Polishing pad

Abstract

To provide a polishing pad having high polishing speed while suppressing generation of a damage of an object to be polished at the time of polishing, and capable of improving a flatness characteristic of the object to be polished.SOLUTION: A polishing pad has a polishing surface including a surface of a polyurethane resin foaming body. An apparent density of the polyurethane resin foaming body continuously changes from a center point of the polishing surface in an outer peripheral direction.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a polishing pad. [Background technology]

[0002] Polishing pads with polishing surfaces made of polyurethane resin foam are used for planarizing materials that require a high degree of surface flatness, such as silicon wafers. This planarization generally involves chemical mechanical polishing, in which the surface to be processed, such as a silicon wafer, is pressed against the polishing surface of the polishing pad and polished with a slurry-like abrasive containing dispersed abrasive grains.

[0003] Conventional polishing pads generally have uniform physical properties (apparent density, hardness, etc.) within the polishing surface, but the following Patent Documents 1 and 2 disclose polishing pads that have regions with different physical properties within the polishing surface in order to improve the flatness of the polished surface of workpieces such as silicon wafers. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-294412 [Patent Document 2] Special Publication No. 2006-526902 Summary of the Invention [Problem to be solved by the invention]

[0005] The polishing pads described in Patent Documents 1 and 2 have discontinuous changes in physical properties, and therefore discontinuous wear occurs due to the surface dressing treatment during use, which may cause damage such as scratches to the object being polished, such as a wafer.

[0006] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a polishing pad that has a high polishing rate while suppressing damage to the polished object during polishing and can improve the planarization characteristics of the polished object. [Means for solving the problem]

[0007] The present invention provides A polishing pad having a polishing surface formed of a surface of a polyurethane resin foam, The polishing pad has an apparent density of the polyurethane resin foam that changes continuously from the center of the polishing surface toward the outer periphery.

[0008] The present invention provides A polishing pad having a polishing surface formed of a surface of a polyurethane resin foam, The polishing pad has an average pore diameter of the polyurethane resin foam that changes continuously from the center of the polishing surface toward the outer periphery. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a polishing pad that has a high polishing rate while suppressing damage to the object to be polished during polishing, and that can improve the planarization characteristics of the object to be polished. [Brief explanation of the drawings]

[0010] [Figure 1] Schematic diagram for explaining a method for measuring the physical properties of polyurethane resin foam [Figure 2] Graph showing evaluation results of polyurethane resin foam according to Example 1 [Figure 3] Graph showing evaluation results of polyurethane resin foam according to Example 2 [Figure 4] Graph showing evaluation results of polyurethane resin foam according to Comparative Example 1 DETAILED DESCRIPTION OF THE INVENTION

[0011] First Embodiment The polishing pad of the first embodiment is A polishing pad having a polishing surface formed of a surface of a polyurethane resin foam, The polishing pad of the first embodiment has a polishing surface having a surface area of ​​100 mm or less, and a polishing rate of 100 mm or less, and a polishing surface area ...

[0012] The polyurethane resin foam is a foam of polyurethane resin and has a large number of bubbles (hereinafter also referred to as pores). The polyurethane resin is obtained by curing a polyurethane resin composition containing at least an isocyanate group-containing compound and an active hydrogen-containing compound, and the polyurethane resin has a structure in which a structural unit derived from the isocyanate group-containing compound and a structural unit derived from the active hydrogen-containing compound are urethane-bonded.

[0013] The isocyanate group-containing compound can be any compound having an isocyanate group known in the field of polyurethanes without any particular limitation. Examples of the isocyanate group-containing compound include aromatic diisocyanates such as 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate, p-xylylene diisocyanate, and m-xylylene diisocyanate; aliphatic diisocyanates such as ethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and 1,6-hexamethylene diisocyanate; and alicyclic diisocyanates such as 1,4-cyclohexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, and norbornane diisocyanate. These may be used alone or in combination of two or more.

[0014] The active hydrogen-containing compound can be any compound having one or more active hydrogen groups capable of reacting with an isocyanate group to form a urethane bond. Examples of the active hydrogen group include a hydroxyl group, a primary amino group, a secondary amino group, and a thiol group (SH).

