Polishing pad and method for polishing notches in wafers

Abstract

Provided are: a polishing pad with which wasting of wafers having notches can be minimized as much as possible, and which allows for a short machining time while not causing chipping in notches; and a method for polishing notches in such wafers. A polishing pad 1 according to the present invention has a polishing surface 3 constituted of a polishing body comprising: a base material 13 containing a binder resin and having a plurality of pores 15a, 15b formed therein; and abrasive grains 11 held in the base material 13 or in the pores 15a, 15b. The binder resin is polyvinylidene fluoride or a thermoplastic polyurethane. The abrasive grains 11 are diamond. The polishing pad 1 has a density of 0.9-1.2 g / cm3, a durometer hardness (D) of 26-47, and a compressive elastic modulus of 1645.1-3241.7 MPa.

Description

Polishing pad and wafer notch polishing method

[0001] The present invention relates to a polishing pad and a method for polishing a wafer notch.

[0002] Patent Documents 1 to 4 disclose conventional polishing pads. The polishing pads in Patent Documents 1 to 3 are made by impregnating a nonwoven fabric with a paste and then removing the solvent from the paste. The paste in Patent Document 1 consists of urethane, a solvent such as dimethylformamide, abrasive particles such as SiO2, and alkaline fine particles such as sodium carbonate. The paste in Patent Document 2 consists of an ether-based urethane and a solvent such as N,N-dimethylformamide. The paste in Patent Document 3 consists of urethane, a solvent, and a water repellent. By removing the solvent by drying or the like, the urethane is solidified while bonded to the nonwoven fabric. The polishing pad in Patent Document 4 is made using a paste obtained by mixing a binder resin, abrasive particles, and a solvent.

[0003] The polishing pad of Patent Document 1 is used to polish the outer peripheral edge of a disk-shaped wafer made of silicon or the like used in manufacturing semiconductor devices. Specifically, the wafer is held on a rotating table that can rotate around its center of rotation. The central axis of the wafer is positioned at the center of rotation of the rotating table. Meanwhile, the polishing pad is mounted on the upper end of a spindle so that the outer peripheral edge of the polishing pad abuts against the outer peripheral edge of the wafer. A polishing liquid is then supplied between the outer peripheral edge of the wafer and the outer peripheral edge of the polishing pad, and the rotating table and spindle are rotated while a predetermined load is applied. This allows the outer peripheral edge of the wafer to be polished. This makes it possible to suppress the occurrence of defects in semiconductor devices due to the outer peripheral edge of the wafer.

[0004] JP 2019-46838 A JP 2019-118981 A JP 2020-49639 A Japanese Patent No. 5511266

[0005] However, in addition to the central axis that forms the center of the arc, a wafer may have a notch that indicates the direction of the crystal axis. This is because the area to be cut out from a large-diameter wafer becomes large, resulting in wasted wafer.

[0006] In the case of a wafer having such a notch, if the front or back surface is polished without taking any measures to address the notch, chipping or cracking will occur near the notch during polishing, resulting in wasted wafer.

[0007] Furthermore, in consideration of mass production, it is desirable to shorten the processing time, while there is also a demand for no chipping or the like occurring in the notch.

[0008] The present invention has been made in consideration of the above-mentioned conventional situation, and aims to provide a polishing pad that can minimize waste of wafers having notches, shorten the processing time, and prevent chipping in the notch, as well as a method for polishing the notch of such wafers.

[0009] The polishing pad of the present invention is formed in an annular shape centered on a first rotation axis, and has an annular first surface extending in a direction substantially perpendicular to the first rotation axis, an annular second surface extending in a direction substantially perpendicular to the first rotation axis and positioned opposite the first surface, and a polishing surface connecting the first surface and the second surface on the outer periphery, and is a polishing pad that polishes a notch formed in a disk-shaped wafer and indicating the direction of a crystal axis by rotating the pad around the first rotation axis while pressing the polishing surface against the notch, and the polishing surface is constituted by an abrasive body that includes a base material containing a binder resin and having a plurality of pores formed therein, and abrasive particles held in the base material or the pores, the binder resin being polyvinylidene fluoride or thermoplastic polyurethane, the abrasive grains being diamond, and has a density of 0.9 to 1.2 g / cm 3 The durometer hardness (D) is 26 to 47, and the compressive modulus is 1645.1 to 3241.7 MPa.

