Device for straightening a urethane foam pad for polishing

Abstract

Straightening device for straightening a urethane foam pad for use in polishing by bringing diamond abrasive media into sliding contact with the urethane foam pad, the straightening device comprising a carrier for holding the diamond abrasive media, the diamond abrasive media held by the carrier having multiple grits, the multi-grit diamond abrasive media comprising a high-grit diamond abrasive media with a grit of 170 or more and a low-grit diamond abrasive media with a grit of 140 or less, the multi-grit diamond abrasive media being held by the carrier such that the height positions of the straightening surfaces of the diamond abrasive media are on the same plane, and the straightening surfaces come into contact with the urethane foam pad; and (i) wherein diamond pellets, to which the diamond grinding elements with multiple grit sizes are attached, are held by the carrier, wherein the thicknesses of the diamond pellets are adjustable, whereby the height positions of the alignment surfaces of the diamond grinding elements are on the same plane; and / or (ii) wherein the thickness of the support is adjustable, whereby the height positions of the alignment surfaces of the diamond grinding bodies are on the same plane.

Description

TECHNICAL FIELD

[0001] The present invention relates to a straightening device for straightening a urethane foam pad for polishing a wafer and a straightening method. STATE OF THE ART

[0002] In wafer polishing, a urethane foam pad was used to improve the flatness of the wafer surfaces. The urethane foam pad for polishing undergoes an initial straightening process to prepare it for use, followed by regular straightening from batch to batch at intervals between polishing batches. Such regular straightening of the urethane foam pad allows for adjustment of the urethane foam pad, thereby maintaining the flatness quality of wafers after polishing.

[0003] Generally, a straightening device with diamond grinding wheels is used to straighten a urethane foam pad. The straightening device is designed to straighten a urethane foam pad by bringing diamond grinding wheels with a grain size, which are arranged evenly or irregularly on a carrier, into sliding contact with the urethane foam pad. LIST OF CITIONSPATENT LITERATURE

[0004] As the closest prior art, the document JP 2004-98 214 A discloses an “adjusting unit” (adjusting mechanism 7) which uses additional means “adjusting screw 7b” and “spacer 7d” in order to adjust the height of the otherwise unchanged bases “base 7a”) of the “first abrasive grain group 5” in accordance with the “second abrasive grain group 6”. Patent Document 1: JP H11-00 868 A Patent document 2: JP 2004- 98 214 A Patent document 3: US 2,309,016 A SUMMARY OF THE INVENTION TECHNICAL TASK

[0005] A urethane foam pad with a soft resin hardness (especially a urethane foam pad with a Shore D hardness of 30 or less) is generally straightened with a diamond grinding wheel straightener as mentioned above, where the diamond grinding wheels typically have a grit of 60, 100, and 325. However, if the urethane foam pad is straightened only with the low-grain diamond grinding wheels of 60 or 100 grit, the diamond grinding wheels will become heavily trapped in the holes of a foam part of the pad, and the urethane resin will be stretched, thus disadvantageously closing the holes of the foam part in the pad. The urethane foam pad, in which the holes of the foam part are closed, cannot hold sufficient slurry for the polishing process, leading to the problem of poor flatness of polished wafers.

[0006] If the urethane foam pad is straightened only with the high-grain diamond abrasives of 325 grit, although the holes in the foam part are not closed, the surface of the foam part of the urethane pad cannot be sufficiently roughened because the diamond abrasives are too fine. Accordingly, the surface roughness of the urethane foam pad becomes low, and the flatness of wafers after polishing cannot be maintained in good condition, thus requiring a shorter straightening interval. For example, if the diamond abrasives of 325 grit are used, optimal flatness of continuously polished wafers cannot be achieved because straightening is performed every three batches. As a result, the number of straightening operations increases, leading to the problem of lower productivity in wafer manufacturing.

[0007] As a suitable straightening method for sufficiently roughening the surface of the urethane foam pad and reducing the closure of holes in the foam part, a straightening method using a straightener with high-grit diamond abrasives and a straightener with low-grit diamond abrasives is worth mentioning. However, this method has poor efficiency and requires a long time for straightening, thereby reducing wafer manufacturing productivity.

