Polishing pad dressing method, silicon wafer polishing method, silicon wafer manufacturing method, and silicon wafer polishing apparatus

Abstract

To provide a dressing method of a polishing pad which can uniformly dress a polishing pad, even when the surface of a rotary surface plate is curved.SOLUTION: There is provided a dressing method of a polishing pad 100 for pressing a grinding wheel 12 of a pad dresser 1 attached with a grinding wheel 12 against the polishing pad 100 stuck to a polishing surface plate, bringing the grinding wheel 12 in slide contact with the polishing pad 100, and thereby dressing the polishing pad 100, wherein the pad dresser 1 is used which is configured so that a radius R1 of curvature in a radial direction of the polishing surface plate of a dressing surface 12b of the grinding wheel 12 which is brought into slide contact with the polishing pad 100 can be changed.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for dressing a polishing pad, a method for polishing a silicon wafer, a method for manufacturing a silicon wafer, and an apparatus for polishing a silicon wafer. [Background technology]

[0002] In the manufacture of silicon wafers, which are a typical example of substrates for semiconductor devices, a double-sided polishing process in which the front and back surfaces of the silicon wafer are polished, and a single-sided polishing process in which either the front or back surface of the silicon wafer is polished, are generally adopted in order to obtain higher precision in wafer flatness and surface roughness quality.

[0003] In the double-side polishing process, a silicon wafer is held on a carrier plate, and the carrier plate is sandwiched between a pair of rotating platens consisting of an upper platen and a lower platen to which a polishing pad is attached. The rotating platen and the carrier plate are rotated relative to each other while a polishing liquid is supplied, thereby simultaneously polishing the front and back surfaces of the silicon wafer.

[0004] On the other hand, in the single-side polishing process, a silicon wafer is placed on a rotating platen to which a polishing pad is attached, and the silicon wafer is pressed by a polishing head. At the same time, the rotating platen and the polishing head are rotated relative to each other while a polishing liquid is supplied, thereby polishing either the front or back side of the silicon wafer.

[0005] When the double-side polishing process or single-side polishing process is repeated, abrasive grains contained in the polishing liquid and polishing debris adhere to the polishing pad attached to the rotating platen, degrading the performance of the polishing pad and causing problems such as a decrease in the polishing rate and uneven polishing. Therefore, a dressing treatment is periodically performed on the polishing pad to restore its performance.

[0006] For example, Patent Document 1 describes a technology for regenerating a polishing pad by pressing a diamond dresser with diamond particles electrodeposited on its underside against a polishing pad and sliding it against the pad to roughen the polishing pad, and then pressing a brush dresser with a brush on its underside against the polishing pad and sliding it against the pad, thereby effectively removing foreign matter that has accumulated in the recesses, even when the polishing surface of the polishing pad has recesses. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-211355 Summary of the Invention [Problem to be solved by the invention]

[0008] In the technology described in Patent Document 1, the dressing surface of the dresser is flat. When a polishing pad is dressed using such a dresser with a flat dressing surface, the radial pressing force varies at the inner and outer ends of the rotating platen depending on the accuracy of the dresser's installation and the angle at which it is pressed, resulting in variations in the removal amount in the radial direction of the rotating platen. Furthermore, if the surface of the rotating platen has a curved shape, such as a bowl shape or an inverted bowl shape, the edges of the dresser are pressed more strongly against the polishing pad at the inner and outer ends of the rotating platen, similarly resulting in variations in the removal amount in the radial direction of the rotating platen.

[0009] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to propose a polishing pad dressing method that can dress the polishing pad more uniformly even when the surface of the rotating table is curved. [Means for solving the problem]

[0010] [1] A method for dressing a polishing pad, comprising pressing a grinding wheel of a pad dresser having a grinding wheel attached thereto against a polishing pad attached to a polishing table, and sliding the grinding wheel against the polishing pad, A method for dressing a polishing pad, comprising using a pad dresser configured to change the radius of curvature R1 of the dressing surface of the grinding wheel that is in sliding contact with the polishing pad in the radial direction of the polishing table.

[0011] [2] A method for dressing a polishing pad according to [1], wherein the radius of curvature R1 of the dressing surface of the grinding wheel is changed to be smaller than the radius of curvature R2 of the surface of the polishing pad, and then the polishing pad is dressed.

