Polishing pad, polishing method, and method for manufacturing a polishing pad

Abstract

To provide a polishing pad that excels in both polishing rate and maintenance of that polishing rate. [Solution] The surface with the maximum bubble area ratio is such that the average aspect ratio of the openings of the depressions originating from multiple bubbles is 1.00 or more and 2.00 or less, and the sum of the equivalent diameters of the openings of the depressions originating from multiple bubbles per unit area is 9.0 mm / mm 2 61.0 mm / mm 2 The polishing pad is characterized in that, as described below, the surface with the maximum bubble area ratio has a bubble area ratio of 55% or more and 95% or less.

Description

[Technical Field]

[0001] This disclosure relates to a polishing apparatus, a polishing method, and a method for manufacturing a polishing pad. [Background technology]

[0002] Conventionally, polishing with free abrasive particles has been used as a method for precisely polishing the surface of objects to be polished, such as glass substrates used in lenses, display mask blanks, compound semiconductor wafers of silicon and silicon carbide, gallium nitride, gallium oxide, diamond, silicon oxide insulating films, semiconductor devices containing metals such as copper, tungsten, and other barrier metals, and hard disks, to transfer their shape or flatten them.

[0003] In polishing with free abrasive particles, the general method involves supplying a slurry containing free abrasive particles between the workpiece and the polishing pad, while rotating and oscillating the workpiece and the polishing pad individually to bring them into contact.

[0004] To improve the productivity of free abrasive polishing, an increase in the polishing rate is required. Polishing is thought to proceed as abrasive particles in the slurry come into contact with the workpiece by the pad. Therefore, an increase in the area where the pad contacts the workpiece with the abrasive particles is expected to improve the polishing rate.

[0005] For example, Patent Document 1 describes an approach to control the length of the edges of the microscopic hollow spherical bodies on the polishing surface of a polishing pad, as these contribute to polishing. Patent Document 2 focuses on the contact area between the pad and the workpiece, and attempts to improve the polishing rate by increasing this area using organic fiber fillers. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 6439958 [Patent Document 2] Patent No. 6196773 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] However, the structure of the above-mentioned literature was insufficient from the perspective of aiming for further improvement of the polishing rate. Furthermore, it is desirable for the polishing rate to remain stable between dressings, but the structure of the above-mentioned literature needed further improvement.

[0008] The object of this disclosure is to provide a polishing pad that is excellent in terms of polishing rate and maintenance of that polishing rate. The object of this disclosure is to provide a polishing method that is excellent in terms of polishing rate and maintenance of that polishing rate. The object of this disclosure is to provide a method for manufacturing a polishing pad that is excellent in terms of polishing rate and maintenance of that polishing rate. [Means for solving the problem]

[0009] To address the above issues, this disclosure provides: A polishing pad for polishing a workpiece with free abrasive particles, The polishing pad has a resin sheet having multiple air bubbles, Based on the X-ray CT measurement results of the resin sheet, multiple cross-sections are determined at depths of 4 μm from the surface on which the workpiece is being polished to the opposite surface on the same side, parallel to the surface on which the workpiece is being polished. When the sum of the area of ​​the openings of the multiple depressions originating from bubbles per unit area in each of these multiple cross-sections is defined as the bubble area ratio, The resin sheet has a surface among the multiple cross-sections that has the largest air bubble area ratio, The surface with the maximum bubble area ratio is one in which the average aspect ratio of the openings of the recesses originating from the multiple bubbles is 1.00 or more and 2.00 or less. The surface with the highest bubble area ratio is one where the sum of the equivalent diameters of the openings of the multiple bubble-derived recesses per unit area is 9.0 mm / mm 2 61.0 mm / mm2 is as follows, The surface where the gas bubble area ratio is maximum is such that the gas bubble area ratio is 55 area% or more and 95 area% or less, which is a polishing pad. Further, the present disclosure relates to a polishing method using a polishing pad for polishing an object to be polished with free abrasive grains, where the polishing pad is the above-described polishing pad, and when the surface where the gas bubble area ratio is maximum or the surface in the vicinity thereof is not exposed on the surface of the resin sheet, the method includes a step of exposing the surface where the gas bubble area ratio is maximum or the surface in the vicinity thereof from the resin sheet to the surface of the resin sheet. Further, the present disclosure relates to a step of charging uncured resin into a coaxial centrifugal forming device, forming an uncured resin layer on the inner peripheral surface of the coaxial centrifugal forming device by centrifugal force, and heating and curing the uncured resin layer to produce a resin sheet, where the resin sheet has a plurality of bubbles, From the measurement result of X-ray CT of the resin sheet, when a plurality of cross-sections are obtained every 4 μm in depth from the surface on the side for polishing the object to be polished to the surface on the opposite side of the surface on the side for polishing the object to be polished parallel to the surface on the side for polishing the object to be polished, and the sum value of the areas of the openings of the recesses derived from the plurality of bubbles per unit area in each of the plurality of cross-sections is defined as the gas bubble area ratio, the resin sheet has a surface where the gas bubble area ratio is maximum among the plurality of cross-sections, the average aspect ratio of the openings of the recesses derived from the plurality of bubbles on the surface where the gas bubble area ratio is maximum is 1.00 or more and 2.00 or less, the total value of the equivalent circle diameters of the openings of the recesses derived from the plurality of bubbles per unit area on the surface where the gas bubble area ratio is maximum is 9.0 mm / mm 2 or more and 61.0 mm / mm 2 or less, and the gas bubble area ratio on the surface where the gas bubble area ratio is maximum is 55 area% or more and 95 area% or less. This is a method for manufacturing a polishing pad.

Advantages of the Invention

[0010] According to the present disclosure, it is possible to provide a polishing pad that exhibits a polishing rate higher than that of the prior art and is excellent in the retention of the polishing rate, and a polishing method using the polishing pad.

Brief Description of the Drawings

[0011] [Figure 1] (a) Perspective view showing the concept of the recesses and openings derived from bubbles of the present disclosure, (b) Cross-sectional view showing the concept of the recesses and openings derived from bubbles of the present disclosure. [Figure 2] Conceptual diagram of the equivalent circle diameter of the opening of the recess derived from bubbles. [Figure 3] Configuration example of a centrifugal molding machine used for centrifugal molding. [Figure 4] Schematic diagram of the method for defining the measurement surface in X-ray CT apparatus measurement and analysis.