[0008] Patent Document 1 discloses a straightening device comprising diamond abrasive particles with different grain diameters (grits) arranged on a support. However, since the support has a fixed height, the height positions of the straightening surfaces of the diamond abrasive particles differ from each other, and thus the amount of contact between the polishing pad and the diamond abrasive particles varies depending on the grain diameter. This poses a problem in that the amount of contact between the high-grain diamond abrasive particle, which has a small abrasive particle diameter, and the polishing pad is reduced, resulting in the high-grain diamond abrasive particle not functioning sufficiently.

[0009] The present invention is intended to solve the problems described above. The object of the present invention is to provide a straightening device capable of sufficiently roughening the surface of a urethane foam pad by straightening once without closing holes in the foam portion of the urethane foam pad, thereby enabling a short straightening time, a long straightening interval, and preventing a decrease in productivity during wafer production. TECHNICAL SOLUTION

[0010] To achieve this object, the present invention provides a straightening device for straightening a urethane foam pad for polishing by bringing diamond grinding wheels into sliding contact with the urethane foam pad, the straightening device comprising a carrier of the diamond grinding wheels, the diamond grinding wheels held by the carrier having multiple grains, the multi-grain diamond grinding wheels comprising a high-grain diamond grinding wheel with a grain of 170 or more and a low-grain diamond grinding wheel with a grain of 140 or less, the multi-grain diamond grinding wheels being held by the carrier such that height positions of straightening surfaces of the diamond grinding wheels are on the same plane, and the straightening surfaces come into contact with the urethane foam pad; and (i) wherein diamond pellets, to which diamond grinding bodies of multiple grain sizes are respectively attached, are held by the carrier, wherein the thicknesses of the diamond pellets are adjustable, whereby the height positions of the straightening surfaces of the diamond grinding bodies are on the same plane; and / or (ii) wherein the thickness of the carrier is adjustable, whereby the height positions of the straightening surfaces of the diamond grinding bodies are on the same plane.

[0011] Such a straightening device allows the high-grain diamond grinding wheel and the low-grain diamond grinding wheel to come into sliding contact with the urethane foam pad simultaneously, thus achieving sufficient surface roughening in a single straightening step without closing any holes in the foam part. This allows for short straightening times and long straightening intervals, and straightening can be performed without reducing productivity.

[0012] Diamond pellets, to which the diamond grinding wheels with multiple grits are attached, can be held by the carrier, whereby the thicknesses of the diamond pellets are adjustable, whereby the height positions of the straightening surfaces of the diamond grinding wheels are on the same level.

[0013] According to this design, the height positions of the straightening surfaces of the diamond grinding wheels can be easily set to the same level by adjusting the thicknesses of the diamond pellets.

[0014] In one embodiment, the thickness of the carrier is adjustable, whereby the height positions of the straightening surfaces of the diamond grinding bodies are on the same level.

[0015] According to this design, even if the diamond grinding wheels are directly electrolytically deposited on the carrier, the height positions of the straightening surfaces of the diamond grinding wheels can be set to the same level by adjusting the thickness of the carrier.

[0016] Preferably, the carrier is a ring-like carrier divided into a plurality of segments, each of the plurality of segments holds either the high-grain diamond abrasive or the low-grain diamond abrasive, and the segment holding the high-grain diamond abrasive and the segment holding the low-grain diamond abrasive are alternately arranged on the same circumference.

[0017] Such a device enables more reliable, effective and uniform straightening of the urethane foam pad without reducing productivity.

[0018] Furthermore, by using the straightening device according to the invention, a urethane foam pad for polishing with a Shore D hardness of 30 or less can be straightened.

[0019] Such a straightening method enables the high-grain diamond abrasive and the low-grain diamond abrasive to come into sliding contact with the urethane foam pad simultaneously, thereby efficiently and effectively straightening the soft urethane foam pad to polish a wafer with high flatness. ADVANTAGEOUS EFFECTS OF THE INVENTION