[0012] [3] A method for dressing a polishing pad according to [1] or [2], wherein the grinding wheel has a plurality of dressing surfaces with different radii of curvature, and a pad dresser is used that can change the radius of curvature R2 of the dressing surface that comes into sliding contact with the polishing pad by rotating the grinding wheel.

[0013] [4] A method for dressing a polishing pad according to [1] or [2], wherein the base material of the grinding wheel is made of a flexible alloy, and a pad dresser is used that can change the radius of curvature R1 of the dressing surface by pressing the grinding wheel from the opposite side of the dressing surface.

[0014] [5] The grinding wheel is attached to the pad dresser via a holder, both ends of the base material of the grinding wheel are connected to the holder, and the pad dresser can change the radius of curvature R1 of the dressing surface by pressing a part of the grinding wheel on the opposite side of the dressing surface with a pressing member.

[0033] A method for dressing a polishing pad as described in [4] above.

[0015] [6] The grinding wheel is attached to the pad dresser via a holder having a thermal expansion coefficient different from that of the base material of the grinding wheel, and the pad dresser can change the radius of curvature R1 of the dressing surface by changing the temperature of the holder.

[0033] A method for dressing a polishing pad according to [4].

[0016] [7] A method for polishing a silicon wafer, comprising polishing a silicon wafer using a polishing pad that has been dressed using the method for dressing a polishing pad according to any one of [1] to [6] above.

[0017] [8] A method for producing a silicon wafer, comprising: polishing a silicon wafer obtained by subjecting a single crystal silicon ingot grown by a predetermined method to wafer processing using the silicon wafer polishing method described in [7] above.

[0018] [9] A polishing apparatus comprising a polishing platen, a polishing pad attached to the polishing platen, and a pad dresser equipped with a grinding stone for dressing the polishing pad, 1. A silicon wafer polishing apparatus, comprising: a dressing surface of the grinding wheel that comes into sliding contact with the polishing pad; a radius of curvature R1 in the radial direction of the polishing platen that is variable.

[0019]

[10] The silicon wafer polishing apparatus according to [9], wherein the grinding wheel has a plurality of dressing surfaces with different radii of curvature, and the radius of curvature R1 of the dressing surface that comes into sliding contact with the polishing pad can be changed by rotating the grinding wheel.

[0020]

[11] The silicon wafer polishing apparatus according to

[10] , wherein the base material of the grinding wheel is made of a flexible alloy, and the radius of curvature R1 of the dressing surface can be changed by pressing the grinding wheel from the opposite side of the dressing surface.

[0021]

[12] The polishing apparatus for silicon wafers described in

[11] above, wherein the grinding wheel is attached to the pad dresser via a holder, both ends of the base material of the grinding wheel are connected to the holder, and the radius of curvature R1 of the dressing surface can be changed by pressing a part of the grinding wheel on the opposite side of the dressing surface with a pressing member.

[0022]

[13] The grinding wheel is attached to the pad dresser via a holder having a thermal expansion coefficient different from that of the base material of the grinding wheel, and the polishing apparatus for the polishing pad described in

[11] is configured so that the radius of curvature R1 of the dressing surface can be changed by changing the temperature of the holder. [Effects of the Invention]

[0023] Even if the surface of the rotating platen is curved, the polishing pad can be dressed more uniformly. [Brief explanation of the drawings]

[0024] [Figure 1] 1A and 1B are diagrams illustrating a method for dressing a polishing pad according to the present invention, in which (a) is a perspective view and (b) is a top view. [Figure 2] 3A and 3B are diagrams illustrating the radius of curvature of the dressing surface of the grinding wheel and the radius of curvature of the polishing pad. [Figure 3] FIG. 1 is a diagram showing an example of a pad dresser that can be used in the present invention and is configured so that the radius of curvature of the dressing surface of the grinding wheel can be changed. [Figure 4] FIG. 10 is a diagram showing another example of a pad dresser that can be used in the present invention and is configured so that the radius of curvature of the dressing surface of the grinding wheel can be changed. [Figure 5] FIG. 10 is a diagram showing yet another example of a pad dresser that can be used in the present invention and is configured so that the radius of curvature of the dressing surface of the grinding wheel can be changed. [Figure 6]FIG. 10 is a diagram showing yet another example of a pad dresser that can be used in the present invention and is configured so that the radius of curvature of the dressing surface of the grinding wheel can be changed. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The polishing pad dressing method according to the present invention is a method for dressing a polishing pad by pressing a grinding wheel of a pad dresser with a grinding wheel attached to the polishing pad and sliding the grinding wheel against the polishing pad attached to a polishing table. The pad dresser is characterized by using a pad dresser configured to change the radius of curvature R1 of the dressing surface of the grinding wheel that slides against the polishing pad in the radial direction of the polishing table.

