Wafer polishing device, polishing pad, and wafer polishing method

Abstract

Provided is a single-wafer polishing device capable of polishing a surface to be polished of a wafer at high speed and in a desirable manner. A wafer polishing device according to the present invention comprises: a surface plate 7 to which a polishing pad 1 having a polishing surface 1a is fixed and which rotates the polishing surface 1a around a first axis O1; and a carrier 5 to which a single wafer W having a surface Wf to be polished is fixed and which rotates the surface Wf to be polished around a second axis O2 parallel to the first axis O1. The surface Wf to be polished is polished by the polishing surface 1a at a predetermined surface pressure and in the presence of a polishing liquid 11a. The carrier 5 is swingable with respect to the second axis O2 so that the surface Wf to be polished follows the polishing surface 1a. The polishing pad 1 has a recess 10 where the polishing surface 1a is recessed in a conical shape with the first axis O1 as a center axis and comes into contact with the surface Wf to be polished.

Description

Wafer polishing apparatus, polishing pad, and wafer polishing method

[0001] The present invention relates to a wafer polishing apparatus, a polishing pad, and a wafer polishing method.

[0002] Patent Document 1 discloses a wafer polishing apparatus. This wafer polishing apparatus includes a platen and a carrier. A polishing pad having a polishing surface is fixed to the platen, and the polishing surface is rotated about a first axis. A wafer having a surface to be polished is fixed to the carrier, and the carrier rotates the surface to be polished about a second axis parallel to the first axis. This wafer polishing apparatus polishes the surface to be polished with the polishing surface under a predetermined surface pressure and in the presence of a polishing liquid.

[0003] Wafer polishing apparatuses include batch-type apparatuses in which three or four wafers are fixed to one carrier and the polished surface of each wafer is polished by the polishing surface of a polishing pad, and single-wafer-type apparatuses in which a single wafer is fixed to one carrier and the polished surface of that wafer is polished by the polishing surface of a polishing pad. Among single-wafer-type wafer polishing apparatuses, there is one in which the carrier can swing about a second axis so that the polished surface conforms to the polishing surface. In the single-wafer-type wafer polishing apparatus disclosed in Patent Document 1, the carrier can swing about a second axis so that the polished surface conforms to the polishing surface.

[0004] Compared with batch-type polishing machines, single-wafer wafer polishing machines are increasingly being used when polishing the polished surface of large-diameter wafers. Currently, for example, silicon carbide (SiC) wafers are mainly 6-inch in size, but there is a trend toward 8-inch wafers, and it is expected that single-wafer wafer polishing machines will attract attention in the future. In single-wafer wafer polishing machines, if the carrier can oscillate about the second axis, it is said that the flatness of the wafer can be improved.

[0005] International Publication No. 2004 / 28743

[0006] However, in the single-wafer type wafer polishing apparatus described above, the number of wafers processed in one polishing session is inevitably smaller than in the batch type wafer polishing apparatus, so it is not enough to simply be able to polish the surface to be polished well; higher speed polishing is also required.

[0007] The present invention has been made in consideration of the above-described conventional situation, and has as its object to provide a single-wafer wafer polishing apparatus capable of polishing the polished surface of a wafer quickly and effectively. Another object of the present invention is to provide a polishing pad that, when used in such a single-wafer wafer polishing apparatus, can polish the polished surface of a wafer quickly and effectively. A further object of the present invention is to provide a wafer polishing method that can polish the polished surface of a wafer quickly and effectively in such a single-wafer wafer polishing apparatus.

[0008] The wafer polishing apparatus of the present invention comprises a base plate on which a polishing pad having a polishing surface is fixed and which rotates the polishing surface around a first axis, and a carrier on which a single wafer having a surface to be polished is fixed and which rotates the surface to be polished around a second axis parallel to the first axis, and which polishes the surface to be polished with the polishing surface under a predetermined surface pressure and in the presence of a polishing liquid, characterized in that the carrier is oscillating about the second axis so that the surface to be polished conforms to the polishing surface, and the polishing pad has a recess in which the polishing surface is conically recessed with the first axis as its central axis and abuts the surface to be polished.