Modes for Carrying Out the Invention

[0012] In the present disclosure, the description of "XX or more and YY or less" or "XX to YY" representing a numerical range means a numerical range including the lower limit and the upper limit which are the endpoints, unless otherwise specified.

[0013] 〔First Embodiment〕 The first embodiment relates to a polishing pad. The polishing pad of the present disclosure is a polishing pad for polishing an object to be polished with free abrasive grains, the polishing pad having a resin sheet having a plurality of bubbles, from the measurement result of X-ray CT of the resin sheet, a plurality of cross-sections are obtained every 4 μm from the surface on the side for polishing the object to be polished to the opposite surface of the surface on the side for polishing the object to be polished parallel to the surface on the side for polishing the object to be polished, and when the total value of the area of the openings of the plurality of recesses derived from the plurality of bubbles per unit area in each of the plurality of cross-sections is defined as the bubble area ratio, the resin sheet has a surface in the plurality of cross-sections where the bubble area ratio is the maximum, The surface with the maximum bubble area ratio is one in which the average aspect ratio of the openings of the recesses originating from the multiple bubbles is 1.00 or more and 2.00 or less. The surface with the highest bubble area ratio is one where the sum of the equivalent diameters of the openings of the multiple bubble-derived recesses per unit area is 9.0 mm / mm 2 61.0 mm / mm 2 The following: The surface with the maximum bubble area ratio is one where the bubble area ratio is between 55% and 95%. It is characterized by the following: The explanation is as follows.

[0014] Figure 1 is a conceptual diagram of bubble-derived recesses and openings on the surface or near the surface where the bubble area ratio is maximum in this disclosure. Although the figure shows a single bubble-derived recess, in reality there are multiple bubble-derived recesses. Figure 2 is a conceptual diagram of the equivalent diameter of an equiarea circle at the opening of a recess originating from an air bubble.

[0015] According to the inventors' research, the above-mentioned polishing pad makes it possible to provide a polishing pad that exhibits a higher polishing rate than conventional pads while also having excellent retention of that polishing rate, as well as a polishing method using the polishing pad. The details are described below.

[0016] Although there are various theories about the mechanism by which polishing by free abrasive particles progresses, it is basically carried out by the contact of the abrasive particles with the object to be polished by the polishing pad, and it is thought that increasing the area of ​​the polishing pad that has the function of contacting the abrasive particles contributes to an improvement in the polishing rate.

[0017] Many aspects of the polishing pad remain unclear, such as exactly where the abrasive particles make contact with the workpiece, whether it's limited to the true contact area, or whether other parts also have some degree of contact function during the relative motion between the polishing pad and the workpiece. There is also debate as to whether the total contact amount of abrasive grains is important, or whether the projected diameter relative to the relative motion direction of the polishing pad and the workpiece is the essential factor.

[0018] The inventors hypothesized that the dominant factor in the polishing rate is not the simple contact amount of the abrasive grains, but rather the projected diameter with respect to the relative direction of motion between the polishing pad and the workpiece. This is because, considering abrasive grains behind a given abrasive grain as viewed from the direction of motion, and abrasive grains arranged in parallel, it seems clear that the latter contribute more to the polishing rate than the former.

[0019] As a result of their investigation, the inventors found that the sum of the projected diameters of the depressions originating from air bubbles on the surface of the polishing pad with the maximum air bubble area ratio, or on a nearby surface, with respect to the relative motion direction between the polishing pad and the workpiece, correlates with the polishing rate.

[0020] In particular, when the relative motion of the polishing pad and the workpiece involves rotational motion, or when the depressions caused by air bubbles are roughly spherical, the anisotropy due to the bubble shape is eliminated, and the projected diameter can be considered equal to the equivalent diameter of an equiarea circle. Therefore, the polishing rate correlates with the sum of the equivalent diameters of equiarea circles of the depressions caused by air bubbles in the polishing pad, multiplied by the number of depressions.

[0021] Although the details of the principle remain unclear, it is thought that abrasive grains held at the edges of depressions originating from air bubbles on the surface of the polishing pad are preferentially supplied to areas with contact function during the relative motion process, thereby contributing to polishing. When viewed on a bubble-by-bubble basis, this phenomenon occurs in proportion to the projected diameter, so when viewed across the entire polishing pad, it is thought to correlate with the sum of the equivalent diameters of the equiarea circles of the depressions originating from the air bubbles.

[0022] In light of the above findings, the inventors aimed to improve the total equivalent diameter of the openings of the recesses originating from the roughly spherical bubbles. While this was successful in terms of improving the polishing rate, it was insufficient to maintain that polishing rate. Our investigations revealed that maintaining a high polishing rate requires a certain degree of bubble-derived recess openings on the surface with the highest bubble area ratio or in its vicinity.

[0023] This was thought to be due to the accumulation of abrasive grains in the depressions caused by air bubbles in the slurry. In other words, when there are enough openings caused by air bubbles, the abrasive grains are replaced as needed by rolling between the openings, and newly supplied abrasive grains are quickly spread out on the pad surface. Also, abrasive grains that have been used for polishing, worn, and aggregated are discharged relatively quickly from between the polishing pad and the workpiece. As a result of these actions, the polishing rate is thought to be maintained. Conversely, when there are few openings caused by air bubbles, the rolling of abrasive grains between the openings is suppressed, so deteriorated abrasive grains accumulate, and the supply of new abrasive grains is also suppressed, so the polishing rate is thought to decrease.

[0024] As a result of their investigation, the inventors have found a configuration that maintains a high polishing rate over a long period of time by achieving a high total area equivalent circle diameter and a high opening ratio through a bubble distribution that brings many abrasive grains into contact with each other and suppresses the retention of deteriorated abrasive grains.

[0025] The details of this disclosure are described below. The polishing pad of this disclosure is a polishing pad for polishing an object to be polished with free abrasive particles. In this disclosure, the polishing pad has a resin sheet having a plurality of air bubbles.

[0026] In this disclosure, from the X-ray CT measurement results of the resin sheet, multiple cross-sections are determined at depths of 4 μm from the surface on which the workpiece is to be polished to the opposite surface on the same side, parallel to the surface on which the workpiece is to be polished, and the sum of the area of ​​the openings of the multiple depressions originating from bubbles per unit area in each of the multiple cross-sections is defined as the bubble area ratio.