[0010] The present invention also provides a method for polishing a wafer notch, 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 extending in a direction substantially perpendicular to the central axis, a back surface located opposite to the front surface and extending in a direction substantially perpendicular to the central axis, and a notch cut from the front surface to the back surface and indicating the direction of a crystal axis; the polishing pad is formed in an annular shape centered on a first rotation axis; the polishing pad has an annular first surface extending in a direction substantially perpendicular to the first rotation axis, an annular second surface extending in a direction substantially perpendicular to the first rotation axis and located opposite to the first surface, and a polishing surface connecting the first surface and the second surface on the outer periphery; and the polishing surface is constituted by an abrasive body including a base material containing a binder resin and having a plurality of pores formed therein, and abrasive particles held in the base material or the pores. The binder resin is polyvinylidene fluoride or thermoplastic polyurethane, the abrasive grains are diamond, and the density is 0.9 to 1.2 g / cm 3 a durometer hardness (D) of 26 to 47; and a compressive modulus of elasticity of 1645.1 to 3241.7 MPa; and in the second step, the first rotation axis is perpendicular to the central axis, and the polishing pad is rotated around the first rotation axis while pressing the polishing surface against the notch, using the polishing liquid that does not contain the abrasive particles.

[0011] The polishing pad of the present invention has a polishing surface formed of an abrasive body containing a base material and abrasive particles. The base material contains a binder resin and has a plurality of pores formed therein. The abrasive particles are held within the base material or the pores. Therefore, when the polishing pad of the present invention is used to polish a wafer notch using the notch polishing method of the present invention, excellent followability can be achieved when the pad is pressed against the notch, resulting in good polishing.

[0012] The polishing pad of the present invention uses polyvinylidene fluoride or thermoplastic polyurethane as the binder resin, diamond as the polishing abrasive grains, and has a specific density, durometer hardness (D), and compressive modulus. Test results by the inventors have shown that these properties reduce processing time while reducing or eliminating chipping and cracking near the notch.

[0013] According to the present invention, it is possible to minimize waste of wafers having notches, shorten the processing time, and prevent chipping of the notches. Furthermore, according to the present invention, since a polishing liquid containing no abrasive particles or only a small amount of abrasive particles can be used, the amount of abrasive particles remaining on the wafer after polishing is small, and the wafer can be easily cleaned after polishing.

[0014] FIG. 1 relates to polishing pads of Examples 1 to 10, with FIG. 1A being a plan view and FIG. 1B being a cross-sectional view. FIG. 2 is an enlarged cross-sectional view of the polishing pads of Examples 1 to 10. FIG. 3 is a 500x SEM photograph of the polishing pad of Example 1. FIG. 4 is a 2000x SEM photograph of the polishing pad of Example 1. FIG. 5 is a 5000x SEM photograph of the polishing pad of Example 1. FIG. 6 is a 500x SEM photograph of the polishing pad of Example 1 showing a large pore. FIG. 7 is a 500x SEM photograph of the polishing pad of Example 1 showing another large pore. FIG. 8 relates to a wafer before polishing used in the notch polishing method of Examples 1 to 6, with FIG. 8A being a plan view and FIG. 8B being a cross-sectional view. FIG. 9 is a partially enlarged side view of a wafer before polishing used in the notch polishing method of the Examples. FIG. 10 is a schematic plan view showing the notch polishing method of Examples 1 to 6. Fig. 11 is a schematic side view showing the notch polishing method of Examples 1 to 6. Fig. 12 is a partially enlarged plan view of a wafer after polishing by the notch polishing method of Examples 1 to 6. Fig. 13 is a partially enlarged side view of a wafer after polishing by the notch polishing method of Examples 1 to 6. Fig. 14 is a schematic enlarged cross-sectional view of the polishing pad of Examples 1 to 6 during polishing. Fig. 15 is a schematic enlarged cross-sectional view of the polishing pad of Examples 1 to 6.

[0015] The polishing pad of the present invention has a polishing surface formed by an abrasive body, which contains a matrix and abrasive particles. The matrix contains a binder resin and has a plurality of pores formed therein. The abrasive particles are held within the matrix or the pores. This polishing pad is an abrasive-containing polishing pad, also known as an LHA (Loosely Held Abrasive) pad.

[0016] The binder resin is polyvinylidene fluoride or thermoplastic polyurethane. The LHA pad can use, as the binder resin, polyether, rigid foam polyurethane, epoxy resin, polyethersulfone resin, as well as fluorine-based synthetic resins such as polyvinyl fluoride, vinyl fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyethylene resin, polymethyl methacrylate, etc. However, according to the test results of the inventors, polyvinylidene fluoride or thermoplastic polyurethane is preferred for the polishing pad of the present invention in terms of followability, flexibility, etc.

