JP2007266299A - Wafer-polishing apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wafer-polishing apparatus and method, which can control the thrust of a wafer to be a desired value all over the surface, particularly, can control the thrust of the edge part of the wafer locally to be the desired value, and can maintain the quality of the wafer. <P>SOLUTION: The wafer-polishing apparatus holds a wafer W by a holder head 14, and pushes the wafer against a polishing pad 20 and polishes it through the holder head. The holder head is equipped with a carrier to push the wafer against the polishing pad, a retainer ring arranged in the perimeter of the carrier, a plurality of toric elastic members arranged concentrically on the underside of the carrier, and an air supply line to supply pressurized gas to the air chamber in the interior of the elastic member, wherein the zone rubber ring 52D of the outermost periphery is arranged at the position to press the marginal part of the wafer, the pressing plane 53A is formed so that the pressing distribution is formed in the radial direction of the wafer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wafer polishing apparatus and method, and more particularly, to a wafer polishing apparatus and method suitable for polishing a wafer or the like by chemical mechanical polishing (CMP).

  Polishing of a wafer by CMP is performed by pressing the wafer against a rotating polishing pad with a predetermined pressure while rotating the wafer, and supplying a mechanochemical abrasive between the polishing pad and the wafer. At this time, the wafer is surrounded by a retainer ring, and the back side is held by the carrier and pressed against the polishing pad.

  At this time, when a back plate that is arranged on the back surface of the wafer W and presses the wafer W is pressed by mechanical means, a structure is likely to apply a load to a part of the back plate. For example, a case where an air cylinder or the like is used is typical. In this case, when a load is applied to a part of the back plate, the back plate is locally deformed, and the deformation affects the wafer W, and there is a concern that the polishing accuracy may be adversely affected.

  Therefore, in the conventional wafer polishing apparatus, for example, as shown in FIG. 7, the back plate 4 is pressed through the airbag 1 in the head body 2 so that the wafer W is pressed uniformly. Yes. Further, as shown in FIG. 8, there is a case where the wafer W is directly pressed by the airbag 1. With these configurations, the wafer W is pressed uniformly.

  7 and 8, the wafer W is polished by the polishing pad 20 attached to the upper surface of the polishing surface plate 12. Further, the periphery of the wafer W is held by the retainer ring 3.

  Furthermore, a zone pressurization method has been proposed in which the air bag press method is improved so that the wafer W is pressed uniformly (see, for example, Patent Documents 1 and 2).

This is because a plurality of airbags of different sizes are formed in a donut shape, arranged concentrically, and the radial pressure of the wafer W is controlled so that the wafer W is pressed more uniformly. It is composed, and the expected effect is obtained.
Japanese Patent No. 3595266 JP 2004-363505 A

  However, in these various conventional wafer polishing apparatuses, a problem has been pointed out that the shape of the edge portion of the wafer W is still not formed in a desired shape. This phenomenon will be described with reference to FIG.

  FIG. 9 is a partially enlarged cross-sectional view around the left end of the wafer W. In the same figure, the zone 1 is pressed by the airbag 1, and the pressing force at the left end of the wafer W is uniform as shown by the arrows. On the other hand, the polishing pad 20 in contact with the left end portion of the wafer W is in a state where it is locally crushed downward (indicated by 20A).

  In such a case, the polishing amount of the edge portion of the wafer W becomes smaller than the other portions, and the edge shape after processing becomes a shape that rises, resulting in a defect in the quality of the wafer W.

  In order to cope with this, although it is considered that the width of the zone pressurizing portion of the airbag 1 is decreased and the polishing pressure of the locally collapsed portion 20A is locally increased, the width of the airbag 1 is set to a predetermined value. Processing to a length (for example, 10 mm) or less is not practical because of restrictions on the material of the airbag 1 and the pressing force.

  The present invention has been made in view of such circumstances, and can control the pressing force of the wafer to a desired value over the entire surface, and in particular, control the pressing force of the edge portion of the wafer to a desired value locally. As a result, an object of the present invention is to provide a wafer polishing apparatus and method capable of maintaining the quality of a wafer.

