JP2000246627A - Wafer polishing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer polishing method and device capable of improving the flatness of a wafer by preventing the production of thin walled section of a peripheral section. SOLUTION: In a wafer polishing device which is provided with an upper surface table, a lower surface table 23, an upper polishing cloth, which is provided on the upper surface table, a lower polishing cloth 26, which is provided on the lower surface table 23, and a carrier plate 24, which is provided with a wafer holding hole 32, arranged on the lower polishing cloth 26 on the lower surface table 23 and contacts the upper polishing cloth on the upper surface table, and has a carrier rotating mechanism which polishes the wafer W by the upper polishing cloth and the lower polishing cloth 26 by rotating the carrier plate 24, the carrier plate 24 is supported in such a way that when the carrier plate 24 is rotated, the locus of the carrier plate 24 in the peripheral edge section 35 of the wafer holding hole passes an area out of the polish working area of at least either the upper or lower polishing cloth.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a wafer polishing apparatus for polishing a surface of a wafer or the like forming an integrated circuit.

[0002]

2. Description of the Related Art A silicon wafer having a surface etched is subjected to mechanical and chemical polishing in a polishing step. For example, by polishing the surface, the surface of the wafer is finished to a smooth and distortion-free mirror surface. A general double-side polishing wafer polishing apparatus is configured as follows. That is, the upper surface plate and the lower surface plate provided opposite to each other, the polishing cloth adhered to the surface of the upper surface plate and the lower surface plate, and a disk-shaped plate disposed on the polishing cloth on the surface of the lower surface plate. A rotating shaft having a sun gear is disposed in the center of the lower platen, and an internal gear is provided around the outer periphery of the lower platen. The carrier plate is provided with a wafer holding hole for holding a wafer to be polished. A gear that meshes with the sun gear and the internal gear is provided around the outer periphery of the carrier plate, and the carrier plate revolves around the lower platen while rotating on the lower platen by rotation of the rotation shaft. .

When polishing a wafer, a predetermined load is applied between the polishing cloth and each wafer while a polishing liquid (slurry) containing polishing grains such as calcined silica or colloidal silica (silica sol) is supplied to the polishing cloth. And polishing by giving a relative speed. That is, in the case of single-side polishing, the wafer adhered to the carrier is polished while rotating each carrier by each polishing head. In the case of double-side polishing, when the rotating shaft is driven to rotate the sun gear, the carrier plate is revolved around the rotating shaft by the sun gear and the internal gear while rotating. Since a polishing load is applied to the wafer, the wafer is polished as the carrier plate rotates and revolves.

[0004]

The above-mentioned conventional wafer polishing apparatus has the following problems.
That is, when the wafer rotates, the rotation speed near the periphery of the carrier is higher than that near the center of the carrier. For this reason, the polishing amount of the peripheral portion of the wafer is increased as compared with other portions, and the peripheral portion is thinner than the central portion (so-called “drip”).
Is formed. Particularly, in the case of an 8-inch wafer, the diameter of the carrier is as large as about 600 mm, and the amount of the thin portion formed is large. As a result, TTV (Total Thickness)
Variation), SBIR (Site Back-side Ideal Rang)
e) The flatness of the wafer surface, as shown in FIG. Further, at the time of polishing, the wafer is pressed against the polishing cloth, and the polishing cloth in that portion is elastically compressed and deformed. FIG. 17 shows the state at this time. In the figure, the polishing cloths 25 and 26 undergoing elastic compression deformation give a pressing force as a restoring force to the wafer W. Since this pressing force is particularly large at the peripheral portion of the wafer 4, the outer peripheral portion of the wafer W is subjected to a greater external pressure than the central portion, and the polishing amount of the peripheral portion of the wafer W is increased. From the above, as shown in FIG. 17, a problem that the thinner portion A is formed by being polished more toward the periphery of the wafer, the surface of the wafer W becomes a convex curved surface as shown in FIG. 18, and the flatness is reduced. There was a point.

[0005] In view of the above circumstances, it is an object of the present invention to provide a wafer polishing method and a wafer polishing apparatus capable of preventing the occurrence of a thin portion at a peripheral portion and improving the flatness of a wafer. .

