JP4402826B2 - Semiconductor wafer polishing equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor wafer polishing apparatus, and more specifically, in order to apply the entire load of the polishing head to the outer peripheral portion of the carrier plate during polishing of the semiconductor wafer, an annular shape is provided between the outer peripheral portion of the polishing head and the outer peripheral portion of the carrier plate. The present invention relates to a dead weight type semiconductor wafer polishing apparatus in which a shock absorber is interposed.
[0002]
[Prior art]
A silicon wafer (semiconductor wafer) whose surface has been etched is mechanically and chemically polished in a polishing process which is the next process. Here, the polishing apparatus finishes the wafer surface into a smooth and undistorted mirror surface.
Hereinafter, a conventional polishing apparatus will be described with reference to FIG. FIG. 4 is an enlarged cross-sectional view of a main part showing a state during wafer polishing by a semiconductor wafer polishing apparatus according to conventional means.
As shown in FIG. 4, a polishing head 100 mounted on a conventional polishing apparatus has a disc-shaped head main body 101. A thick annular flange 101 a is integrally formed on the lower surface of the outer peripheral portion of the head body 101. An annular dovetail groove 101b is formed on the lower end surface of the annular flange 101a. An O-ring (annular buffer) 102 is fitted into the dovetail groove 101b.
A disc-shaped weight 107 is mounted on the upper surface of the head body 101. The weight 107 acts as an overall load (static load) of the polishing head 100 from the head main body 101 side to the carrier plate 103 via the O-ring 102.
[0003]
The O-ring 102 is a ring having a circular cross section obtained by molding a silicone rubber. In addition, the outer peripheral surface of the O-ring 102 is positioned at two points (partially enlarged view of FIG. 4) intersecting with one imaginary line that crosses the center point of the O-ring 102 in the ring cross section. A pair of appearing burrs 102a remains. Here, the burr 102a is an unnecessary resin piece that has cooled and solidified the molding material protruding from the gap between the upper and lower molds during mold molding. Usually, the burr 102a is removed in a deburring step after mold forming. However, it is often the case that some of them remain on the outer peripheral surface of the O-ring 102 without being completely removed.
Four silicon wafers W are bonded to the back surface (lower surface) of the carrier plate 103 with wax. Each silicon wafer W is attached at intervals of 90 degrees in a state inscribed in a virtual circle separated from the center point of the carrier plate 103 by a predetermined distance.
[0004]
On the other hand, an air cylinder 106 is suspended from the center of the inner surface of the head body 101. A disc-shaped pressure plate 105 is fixed to the lower end of the rod 106a. When the rod 106a is protruded, the pressure plate 105 moves downward, and the central portion of the carrier plate 103 is pushed downward. Accordingly, each silicon wafer W adhered to the carrier plate 103 is pressed against the polishing cloth 109 spread on the upper surface of the polishing surface plate 104 with a predetermined pressure.
In FIG. 4, reference numeral 108 denotes a relative relationship between the tip portion of the air introduction pipe 110 communicated with the air cylinder 106 and the tip portion of the air supply pipe 111 communicated with the compressed air generator (not shown). It is a rotary joint that is rotatably connected.
[0005]
In this polishing apparatus, first, a static load of the weight 107 is applied as an overall load of the polishing head 100 from the annular flange 101a to the outer peripheral portion of the carrier plate 103 via the O-ring 102 at the time of wafer polishing. The warpage and deformation of the carrier plate 103 at this time are suppressed by the center load applied to the center portion of the plate 103. This central load is obtained by causing the rod 106a of the air cylinder 106 to protrude by an appropriate amount. The silicon wafer W is subjected to surface polishing while maintaining a balance between the overall load and the center load.
Specifically, polishing is performed between the polishing cloth 109 and the silicon wafer W while supplying an abrasive (slurry) containing abrasive grains such as baked silica and colloidal silica (silica sol) to the polishing cloth 109 on the polishing surface plate 104. Polishing is performed by applying a predetermined load and a relative speed therebetween.