[0027] At this time, in the present disclosure, the resin sheet has a surface with the largest bubble area ratio among the plurality of cross-sections, and the resin sheet has a surface with the largest bubble area ratio or a surface in its vicinity that is not exposed on the surface of the resin sheet, or is exposed on the surface of the resin sheet. In the present disclosure, the surface in its vicinity refers to the surface within the range of ±200 μm in the depth direction of the surface with the largest bubble area ratio. Since the distribution of the bubbles is continuous, it is considered that the surface in the vicinity also has recesses derived from bubbles that are substantially equivalent to those on the surface with the largest bubble area ratio and exhibits substantially the same effects.

[0028] Figs. 1(a) and 1(b) schematically show the bubbles on the surface with the largest bubble area ratio or the surface in its vicinity. As shown in the figure, in the bubbles on the surface with the largest bubble area ratio or the surface 3 in its vicinity, there are an opening 2 of the recess derived from the bubble and a recess 1 derived from the bubble.

[0029] In the present disclosure, for the surface with the largest bubble area ratio, the total value of the equivalent circle diameters of the openings of the recesses derived from the plurality of bubbles per unit area is 9.0 mm / mm 2 or more and 61.0 mm / mm 2 or less, and more preferably, 9.0 mm / mm 2 or more and 13.5 mm / mm 2 or less, still more preferably, 9.0 mm / mm 2 or more and 12.0 mm / mm 2 or less, and particularly preferably 9.0 mm / mm 2 or more and 11.4 mm / mm 2 or less.

[0030] When the total value is within the above range, a high polishing rate is exhibited. When it is less than 9.0 mm / mm 2 , a sufficient polishing rate cannot be obtained. When it is 9.0 mm / mm 2 or more, it is more preferable from the viewpoint of exhibiting a high polishing rate.

[0031] Here, Figure 2 shows a diagram illustrating the equivalent diameter of an equal-area circle opening of a bubble-derived recess in this disclosure. The equivalent diameter 6 of an equal-area circle opening of a bubble-derived recess can be determined by fitting an equal-area circle 5 of an opening of a bubble-derived recess to the opening 4 of the bubble-derived recess, as in known methods.

[0032] Furthermore, in this disclosure, the surface having the maximum bubble area ratio is one in which the bubble area ratio is 55% or more and 95% or less, preferably 55% or more and 94% or less.

[0033] If the bubble area ratio is within the above range, the polishing rate will be maintained over a long period of time. If it is less than 55 area%, the initial polishing rate cannot be sufficiently maintained. If it is greater than 95 area%, the resin portion between the openings becomes fragile, the part of the polishing pad that has the function of contacting the abrasive grains does not maintain its shape during polishing, the polishing rate decreases, and the polishing rate cannot be maintained. A ratio of 70 area% or more is preferable because it better maintains the polishing rate.

[0034] In this disclosure, the surface having the maximum bubble area ratio has an average aspect ratio of the openings of the depressions originating from the plurality of bubbles of 1.00 or more and 2.00 or less, preferably 1.00 or more and 1.60 or less, and more preferably 1.00 or more and 1.50 or less.

[0035] When the average aspect ratio is within the above range, a stable polishing rate can be achieved regardless of the anisotropy of the relative motion. When the average aspect ratio is greater than 2.00, a stable polishing rate may not be achieved depending on the anisotropy of the relative motion.

[0036] The surface with the maximum bubble area ratio preferably has an average equivalent circle diameter Da of 20 μm to 200 μm, more preferably 60 μm to 160 μm, even more preferably 70 μm to 140 μm, and particularly preferably 75 μm to 133 μm. By doing so, slurry abrasive grains stored in the bubble-derived recesses can be efficiently supplied to the edge, thereby improving the polishing rate. When Da is 50 μm or larger, the slurry retention is good and the polishing rate is stabilized.

[0037] In this disclosure, the Asker A hardness of the resin sheet, measured at 25°C using an indenter with a tip diameter of 0.79 mm, is preferably 40 or higher, more preferably 60 or higher, even more preferably 70 or higher, and particularly preferably 90 or higher. This stabilizes the contact of the slurry abrasive grains, allowing for a stable and high polishing rate. When Asker A has a hardness of 60 or higher, it can exhibit a high polishing rate and stability.

[0038] [Second Embodiment] The second embodiment relates to a method for manufacturing an abrasive pad. The method for manufacturing an abrasive pad according to this disclosure is: The process includes introducing uncured resin into a coaxial centrifugal molding apparatus, forming an uncured resin layer on the inner surface of the coaxial centrifugal molding apparatus by centrifugal force, and then heating and curing the uncured resin layer to produce a resin sheet. The resin sheet has multiple air bubbles, Based on the X-ray CT measurement results of the resin sheet, multiple cross-sections are determined at depths of 4 μm, parallel to the surface on which the workpiece is being polished, and extending to the opposite surface on the same side. When the sum of the area of ​​the openings of the multiple bubble-derived recesses per unit area in each of these multiple cross-sections is defined as the bubble area ratio, The resin sheet has a surface among the multiple cross-sections that has the largest air bubble area ratio, The average aspect ratio of the openings of the recesses originating from the multiple bubbles on the surface where the bubble area ratio is maximum is 1.00 or more and 2.00 or less. On the surface where the bubble area ratio is maximum, the sum of the equivalent diameters of the openings of the multiple bubble-derived recesses per unit area is 9.0 mm / mm 2 61.0 mm / mm 2 The following: On the surface where the bubble area ratio is maximum, the bubble area ratio is 55% or more and 95% or less. It is characterized by the following: The items described in the first embodiment overlap with those described in the second embodiment, so their explanations will be omitted.

[0039] The present disclosure's method for manufacturing a polishing pad includes the steps of introducing uncured resin into a coaxial centrifugal molding apparatus, forming an uncured resin layer on the inner surface of the coaxial centrifugal molding apparatus by centrifugal force, and then heating and curing the uncured resin layer to produce a resin sheet. In this way, the bubble-derived recessed structure can be formed on the surface where the bubble area ratio is maximum.

[0040] In the method for manufacturing polishing pads according to this disclosure, the centrifugal force applied by the coaxial centrifugal molding apparatus in the process is 200 m / s 2 More than 4000m / s 2 The following conditions must be met, and it is preferable that the viscosity of the uncured resin introduced into the coaxial centrifugal molding apparatus is between 1,000 mPa·s and 20,000 mPa·s. By doing so, a bubble distribution can be formed to create the depressions originating from the bubbles on the surface of the resin sheet where the bubble area ratio is maximum.

