film 7 outside the primary coil formation trench 11 A. Likewise, the barrier metal film 13 made of TiN is formed on the surfaces of the insulating film 12 and the insulating film 7 within the secondary coil formation trench 11 B and the surface of the insulating film 7 outside the secondary coil formation trench 11 B. Moreover, as shown in FIG. 117C , the barrier metal film 13 is formed on the surfaces of the insulating film 12 and the insulating film 7 within the first electrode-side trench 21 A and the surface of the insulating film 7 outside the first electrode-side trench 21 A. Likewise, the barrier metal film 13 is formed on the surfaces of the insulating film 12 and the insulating film 7 within the second electrode-side trench 21 B and the surface of the insulating film 7 outside the second electrode-side trench 21 B. Thereafter, annealing processing is performed.

Thereafter, as shown in FIGS. 102C, 103D, 104C, and 117D , for example, by a CVD method, on the element formation surface 2 a including the interiors of the trenches 11 A, 11 B, 21 A, and 21 B, the conductive member 51 formed of tungsten (W) is deposited. Since on the entire surface of the element formation surface 2 a including the interiors of the trenches 11 A, 11 B, 21 A, and 21 B, the conductive member 51 is deposited at the same rate, in the surface of the conductive member 51 , concave portions 80 (see FIG. 117D ) are formed in positions opposite the trenches 11 A, 11 B, 21 A, and 21 B.

Then, for example, by an etch back method, overall etching is performed on the conductive member 51 from its surface. The overall etching is continued until the surface of the conductive member 51 is flush with the surface of the insulating film 7 . In this way, as shown in FIGS. 102D, 103E, 104D, and 117E , the conductive member 51 is embedded within the trenches 11 A, 11 B, 21 A, and 21 B while in contact with the barrier metal film 13 . By the conductive member 51 embedded within the primary coil formation trench 11 A, the primary coil 3 A in the shape of a spiral when seen in plan view is formed, and by the conductive member 51 embedded within the secondary coil formation trench 11 B, the secondary coil 3 B in the shape of a spiral when seen in plan view is formed.

Since the conductive member 51 is etched from the entire surface thereof at the same rate, on the surface of the conductive member 51 after the etching, the concave portions 81 are formed in positions opposite the concave portions 80 before the etching. However, although for ease of description, the concave portions 81 are shown in FIG. 117E , the concave portions are omitted in FIG. 103E . In the following description, the concave portion 81 formed in the conductive member 51 within the first electrode-side trench 21 A is referred to as a “first concave portion 81 A,” and the concave portion 81 formed in the conductive member 51 within the second electrode-side trench 21 B is referred to as a “second concave portion 81 B.”

Then, as shown in FIGS. 102E, 104E, and 117F , on the insulating film 7 , the insulating film 8 formed with a USG (Undoped Silicate Glass) film or the like is formed so as to coat the insulating film 7 (the element formation surface 2 a ) and the conductive member 51 . The insulating film 8 is formed by, for example, a CVD method. In the surface of the insulating film 8 formed as described above, as shown in FIG. 117F , in positions opposite the first concave portions 81 A, the first concave portions 82 A are formed. Although not shown in FIG. 117F , in positions opposite the second concave portions 81 B, the second concave portions 82 B are formed. Thereafter, by photolithography and etching, in regions of the insulating film 8 corresponding to one end portion and the other end portion of the primary coil 3 A, the first contact hole 14 A (see FIG. 110 ) and the second contact hole 15 A (see FIG. 102E ) penetrating the insulating film 8 are respectively formed. Likewise, in regions of the insulating film 8 corresponding to one end portion and the other end portion of the secondary coil 3 B, the third contact hole 14 B (see FIG. 110 ) and the fourth contact hole 15 B (see FIG. 104E ) penetrating the insulating film 8 are respectively formed.

Then, for example, by sputtering, on the insulating film 8 including the interiors of the contact holes 14 A, 15 A, 14 B, and 15 B, an electrode film forming the first to fourth electrodes 41 to 44 is formed. In the preferred embodiment, the electrode film made of Al is formed. Thereafter, by photolithography and etching, the electrode film is patterned, and thus as shown in FIGS. 102F, 104F, and 117F , the electrode film is separated into the first electrode film 41 A, the second electrode film 42 A, the third electrode film 43 A, and the fourth electrode film 44 A. In the surface of the first electrode film 41 A formed as described above, as shown in FIG. 117F , the first concave portions 83 A are formed in positions opposite the first concave portions 82 A. Although not shown in FIG. 117F , the second concave portions 83 B are formed in positions opposite the second concave portions 82 B.

Then, as shown in FIGS. 102G and 104G , for example, by a CVD method, the passivation film 16 such as a nitride film is formed, and furthermore, polyimide is applied to form the resin film 17 . For example, polyimide to which photosensitivity is added is applied, and the polyimide is developed after exposure with a pattern corresponding to the first to fourth cutout portions 18 A, 19 A, 18 B, and 19 B. In this way, the resin film 17 having a cutout portion corresponding to the first to fourth cutout portions 18 A, 19 A, 18 B, and 19 B is formed. Thereafter, as necessary, heat treatment for curing the resin film is performed. Then, by dry etching using the resin film 17 as a mask, the first to fourth cutout portions 18 A, 19 A, 18 B, and 19 B are formed in the passivation film 16 .

Then, as shown in FIGS. 102H and 104H , a resist mask 52 having an opening 52 a in a lattice shape matching with the boundary region Y (see FIG. 105 ) is formed. Plasma etching is performed via the resist mask 52 , and thus as shown in FIGS. 102H and 104H , the original substrate 50 , the insulating film 7 , and the insulating film 8 are etched from the surface of the insulating film 8 to a predetermined depth. In this way, along the boundary region Y, a groove (scribe groove) 53 for cutting is formed.

Then, the resist mask 52 is peeled off. Thereafter, as shown in FIGS. 102I and 104I , for example, by a CVD method, an insulating film 54 such as a nitride film serving as the material of the passivation film 9 is formed over the entire region of the surface of the original substrate 50 . Here, the insulating film 54 is also formed over the entire region of the inner surface (the side wall surface and the bottom wall surface) of the groove 53 .

