METHOD FOR DRESSING POLISHING PAD, METHOD FOR POLISHING SILICON WAFER, METHOD FOR PRODUCING SILICON WAFER, AND DEVICE FOR POLISHING SILICON WAFER

Abstract

A method for dressing a polishing pad that enables more even dressing of the polishing pad even when the surface of the rotating plate is curved. This method for dressing a polishing pad performs dressing of the polishing pad by pressing a grindstone of a pad dresser having the grindstone attached thereto against the polishing pad attached to a polishing plate and sliding the grindstone thereon, and uses a pad dresser which is configured to allow a radius of curvature, in the radial direction of the polishing plate, of a dressing surface of the grindstone that slides on the polishing pad to be changed.

Claims

1. A method for dressing a polishing pad performing dressing of the polishing pad by pressing a grindstone of a pad dresser having the grindstone attached thereto against the polishing pad attached to a polishing plate and sliding the grindstone thereon, wherein using a pad dresser which is configured to allow a radius of curvature R1, in the radial direction of the polishing plate, of a dressing surface of the grindstone that slides on the polishing pad is to be changed.

2. The method for dressing a polishing pad as claimed in claim 1, wherein changing the radius of curvature R1 of the dressing surface of the grindstone to be smaller than a radius of curvature R2 of a surface of the polishing pad, and then performing dressing of the polishing pad.

3. The method for dressing a polishing pad as claimed in claim 1, wherein using a pad dresser in which the grindstone has a plurality of dressing surfaces with different radius of curvatures, and the radius of curvature R2 of the dressing surface that slides on the polishing pad can be changed by rotating the grindstone.

4. The method for dressing a polishing pad as claimed in claim 1, wherein using a pad dresser in which a base material of the grindstone is made of an alloy capable of flexing, and the radius of curvature R1 of the dressing surface can be changed by pressing the grindstone from an opposite side of the dressing surface.

5. The method for dressing a polishing pad as claimed in claim 4, wherein using a pad dresser in which the grindstone is attached to the pad dresser via a retainer, two ends of the base material of the grindstone are coupled to the retainer, and the radius of curvature R1 of the dressing surface can be changed by pressing a portion of the grindstone on an opposite side of the dressing surface with a pressing member.

6. The method for dressing a polishing pad as claimed in claim 4, wherein using a pad dresser in which the grindstone is attached to the pad dresser via a retainer that has a different coefficient of thermal expansion than the base material of the grindstone, and the radius of curvature R1 of the dressing surface can be changed by changing temperature of the retainer.

7. A method for polishing a silicon wafer, wherein 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, wherein comprising polishing a silicon wafer obtained by performing wafer processing treatment on a single crystal silicon ingot grown by a predetermined method, using the method for polishing a silicon wafer according to claim 7.

9. A device for polishing a silicon wafer comprising a polishing plate; a polishing pad attached to the polishing plate; and a pad dresser having a grindstone attached thereto, and dresses the polishing pad, wherein the device is configured to allow a radius of curvature R1, in the radial direction of the polishing plate, of a dressing surface of the grindstone that slides on the polishing pad to be changed.

10. A device for polishing a silicon wafer as claimed in claim 9, wherein the grindstone has a plurality of dressing surfaces with different radius of curvatures, so that the device is configured to allow the radius of curvature R1 of the dressing surface that slides on the polishing pad to be changed by rotating the grindstone.

11. A device for polishing silicon wafer as claimed in claim 10, wherein a base material of the grindstone is made of an alloy capable of flexing, so that the device is configured to allow the radius of curvature R1 of the dressing surface to be changed by pressing the grindstone from an opposite side of the dressing surface.

12. A device for polishing silicon wafer as claimed in claim 11, wherein the grindstone is attached to the pad dresser via a retainer and two ends of the base material of the grindstone are coupled to the retainer, so that the device is configured to allow the radius of curvature R1 of the dressing surface to be changed by pressing a portion of the grindstone on an opposite side of the dressing surface with a pressing member.