[0009] Furthermore, the polishing pad of the present invention is a polishing pad used for polishing wafers in a wafer polishing apparatus, wherein the wafer polishing apparatus comprises a base plate to which the polishing pad having a polishing surface is fixed and which rotates the polishing surface around a first axis, and a carrier to which a single wafer having a surface to be polished is fixed and which rotates the surface to be polished around a second axis parallel to the first axis, and polishes the surface to be polished with the polishing surface under a predetermined surface pressure and in the presence of a polishing liquid, the carrier is capable of swinging about the second axis so that the surface to be polished conforms to the polishing surface, and the polishing surface has a recess that is conically recessed with the first axis as its central axis and abuts the surface to be polished.

[0010] Furthermore, the present invention provides a wafer polishing method comprising: a first preparation step of preparing a wafer polishing apparatus having a platen having a pad fixing surface and rotating the pad fixing surface around a first axis, and a carrier having a wafer fixing surface and rotating the wafer fixing surface around a second axis parallel to the first axis; a second preparation step of preparing a flat polishing pad and fixing the polishing pad to the pad fixing surface; a third preparation step of preparing a wafer having a surface to be polished and fixing a single wafer to the wafer fixing surface; a dressing step of forming a polishing surface on the polishing pad fixed to the pad fixing surface; and a polishing step of polishing the surface to be polished with the polishing surface under a predetermined surface pressure and in the presence of a polishing liquid, wherein the dressing step forms a recess in the polishing surface that is conically recessed about the first axis and comes into contact with the surface to be polished; and the polishing step oscillates the carrier about the second axis so that the surface to be polished conforms to the polishing surface.

[0011] According to the inventors' test results, in a single-wafer wafer polishing machine in which the carrier can oscillate about the second axis and the wafer surface conforms to the polishing surface of the polishing pad, using a polishing pad with a conical recess centered on the first axis results in a flat and large wafer removal rate even when polishing at high speed. This improves polishing efficiency in proportion to the rotation speed and pressure (Preston's Law). Furthermore, no scratches are produced on the polished surface after polishing, and the surface roughness is minimal.

[0012] On the other hand, even in a single-wafer wafer polishing apparatus in which the carrier can oscillate about the second axis and the polished surface of the wafer conforms to the polishing surface of the polishing pad, if a polishing pad with a flat polishing surface or a polishing pad with a conical protrusion centered on the first axis is used, the wafer removal rate becomes mountain-shaped and is smaller than that described above when polished at high speed. It is believed that this is because rotating the surface plate or carrier at high speed causes the surface plate to thermally expand into a conical shape centered on the first axis, or the tape securing the polishing pad to the surface plate peels off, causing a conical rise centered on the first axis. Even in these cases, no scratches are produced on the polished surface after polishing, and the surface roughness is small.

[0013] The surface plate has a pad fixing surface on which a polishing pad is fixed. Before the polishing process, the pad fixing surface extends in a direction perpendicular to the first axis. The inventors have confirmed the effects of the present invention in a wafer polishing apparatus having this pad fixing surface.

[0014] The recess may have a straight generatrix or may have a center that curves and recesses away from the polished surface, but it is preferable that the center of the generatrix protrudes while curving toward the polished surface. If the center of the generatrix protrudes while curving toward the polished surface, the removal amount of the polished surface of the wafer after polishing is greater.

[0015] The polishing pad is preferably made of a resin matrix, has a base material with multiple pores formed therein, and abrasive particles held within the base material or the pores. This polishing pad is an abrasive-containing polishing pad, also known as an LHA (Loosely Held Abrasive) pad. In this case, a polishing liquid containing no abrasive particles can be used, so even if the carrier uses a negative pressure fixing means, problems with the fixing means or the backside of the wafer are unlikely to occur. This allows for quick wafer removal and improves wafer polishing efficiency. Furthermore, when a polishing liquid containing abrasive particles is used, rotating the platen or carrier at high speed causes the abrasive particles to fly outward due to centrifugal force, making it difficult for the abrasive particles to reach the processing point. However, by using such an LHA pad, such problems are unlikely to occur due to the use of a polishing liquid containing no abrasive particles.

[0016] The wafer polishing apparatus of the present invention can polish the surface of a wafer quickly and effectively. Furthermore, the polishing pad of the present invention, when used in such a single-wafer-processing wafer polishing apparatus, can polish the surface of a wafer quickly and effectively. Furthermore, the wafer polishing method of the present invention can polish the surface of a wafer quickly and effectively in such a single-wafer-processing wafer polishing apparatus.