Then, as shown in FIGS. 102J and 104J , the insulating film 54 is selectively etched. Specifically, a part of the insulating film 54 other than the insulating film 54 on the side wall surface of the groove 53 (the passivation film 9 ) is removed. In this way, a part of the electrode films 41 A to 44 A that is not covered by the passivation film 16 and the resin film 17 is exposed. The insulating film 54 on the bottom surface of the groove 53 is removed.

Then, as shown in FIGS. 102K, 104K, and 117F , on the first to fourth electrode films 41 A to 44 A exposed from the first to fourth cutout portions 18 A, 19 A, 18 B, and 19 B, for example, by plating (preferably, electroless plating), plating growth is performed in the following order: for example, Ni, Pd, and Au. In this way, the first to fourth external connection electrodes 41 B to 44 B are formed. In the surface of the first external connection electrode 41 B formed as described above, as shown in FIG. 117F , the first concave portions 84 A are formed in positions opposite the first concave portions 83 A. Although not shown in FIG. 117F , in the surface of the second external connection electrode 42 B, the second concave portions 84 B are formed in positions opposite the second concave portions 83 B.

Thereafter, by a DBG (Dicing Before Grinding) method, a plurality of chip transformer regions X are divided into pieces. Specifically, as shown in FIGS. 102L and 104L , first, on the side of the surface of the original substrate 50 (the side of the external connection electrode), a supporting tape 71 having an adhesive surface 72 is adhered. Then, the original substrate 50 is polished from the rear surface to the bottom surface of the groove 53 . In this way, the plurality of chip transformer regions X are separated into individual chip transformers 1 . Thereafter, on a plurality of chip transformers 1 A, the recovery step shown in FIGS. 45A to 45D or the recovery step shown in FIGS. 46A to 46C described in the first preferred embodiment of the second invention may be performed.

FIG. 118 is a partially cut perspective view of a chip transformer according to a third preferred embodiment of the fourth invention, and FIG. 119 is a plan view of a chip transformer. FIG. 120 is a cross-sectional view taken along line CXX-CXX in FIG. 119 , and FIG. 121 is a partially enlarged cross-sectional view of FIG. 120 . FIG. 122 is a cross-sectional view taken along line CXXII-CXXII in FIG. 119 , FIG. 123 is a cross-sectional view taken along line CXXIII-CXXIII in FIG. 119 , FIG. 124 is a cross-sectional view taken along line CXXIV-CXXIV in FIG. 119 , FIG. 125 is a cross-sectional view taken along line CXXV-CXXV in FIG. 119 and FIG. 126 is a plan view showing a structure of the surface of a substrate by removing an arrangement formed on the surface of the substrate.

The chip transformer 1 B is a minute chip part and is formed in the shape of a rectangular parallelepiped. The planar shape of the chip transformer 1 B may be rectangular, the length L in the longitudinal direction may be about 0.4 mm and the length W in the lateral direction may be about 0.2 mm. The thickness T of the entire chip transformer 1 may be about 0.15 mm.

The chip transformer 1 B includes a substrate 2 , a primary coil 3 A and a secondary coil 3 B that are formed within the substrate 2 , a first electrode 41 that is connected to one end portion of the primary coil 3 A, a second electrode 42 that is connected to the other end portion of the primary coil 3 A, a third electrode 43 that is connected to one end portion of the secondary coil 3 B, and a fourth electrode 44 that is connected to the other end of the secondary coil 3 B. The number of windings of the primary coil 3 A differs from the number of windings of the secondary coil 3 B. Although in the preferred embodiment, an example where the number of windings of the secondary coil 3 B is greater than the number of windings of the primary coil 3 A is described, the number of windings of the primary coil 3 A may be greater than the number of windings of the secondary coil 3 B.

In the following description, the “front” refers to the lower side of the plane of FIG. 119 , the “back” refers to the upper side of the plane of FIG. 119 , the “left” refers to the left side of the plane of FIG. 119 , and the “right” refers to the right side of the plane of FIG. 119 .

The substrate 2 is formed in the shape of a rectangular parallelepiped, and includes a pair of main surfaces 2 a and 2 b and four side surfaces 2 c . One (the main surface 2 a on the upper surface side in FIG. 118 ) of the pair of main surfaces 2 a and 2 b is an element formation surface. In the following description, the main surface 2 a is referred to as an “element formation surface 2 a ,” and the main surface 2 b on the side opposite to the element formation surface 2 a is referred to as a “rear surface 2 b .” In the preferred embodiment, the substrate 2 is formed with a substrate main body 6 and an insulating film 7 formed on the surface thereof, and the surface of the insulating film 7 on the side opposite to the side of the substrate main body 6 is the element formation surface 2 a . In the preferred embodiment, the substrate main body 6 is formed with a silicon substrate, and the insulating film 7 is formed with a thermal oxide film (SiO 2 ). The element formation surface 2 a is formed in the shape of a rectangle in plan view when seen in a normal direction perpendicular to the element formation surface 2 a . The surface (element formation surface 2 a ) of the substrate 2 is covered by an insulating film 8 . The four side surfaces 2 c of the substrate 2 and the outer peripheral surface of the insulating film 8 are covered by a passivation film 9 such as a nitride film.

With reference to FIGS. 119 and 126 , in the element formation surface 2 a , in the left side portion thereof, a primary side electrode pair formation region 47 for the formation of primary side electrode pairs 41 and 42 is provided, and in the right side portion thereof, a secondary side electrode pair formation region 48 for the formation of secondary side electrode pairs 43 and 44 is provided. These regions 47 and 48 are formed, in plan view, in the shape of a rectangle which is long in a front/back direction. On the element formation surface 2 a between the primary side electrode pair formation region 47 and the secondary side electrode pair formation region 48 , a coil formation region 49 is provided. In the preferred embodiment, the coil formation region 49 is formed in the shape of a rectangle.