[0006]
[Problems to be solved by the invention]
Incidentally, the O-ring 102 incorporated in such a conventional polishing head 100 has a circular cross-sectional shape as described above. Therefore, since the O-ring 102 is unstable because it is supported at one point in the vertical direction, the O-ring 102 has a groove in the head main body 101 due to the rotational force of the polishing head 100 applied during wafer polishing or the minute lateral blurring during this rotation. It was easy to twist between the formation surface of 101b and the upper surface of the carrier plate 103.
Moreover, the dimensional tolerance of the diameter of the O-ring 102 is reduced by the burr 102a adhering to the outer peripheral surface of the O-ring 102, and the occurrence frequency of defective products of the O-ring 102 is increased.
Further, since the O-ring 102 has a circular cross section in this way, generally, a groove that can be stored so that the O-ring 102 does not jump out is a dovetail groove 101b. However, the processing of the dovetail groove 101b is difficult, the finishing accuracy of the bottom surface of the groove is unstable, and the attaching / detaching operation of the O-ring 102 in the groove is troublesome.
[0007]
Moreover, due to the difficulty of such groove processing, a step due to a processing error was easily formed on the back surface of the dovetail groove 101b (partially enlarged view of FIG. 4). Therefore, in the ring cross section, there is one contact point between the O-ring 102 and the rear surface of the dovetail groove 101b, and there is a problem that the O-ring 102 easily moves in the groove and stability is lowered.
Since the surface pressure of the O-ring 102 changes in proportion to 1.3 times the crushing allowance, even a slight dimensional difference appears as a large offset load. In addition, a slight movement of the O-ring 102 also affects the single point support.
As a result, when the static load of the weight 107 is applied to the outer peripheral portion of the carrier plate 103 during wafer polishing, the above-described twist of the O-ring 102 is coupled with the variation in mechanical accuracy of the polishing head 100 by the O-ring 102. I couldn't suppress it. For this reason, there has been a problem that the load cannot be transmitted uniformly to the entire carrier plate 103.
[0008]
Therefore, as a result of earnest research, the inventor, if the cross-sectional shape of the shock absorber is V-shaped, instead of the conventional dovetail groove, the groove is easy to process and the shock absorber receiving position is stable. A groove shape having a rectangular cross section can be adopted, and the buffer body does not twist due to the polishing pressure applied during wafer polishing. As a result, when transferring a load from the head body to the carrier plate, The present invention has been completed by discovering that a load can be transmitted uniformly over the circumference, and that the occurrence frequency of defective products of the buffer due to the remaining burrs can be reduced.
The load-deflection curve of the shock absorber is a substantially linear graph because the legs of the V-shaped shock absorber are deformed by bending due to an increase in load. For this reason, even if the dimensional difference changes, the offset load is extremely small.
On the other hand, since the solid body is crushed by the load in the O-ring, in the graph showing the relationship between the load and the deformation allowance, the load increases greatly in a quadratic curve as the amount of deformation increases.
[0009]
OBJECT OF THE INVENTION
According to the present invention, the entire load from the polishing head to the carrier plate can be uniformly transmitted over the entire circumference of the plate, and it is easy to make a groove for storing the buffer body on the head body, and the buffer body with respect to this groove can be easily manufactured. An object of the present invention is to provide a semiconductor wafer polishing apparatus that can be easily attached and detached, and that can reduce the frequency of occurrence of defective buffer bodies due to burrs.
Another object of the present invention is to provide a semiconductor wafer polishing apparatus capable of ensuring in the groove a deformation space of the buffer that can perform a sufficient function as the buffer.
[0010]
[Means for Solving the Problems]
According to the first aspect of the present invention, a polishing surface plate on which a polishing cloth is spread, a polishing head disposed opposite to the polishing surface plate, and a plurality of semiconductor wafers attached to the polishing head are attached. A carrier plate, and while supplying an abrasive to the polishing cloth, an annular buffer is interposed between the outer peripheral portion of the polishing head and the outer peripheral portion of the carrier plate, so that the outer peripheral portion of the carrier plate In the semiconductor wafer polishing apparatus that polishes the semiconductor wafer by applying a central load to the center portion of the carrier plate and applying the entire load of the polishing head, the buffer body is disposed on the outer peripheral portion of the polishing head. A ring groove having a rectangular cross-section to be stored is formed, and the shock absorber connects a pair of inclined portions in a V-shaped cross section, and burrs on the outer surfaces near the tips of both inclined portions. A molded product having a V-shaped cross section formed in the shock absorber, the tip of the pair of inclined portions abuts against the bottom wall of the ring groove, and the bent portion is outside the ring groove. By projecting, the semiconductor wafer polishing apparatus accommodated in the ring groove in a state where a gap having a V-shaped cross section exists between the pair of inclined portions .