[0006]

According to a first aspect of the present invention, there is provided a wafer polishing apparatus comprising: an upper polishing plate, a lower polishing plate, an upper polishing cloth provided on the upper polishing plate, and a lower polishing cloth provided on a surface of the lower polishing plate. And a carrier plate provided with a wafer holding hole for holding a wafer to be polished, disposed on the lower polishing cloth of the lower platen surface, and in contact with the upper polishing cloth of the upper platen surface, and rotating the carrier plate. Thereby, in a wafer polishing apparatus having a carrier rotating mechanism for polishing a wafer with the upper polishing cloth and the lower polishing cloth, the carrier plate has a peripheral portion of the wafer holding hole when the carrier plate is rotated. The trajectory is supported so as to pass outside at least one of the polishing action areas of the upper polishing cloth and the lower polishing cloth.

In this wafer polishing apparatus, when the polishing head and the carrier plate rotate, a part of the peripheral edge of the wafer is outside the polishing action area of at least one of the upper polishing cloth and the lower polishing cloth, for example, the outer peripheral edge. It may pass outside or inside the inner periphery. For this reason, the total amount of time for the peripheral portion of the wafer to pass through the polishing area of the polishing cloth is smaller than that for the central portion. Therefore, as described above, when the peripheral portion of the wafer passes through the polishing action area of the polishing pad, it is polished more than the central portion, but the total amount of time passing through the polishing action area is small, and as a result, the polishing amount is offset. The Rukoto. In addition, at least a part of the wafer peripheral portion may always pass outside the polishing operation region of the polishing cloth, or the wafer peripheral portion may temporarily pass outside the polishing operation region of the polishing cloth.

[0008] Examples of the wafer include a silicon wafer and a gallium arsenide wafer. Examples of the polishing cloth include a hard urethane pad and a CeO ₂ pad. As the polishing liquid, for example, calcined silica, colloidal silica (polishing abrasive), amine (processing accelerator)
And a mixture of an organic polymer (haze suppressant) and the like. Colloidal silica is present as a transparent or opaque milky white colloid liquid dispersed in water as primary particles without condensation of silicate fine particles. The area of the peripheral portion of the wafer passing outside the polishing area of the polishing cloth is 10 to 30 times the entire surface area of the wafer.
%, Particularly preferably 20 to 25%. If it is less than 10%, there is an inconvenience that the shape of the wafer is not changed (the peripheral portion cannot be reduced in thickness). Also, 30
%, There is a disadvantage that the wafer peripheral portion may be cut up.

According to a second aspect of the present invention, in the wafer polishing apparatus according to the first aspect, when the carrier plate is rotated, a locus of a periphery of the wafer holding hole is the upper polishing. At least one of the cloth and the lower polishing cloth is supported so as to pass through the outer peripheral edge or the inner peripheral edge, and the polishing cloth is formed in a ring shape in plan view, and has a contour shape of the outer peripheral edge or a contour of the inner peripheral edge. It is characterized in that the shape is non-circular.

According to a third aspect of the present invention, in the wafer polishing apparatus of the second aspect, at least one notch is provided at an outer peripheral edge or an inner peripheral edge of the polishing cloth. And