[0020] The straightening device according to the invention is suitable for sufficiently roughening the surface of a urethane foam pad by straightening it once without closing holes in the foam part of the urethane foam pad, thereby shortening the straightening time. Using this device enables the surface of the urethane foam pad to exhibit good slurry retention after a single straightening and allows for long straightening intervals to maintain the surface roughness in a suitable state for a long time. As a result, wafer manufacturing productivity can be significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows a schematic diagram illustrating an example of the straightening device according to the invention. Fig. 2 shows a schematic diagram illustrating an arrangement of the carrier of the straightening device according to the invention. Fig. 3 is a schematic diagram showing the case where the diamond grinding bodies are uniformly arranged in the straightening device according to the invention. Fig. Fig. 4 is a schematic diagram showing the case where the diamond grinding bodies are unevenly arranged in the straightening device according to the invention. Fig. 5 shows an enlarged side view of a part of the straightening device according to the invention. Fig. 6 is a schematic side view showing the case where the urethane foam pad is straightened by the straightening device according to the present invention. Fig. Figure 7 shows the observation result of the surface condition of the urethane foam pad in Example 1 and Comparative Examples 1 and 2. Fig. Figure 8 shows the measurement result of flatness after one-sided polishing in Example 1 and Comparative Examples 1 and 2. Fig. Figure 9 shows the measurement result of GBIR in Example 2 and Comparative Example 3. DESCRIPTION OF THE EMBODIMENTS

[0021] Embodiments of the present invention will be described below, but the present invention is not limited to these.

[0022] A straightening device using low-grain diamond abrasives (with a large average grain diameter) easily closes holes in the foam part of a urethane foam pad, resulting in impaired flatness of polished wafers. A straightening device using high-grain diamond abrasives (with a small average grain diameter) cannot sufficiently roughen the surface of a urethane foam pad and therefore requires straightening at a shorter straightening interval, resulting in a deterioration in productivity.

[0023] With this in mind, the present inventors conducted studies to solve such problems and came up with the idea of ​​simultaneously bringing diamond abrasive particles of two or more grits into sliding contact with a urethane foam pad. They then conducted repeated and comprehensive studies and found that the aforementioned problems can be solved by constructing a high-grain diamond abrasive particle with a grit of 170 or more and a high-grain diamond abrasive particle with a grit of 140 or less, in which the height positions of the straightening surfaces of the diamond abrasive particles are on the same plane, thus completing the present invention.

[0024] The straightening device according to the invention is described below with reference to Fig. 1 to 6 explained.

[0025] As in Fig. 1 and Fig. As shown in Fig. 2, a straightening device 1 comprises a ring-like plate 6, a ring-like carrier 3 and diamond pellets 5a, 5b to which the diamond grinding bodies 2 are attached.

[0026] The ring-like support 3 is attached to and held by an upper surface of the plate 6. The material of the plate 6 for holding the support 3 can be a metal or a metal whose surface has been subjected to a coating treatment. Illustrative examples of the usable material include stainless steel, resin-coated stainless steel, diamond-like carbon-coated stainless steel, and titanium nitride-coated stainless steel. The coating treatment is not performed on the part that comes into contact with the diamond pellets and requires parallelism.

[0027] As in Fig. As shown in Figure 2, the carrier 3 can be divided into several fan-shaped segments 8 and fan-shaped diamond pellets 5a, 5b can be attached to and held by the divided segments 8.

[0028] High-grain diamond abrasives 2a are attached to the diamond pellets 5a. In the present invention, the high-grain diamond abrasives 2a indicate a diamond abrasives with a grain of 170 or more. On the other hand, low-grain diamond abrasives 2b are attached to the diamond pellets 5b. In the present invention, the low-grain diamond abrasives 2b indicate a diamond abrasives with a grain of 140 or less. As an alternative to the diamond pellets, the diamond abrasives 2a, 2b can be directly electrolytically applied to the corresponding segments 8 of the carrier 3 so that the diamond abrasives 2a, 2b are held by the carrier 3. The diamond abrasives 2a, 2b attached to the diamond pellets 5a, 5b or electrolytically applied to the carrier 3 can be uniformly as in Fig. 3 or uneven as in Fig. 4 shown.

[0029] Preferably, as in Fig. 1 shows the segments 8 for holding the diamond pellets 5a, to which the high-grain diamond abrasives 2a are attached, and the segments 8 for holding the diamond pellets 5b, to which the low-grain diamond abrasives 2b are attached, arranged alternately on the same circumference. Such an arrangement of the segments 8 enables effective and uniform straightening of the urethane foam pad, thereby more reliably preventing a reduction in productivity.