[0011]
The polishing apparatus is not limited as long as it is of a type in which a plurality of semiconductor wafers are attached to a carrier plate attached to a polishing head by wax. The number of semiconductor wafers adhered to the carrier plate is not limited as long as it is two or more.
Examples of the semiconductor wafer include a silicon wafer and a gallium arsenide wafer.
Examples of the polishing cloth include a nonwoven fabric pad, a hard urethane pad, and a CeO ₂ pad.
Moreover, as an abrasive | polishing agent, what mixed calcination silica, colloidal silica (abrasive grain), an amine (processing acceleration | stimulation material), an organic polymer (haze suppression material) etc. is employable, for example. 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 silicic acid fine particles.
[0012]
The material and size of the annular buffer body are not limited as long as the cross-sectional shape is V-shaped. Examples of the material include silicone rubber. The angle between both inclined parts of this buffer is not limited.
Moreover, the appearance position of the burr | flash on a buffer body is the outer surface of the front-end | tip vicinity of both inclination parts. Usually, since the buffer body is formed by a pair of upper mold and lower mold, in the cross section of the buffer body, it becomes the outer surface of both inclined parts centering on the V-shaped line symmetry axis.
The shape of the groove in which the buffer body is accommodated is a rectangular cross section in consideration of the ease of manufacturing the groove and the ease of attaching and detaching the buffer body to the groove.
[0013]
Further, the volume of the buffer may be 80 to 90% of the volume of the groove. If the volume of the buffer is less than 80%, the deformation of the buffer in the groove becomes too large, and the outer periphery of the polishing head and the outer periphery of the carrier plate come into contact with each other during wafer polishing, and the effect as a buffer is obtained. I can't get it. Furthermore, if the volume of the buffer exceeds 90%, the deformation of the buffer is constrained by the groove, and the buffer cannot be sufficiently deformed during wafer polishing, and a buffer that is harder than the actual buffer is used. Only the deformation at the time of doing can be obtained.
[0014]
[Action]
According to the present invention, since the cross section of the buffer body is V-shaped, it is easier to manufacture the groove than in the prior art. For example, a groove having a rectangular cross section can be formed on the outer periphery of the polishing head. Also, the buffer can be easily attached to and detached from the groove. In addition, the storage position of the buffer in the groove is also stable. Furthermore, since the shock absorber has a V-shaped cross section, the shock absorber does not twist even when the entire load is applied to the outer peripheral portion of the carrier plate. Therefore, the entire load from the polishing head to the carrier plate can be transmitted uniformly over the entire circumference of the plate.
Furthermore, since the cross-sectional shape of the buffer body is V-shaped, the appearance position of the burr at the time of molding the buffer body can be the outer surface in the vicinity of the tips of both inclined portions . Accordingly, when accommodating the cushion in the groove, even if a relatively large burr remains, no little effect on uniform transfer of the entire load from the polishing head to a carrier plate. Therefore, the frequency of occurrence of defective buffer bodies due to remaining burrs is significantly reduced.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is an enlarged sectional view of an essential part showing a state during polishing of a silicon wafer by a silicon wafer polishing apparatus according to one embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of a buffer incorporated in a silicon wafer polishing apparatus according to one embodiment of the present invention. FIG. 3 is an enlarged cross-sectional view of a shock absorber incorporated in a silicon wafer polishing apparatus according to another embodiment of the present invention.
In FIG. 1, reference numeral 10 denotes a batch type polishing apparatus. The polishing apparatus 10 has a polishing surface plate 12 with a polishing cloth 11 made of a hard urethane pad stretched on its surface, and a polishing head 13 disposed above this. And.