For example, when the notch is formed at the outer peripheral edge of the polishing cloth, the notch is formed in such a shape that the width in the circumferential direction of the notch is closer to the center than the width of the outer peripheral edge of the polishing cloth. When it is provided on the inner peripheral edge of the cloth, the polishing pad is shaped so that the width of the polishing pad near the outer periphery becomes narrow. Specifically, the cutout portion is formed in a wavy shape, a wedge shape, or the like, but the shape may be various. By providing such a notch, the contour shape of the outer peripheral edge or the inner peripheral edge of the polishing pad is made non-circular. The number of notches may be at least one, and a plurality of notches may be provided discretely and periodically in the circumferential direction of the polishing pad. Further, the configuration in which the outer peripheral edge or the inner peripheral edge of the polishing cloth is made non-circular is not limited to the above-mentioned notch portion. Or a polygon or the like. This configuration has the following operation. That is, as described above, when the contour shape of the polishing cloth is circular, and the trajectory at the peripheral portion of the wafer is supported so as to pass through the outer peripheral edge or the inner peripheral edge of the polishing cloth as shown in FIG. The polishing amount of the peripheral portions 35 and 36 is reduced, and sagging of the wafer W is eliminated. However, in some cases, a step B as shown in FIG. 20 appears at the boundary between the wafer peripheral portions 35 and 36 and the central portion of the wafer that does not leave the polishing region at all. As the invention according to claims 4 and 5 of the present invention, for example, if the configuration shown in FIG. 12 or FIG. 13 is used, the boundary between the portion of the polishing pad that protrudes outside the polishing area and the portion that does not protrude becomes smooth, The step as shown by the symbol B in FIG. 20 becomes gentle. Specifically, for example, in the case where the notch is provided on the outer peripheral edge of the polishing cloth, the notch is formed so that the center of the polishing cloth is formed narrower, so that the outer peripheral polishing is performed even in the peripheral part of the wafer. The amount can be reduced and the amount of polishing near the center can be relatively increased. That is, a difference can be given to the polishing amount even in the peripheral portion of the wafer, and the polishing amount can be controlled. Therefore, the step B can be made gentle, and the flatness of the wafer can be improved. .

A wafer polishing apparatus according to a fourth aspect of the present invention is the wafer polishing apparatus according to any one of the first to third aspects, wherein the carrier plate has a peripheral edge of the wafer holding hole when the carrier plate is rotated. The trajectory in the portion is supported so as to pass outside the polishing action area of the upper polishing cloth and the lower polishing cloth, and the upper polishing cloth and the lower polishing cloth are different in size or shape of a contour in plan view. I do.

In this wafer polishing apparatus, when the carrier plate rotates, a part of the periphery of the wafer holding hole may be located outside the polishing area of the polishing pad, for example, outside the outer periphery or inside the inner periphery. . Therefore, the total amount of time required for the peripheral portion of the wafer held in the wafer holding hole to pass through the region of the polishing pad from the center portion is reduced. Therefore, when the wafer passes through the region of the polishing cloth, the peripheral portion is polished more as described above, but the total amount of time passing through the region is small, so that the polishing amount is offset. Further, since the upper polishing cloth and the lower polishing cloth have different sizes or shapes of the outline in plan view, the polishing state of the wafer peripheral portion differs between the upper surface and the lower surface of the wafer. Therefore, different polishing can be performed on the upper surface and the lower surface of the wafer.

[0014]

Next, embodiments of the present invention will be described with reference to the drawings. First, the base technology of the present invention will be described. FIG. 1 is an enlarged sectional view of a main part of a wafer polishing apparatus according to a first base technology. FIG. 2 is a plan view of a polishing surface plate according to the first base technology. The present technology is a wafer polishing apparatus for single-side polishing. In FIG. 1, reference numeral 10 denotes a batch type silicon wafer polishing apparatus. The polishing apparatus 10 includes a polishing platen 12 having a polishing pad 11 made of a hard urethane pad stretched on a surface thereof, and a polishing plate 4 disposed above the polishing table 12. And a polishing head 13.

As the polishing cloth 11, a hard nonwoven urethane pad ("suba") having a diameter of 200 mm and a thickness of 1.3 mm is used.
800 "manufactured by Rodel Nitta Co., Ltd.). In addition, an annular groove 11a having a width of 25 mm and a depth of 0.6 mm is formed in a peripheral portion of the polishing cloth 11 as a non-polishing area.
Are notched. The groove width is a width that allows the silicon wafer W to be polished by protruding a part of the periphery of each rotating wafer out of the polishing action area of the polishing pad 11 during wafer polishing. Since the annular groove 11a is formed thinner than the polishing action area, a part of the wafer peripheral portion protruding from the polishing action area comes into contact with the polishing cloth (annular groove 11a) with a smaller pressing force than the polishing action area. Five silicon wafers W having a diameter of 8 inches and a thickness of 725 μm
However, wax is attached at intervals of 72 degrees around the center of the head. In addition, each silicon wafer W has a notch w1 formed at the peripheral portion of each silicon wafer,
It is arranged toward the radial outside of the carrier. The rotation directions of the polishing table 12 and the polishing heads 13 are the same (see FIG. 2).