  In order to achieve the above object, the present invention provides a wafer polishing apparatus that holds a wafer with a holding head and presses the wafer against the polishing pad via the holding head to polish the wafer. A carrier to be pressed against the carrier, a retainer ring disposed around the carrier, a plurality of annular elastic members arranged concentrically below the carrier, and a pressurized gas in the air chamber inside the elastic member An air supply line for supplying the outer peripheral surface, and the elastic member on the outermost periphery is disposed at a position for pressing the peripheral portion of the wafer, and a pressure distribution is formed in the radial direction of the wafer. Provided is a wafer polishing apparatus in which a pressing surface of an elastic member is formed.

  To this end, the present invention provides a wafer polishing method in which a wafer is held by a holding head, and the wafer is pressed against the polishing pad via the holding head to polish the wafer, and the wafer is pressed against the holding head against the holding head. A carrier, a retainer ring disposed around the carrier, a plurality of annular elastic members arranged concentrically below the carrier, and a pressurized gas supplied to an air chamber inside the elastic member An air supply line is provided, and the wafer polishing method is characterized in that the peripheral portion of the wafer is pressed by the outermost elastic member so that a pressing force distribution is formed in the radial direction.

  According to the present invention, it is provided with a plurality of annular elastic members arranged concentrically on the lower side of the carrier, the outermost elastic member is arranged at a position pressing the peripheral portion of the wafer, and the diameter of the wafer Since the pressing surface is formed so that the pressing force distribution is formed in the direction, the peripheral portion of the wafer can be pressed so that the pressing force distribution is formed in the radial direction. Thereby, the pressing force at the edge portion of the wafer can be locally controlled to a desired value, and as a result, the quality of the wafer can be maintained.

  In the present invention, the pressing surface of the outermost elastic member is preferably formed so as to have a thickness distribution in the radial direction. Thus, if the pressing surface of the elastic member is formed so as to have a thickness distribution in the radial direction, it is possible to easily press the peripheral portion of the wafer so that the pressing force distribution is formed in the radial direction. . In addition, as another structure for pressing so that a pressing force distribution is formed in the radial direction, for example, the thickness of the elastic member is made uniform, and a protrusion is formed on a predetermined diameter portion of the pressing surface of the elastic member. The mode to do can be adopted.

  In the present invention, the elastic member is preferably formed of ethylene propylene rubber (EPDM), silicon rubber, urethane rubber, or nitrile rubber (NBR). Such various rubber members are suitable as pressing members.

  Moreover, in this invention, it is preferable that the said elastic member is 20-60 by A hardness prescribed | regulated by JISK6301. An elastic member having such characteristics is suitable as a pressing member.

  In the present invention, it is preferable that a radial width of the outermost elastic member is 10 mm or less. Such a radial width is suitable for local pressing control.

  As described above, according to the present invention, the pressing force at the edge portion of the wafer can be locally controlled to a desired value, and as a result, the quality of the wafer can be maintained.

  Hereinafter, preferred embodiments of a wafer polishing apparatus and method according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a perspective view showing the overall configuration of the wafer polishing apparatus 10. As shown in the figure, the wafer polishing apparatus 10 is mainly composed of a polishing surface plate 12 and a wafer holding head 14.

  The polishing surface plate 12 is formed in a disk shape, and a rotating shaft 16 is connected to the center of the lower surface thereof. The polishing surface plate 12 rotates in the direction of arrow A by driving a motor 18 connected to the rotating shaft 16. A polishing pad 20 is attached to the upper surface of the polishing surface plate 12, and a mechanochemical abrasive (slurry) is supplied onto the polishing pad 20 from a nozzle (not shown).

  As shown in FIG. 2, the wafer holding head 14 mainly includes a holding head main body 22, a carrier 24, a carrier pressing means 26, a retainer ring 28, a retainer ring pressing means 30, a protective sheet 52, a control means such as air. Yes.

  The holding head main body 22 is formed in a disc shape, and a rotary shaft 32 (see FIG. 1) is connected to the center of the upper surface thereof. The holding head main body 22 is driven by a motor (not shown) connected to the rotary shaft 32 and rotates in the direction of arrow B in FIG.

  The carrier 24 is formed in a disc shape and is arranged at the lower center of the holding head body 22. A drive plate 34 is provided between the center of the upper surface of the carrier 24 and the lower center of the holding head main body 22, and the rotation is transmitted from the holding head main body 22 via the pins 36.