[0041] The materials for the resin sheets used in this disclosure will be described in detail below. The material for the resin sheet is not particularly limited as long as it is a thermosetting resin, but for example, one or more of the following can be used: polyurethane resin composition, polyacrylic resin composition, polycarbonate resin composition, polyamide resin composition, polyester resin composition, polyepoxy resin composition, etc.

[0042] The polyurethane resin composition contains a structure in which compounds containing active hydrogen groups and compounds containing isocyanate groups are alternately repeated as constituent units. The compound containing the active hydrogen group is an organic compound having an active hydrogen group that can react with an isocyanate group. Specific examples of the active hydrogen group include functional groups such as a hydroxyl group, a primary amino group, a secondary amino group, and a thiol group. The compound containing the active hydrogen group may have multiple types and multiple individuals of the active hydrogen group.

[0043] Examples of compounds containing the active hydrogen group include polyol compounds and polyamine compounds. Examples of polyol compounds include linear aliphatic glycols, branched aliphatic glycols, alicyclic diols, polyfunctional polyols, polyester polyols, polyester polycarbonate polyols, polyether polyols, polycarbonate polyols, and polyfunctional polyol polymers.

[0044] Examples of linear aliphatic glycols include 1,4-benzenedimethanol, 1,4-bis(2-hydroxyethoxy)benzene, ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, and 1,9-nonanediol.

[0045] Examples of branched aliphatic glycols include neopentyl glycol, 3-methyl-1,5-pentanediol, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, and 2-methyl-1,8-octanediol. Examples of alicyclic diols include 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, and bisphenol A with water.

[0046] Examples of polyfunctional polyols include glycerin, trimethylolpropane, tributylolpropane, pentaerythritol, and sorbitol. Examples of polyester polyols include polyethylene adipate glycol, polybutylene adipate glycol, polycaprolactone polyol, and polyhexamethylene adipate glycol.

[0047] Examples of polyester polycarbonate polyols include reaction products of polyester glycols such as polycaprolactone polyols and alkylene carbonates. Another example is a reaction product obtained by reacting a reaction mixture, which is formed by reacting ethylene carbonate with a polyhydric alcohol, with an organic dicarboxylic acid.

[0048] Examples of polyether polyols include polytetramethylene ether glycol, polypropylene glycol, polyethylene glycol, and ethylene oxide-added polypropylene polyol.

[0049] Examples of polycarbonate polyols include reaction products of diols such as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, polyethylene glycol, polypropylene glycol, or polytetramethylene ether glycol with phosgene, diallyl carbonate (e.g., diphenyl carbonate), or cyclic carbonate (e.g., propylene carbonate).

[0050] Examples of polyamine compounds include 4,4'-methylenebis(2-chloroaniline) (MOCA), 4,4'-methylenedianiline, and trimethylene Examples include bis(4-aminobenzoate), 2-methyl4,6-bis(methylthio)benzene-1,3-diamine, 2-methyl4,6-bis(methylthio)-1,5-benzenediamine, 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, 1,2-bis(2-aminophenylthio)ethane, and 4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane.

[0051] Compounds containing an isocyanate group include aromatic diisocyanates, aliphatic diisocyanates, alicyclic diisocyanates, and urethane prepolymers. Examples of aromatic diisocyanates include tolylene diisocyanate (TDI), 1,5-naphthalene diisocyanate, xylylene diisocyanate, 1,3-phenylene diisocyanate, and 1,4-phenylene diisocyanate. Furthermore, examples of aromatic diisocyanates include diphenylmethane diisocyanate (MDI) and modified diphenylmethane diisocyanate (MDI).

[0052] Modified forms of diphenylmethane diisocyanate (MDI) include, for example, carbodiimide-modified forms, urethane-modified forms, allophanate-modified forms, urea-modified forms, biuret-modified forms, isocyanurate-modified forms, and oxazolidone-modified forms. Specifically, an example of such a modified form is carbodiimide-modified diphenylmethane diisocyanate (carbodiimide-modified MDI).

[0053] Examples of aliphatic diisocyanates include ethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and hexamethylene diisocyanate (HDI).

[0054] Examples of alicyclic diisocyanates include 1,4-cyclohexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, norbornane diisocyanate, and methylenebis(4,1-cyclohexylene) diisocyanate. The urethane prepolymer is a polymer formed by bonding a polyol and a polyisocyanate, and has isocyanate groups as terminal groups.

[0055] The resin sheet may contain a filler. Examples of fillers include inorganic powders such as aluminum oxide, cerium oxide, titanium oxide, germanium oxide, silicon carbide, calcium carbonate, silica, carbon black, diamond, talc, and clay; inorganic fibers such as glass fiber and carbon fiber; metal powders such as iron, copper, aluminum, and nickel; metal fibers such as iron fibers, copper fibers, and aluminum fibers; organic fibers such as polyimide fibers, Teflon® fibers, and polyester fibers; organic pigments such as azo pigments; and other materials commonly used in polymer chemistry, such as gases, fluids, and resin powders. Multiple types of these may be included simultaneously.

[0056] The filler is preferably in an amount of 0.1 parts by mass or more and 40.0 parts by mass or less per 100 parts by mass of resin. The particle size of the filler is preferably between 10 nm and 500 nm.

[0057] The resin sheet may contain a foam stabilizer. Examples of foam stabilizers include silicone-based surfactants, and one or more types can be used. Examples include "Toray Silicone SH-193," "Toray Silicone SH-192," and "Toray Silicone SH-190" manufactured by Toray Dow Corning Co., Ltd.

[0058] In addition to the materials mentioned above, stabilizers such as antioxidants, lubricants, pigments, fillers, antistatic agents, and other additives may be added to the resin sheet as needed.

[0059] Methods for forming multiple bubble-derived recesses on the surface of the resin sheet of the polishing pad where the bubble area ratio is maximum include, for example, mechanical foaming by mixing an inert gas into the uncured resin, chemical foaming by adding a foaming agent such as water, and the addition of hollow microspheres that themselves become bubbles.

[0060] Examples of inert gases used in mechanical foaming include nitrogen, oxygen, carbon dioxide, noble gases such as helium and argon, and mixtures of these gases such as air. Any known stirring device can be used without particular limitation as a stirring device for dispersing inert gas in the form of fine bubbles by mechanical foaming. Specifically, examples include homogenizers, dissolvers, twin-screw planetary mixers, and mechanical floss foamers. The shape of the stirring blades of the stirring device is also not particularly limited, but examples include whip-type stirring blades.