[0026] As described above, when a polishing pad is dressed using a dresser with a flat dressing surface, as in the technology described in Patent Document 1, differences in the radial pressing force occur at the inner and outer ends of the rotating platen depending on the installation accuracy of the dresser and the angle at which pressure is applied, resulting in a problem of variation in the removal amount in the radial direction of the rotating platen. Also, if the surface of the rotating platen has a curved shape, such as a bowl shape or an inverted bowl shape, the edges of the dresser are pressed more strongly against the polishing pad at the inner and outer ends of the rotating platen, similarly resulting in a problem of variation in the removal amount in the radial direction of the rotating platen.

[0027] The present inventors have conducted extensive research into ways to more uniformly dress a polishing pad even when the surface of the rotating platen is curved. As a result, they came up with the idea of ​​using a pad dresser that is configured to change the radius of curvature R1 of the dressing surface of the grinding wheel that comes into sliding contact with the polishing pad in the radial direction of the polishing platen (hereinafter simply referred to as the "radius of curvature of the dressing surface"). They then discovered that by using such a pad dresser, the radius of curvature of the dressing surface can be changed to match the curvature of the rotating platen, thereby making it possible to dress the polishing pad with a constant pressing pressure, which led to the completion of the present invention.

[0028] FIG. 1 illustrates a method for dressing a polishing pad according to the present invention, with (a) being a perspective view and (b) being a top view. FIG. 1 illustrates the case of dressing a polishing pad 100 attached to the surface of a lower surface plate of a double-sided polishing machine. As shown in FIG. 1(a), the pad dresser 1 has an arm 11 and a grinding wheel 12 attached to the arm 11. The grinding wheel 12 is fixed to the end 11a of the arm 11 via a holder 13. The grinding wheel 12 is composed of a substrate 12a and abrasive grains (not shown) adhered to the surface of the substrate 12a. The abrasive grains are adhered to at least the dressing surface 12b of the grinding wheel 12.

[0029] The radius of curvature R1 of the dressing surface 12b of the grinding wheel 12 is configured to be changeable. This allows the polishing pad 100 to be dressed with a constant pressing pressure by changing the radius of curvature R1 of the dressing surface 12b in accordance with the curvature of the rotating surface plate, thereby enabling the polishing pad 100 to be dressed more uniformly. A specific pad dresser 1 capable of changing the radius of curvature R1 will be described in detail later.

[0030] In the present invention, the "dressing surface of the grinding wheel" refers to the surface of the grinding wheel 12 that comes into sliding contact with the polishing pad 100 when dressing the polishing pad 100. In FIG. 1, the dressing surface 12b is the entire lower surface of the grinding wheel 12. Furthermore, the "radius of curvature of the dressing surface" refers to the radius R1 of the arc obtained by fitting an arc to the radial surface profile of the polishing table for the dressing surface 12b of the grinding wheel 12 that comes into sliding contact with the polishing pad 100, as shown in FIG. 2. The surface profile of the dressing surface 12b can be measured using a commercially available non-contact shape measuring instrument or the like. The arc fitting can be performed using the least squares method or the like.

[0031] As shown in FIG. 1(b), the pad dresser 1 configured as described above is moved from one of the inner and outer ends of the lower platen to the other while rotating the lower platen, thereby dressing the entire polishing pad 100.