[0030] In the present invention, as in Fig. 5 (a replaced by “a” in Fig. 1), the high-grain diamond grinding bodies 2a and the low-grain diamond grinding bodies 2b are arranged so that the height positions of their straightening surfaces 4 are on the same plane. In particular, the thickness L1 of the diamond pellet 5a and the thickness L2 of the diamond pellet 5b are determined as shown in Fig. 5, adjusted according to the difference in the grain sizes of the respective diamond grinding wheels, whereby the height positions of the straightening surfaces 4 can be brought to the same level. Alternatively, the height of the carrier 3 can be adjusted according to the difference in the grain sizes of the diamond grinding wheels so that the height positions of the straightening surfaces 4 are on the same level. As a further alternative, the thicknesses of the diamond pellets and the height of the carrier can be adjusted so that the height positions are on the same level. If the height positions of the straightening surfaces 4 are on the same level as in Fig. 6, during straightening, both the high-grain diamond grinding bodies 2a and the low-grain diamond grinding bodies 2b can be brought into sliding contact with the surface of the urethane foam pad 7 at the same time.

[0031] According to the straightening device 1 of the present invention, the urethane foam pad 7 is stretched, and the surface of the pad is roughened by scratching (specifically, the SMD is maintained at 3 μm or more to represent the surface roughness of the pad) due to the low-grain diamond abrasives 2b. At the same time, the resin stretched by the low-grain diamond abrasives 2b is cut, and the closing of holes in the foam part due to the high-grain diamond abrasives 2a can be prevented. In addition, since the height positions of the straightening surfaces 4 of the respective diamond abrasives are on the same plane, not only the low-grain diamond abrasives 2b with a large diameter but also the high-grain diamond abrasives 2a with a small diameter can be sufficiently brought into contact with the urethane foam pad 7.As a result, the surface can be roughened without closing holes of the foam part of the urethane foam pad 7, the straightening interval can be extended, and the productivity of wafer manufacturing can be prevented from decreasing.

[0032] The straightening device 1 described above is an exemplary case where the grinding wheels include one type of high-grain diamond grinding wheel and one type of low-grain diamond grinding wheel, thus using two-grain diamond grinding wheels in total. It should be understood that the present invention is not limited to this, and diamond grinding wheels with three or more grains may be used. Furthermore, in the above example, the thicknesses of the diamond pellets and the height of the carrier are respectively adjusted by the diamond pellets and the segments. The present invention is, of course, not limited to this. In order to bring the height positions of the straightening surfaces 4 into the same plane, the height of the carrier and the thicknesses of the diamond pellets can be adjusted by providing steps on the surfaces of the carrier and the diamond pellets or by using a curved surface.

[0033] The straightening device 1 according to the invention as mentioned above can be used for straightening a urethane foam pad having a Shore D hardness of 30 or less. The straightening can be performed, for example, by holding the straightening device 1 by a disc-like rotation drive mechanism and bringing the straightening device 1 into sliding contact with the urethane foam pad 7 while rotating the device.

[0034] Such a straightening method can sufficiently roughen the surface of the urethane foam pad without closing holes in the foam portion of the urethane foam pad, since the straightening device 1 comprises two or more high-grain and low-grain diamond grinding wheels whose straightening surfaces 4 are located on the same plane. Accordingly, the urethane foam pad can be efficiently straightened, allowing wafers to be produced with optimal flatness and improving wafer manufacturing productivity. Thus, the method using the straightening device 1 according to the invention is particularly suitable for straightening a urethane foam pad with a Shore D hardness of 30 or less. EXAMPLE

[0035] Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples; however, the present invention is not limited thereto. (Example 1)

[0036] In a single-side polishing machine for wafers (a single-side polishing machine of the SRED type, manufactured by Fujikoshi Machinery Corp), the straightening device according to the invention, in which height positions of diamond grinding wheels with multiple grains are on the same plane as in Fig. 1, held by a disk-like rotary drive mechanism. Using this straightening device, initial straightening was performed to prepare a new urethane foam pad mounted on a turntable. After initial straightening, the surface condition of the urethane foam pad was observed with a microscope to examine whether holes in the foam part were closed. Subsequently, wafers were single-sided polished in batches with the straightened urethane foam pad, and the flatness of the single-sided polished wafer in the tenth batch was measured.

[0037] During the initial straightening of the urethane foam pad, a high-grain diamond abrasive with a grit of 200 and a low-grain diamond abrasive with a grit of 100 were used as diamond abrasive. The straightening conditions were as follows: The speed of the straightening device was 10 rpm, the speed of the rotary table was 20 rpm, and the load was 35 mg / cm 2 The initial alignment time was 300 seconds. Water was used as the alignment fluid.