  An operating transformer 38 is provided between the center lower portion of the drive plate 34 and the center upper portion of the carrier 24 so that the vertical movement amount of the carrier 24 relative to the holding head main body 22 can be detected with high accuracy. Specifically, an operating transformer main body 38A is fixed to the lower center of the drive plate 34, and a core 38B of the operating transformer is fixed to the upper upper center of the carrier 24.

  Further, a carrier pressing member 40 is provided on the peripheral edge of the upper surface of the carrier 24. The carrier 24 receives a pressing force from the carrier pressing means 26 via the carrier pressing member 40.

  Further, a suction / blowout groove 42 is formed on the lower surface of the carrier 24 as a supply path for sucking air or injecting pure water (DIW). A fluid channel (not shown) formed inside the carrier 24 is communicated with the suction / blowout groove 42. An intake pump and a pure water supply source are connected to the fluid flow path via a fluid pipe (not shown). The suction of the air from the suction / blowing groove 42 and the discharge of pure water are performed by switching between the intake pump and the pure water supply source.

  The above-described suction / blowing groove 42, fluid flow path, fluid piping, intake pump, pure water supply source, switching means between the intake pump and the pure water supply source, and the like constitute an air control means.

  The carrier pressing means 26 is disposed on the periphery of the central portion of the lower surface of the holding head main body 22, and applies a pressing force to the carrier pressing member 40 to transmit the pressing force to the carrier 24 coupled thereto. The carrier pressing means 26 is preferably composed of a rubber sheet airbag 46 that expands and contracts by air intake and exhaust. An air supply mechanism 48 for supplying air is connected to the airbag 46, and the air supply mechanism 48 is provided with a regulator (not shown) that adjusts the pressure of air pumped from a pump (not shown).

  The airbag 46 is preferably made of a rubber sheet such as chloroprene rubber, but other materials such as a flexible resin material can also be used.

  The retainer ring 28 is formed in a ring shape and is disposed on the outer periphery of the carrier 24. The retainer ring 28 is attached to a holder (retainer ring holder) 50 provided on the wafer holding head 14, and a protective sheet (not shown) can be stretched on the inner periphery of the retainer ring 28 as necessary. . In the configuration of FIG. 2, protective sheets 52A, 52B, 52C and a zone rubber ring 52D, which will be described later, are employed instead of the protective sheet that covers the entire lower surface of the carrier 24.

  The retainer ring holder 50 is formed in a ring shape, and an annular recess 54 is formed on the lower surface thereof. On the other hand, a convex portion 56 that fits into the concave portion 54 is formed on the upper surface of the retainer ring 28. By fitting the convex portion 56 into the concave portion 54 of the retainer ring holder 50, the retainer ring 28 is retained by the retainer ring 28. Attached to the ring holder 50.

  The retainer ring 28 is fixed to the retainer ring holder 50 by fitting the convex portion 56 to the concave portion 54 of the retainer ring holder 50 and then screwing it with a plurality of bolts (not shown). For this reason, screw holes (not shown) are formed in the retainer ring 28 at regular intervals, and through holes (not shown) are formed in the retainer ring holder 50 at regular intervals.

  The combination of the retainer ring 28 and the retainer ring holder 50 is preferably used when a protective sheet covering the entire lower surface of the carrier 24 is stretched.

  The retainer ring holder 50 is attached to an attachment member 64 formed in a ring shape via a snap ring 66. A retainer ring pressing member 68 is connected to the mounting member 64. The retainer ring 28 is transmitted with a pressing force from the retainer ring pressing means 30 via the retainer ring pressing member 68.

  The retainer ring pressing means 30 is disposed on the outer peripheral portion of the lower surface of the holding head main body 22, and applies a pressing force to the retainer ring pressing member 68 to press the retainer ring 28 coupled thereto against the polishing pad 20. The retainer ring pressing means 30 is also preferably formed of a rubber sheet airbag 70 in the same manner as the carrier pressing means 26. An air supply mechanism 72 for supplying air is connected to the airbag 70, and the air supply mechanism 72 is provided with a regulator (not shown) that adjusts the pressure of air pumped from a pump (not shown).

  The airbag 70 is preferably made of a rubber sheet such as chloroprene rubber, but other materials such as a flexible resin material can also be used.