It should be noted that all the prerequisite techniques shown here and a wafer polishing apparatus according to the present invention described later may be a waxless type that does not use wax. The polishing machine of the waxless mount type uses a template in which a suction pad (such as a suede pad) is arranged in a hole having a diameter slightly larger than the diameter of the wafer, and a foam layer (nap portion) on the surface of the suction pad and a back surface of the wafer. And pure water or the like, and the wafer is handled using the surface tension of the pure water. However, in this apparatus, since the wafer is merely adsorbed to the suction pad by the surface tension of water, the force of adhering the wafer to the mounting block (carrier) is weak. Therefore, during the rotation of the mounting block, when a part of the wafer peripheral portion that once protrudes out of the polishing cloth is again pressed against the polishing surface of the polishing cloth, the wafer peripheral portion may be turned up and the wafer may be damaged. is there.

Next, a method for polishing a silicon wafer W using the polishing apparatus 10 will be described. As shown in FIGS. 1 and 2, first, five silicon wafers W are attached to each carrier 14 at an interval of 72 degrees with wax, and then each carrier 1
4 is fixed to the lower surface of the corresponding polishing head 13. Then, by lowering each polishing head 13, 0.3 kgf
Each silicon wafer W is pressed against the polishing surface of the polishing pad 11 spread on the polishing platen 12 at a pressure of / cm ² . The polishing platen 12 is rotated at 35 ± 2 rpm in the direction of the solid line arrow in FIG. 2 while maintaining this state and supplying the polishing liquid onto the polishing pad 11 at 2.0 ± 0.5 liter / min. At the same time, each polishing head 13 is rotated at 35 ± 2 rpm in the direction of the two-dot chain line arrow in FIG. Thereby, the polished surface (front surface) of each silicon wafer W is polished. The polishing time is, for example, 10 minutes.

Incidentally, in the first base technology, an annular groove 11a is formed in a peripheral portion of the polishing pad 11. Therefore, during polishing, each silicon wafer W is placed in the annular groove 11a.
The wafer is rotated while protruding a part of the wafer periphery. That is, every time the silicon wafer W rotates by a predetermined angle, the peripheral portion of the silicon wafer passes through the annular groove 11a having a smaller pressing force than when the silicon wafer W passes through the polishing action area. That is, in the conventional polishing apparatus, polishing of the portion where the notch w1 is formed progresses as compared with the central portion of the wafer, and a thin portion is generated in the notch forming portion. The amount of polishing at the peripheral portion of the wafer is suppressed by the groove 11a. Therefore, the flatness (TTV or the like) of the silicon wafer W is increased.

Next, a wafer polishing apparatus according to a second base technology of the present invention will be described with reference to FIGS. FIG.
FIG. 3 is an enlarged cross-sectional view of a main part of a wafer polishing apparatus according to a second base technology. FIG. 4 is a plan view of a polishing platen according to the second base technology. As shown in FIGS. 3 and 4, a wafer polishing apparatus 20 according to the second base technology uses a polishing cloth 11A having a regular hexagonal shape in plan view instead of the polishing cloth 11 having the annular groove 11a according to the first base technology. This is an example in which is adopted. Thus, six lug-shaped cutouts (non-polishing action areas) 11b are arranged on the peripheral edge of the polishing cloth 11A. In addition,
Other configurations are substantially the same as those of the first base technology, and thus description thereof is omitted. In the base technology, the notch 11
Since b is provided, each silicon wafer W rotates while protruding a part of the wafer peripheral edge from the polishing area of the polishing pad 11 during polishing. Therefore, the peripheral portion of the silicon wafer passes through the non-polishing area every time the silicon wafer W rotates by a predetermined angle. Since the wafer W is not polished in the non-polishing area, the amount of polishing at the peripheral portion of the wafer is suppressed and the flatness (TTV, etc.) of the silicon wafer W is increased, as in the first base technology.