[0038] The wafers used for single-sided polishing were p-doped wafers with a diameter of 300 mm and a crystal orientation of <100> . The polishing conditions were as follows: The polishing load was 80 to 200 g / cm 2 The rotational speed of the rotary table was 30 rpm. The rotational speed of the polishing head was 30 rpm. NaOH-based colloidal silica was used as the polishing agent.

[0039] The flatness of the polished wafer was measured using a Nanometoro 300TT-A flatness tester manufactured by Kuroda Precision Industries Ltd.

[0040] Fig. 7 show photographs illustrating the surface condition of the urethane foam pad immediately after initial straightening. As shown in Fig. 7, holes of the foam part were open without closing and the surface except the holes was sufficiently roughened.

[0041] Fig. Figure 8 shows the measurement result of wafer flatness after single-sided polishing. As in Fig. As shown in Figure 8, the wafer after the tenth batch had a GBIR of 0.077 (µm), SFQRmax of 0.028 (µm), and SBIRmax of 0.051 (µm), which are smaller values ​​than those in Comparative Example 2 described below, and thus a wafer with higher flatness could be obtained compared to Comparative Example 2. This result indicates that, even when a straightening interval of 10 batches was selected, which is longer than that in Comparative Example 1 described below, a wafer with higher flatness can be obtained compared to Comparative Example 2. Table 1 shows test results whether holes of the foam part were closed or not and the maximum number of batches for obtaining a wafer with optimal flatness.

[0042] In addition, straightening was performed under the same conditions as before, except that a high-grain diamond abrasive with a grit of 170 and a low-grain diamond abrasive with a grit of 60 were used as the diamond abrasive in the initial straightening. Subsequently, the surface condition of the urethane foam pad was observed, and it was consistently found that holes in the foam part were not closed and the surface was sufficiently roughened. In this case, too, a wafer with high flatness could be obtained even after 10 consecutive polishing batches. Similarly, straightening was performed under the same conditions as before, except that a high-grain diamond abrasive with a grit of 170 and a low-grain diamond abrasive with a grit of 140 were used as the diamond abrasive in the initial straightening.In this case, too, holes in the foam part were not closed, the surface was sufficiently roughened, and a wafer with high flatness was obtained even after 10 consecutive polishing batches. From these results, it could be concluded that using the straightening device according to the invention could improve wafer manufacturing productivity. (Comparison example 1)

[0043] Initial straightening of a urethane foam pad, polishing of a wafer, and flatness measurement were performed under the same conditions as in Example 1, except that only a 325 grit diamond abrasive was used and the flatness measurement was performed on a wafer polished on one side in the third batch.

[0044] As in Fig. 7 and Table 1, although the holes in the foam part were not closed but open, the surface, with the exception of the holes, was not sufficiently roughened. Therefore, as shown in Fig. As shown in Figure 8, although the wafer polished in the third batch after leveling had good GBIR values ​​of 0.079 (µm), SFQRmax of 0.029 (µm), and SBIRmax of 0.053 (µm), a wafer with optimal flatness could not be achieved when the polishing batch was continuously repeated three times. Thus, Comparative Example 1 had a lower maximum batch number for achieving a wafer with optimal flatness and required a leveling interval every three batches or less, resulting in a deterioration in wafer manufacturing productivity compared to Example 1.

[0045] Similarly, initial straightening of a urethane foam pad, wafer polishing, and flatness measurement were performed, but the diamond abrasive grit was changed to 170, 200, or 230. Thus, as shown in Table 1, when only the 230 grit diamond abrasive was used, the maximum batch number for achieving a wafer with optimal flatness was as low as 3 batches, as in the case where only the 325 grit diamond abrasive was used. When only the 170 or 200 grit diamond abrasive was used, the maximum batch number for achieving a wafer with optimal flatness was slightly improved to 5 batches; however, this number was half that of Example 1. (Comparison example 2)

[0046] Initial straightening of a urethane foam pad, polishing of a wafer, and flatness measurement were performed under the same conditions as in Example 1, except that only a 100 grit diamond abrasive was used and the flatness measurement was performed on a wafer polished on one side in the first batch.

