JP2001341062A - Semiconductor wafer polisher - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor wafer polisher capable of preventing a semiconductor wafer from being entirely deformed in a tapered shape in cross section by applying a load uniformly from a polishing head to the entire surface of a carrier plate. SOLUTION: A compressed air is fed from a compressor 20 to a first diaphragm 17 to apply a center load onto the carrier plate 16. On the other hand, the compressed air is fed from the compressor 20 to a second diaphragm 15 to apply an outer peripheral load onto the plate 16 for polishing. In this case, the pressure of the compressed air on both diaphragms 15 and 17 is controlled by a control part 21 so that a load is hydrostatically applied uniformly from the polishing head 13 to the entire surface of the carrier plate 16. As a result, the amount of deformation of a silicon wafer W after polishing is reduced, and the flatness of the surface of the wafer is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor wafer polishing apparatus, and more particularly to a semiconductor wafer polishing apparatus for applying a load to a carrier plate by expanding a diaphragm interposed between a polishing head and a carrier plate.

[0002]

2. Description of the Related Art The surface of a silicon wafer whose surface has been etched is mechanically and chemically polished in a polishing step which is the next step. Here, the wafer surface is finished to a smooth and distortion-free mirror surface by a polishing apparatus. The polishing apparatus includes a polishing platen on which a polishing cloth is spread on an upper surface, and a polishing head to which a plurality of silicon wafers are attached by wax. A disc-shaped carrier plate made of metal, ceramic, or glass is detachably fixed to the lower surface of the polishing head. The silicon wafer is arranged on the back surface of the carrier plate. During polishing of a wafer by this polishing apparatus, a polishing liquid (slurry) containing polishing abrasive grains such as calcined silica or colloidal silica (silica sol) is supplied to a polishing cloth on a polishing platen, and a polishing liquid is supplied between the polishing cloth and the semiconductor wafer. Polishing is performed by applying a predetermined load and a relative speed.

[0003] As a conventional polishing apparatus, there is known an apparatus for applying a polishing load to the entire carrier plate (mainly the center of the plate) by hydraulic pressure, pneumatic pressure or mechanically during polishing. Separately, during polishing, an outer peripheral load (constant static load) is applied to the outer peripheral portion of the carrier plate via an O-ring, and a central load is applied to the central portion of the carrier plate by a hydraulic or pneumatic cylinder. Devices having a mechanism for adjusting the deflection are also known.

[0004]

However, these conventional polishing apparatuses have the following disadvantages. That is, according to the former polishing apparatus, since the load is always applied to the carrier plate with a constant distribution, the shape of the wafer, which changes with the life of the polishing pad, cannot be corrected. Therefore, the silicon wafer attached to the carrier plate is thicker at the center of the carrier plate,
The outer periphery of the carrier plate was thin, that is, the whole wafer tended to have a tapered cross section. As a result, TT
There was a problem that the flatness of the wafer represented by V, SBIR was reduced.

On the other hand, in the latter conventional apparatus, the center load applied to the center portion of the carrier plate and the outer periphery of the carrier plate in response to such a change in the shape (taper) of the wafer that changes with the life of the polishing pad. It has been developed for the purpose of eliminating it by adjusting the balance with the outer peripheral load applied to the part. However, according to the latter device, the central load is a hydraulic cylinder (or air cylinder) and the outer peripheral load is via an O-ring (static load).
It is hanging out. For this reason, there has been a problem that a uniform pressure distribution cannot be obtained due to the influence of the mechanical accuracy. This is because variations occur in the wear and damage of the O-ring, the processing accuracy of the O-ring groove, the processing accuracy of the groove forming surface, and the like.

Therefore, as a result of earnest research, the inventor has made the center load applied to the center portion of the carrier plate and the outer peripheral load applied to the outer peripheral portion of the carrier plate to act on separate diaphragms, and supplied to the respective diaphragms. By controlling the pressure of the working fluid, the entire surface of the silicon wafer can be uniformly polished with hydrostatic pressure without being affected by such mechanical accuracy, and the deformation of the wafer that changes with the life of the polishing cloth can be prevented. Having found that it can be adjusted, the present invention has been completed.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor wafer polishing apparatus capable of uniformly applying a load from a polishing head to the entire carrier plate with a hydrostatic pressure. Another object of the present invention is to provide a semiconductor wafer polishing apparatus that prevents a polishing wafer from becoming tapered in cross section.