[0015] As the active hydrogen-containing compound having a hydroxyl group, a high molecular weight polyol or a low molecular weight polyol can be used.

[0016] Examples of the high molecular weight polyol include polyether polyols typified by polytetramethylene ether glycol and polyethylene glycol, polyester polyols typified by polybutylene adipate, polyester polycarbonate polyols exemplified by polycaprolactone polyols and reaction products of polyester glycols such as polycaprolactone with alkylene carbonates, polyester polycarbonate polyols obtained by reacting ethylene carbonate with a polyhydric alcohol and then reacting the resulting reaction mixture with an organic dicarboxylic acid, and polycarbonate polyols obtained by transesterification of a polyhydroxyl compound with an aryl carbonate.

[0017] Examples of the low molecular weight polyols include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol, diethylene glycol, triethylene glycol, 1,4-bis(2-hydroxyethoxy)benzene, trimethylolpropane, glycerin, 1,2,6-hexanetriol, pentaerythritol, tetramethylolcyclohexane, methyl glucoside, sorbitol, mannitol, dulcitol, sucrose, 2,2,6,6-tetrakis(hydroxymethyl)cyclohexanol, diethanolamine, N-methyldiethanolamine, and triethanolamine.

[0018] Examples of the active hydrogen-containing compound having the primary amino group or the secondary amino group include 4,4'-methylenebis(o-chloroaniline) (MOCA), 2,6-dichloro-p-phenylenediamine, 4,4'-methylenebis(2,3-dichloroaniline), 3,5-bis(methylthio)-2,4-toluenediamine, 3,5-bis(methylthio)-2,6-toluenediamine, 3,5-diethyltoluene-2,4-diamine, 3,5-diethyltoluene-2,6-diamine, trimethylene glycol-di-p-aminobenzoate, polytetramethylene oxide-di-p-aminobenzoate, 4,4'-diamino-3,3',5,5'-tetraethyldiphenylmethane, 4,4'-diamino-3,3'-diisopropyl-5,5'-dimethyl ... Examples of suitable polyamines include high molecular weight polyamines such as N-3,3',5,5'-tetraisopropyldiphenylmethane, 1,2-bis(2-aminophenylthio)ethane, 4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane, N,N'-di-sec-butyl-4,4'-diaminodiphenylmethane, 3,3'-diethyl-4,4'-diaminodiphenylmethane, m-xylylenediamine, N,N'-di-sec-butyl-p-phenylenediamine, m-phenylenediamine, and p-xylylenediamine; low molecular weight polyamines such as ethylenediamine, tolylenediamine, diphenylmethanediamine, and diethylenetriamine; and alcohol amines such as monoethanolamine, 2-(2-aminoethylamino)ethanol, and monopropanolamine.

[0019] The active hydrogen-containing compounds may be used alone or in combination of two or more kinds.

[0020] The polyurethane resin composition may contain a foam stabilizer, a filler, an antistatic agent, and other additives.

[0021] The isocyanate group-containing compound and the active hydrogen-containing compound used in the production of the polyurethane resin foam can be varied depending on the molecular weight of each compound and the desired physical properties of the polishing pad.

[0022] From the viewpoint of suppressing scratching during polishing, the polyurethane resin constituting the polyurethane resin foam is preferably a single polyurethane resin as a whole, i.e., the polyurethane resin as a whole has a structure in which structural units derived from the same isocyanate group-containing compound and structural units derived from the same active hydrogen-containing compound are urethane-bonded. From the same viewpoint, it is also preferable that the polyurethane resin foam is not formed by joining polyurethane resin foams of the same or different types of polyurethane resin. In other words, it is preferable that the polyurethane resin foam does not have a joining surface.

[0023] The apparent density of the polyurethane resin foam is preferably 0.20 g / cm from the viewpoint of improving the polishing rate and the planarization characteristics of the object to be polished. 3 More than 0.80g / cm 3 More preferably, it is 0.30 g / cm or less. 3 More than 0.70g / cm 3 In this specification, the apparent density is measured based on JIS K7222:2005.

