Conductive pad structure and method of fabricating the same

1. Field of the Invention

The invention relates to a conductive pad structure and method of fabricating the same, and more particularly to a conductive pad structure applied to a semiconductor package with a hall sensor, and a method of fabricating the same.

2. Description of the Prior Art

A hall sensor is a transducer that varies its output voltage in response to a magnetic field. Hall sensors are used for proximity switching, positioning, speed detection, and current sensing applications.

Hall sensors are popularly used in semiconductor chips. A metal shield is often set above the hall sensor in order to prevent the magnetic field or the electric field from interfering with the hall sensor. In addition, several conductive pads are positioned on the semiconductor chip for transmitting in/out signals of the hall sensor. According to current fabricating processes, the upmost metal layer of the conductive pad is formed in the same step as the aforesaid metal shield. The metal shield and the upmost metal layer are relatively thin because they are formed in the same step. The thinness causes difficulties during the formation of the upmost metal layer, and may causes discontinuousness in the upmost metal layer.

Therefore, a novel conductive pad structure and a fabricating process thereof are provided in the present invention to form an upmost metal layer with a continuous profile.

According to a preferred embodiment of the present invention, a conductive pad structure includes a first conductive layer, a first dielectric layer covering the first conductive layer, a first contact hole disposed within the first dielectric layer, a second conductive layer filling in the first contact hole wherein the second conductive layer extends from the first contact hole to a top surface of the first dielectric layer so that the second conductive layer forms a step profile, a second dielectric layer covering the first dielectric layer, and a third conductive layer contacting and covering the step profile.

According to another aspect of the present invention, a method of fabricating a conductive pad structure includes the following steps: forming a first conductive layer; forming a first dielectric layer to cover the first conductive layer; forming a first contact hole within the first dielectric layer; filling the first contact hole with a second conductive layer, wherein the second conductive layer extends from the first contact hole to a top surface of the first dielectric layer so that the second conductive layer forms a step profile; and forming a third conductive layer to contact and cover the step profile.

These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.

FIG. 1 to FIG. 8 are drawings illustrating a fabricating method of a conductive pad structure according to a preferred embodiment of the present invention.

FIG. 9 depicts a semiconductor package with a hall sensor according to a preferred embodiment of the present invention.

FIG. 10 shows a SEM image of a conductive pad structure of the present invention.

FIG. 1 to FIG. 8 are drawings illustrating a fabricating method of a conductive pad structure according to a preferred embodiment of the present invention. A substrate 10 is provided. A first conductive pad M 1 and an inter-metal dielectric (IMD) layer 12 are formed on the substrate 10 in sequence. The substrate 10 may be a bulk silicon substrate, a germanium substrate, a gallium arsenide substrate, a silicon germanium substrate, an indium phosphide substrate, a gallium nitride substrate, a silicon carbide substrate, a silicon on insulator (SOI) substrate, or other suitable materials. The first conductive layer M 1 is preferably aluminum, a metal layer, or other suitable conductive materials. The IMD layer 12 may be a silicon oxide layer, a silicon nitride layer or other dielectrics.

As shown in FIG. 2 , a first contact hole V 1 is formed within the IMD layer 12 by utilizing a lithography and etching process, and the first conductive layer M 1 is exposed through the first contact hole V 1 . Later, as shown in FIG. 3 , a second conductive layer M 2 is formed to conformally fill in the first contact hole V 1 . The second conductive layer M 2 extends from the first contact hole V 1 to a top surface 14 of the IMD layer 12 . After that, part of the second conductive layer M 2 on the IMD layer 12 is removed so that the second conductive layer M 2 forms a step profile 16 . In detail, the second conductive layer M 2 includes a first surface 18 disposed within the first contact hole V 1 and a second surface 20 disposed on the IMD layer 12 . The first surface 18 and the second surface 20 are both parallel to the top surface 14 of the IMD layer 12 . A second conductive layer M 2 includes a sloping surface 22 which connects the first surface 18 to the second surface 20 . The first surface 18 , the second surface 20 and the sloping surface 22 form the step profile 16 . In addition, the second conductive layer M 2 within the first contact hole V 1 contacts the first conductive layer M 1 . Subsequently, an inter-metal dielectric (IMD) layer 24 is formed to cover the second conductive layer M 2 and the IMD layer 12 . The IMD layer 24 contacts the second conductive layer M 2 and the IMD layer 12 . Please refer to FIG. 4 . FIG. 4 shows a schematic top view of FIG. 3 For clarity, only the first conductive layer M 1 and the second conductive layer M 2 are shown in FIG. 4 , and other elements are omitted. Please refer to both FIG. 3 and FIG. 4 . The second conductive layer M 2 crosses the first conductive layer M 1 . In addition, the first conductive layer M 1 extends in an X direction, and the second conductive layer M 2 extends in a Y direction, wherein the X direction is different from the Y direction.