In the back half of the primary side electrode pair formation region 47 , a first electrode formation region 47 A is provided, and in the front half, a second electrode formation region 47 B is provided. In the back half of the secondary side electrode pair formation region 48 , a third electrode formation region 48 A is provided, and in the front half, a fourth electrode formation region 48 B is provided.

In the first electrode formation region 47 A, the external connection electrode (the first external connection electrode) 41 B of the first electrode 41 is disposed, and in the second electrode formation region 47 B, the external connection electrode (the second external connection electrode) 42 B of the second electrode 42 is disposed. The first external connection electrode 41 B is formed, in plan view, in the shape of a rectangle, and covers a region of the first electrode formation region 47 A other than an edge portion on the side of the second electrode formation region 47 B. The second external connection electrode 42 B is formed, in plan view, in the shape of a rectangle, and covers a region of the second electrode formation region 47 B other than an edge portion on the side of the first electrode formation region 47 A.

In the third electrode formation region 48 A, the external connection electrode (the third external connection electrode) 43 B of the third electrode 43 is disposed, and in the fourth electrode formation region 48 B, the external connection electrode (the fourth external connection electrode) 44 B of the fourth electrode 44 is disposed. The third external connection electrode 43 B is formed, in plan view, in the shape of a rectangle, and covers a region of the third electrode formation region 48 A other than an edge portion on the side of the fourth electrode formation region 48 B. The fourth external connection electrode 44 B is formed, in plan view, in the shape of a rectangle, and covers a region of the fourth electrode formation region 48 A other than an edge portion on the side of the third electrode formation region 48 A.

With reference to FIGS. 119 to 124 and 126 , in the substrate 2 , the primary coil formation trench 11 A and the secondary coil formation trench 11 B are formed in the coil formation region 49 , by digging down, to a predetermined depth from the element formation surface 2 a . Each of the coil formation trenches 11 A and 11 B is formed, in plan view, in the shape of a spiral. The primary coil formation trench 11 A and the secondary coil formation trench 11 B are disposed, in plan view, such that in a gap of one trench, the other trench is disposed. However, since in the preferred embodiment, the number of windings of the secondary coil formation trench 11 B is greater than the number of windings of the primary coil formation trench 11 A, in a part of the gap on the inner peripheral side of the secondary coil formation trench 11 B, the primary coil formation trench 11 A is not disposed. In other words, the primary coil formation trench 11 A and the secondary coil formation trench 11 B are disposed, in plan view, except the part of the inner peripheral side of the secondary coil formation trench 11 B, such that they are alternately arrayed from the inner peripheral side to the outer peripheral side. Hence, the primary coil formation trench 11 A and the secondary coil formation trench 11 B are disposed so as not to intersect each other. In the preferred embodiment, the coil formation trenches 11 A and 11 B are formed, in plan view, in the shape of a quadrilateral spiral, and have a plurality of rectilinear portions parallel to the side surfaces 2 c of the substrate 2 .

The cross section (cross section in a direction perpendicular to a direction in which the coil formation trenches 11 A and 11 B are extended in the spiral direction) of the coil formation trenches 11 A and 11 B is formed in the shape of a rectangle which is long in the direction of the thickness of the substrate 2 . For example, the width of the coil formation trenches 11 A and 11 B may be 1 μm or more and 3 μm or less. For example, the depth of the coil formation trenches 11 A and 11 B may be 10 μm or more and 82 μm or less. The depth of the coil formation trenches 11 A and 11 B is preferably 10 μm or more so that the internal resistance of the coils 3 A and 3 B formed within the coil formation trenches 11 A and 11 B is decreased.

As shown in FIG. 121 , the primary coil formation trench 11 A is formed with a first trench part 11 Aa that is formed in the insulating film 7 and a second trench part 11 Ab that is formed in the substrate main body 6 and that communicates with the first trench part 11 Aa. Likewise, the secondary coil formation trench 11 B is formed with a first trench part 11 Ba that is formed in the insulating film 7 and a second trench part 11 Bb that is formed in the substrate main body 6 and that communicates with the first trench part 11 Ba.

On the inner surface of the coil formation trenches 11 A and 11 B (the second trench parts 11 Ab and 11 Bb) in the substrate main body 6 , an insulating film 12 formed with an oxide film or the like is formed. In the preferred embodiment, the insulating film 12 is formed with a thermal oxide film (SiO 2 ), and when the thermal oxide film is formed on the inner surface of the coil formation trenches 11 A and 11 B, the surrounding wall (the side wall and the bottom wall) of the coil formation trenches 11 A and 11 B (the second trench parts 11 Ab and 11 Bb) in the substrate main body 6 is thermally oxidized into an insulator portion (thermal oxide film) 30 having insulation. In the preferred embodiment, an example is described where the entire wall sandwiched by the coil formation trenches 11 A and 11 B (the second trench parts 11 Ab and 11 Bb) in the substrate main body 6 is a thermal oxide film.

On the surface of the insulating film 12 within the coil formation trenches 11 A and 11 B (the second trench parts 11 Ab and 11 Bb) and on the inner surface of the coil formation trenches 11 A and 11 B (the first trench parts 11 Aa and 11 Ba) in the insulating film 7 , a barrier metal film 13 is formed. The barrier metal film 13 is formed of, for example, TiN. The thickness of the barrier metal film 13 is about 400 to 500 angstroms. Within the coil formation trenches 11 A and 11 B, a conductive member 51 is embedded while being in contact with the barrier metal film 13 . In the preferred embodiment, the conductive member 51 is formed of tungsten (W).

The primary coil 3 A is formed with the conductive member 51 embedded within the primary coil formation trench 11 A. Hence, the primary coil 3 A is formed, in plan view, in the shape of a spiral (in the shape of a quadrilateral spiral) of the same pattern as the primary coil formation trench 11 A. Specifically, the primary coil 3 A includes a plurality of plate-shaped parts parallel to the side surfaces 2 c of the substrate 2 . The secondary coil 3 B is formed with the conductive member 51 embedded within the secondary coil formation trench 11 B. Hence, the secondary coil 3 B is formed, in plan view, in the shape of a spiral (in the shape of a quadrilateral spiral) of the same pattern as the secondary coil formation trench 11 B. Specifically, the secondary coil 3 B includes a plurality of plate-shaped parts parallel to the side surfaces 2 c of the substrate 2 . Hence, the number of windings of the secondary coil 3 B is greater than the number of windings of the primary coil 3 A.