The polishing head 13 has a disk-shaped head body 14. A thick annular flange 14 a is integrally formed on the lower surface of the outer peripheral portion of the head body 14. A ring groove 14b having a rectangular cross section is engraved in a ring shape on the lower end surface of the annular flange 14a. An annular buffer (V ring) 15 is fitted in the ring groove 14b. A ceramic carrier plate 16 is detachably supported by the head body 14 via the buffer 15.
[0016]
The buffer body 15 is a ring in which silicone rubber is molded in a V-shaped cross section. The volume of the buffer 15 is designed to be 83% of the volume of the ring groove 14b.
In addition, a pair of burrs 15 a that appear at the time of molding the mold are attached to the buffer body 15. The specific position of the burr 15a is the position opposite to the outer surface of the outer edge of each inclined portion 15b around the V-shaped line symmetry axis a in the cross section of the shock absorber 15 (see FIG. 2). . Further, at the time of fitting into the ring groove 14b, the buffer body 15 is fitted in a state where both inclined portions 15b are compressed from both sides. At this time, the bent portion 15 c of the buffer body 15 protrudes outward from the ring groove 14 b, and this protruding portion is pressed against the upper surface of the carrier plate 16. The bent portion 15c is tapered so that both sides of the buffer body 15 are 83% of the volume of the ring groove 14b.
Instead of the buffer body 15, a buffer body 15A similar to the V-shaped cross section shown in FIG. The feature of this buffer 15A is that the outer corners of the outer edges of both inclined portions 15b are chamfered, and the bent portion 15c has a semicircular cross section.
[0017]
As shown in FIG. 1, four silicon wafers W are adhered to the back surface (lower surface) of the carrier plate 16 with wax. On the other hand, a disk-shaped pressure plate 17 is detachably fixed to the upper surface of the central portion of the plate 16 via a pyramidal silicone rubber (not shown).
An air cylinder 18 is suspended from the center of the inner surface of the head body 14. A pressure plate 17 is fixed to the lower end of the rod 18a. When the rod 18a is protruded, the pressure plate 17 moves downward, and the central portion of the carrier plate 16 is pushed downward. Therefore, each silicon wafer W adhered to the carrier plate 16 is pressed against the polishing pad 11 of the polishing surface plate 12 with a predetermined pressure.
A disc-shaped weight 19 is mounted on the head body 14, and the entire load (static load) of the polishing head 13 by the weight 19 is applied to the carrier plate 16 via the buffer body 15. .
In FIG. 1, reference numeral 20 denotes a relative relationship between a tip portion of an air introduction pipe 21 communicated with the air cylinder 18 and a tip portion of an air supply pipe 22 communicated with a compressed air generator (not shown). It is a rotary joint that is rotatably connected to.
[0018]
At the time of wafer polishing, the static load of the weight 19 acts on the outer peripheral portion of the carrier plate 16 from the annular flange 14a through the buffer body 15. At this time, when a large load is applied to the outer peripheral portion of the carrier plate 16, only the outer peripheral portion of the plate 16 is pushed and bent toward the polishing surface plate 12. As a result, the carrier plate 16 is warped and deformed, but this is reduced by the center load applied to the center of the carrier plate 16 by the air cylinder 18. That is, the surface of the silicon wafer W is polished while maintaining the balance between the overall load and the center load.
Specifically, the polishing cloth 11 on the polishing surface plate 12 is supplied with a polishing agent containing abrasive grains such as baked silica and colloidal silica while supplying a predetermined load between the polishing cloth 11 and the silicon wafer W. This is done by giving a relative speed.
[0019]
As described above, the static load from the head body 14 to the carrier plate 16 is transmitted through the buffer body 15. As the buffer body 15, the one having a V-shaped cross section that can make the appearance position of the burr 15 a be the outer surface of the both inclined portions 15 b is employed. If such a V-shaped buffer 15 is used, the ring groove shape can be replaced with the conventional dovetail groove, and the groove can be easily manufactured and the buffer body 15 can be easily attached and detached. A ring groove 14b having a rectangular cross section that stabilizes the housing position of the body 15 can be formed.