[0017] Diamond is used as the abrasive particles. Although the LHA pad can use silica, ceria, alumina, zirconia, titania, manganese oxide, barium carbonate, chromium oxide, boron carbide, iron oxide, etc. as abrasive particles, according to the inventors' test results, diamond is preferred for the polishing pad of the present invention because of its high Knoop hardness and good polishing durability.

[0018] According to the test results of the inventors, the polishing pad of the present invention has a density of 0.9 to 1.2 g / cm 3 The durometer hardness (D) is preferably 26 to 47, and the compressive modulus of elasticity is preferably 1645.1 to 3241.7 MPa.

[0019] According to the results of the inventors' tests, it is particularly preferable for the polishing body to contain silica particles held within the matrix or pores. Silica particles are softer than the diamond abrasive particles and provide a flexible support for the diamond.

[0020] It is particularly preferable that the pores consist of fine pores forming a three-dimensional network structure and large pores having a larger volume than the fine pores and communicating with the fine pores while opening onto the polishing surface. The large pores suppress the processing resistance during polishing of the notch and reduce chipping at the notch.

[0021] According to the results of the inventors' tests, it is preferable that the fine pores are 46.8 to 57.7% by volume, and the large pores are 0 to 13.8% by volume.

[0022] When a polishing liquid is used, the polishing liquid may be pure water, an oil-based liquid, or a liquid containing an acidic or alkaline chemical.

[0023] The polishing surface may have a third surface that is continuous with the first surface and has a tapered shape that increases in diameter as it approaches the second surface, and a fourth surface that is continuous with the second surface and has a tapered shape that increases in diameter as it approaches the first surface. The third surface and the fourth surface preferably have an interior angle that matches the opening angle of the notch.

[0024] In the polishing method of the present invention, it is preferable that the polishing pad is moved along the first rotation axis in the second step. In this case, the entire notch, including the boundary between the fifth and sixth faces of the notch, can be polished by the ridge of the polishing pad. Therefore, chipping or cracking near the notch in the wafer after notch polishing is less likely or does not occur.

[0025] In the polishing method of the present invention, it is also preferable that the polishing pad is oscillated so that the central axis oscillates around the first rotation axis in the second step. In this case, the edge between the notch and the front or back surface can also be polished effectively. Therefore, chipping or cracking near the notch in the wafer after notch polishing is less likely or does not occur.

[0026] Examples and Comparative Examples Examples 1 to 6 embodying the present invention and Comparative Examples 1 and 2 will be described below.

[0027] First, the following binder resin, abrasive particles, and solvent were prepared: (binder resin) PVDF (polyvinylidene fluoride) (abrasive particles) diamond (average particle size: 5 μm) (solvent) NMP (N-methyl-2-pyrrolidone) (filler) silica particles (average particle size: 200 nm) (pore-forming agent) granulated sugar (average particle size 200 μm)

[0028] The binder resin, abrasive particles, solvent, filler, and pore-forming agent were mixed in the mass percentages shown in Table 1 to form pastes. Each of the resulting pastes was used to obtain a sheet-shaped molded body using a T-die. The solvent was removed from each molded body, and the binder resin was solidified.

[0029]

[0030] Thus, each polishing body was obtained. The outer and inner peripheral portions of each polishing body were cut away around the first rotation axis P to obtain the polishing pads 1 of Examples 1 to 6. As shown in Figures 1 and 2, each polishing pad 1 had an inner diameter φ1 of 152 mm, an outer diameter φ2 of 200 mm, and a thickness t of 4.5 mm. The inner diameter, outer diameter, and thickness can be changed depending on the polishing device described below.

[0031] 1, each polishing pad 1 is formed in an annular shape centered on a first rotation axis P. Each polishing pad 1 has an annular first surface 1a extending in a direction substantially perpendicular to the first rotation axis P, an annular second surface 1b extending in a direction substantially perpendicular to the first rotation axis P and positioned opposite the first surface 1a, and a polishing surface 3 connecting the first surface 1a and the second surface 1b on the outer periphery.

[0032] 2, the polished surface 3 has a third surface 3a that is continuous with the first surface 1a and that tapers from the first rotation axis P toward the second surface 1b, and a fourth surface 3b that is continuous with the second surface 1b and that tapers from the first rotation axis P toward the first surface 1a, as shown in FIG. 2. The third surface 3a and the fourth surface 3b form an interior angle θ1 of 110°±20°. The third surface 3a and the fourth surface 3b also form a ridge line L. The interior angle θ1 is formed to match the opening angle θ2 of a notch 7, which will be described later.