13. A device for polishing a silicon wafer as claimed in claim 11, wherein the grindstone is attached to the pad dresser via a retainer that has a different coefficient of thermal expansion than the base material of the grindstone, so that the device is configured to allow the radius of curvature R1 of the dressing surface to be changed by changing temperature of the retainer.

14. The method for dressing a polishing pad as claimed in claim 2, wherein using a pad dresser in which the grindstone has a plurality of dressing surfaces with different radius of curvatures, and the radius of curvature R2 of the dressing surface that slides on the polishing pad can be changed by rotating the grindstone.

15. The method for dressing a polishing pad as claimed in claim 2, wherein using a pad dresser in which a base material of the grindstone is made of an alloy capable of flexing, and the radius of curvature R1 of the dressing surface can be changed by pressing the grindstone from an opposite side of the dressing surface.

16. The method for dressing a polishing pad as claimed in claim 14, wherein using a pad dresser in which the grindstone is attached to the pad dresser via a retainer, two ends of the base material of the grindstone are coupled to the retainer, and the radius of curvature R1 of the dressing surface can be changed by pressing a portion of the grindstone on an opposite side of the dressing surface with a pressing member.

17. The method for dressing a polishing pad as claimed in claim 15, wherein using a pad dresser in which the grindstone is attached to the pad dresser via a retainer that has a different coefficient of thermal expansion than the base material of the grindstone, and the radius of curvature R1 of the dressing surface can be changed by changing temperature of the retainer.

18. A method for polishing a silicon wafer, wherein comprising polishing a silicon wafer using a polishing pad that has been dressed using the method for dressing a polishing pad according to claim 2.

19. A method for producing a silicon wafer, wherein comprising polishing a silicon wafer obtained by performing wafer processing treatment on a single crystal silicon ingot grown by a predetermined method, using the method for polishing a silicon wafer according to claim 18.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In the accompanying drawings:

[0027] FIG. 1A is a perspective view for explaining a method for dressing a polishing pad according to the present disclosure;

[0028] FIG. 1B is a top view for explaining a method for dressing a polishing pad according to the present disclosure;

[0029] FIG. 2 is a drawing for explaining the radius of curvature of a dressing surface of a grindstone and the radius of curvature of a polishing pad;

[0030] FIG. 3 illustrates an example of a pad dresser that can be used in the present disclosure, configured to allow the radius of curvature of the dressing surface of the grindstone to be changed;

[0031] FIG. 4 illustrates another example of a pad dresser that can be used in the present disclosure, configured to allow the radius of curvature of the dressing surface of the grindstone to be changed;

[0032] FIG. 5 illustrates yet another example of a pad dresser that can be used in the present disclosure, configured to allow the radius of curvature of the dressing surface of the grindstone to be changed; and

[0033] FIG. 6 illustrates still another example of a pad dresser that can be used in the present disclosure, configured to allow the radius of curvature of the dressing surface of the grindstone to be changed.

DETAILED DESCRIPTION

[0034] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. The method for dressing a polishing pad according to this disclosure is a method for dressing a polishing pad performing dressing of the polishing pad by pressing a grindstone of a pad dresser having the grindstone attached thereto against the polishing pad attached to a polishing plate and sliding the grindstone thereon. Here, this method is characterized in using a pad dresser which is configured to allow a radius of curvature R1, in the radial direction of the polishing plate, of a dressing surface of the grindstone that slides on the polishing pad to be changed.

[0035] As mentioned above, when dressing a polishing pad using a dresser with a flat dressing surface as in the art described in PTL 1, the accuracy of the dresser installation and the angle at which the dresser is pressurized cause differences in pressing force, at the inner and outer edges of the rotating plate, in the radial direction thereof, resulting in variation in the removal allowance in the radial direction of the rotating plate. Also, when the surface of the rotating plate is curved like a bowl or inverted bowl, the edge of the dresser is pressed more strongly against the polishing pad at the inner and outer edges of the rotating plate, which also causes variations in the removal allowance in the radial direction of the rotating plate.