[0008]

According to a first aspect of the present invention, there is provided a polishing platen on which a polishing cloth is spread, a polishing head disposed opposite to the polishing platen, and a polishing head attached to the polishing head. A carrier plate to which a plurality of semiconductor wafers are adhered, while applying a polishing liquid to the polishing cloth, a central load is applied to a central portion of the carrier plate, and an outer peripheral load is applied to an outer peripheral portion of the carrier plate. In a semiconductor wafer polishing apparatus for polishing the semiconductor wafer by acting, a first diaphragm provided between a central portion of the polishing head and a central portion of a carrier plate, and a working fluid is supplied to the first diaphragm. First to supply
Fluid supply means, a second diaphragm provided between the outer periphery of the polishing head and the outer periphery of the carrier plate, and a second fluid supply means for supplying a working fluid to the second diaphragm; A fluid pressure control means for controlling the pressure of the working fluid supplied from the first fluid supply means and the second fluid supply means to the corresponding first diaphragm or the second diaphragm, respectively. It is a polishing device.

This polishing apparatus is not limited as long as a plurality of semiconductor wafers are of a type in which wax is adhered to a carrier plate attached to a polishing head. The number of semiconductor wafers attached to the carrier plate is not limited as long as it is two or more. As a semiconductor wafer,
For example, a silicon wafer, a gallium arsenide wafer, or the like can be used. Examples of the polishing cloth include a non-woven fabric pad, a hard urethane pad, and a CeO ₂ pad.
As the polishing liquid, for example, a mixture of calcined silica, colloidal silica (polishing abrasive), amine (processing accelerator), organic polymer (haze suppressor), and the like can be used. Colloidal silica is present in the form of a transparent or opaque milky white colloid liquid dispersed in water as primary particles without aggregation of fine silica particles.

[0010] The shapes of the first diaphragm and the second diaphragm are not limited. For example, the first diaphragm may have a disk shape in plan view, and the second diaphragm may have an annular shape in plan view. The material is an elastic substance and has a certain degree of durability against chemicals, for example, silicone rubber, fluorine rubber, EPD
M and so on. The type of working fluid that expands and contracts each diaphragm is not limited. For example, it may be a gas such as compressed air or an inert gas, or a liquid such as water or oil. The first fluid supply means and the second fluid supply means include:
It has at least a supply source of the working fluid, and is provided with a pressure pump or the like as needed. As the source here,
For example, if the working fluid is compressed air, it becomes a compressor. These first fluid supply means and second fluid supply means may be provided separately, or may serve as one fluid supply means. The method of controlling the pressure of the working fluid supplied from the first fluid supply unit and the second fluid supply unit to the corresponding first diaphragm or the second diaphragm by the fluid pressure control unit is not limited. In short, it is only necessary to perform control so that a load can be uniformly applied to the entire carrier plate from the polishing head. The control may be performed, for example, by adjusting the opening degree using a regulator.

[0011]

According to the semiconductor wafer polishing apparatus of the present invention, the polishing surface of the semiconductor wafer is polished with a polishing cloth while supplying a polishing liquid. At this time, the working fluid is supplied from the first fluid supply means to the first diaphragm, a central load is applied to the center portion of the carrier plate, and the working fluid is supplied from the second fluid supply means to the second diaphragm. Then, the outer peripheral portion of the carrier plate is polished by applying an outer peripheral load. In addition, the fluid pressure control means controls the pressure of the working fluid supplied from the first fluid supply means to the first diaphragm so as to uniformly apply a hydrostatic pressure to the entire carrier plate from the polishing head. The pressure of the working fluid supplied to the second diaphragm from the fluid supply means is controlled. As a result, the deflection of the carrier plate can be arbitrarily changed, and the amount of deformation of the semiconductor wafer attached to the carrier plate after polishing can be adjusted.
Therefore, the flatness (such as TTV) of the semiconductor wafer surface is increased.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an enlarged sectional view of a semiconductor wafer polishing apparatus according to an embodiment of the present invention during wafer polishing. In FIG. 1, reference numeral 10 denotes a batch-type polishing apparatus. The polishing apparatus 10 includes a polishing platen 12 on which a polishing pad 11 made of a hard urethane pad is spread, and a polishing head 13 disposed above the polishing table 12. And The polishing head 13 has a disk-shaped head main body 14. On the lower surface of the outer peripheral portion of the head main body 14, a thick annular flange 14a is integrally formed. Annular flange 1
A ceramic carrier plate 16 is detachably fixed to the lower end surface of 4a via a second tubular diaphragm 15 fitted in the annular groove 14d. Four silicon wafers W are attached to the back surface of the carrier plate 16 with wax.

On the other hand, a flat circular bag-shaped first diaphragm 17 is attached to the upper surface of the entire central portion of the carrier plate 16. The first diaphragm 17 is a fixed disk 1 fixed to a lower portion of the head body 14.
4b. A thick disk-shaped weight 18 is provided on the upper surface of the outer peripheral portion of the head main body 14. The weight 18 is covered from outside by a cover 18a. A rotating shaft 14c of the polishing head 13 is provided upright at the upper center of the head body 14. A rotary joint 19 is connected to the upper end surface of the rotating shaft 14c. Two flow paths are formed inside the rotary joint 19. In one channel,
A pipe a communicating with the first diaphragm 17 is attached, and a pipe b communicating with the second diaphragm 15 is attached to the other flow path. The rotary joint 19 is connected to the outer cylinder 1 mounted on the upper end of the rotary shaft 14c.
9a.