[0032] In the present invention, it is preferable to change the radius of curvature R1 of the dressing surface 12b of the grinding wheel 12 to be smaller than the radius of curvature R2 of the surface of the polishing pad 100, and then dress the polishing pad 100. By making the radius of curvature R1 of the dressing surface 12b smaller than the radius of curvature R2 of the surface of the polishing pad 100, dressing can be performed with a more constant pressing pressure, and the polishing pad 100 can be dressed more uniformly. The lower limit of the radius of curvature of the dressing surface 12b is preferably 10 mm or more. This ensures a sufficient contact area between the grinding wheel 12 and the polishing pad 100, allowing the entire polishing pad 100 to be dressed uniformly and efficiently.

[0033] The "radius of curvature of the polishing pad" refers to the radius R2 of the arc obtained by fitting an arc to the surface profile of the polishing pad 100 in the radial direction, as shown in FIG. 2, for the surface 100a of the polishing pad 100. Here, the surface profile refers to the profile of the entire surface of the polishing pad 100 from one end (e.g., the inner end) to the other end (e.g., the outer end). The surface profile of the polishing pad 100 can be measured using a commercially available non-contact shape measuring instrument or a dedicated surface profiler. The arc fitting can be performed using the least squares method or the like.

[0034] Figure 3 shows an example of a pad dresser that can be used in the present invention and is configured so that the radius of curvature of the dressing surface of the grinding wheel can be changed. The pad dresser 2 shown in Figure 3(a) includes a grinding wheel 22. The grinding wheel 22 has a substrate 22a and abrasive grains (not shown) fixed to at least the dressing surface of the substrate 22a. The grinding wheel 22 also has four dressing surfaces with different radii of curvature: 22b (radius of curvature: 50.0 mm), 22c (radius of curvature: 100.0 mm), 22d (radius of curvature: 250.0 mm), and 22e (radius of curvature: 500.0 mm).

[0035] As shown in Fig. 3(b), the grinding wheel 22 is connected to the arm unit 21 via a rotating shaft 23 and a cylinder 24, and is configured so that the radius of curvature R1 of the dressing surface can be changed by rotating the grinding wheel 22 in the radial direction of the surface plate around the rotating shaft 23. The grinding wheel 22 and the rotating shaft 23 can be fixed together by, for example, screws as shown in Fig. 3(c).

[0036] For example, SUS with a DLC-coated surface can be used as the base material of the grindstone 22. Furthermore, for example, diamond abrasive grains or ceramic abrasive grains can be used as the abrasive grains.

[0037] In the pad dresser 2 having such a configuration, the dressing surface of the grindstone 22 is appropriately selected to match the surface shape of the polishing platen to which the polishing pad 100 is attached. Then, the cylinder 24 brings the selected dressing surface (dressing surface 22c in FIG. 3) into sliding contact with the rotating polishing pad 100. This allows the polishing pad 100 to be dressed with a constant pressing pressure, allowing the polishing pad 100 to be dressed more uniformly.

[0038] 3 has four dressing surfaces 22b to 22e, it may have two, three, five or more dressing surfaces. The curvature radius R1 of the dressing surfaces 22b to 22e is not limited to the above-mentioned value, and can be set appropriately to match the surface shape of the polishing platen to which the polishing pad 100 is attached.

[0039] As shown in Figures 4 and 5, unlike the pad dresser 2 described above, a pad dresser can also be used in which the base material of the grinding wheel is made of a flexible metal and the radius of curvature R1 of the dressing surface can be changed by pressing the grinding wheel from the opposite side of the dressing surface.

[0040] Fig. 4 shows another example of a pad dresser that can be used in the present invention and is configured so that the radius of curvature of the dressing surface of the grinding wheel can be changed. Note that Fig. 4 shows only the configuration of the pad dresser near the grinding wheel.

[0041] 4 includes an arm portion 31 (not shown) and a grinding wheel 32. The grinding wheel 32 is fixed to a holder 34 by two fixtures 33, and the holder 34 is fixed to an end portion 31a (not shown) of the arm portion 31. The pad dresser 3 also includes a pressing member 35, and is configured so that the radius of curvature R1 of the dressing surface 32b can be changed by pressing a part of the grinding wheel 32 opposite to the dressing surface 32b with the pressing member 35.

[0042] The flexible metal that constitutes the base material 32a of the grinding wheel 32 is not particularly limited as long as it can be bent by the pressing member 35, and SUS, titanium, aluminum, superelastic alloys, etc. can be used.