[0036] We have thoroughly studied ways to dress a polishing pad more evenly when the surface of the rotating plate is curved. As a result, we conceived the idea of using a pad dresser which is configured to allow the radius of curvature, in the radial direction of the polishing plate, of the dressing surface of the grindstone that slides on the polishing pad (hereinafter, simply referred to as radius of curvature of dressing surface) R1 to be changed. We then found that by using such a pad dresser, it is possible to dress a polishing pad with a constant pressing pressure by changing the radius of curvature of the dressing surface to match the curvature of the rotating plate.

[0037] FIGS. 1A and 1B are respectively a perspective view and a top view of a drawing for explaining a method for dressing a polishing pad according to the present disclosure. FIG. 1 illustrates the case of dressing a polishing pad 100 attached to the surface of a lower polishing plate of a double-side polishing device. As illustrated in FIG. 1A, a pad dresser 1 has an arm 11 and a grindstone 12 attached to the arm 11, and the grindstone 12 is fixed to an end portion 11a of the arm 11 via a retainer 13. The grindstone 12 comprises a base material 12a and abrasive grains (not illustrated) adhered to the surface of the base material 12a. The abrasive grains are adhered to at least a dressing surface 12b of the grindstone 12.

[0038] The radius of curvature R1 of the dressing surface 12b of the grindstone 12 is configured to be changeable. By changing the radius of curvature R1 of the dressing surface 12b to match the curvature of the rotating plate, the polishing pad 100 can be dressed with a constant pressing pressure to dress the polishing pad 100 more evenly. The specific pad dresser 1 that can change the radius of curvature R1 will be described in detail later.

[0039] In the present disclosure, the dressing surface of the grindstone means the surface of the grindstone 12 that slides on the polishing pad 100 when dressing the polishing pad 100, and in FIG. 1, the dressing surface 12b is the entire lower surface of the grindstone 12. In addition, the radius of curvature of the dressing surface means the radius R1 of the arc when fitting an arc to the surface profile, in the radial direction of the polishing plate, for the dressing surface 12b of the grindstone 12 that slides on the polishing pad 100, as illustrated in FIG. 2. The surface profile of the dressing surface 12b can be measured using a commercially available non-contact shape measuring instrument. Also, fitting of arcs can be performed by the least-squares method or other methods.

[0040] As illustrated in FIG. 1B, the pad dresser 1 configured as described above is moved from one of the inner and outer edges of the lower plate to the other while rotating the lower plate, so that to dress the entire polishing pad 100.

[0041] In the present disclosure, it is preferable to change the radius of curvature R1 of the dressing surface 12b of the grindstone 12 to be smaller than a radius of curvature R2 of a surface of the polishing pad 100, and then to perform dressing of 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 evenly. The radius of curvature R1 of the dressing surface 12b is preferably 10 mm or more. This ensures that the contact area between the grindstone 12 and the polishing pad 100 is sufficient to perform even and efficient dressing of the entire polishing pad 100.

[0042] The radius of curvature of the polishing pad means the radius R2 of the arc when fitting an arc to the surface profile, in the radial direction of the polishing plate, for the surface 100a of the polishing pad 100, as illustrated in FIG. 2. Here, the surface profile is the profile of the entire surface of the polishing pad 100 from one end (e.g., the inner edge) to the other end (e.g., the outer edge). The surface profile of the polishing pad 100 can be measured using a commercially available non-contact shape measuring instrument as well as a dedicated surface profiler. Also, fitting of arcs can be performed by the least-squares method or other methods.

