Scanning deposition head for depositing particles on a wafer

The present invention relates to a deposition head arrangement for depositing particles onto a semiconductor wafer in particular, under a controlled sequence, so that the location, and amount of the particle deposition can be precisely controlled.

In the prior art, it has been known to use an aerosol carrying particles that are deposited onto semiconductor wafers and other substrates in a deposition chamber. The controlling of the density and location of such particles is of great importance, and in many instances it is desirable to deposit individual spots of particles on a wafer as well as providing full coverage of the wafers. It has also been known to apply an electrical charge between a deposition head and the wafer or substrate.

It also has been known to rotate the support tables used in deposition chambers while a thin film material is introduced into the chamber, but in general the rotation has been used primarily for a uniform coating across a wafer that is supported on the table. Such a rotatable device is shown in U.S. Pat. No. 5,688,565 for example.

It is also been known to provide a potential between the deposition head and the support table that supports the wafer, for attracting the particles that are being deposited to the wafer or substrate, in order to insure control the deposition area.

However, precise control of not only the size of the area covered by the particles but also the location of the particles on a wafer is still desired.

The present invention relates to an aerosol deposition head that can be moved relative to a rotating wafer or substrate in a deposition chamber. The deposition head has two different size discharge openings for discharging particles. The head provides precise sizing of the deposition areas. The rotating support and movable deposition head are controlled to properly place the particles on the substrate.

The apparatus used for the present invention includes a rotating support table for the substrate on which deposition is to be made. The deposition head has a central relatively small tubular discharge opening and a larger annular discharge opening surrounding the central opening. The deposition head is mounted on a support on a deposition chamber and the deposition head will move radially linearly perpendicular to the rotational axis of the substrate carrier. The line of movement of the deposition head is along an axis that intersects the rotational axis of the rotating substrate character.

The present apparatus thus provides for precisely controlling the deposition of particles in desired spots on a substrate, or permits full coverage of the substrate in a uniform layer, or permits irregular patterns to be deposited by controlling the relative rate of rotation of the substrate holder and the linear movement and position of the deposition head while also controlling the flow of the deposition material, both as to the rate of flow and whether the flow is on or off.

FIG. 1 is a schematic, fragmentary sectional view of a typical deposition chamber having a substrate holder and deposition head made according to the present invention;

FIG. 2 is a top plan view of the deposition chamber taken along line 2 — 2 in FIG. 1;

FIG. 3 is a sectional view taken along line 3 — 3 in FIG. 1;

FIG. 4 is an enlarged sectional view of the deposition head and a portion of the substrate;

FIG. 5 is a sectional view of the deposition head showing portions of the aerosol delivering tube;

FIG. 6 is a plan view of a wafer having spots of particles deposited; and

FIG. 7 is a plan view of a wafer having an annular band of particles deposited thereon.

A deposition chamber indicated generally at 10 is provided with an interior substrate carrier 12 which forms a circular table, as shown, in an interior chamber 18 that is under negative pressure from a connected vacuum source 17 . The substrate carrier 12 is supported on a rotatable shaft 14 , which is driven about an upright axis indicated at 20 using a motor 15 , driving through a gear set 15 A, as shown. Other types of drives can be utilized for rotating the substrate carrier 12 , and the mounting of the shaft 14 can be as desired, but usually it is on bearings and is sealed relative to the interior chamber 18 .

The substrate carrier 12 can support a substrate 26 in a suitable manner, so that a deposition head 24 is positioned above the substrate 26 . The substrate 26 may be a semi-conductor wafer on which particles are to be deposited on the deposition head. The deposition head 24 , as shown, has a pair of aerosol passageways forming outlet openings above the substrate, including the open end of a central tube 28 which is relatively small in diameter. The tube opening discharges the aerosol carrying particles to be deposited. The tube 28 is surrounded by an annular passageway 30 defined by an outer wall 32 of the deposition head 24 and the lower end of passageway 30 forms a second particle discharge openings. The interior of the tube 28 is connected to a first inlet portion 34 of the deposition head. The annular passageway 30 is connected to a second inlet portion 36 .