[0017] FIG. 1 is a schematic cross-sectional view of a wafer polishing apparatus according to an embodiment. FIG. 2 is a graph showing the relationship between the radial length and thickness dimension of a polishing pad for a wafer polishing apparatus and wafer polishing method according to an embodiment. FIG. 3 is a graph showing the relationship between the diameter length of a wafer after polishing and the removal allowance under first high-speed conditions for a wafer polishing apparatus and wafer polishing method according to an embodiment. FIG. 4 is a graph showing the relationship between the diameter length of a wafer after polishing and the removal allowance under second high-speed conditions for a wafer polishing apparatus and wafer polishing method according to an embodiment. FIG. 5 is a graph showing the surface roughness of a wafer after polishing for a wafer polishing apparatus and wafer polishing method according to an embodiment. FIG. 6 is a schematic cross-sectional view of a wafer polishing apparatus according to Comparative Example 1. FIG. 7 is a graph showing the relationship between the radial length and thickness dimension of a polishing pad for a wafer polishing apparatus and wafer polishing method according to Comparative Example 1. FIG. 8 is a graph showing the relationship between the diameter length of a wafer after polishing and the removal allowance under first high-speed conditions for a wafer polishing apparatus and wafer polishing method according to Comparative Example 1. Fig. 9 is a graph showing the relationship between the diameter length of a wafer after polishing and the removal allowance under second high-speed conditions for the wafer polishing apparatus and wafer polishing method of Comparative Example 1. Fig. 10 is a schematic cross-sectional view of a wafer polishing apparatus of Comparative Example 2. Fig. 11 is a graph showing the relationship between the radial length and thickness dimension of a polishing pad for the wafer polishing apparatus and wafer polishing method of Comparative Example 2. Fig. 12 is a graph showing the relationship between the diameter length of a wafer after polishing and the removal allowance under first high-speed conditions for the wafer polishing apparatus and wafer polishing method of Comparative Example 2. Fig. 13 is a graph showing the relationship between the diameter length of a wafer after polishing and the removal allowance under second high-speed conditions for the wafer polishing apparatus and wafer polishing method of Comparative Example 2.

[0018] Hereinafter, examples embodying the present invention will be described together with comparative examples 1 and 2 with reference to the drawings.

[0019] (Example) <First Preparation Step> First, a single-wafer wafer polishing apparatus for the example was prepared. This wafer polishing apparatus was a modified version of the LAPMASTER LAPOLISH15. As shown in Figure 1, this wafer polishing apparatus includes a surface plate 7, a single carrier 5, a drive unit 9, and a polishing liquid supply unit 11.

[0020] The surface plate 7 is in the shape of a horizontal disk that contains the carrier 5 within its own radius. The diameter of the surface plate 7 is 380 inches. A first rotation shaft 7a is vertically provided on the underside of the surface plate 7. The first rotation shaft 7a is driven to rotate at a predetermined speed around a first axis O1. The upper surface of the surface plate 7 serves as a pad fixing surface 7b. Before the polishing process, the pad fixing surface 7b extends in a direction perpendicular to the first axis O1.

[0021] The carrier 5 has a horizontal disk shape. A wafer fixing surface 5a is recessed in the lower surface of the carrier 5, and the wafer W is fixed to the wafer fixing surface 5a by negative pressure. A second rotation shaft 5b is vertically provided on the upper surface of the carrier 5. The second rotation shaft 5b is driven to rotate at a predetermined speed around a second axis O2. The carrier 5 is configured to be swingable about the second axis O2 by a constant velocity joint or the like.

[0022] The drive unit 9 includes a main drive unit 9a, a sub-drive unit 9b, and a pressure unit 9c. The main drive unit 9a drives the first rotating shaft 7a to rotate around the first axis O1 at a predetermined speed. The sub-drive unit 9b drives the second rotating shaft 5b to rotate around the second axis O2 at a predetermined speed. The pressure unit 9c presses the second rotating shaft 5b and the sub-drive unit 9b against the surface plate 7 with a predetermined load.

[0023] The polishing liquid supply device 11 is provided above the surface plate 7. The polishing liquid supply device 11 provides a polishing liquid 11a between each wafer W and the polishing pad 1. The polishing liquid is a potassium permanganate-based aqueous solution and does not contain abrasive particles.