[0061] Examples of foaming agents used in chemical foaming include water, foaming agents mainly composed of hydrocarbons having 5 or 6 carbon atoms, organic chemical foaming agents, and halogenated hydrocarbons. Examples of such hydrocarbons include chain hydrocarbons such as butane, n-pentane, and n-hexane, and alicyclic hydrocarbons such as cyclopentane and cyclohexane.

[0062] Examples of such organic chemical blowing agents include azo compounds, nitroso compounds, and sulfonyl hydrazide compounds. Examples of azo compounds include azodicarbonamide, azobisisobutyronitrile, diazoaminobenzene, and barium azodicarboxylate.

[0063] Examples of nitroso compounds include N,N'-dinitrosopentamethylenetetramine and N,N'-dinitroso-N,N'-dimethylterephthalamide. Examples of sulfonyl hydrazide compounds include p,p'-oxybis(benzenesulfonyl hydrazide) and p-toluenesulfonyl hydrazide. Examples of halogenated hydrocarbons include methylene chloride and HFCs (hydrofluorocarbons).

[0064] Hollow microspheres can be either already expanded or unexpanded. Unexpanded microspheres are heat-expandable microspheres and can be expanded by heating. Examples of commercially available hollow microspheres include, but are not limited to, the Expancel series (product name of Akzo Nobel Corporation) and Matsumoto Microspheres (product name of Matsumoto Oil & Fat Co., Ltd.).

[0065] Alternatively, materials obtained by synthesis using conventional methods may be used. The material of the outer shell of the hollow microsphere 4A is not particularly limited, but examples include polyvinyl alcohol, polyvinylpyrrolidone, poly(meth)acrylic acid, polyacrylamide, polyethylene glycol, polyhydroxyether acrylate, maleic acid copolymer, polyethylene oxide, polyurethane, poly(meth)acrylonitrile, polyvinylidene chloride, polyvinyl chloride, and organosilicon resins, as well as copolymers obtained by combining two or more monomers that constitute these resins.

[0066] There are two main methods for manufacturing the resin sheet of the polishing pad: cutting the sheet from a bulk material and pre-forming the resin into a sheet. The latter method includes pouring uncured resin into a sheet-shaped mold, or forming the uncured resin into a sheet shape by applying external stress.

[0067] Examples of external stresses include centrifugal force. Spin coating is a method in which the rotation axis is vertical and the uncured resin is spread horizontally, while centrifugal molding is a method in which a cylindrical mold with a horizontal rotation axis rotates, and resin is poured from the rotation axis and spread on the surface of the cylindrical mold. In this disclosure, centrifugal molding is preferred.

[0068] Centrifugal molding is a method of forming a thin-walled cylindrical sheet by placing uncured resin sheet material into a cylindrical mold, rotating it at high speed to form a resin material layer on the inner surface using centrifugal force, and then heating and curing that layer. The resulting cylindrical sheet is removed from the cylindrical mold as a molded product, secondary crosslinking is performed as needed, and it is cut to the desired dimensions and shape as needed. Cutting methods include known methods such as sledgehammers, lasers, and cutters.

[0069] Figure 3 shows an example of the configuration of a centrifugal molding machine used for centrifugal molding. Specifically, the centrifugal molding machine can be configured to include a drive shaft 7 that rotates with a motor or the like, a cylindrical cup-shaped mold 8 that is attached to the tip of the drive shaft and rotatably supported, a heat source 9 such as a heater fixedly arranged on the outer circumference of the mold 8, and a hatch 10 opening in a case that covers these components.

[0070] Controlling the bubble distribution is achieved by comprehensively controlling the foaming caused by heating from the surface of the cylindrical mold of a coaxial centrifugal molding machine and the movement of bubbles due to centrifugal force, using prescriptive factors such as resin viscosity, foaming amount and timing, and control of the ratio of competitive reactions between curing and foaming, as well as operating conditions such as the centrifugal force intensity level and the duration for which centrifugal force is applied. The temperature of the cylindrical mold should be appropriately changed depending on the viscosity and foaming characteristics of the material used. For example, if you want to speed up the curing rate, you should raise the temperature, but the balance between foaming and curing has characteristics that differ for each material, so it needs to be changed according to the purpose.

[0071] Furthermore, the rotation speed of the cylindrical mold controls the effect of centrifugal force due to rotation, and this should also be adjusted appropriately based on the viscosity and foaming characteristics of the material used. For example, if you want to increase the foaming rate on the inner surface of a cylindrical mold for a resin sheet, you can increase the rotation speed to increase centrifugal force and promote the accumulation of bubbles. Also, if you want to reduce the diameter of the bubbles, you can increase the rotation speed to increase centrifugal force and promote the bursting of large-diameter bubbles. The same applies if you want to equalize the distribution of bubble diameters. It is also possible to change the rotation speed in stages depending on the curing and foaming state of the resin. The rotation time of the cylindrical mold should be appropriately controlled to the extent that the centrifugal force effect described above is exerted.

[0072] The manufacturing method for the polishing pad of this disclosure preferably includes a step of exposing the surface with the maximum bubble area ratio or a nearby surface to the surface of the resin sheet if that surface is not exposed to the surface of the resin sheet. At a minimum, the surface with the maximum bubble area ratio or a nearby surface must be exposed to the surface of the resin sheet before use as a polishing pad. Any method that exposes the cross section is acceptable. In this disclosure, the nearby surface refers to the surface within a depth range of ±200 μm of the surface with the maximum bubble area ratio.

[0073] [Third Embodiment] The third embodiment relates to a polishing method. The polishing method disclosed herein is A polishing method using a polishing pad for polishing a workpiece with free abrasive particles, The polishing pad is the polishing pad of the present disclosure, If the surface with the maximum bubble area ratio, or a surface near it, is not exposed on the surface of the resin sheet, the method includes a step of exposing the surface with the maximum bubble area ratio, or a surface near it, from the surface of the resin sheet. The items described in the first and second embodiments will be omitted from the explanation in the third embodiment as they will be repeated.

[0074] The polishing method of this disclosure is a polishing method that uses a polishing pad for polishing an object to be polished with free abrasive particles, wherein the polishing pad is the polishing pad of this disclosure. A specific example thereof will be described.