[0043] 4 can deform the grinding wheel 32 as shown by the dotted line in Fig. 4 and reduce the radius of curvature R1 of the dressing surface 32b by increasing the force with which the pressing member 35 presses the grinding wheel 32. In this way, by changing the radius of curvature R1 of the dressing surface 32b to match the surface shape of the polishing table and bringing the grinding wheel 32 into sliding contact with the rotating polishing pad 100, the polishing pad 100 can be dressed with a constant pressing pressure, thereby more uniformly dressing the polishing pad 100.

[0044] Fig. 5 shows another example of a pad dresser that can be used in the present invention and is configured so that the radius of curvature of the dressing surface of the grinding wheel can be changed. Note that Fig. 5 shows only the configuration of the pad dresser near the grinding wheel.

[0045] 5 includes an arm portion 41 (not shown) and a grindstone 42. The grindstone 42 is attached to an end portion 41a (not shown) of the arm portion 41 via a holder 44 having a thermal expansion coefficient different from that of a substrate 42a. A flow path 44a through which a liquid flows is provided inside the holder 44.

[0046] A liquid W of a predetermined temperature, such as water, is introduced into the flow path 44a of the holder 44 configured in this manner and circulated to change the temperatures of the grinding wheel 42 and the holder 44. This causes the grinding wheel 42 to deform due to the difference in the thermal expansion coefficients of the two, thereby changing the radius of curvature R1 of the dressing surface 42b. In this way, by changing the radius of curvature R1 of the grinding wheel 42 to match the surface shape of the polishing table and bringing the grinding wheel 42 into sliding contact with the rotating polishing pad 100, the polishing pad 100 can be dressed with a constant pressing pressure, allowing the polishing pad 100 to be dressed more uniformly.

[0047] Metals with different thermal expansion coefficients can be used as materials for forming the base material 42a of the grinding wheel 42 and the holder 44. For example, the base material 42a of the grinding wheel 42 can be made of SUS, titanium, aluminum, a low thermal expansion alloy (Invar), or the like. The holder 44 can also be made of SUS, titanium, aluminum, or the like. Specifically, the base material 42a of the grinding wheel 42 can be made of a low thermal expansion alloy (Invar), and the holder 44 can be made of SUS, but is not limited to this.

[0048] When the thermal expansion coefficient of the holder 44 is made larger than that of the base material 42a of the grinding wheel 42, for example, low-temperature water is circulated as the liquid W through the flow passage 44a of the holder 44. This causes the holder 44 to contract, and the radius of curvature R1 of the dressing surface 42b of the grinding wheel 42 can be changed. On the other hand, when the thermal expansion coefficient of the holder 44 is made smaller than that of the base material 42a of the grinding wheel 42, for example, high-temperature water is circulated as the liquid W through the flow passage 44a of the holder 44. This causes the base material 42a of the grinding wheel 42 to expand, and the radius of curvature R1 of the dressing surface 42b of the grinding wheel 42 can be changed.

[0049] Fig. 6 shows yet another example of a pad dresser that can be used in the present invention and is configured so that the radius of curvature of the dressing surface of the grinding wheel can be changed. Note that Fig. 6 shows only the configuration of the pad dresser near the grinding wheel.

[0050] 6 includes an arm portion 51 (not shown) and a plurality of grinding wheels 52. Each grinding wheel 52 is fixed to the lower surface of a cylinder 53, and the upper surface of the cylinder 53 is fixed to a holder 54. The holder 54 is fixed to an end portion 51 a (not shown) of the arm portion 51.

[0051] In the pad dresser 5, the entire lower surfaces of the multiple grinding wheels 52 form a dressing surface, and the radius of curvature R1 of the dressing surface can be changed by changing the degree of extension and contraction of each cylinder 53. The radius of curvature R1 of the dressing surface can be found by fitting the surface profile formed by the lower surfaces of all the grinding wheels 52 with an arc.

[0052] (Silicon wafer polishing method) The method for polishing a silicon wafer according to the present invention is characterized in that a silicon wafer is polished using a polishing pad that has been dressed using the above-described method for dressing a polishing pad according to the present invention.