  Three concentric grooves are provided on the lower surface of the carrier 24, and protective sheets 52A, 52B, 52C, which are elastic members, and a zone rubber ring 52D are attached so as to cover the grooves 24A, 24B, 24C. Each of the protective sheets 52A, 52B, 52C and the zone rubber ring 52D constitutes an airbag.

  An air flow path (not shown) formed inside the carrier 24 is communicated with the airbag (the protective sheets 52A, 52B, 52C, and the zone rubber ring 52D). An air supply source is connected to the air flow path via an air pipe and a pressure control valve (not shown). And the air pressure in each airbag (protection sheet 52A, 52B, 52C and zone rubber ring 52D) can be controlled independently.

  Within the outermost peripheral groove 24C on the lower surface of the carrier 24, a protective sheet 52C is disposed on the inner peripheral side, and a zone rubber ring 52D is disposed on the outer peripheral side (inside the circle a in the figure). The zone rubber ring 52D is an elastic member having a U-shaped cross section (channel shape). An example of the arrangement and cross-sectional shape of the zone rubber ring 52D is shown in FIG.

  This zone rubber ring 52D is suspended inward from the pressing surface 53A, side wall surfaces 53B (outer peripheral side) and 53C (inner peripheral side) suspended from both ends of the pressing surface 53A, and upper ends of the sidewall surfaces 53B and 53C. And extending sides 53D and 53E. Then, when air pressure is applied to the inside 53F of the zone rubber ring 52D, the zone rubber ring 52D functions as a pressing means.

  Although there is no restriction | limiting in particular as a material of the zone rubber ring 52D which is this elastic member, It is preferable that they are ethylene propylene rubber (EPDM), silicon rubber, urethane rubber, or nitrile rubber (NBR). This is because such a member is excellent in flexibility, durability, stain resistance and the like, and is suitable for the object of the present invention.

  Further, the zone rubber ring 52D preferably has an A hardness specified by JIS K6301 of 20 to 60. This is because such a member has appropriate flexibility and is suitable for the object of the present invention.

  Although there is no restriction | limiting in particular about the thickness of zone rubber ring 52D, The range of 0.4-1.0 mm is preferable. If it is less than 0.4 mm, the durability may be inferior, whereas if it exceeds 1.0 mm, the flexibility may be inferior.

  The width in the radial direction of the zone rubber ring 52D, that is, the width of the pressing surface 53A is not particularly limited, but is preferably 10 mm or less. This is because such a width is suitable for controlling the local pressing of the edge portion of the wafer.

  Although there is no restriction | limiting in particular about the supply pressure to the inside 53F of the zone rubber ring 52D, The range of 1-100 kPa is preferable.

  The pressing surface 53A of the zone rubber ring 52D is preferably formed so as to have a thickness distribution in the radial direction (left-right direction in FIG. 3). Hereinafter, this operation will be described. FIG. 4 is a cross-sectional view showing the configuration of the zone rubber ring 52D, and a pressure distribution corresponding to the thickness distribution of the pressing surface 53A. Note that symbols j, f, and g in parentheses in FIG. 4 correspond to symbols in a cross-sectional view in FIG. 5 described later.

  FIG. 4J shows a conventional zone rubber ring having a uniform pressing surface 53A (no thickness distribution), and the pressure distribution is also substantially uniform.

  In FIG. 4 (f), the upper surface of the pressing surface 53A is linear, the lower surface is a convex arc, and the thickness distribution of the pressing surface 53A is thick at the center so that it corresponds to the left and right. It is a line-symmetric shape. Accordingly, the pressure distribution has a pattern in which the central portion is high and decreases toward the left and right.

  In FIG. 4G, about 右側 on the right side of the pressing surface 53A is about twice as thick as the other part, and this part is convex downward in a stepped manner. Accordingly, the pressure distribution has a pattern in which the right side is high and decreases toward the left side.

  As described above, the zone rubber ring 52D in FIGS. 4 (f) and 4 (g) differs from the conventional example in FIG. 4 (j) by forming a thickness distribution on the pressing surface 53A, thereby obtaining a desired pressure corresponding thereto. Distribution can be obtained. Hereinafter, similar examples will be described with reference to FIG.