[0024] From the viewpoint of improving the polishing speed and the planarization characteristics of the workpiece, it is preferable that the apparent density of the polyurethane resin foam continuously increases from the center point of the polishing surface formed by the surface of the polyurethane resin foam toward the periphery. From the same viewpoint, it is preferable that the apparent density of the polyurethane resin foam continuously increases from the center point of the polishing surface toward the periphery. -6 g / cm 3 / mm or more 3.0×10 -4 g / cm 3 / mm or less, it is more preferable that the density continuously increases at a rate of 9.0 × 10 -6 g / cm 3 / mm or more 1.0×10 -4g / cm 3 It is more preferable that the thickness continuously increases at a rate of 1 / mm or less.

[0025] The average pore diameter of the pores in the polyurethane resin foam is preferably 60 μm or more and 200 μm or less, more preferably 65 μm or more and 180 μm or less, and even more preferably 70 μm or more and 170 μm or less, from the viewpoint of improving the polishing rate and the planarization property of the object to be polished. In this specification, the average pore diameter is measured by the method described in the Examples.

[0026] From the viewpoint of improving the polishing rate and the planarization characteristics of the workpiece, the average pore diameter of the pores of the polyurethane resin foam preferably changes continuously from the center point of the polishing surface toward the periphery, and more preferably decreases continuously from the center point of the polishing surface toward the periphery. From the same viewpoint, the average pore diameter of the polyurethane resin foam is preferably 1.0×10 -4 um / mm or more 3.0×10 -2 It is more preferable that the particle size continuously decreases at a rate of 9.0×10 -3 um / mm or more 1.0×10 -2 It is even more preferable that the density continuously decreases at a rate of um / mm or less.

[0027] From the viewpoint of improving the polishing rate and the planarization properties of the object to be polished, the polyurethane resin foam preferably has a JIS-A hardness of 75 or more and 95 or less. The JIS-A hardness is measured based on the hardness test according to Type A of JIS K6253-3:2012, and is measured by pressing a needle into the polishing surface.

[0028] In order to improve the polishing rate and the planarization property of the object to be polished, the polyurethane resin foam has a JIS-A hardness change of −3.3×10 from the center point of the polishing surface toward the periphery. -3 JIS-A hardness / mm or more 3.3×10 -3 It is preferable that the hardness is JIS-A / mm or less.

[0029] The thickness of the polyurethane resin foam is not particularly limited, but is generally about 0.5 to 2.0 mm.

[0030] The polyurethane resin foam can be produced by applying a known urethane-forming technique such as a prepolymer method.

[0031] When producing the polyurethane resin foam using the prepolymer method, for example, at least an isocyanate-terminated prepolymer obtained by reacting an isocyanate group-containing compound with an active hydrogen-containing compound, the active hydrogen-containing compound, and a blowing agent are mixed in a closed system, and the mixture is continuously discharged from the center of a flat mold. The discharged mixture is then cast into a mold while curing and foaming, spreading in a circular pattern from the center toward the periphery of the mold. This allows for the production of a polyurethane resin foam with different physical properties from the center of the mold (corresponding to the center of the polished surface) to the periphery of the mold (corresponding to the periphery of the polished surface). The production conditions for the polyurethane resin foam cannot be determined uniquely because they vary depending on factors such as the reaction rate between the isocyanate-terminated prepolymer and the active hydrogen-containing compound used. However, the polyurethane resin foam can be produced by adjusting various conditions, such as the reaction rate between the isocyanate-terminated prepolymer and the active hydrogen-containing compound, the viscosity of the mixture of the isocyanate-terminated prepolymer and the active hydrogen-containing compound, the foaming rate due to the blowing agent, the discharge rate of the mixture, the temperature of the mixture, and the temperature of the mold.

[0032] Second Embodiment The polishing pad of the second embodiment is A polishing pad having a polishing surface formed of a surface of a polyurethane resin foam, The average pore diameter of the polyurethane resin foam varies continuously from the center point of the polishing surface toward the periphery. The polishing pad of the second embodiment achieves a high polishing rate while suppressing damage to the workpiece during polishing, and improves the planarization characteristics of the workpiece. The polishing pad of the second embodiment will be described below, but explanations of content that overlaps with the polishing pad of the first embodiment may be omitted.