[0020]
Further, since the cross-sectional shape of the buffer body 15 is V-shaped in this way, the buffer body 15 is buffered by a load from the head main body 14 during wafer polishing, for example, rotational force of the polishing head 13 or minute lateral blur of the polishing head 13. The body 15 is not easily twisted between the formation surface of the ring groove 14 b of the head body 14 and the upper surface of the carrier plate 16. As a result, when the buffer body 15 transmits the entire load from the head main body 14 to the carrier plate 16, the buffer body 15 can transmit the load uniformly over the entire circumference of the plate 16.
[0021]
And by making it V shape, it becomes possible to make the appearance position of the burr | flash 15a into the outer surface of both the inclination parts 15b. Thus, even when a slightly larger burr 15a is attached when the buffer body 15 is stored in the ring groove 14b, there is almost no influence on the uniform transmission of the static load. As a result, the occurrence frequency of defective products of the buffer body 15 due to the burr 15a can be reduced.
Further, since the volume of the buffer 15 is 83% of the volume of the ring groove 14b, it is possible to secure a sufficient deformation space for the buffer 15 to function as a buffer in the ring groove 14b during wafer polishing. it can. As a result, during wafer polishing, from the outer peripheral portion of the polishing head 13 to the outer peripheral portion of the carrier plate 16 via the buffer 15, for example, sudden fluctuations such as fluctuations in the rotational force of the polishing head 13 and lateral blurring of the polishing head 13 occur. Even if pressure is applied, it can be absorbed well.
[0022]
【The invention's effect】
According to this invention, since the cross-sectional shape of the buffer body is V-shaped, and the appearance position of unnecessary burrs that occur at the time of mold forming is the outer surface of both inclined portions in the cross-section of the buffer body, A load can be transmitted uniformly to the other member. In addition, the degree of freedom in selecting the shape of the groove for accommodating the buffer body is increased, and the frequency of occurrence of defective buffer bodies due to burrs can be reduced .
[Brief description of the drawings]
FIG. 1 is an enlarged cross-sectional view of a main part showing a state during wafer polishing by a semiconductor wafer polishing apparatus according to an embodiment of the present invention;
FIG. 2 is an enlarged cross-sectional view of a buffer incorporated in a semiconductor wafer polishing apparatus according to an embodiment of the present invention.
FIG. 3 is an enlarged cross-sectional view of a shock absorber incorporated in a semiconductor wafer polishing apparatus according to another embodiment of the present invention.
FIG. 4 is an enlarged cross-sectional view of a main part showing a state during wafer polishing by a semiconductor wafer polishing apparatus according to conventional means.
[Explanation of symbols]
10 Semiconductor wafer polishing equipment,
11 Abrasive cloth,
12 Polishing surface plate,
13 Polishing head,
14 grooves,
15,15A buffer,
16 carrier plate,
W Silicon wafer (semiconductor wafer)

Claims (1)

A polishing surface plate on which the polishing cloth is stretched;
A polishing head disposed opposite to the polishing platen;
A carrier plate attached to the polishing head, to which a plurality of semiconductor wafers are attached,
While supplying an abrasive to the polishing cloth, an annular buffer is interposed between the outer periphery of the polishing head and the outer periphery of the carrier plate, and the entire load of the polishing head acts on the outer periphery of the carrier plate. In the semiconductor wafer polishing apparatus for polishing the semiconductor wafer by applying a central load to the center of the carrier plate,
On the outer periphery of the polishing head, a ring groove having a rectangular cross section for accommodating the buffer is formed,
The shock absorber is a molded product having a V-shaped cross section in which a pair of inclined portions are connected in a V-shaped cross section, and burrs are formed on the outer surfaces in the vicinity of the tips of both inclined portions, respectively.
The buffer body has a V-shaped cross section between the pair of inclined portions, with the ends of the pair of inclined portions abutting against the bottom wall of the ring groove and the bent portion protruding outward from the ring groove. A polishing apparatus for a semiconductor wafer accommodated in the ring groove in a state in which a gap of shape exists .

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