[0033] An SEM photograph of polishing pad 1 of Example 1 at 500x magnification is shown in Figure 3, an SEM photograph at 2000x magnification is shown in Figure 4, and an SEM photograph at 5000x magnification is shown in Figure 5. An SEM photograph of one large pore in polishing pad 1 of Example 1 at 500x magnification is shown in Figure 6, and an SEM photograph of another large pore at 500x magnification is shown in Figure 7.

[0034] As shown in Figures 3 and 4, the polishing pads 1 of Examples 1 to 6, as also shown in Figures 14 and 15, have a matrix 13 and abrasive particles 11. The matrix 13 is made of a binder resin and has a plurality of pores 15a, 15b formed therein. The abrasive particles 11 are held within the matrix 13 or within the pores 15a. Each polishing pad 1 also includes filler 12 held within the matrix 13 or within the pores 15a. As shown in Figures 5 and 6, the pores 15a, 15b of each polishing pad 1 are composed of pores 15a forming a three-dimensional network structure and large pores 15b that are larger in volume than the pores 15a and that are open to the polishing surface 3 and communicate with the pores 15a.

[0035] The physical properties of the polishing pads 1 of Examples 1 to 6 thus obtained were measured in terms of durometer hardness (D), density (g / cm 3 The results are shown in Table 2.

[0036]

[0037] The binder resin content (vol %), abrasive particle content (vol %), filler content (vol %), and pore content (vol %) were also measured. The results are shown in Table 3.

[0038]

[0039] The pore content breakdown, i.e., the volume percent of fine pores and the volume percent of large pores, was also measured. The results are shown in Table 4.

[0040]

[0041] (Test) As shown in Fig. 8, an unpolished wafer 5 made of SiC was prepared. The wafer 5 was disk-shaped with a diameter of 8 inches. The wafer 5 had a central axis Q forming the center of an arc, a front surface 5a extending in a direction substantially perpendicular to the central axis Q, and a back surface 5b located opposite the front surface 5a and extending in a direction substantially perpendicular to the central axis Q. In addition, the wafer 5 had a notch 7 cut out from the front surface 5a to the back surface 5b at one location on its outer periphery, indicating the direction of the crystal axis.

[0042] As shown in FIG. 9 , the notch 7 is formed by a fifth surface 7 a extending from one point on the outer peripheral edge toward the central axis Q and a sixth surface 7 b extending from another point on the outer peripheral edge toward the central axis Q at an opening angle θ2.

[0043] A polishing apparatus shown in FIG. 10 was also prepared. The polishing apparatus was a "FINE SURFACE E-200" manufactured by BBS Kinmei and was equipped with a bracket (not shown) that could rotate the polishing pad 1 around a first rotation axis P. The first rotation axis P was perpendicular to the central axis Q of the wafer 5 held on a drum (not shown). The bracket was capable of pressing the polishing pad 1 against the drum. The polishing apparatus was also capable of moving the polishing pad 1 within a certain range T along the first rotation axis P. This allowed the entire notch 7, including the boundary between the fifth surface 7a and the sixth surface 7b of the notch 7, to be polished by the ridge line L of the polishing pad 1.

[0044] 11 , the wafer 5 is adapted to oscillate vertically at an angle of S° relative to the polishing pad 1 so that the central axis Q oscillates around the first rotation axis P. The oscillation center is the intersection X of an imaginary line extending from the central axis Q toward the center of the notch 7 at the center in the thickness direction of the wafer 5 and the outer circumferential surface of the wafer 5. This allows the notch 7 to be polished at the boundary portion with the front surface 5a of the wafer 5 and the boundary portion with the back surface 5b.