[0043] FIG. 3 illustrates an example of a pad dresser that can be used in the present disclosure, configured to allow the radius of curvature of the dressing surface of the grindstone to be changed. The pad dresser 2 illustrated in FIG. 3 A has a grindstone 22, which has a base material 22a and abrasive grains (not illustrated) adhered to at least the dressing surface of the base material 22a. The grindstone 22 has four dressing surfaces with different radius of curvatures: 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).

[0044] The grindstone 22 is connected to an arm 21 via a rotating shaft 23 and a cylinder 24, as illustrated in FIG. 3B. The dresser is configured to allow the radius of curvature R1 of the dressing surface to be changed by rotating the grindstone 22 in the radial direction of the plate around the rotating shaft 23. The grindstone 22 and the rotating shaft 23 can be fixed by screwing, for example, as illustrated in FIG. 3C.

[0045] For example, SUS with a DLC coated surface can be used as the base material of the grindstone 22. In addition, for example, diamond or ceramic abrasive grains can be used as the abrasive grains.

[0046] In the pad dresser 2 having this configuration, the dressing surface of the grindstone 22 is appropriately selected according to the surface profile of the polishing plate to which the polishing pad 100 is attached. The cylinder 24 then slides the selected dressing surface (in FIG. 3, the dressing surface 22c) onto the rotating polishing pad 100. This allows dressing of the polishing pad 100 with a constant pressing pressure, thus dressing the polishing pad 100 more evenly.

[0047] The pad dresser 2 illustrated in FIG. 3 has four dressing surfaces 22b to 22e, but may have two, three, or five or more dressing surfaces. In addition, the radius of curvature R1 of the dressing surfaces 22b to 22e is not limited to the above values, but can be set appropriately according to the surface profile of the polishing plate to which the polishing pad 100 is attached.

[0048] As illustrated in FIGS. 4 and 5, unlike the pad dresser 2 above, it is also possible to use a pad dresser in which a base material of the grindstone is made of an alloy capable of flexing and the radius of curvature R1 of the dressing surface can be changed by pressing the grindstone from an opposite side of the dressing surface.

[0049] FIG. 4 illustrates another example of a pad dresser that can be used in the present disclosure, configured to allow the radius of curvature of the dressing surface of the grindstone to be changed. In FIG. 4, only the configuration near the grindstone of the pad dresser is illustrated.

[0050] The pad dresser 3, illustrated in FIG. 4, has an arm 31 (not illustrated) and a grindstone 32. The grindstone 32 is secured to a retainer 34 by two fixtures 33, and the retainer 34 is secured to an end portion 31a of the arm 31 (not illustrated). The pad dresser 3 also comprises a pressing member 35, and is configured to allow the radius of curvature R1 of the dressing surface 32b to be changed by pressing a portion of the grindstone 32 on an opposite side of the dressing surface 32b with the pressing member 35.

[0051] The metal capable of flexing that composes the base material 32a of the grindstone 32 is not limited as long as it can be flexed by the pressing member 35, and SUS, titanium, aluminum, superelastic alloys, and the like can be used.

[0052] The pad dresser 3 illustrated in FIG. 4 can reduce the radius of curvature R1 of the dressing surface 32b by increasing the force of pressing the grindstone 32 by the pressing member 35, causing the grindstone 32 to deform as illustrated by the dotted line in FIG. 4. In this way, the radius of curvature R1 of the dressing surface 32b is changed to match the surface profile of the polishing plate, and by sliding the grindstone 32 on the rotating polishing pad 100, the polishing pad 100 is dressed with a constant pressing pressure to dress the polishing pad 100 more evenly.

[0053] FIG. 5 illustrates yet another example of a pad dresser that can be used in the present disclosure, configured to allow the radius of curvature of the dressing surface of the grindstone to be changed. In FIG. 5, only the configuration near the grindstone of the pad dresser is illustrated.

[0054] The pad dresser 4, illustrated in FIG. 5, comprises an arm 41 (not illustrated) and a grindstone 42. The grindstone 42 is secured by a fixture 43 to a retainer 44, which has a different coefficient of thermal expansion than a base material 42a, and is attached to an end portion 41a of the arm 41 (not illustrated) via the retainer 44. A channel 44a through which the liquid W flows is provided inside the retainer 44.