[0033] The average pore diameter of the pores in the polyurethane resin foam is preferably 60 μm or more and 200 μm or less, more preferably 65 μm or more and 180 μm or less, and even more preferably 70 μm or more and 170 μm or less, from the viewpoint of improving the polishing rate and the planarization property of the object to be polished. In this specification, the average pore diameter is measured by the method described in the Examples.

[0034] From the viewpoint of improving the polishing rate and the planarization characteristics of the workpiece, the average pore diameter of the pores of the polyurethane resin foam preferably changes continuously from the center point of the polishing surface toward the periphery, and more preferably decreases continuously from the center point of the polishing surface toward the periphery. From the same viewpoint, the average pore diameter of the polyurethane resin foam is preferably 1.0×10 -4 um / mm or more 3.0×10 -2 It is more preferable that the particle size continuously decreases at a rate of 9.0×10 -3 um / mm or more 1.0×10 -2 It is even more preferable that the density continuously decreases at a rate of um / mm or less.

[0035] The apparent density of the polyurethane resin foam is preferably 0.20 g / cm from the viewpoint of improving the polishing rate and the planarization characteristics of the object to be polished. 3 More than 0.80g / cm 3 More preferably, it is 0.30 g / cm or less. 3 More than 0.70g / cm 3 The following is the result.

[0036] From the viewpoint of improving the polishing speed and the planarization characteristics of the workpiece, it is preferable that the apparent density of the polyurethane resin foam continuously increases from the center point of the polishing surface formed by the surface of the polyurethane resin foam toward the periphery. From the same viewpoint, it is preferable that the apparent density of the polyurethane resin foam continuously increases from the center point of the polishing surface toward the periphery. -6 g / cm 3 / mm or more 3.0×10 -4 g / cm 3 / mm or less, it is more preferable that the density continuously increases at a rate of 9.0 × 10 -6 g / cm 3 / mm or more 1.0×10 -4 g / cm 3 It is more preferable that the thickness continuously increases at a rate of 1 / mm or less.

[0037] From the viewpoint of improving the polishing rate and the planarization properties of the object to be polished, the polyurethane resin foam preferably has a JIS-A hardness of 75 or more and 95 or less. The JIS-A hardness is measured based on the hardness test according to Type A of JIS K6253-3:2012, and is measured by pressing a needle into the polishing surface.

[0038] In order to improve the polishing rate and the planarization property of the object to be polished, the polyurethane resin foam has a JIS-A hardness change of −3.3×10 from the center point of the polishing surface toward the periphery. -3 JIS-A hardness / mm or more 3.3×10 -3 It is preferable that the hardness is JIS-A / mm or less. [Example]

[0039] <Polishing pad manufacturing example> [Examples 1 and 2] The mixture obtained by mixing the prepolymer, water as a foaming agent, foam stabilizer, curing agent, and catalyst in the amounts shown in Table 1 in a closed system using a stirring blade was poured at a constant speed without interruption into the center of a mold (a regular octagonal flat mold with a diagonal length passing through the center of 2050 mm) that had been heated in an oven at 100°C for 20 minutes, and then cured at 100°C for 25 minutes and demolded to obtain a polyurethane resin foam. The polyurethane resin foam was sliced ​​to obtain a polishing pad made of polyurethane resin foam, a regular octagonal shape with a diagonal length passing through the center of 2050 mm and a thickness of 0.9 mm. The notations in Table 1 have the following meanings: Prepolymer A: Isocyanate-terminated urethane prepolymer (NCO%: 8.40%) obtained by reacting toluene diisocyanate, diethylene glycol, and polytetramethylene ether glycol MOCA: 4,4'-methylenebis(2-chloroaniline) Catalyst: Amine catalyst Foam stabilizer: Silicone foam stabilizer SZ-1671 (manufactured by Toray Dow Corning)

[0040] Comparative Example 1 Polishing pads made of polyurethane resin foam were obtained in the same manner as in each of the Examples, except that the raw materials were stirred in an open system.