[0045] Then, using the polishing pads 1 of Examples 1 to 6 or the polishing pads 1 of Comparative Examples 1 and 2, the notches 7 of 200 wafers 5 were polished under the following conditions. The polishing pad 1 of Comparative Example 1 was a commercially available hard urethane pad (hardness D: 60), and the polishing pad 1 of Comparative Example 2 was a commercially available nonwoven fabric pad (hardness D: 30). For the polishing pads 1 of Examples 1 to 6, water containing no abrasive particles was used as the polishing liquid. For the polishing pads 1 of Comparative Examples 1 and 2, silica was used as the abrasive particles, and a permanganate-based slurry with a varied abrasive particle concentration was used as the polishing liquid. Rotation speed of polishing pad 1: 600 (rpm) Pressing load of polishing surface 3 against notch 7: 0.8 (kgf)

[0046] A partially enlarged plan view of the notch 7 after polishing is shown in Fig. 12, and a partially enlarged side view is shown in Fig. 13. As shown in Fig. 12 and Fig. 13, the surface of the notch 7 after polishing is smoothed, and chamfers 9 are formed at the tip, the boundary with the front surface 5a, and the boundary with the back surface 5b, making it less likely that chipping or cracking will occur in the vicinity of the notch 7 in the polished wafer 5.

[0047] The polishing time, the presence or absence of unpolished areas, particles, and the polishing solution were evaluated. Unpolished areas were evaluated at the tip of the notch 7 (TOP-VN), the surface 5a of the notch 7 (A-VN), and the back surface 5b of the notch 7 (B-VN).

[0048] Regarding the polishing time and the presence or absence of unpolished areas, if the polishing time was within 90 seconds and there were no unpolished areas, it was rated as ⊚, if the polishing time was within 120 seconds and there were no unpolished areas, it was rated as ◯, if the polishing time was within 180 seconds and there were no unpolished areas, it was rated as △, and if the polishing time was 180 seconds or more and there were unpolished areas, it was rated as ×. However, if pre-processing grinding marks (scratches) existed in the horizontal direction in notch 7 and horizontal grinding marks were confirmed by microscope observation, it was determined that there were unpolished areas.

[0049] Regarding particles, the number of particles was judged by observation under an electron microscope as follows: 0 particles within a 5 μm × 5 μm surface was judged as ⊚; 5 or less particles was judged as ◯; 5 or more but less than 10 particles was judged as △; and 10 or more particles was judged as ×.

[0050] Regarding the polishing liquid, if polishing was possible with an abrasive particle concentration of 0 ppm, it was marked with an ⊚; if polishing was not possible unless the abrasive particle concentration was 1 ppm or more and less than 1000 ppm, it was marked with an ◯; if polishing was not possible unless the abrasive particle concentration was 1000 ppm or more and less than 5000 ppm, it was marked with a △; and if polishing was not possible unless the abrasive particle concentration was 5000 ppm or more and 10000 ppm or less, it was marked with an ×.

[0051] Overall, if any of the polishing time, the presence or absence of unpolished areas, particles, and polishing solution was marked with an × or △, it was marked with an ×, if all were ○ or above and the ◎ was 2 or less, it was marked with an ○, and if all were ○ or above and the ◎ was 3 or above, it was marked with an ◎. The results are shown in Table 5.

[0052]

[0053] From Table 5, the polishing pads 1 of Examples 1 to 4 received an overall rating of ◎, and the polishing pads 1 of Examples 5 and 6 received a rating of ○. According to the inventors' test results, the same effect was obtained when TPU (thermoplastic polyurethane) was used instead of PVDF. In contrast, the polishing pads 1 of Comparative Examples 1 and 2 left some areas unpolished and received poor ratings for particles and polishing liquid. This is presumably due to the following reasons.

[0054] That is, as shown in Figures 14 and 15, the polishing pads 1 of Examples 1 to 6 have pores 15 consisting of fine pores 15a and large pores 15b. The pores 15a have a three-dimensional network structure. The large pores 15b have a larger volume than the pores 15a and are open to the polishing surface 2 while communicating with the pores 15a. The diamond abrasive particles 11 are contained within the pores 15a of the matrix 13 and are fixed to the matrix 13 by point or surface contact. If an excessively large load is concentrated on a certain abrasive particle 11 during polishing, that abrasive particle 11 falls off the matrix 13 and polishes while maintaining local freedom within the pores 15a. At this time, the filler 12 flexibly supports the abrasive particle 11 within the pores 15a, preventing excessive load concentration on the abrasive particle 11. This prevents deep scratches or imperfections in the notch 7 of the wafer 5.

[0055] Furthermore, it is presumed that the polishing pads 1 of Examples 1 to 6 have improved flexibility due to the presence of large pores 15b, and are therefore more likely to deform during processing, polishing while following the notch 7. Thus, in the polishing pads 1 of Examples 1 to 6, the large pores 15b suppress the processing resistance during polishing of the notch 7, reducing chipping at the notch 7.