  FIG. 5 is a cross-sectional view showing the configuration of the zone rubber ring 52D. In the zone rubber ring 52D shown here, the right side in the left-right direction is the inner peripheral side (side wall surface 53C) and the left side is the outer peripheral side (side wall surface 53B), unlike the above-described FIGS.

  In FIG. 5A, the upper surface of the pressing surface 53A is a horizontal straight line, and the lower surface is a straight line descending toward the left side (outer peripheral side), and the thickness distribution of the pressing surface 53A corresponds to this. The taper shape increases linearly (by first-order correlation) from the inner peripheral side toward the outer peripheral side.

  In FIG. 5 (b), the upper surface of the pressing surface 53A is a horizontal straight line, and the lower surface is a straight line descending toward the right side (inner peripheral side), and the thickness distribution of the pressing surface 53A also corresponds to this. The taper shape increases linearly (by first-order correlation) from the outer peripheral side toward the inner peripheral side.

  In FIG. 5C, the upper surface of the pressing surface 53A is a horizontal straight line, the lower surface is V-shaped, and the thickness distribution of the pressing surface 53A is linear from the center to both sides corresponding to this. It is a Yamagata that decreases (by the first-order correlation).

  In FIG. 5D, the upper surface of the pressing surface 53A is a horizontal straight line, and the lower surface is also a horizontal straight line. However, a step-like protrusion is formed at the center of the lower surface, and the thickness of the pressing surface 53A. The thickness distribution is about twice as thick as the other portions so that the thickness distribution also corresponds to this.

  In FIG. 5E, the upper surface of the pressing surface 53A is a horizontal straight line, and the lower surface is also a horizontal straight line, but an arc-shaped protrusion is formed at the center of the lower surface, and the thickness of the pressing surface 53A. Only the protrusion is thicker than the other parts so that the thickness distribution corresponds to this.

  FIGS. 5 (f) and 5 (g) are as described above with reference to FIG.

  FIGS. 5H and 5I are different from the examples described so far in that the pressing surface 53A has a uniform thickness (no thickness distribution).

  In FIG. 5H, a step-like protrusion is formed at the center of the lower surface of the pressing surface 53A, and the center of the upper surface is also formed in a concave shape so as to follow this. Even with such a configuration, the pressing force at the center can be locally increased.

  In FIG. 5 (i), a step-like protrusion is formed on the left side (outer peripheral side) of about 1/3 of the pressing surface 53A, and the left side of the upper surface (outer peripheral side) of about 1/3 is also recessed to follow this. Is formed. Even with such a configuration, the pressing force on the left side (outer peripheral side) can be locally increased.

  FIG. 5 (j) is a conventional example already described with reference to FIG.

  The wafer polishing method of the wafer polishing apparatus 10 configured as described above is as follows.

  First, the wafer W is held by the wafer holding head 14 and placed on the polishing pad 20. At this time, the wafer W is sucked and held by using the sucking / blowing grooves 42 formed on the lower surface of the carrier 24.

  Next, air is supplied to the airbags 46 and 70 from a pump (not shown). At the same time, air is supplied to each airbag (protective sheets 52A, 52B, 52C and zone rubber ring 52D) of the carrier 24 (supply pressure 1 to 100 kPa). Thereby, the internal pressure of each airbag becomes high. Next, the airbags 46 and 70 are inflated, and the wafer W and the retainer ring 28 are pressed against the polishing pad 20 with a predetermined pressure. In this state, the polishing surface plate 12 is rotated in the direction of arrow A in FIG. 1, and the wafer holding head 14 is rotated in the direction of arrow B in FIG. Then, slurry is supplied from a nozzle (not shown) onto the rotating polishing pad 20. Thereby, the lower surface of the wafer W is polished by the polishing pad 20.

  The edge portion of the wafer W during polishing will be described with reference to FIG. FIG. 6 is a partially enlarged sectional view around the left end portion of the wafer W, and is an example in which the type of FIG. 5G is used as the zone rubber ring 52D. FIG. 6 corresponds to FIG. 9 described above showing a conventional example.

  A plurality of arrows shown below the zone rubber ring 52D are pressing forces at the respective locations of the zone rubber ring 52D. As described above, since the pressing force distribution can be formed in the width direction (radial direction) of the zone rubber ring 52D, the uneven pressing force applied to the edge portion of the wafer W in the conventional polishing can be corrected (locally). As a result, the polishing quality of the wafer W can be maintained.

