Polishing pad and wafer polishing method

Abstract

A polishing pad ( 1 ) is provided with higher polishing efficiency for polishing an outer circumferential edge part ( 3 d, 3 e ) of a disc-shaped wafer ( 3 ). An unpolished part is less likely to occur during a polishing process with the polishing pad ( 1 ), and the polished wafer ( 3 ) is cleanable easily. In the polishing pad ( 1 ), a polishing surface is formed of a polishing body, and the polishing body includes a base material and polishing particles. The base material is composed of a binder resin and fibers and has a plurality of pores formed therein. The polishing particles are retained in the base material or in the pores and are diamond particles. The polishing pad ( 1 ) has a durometer hardness in a range from 16 to 27, a density in a range from 0.58 to 0.81 g/cm 3 , and an elastic modulus in a range from 21.5 to 37.5 N/mm 2 .

1 . A polishing pad for polishing an outer circumferential edge part of a disc-shaped wafer, comprising:
 a polishing body that includes: a base material composed of a binder resin and fibers and having a plurality of pores formed therein; and polishing particles retained in the base material or in the pores, the polishing body constituting a polishing surface,   wherein the polishing particles are diamond particles,   a durometer hardness is in a range from 16 to 27,   a density is in a range from 0.58 to 0.81 g/cm 3 , and   an elastic modulus is in a range from 21.5 to 37.5 N/mm 2 .   
     
     
         2 . The polishing pad according to  claim 1 ,
 wherein the polishing body includes a filler retained in the base material or in the pores.   
     
     
         3 . The polishing pad according to  claim 2 ,
 wherein the fibers are fibers in a fibrous web, and the binder resin, the polishing particles, the pores and the filler are contained in the fibrous web.   
     
     
         4 . The polishing pad according to  claim 3 ,
 wherein the binder resin is a thermoplastic polyurethane resin or a polyvinylidene fluoride resin, and the fibers are polypropylene fibers.   
     
     
         5 . The polishing pad according to  claim 4 ,
 wherein the binder resin is in a range from 12 to 14 vol %, the polishing particles are in a range from 2.2 to 14.3 vol %, the fibers are in a range from 5.1 to 10.2 vol %, the filler is in a range from 8 to 24 vol %, and the pores are in a range from 34.6 to 68.5 vol %.   
     
     
         6 . A wafer polishing method, comprising:
 a first step of preparing a wafer, a polishing pad, and a polishing liquid: and   a second step of polishing the wafer with the polishing pad while supplying the polishing liquid between the wafer and the polishing pad,   wherein the wafer has: a central axis: a front surface that extends in a direction substantially orthogonal to the central axis: a rear surface that is positioned opposite to the front surface and extends in the direction substantially orthogonal to the central axis: an outer circumferential surface that connects an outer circumferential edge of the front surface and an outer circumferential edge of the rear surface; and an outer circumferential edge part that is formed by the front surface or the rear surface and the outer circumferential surface,   the polishing pad has a polishing body that includes: a base material composed of a binder resin and fibers and having a plurality of pores formed therein: and polishing particles retained in the base material or in the pores, and the polishing body constitutes a polishing surface,   in the polishing pad, the polishing particles are diamond particles,   a durometer hardness is in a range from 16 to 27,   a density is in a range from 0.58 to 0.81 g/cm 3 , and   an elastic modulus is in a range from 21.5 to 37.5 N/mm 2 , and   in the second step, while water is used as the polishing liquid, the polishing surface is pressed against the outer circumferential edge part at a predetermined pressing force. and at least one of the wafer and the polishing pad is caused to rotate relative to the other around the central axis.