[0053] As described above, the polishing pad dressing method according to the present invention uses a pad dresser configured to change the radius of curvature R1 of the dressing surface of the grinding wheel that is in sliding contact with the polishing pad in the radial direction of the polishing table, so that the polishing pad can be dressed more uniformly even if the surface of the rotating table is curved. As a result, by polishing a silicon wafer with the dressed polishing pad, the flatness of the silicon wafer can be improved.

[0054] (Silicon wafer manufacturing method) The method for producing a silicon wafer according to the present invention is characterized in that a silicon wafer obtained by subjecting a single crystal silicon ingot grown by a predetermined method to wafer processing is polished using the above-described method for polishing a silicon wafer according to the present invention.

[0055] As described above, the method for polishing silicon wafers according to the present invention can improve the flatness of silicon wafers. Therefore, by polishing silicon wafers obtained by subjecting single crystal silicon ingots grown by a predetermined method such as the Czochralski (CZ) method or the floating zone melting (FZ) method to wafer processing using the method for polishing silicon wafers according to the present invention, silicon wafers with higher flatness can be manufactured.

[0056] (Silicon wafer polishing equipment) The silicon wafer polishing apparatus according to the present invention is a polishing apparatus comprising a polishing platen, a polishing pad attached to the polishing platen, and a pad dresser to which a grinding stone is attached and which dresses the polishing pad. The polishing apparatus is characterized in that the radius of curvature R1 in the radial direction of the polishing platen of the dressing surface of the grinding stone that comes into sliding contact with the polishing pad is configured to be changeable.

[0057] The silicon wafer polishing apparatus according to the present invention is characterized by including a pad dresser that can be used in the polishing pad dressing method according to the present invention. By including the pad dresser in the polishing apparatus, the polishing pad can be dressed with a constant pressing pressure, thereby more uniformly dressing the polishing pad. As a result, by polishing a silicon wafer using the dressed polishing pad, the flatness of the silicon wafer can be improved.

[0058] As shown in Figure 3, the pad dresser can be a pad dresser 2 in which the grinding wheel 22 has multiple dressing surfaces 22b to 22e with different radii of curvature, and the radius of curvature R1 of the dressing surface that comes into sliding contact with the polishing pad 100 can be changed by rotating the grinding wheel 22.

[0059] The pad dresser may also be configured such that the base material of the grinding wheel is made of a flexible alloy, and the radius of curvature R1 of the dressing surface can be changed by pressing the grinding wheel from the opposite side of the dressing surface.

[0060] Specifically, as shown in FIG. 4, the grinding wheel 32 is attached to the pad dresser 3 via a holder 34, and both ends of the base material 32a of the grinding wheel 32 are connected to the holder 34. By pressing a part of the grinding wheel 32 on the opposite side of the dressing surface 32b with a pressing member 35, the pad dresser 3 can be configured to change the radius of curvature R1 of the dressing surface 32b.

[0061] Alternatively, as shown in FIG. 5, the pad dresser 4 may be configured such that the grinding wheel 42 is attached to the pad dresser 4 via a holder 44 having a different thermal expansion coefficient from the base material 42a of the grinding wheel 42, and the radius of curvature R1 of the dressing surface 42b can be changed by changing the temperature of the holder 44.

[0062] Furthermore, as shown in Figure 6, the pad dresser is provided with an arm portion 51 (not shown) and a plurality of grinding wheels 52, each of which is fixed to the underside of a cylinder 53, the upper surface of which is fixed to a holder 54, and by changing the degree of extension and contraction of each cylinder 53, the pad dresser 5 can be made to be capable of changing the radius of curvature R1 of the dressing surface. [Industrial Applicability]

[0063] According to the present invention, even if the surface of the rotating platen is curved, the polishing pad can be dressed more uniformly, which is useful in the semiconductor wafer manufacturing industry. [Explanation of symbols]

[0064] 1,2,3,4,5 Pad Dresser 11, 21, 31, 41, 51 Arm section 11a,21a,31a,41a,51a End 12, 22, 32, 42, 52 Grindstone 12a,22a,32a,42a Base material 12b, 22b, 22c, 22d, 22e, 32b, 42b Dressing surface 13,34,44,54 Holder 23 Rotation axis 24.53 cylinders 33,43 Fixtures 44a Flow path R1,R2 radius of curvature W liquid