[0024] <Second Preparation Step> A flat polishing pad called an LHA pad was prepared. This polishing pad was made of a base resin and had a base material with multiple pores formed therein, and abrasive particles held in the base material or the pores. The base resin was polyethersulfone, and the abrasive particles were silica. The volume percentages of the base material, pores, and abrasive particles were 28 volume %, 46 volume %, and 26 volume %, respectively. The average particle size of the abrasive particles was 200 nm.

[0025] <Third Preparation Step> A 4-inch wafer W made of SiC was prepared, and a single wafer W was fixed to the wafer fixing surface 5a. At this time, the Si surface was used as the surface to be polished Wf.

[0026] <Dressing Step> The polishing pad was fixed to the pad fixing surface 7b of the surface plate 7 with tape (not shown). Then, a dressing tool (not shown) was prepared and a recess 10 was formed in the polishing pad with the dressing tool. FIG. 1 shows a polishing pad 1 with a recess 10 formed therein. The recess 10 consists of a flat bottom surface 10a with the first axis O1 as its central axis and a conical surface 10b that is continuous with the bottom surface 10a and is recessed in a conical shape with the first axis O1 as its central axis. The polishing surface 1a of the polishing pad 1 consists of the bottom surface 10a and the conical surface 10b.

[0027] The polished surface Wf of the wafer W is disposed so as to abut on the conical surface 10b, but not on the bottom surface 10a. The relationship between the radial length (mm) and thickness (μm) of the polishing pad 1 is shown in Figure 2. As shown in Figure 2, the generatrix L of the conical surface 10b is an approximately straight line.

[0028] <Polishing Step> The surface to be polished Wf was polished by the polishing surface 1a under the following first and second high-speed conditions. During this process, the carrier 5 was oscillated about the second axis O2 so that the surface to be polished Wf followed the conical surface 10b of the polishing surface 1a.

[0029] First high-speed condition: The surface to be polished Wf was polished by the polishing surface 1a at a surface pressure of 40 kPa and a polishing solution of pH 7 at a rate of 10 mL / min, with the rotation speed of the platen 7 and the carrier 5 set to 60 rpm. The polishing time was 1 hour.

[0030] Second high-speed conditions: The surface to be polished Wf was polished by the polishing surface 1a at a surface pressure of 70 kPa and a rotation speed of the platen 7 and the carrier 5 of 120 rpm while the polishing liquid was present at a rate of 10 mL / min. The polishing time was 1 hour.

[0031] The relationship between the diameter length (mm) of the wafer W after polishing under the first high-speed conditions and the removal rate (μm) of the polished surface Wf is shown in Figure 3. The temperature of the platen 7 during polishing under the first high-speed conditions was 36.3°C. The polishing rate under the first high-speed conditions was 1098 nm / hour. A Keyence SI-T1000V spectroscopic interferometer was used to measure the thickness.

[0032] The relationship between the diameter (mm) of the wafer W after polishing under the second high-speed conditions and the removal rate (μm) of the polished surface Wf is shown in Figure 4. The temperature of the platen 7 during polishing under the second high-speed conditions was 54.0°C. The polishing rate under the second high-speed conditions was 8139 nm / hour.

[0033] In addition, a polishing pad 1 having a circular groove formed concentric with the first axis O1 was used, and the polished surface Wf was polished by the polishing surface 1a in the presence of a polishing solution of pH 3. Other conditions were the same as those for the second high-speed conditions. After polishing, the presence or absence of scratches and the surface roughness Ra (nm) were measured at nine locations on the polished surface Wf of the wafer W. The presence or absence of scratches was measured using an OPTELICS HYBRID spectral interferometric displacement measuring instrument manufactured by Lasertec. The surface roughness was measured using a Hitachi High-Tech VS1330 white light interference microscope. The results, along with the average values, are shown in Figure 5.

[0034] 3 and 4, the results of the temperature of the platen 7 during polishing and the polishing rate show that the wafer W removal stock is flat and large even when polished at high speeds with the wafer polishing apparatus of the embodiment. It can also be seen that no scratches are generated on the polished surface Wf after polishing, and the surface roughness is small as shown in FIG. 5. This is because the embodiment uses a polishing pad 1 whose polishing surface 1a has a conical recess 10 with the first axis O1 as its central axis.

[0035] Comparative Example 1 Similar to Example 1, the first to third preparation steps were performed. Then, in the dressing step, a flat polishing surface 2a was formed on the polishing pad using a dressing tool. FIG. 6 shows the polishing pad 2 on which the polishing surface 2a was formed. FIG. 7 shows the relationship between the radial length (mm) and the thickness dimension (μm) of the polishing pad 2. As shown in FIG. 7, the generatrix L of the polishing surface 2a is also approximately straight.