[0041] <Evaluation method> [Method for evaluating the rate of change in apparent density in polyurethane resin foam] The method for evaluating the rate of change in apparent density within a polyurethane resin foam will be described with reference to FIG. 1. FIG. 1 shows a view of a polyurethane resin foam 1 viewed toward a polished surface 2. The center 21 of the polished surface 2 was set to 0 mm, and the apparent density within the polyurethane resin foam was measured every 200 mm from the center 21 along an imaginary line 3 passing through the center 21 according to JIS K7222:2005. For data processing, the distance from the center 21 to the left of the measurement point in FIG. 1 was treated as a negative value, while the distance from the center 21 to the right of the measurement point in FIG. 1 was treated as a positive value. A linear equation was calculated using the least squares method from the apparent density of each measurement point within the polyurethane resin foam and the distance from the center 21 at which the apparent density was measured. The absolute value of the slope of the linear equation was used to represent the rate of change in apparent density. The evaluation results are shown in Table 1.

[0042] [Method for Evaluating the Apparent Density of the Whole Polyurethane Resin Foam] The average value of the "apparent density" at each measurement point in the polyurethane resin foam measured by the above-mentioned "method for evaluating the rate of change in apparent density in a polyurethane resin foam" was taken as the apparent density of the entire polyurethane resin foam. The evaluation results are shown in Table 1.

[0043] [Method for evaluating the rate of change in average pore diameter within polyurethane resin foam] The method for evaluating the rate of change in the average pore diameter within a polyurethane resin foam will be described with reference to FIG. 1. The center 21 of the polished surface 2 was set at 0 mm, and cross-sectional images (measurement range: 1.6 mm x 1.6 mm x 0.7 mm) of the polyurethane resin foam in the direction perpendicular to the polished surface were taken every 200 mm from the center 21 along an imaginary line 3 passing through the center 21 using an X-ray CT scanner (TDM1000H-I, manufactured by Yamato Scientific Co., Ltd.). The cross-sectional images were then binarized using image processing software (VGStudioMAX2.1, manufactured by VOLUMEGRAPHICS Co., Ltd.) to clearly distinguish between pores and areas other than pores (areas where polyurethane resin is present). Next, The volume of each pore was measured, and the diameter of a sphere with the same volume was taken as the pore diameter. For data processing, the further the measurement point was from the center 21 in Figure 1 to the left, the negative value was the distance from the center 21, and the further the measurement point was from the center 21 to the right, the positive value was the distance from the center 21. A linear equation was calculated by the least squares method from the "average pore diameter" of each measurement point within the polyurethane resin foam and the "distance from the center 21 at which the average pore diameter was measured," and the absolute value of the slope of the linear equation was taken as the percentage change in average pore diameter. The evaluation results are shown in Table 1.

[0044] [Method for evaluating the average pore diameter of the entire polyurethane resin foam] The average value of the "average pore diameter" at each measurement point in the polyurethane resin foam measured by the above-mentioned "method for evaluating the rate of change in average pore diameter in a polyurethane resin foam" was taken as the average pore diameter of the entire polyurethane resin foam. The evaluation results are shown in Table 1.

[0045] [Method for evaluating the rate of change in JIS-A hardness within polyurethane resin foam] The method for evaluating the rate of change in JIS-A hardness within a polyurethane resin foam will be described with reference to FIG. 1. The center 21 of the polished surface 2 was set at 0 mm, and the JIS-A hardness was measured every 200 mm from the center 21 along an imaginary line 3 passing through the center 21, based on the Type A hardness test of JIS K6253-3:2012. A linear equation was calculated using the least squares method from the "JIS-A hardness" of each measurement point within the polyurethane resin foam and the "distance from the center 21 at which the JIS-A hardness was measured." The absolute value of the slope of the linear equation was taken as the rate of change in JIS-A hardness. The JIS-A hardness of each example and comparative example was 90 degrees, and the rate of change in JIS-A hardness within the polyurethane resin foam of each example and comparative example was 0.