On the element formation surface 2 a (the surface of the insulating film 7 ) of the substrate 2 , an insulating film 8 is formed so as to coat the element formation surface 2 a and the conductive member 51 (the coils 3 A and 3 B). The insulating film 8 is formed, in plan view, in the shape of a rectangle matching with the element formation surface 2 a . The insulating film 8 is formed with, for example, a USG (Undoped Silicate Glass) film. In the insulating film 8 , a first contact hole 14 A (see FIGS. 119 and 123 ) that exposes the outer peripheral side end portion of the primary coil 3 A and a second contact hole 15 A (see FIGS. 119 and 120 ) that exposes the inner peripheral side end portion of the primary coil 3 A are formed. Furthermore, in the insulating film 8 , a third contact hole 14 B (see FIGS. 119 and 122 ) that exposes the inner peripheral side end portion of the secondary coil 3 B and a fourth contact hole 15 B (see FIGS. 119 and 124 ) that exposes the outer peripheral side end portion of the secondary coil 3 B are formed. As described above, in the side surfaces 2 c of the substrate 2 and the outer peripheral surface of the insulating film 8 , the passivation film 9 formed with a nitride film or the like is formed.

On the surface of the insulating film 8 , the first electrode 41 , the second electrode 42 , the third electrode 43 , and the fourth electrode 44 are formed. With reference to FIGS. 119, 122, 123 , and 125 , the first electrode 41 includes a first electrode film 41 A that is formed on the surface of the insulating film 8 and a first external connection electrode 41 B that is bonded to the first electrode film 41 A. As shown in FIG. 119 , the first electrode film 41 A includes a drawing electrode 41 Aa that is connected to the outer peripheral side end portion of the primary coil 3 A and a first pad 41 Ab that is formed integrally with the drawing electrode 41 Aa. The first pad 41 Ab is formed to be rectangular at a corner portion of the element formation surface 2 a on the side of the first electrode formation region 47 A. The first external connection electrode 41 B is connected to the first pad 41 Ab. As shown in FIGS. 119 and 123 , the drawing electrode 41 Aa enters the first contact hole 14 A from the surface of the insulating film 8 , and is connected to the outer peripheral side end portion of the primary coil 3 A within the first contact hole 14 A. The drawing electrode 41 Aa is formed straight along a straight line that passes above one end portion of the primary coil 3 A to reach the first pad 41 Ab.

By extending the outer peripheral side end portion of the primary coil formation trench 11 A to a position below the first pad 41 Ab, the outer peripheral side end portion of the primary coil 3 A may be disposed in a position below the first pad 41 Ab. In this way, since the first contact hole 14 A can be formed in a position below the first pad 41 Ab, one end portion of the primary coil 3 A can be connected to the first pad 41 Ab. In this case, since the first electrode film 41 A can be formed with only the first pad 41 Ab, the drawing electrode 41 Aa is not needed.

The second electrode 42 includes a second electrode film 42 A that is formed on the surface of the insulating film 8 and a second external connection electrode 42 B that is bonded to the second electrode film 42 A. As shown in FIG. 119 , the second electrode film 42 A includes a drawing electrode 42 Aa that is connected to the inner peripheral side end portion of the primary coil 3 A and a second pad 42 Ab that is formed integrally with the drawing electrode 42 Aa. The second pad 42 Ab is formed to be rectangular at the corner portion of the element formation surface 2 a on the side of the second electrode formation region 47 B. The second external connection electrode 42 B is connected to the second pad 42 Ab. As shown in FIGS. 119 and 120 , the drawing electrode 42 Aa enters the second contact hole 15 A from the surface of the insulating film 8 , and is connected to the inner peripheral side end portion of the primary coil 3 A within the second contact hole 15 A. The drawing electrode 42 Aa is formed straight along a straight line that passes above the inner peripheral side end portion of the primary coil 3 A to reach the second pad 42 Ab.

With reference to FIGS. 119, 122, and 124 , the third electrode 43 includes a third electrode film 43 A that is formed on the surface of the insulating film 8 and a third external connection electrode 43 B that is bonded to the third electrode film 43 A. As shown in FIG. 119 , the third electrode film 43 A includes a drawing electrode 43 Aa that is connected to the inner peripheral side end portion of the secondary coil 3 B and a third pad 43 Ab that is formed integrally with the drawing electrode 43 Aa. The third pad 43 Ab is formed to be rectangular at the corner portion of the element formation surface 2 a on the side of the third electrode formation region 48 A. The third external connection electrode 43 B is connected to the third pad 43 Ab. As shown in FIGS. 119 and 122 , the drawing electrode 43 Aa enters the third contact hole 14 B from the surface of the insulating film 8 , and is connected to the inner peripheral side end portion of the secondary coil 3 B within the third contact hole 14 B. The drawing electrode 43 Aa is formed straight along a straight line that passes above the inner peripheral side end portion of the secondary coil 3 B to reach the third pad 43 Ab.

The fourth electrode 44 includes a fourth electrode film 44 A that is formed on the surface of the insulating film 8 and a fourth external connection electrode 44 B that is bonded to the fourth electrode film 44 A. As shown in FIG. 119 , the fourth electrode film 44 A includes a drawing electrode 44 Aa that is connected to the outer peripheral side end portion of the secondary coil 3 B and a fourth pad 44 Ab that is formed integrally with the drawing electrode 44 Aa. The fourth pad 44 Ab is formed to be rectangular at the corner portion of the element formation surface 2 a on the side of the fourth electrode formation region 48 B. The second external connection electrode 42 B is connected to the second pad 42 Ab. As shown in FIGS. 119 and 124 , the drawing electrode 44 Aa enters the fourth contact hole 15 B from the surface of the insulating film 8 , and is connected to the outer peripheral side end portion of the secondary coil 3 B within the fourth contact hole 15 B. The drawing electrode 44 Aa is formed straight along a straight line that passes above the outer peripheral side end portion of the secondary coil 3 B to reach the fourth pad 44 Ab. In the preferred embodiment, as the electrode films 41 A to 44 A, Al films are used.