[0036] In the polishing step, the surface to be polished Wf was polished by the polishing surface 2a under the first and second high-speed conditions.

[0037] The relationship between the diameter (mm) of the wafer W after polishing under the first high-speed conditions and the removal rate (μm) of the polished surface Wf is shown in Figure 8. The temperature of the platen 7 during polishing under the first high-speed conditions was 36.8°C. The polishing rate under the first high-speed conditions was 1644 nm / hour.

[0038] The relationship between the diameter (mm) of the wafer W after polishing under the second high-speed conditions and the removal rate (μm) of the polished surface Wf is shown in Figure 9. The temperature of the platen 7 during polishing under the second high-speed conditions was 51.0°C. The polishing rate under the second high-speed conditions was 7007 nm / hour.

[0039] 8 and 9, which show the temperature of the platen 7 during polishing and the polishing rate, the wafer polishing apparatus of Comparative Example 1 polishes at high speed, resulting in a mountain-shaped removal stock of the wafer W, which is smaller than that of the Examples. This is because a polishing pad 2 with a flat polishing surface 2a is used. Note that in Comparative Example 1, no scratches were observed on the polished surface Wf after polishing, and the surface roughness was small. (Comparative Example 2) Similar to Example 1 and Comparative Example 1, the first to third preparation steps were performed. Then, in the dressing step, a protrusion 20 was formed on the polishing pad using a dressing tool. FIG. 10 shows a polishing pad 3 with a protrusion 20 formed thereon. The protrusion 20 consists of a flat upper surface 20a with the first axis O1 as its central axis and a conical surface 20b that is continuous with the upper surface 20a and protrudes in a conical shape with the first axis O1 as its central axis. The polishing surface 3a of the polishing pad 3 consists of the upper surface 20a and the conical surface 20b.

[0040] 11 shows the relationship between the radial length (mm) and the thickness (μm) of the polishing pad 3. As shown in Fig. 11, the generatrix L of the polishing surface 3a is also substantially straight.

[0041] In the polishing step, the surface to be polished Wf was polished by the polishing surface 3a under the first and second high-speed conditions.

[0042] 12 shows the relationship between the diameter (mm) of the wafer W after polishing under the first high-speed conditions and the removal rate (μm) of the polished surface Wf. The temperature of the platen 7 during polishing under the first high-speed conditions was 36.1° C. The polishing rate under the first high-speed conditions was 1308 nm / hour.

[0043] 13 shows the relationship between the diameter (mm) of the wafer W after polishing under the second high-speed conditions and the removal rate (μm) of the polished surface Wf. The temperature of the platen 7 during polishing under the second high-speed conditions was 59.0° C. The polishing rate under the second high-speed conditions was 7460 nm / hour.

[0044] 12 and 13, which show the temperature of the platen 7 during polishing and the polishing rate, the wafer polishing apparatus of Comparative Example 2 also polishes at high speed, resulting in a mountain-shaped removal amount for the wafer W, which is smaller than that of the Example. This is because the polishing pad 3 used has a polishing surface 3a with a conical protrusion 20 whose central axis is the first axis O1. Also in Comparative Example 2, no scratches were generated on the polished surface Wf after polishing, and the surface roughness was small.

[0045] Therefore, the wafer polishing apparatus of the embodiment can quickly and effectively polish the polished surface Wf of the wafer W. Furthermore, the wafer polishing method of the embodiment can quickly and effectively polish the polished surface Wf of the wafer W in such a single-wafer type wafer polishing apparatus.

[0046] In the above embodiment, recesses 10 are formed in the polishing surface of the polishing pad in the dressing process, but it is also possible to manufacture a polishing pad 1 with recesses 10 formed in advance and attach the polishing pad to the pad fixing surface 7b of the surface plate 7. In this case, when the polishing pad 1 is used in the single-wafer type wafer polishing apparatus described above, it is possible to polish the polished surface Wf of the wafer W quickly and effectively.

[0047] Furthermore, because the wafer polishing apparatus of the present embodiment employs an abrasive-containing polishing pad, also known as an LHA pad, it is possible to employ a polishing liquid 11a that does not contain abrasive particles. Therefore, even if the carrier 5 employs a fixing means that uses negative pressure, problems are unlikely to occur with the fixing means or the backside of the wafer W. This allows for quick detachment of the wafer W, improving the polishing efficiency of the wafer W. Furthermore, the frequency of maintenance, such as part replacement, of the wafer polishing apparatus is reduced.