As shown in FIG. 5 , a second contact hole V 2 is formed within the IMD layer 24 by utilizing a lithography and etching process, and the second conductive layer M 2 is exposed through the second contact hole V 2 . FIG. 6 shows a schematic top view of FIG. 5 . For clarity, only the IMD layer 24 , the second conductive layer M 2 , the second contact hole V 2 and the first contact hole V 1 are shown in FIG. 6 , and other elements are omitted. Please refer to FIG. 5 and FIG. 6 . An opening of the second contact hole V 2 is greater than an opening of the first contact hole V 1 . The opening of the second contact hole V 2 overlaps the opening of the first contact hole V 1 . A region R 2 of the second contact hole V 2 entirely overlaps a region R 1 of the first contact hole V 1 to expose the step profile 16 of the second conductive layer M 2 through the second contact hole V 2 .

As shown in FIG. 7 , a third conductive layer M 3 fills in the second contact hole V 2 conformally. The third conductive layer M 3 continuously and conformally covers the step profile 16 . In other words, the third conductive layer M 3 continuously and conformally contacts the first surface 18 , the sloping surface 22 and the second surface 20 of the second conductive layer M 2 . In addition, the third conductive layer M 3 extends from the second contact hole V 2 to a top surface 28 of the IMD layer 24 . Then, the third conductive layer M 3 is patterned to remove part of the third conductive layer M 3 on the top surface 28 of the IMD layer 24 . At this point, the conductive pad structure 100 of the present invention is completed. Finally, based on different requirements, a protective layer 30 can be formed optionally on the third conductive layer M 3 to cover the third conductive layer M 3 .

FIG. 8 shows a schematic top view of FIG. 7 . For clarity, only the relative positions of the first conductive layer M 1 , the second conductive layer M 2 , the third conductive layer M 3 , the second contact hole V 2 and the first contact hole V 1 are shown in FIG. 8 , and other elements are omitted. In FIG. 8 , the first conductive layer M 1 is shown by a bold dashed line. The second conductive layer M 2 is shown by a bold dot-dashed line. The first contact hole V 1 is shown by a dashed line, and the second contact hole V 2 is shown by a dot-dashed line. As shown in FIG. 8 , the third conductive layer M 3 serves as a conductive pad, the size of the third conducive layer M 3 is greater than the opening of the first contact hole V 1 , and is also greater than the opening of the second contact hole V 2 .

FIG. 9 depicts a semiconductor package with a hall sensor according to a preferred embodiment of the present invention. As shown in FIG. 9 , the conductive pad structure of the present invention can be applied to a semiconductor package 200 with a hall sensor. The third conductive layer M 3 can contact with a wire bonding 32 so the wire bonding 32 can send out the signal of the hall sensor 34 . In addition, a protective layer 36 such as a metal layer covers the hall sensor 34 . The protective layer 36 serves as a metal shielding layer for keeping the noise disturbance from the hall sensor 34 . Please refer to both FIG. 7 and FIG. 9 . The protective layer 36 is preferably formed together with the third conductive layer M 3 using the same material in the same fabricating step. For example, firstly a preliminary third conductive layer is formed to cover the step profile 16 . At a later point in the process, the protective layer 36 will be defined and separate from the third conductive layer M 3 by patterning the preliminary third conductive layer using a lithography and etching process. Refer to both FIG. 7 and FIG. 9 for details of the position of the first conductive layer M 1 , the second conductive layer M 2 and the hall sensor 34 . Please refer to FIG. 8 and FIG. 9 . The first conductive layer M 1 extends in the X direction, and can be electrically connected to the hall sensor 34 at somewhere underneath the protective layer 36 via some interconnection. The second conductive layer M 2 is also electrically connected to the hall sensor 34 because the first conductive layer M 1 contacts the second conductive layer M 2 . The first conductive layer M 1 and the second conductive layer M 2 electrically connect to the hall sensor 34 for receiving or sending signals of the hall sensor 34 .