[0075] First, the polishing method of this disclosure includes a step of exposing the surface with the maximum bubble area ratio or a nearby surface to the surface of the resin sheet if that surface is not exposed to the surface of the resin sheet. When polishing, it is necessary that the surface with the maximum bubble area ratio or a nearby surface is exposed to the surface of the resin sheet. Any method that exposes the cross-section is acceptable. In this disclosure, the nearby surface refers to the surface within a depth range of ±200 μm of the surface with the maximum bubble area ratio.

[0076] Next, the workpiece to be polished is held in the holding platen of the polishing machine. Then, a polishing pad is attached to a polishing platen positioned opposite the holding platen. If the polishing pad has double-sided tape and release paper, when attaching the polishing pad to the polishing platen, the release paper is peeled off from the double-sided tape to expose the adhesive layer of the double-sided tape, and then the exposed adhesive layer is brought into contact with the polishing platen and pressed down. Then, a polishing slurry containing abrasive grains is supplied between the workpiece and the polishing pad as needed, and the workpiece is pressed towards the polishing pad with a predetermined polishing pressure while the polishing platen or holding platen is rotated, thereby polishing the workpiece with free abrasive grains.

[0077] The polishing slurry is not particularly limited and may be one used in conventional chemical mechanical polishing. As for the abrasive grains, general types can be used depending on the material to be polished, such as ceria, silica, alumina, manganese oxide, diamond, and organic-inorganic composite abrasive grains. The abrasive grains may be used individually or in combination of two or more types.

[0078] [Measurement and calculation methods for each physical property] The measurement and calculation methods for various physical properties of the polishing pad and material are described below. <Method for measuring the average aspect ratio> • Acquisition of shape data A strip-shaped section measuring 2 cm wide and 5 cm long (section 11 of the resin sheet for X-ray CT imaging) was prepared from the resin sheet of the polishing pad, and it was set in an X-ray CT scanner (TXS-32300FDHS manufactured by Toshiba IT Control Systems Co., Ltd.) and X-ray CT measurements were performed. The measurement conditions are shown below. X-ray tube voltage [kV]: 75.000 X-ray tube voltage [mA]: 0.053 Data mode: CONE FC function: Laks Scan Mode: FULL Views: 2000 Slice distance: 0.004 Integral: 1

[0079] • Definition of measuring surface The shape data obtained for the X-ray CT imaging area 12 in the above measurement was analyzed using VGStudio Max 2.1, image processing software manufactured by Visual Science Volume Graphics Co., Ltd. A 4.0 mm × 4.0 mm area on the surface of the resin sheet with the largest surface area was sliced ​​every 4.0 μm in the depth direction to obtain a measurement surface 13 that sliced ​​the X-ray CT imaging area. An overview of the method for defining the measurement surface up to this point is shown in Figure 4.

[0080] Each obtained cross-section was classified into bubble-derived depressions and resin portions by binarization processing using contrast adjustment. For bubble-derived depressions of 2 μm or larger (openings 14 of bubble-derived depressions on the measurement surface), the total area of ​​the openings was calculated and divided by the area of ​​the entire region to determine the ratio.

[0081] When the surface with the largest area ratio of the openings of the depressions caused by air bubbles, or a surface near it, was used as the measurement surface, the measurement surface was determined from the above data. Furthermore, when the outermost surface of the resin sheet was used as the measurement surface, the sheet was sliced ​​from the surface side, and the measurement surface was defined as the cut surface where the void portion, which accounted for 10% or more of the entire measurement surface, was eliminated, when the entire measurement surface was considered to be 100%.

[0082] • Measurement of average aspect ratio The 4.0mm x 4.0mm measurement surface data obtained from the above measurements was further analyzed using VGStudio Max 2.1 image processing software from Visual Science Volume Graphics Co., Ltd. The circumferential portion of bubble-derived depressions of 2 μm or larger on the surface with the largest area ratio of bubble-derived depressions or its vicinity was extracted, and the average aspect ratio was calculated. The average of at least 50 bubble-derived depressions was used. If there were fewer than 50 bubble-derived depressions in the measurement surface, multiple samples were measured, and the average of 50 or more was calculated.

[0083] <Method for measuring the equivalent diameter of an equal-area circle> • Acquisition of shape data Similar to the measurement of the average aspect ratio, X-ray CT measurements were performed on the resin sheet to obtain measurement surface data of 4.0 mm x 4.0 mm.

[0084] • Measurement of the equivalent diameter of an area circle The 4.0mm x 4.0mm measurement surface data obtained from the above measurements was analyzed using ImageJ (Rasband, WSUS National Institutes of Health, Bethesda, Maryland, USA). By performing binarization processing with contrast adjustment, the surface with the largest area ratio of bubble-derived depressions or its vicinity was classified into bubble-derived depressions and resin portions. For bubble-derived depressions of 2μm or larger on the 4.0mm x 4.0mm measurement surface, the equivalent diameter of an equal-area circle was calculated, and the average value was calculated. The average of at least 50 bubble-derived depressions was used. If there were fewer than 50 bubble-derived depressions on the measurement surface, multiple samples were measured, and the average value of 50 or more was calculated.

[0085] <Method for calculating the ratio of the total area of ​​openings> • Acquisition of shape data Similar to the measurement of the average aspect ratio, X-ray CT measurements were performed on the resin sheet to obtain data for a 4.0 mm x 4.0 mm measurement surface.

[0086] • Calculation of the ratio of the total area of ​​openings The data from the 4.0 mm × 4.0 mm measurement surface obtained from the above measurements was analyzed using VGStudio Max 2.1, image processing software manufactured by Visual Science Volume Graphics Co., Ltd. For the 4.0 mm × 4.0 mm measurement surface data, the total area of ​​the openings for depressions caused by air bubbles of 2 μm or larger was calculated, and the ratio was calculated by dividing this by the total area of ​​the 4.0 mm × 4.0 mm measurement surface.

[0087] <Method for measuring the Asker A hardness of the resin sheet at 25°C> To eliminate the influence of the sheet stand on the measurement values, the resin sheets, laminated to a thickness of 6 mm or more, were left standing for 16 hours in a 25°C environment with a humidity of 50% ± 5%. Then, they were measured five times using a Type A durometer compliant with JIS K 6253 (Asker Type A, manufactured by Polymer Instruments Co., Ltd.), and the average value was taken as the Asker A hardness of the resin sheet.