By extending the outer peripheral side end portion of the secondary coil formation trench 11 B to a position below the fourth pad 44 Ab, the outer peripheral side end portion of the secondary coil 3 B may be disposed in a position below the fourth pad 44 Ab. In this way, since the fourth contact hole 15 B can be formed in a position below the fourth pad 44 Ab, the outer peripheral side end portion of the secondary coil 3 B can be connected to the fourth pad 44 Ab. In this case, since the fourth electrode film 44 A can be formed with only the fourth pad 44 Ab, the drawing electrode 44 Aa is not needed.

The first to fourth electrode films 41 A to 44 A are covered by a passivation film 16 formed with a nitride film (SiN), and furthermore, on the passivation film 16 , a resin film 17 such as polyimide is formed. In the passivation film 16 and the resin film 17 , in plan view, in regions corresponding to the vicinity of the first pad 41 Ab, the vicinity of the second pad 42 Ab, the vicinity of the third pad 43 Ab, and the vicinity of the fourth pad 44 Ab, first, second, third, and fourth cutout portions 18 A, 19 A, 18 B, and 19 B (see FIGS. 120, 122, and 125 ) are respectively formed.

A region of the surface of the first pad 41 Ab other than an edge portion on the side of the third pad 43 Ab is exposed by the first cutout portion 18 A. A region of the surface of the second pad 42 Ab other than an edge portion on the side of the fourth pad 44 Ab is exposed by the second cutout portion 19 A. A region of the surface of the third pad 43 Ab other than an edge portion on the side of the first pad 41 Ab is exposed by the third cutout portion 18 B. A region of the surface of the fourth pad 44 Ab other than an edge portion on the side of the second pad 42 Ab is exposed by the fourth cutout portion 19 B. In other words, the passivation film 16 and the resin film 17 are formed, in plan view, in the coil formation region 49 , the boundary portion region between the first electrode formation region 47 A and the second electrode formation region 47 B, and the boundary portion region between the third electrode formation region 48 A and the fourth electrode formation region 48 B.

The first, second, third, and fourth external connection electrodes 41 B, 42 B, 43 B, and 44 B fill the first, second, third, and fourth cutout portions 18 A, 19 A, 18 B, and 19 B respectively. The first external connection electrode 41 B and the third external connection electrode 43 B are formed so as to protrude from the resin film 17 , and include a drawing portion 20 that is drawn to the side of the other external connection electrode along the surface of the resin film 17 . Likewise, the second external connection electrode 42 B and the fourth external connection electrode 44 B are formed so as to protrude from the resin film 17 , and include the drawing portion 20 that is drawn to the side of the other external connection electrode along the surface of the resin film 17 .

In the preferred embodiment, the first external connection electrode 41 B is formed so as to cover not only the surface of the first electrode film 41 A (the pad 41 Ab) and the insulating film 8 exposed within the first cutout portion 18 A but also the upper end surface of the passivation film 9 on the corner portion on the side of the first pad 41 Ab of the element formation surface 2 a . The two side surfaces other than the two side surfaces on the inner side of the first external connection electrode 41 B are formed so as to be flush with the surface of the passivation film 9 covering the peripheral surface of the insulating film 8 on the corner portion of the element formation surface 2 a on the side of the first pad 41 Ab.

The second external connection electrode 42 B is formed so as to cover not only the surface of the second electrode film 42 A (the pad 42 Ab) and the insulating film 8 exposed within the second cutout portion 19 A but also the upper end surface of the passivation film 9 on the corner portion of the element formation surface 2 a on the side of the second pad 42 Ab. The two side surfaces other than the two side surfaces on the inner side of the second external connection electrode 42 B are formed so as to be flush with the surface of the passivation film 9 covering the peripheral surface of the insulating film 8 on the corner portion of the element formation surface 2 a on the side of the second pad 42 Ab.

The third external connection electrode 43 B is formed so as to cover not only the surface of the third electrode film 43 A (the pad 43 Ab) and the insulating film 8 exposed within the third cutout portion 18 B but also the upper end surface of the passivation film 9 on the corner portion of the element formation surface 2 a on the side of the third pad 43 Ab. The two side surfaces other than the two side surfaces on the inner side of the third external connection electrode 43 B are formed so as to be flush with the surface of the passivation film 9 covering the peripheral surface of the insulating film 8 on the corner portion of the element formation surface 2 a on the side of the third pad 43 Ab.

The fourth external connection electrode 44 B is formed so as to cover not only the surface of the fourth electrode film 44 A (the pad 44 Ab) and the insulating film 8 exposed within the fourth cutout portion 19 B but also the upper end surface of the passivation film 9 on the corner portion of the element formation surface 2 a on the side of the fourth pad 44 Ab. The two side surfaces other than the two side surfaces on the inner side of the fourth external connection electrode 44 B are formed so as to be flush with the surface of the passivation film 9 covering the peripheral surface of the insulating film 8 on the corner portion of the element formation surface 2 a on the side of the fourth pad 44 Ab. The external connection electrodes 41 B, 42 B, 43 B, and 44 B may be formed with, for example, a Ni/Pd/Au laminated film having a Ni film in contact with the electrode films 41 A, 42 A, 43 A, and 44 A, a Pd film formed thereon, and an Au film formed thereon. The laminated film described above can be formed by a plating method.

The passivation film 16 and the resin film 17 coat, from the surface, the coils 3 A and 3 B, the insulating film 8 , and the electrode films 41 A to 44 A in the coil formation region 49 on the element formation surface 2 a , a region between the first external connection electrode 41 B and the second external connection electrode 42 B, and a region between the third external connection electrode 43 B and the fourth external connection electrode 44 B, and function as a protective film to protect them. On the other hand, the passivation film 9 formed on the side surfaces 2 c of the substrate 2 and the outer peripheral surface of the insulating film 8 functions as a protective film to protect the side surfaces 2 c of the substrate 2 and the outer peripheral surface of the insulating film 8 .