Please refer to FIG. 7 The conductive pad structure 100 of the present invention includes a substrate 10 . A first conductive layer M 1 covers the substrate 10 . An IMD layer 12 covers the conductive layer M 1 . A first contact hole V 1 is disposed within the IMD layer 12 . A second conductive layer M 2 fills in the first contact hole V 1 , and the second conductive layer M 2 extends from the first contact hole V 1 to a top surface 14 of the IMD layer 12 so that the second conductive layer M 2 forms a step profile 16 . In detail, the second conductive layer M 2 includes a first surface 18 disposed within the first contact hole V 1 and a second surface 20 disposed on the IMD layer 12 . The first surface 18 and the second surface 20 are both parallel to the top surface 14 of the IMD layer 12 . A second conductive layer M 2 includes a sloping surface 22 connecting the first surface 18 to the second surface 20 . The first surface 18 , the second surface and the sloping surface 22 form the step profile 16 . An IMD layer 24 covers the IMD layer 12 and the second conductive layer M 2 . A second contact hole V 2 is disposed within the IMD layer 24 . The first conductive layer M 1 , the second conductive layer M 2 and the third conductive layer M 3 are preferably aluminum, metals or other suitable materials. The ratio of thickness of the second conductive layer M 2 to the third conductive layer M 3 is 3. For example, the thickness of the second conductive layer M 2 is preferably 15000 angstroms. The thickness of the third conductive layer M 3 is preferably 5000 angstroms. The second conductive layer M 2 is relatively thick, so a higher current density can be transferred by the second conductive layer M 2 . The third conductive layer M 3 is relatively thin, therefore the protective layer 36 formed in the same fabricating step as the third conductive layer M 3 also is relatively thin. The protective layer 36 is primarily for electrostatic shielding, and therefore usually is relatively thin. The IMD layer 12 and the IMD layer 24 can be silicon oxide, silicon nitride or other dielectrics. The thickness of the IMD layer 12 is preferably 13000 angstroms. The thickness of the IMD layer 12 is preferably around 17000 angstroms to 33000 angstroms. For example, the thickest part of the IMD layer 24 is 33000 angstroms. The thinnest part of the IMD layer 24 is 17000 angstroms. Please refer to FIG. 6 . An opening of the second contact hole V 2 is greater than an opening of the first contact hole V 1 . A region R 2 of the second contact hole V 2 entirely overlaps a region R 1 of the first contact hole V 1 . Please refer to FIG. 7 again. A third conductive layer M 3 continuously covers the step profile 16 . In other words, the third conductive layer M 3 continously covers a first surface 18 , a second surface 20 and the sloping surface 22 . The third conductive layer M 2 extends from the second contact hole V 2 to a top surface 28 of the IMD layer 24 . It is noteworthy that the third conductive layer M 3 is a continuous material layer which extends from the first surface 18 to the sloping surface 22 , the second surface 20 , the second contact hole V 2 and the top surface 28 .

FIG. 10 shows a SEM image of a conductive pad structure of the present invention. As shown in FIG. 10 , the third conductive layer M 3 continuously contacts the sloping surface (marked by an arrow) of the second conductive layer M 2 .

The conductive pad structure of the present invention includes the first contact hole V 1 and the second contact hole V 2 . The opening of the second contact hole V 2 is greater than the opening of the first contact hole V 1 . The region R 2 of the second contact hole V 2 overlaps the region R 1 of the first contact hole V 1 so that the step profile 16 can be exposed through the second contact hole V 2 . In this way, the thin third conductive layer M 3 can continuously contact the step profile 16 , and the third conductive layer M 3 can also continuously extend to the top surface 28 of the IMD layer 24 .

Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.