[0088] <Method for measuring resin viscosity> Viscosity was measured after 60 seconds using a HAAKE VP-500. The measurement equipment and conditions are as follows. Viscometer: Rotary viscometer Viscotester VT550 (HAAKE Corporation) Sensor system: NV cup / NV rotor Rotation speed: 8.3s-1 (500rpm) Circulating constant temperature bath: Open bath circulator DC5-K20 (manufactured by HAAKE) Set temperature: 70℃

[0089] <Evaluation method for initial polishing rate and polishing rate changes> The surface of the fabricated polishing pad 1 was subjected to so-called XY groove processing (lattice-like groove processing) with a width of 2.0 mm, a pitch of 15 mm, and a depth of 0.5 mm, and was mounted on a CMP polishing machine (NF-300HP manufactured by Nanofactor Co., Ltd.).

[0090] Next, the platen rotation speed is 60 rpm, the head rotation speed is 61 rpm, and the polishing pressure is 70 g / cm². 2Under these conditions, a #100 diamond plate was attached to the head, and the pads were initially dressed for 1 minute. No further dressing was performed throughout the evaluation.

[0091] Next, the platen rotation speed is 60 rpm, the head rotation speed is 61 rpm, and the polishing pressure is 140 g / cm². 2 Under these conditions, a wafer with a 5000 Å SiO2 film formed on the surface of a 4-inch diameter single-crystal silicon (100) surface was polished for 2 minutes, 20 minutes, and 40 minutes while supplying silica (SiO2) slurry (manufactured by Fujimi Incorporated) at a rate of 100 ml / min, and the polishing rate was measured.

[0092] In this disclosure, "excellent maintenance of the polishing rate" means that the polishing rate does not decrease significantly with polishing time, for example, that the difference between the polishing rate after 2 minutes of polishing and the polishing rate after 40 minutes of polishing is relatively small. [Examples]

[0093] The present disclosure will be described in detail below with reference to examples, but these examples are not intended to limit the present disclosure in any way. In the following formulations, parts are by mass unless otherwise specified. <Example 1> 237 parts by mass of 2,4-TDI (tolylene diisocyanate) was reacted with 412 parts by mass of PTMG (polytetramethylene ether glycol) with a number average molecular weight of approximately 1000 and 40 parts by mass of diethylene glycol. The mixture was degassed under heating and reduced pressure to obtain a prepolymer. This prepolymer had an isocyanate content of 9.1%.

[0094] An uncured resin solution was obtained by mixing 55.0 parts by mass of prepolymer, 45.0 parts by mass of diethyltoluenediamine (DETDA), 5.0 parts by mass of water, 0.006 parts by mass of Toyocat® ET (manufactured by Tosoh Corporation), and 2.0 parts by mass of silicone-based foam stabilizer SH-193.

[0095] 340 g of the uncured resin solution was poured into a cylindrical mold with a diameter of 450 mm and a depth of 320 mm in a centrifugal molding machine that had a silicone rubber release layer pre-formed on it, was heated to 110°C, and rotated at 1200 rpm. From the moment the pouring was completed, the machine was maintained at 1200 rpm for 30 minutes to heat-cur the solution. After that, the mold was demolded to obtain a resin sheet 1 with a thickness of 1.50 mm.

[0096] On the side of the obtained resin sheet 1 opposite to the side with the maximum air bubble area ratio or a nearby side, a double-sided tape made of PET with adhesive layers (material: acrylic resin) on both sides and release paper on one side was attached to the adhesive layer opposite to the release paper. The tape was then cut into a circular shape with a diameter of 300 mm to obtain a polishing pad 1. The formulation and manufacturing conditions of the obtained polishing pad 1 are shown in Table 1. The physical properties of the obtained polishing pad 1 are shown in Table 2.

[0097] [Table 1]

[0098] [Table 2]

[0099] Table 3 shows the results of the evaluation of the initial polishing rate and the progression of the polishing rate.

[0100] [Table 3]

[0101] <Examples 2-9> Polishing pads 2 to 9 were obtained in the same manner as in Example 1, except that the formulation, the rotation conditions of the cylindrical mold, and the rotation time were changed as shown in Table 2. The physical properties of the obtained polishing pads 2 to 9 are shown in Table 2. The evaluation results for the polishing pads 2-9 obtained are shown in Table 3.

[0102] <Comparative Examples 1-3> Polishing pads 10 to 12 were obtained in the same manner as in Example 1, except that the formulation, the rotation conditions of the cylindrical mold, and the rotation time were changed as shown in Table 3. The physical properties of the obtained polishing pads 10 to 12 are shown in Table 2. The evaluation results for the obtained polishing pads 10-12 are shown in Table 3.

[0103] Examples 1 to 9 showed good progress in the initial polishing rate and the progression of the polishing rate because the average aspect ratio of the openings of the depressions caused by air bubbles, the sum of the equivalent diameters of the equal-area circles, and the sum of the opening areas all met the requirements of claim 1. Example 1 was particularly good.

[0104] Comparative Examples 1 to 3 did not satisfy the requirements of Claim 1 in terms of the average aspect ratio of the openings of the depressions caused by air bubbles, the sum of the equivalent diameters of the equal-area circles, and the sum of the opening areas, and showed low values ​​in the initial polishing rate and the progression of the polishing rate.