Here, with reference to FIGS. 5 and 6, when a silicon wafer is actually polished by using the wafer polishing apparatus 10 according to the first base technology and a conventional polishing apparatus of the same type. The results of the flatness (SBIR) of each silicon wafer surface when a comparison experiment is performed are described. FIG.
FIG. 1 is a perspective view showing a silicon wafer polished using a wafer polishing apparatus according to a first base technology by contour lines. FIG. 6 is an explanatory diagram showing each partial flatness of the surface of the silicon wafer polished using the wafer polishing apparatus according to the first base technology. FIG. 7 is a perspective view showing a silicon wafer polished using a conventional polishing apparatus by contour lines. FIG. 8 is an explanatory diagram showing each partial flatness of the surface of a silicon wafer polished using a conventional polishing apparatus. The numerical value in each area is the SBI for evaluating flatness.
R value. Among these, the hatched portion is 0.4 μm or more.

As is clear from FIGS. 7 and 8, in the polishing by the conventional polishing apparatus, a thin portion was formed at a part of the peripheral portion of the wafer. On the other hand, as shown in FIGS. 5 and 6, in the polishing by the polishing apparatus 10 according to the first base technology, there was almost no area where the SBIR value exceeded 0.4 μm, and the flatness was improved.

Next, a first embodiment according to the present invention will be described. In FIG. 9, reference numeral 21 denotes a wafer polishing apparatus for polishing a silicon wafer, which is attached to the upper surface plate 22 and the lower surface plate 23 provided opposite to each other and to the surfaces of the upper surface plate 22 and the lower surface plate 23, respectively. Polishing cloth (upper polishing cloth) 2
5. It has a polishing cloth (lower polishing cloth) 26 and a disk-shaped carrier plate 24 arranged on the polishing cloth 26 on the surface of the lower platen 23. A rotating shaft 29 provided with a sun gear 28 is disposed at the center of the lower stool 23, and an internal gear 30 is provided around the outer periphery of the lower stool 23. Sun gear 28, rotating shaft 29, and internal gear 30
Constitute a carrier plate rotation mechanism 31. FIG. 10 shows a perspective view of the wafer polishing apparatus 21. In addition,
The upper stool 22 is omitted. As shown in FIG. 10, the carrier plate 24 is provided with a wafer holding hole 32 for holding a wafer W to be polished. A gear 33 that meshes with the sun gear 28 and the internal gear 30 is provided around the outer periphery of the carrier plate 24. While orbiting.

Each of the polishing cloths 25 and 26 is annular in plan view, and the outer peripheral shape and the inner peripheral shape are circular. However, the outer diameter is smaller and the inner diameter is larger than that of the conventional polishing cloth, and as shown in FIG.
The movement trajectory of the peripheral portion of the wafer holding hole 32 indicated by the symbol passes outside the polishing action area of the polishing pads 25 and 26, that is, outside the outer peripheral edge and inside the inner peripheral edge. Similarly,
With respect to the wafer W held in the wafer holding hole 32, the movement trajectory of the peripheral portion 36 passes outside the polishing action area of the polishing pads 25 and 26, that is, outside the outer peripheral edge and the inner peripheral edge. I have. Hereinafter, the radial width of the wafer peripheral portion 36 is referred to as an offset amount d.

In general, the higher the hardness of the polishing cloth, the smaller the compressive deformation, so that the thin portion at the peripheral portion of the wafer W becomes less noticeable. Further, the degree of occurrence of the thin portion also differs depending on the polishing load and the polishing rate. Therefore, the wafer periphery 3
Although the extent of the area of the wafer 6 is not uniquely determined, considering the hardness and the like of the polishing cloth actually used, the outer peripheral edge and the inner peripheral edge of each of the 10 to 30 of the entire surface area of the wafer as described above. %, Particularly preferably 20 to 25%. Further, the offset amount d is about 5 to 50 mm. In the figure, the offset amount d for the outer peripheral edge is shown, but the inner peripheral edge is set under the same conditions.