The inlet portion 34 is connected to a tube 38 that is surrounded by a larger tube 40 that opens into the inlet portion 36 (see FIGS. 3 and 5 ). The tubes 38 and 40 then can be connected to separate aerosol sources 38 A, and 40 A, respectively. The aerosol sources can have the same size and type of particles therein, or the particle sizes from each of the aerosol sources can be different so each of the passageways will deposit particles having different characteristics.

The outer tube 40 is slidably mounted through a wall of the chamber using seal assembly 42 and is driven axially through a linear drive 44 . This drive, as shown, can be a rack 46 driven by a pinion 48 . The pinion 48 is driven by a reversible motor 50 . Other linear drives can be used.

The deposition head 24 has an outwardly flared edge flange 33 at its lower end, that forms a plane that is parallel to the upper surface 26 A of the substrate 26 . The flange plane can be spaced from the surface 26 A a selected distance indicated at D 1 in FIGS. 1 and 5.

A voltage source 46 is connected between the deposition head and the substrate by connecting one terminal of the voltage source to the tube 40 and the other terminal of the voltage source to the mounting shaft 14 . The voltage can be a DC voltage that can be in the range of a few volts to about 10,000 volts DC. The voltage level is controlled with a controller 47 . The controller 47 also can be used for controlling the drive motor 15 , and the drive motor 50 . The motors 15 and 50 are controllable as to direction of rotation and speed. Also, if the motors are stepper motors the position of the substrate and the deposition head are known. If DC motors are used, sensors can be used to provide a position feedback for closed loop control.

The controller will be used for controlling the rate of transfer of aerosol materials from the sources 38 A and 48 A, by regulating flow controllers 38 B and 40 B in order to provide precise control over the deposition of particles onto the substrate 26 , which generally is a semiconductor wafer. Instead of flow controllers, orifice can be used for flow control.

By way of example, in FIG. 4, a typical flow path of the aerosol from the central tubular section 28 is illustrated, and it can be seen that the gas that carries the aerosol particles will flatten or spread out as the distance from the central axis of the central tube 28 increases. This flow is shown by the flow lines coming from the bottom of the tube. By adjusting the voltage level, the area of particle deposition can be modified. By having the voltage higher, the particles will tend to deposit straight down against the substrate as shown by the center arrows 29 . Lowering the voltage causes the particles to tend to be carried out along the flow lines shown at 56 , and thus provide a wider deposition line or spot from the tube 28 . Intermediate sizes are shown by arrows 58 .

By operating the controller 47 to rotate the shaft 14 at a selected rate, and then moving the deposition head 24 radially relative to the axis 20 of the shaft 14 , the positioning of the deposited particles can be changed significantly. If a series of spots on a substrate or wafer are desired, such as that shown in FIG. 6, the deposition can be started by operating the aerosol source 38 A to deposit the desired density of particles. The aerosol source can be shut off and then the substrate carrier can be indexed or rotated to a new position by driving motor 15 . Then the aerosol source can be turned back on, so individual spots 62 can be deposited. By controlling the voltage of the voltage source 46 the size of the spots can be controlled as well, and the number of particles actually in the spot will be known when fully controlled. The radial location of the deposited spots can be selected by positioning the deposition head with motor 50 .

If a narrow ring of particles is desired to be deposited on the wafer as shown in FIG. 7, the aerosol source 38 A can be started, and left on continuously while the substrate carrier 12 is rotated by operating drive motor 15 , resulting in a line pattern 68 similar to that shown in FIG. 7 . Uniform deposition can be obtained for example by operating the aerosol source 40 A providing a large area of deposition, and then moving the tube 40 and deposition head 26 radially in at the same time that the substrate is being rotated, to provide a uniform coating all the way to the center of the substrate. Additionally, with narrow deposition bands, and movement in and out of the tube 40 while the substrate is rotated, script can be obtained. Even printing can be made with the particles that are being deposited.

A two coordinate system for moving the deposition head and rotating the substrate, and having two different size deposition openings, greatly enhances the ability to provide deposition patterns that are desired.

Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.