Claims

1. A method for dressing a polishing pad, comprising: pressing a grindstone of a pad dresser provided with a grindstone against a polishing pad attached to a polishing platen; and sliding the grindstone against the polishing pad, thereby dressing the polishing pad; A method for dressing a polishing pad, characterized in that the direction of movement of the grinding wheel when sliding the grinding wheel against the polishing pad is the radial direction of the polishing table, and a pad dresser is used that is configured to be able to change the radius of curvature R1 of the dressing surface of the grinding wheel that slides against the polishing pad in the radial direction of the polishing table.

2. 2. A method for dressing a polishing pad as described in claim 1, wherein the radius of curvature R1 of the dressing surface of the grinding wheel is changed to be smaller than the radius of curvature R2 of the polishing table in the radial direction of the surface of the polishing pad, and then the polishing pad is dressed.

3. 3. A method for dressing a polishing pad according to claim 1, wherein the grinding wheel has a plurality of dressing surfaces with different radii of curvature, and a pad dresser is used that can change the radius of curvature R1 of the dressing surface that comes into sliding contact with the polishing pad by rotating the grinding wheel.

4. 3. A method for dressing a polishing pad according to claim 1, wherein the base material of the grinding wheel is made of a flexible alloy, and a pad dresser is used that can change the radius of curvature R1 of the dressing surface by pressing the grinding wheel from the opposite side of the dressing surface.

5. 5. A method for dressing a polishing pad as described in claim 4, wherein the grinding wheel is attached to the pad dresser via a holder, both ends of the base material of the grinding wheel are connected to the holder, and the pad dresser is capable of changing the radius of curvature R1 of the dressing surface by pressing a portion of the grinding wheel on the opposite side of the dressing surface with a pressing member.

6. 3. A method for dressing a polishing pad according to claim 1, wherein the grinding wheel is attached to the pad dresser via a holder having a thermal expansion coefficient different from that of the base material of the grinding wheel, and the pad dresser is capable of changing the radius of curvature R1 of the dressing surface by changing the temperature of the holder.

7. 3. A method for polishing a silicon wafer, comprising polishing a silicon wafer using a polishing pad that has been dressed using the method for dressing a polishing pad according to claim 1.

8. A method for producing a silicon wafer, comprising: polishing a silicon wafer obtained by subjecting a single crystal silicon ingot grown by a predetermined method to wafer processing using the method for polishing a silicon wafer according to claim 7.

9. A polishing apparatus comprising a polishing platen, a polishing pad attached to the polishing platen, and a pad dresser equipped with a grinding stone for dressing the polishing pad, the grinding wheel is configured to move in a radial direction of the polishing platen when the grinding wheel is pressed against the polishing pad and brought into sliding contact with the polishing pad to dress the polishing pad, 1. A silicon wafer polishing apparatus, comprising: a dressing surface of said grinding wheel that comes into sliding contact with said polishing pad; a radius of curvature R1 in the radial direction of said polishing surface plate that is changeable.

10. 10. The silicon wafer polishing apparatus according to claim 9, wherein the grinding wheel has a plurality of dressing surfaces with different radii of curvature, and the radius of curvature R1 of the dressing surface that comes into sliding contact with the polishing pad can be changed by rotating the grinding wheel.

11. 10. The silicon wafer polishing apparatus of claim 9, wherein the base material of the grinding wheel is made of a flexible alloy, and the radius of curvature R1 of the dressing surface can be changed by pressing the grinding wheel from the opposite side of the dressing surface.

12. 12. The silicon wafer polishing apparatus according to claim 11, wherein the grinding wheel is attached to the pad dresser via a holder, both ends of a base material of the grinding wheel are coupled to the holder, and the radius of curvature R1 of the dressing surface can be changed by pressing a part of the grinding wheel on the opposite side of the dressing surface with a pressing member.

13. 10. The silicon wafer polishing apparatus according to claim 9, wherein the grinding wheel is attached to the pad dresser via a holder having a thermal expansion coefficient different from that of a base material of the grinding wheel, and the radius of curvature R1 of the dressing surface can be changed by changing the temperature of the holder.

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