The wafer polishing apparatus 21 configured as described above operates as follows. First, the wafer W is held in the wafer holding hole 32, and the upper platen 22 and the lower platen 2
3 to press the wafer W, and 100 to 500 g / c
A polishing load of about m ² is applied. When the rotating shaft 29 is driven to rotate the sun gear 28 in this state, the carrier plate 24 revolves around the rotating shaft 29 by the sun gear 28 and the internal gear 30 as shown in FIG. At this time, a polishing liquid is supplied to the polishing cloths 25 and 26. When the rotation shaft 29 rotates, the wafer W rotates in the wafer holding hole 32 and revolves around the rotation center axis of the carrier plate 24. Further, since the carrier plate 24 revolves around the rotation axis 29, the wafer W relatively moves with respect to the polishing cloths 25 and 26. Its speed is between 5 and 50 m / s.

Due to the above polishing load, the polishing cloths 25 and 26 in contact with the wafer W are compressed and deformed. For this reason, in the peripheral portion 36 of the wafer pressed by the polishing cloths 25 and 26, an external pressure greater than that in the central portion is exerted by the restoring force of the polishing cloths 25 and 26, and the polishing amount is increased. However, as described above, the movement trajectory of the wafer peripheral portion 36 passes outside the polishing action area of the polishing pads 25 and 26, so that a part of the wafer W is temporarily polished with the movement of the wafer W. Since it passes through the region of the cloths 25 and 26 and passes outside the outer peripheral edge or the inside of the inner peripheral edge, the total amount of time to be polished by the polishing cloths 25 and 26 is different between the peripheral part 36 and the central part. As a result, the difference in the amount of polishing between the central portion and the peripheral portion 36 is offset. Therefore, the occurrence of a thin portion at the wafer peripheral portion 36 is prevented, and the flatness of the wafer W can be increased. FIG. 19 shows a wafer polished according to the present embodiment. According to this, it is understood that the flatness is higher than the wafer polished by the conventional polishing apparatus shown in FIG.

By the way, in the above-mentioned wafer polishing apparatus 21, as shown in FIG. 20, in some cases, a step B appears as a boundary between the wafer peripheral portion 36 and the central portion of the wafer which does not leave the polishing area at all. is there. In this case, by cutting the peripheral edges of the polishing cloths 25 and 26 in a wavy shape as shown in FIG. 12, the boundary between the peripheral edge portion 36 and the central portion becomes gentle, so that this step can be eliminated.

This step B can be eliminated in the following second and third embodiments. That is, as a second embodiment of the present invention, as shown in FIG.
A plurality of wedge-shaped cutouts 25a, 26a are provided on the outer peripheral edges of the polishing cloths 25, 26 at predetermined intervals in the circumferential direction. Other configurations are the same as those of the third embodiment. In this polishing apparatus, when the wafer W passes near the periphery of the polishing cloths 25 and 26, the peripheral portion 36 of the wafer W
5, 26 notch 25a, 26a, that is, polishing cloth 25,
26 passes outside the polishing action area. That is, as in the first embodiment, when the wafer peripheral portion 36 passes through the region of the polishing cloths 25 and 26, it is polished more than the central portion, but the total amount of time passing through the region is small. As a result, the difference in the polishing amount is offset. Therefore, the occurrence of a thin portion at the wafer peripheral portion 36 is prevented, and the flatness of the wafer W can be increased. Further, since the boundary between the wafer peripheral portion 36 and the central portion becomes gentle, the occurrence of the step B as shown in FIG. 20 is suppressed.

The shape of the cutouts 25a and 26a is not limited to the above embodiment, and the number of cutouts is arbitrary. For example, the number may be one as shown in FIG. 13 (b), or may be a wave-shaped notch as shown in FIG. 13 (c). Further, as shown in FIG. 13 (d), the notch may of course be provided on the inner peripheral edge instead of the outer peripheral edge.

Next, a third embodiment of the present invention will be described. As shown in FIG. 14, in the wafer polishing apparatus 21 according to the present embodiment, the outer periphery of the upper and lower polishing cloths 25 and 26 has a non-circular shape that is largely cut in a wavy shape.
Other configurations are the same as those of the first embodiment. In this polishing apparatus, when the wafer W passes near the peripheral edges of the polishing cloths 25 and 26, the peripheral edge portion 36 of the wafer W passes through the cut portions of the polishing cloths 25 and 26, that is, outside the polishing action area of the polishing cloths 25 and 26. You will pass. That is, similarly to the first embodiment, the wafer peripheral portion 36 is
When passing through the regions 5 and 26, it is polished more than the central portion, but since the total amount of time passing through the region is small,
As a result, the difference in the polishing amount is offset. Therefore, the occurrence of a thin portion at the wafer peripheral portion 36 is prevented, and the flatness of the wafer W can be increased. Also in the present embodiment, since the boundary between the wafer peripheral portion 36 and the central portion becomes gentle, the occurrence of the step B as shown in FIG. 20 is suppressed.