FIG. 127 is an electrical circuit diagram showing an electrical structure within the chip transformer. One end of the primary coil 3 A (represented by a symbol L 1 in FIG. 127 ) is connected to the first electrode 41 , and the other end of the primary coil 3 A is connected to the second electrode 42 . One end of the secondary coil 3 B (represented by a symbol L 2 in FIG. 127 ) is connected to the third electrode 43 , and the other end of the secondary coil 3 B is connected to the fourth electrode 44 . In this way, it functions as a transformer.

As a parameter indicating the performance (quality) of the transformer, the Q (Quality Factor) value of the coil is present. As the Q value of the coil is increased, its loss is decreased, and the coil has an excellent characteristic as a high-frequency inductance.

The Q value of the coils 3 A and 3 B is represented by formula (9) below.

Q= 2π fL/R   (9)

In the formula (9) above, f represents the frequency of a current flowing through the coil, L represents the inductance of the coils 3 A and 3 B and R represents the internal resistance of the coils 3 A and 3 B.

In the arrangement of the third preferred embodiment of the fourth invention, in the substrate 2 , the primary coil formation trench 11 A and the secondary coil formation trench 11 B obtained by digging down from the element formation surface 2 a are formed, in plan view, in the shape of a spiral. The conductive member 51 is embedded within the primary coil formation trench 11 A and thus the primary coil 3 A is formed, and the conductive member 51 is embedded within the secondary coil formation trench 11 B and thus the secondary coil 3 B is formed. Hence, it is possible to increase the cross-sectional area of the coils 3 A and 3 B (the cross-sectional area of the coils 3 A and 3 B perpendicular to the direction in which the coils 3 A and 3 B are extended in the spiral direction), and thus it is possible to decrease the internal resistance (R in the formula (9) above) of the coils 3 A and 3 B. In this way, since the Q value of the coils 3 A and 3 B can be increased, it is possible to provide a high performance chip transformer.

In the third preferred embodiment of the fourth invention, as compared with the first preferred embodiment of the fourth invention, the primary coil 3 A and the secondary coil 3 B can be disposed close to each other, and thus it is possible to provide a higher performance chip transformer.

The coil formation trenches 11 A and 11 B are formed in the substrate 2 , the conductive member 51 is embedded within the coil formation trenches 11 A and 11 B and thus it is possible to form the coils 3 A and 3 B, with the result that the coils 3 A and 3 B are easily manufactured. In this way, it is possible to provide a chip transformer that is easily manufactured.

Furthermore, on the element formation surface 2 a , which is one surface of the substrate 2 , the external connection electrodes 41 B to 44 B of the first to fourth electrodes 41 to 44 are formed. Hence, as shown in FIG. 128 , the element formation surface 2 a is made to face a mounting substrate 91 , the external connection electrodes 41 B to 44 B are bonded on the mounting substrate 91 by a solder 92 and thus it is possible to form a circuit assembly in which the chip transformer 1 B is surface-mounted on the mounting substrate 91 . In other words, it is possible to provide a flip-chip connection-type chip transformer 1 B, and it is possible to connect the chip transformer 1 B to the mounting substrate 91 by a face-down bonding in which the element formation surface 2 a is made to face the mounting substrate 91 and wireless bonding. In this way, it is possible to decrease the occupied space of the chip transformer 1 B on the mounting substrate 91 . In particular, it is possible to realize a low profile chip transformer 1 B on the mounting substrate 91 . In this way, it is possible to effectively utilize the space within the housing of a small-sized electronic device or the like and to contribute to high-density mounting and miniaturization.

FIGS. 129A to 129L are cross-sectional views for illustrating an example of the manufacturing step of the chip transformer, and show cut surfaces corresponding to FIG. 120 . FIGS. 130 A to 130 E are partially enlarged cross-sectional views showing the details of the manufacturing step of a coil, and show cut surfaces corresponding to FIG. 121 .

First, as shown in FIG. 129A , an original substrate 50 that is an original of the substrate main body 6 is prepared. On the surface of the original substrate 50 , the insulating film 7 such as a thermal oxide film or a CVD oxide film is formed. In the preferred embodiment, the insulating film 7 is a thermal oxide film. The surface of the insulating film 7 corresponds to the element formation surface 2 a of the substrate 2 .

FIG. 131 is a schematic plan view of part of the original substrate 50 in which the insulating film 7 is formed on the surface. As shown in FIG. 131 , in the element formation surface 2 a , chip transformer regions X corresponding to a plurality of chip transformers 1 B are disposed in a matrix. Between the chip transformer regions X adjacent to each other, a boundary region Y is provided. The boundary region Y is a region in the shape of a band having a substantially constant width, extends in two directions perpendicular to each other and is formed in a lattice shape. After necessary steps are performed on the original substrate 50 in which the insulating film 7 is formed on the surface, the original substrate 50 is separated along the boundary region Y, and thus it is possible to obtain a plurality of chip transformers 1 B.

The steps performed on the original substrate 50 in which the insulating film 7 is formed on the surface are as follows. First, as shown in FIGS. 129A and 130A , by photolithography and etching, a part of the insulating film 7 that corresponds to a region in which the coil formation trench 11 A and the secondary coil formation trench 11 B need to be formed is removed. In this way, in the insulating film 7 , the first trench part 11 Aa of the primary coil formation trench 11 A and the first trench part 11 Ba of the secondary coil formation trench 11 B are formed. Then, a hard mask formed with the insulating film 7 is used, and thus the original substrate 50 is etched. In this way, as shown in FIGS. 129B and 130A , the second trench part 11 Ab of the primary coil formation trench 11 A and the second trench part 11 Bb of the secondary coil formation trench 11 B are formed in the original substrate 50 . In this way, in the insulating film 7 and the original substrate 50 , the primary coil formation trench 11 A and the secondary coil trench 11 B are formed. The coil formation trenches 11 A and 11 B may be formed by, for example, a so-called BOSCH process. The BOSCH process is a process that is generally used to make a hollow part in a MEMS (Micro Electro Mechanical System).