[0047] Thus, as in Fig. 7 and Table 1 holes of the foam part closed. Therefore, as in Fig. As shown in Figure 8, the wafer polished in the first batch shortly after leveling exhibited a GBIR of 0.314 (µm), SFQRmax of 0.038 (µm), and SBIRmax of 0.074 (µm), which was significantly worse than in Example 1. Furthermore, the polished wafer exhibited a concave shape, and the wafer shape was compromised. It was found that the urethane foam pad with such a surface condition could not achieve a wafer with optimal flatness, unlike in Example 1.

[0048] Similarly, initial straightening of a urethane foam pad, wafer polishing, and flatness measurement were performed in the same manner, but the diamond abrasive grit was changed to 60, 80, 120, or 140. Thus, as shown in Table 1, holes of the foam part were closed, and a wafer with optimal flatness could not be obtained in all cases. (Comparison example 3)

[0049] Initial straightening of a urethane foam pad, polishing of a wafer, and flatness measurement were performed under the same conditions as in Example 1, except that two diamond abrasives with grits of 60 and 140 were used in combination, and the flatness measurement was performed on a wafer polished on one side in the first batch.

[0050] Thus, as shown in Table 1, holes of the foam part were closed and, unlike in Example 1, no wafer with optimal flatness could be obtained. (Example 2)

[0051] In addition to the same conditions as in Example 1, initial straightening and batch-by-batch straightening were performed every 10 polishing batches using the straightening device of the present invention to measure the GBIR of a wafer after single-side polishing. In Example 2, the batch-by-batch straightening time was 180 seconds, and a WaferSight2 flatness tester manufactured by KLA-Tencor Co. Ltd. was used for flatness measurement.

[0052] Thus, as in Fig. 9 shows the average value of GBIR (average in Fig. 9) 107.9 (nm) and the standard deviation (s in Fig. 9) 29.4 (nm). Thus, it was concluded that the amount of change between the flatness of the wafer polished in the first batch after straightening and the flatness of the wafer polished in the tenth batch after straightening was small. Thus, it turned out that in this case, too, a wafer with high flatness could be achieved even when straightening was performed at a long interval every 10 polishing batches. (Comparison example 4)

[0053] Initial straightening and batch-by-batch straightening of a urethane foam pad, wafer polishing, and flatness measurement were performed under the same conditions as in Example 2, but using only a 325 grit diamond abrasive.

[0054] Thus, as in Fig. 9 shows the average value of GBIR (average in Fig. 9) 142.4 (nm) and the standard deviation (s in Fig.9) 59.0 (nm). Thus, it could be deduced that there was a large amount of change between the flatness of the wafer polished in the first batch after straightening and the flatness of the wafer polished in the tenth batch after straightening. Thus, it turned out that in this case, a wafer with high flatness could only be achieved in several batches after straightening, even if straightening was performed at a long interval every 10 polishing batches.

[0055] The results of examples and comparative examples are summarized in Table 1.

[0056] It should be noted that the present invention is not limited to the foregoing embodiment. The embodiment is merely illustrative, and any example having substantially the same features and effects as the technical concept described in the claims of the present invention is included within the technical scope of the present invention.

Claims

[1] A straightening device for straightening a urethane foam pad for use in polishing by bringing diamond abrasives into sliding contact with the urethane foam pad, the straightening device comprising a carrier for holding the diamond abrasives, the diamond abrasives held by the carrier having multiple grains, the multi-grain diamond abrasives comprising a high-grain diamond abrasive with a grain of 170 or more and a low-grain diamond abrasive with a grain of 140 or less, the multi-grain diamond abrasives being held by the carrier such that height positions of straightening surfaces of the diamond abrasives are on the same plane, and the straightening surfaces come into contact with the urethane foam pad; and (i) wherein diamond pellets, to which diamond grinding bodies of multiple grain sizes are respectively attached, are held by the carrier, wherein the thicknesses of the diamond pellets are adjustable, whereby the height positions of the straightening surfaces of the diamond grinding bodies are on the same plane; and / or (ii) wherein the thickness of the carrier is adjustable, whereby the height positions of the straightening surfaces of the diamond grinding bodies are on the same plane. [2] The straightening device according to claim 1, wherein the carrier is a ring-like carrier divided into a plurality of segments, each of the plurality of segments holds either the high-grain diamond abrasive or the low-grain diamond abrasive, and the segment holding the high-grain diamond abrasive and the segment holding the low-grain diamond abrasive are alternately arranged on the same circumference. [3] A straightening method for straightening a urethane foam pad for use in polishing having a Shore D hardness of 30 or less using a straightening device according to claim 1 or 2.

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