If the same effect can be obtained, the polishing pad 2
5, 26 may be of any shape, besides wavy, saw blade,
It may be elliptical as shown in FIG. Also, the wafer W
The outer peripheral portion 36 of the polishing cloths 25 and 26 may pass outside the polishing action area of the polishing cloths 25 and 26 at least either one of the outer peripheral edge and the inner peripheral edge.

Next, a fourth embodiment of the present invention will be described. As shown in FIG. 16, in the wafer polishing apparatus 21 according to the present embodiment, the inner diameter of the polishing cloth 25 and the polishing cloth 26 and the outer diameter of the polishing cloth 25 and the polishing cloth 26 are different from each other. Other configurations are the same as those of the first embodiment. In this wafer polishing apparatus 21, the wafer W
Is different between the polishing cloth 25 side and the polishing cloth 26 side. That is, when performing double-side polishing of the wafer W, the width of the wafer peripheral portion 36 that passes outside the polishing area of the polishing cloth differs between the upper surface and the lower surface of the wafer W. Therefore,
A difference can be provided in the polishing state of the peripheral portion between the upper surface and the lower surface of the wafer W.

The size and shape of the outer and inner contours of the polishing pads 25 and 26 are arbitrary. That is, the polishing cloths of various sizes and shapes used in the first to third embodiments may be freely combined. Also,
In each of the above embodiments, at least one of the outer peripheral edge and the inner peripheral edge of the polishing pad may cause the peripheral portion of the wafer to pass outside the polishing area of the polishing pad. Further, the shape of the polishing cloth shown in each embodiment can take various forms. For example, the annular groove 11a provided in the polishing cloth shown in the first base technology is
-Can be used for the polishing cloth of the fourth embodiment.

[0034]

As described above, in the wafer polishing apparatus according to the present invention, since the peripheral portion of the wafer holding hole is configured to pass outside the polishing area of the polishing pad, the thickness of the peripheral portion of the wafer is reduced. Part generation is prevented, and the flatness of the wafer can be increased.

[Brief description of the drawings]

FIG. 1 is an enlarged view of a main part of a wafer polishing apparatus shown as a first base technology of the present invention.

FIG. 2 is a plan view of a polishing platen used in the polishing apparatus.

FIG. 3 is an enlarged sectional view of a main part of a wafer polishing apparatus according to a second base technology of the present invention.

FIG. 4 is a plan view of a polishing platen used in the polishing apparatus.

FIG. 5 is a perspective view showing a silicon wafer polished using a wafer polishing apparatus according to a first prerequisite technique by contour lines.

FIG. 6 is an explanatory view showing respective partial flatnesses of a silicon wafer surface polished using a wafer polishing apparatus according to a first base technology;

FIG. 7 is a perspective view showing a silicon wafer polished using a conventional polishing apparatus by contour lines.

FIG. 8 is an explanatory view showing each partial flatness of the surface of a silicon wafer polished using a conventional polishing apparatus.

FIG. 9 is a sectional view of the wafer polishing apparatus shown as the first embodiment of the present invention.

FIG. 10 is a schematic perspective view of the wafer polishing apparatus.

FIG. 11 is a view showing a peripheral portion of a wafer holding hole of the wafer polishing apparatus.

FIG. 12 is a view showing a peripheral portion of a wafer holding hole of a wafer polishing apparatus shown as another embodiment of the present invention.

FIG. 13 is a plan view of a polishing cloth used in a wafer polishing apparatus shown as a second embodiment of the present invention.

FIG. 14 is a view showing a peripheral portion of a wafer holding hole of a wafer polishing apparatus shown as a third embodiment of the present invention.