Then, as shown in FIGS. 129B and 130B , on the inner surface of the coil formation trenches 11 A and 11 B, the insulating film (thermal oxide film) 12 is formed by a thermal oxidization method. Here, the surrounding wall (the side wall and the bottom wall) of the coil formation trenches 11 A and 11 B (the second trench parts 11 Ab and 11 Bb) in the original substrate 50 is thermally oxidized into an insulator portion (thermal oxide film) 30 having insulation. In FIG. 129B , the insulating film 12 is omitted but the insulator portion 30 is shown. In the preferred embodiment, the entire wall sandwiched by the coil formation trenches 11 A and 12 A (the second trench parts 11 Ab and 11 Bb) in the substrate main body 6 are formed into the thermal oxide film.

Then, for example, by a sputtering method, the barrier metal film 13 made of TiN is formed on the element formation surface 2 a including the interiors of the trenches 11 A and 11 B. In this way, as shown in FIG. 130C , the barrier metal film 13 made of TiN is formed on the surfaces of the insulating film 12 and the insulating film 7 within the coil formation trenches 11 A and 11 B and the surface of the insulating film 7 outside the coil formation trenches 11 A and 11 B. Thereafter, annealing processing is performed.

Thereafter, as shown in FIGS. 129C and 130D , for example, by a CVD method, on the element formation surface 2 a including the interiors of the coil formation trenches 11 A and 11 B, the conductive member 51 formed of tungsten (W) is deposited.

Then, for example, by an etch back method, overall etching is performed on the conductive member 51 from its surface. The overall etching is continued until the surface of the conductive member 51 is flush with the surface of the insulating film 7 . In this way, as shown in FIGS. 129D and 130 E, the conductive member 51 is embedded within the coil formation trenches 11 A and 11 B while in contact with the barrier metal film 13 . By the conductive member 51 embedded within the primary coil formation trench 11 A, the primary coil 3 A in the shape of a spiral when seen in plan view is formed, and by the conductive member 51 embedded within the secondary coil formation trench 11 B, the secondary coil 3 B in the shape of a spiral when seen in plan view is formed.

Then, as shown in FIG. 129E , on the insulating film 7 , the insulating film 8 formed with a USG (Undoped Silicate Glass) film or the like is formed so as to coat the insulating film 7 (the element formation surface 2 a ) and the coils 3 A and 3 B. The insulating film 8 is formed by, for example, a CVD method. Thereafter, by photolithography and etching, in regions of the insulating film 8 corresponding to the outer peripheral side end portion and the inner peripheral side end portion of the primary coil 3 A, the first contact hole 14 A (see FIG. 123 ) and the second contact hole 15 A (see FIG. 129E ) penetrating the insulating film 8 are respectively formed. Likewise, in regions of the insulating film 8 corresponding to the inner peripheral side end portion and the outer peripheral side end portion of the secondary coil 3 B, the third contact hole 14 B (see FIG. 122 ) and the fourth contact hole 15 B (see FIG. 124 ) penetrating the insulating film 8 are respectively formed.

Then, for example, by sputtering, on the insulating film 8 including the interiors of the contact holes 14 A, 15 A, 14 B, and 15 B, an electrode film forming the first to fourth electrodes 41 to 44 is formed. In the preferred embodiment, the electrode film made of Al is formed. Thereafter, by photolithography and etching, the electrode film is patterned, and thus as shown in FIG. 129F , the electrode film is separated into the first electrode film 41 A, the second electrode film 42 A, the third electrode film 43 A, and the fourth electrode film 44 A.

Then, as shown in FIG. 129G , for example, by a CVD method, the passivation film 16 such as a nitride film is formed, and furthermore, polyimide is applied to form the resin film 17 . For example, polyimide to which photosensitivity is added is applied, and the polyimide is developed after exposure with a pattern corresponding to the first to fourth cutout portions 18 A, 19 A, 18 B, and 19 B. In this way, the resin film 17 having a cutout portion corresponding to the first to fourth cutout portions 18 A, 19 A, 18 B, and 19 B is formed. Thereafter, as necessary, heat treatment for curing the resin film is performed. Then, by dry etching using the resin film 17 as a mask, the first to fourth cutout portions 18 A, 19 A, 18 B, and 19 B are formed in the passivation film 16 .

Then, as shown in FIG. 129H , a resist mask 52 having an opening 52 a in a lattice shape matching with the boundary region Y (see FIG. 131 ) is formed. Plasma etching is performed via the resist mask 52 , and thus as shown in FIG. 129H , the original substrate 50 , the insulating film 7 , and the insulating film 8 are etched from the surface of the insulating film 8 to a predetermined depth. In this way, along the boundary region Y, a groove (scribe groove) 53 for cutting is formed.

Then, the resist mask 52 is peeled off. Thereafter, as shown in FIG. 129I , for example, by a CVD method, an insulating film 54 such as a nitride film serving as the material of the passivation film 9 is formed over the entire region of the surface of the original substrate 50 . Here, the insulating film 54 is also formed over the entire region of the inner surface (the side wall surface and the bottom wall surface) of the groove 53 .

Then, as shown in FIG. 129J , the insulating film 54 is selectively etched. Specifically, a part of the insulating film 54 other than the insulating film 54 on the side wall surface of the groove 53 (the passivation film 9 ) is removed. In this way, a part of the electrode films 41 A to 44 A that is not covered by the passivation film 16 and the resin film 17 is exposed. The insulating film 54 on the bottom surface of the groove 53 is removed.

Then, as shown in FIG. 129K , on the first to fourth electrode films 41 A to 44 A exposed from the first to fourth cutout portions 18 A, 19 A, 18 B, and 19 B, for example, by plating (preferably, electroless plating), plating growth is performed in the following order: for example, Ni, Pd, and Au. In this way, the first to fourth external connection electrodes 41 B to 44 B are formed.