[0046] [Evaluation of planarization characteristics] [Polishing conditions] A polishing test was carried out under the following conditions using polishing pads made of polyurethane resin foam according to each of the examples and comparative examples. Polished object: Etche dwafer Polishing machine: DMS 20B-5P-4D, manufactured by Speed ​​FAM Slurry flow rate: 5L / min Slurry type: NP6610 diluted with water (NP6610:water = 1:30 (volume ratio))

[0047] [Evaluation method] The planarization characteristics were evaluated using a Nanometro 300TT-A (Kuroda Precision Industries, Ltd.) to measure GBIR (Global Backside Ideal Range) and ESFQR (Edge Site Front-Rest Square). GBIR indicates global flatness and is measured over the entire wafer surface, excluding the periphery. ESFQR, on the other hand, indicates periphery site flatness and relates to the flatness of a limited area of ​​the wafer, roughly corresponding to the area of ​​the semiconductor components fabricated therein. Lower values ​​indicate better results. Measurements were performed for each polishing test using the polishing pads of each example. Since this polishing machine can polish five wafers at a time, the average values ​​for these five wafers were used for evaluation. The results are shown in Table 1.

[0048] [Evaluation of Polishing Rate] The removal rate was calculated by dividing the thickness reduced by the polishing by the polishing time.

[0049] FIG. 2 is a graph plotting the measurement results of the average pore diameter, apparent density, and JIS-A hardness for Example 1, FIG. 3 is a graph plotting the measurement results of the average pore diameter, apparent density, and JIS-A hardness for Example 2, and FIG. 4 is a graph plotting the measurement results of the average pore diameter, apparent density, and JIS-A hardness for the comparative example.

[0050] [Table 1]

[0051] 2 to 4, it can be seen that although the polyurethane resin foams according to each Example have a relatively constant JIS-A hardness from the center to the periphery, the average pore diameter decreases continuously from the center to the periphery, and the apparent density increases continuously from the center to the periphery. On the other hand, the polyurethane resin foams according to the Comparative Examples have a relatively constant JIS-A hardness, average pore diameter, and apparent density from the center to the periphery.

[0052] 2 to 4 and Table 1, it can be seen that polishing pads made of polyurethane resin foams according to Examples, in which the JIS-A hardness is relatively constant from the center to the periphery, but the average pore size decreases continuously from the center to the periphery, and the apparent density increases continuously from the center to the periphery, are superior in GBIR, ESFQR, and polishing rate to polishing pads made of polyurethane resin foams according to Comparative Examples, in which the JIS-A hardness, average pore size, and apparent density are relatively constant from the center to the periphery. Furthermore, because the polyurethane resin foams according to Examples are made of a single polyurethane resin and do not have a bonding surface, it can be inferred that polishing pads made of polyurethane resin foams according to Examples can suppress damage such as scratches on the polished object during polishing. [Explanation of symbols]

[0053] 1 polyurethane resin foam, 2 polishing surface, 21 center of polyurethane resin foam, 3 imaginary line

Claims

1. A polishing pad having a polishing surface formed of a surface of a polyurethane resin foam, The polishing pad has an apparent density of the polyurethane resin foam that changes continuously from the center point of the polishing surface toward the outer periphery.

2. A polishing pad having a polishing surface formed of a surface of a polyurethane resin foam, A polishing pad in which the average pore diameter of the polyurethane resin foam changes continuously from the center point of the polishing surface toward the outer periphery.

3. A polishing pad having a polishing surface formed of a surface of a polyurethane resin foam, 3. The polishing pad according to claim 1, wherein the apparent density and average pore diameter of the polyurethane resin foam vary continuously from the center of the polishing surface toward the outer periphery.

4. 4. The polishing pad according to claim 3, wherein the apparent density of the polyurethane resin foam increases continuously from the center of the polishing surface toward the outer periphery.

5. The apparent density of the polyurethane resin foam is 1.0 × 10 from the center point of the polishing surface toward the periphery. －６ g / cm ３ / mm or more 3.0×10 －４ g / cm ３ 5. The polishing pad of claim 4, wherein the surface roughness increases continuously at a rate of 1 / mm or less.

6. 4. The polishing pad according to claim 3, wherein the average pore diameter of the polyurethane resin foam decreases continuously from the center of the polishing surface toward the outer periphery.

7. The average pore diameter of the polyurethane resin foam is 1.0 × 10 from the center point of the polishing surface toward the outer periphery. －４ um / mm or more 3.0×10 －２ 7. The polishing pad of claim 6, wherein the surface roughness decreases continuously at a rate of um / mm or less.

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