[0055] A liquid W of a predetermined temperature, such as water, is introduced and circulated in the channel 44a of the retainer 44 configured in this way to change the temperature of the grindstone 42 and the retainer 44. Then, the difference in the thermal expansion coefficients between the two will deform the grindstone 42, thereby changing the radius of curvature R1 of the dressing surface 42b. In this way, the radius of curvature R1 of the grindstone 42 is changed to match the surface profile of the polishing plate, and by sliding the grindstone 42 on the rotating polishing pad 100, the polishing pad 100 is dressed with a constant pressing pressure to dress the polishing pad 100 more evenly.

[0056] Metals with different coefficients of thermal expansion can be used as materials for the base material 42a of the grindstone 42 and the retainer 44. For example, the base material 42a of the grindstone 42 can be made of SUS, titanium, aluminum, low thermal expansion alloy (Invar), etc. As for the retainer 44, it can be made of SUS, titanium, aluminum, etc. Specifically, the base material 42a of the grindstone 42 can be made of a low thermal expansion alloy (Invar) and the retainer 44 can be made of SUS, but is not limited to this.

[0057] When making the coefficient of thermal expansion of the retainer 44 larger than that of the base material 42a of the grindstone 42, for example, cold water is distributed as the liquid W in a channel 44a of the retainer 44. This allows the retainer 44 to contract and change the radius of curvature R1 of the dressing surface 42b of the grindstone 42. On the other hand, when making the coefficient of thermal expansion of the retainer 44 smaller than that of the base material 42a of the grindstone 42, for example, high-temperature water is distributed as the liquid W in the channel 44a of the retainer 44. This allows the base material 42a of the grindstone 42 to expand and change the radius of curvature R1 of the dressing surface 42b of the grindstone 42.

[0058] FIG. 6 illustrates still another example of a pad dresser that can be used in the present disclosure, configured to allow the radius of curvature of the dressing surface of the grindstone to be changed. In FIG. 6, only the configuration near the grindstone of the pad dresser is illustrated.

[0059] The pad dresser 5, illustrated in FIG. 6, comprises an arm 51 (not illustrated) and a plurality of grindstones 52. Each grindstone 52 is fixed to the lower surface of a cylinder 53, and the top of the cylinder 53 is fixed to a retainer 54. The retainer 54 is then fixed to the end portion 51a of the arm 51 (not illustrated).

[0060] In the pad dresser 5, the entire lower surface of the plurality of grindstones 52 form a dressing surface, and the radius of curvature R1 of the dressing surface can be changed by changing the degree of expansion and contraction of each cylinder 53. The radius of curvature R1 of the dressing surface can be obtained by fitting the profile of the surface composed of the lower surfaces of all grindstones 52 with a circular arc.

Method for Polishing Silicon Wafer

[0061] The method for polishing a silicon wafer according to the present disclosure is characterized in comprising polishing a silicon wafer using a polishing pad that has been dressed using the method for dressing a polishing pad according to this disclosure described above.

[0062] As described above, in the method for dressing a polishing pad according to this disclosure, because the pad dresser is used which is configured to allow the radius of curvature R1, in the radial direction of the polishing plate, of the dressing surface of the grindstone that slides on the polishing pad to be changed, the polishing pad can be dressed more evenly even when the surface of the rotating plate is curved. As a result, the flatness of a silicon wafer can be improved by polishing the silicon wafer with the dressed polishing pad.

[0063] The method for producing a silicon wafer according to the present disclosure is characterized in comprising polishing a silicon wafer obtained by performing wafer processing treatment on a single crystal silicon ingot grown by a predetermined method, using the method for polishing a silicon wafer according to the present disclosure described above.