Thereafter, by a DBG (Dicing Before Grinding) method, a plurality of chip transformer regions X are divided into pieces. Specifically, as shown in FIG. 129L , first, on the side of the surface of the original substrate 50 (the side of the external connection electrode), a supporting tape 71 having an adhesive surface 72 is adhered. Then, the original substrate 50 is polished from the rear surface to the bottom surface of the groove 53 . In this way, the plurality of chip transformer regions X are separated into individual chip transformers 1 B. Thereafter, on a plurality of chip transformers 1 B, the recovery step shown in FIGS. 45A to 45D or the recovery step shown in FIGS. 46A to 46C described in the first preferred embodiment of the second invention may be performed.

FIG. 132 is a partially cut perspective view of a chip transformer according to a fourth preferred embodiment of the fourth invention, FIG. 133A is a plan view showing the appearance of the chip transformer when seen from the side of the electrode and FIG. 133B is a plan view showing the internal structure of the chip transformer. FIG. 134 is a cross-sectional view taken along line CXXXIV-CXXXIV in FIG. 133B , and FIG. 135 is a partially enlarged cross-sectional view of FIG. 134 . FIG. 136 is a cross-sectional view taken along line CXXXVI-CXXXVI in FIG. 133B , FIG. 137 is a cross-sectional view taken along line CXXXVII-CXXXVII in FIG. 133B and FIG. 138 is a cross-sectional view taken along line CXXXVIII-CXXXVIII in FIG. 133B . FIG. 139 is a cross-sectional view taken along line CXXXIX-CXXXIX in FIG. 133B , and FIG. 140 is a partially enlarged cross-sectional view of FIG. 139 . FIG. 141 is a plan view showing a structure of the surface of a substrate by removing an arrangement formed on the surface of the substrate.

The chip transformer 1 C is a minute chip part and is formed in the shape of a rectangular parallelepiped. The planar shape of the chip transformer 1 B may be rectangular, the length L in the longitudinal direction may be about 0.4 mm and the length W in the lateral direction may be about 0.2 mm. The thickness T of the entire chip transformer 1 may be about 0.15 mm.

The chip transformer 1 B includes a substrate 2 , a primary coil 3 A and a secondary coil 3 B that are formed within the substrate 2 , a first electrode 41 that is connected to one end portion of the primary coil 3 A, a second electrode 42 that is connected to the other end portion of the primary coil 3 A, a third electrode 43 that is connected to one end portion of the secondary coil 3 B, and a fourth electrode 44 that is connected to the other end of the secondary coil 3 B. The number of windings of the primary coil 3 A differs from the number of windings of the secondary coil 3 B. Although in the preferred embodiment, an example where the number of windings of the secondary coil 3 B is greater than the number of windings of the primary coil 3 A is described, the number of windings of the primary coil 3 A may be greater than the number of windings of the secondary coil 3 B.

The chip transformer 1 C in the fourth preferred embodiment of the fourth invention differs from the chip transformer 1 B in the third preferred embodiment of the fourth invention in that in the surface of a primary side electrode pair (the first electrode 41 and the second electrode 42 ), a plurality of concave portions 84 A and 84 B are respectively formed. In the surface of a secondary side electrode pair (the third electrode 43 and the fourth electrode 44 ), the concave portions 84 A and 84 B are not formed.

In the following description, the “front” refers to the lower side of the plane of FIG. 133B , the “back” refers to the upper side of the plane of FIG. 133B , the “left” refers to the left side of the plane of FIG. 133B and the “right” refers to the right side of the plane of FIG. 133B .

The substrate 2 is formed in the shape of a rectangular parallelepiped, and includes a pair of main surfaces 2 a and 2 b and four side surfaces 2 c . One (the main surface 2 a on the upper surface side in FIG. 132 ) of the pair of main surfaces 2 a and 2 b is an element formation surface. In the following description, the main surface 2 a is referred to as an “element formation surface 2 a ,” and the main surface 2 b on the side opposite to the element formation surface 2 a is referred to as a “rear surface 2 b .” In the preferred embodiment, the substrate 2 is formed with a substrate main body 6 and an insulating film 7 formed on the surface thereof, and the surface of the insulating film 7 on the side opposite to the side of the substrate main body 6 is the element formation surface 2 a . In the preferred embodiment, the substrate main body 6 is formed with a silicon substrate, and the insulating film 7 is formed with a thermal oxide film (SiO 2 ). The element formation surface 2 a is formed in the shape of a rectangle in plan view when seen in a normal direction perpendicular to the element formation surface 2 a . The surface (element formation surface 2 a ) of the substrate 2 is covered by an insulating film 8 . The four side surfaces 2 c of the substrate 2 and the outer peripheral surface of the insulating film 8 are covered by a passivation film 9 such as a nitride film.

With reference to FIGS. 133B and 141 , in the element formation surface 2 a , in the left side portion thereof, a primary side electrode pair formation region 47 for the formation of primary side electrode pairs 41 and 42 is provided, and in the right side portion thereof, a secondary side electrode pair formation region 48 for the formation of secondary side electrode pairs 43 and 44 is provided. These regions 47 and 48 are formed, in plan view, in the shape of a rectangle which is long in a frontward/backward direction. On the element formation surface 2 a between the primary side electrode pair formation region 47 and the secondary side electrode pair formation region 48 , a coil formation region 49 is provided. In the preferred embodiment, the coil formation region 49 is formed in the shape of a rectangle.

In the back half of the primary side electrode pair formation region 47 , a first electrode formation region 47 A is provided, and in the front half, a second electrode formation region 47 B is provided. In the back half of the secondary side electrode pair formation region 48 , a third electrode formation region 48 A is provided, and in the front half, a fourth electrode formation region 48 B is provided.

In the first electrode formation region 47 A, the external connection electrode (the first external connection electrode) 41 B of the first electrode 41 is disposed, and in the second electrode formation region 47 B, the external connection electrode (the second external connection electrode) 42 B of the second electrode 42 is disposed. The first external connection electrode 41 B is formed, in plan view, in the shape of a rectangle, and covers a region of the first electrode formation region 47 A other than an edge portion on the side of the second electrode formation region 47 B. The second external connection electrode 42 B is formed, in plan view, in the shape of a rectangle, and covers a region of the second electrode formation region 47 B other tha