FIG. 15 is a view showing a peripheral portion of a wafer holding hole of a wafer polishing apparatus shown as another embodiment of the present invention.

FIG. 16 is a sectional view of a wafer polishing apparatus shown as a fourth embodiment of the present invention.

FIG. 17 is a cross-sectional view showing a polishing state of a conventional wafer polishing apparatus.

FIG. 18 is a perspective view showing a silicon wafer polished using a conventional wafer polishing apparatus by contour lines, and
It is a graph which shows a cross-section height.

FIG. 19 is a perspective view showing contours of a silicon wafer polished using the wafer polishing apparatus of the present invention, and a graph showing a sectional height.

FIG. 20 is a diagram showing a step formed on a wafer.

[Explanation of symbols]

 10, 20 Wafer polishing device 11, 11A Polishing cloth 11a Annular groove 11b Notch portion 12 Polishing platen 13 Polishing head 14 Carrier 21 Wafer polishing device 22 Upper platen 23 Lower platen 24 Carrier plate 25 Polishing cloth (upper polishing cloth) 26 Polishing Cloth (lower polishing cloth) 28 Sun gear 29 Rotary shaft 30 Internal gear 31 Carrier plate rotating mechanism 32 Wafer holding hole 35 Wafer holding hole peripheral edge 36 Wafer peripheral edge W Silicon wafer (wafer)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Satoshi Shimizu 1-5-1, Otemachi, Chiyoda-ku, Tokyo Within Mitsui Material Silicon Co., Ltd. (72) Isoru Ono 1-chome, Otemachi, Chiyoda-ku, Tokyo No.5-1 Inside Mitsubishi Material Silicon Co., Ltd. (72) Keiichi Tanaka Inventor 1-1-1, Otemachi, Chiyoda-ku, Tokyo (72) Inside Yukio Kuroda, Inventor Yukio Kuroda Otemachi, Chiyoda-ku, Tokyo 1-5-1, Mitsubishi Materials Silicon Co., Ltd. (72) Inventor Kiyomi Watanabe 1-1-1, Otemachi, Chiyoda-ku, Tokyo 1-72 Mitsubishi Materials Silicon Co., Ltd. (72) Toshiyuki Suzuki Chiyoda-ku, Tokyo 1-5-1 Otemachi F-term (reference) in Mitsubishi Materials Silicon Corporation 3C058 AA07 AA09 AB01 AB08 CB01 DA06 DA18

Claims (4)

[Claims] An upper platen and a lower platen, an upper polishing cloth provided on the upper platen, a lower polishing cloth provided on a surface of the lower platen, and a wafer holding hole for holding a wafer to be polished are provided. A carrier plate disposed on the lower polishing cloth of the lower platen surface and in contact with the upper polishing cloth of the upper platen surface; by rotating the carrier plate, a wafer is formed by the upper polishing cloth and the lower polishing cloth. In a wafer polishing apparatus having a carrier rotating mechanism for polishing, the carrier plate has at least one of the upper polishing cloth and the lower polishing cloth when a trajectory at a peripheral portion of the wafer holding hole is rotated when the carrier plate is rotated. A wafer polishing apparatus supported so as to pass outside one of the polishing action areas. 2. The wafer polishing apparatus according to claim 1, wherein, when the carrier plate is rotated, a trajectory at a peripheral portion of the wafer holding hole is at least one of the upper polishing cloth and the lower polishing cloth. The polishing pad is supported so as to pass either one of the outer peripheral edges or the inner peripheral edge, and the polishing pad is formed in an annular shape in plan view, and the contour shape of the outer peripheral edge or the contour shape of the inner peripheral edge is non-circular. Wafer polishing apparatus characterized by the above-mentioned. 3. The wafer polishing apparatus according to claim 2, wherein at least one notch is provided in an outer peripheral edge or an inner peripheral edge of the polishing cloth. 4. The wafer polishing apparatus according to claim 1, wherein the trajectory of the carrier plate at a peripheral portion of the wafer holding hole when the carrier plate is rotated is the upper polishing cloth. A wafer polishing apparatus, wherein the upper polishing cloth and the lower polishing cloth are different in size or shape in plan view from each other.