[0064] As described above, the method for polishing a silicon wafer according to the present disclosure can improve the flatness of silicon wafers. Therefore, by polishing a silicon wafer obtained by performing wafer processing treatment on a single crystal silicon ingot grown by a predetermined method, such as the Czochralski (CZ) process or floating zone melting process (FZ) process, using the method for polishing a silicon wafer according to the present disclosure, a silicon wafer with higher flatness can be produced.

Device for Polishing Silicon Wafer

[0065] The device for polishing a silicon wafer according to the present disclosure is a device which comprises a polishing plate; a polishing pad attached to the polishing plate; and a pad dresser having a grindstone attached thereto, and dresses the polishing pad. Here, this device is characterized in that it is configured to allow a radius of curvature R1, in the radial direction of the polishing plate, of a dressing surface of the grindstone that slides on the polishing pad to be changed.

[0066] The device for polishing a silicon wafer according to the present disclosure is characterized in that it comprises a pad dresser that can be used for the method for dressing a polishing pad according to the present disclosure described above. Because the polishing device comprises the pad dresser, it is possible to dress the polishing pad with a constant pressing pressure, thereby dressing the polishing pad more evenly. As a result, by polishing a silicon wafer with the dressed polishing pad, the flatness of the silicon wafer can be improved

[0067] The pad dresser can be a pad dresser 2, as illustrated in FIG. 3, in which the grindstone 22 has a plurality of dressing surfaces 22b to 22e with different radius of curvatures, so that the radius of curvature R1 of the dressing surface that slides on the polishing pad 100 can be changed by rotating the grindstone 22.

[0068] Further, the pad dresser can be a pad dresser in which a base material of the grindstone is made of an alloy capable of flexing, so that the radius of curvature R1 of the dressing surface can be changed by pressing the grindstone from an opposite side of the dressing surface.

[0069] Specifically, as illustrated in FIG. 4, the pad dresser can be a pad dresser 3 in which a grindstone 32 is attached to the pad dresser 3 via a retainer 34 and two ends of the base material 32a of the grindstone 32 are coupled to the retainer 34, so that the radius of curvature R1 of the dressing surface 32b can be changed by pressing a portion of the grindstone 32 on the opposite side of the dressing surface 32b with a pressing member 35.

[0070] Alternatively, as illustrated in FIG. 5, the pad dresser can be a pad dresser 4 in which the grindstone 42 is attached to the pad dresser 4 via a retainer 44 that has a different coefficient of thermal expansion than the base material 42a of the grindstone 42, so that the radius of curvature R1 of the dressing surface 42b can be changed by changing temperature of the retainer 44.

[0071] Furthermore, as illustrated in FIG. 6, the pad dresser can be a pad dresser 5 in which an arm 51 (not illustrated) and a plurality of grindstones 52 are provided, each grindstone 52 is fixed to the lower surface of a cylinder 53, and the upper surface of the cylinder 53 is fixed to a retainer 54, so that the radius of curvature R1 of the dressing surface can be changed by changing the degree of expansion and contraction of each cylinder 53.

INDUSTRIAL APPLICABILITY

[0072] This disclosure is useful in the semiconductor wafer manufacturing industry because it enables more even dressing of polishing pads even when the surface of the rotating plate is curved.

REFERENCE SIGNS LIST

[0073] 1, 2, 3, 4, 5 Pad dresser [0074] 11, 21, 31, 41, 51 Arm [0075] 11a, 31a, 41a, 51a End portion [0076] 12, 22, 32, 42, 52 Grindstone [0077] 12a, 22a, 32a, 42a Base material [0078] 12b, 22b, 22c, 22d, 22e, 32b, 42b Dressing surface [0079] 13, 34, 44, 54 Retainer [0080] 23 Rotating shaft [0081] 24, 53 Cylinder [0082] 33, 43 Fixture [0083] 35 Pressing member [0084] 44a Chanell [0085] 100 Polishing pad [0086] R1, R2 Radius of curvature [0087] W Liquid