The rotary joint 19 has a compressor (first fluid supply means and second fluid supply means).
Compressed air (working fluid) from 20 is supplied via two paths c and d. One path c is a supply path of compressed air to the first diaphragm 17, and the other path d is a supply path of compressed air to the second diaphragm 15.
The regulator B1 is provided in the middle of the route c, and the regulator B2 is provided in the middle of the route d. These regulators B1 and B2 are a control unit (fluid pressure control means)
The opening is adjusted by 21. That is, the control unit 21
By adjusting the opening of the regulators B1 and B2,
The pressure of the compressed air supplied from the compressor 20 to the first diaphragm 17 and the second diaphragm 15 is controlled.

Next, a method for polishing a silicon wafer W using the polishing apparatus 10 will be described. As shown in FIG.
First, four silicon wafers W are placed on the carrier plate 1.
Wax is attached to the back surface of No. 6 at intervals of 90 degrees in the circumferential direction. Then, the carrier plate 16 is fixed to the lower surface of the first diaphragm 17 of the polishing head 13 and the lower edge surface of the second diaphragm 15. Then, at the time of polishing, the polishing surface of the silicon wafer W is polished by the polishing cloth 11 on the polishing platen 12 on which the polishing cloth 11 is spread on the upper surface while supplying the polishing liquid.

In this polishing apparatus 10, a static load is mainly applied to the carrier plate 16 by the weight 18 regardless of the central portion and the outer peripheral portion of the plate 16 when polishing the wafer. In addition, the first diaphragm 17 swelled by the compressed air supplied from the compressor 20 applies a central load to the center portion of the carrier plate 16 by hydrostatic pressure. Further, an outer peripheral load is applied to the outer peripheral portion of the carrier plate 16 by hydrostatic pressure by the second diaphragm 15 expanded by the compressed air also supplied from the compressor 20. At this time, the control unit 21 adjusts the opening degree of the regulators B1 and B2 so that a load is uniformly applied from the polishing head 13 to the entire carrier plate 16 with hydrostatic pressure, and the compression supplied to the first diaphragm 17 is controlled. The pressure of the air and the pressure of the compressed air supplied to the second diaphragm 15 are adjusted. As a result, the deflection of the carrier plate 16 can be arbitrarily changed, and the amount of deformation of the silicon wafer W attached thereto after polishing can be adjusted. Therefore, the flatness (TTV, SBIR, etc.) of the silicon wafer W adhered to the carrier plate 16 and polished is increased.

[0017]

According to the present invention, the central load applied to the central portion of the plate and the outer peripheral load applied to the outer peripheral portion of the plate are applied with hydrostatic pressure by the first diaphragm and the second diaphragm, respectively. The pressure of the working fluid supplied to the wafer is controlled by the fluid pressure control means, so that a load can be uniformly applied from the polishing head to the entire carrier plate with hydrostatic pressure, and the entire semiconductor wafer has a tapered cross section. Can be prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a state during polishing of a wafer by a semiconductor wafer polishing apparatus according to one embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 10 polishing device for semiconductor wafer, 11 polishing cloth, 12 polishing platen, 13 polishing head, 15 second diaphragm, 16 carrier plate, 17 first diaphragm, 20 compressor (first fluid supply means / second fluid Fluid supply means), 21 control unit (fluid pressure control means), W silicon wafer (semiconductor wafer).

Claims (1)

[Claims] 1. A polishing platen on which a polishing cloth is spread, a polishing head arranged opposite to the polishing platen, a carrier plate attached to the polishing head and attached with a plurality of semiconductor wafers. A polishing apparatus for polishing a semiconductor wafer by applying a central load to a center portion of the carrier plate while supplying a polishing liquid to the polishing cloth, and applying an outer peripheral load to an outer peripheral portion of the carrier plate. In the apparatus, a first diaphragm provided between a central portion of the polishing head and a central portion of the carrier plate; first fluid supply means for supplying a working fluid to the first diaphragm; A second diaphragm provided between an outer peripheral portion of the carrier plate and an outer peripheral portion of the carrier plate; and a second diaphragm for supplying a working fluid to the second diaphragm. Body supply means, and fluid pressure control means for controlling the pressure of the working fluid supplied from the first fluid supply means and the second fluid supply means to the corresponding first diaphragm or second diaphragm, respectively. A semiconductor wafer polishing apparatus provided.