[0048] The inventors conducted various studies to determine the angle θ at which the recess 10 is recessed from a plane parallel to the pad fixing surface 7b and the preferred depth from the parallel surface to the bottom surface 10a in the actual wafer polishing apparatus of the embodiment shown in Figure 1.

[0049] As a result, in an actual machine with a surface plate 7 having a diameter of 380 inches, it was preferable that the angle θ be 0.009 to 0.015° and the depth from the parallel surface to the bottom surface 10a be 40±10 μm. On the other hand, in an actual machine with a surface plate 7 having a diameter of 610 inches, it was preferable that the angle θ be 0.009 to 0.013° and the depth from the parallel surface to the bottom surface 10a be 60±10 μm. From these results, it is inferred that, in commercially available actual machines, a polishing pad 1 having a polishing surface 1a with a recess 10 recessed at an angle θ of 0.01 to 0.015 is preferable.

[0050] Although the present invention has been described above with reference to the examples, it goes without saying that the present invention is not limited to the above examples and can be modified and applied as appropriate within the scope of the invention.

[0051] For example, although the wafer polishing apparatus in FIG. 1 has a single carrier 5, a wafer polishing apparatus to which the present invention can be applied may have a plurality of carriers 5 facing the conical surface 10b.

[0052] The present invention can be used in semiconductor device manufacturing equipment.

[0053] 1a... Polishing surface 1... Polishing pad O1... First axis 7... Surface plate Wf... Polished surface W... Wafer O2... Second axis 5... Carrier 11a... Polishing liquid 10... Recess 7b... Pad fixing surface 5a... Wafer fixing surface

Claims

1. A wafer polishing apparatus comprising: a platen on which a polishing pad having a polishing surface is fixed and which rotates the polishing surface around a first axis; and a carrier on which a single wafer having a surface to be polished is fixed and which rotates the surface to be polished around a second axis parallel to the first axis, wherein the polishing surface is polished by the polishing surface under a predetermined surface pressure and in the presence of a polishing liquid; wherein the carrier is oscillating about the second axis so that the surface to be polished conforms to the polishing surface; and the polishing pad has a recess in the polishing surface that is conically recessed with the first axis as its central axis and comes into contact with the surface to be polished.

2. A polishing pad used for polishing wafers in a wafer polishing apparatus, wherein the wafer polishing apparatus comprises a base on which the polishing pad having a polishing surface is fixed and which rotates the polishing surface around a first axis, and a carrier on which a single wafer having a surface to be polished is fixed and which rotates the surface to be polished around a second axis parallel to the first axis, and wherein the surface to be polished is polished by the polishing surface under a predetermined surface pressure and in the presence of a polishing liquid, the carrier is capable of swinging about the second axis so that the surface to be polished follows the polishing surface, and the polishing surface has a recess that is conically recessed with the first axis as its central axis and abuts the surface to be polished.

3. A wafer polishing method comprising: a first preparation step of preparing a wafer polishing apparatus having a platen having a pad fixing surface and rotating the pad fixing surface about a first axis, and a carrier having a wafer fixing surface and rotating the wafer fixing surface about a second axis parallel to the first axis; a second preparation step of preparing a flat polishing pad and fixing the polishing pad to the pad fixing surface; a third preparation step of preparing a wafer having a surface to be polished and fixing a single wafer to the wafer fixing surface; a dressing step of forming a polishing surface on the polishing pad fixed to the pad fixing surface; and a polishing step of polishing the surface to be polished with the polishing surface under a predetermined surface pressure and in the presence of a polishing liquid, wherein the dressing step forms a recess in the polishing surface that is conically recessed about the first axis and abuts against the surface to be polished; and the polishing step oscillates the carrier about the second axis so that the surface to be polished conforms to the polishing surface.

4. A wafer polishing method according to claim 3, wherein the surface plate has a pad fixing surface to which the polishing pad is fixed, and the pad fixing surface before the polishing step extends in a direction perpendicular to the first axis.

5. A wafer polishing method according to claim 3 or 4, wherein the polishing pad is made of a base resin and has a base material with a plurality of pores formed therein, and abrasive particles held in the base material or the pores.

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