[0105] This embodiment includes the following configurations and methods. (Composition 1) A polishing pad for polishing a workpiece with free abrasive particles, The polishing pad has a resin sheet having multiple air bubbles, Based on the X-ray CT measurement results of the resin sheet, multiple cross-sections are determined at depths of 4 μm from the surface on which the workpiece is being polished to the opposite surface on the same side, parallel to the surface on which the workpiece is being polished. When the sum of the area of ​​the openings of the multiple depressions originating from bubbles per unit area in each of these multiple cross-sections is defined as the bubble area ratio, The resin sheet has a surface among the multiple cross-sections that has the largest air bubble area ratio, The surface with the maximum bubble area ratio is one in which the average aspect ratio of the openings of the recesses originating from the multiple bubbles is 1.00 or more and 2.00 or less. The surface with the highest bubble area ratio is one where the sum of the equivalent diameters of the openings of the multiple bubble-derived recesses per unit area is 9.0 mm / mm 2 61.0 mm / mm 2 The following: The surface with the maximum bubble area ratio is one where the bubble area ratio is between 55% and 95%. A polishing pad characterized by the following features. (Configuration 2) The polishing pad according to configuration 1, wherein the surface with the maximum bubble area ratio has an average equivalent circle diameter Da of the openings of the multiple bubble-derived recesses that is 20 μm or more and 200 μm or less. (Composition 3) The polishing pad according to configuration 1 or 2, wherein the Asker A hardness of the resin sheet, measured at 25°C using an indenter with a tip diameter of 0.79 mm, is 40 or higher. (Method 1) A polishing method using a polishing pad for polishing a workpiece with free abrasive particles, The polishing pad is the polishing pad described in any one of configurations 1 to 3. A polishing method comprising the step of exposing the surface with the maximum bubble area ratio or a nearby surface to the surface of the resin sheet if that surface is not exposed to the surface of the resin sheet. (Method 2) The process includes introducing uncured resin into a coaxial centrifugal molding apparatus, forming an uncured resin layer on the inner surface of the coaxial centrifugal molding apparatus by centrifugal force, and then heating and curing the uncured resin layer to produce a resin sheet. The resin sheet has multiple air bubbles, Based on the X-ray CT measurement results of the resin sheet, multiple cross-sections are determined at depths of 4 μm, parallel to the surface on which the workpiece is being polished, and extending to the opposite surface on the same side. When the sum of the area of ​​the openings of the multiple bubble-derived recesses per unit area in each of these multiple cross-sections is defined as the bubble area ratio, The resin sheet has a surface among the multiple cross-sections that has the largest air bubble area ratio, The average aspect ratio of the openings of the recesses originating from the multiple bubbles on the surface where the bubble area ratio is maximum is 1.00 or more and 2.00 or less. On the surface where the bubble area ratio is maximum, the sum of the equivalent diameters of the openings of the multiple bubble-derived recesses per unit area is 9.0 mm / mm2 61.0 mm / mm 2 The following: On the surface where the bubble area ratio is maximum, the bubble area ratio is 55% or more and 95% or less. A method for manufacturing an abrasive pad, characterized by the above. (Method 3) The aforementioned centrifugal force is 200 m / s 2 More than 4000m / s 2 The following: The method for manufacturing an abrasive pad according to Method 2, wherein the viscosity of the uncured resin introduced is 1,000 mPa·s or more and 20,000 mPa·s or less. (Method 4) A method for manufacturing an abrasive pad according to method 2 or 3, comprising the step of exposing the surface with the maximum bubble area ratio or a nearby surface to the surface of the resin sheet if the surface with the maximum bubble area ratio or a nearby surface is not exposed to the surface of the resin sheet. [Explanation of Symbols]

[0106] 1. Depression caused by air bubbles 2. Opening of a recess caused by an air bubble 3. The surface with the maximum bubble area ratio, or a surface near it. 4. Opening of recesses caused by air bubbles 5. Equi-area circles of openings in depressions caused by air bubbles. 6. Equivalent diameter of an equal-area circle at the opening of a recess caused by air bubbles. 7 Drive shaft 8. Cylindrical mold 9 Heat source 10 hatches 11 Sections of resin sheets for X-ray CT imaging 12 X-ray CT imaging area 13. Measurement surface obtained by slicing the X-ray CT imaging area. 14 Opening of recesses on the measurement surface caused by air bubbles

Claims

1. A polishing pad for polishing a workpiece with free abrasive particles, The polishing pad has a resin sheet having multiple air bubbles, From the X-ray CT measurement results of the resin sheet, multiple cross-sections are determined at depths of 4 μm from the surface on which the workpiece is being polished to the opposite surface on the same side, parallel to the surface on which the workpiece is being polished. When the sum of the area of ​​the openings of the multiple depressions caused by bubbles per unit area in each of these multiple cross-sections is defined as the bubble area ratio, The resin sheet has a surface among the multiple cross-sections that has the largest air bubble area ratio, The surface with the maximum bubble area ratio is one in which the average aspect ratio of the openings of the recesses originating from the multiple bubbles is 1.00 or more and 2.00 or less. The surface with the highest bubble area ratio is one where the sum of the equivalent diameters of the openings of the multiple bubble-derived recesses per unit area is 9.0 mm / mm. ２ The above is 61.0 mm / mm ２ The following: The surface with the maximum bubble area ratio is one where the bubble area ratio is between 55% and 95%. A polishing pad characterized by the following features.

2. The polishing pad according to claim 1, wherein the surface with the maximum bubble area ratio has an average equivalent circle diameter Da of the openings of the recesses originating from the plurality of bubbles that is 20 μm or more and 200 μm or less.

3. The polishing pad according to claim 1, wherein the Asker A hardness of the resin sheet is 40 or higher at 25°C.

4. A polishing method using a polishing pad for polishing a workpiece with free abrasive particles, The polishing pad is the polishing pad described in any one of claims 1 to 3, A polishing method comprising the step of exposing the surface with the maximum bubble area ratio or a nearby surface to the surface of the resin sheet if that surface is not exposed to the surface of the resin sheet.

5. The process includes introducing uncured resin into a coaxial centrifugal molding apparatus, forming an uncured resin layer on the inner surface of the coaxial centrifugal molding apparatus by centrifugal force, and then heating and curing the uncured resin layer to produce a resin sheet. The resin sheet has multiple air bubbles, Based on the X-ray CT measurement results of the resin sheet, multiple cross-sections are determined at depths of 4 μm, parallel to the surface on which the workpiece is being polished, and extending to the opposite surface on the same side. When the sum of the area of ​​the openings of the multiple bubble-derived recesses per unit area in each of these multiple cross-sections is defined as the bubble area ratio, The resin sheet has a surface among the multiple cross-sections that has the largest air bubble area ratio, The average aspect ratio of the openings of the depressions originating from the multiple bubbles on the surface where the bubble area ratio is maximum is 1.00 or more and 2.00 or less. On the surface where the bubble area ratio is maximum, the sum of the equivalent diameters of the openings of the multiple bubble-derived recesses per unit area is 9.0 mm / mm ２ The above is 61.0 mm / mm ２ The following: On the surface where the bubble area ratio is maximum, the bubble area ratio is 55% or more and 95% or less. A method for manufacturing an abrasive pad, characterized by the above.

6. The aforementioned centrifugal force is 200 m / s ２ More than 4000m / s ２ The following: The method for manufacturing an abrasive pad according to claim 5, wherein the viscosity of the uncured resin introduced is 1,000 mPa·s or more and 20,000 mPa·s or less.

7. A method for manufacturing an abrasive pad according to claim 5, comprising the step of exposing the surface with the maximum bubble area ratio or a surface near thereon to the surface of the resin sheet if that surface is not exposed to the surface of the resin sheet.

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