[0056] In particular, the polishing pads of Examples 1 to 6 have a specific density, durometer hardness (D), and compressive modulus, while using polyvinylidene fluoride or thermoplastic polyurethane as the binder resin and diamond as the polishing grains 11. These characteristics enable shortening of the processing time, while reducing or eliminating chipping and cracking near the notch 7.

[0057] Therefore, it can be seen that the polishing pads 1 of Examples 1 to 6 and the notch polishing methods using them can minimize waste of wafers 5 having notches 7 .

[0058] Furthermore, according to the polishing pads 1 of Examples 1 to 10 and the notch polishing methods using them, it is possible to use a polishing liquid that does not contain abrasive particles or that contains only a small amount of abrasive particles, and since there are only a small number of particles that are abrasive particles remaining on the wafer 5 after polishing, the wafer 5 has excellent cleaning properties after polishing.

[0059] Although the present invention has been described above in accordance with Examples 1 to 6, it goes without saying that the present invention is not limited to the above Examples 1 to 6, and can be appropriately modified and applied within the scope of the invention.

[0060] For example, in Examples 1 to 6, the notch 7 of a wafer 5 made of SiC was polished, but the polishing pad and wafer polishing method of the present invention can also be applied to polishing the notch of a wafer made of semiconductors such as Si, GaN, etc.

[0061] The present invention can be used in semiconductor device manufacturing equipment and the like.

[0062] P...First rotation axis 1a...First surface 1b...Second surface 3...Polishing surface 5...Wafer 7...Notch 1...Polishing pad 15a, 15b...Porosity (15a...Micropores, 15b...Large pores) 13...Base material 11...Abrasive particles 12...Silica particles (filler)

Claims

1. A polishing pad formed in an annular shape centered on a first rotation axis, having an annular first surface extending in a direction substantially perpendicular to the first rotation axis, an annular second surface extending in a direction substantially perpendicular to the first rotation axis and positioned opposite the first surface, and a polishing surface connecting the first surface and the second surface on the outer periphery, wherein the pad is rotated around the first rotation axis while pressing the polishing surface against a notch formed in a disk-shaped wafer and indicating the direction of a crystal axis, thereby polishing the notch, wherein the polishing surface is constituted by an abrasive body including a base material containing a binder resin and having a plurality of pores formed therein, and abrasive particles held within the base material or the pores, wherein the binder resin is polyvinylidene fluoride or thermoplastic polyurethane, the abrasive grains are diamond, and the density is 0.9 to 1.2 g / cm 3 The polishing pad has a durometer hardness (D) of 26 to 47 and a compressive modulus of elasticity of 1645.1 to 3241.7 MPa.

2. The polishing pad according to claim 1, wherein said polishing body comprises silica particles held within said matrix or within said pores.

3. A polishing pad according to claim 1 or 2, wherein the pores consist of fine pores forming a three-dimensional network structure and large pores having a larger volume than the fine pores, opening onto the polishing surface and communicating with the fine pores.

4. The polishing pad according to claim 3, wherein the fine pores are 46.8 to 57.7% by volume, and the large pores are 0 to 13.8% by volume.

5. A polishing apparatus 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 extending in a direction substantially perpendicular to the central axis, a back surface located opposite to the front surface and extending in a direction substantially perpendicular to the central axis, and a notch cut from the front surface to the back surface and indicating the direction of the crystal axis; the polishing pad is formed in an annular shape centered on a first rotation axis; the polishing pad has an annular first surface extending in a direction substantially perpendicular to the first rotation axis, an annular second surface extending in a direction substantially perpendicular to the first rotation axis and located opposite to the first surface, and a polishing surface connecting the first surface and the second surface on the outer periphery; the polishing surface is constituted by an abrasive body including a base material containing a binder resin and having a plurality of pores formed therein, and abrasive particles held within the base material or the pores; The binder resin is polyvinylidene fluoride or thermoplastic polyurethane, the abrasive grains are diamond, and the density is 0.9 to 1.2 g / cm 3 a durometer hardness (D) of 26 to 47 and a compressive modulus of elasticity of 1645.1 to 3241.7 MPa; and in the second step, the first rotation axis is orthogonal to the central axis, and the polishing pad is rotated around the first rotation axis while pressing the polishing surface against the notch, using the polishing liquid that does not contain the abrasive particles.

6. A method for polishing a wafer notch according to claim 5, wherein in the second step, the polishing pad is moved along the first rotation axis.

7. A method for polishing a wafer notch according to claim 5 or 6, wherein in the second step, the polishing pad is oscillated so that the central axis oscillates around the first rotation axis.

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