  The configuration described above is an embodiment of the present invention, but the configuration of the present invention is not limited to these, and various configurations can be adopted.

  For example, in the embodiment of the present invention, the wafer holding head 14 shown in FIG. 2 is used. However, wafer holding heads having various configurations other than this may be used. The same effect as the form can be obtained.

  Specifically, instead of the airbags (protective sheets 52A, 52B, 52C) in the wafer holding head 14 shown in FIG. 2, a protective sheet that is stretched inside the retainer ring 28 and covers the entire lower surface of the carrier 24 is provided. Can be adopted. Therefore, the zone rubber ring 52D is disposed on the back surface of the protective sheet.

  In this case, the protective sheet is formed in a circular shape, a plurality of holes are formed, and the peripheral edge portion is sandwiched between the retainer ring 28 and the retainer ring holder 50, thereby being stretched inside the retainer ring 28. The Rukoto.

  An air layer is formed between the carrier 24 and the protective sheet below the carrier 24 on which the protective sheet is stretched. The wafer W is pressed against the carrier 24 through this air layer. The internal pressure of the air layer is increased by blowing air from the blowing groove 42 of the carrier 24. The holes formed in the protective sheet act as suction holes when the wafer W is held and transported. At the time of polishing, air communicates from this hole, so that the protective sheet is only interposed in the air layer 74 and does not act on the back surface of the wafer W.

  However, since the pressing force of the zone rubber ring 52D is independently controlled, the zone rubber ring 52D operates similarly to the example of this embodiment.

The perspective view which shows the whole structure of a wafer polisher Vertical section showing the configuration of the wafer holding head Perspective view showing the arrangement of the zone rubber ring Cross-sectional view showing the configuration and pressure distribution of the zone rubber ring Sectional view showing the configuration of the zone rubber ring Partial enlarged sectional view around the left edge of the wafer Sectional drawing which shows the structure of the principal part of the holding head of a prior art example Sectional drawing which shows the structure of the principal part of the holding head of a prior art example Partial enlarged sectional view around the left edge of the conventional wafer

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Wafer polisher, 12 ... Polishing surface plate, 14 ... Wafer holding head, 20 ... Polishing pad, 22 ... Holding head main body, 24 ... Carrier, 26 ... Carrier pressing means, 28 ... Retainer ring, 30 ... Retainer ring pressing means 46 ... Airbag, 52A, 52B, 52C ... Protective sheet, 52D ... Zone rubber ring, 70 ... Airbag, W ... Wafer

Claims (6)

In a wafer polishing apparatus for holding a wafer with a holding head and pressing the wafer against the polishing pad via the holding head for polishing,
The holding head is
A carrier for pressing a wafer against the polishing pad;
A retainer ring disposed around the carrier;
A plurality of annular elastic members disposed concentrically below the carrier;
An air supply line for supplying pressurized gas into the air chamber inside the elastic member,
The outermost elastic member is arranged at a position for pressing the peripheral portion of the wafer, and the pressing surface of the outermost elastic member is formed so that a pressing force distribution is formed in the radial direction of the wafer. A wafer polishing apparatus.   The wafer polishing apparatus according to claim 1, wherein a pressing surface of the outermost elastic member has a thickness distribution in a radial direction.   The wafer polishing apparatus according to claim 1, wherein the elastic member is formed of ethylene propylene rubber, silicon rubber, urethane rubber, or nitrile rubber.   The wafer polishing apparatus according to any one of claims 1 to 3, wherein the elastic member has an A hardness specified by JIS K6301 of 20 to 60.   The wafer polishing apparatus according to any one of claims 1 to 4, wherein the outermost elastic member has a radial width of 10 mm or less. In a wafer polishing method of holding a wafer with a holding head and polishing the wafer by pressing the wafer against a polishing pad via the holding head,
In the holding head,
A carrier for pressing a wafer against the polishing pad;
A retainer ring disposed around the carrier;
A plurality of annular elastic members disposed concentrically below the carrier;
An air supply line for supplying pressurized gas into the air chamber inside the elastic member,
A wafer polishing method, wherein the outer peripheral elastic member presses a peripheral portion of a wafer so that a pressing force distribution is formed in a radial direction.

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