Polishing pad, method for producing polishing pad, and method for polishing surface of optical material or semiconductor material

Abstract

The purpose of the present invention is to provide a polishing pad capable of inhibiting the occurrence of scratches, a method for producing the polishing pad, and a method for polishing the surface of an optical material or semiconductor material using the polishing pad.　The polishing pad has a polishing layer containing microspheres, wherein: open holes are present on the surface of the polishing layer; on a distribution curve of the open-hole diameter obtained by using, as a reference, the number fraction thereof on the surface of the polishing layer, the peak top is present in a range in which the open-hole diameter is 15 μm or less; and the number fraction of the open holes at the peak top is 15% or more.

Description

Polishing pad, method for manufacturing a polishing pad, and method for polishing the surface of an optical or semiconductor material

[0001] The present invention relates to a polishing pad, a method for manufacturing a polishing pad, and a method for polishing the surface of an optical material or a semiconductor material. The polishing pad of the present invention is used for polishing optical materials, semiconductor wafers, semiconductor devices, hard disk substrates, etc., and is particularly suitable for polishing devices in which an oxide layer, a metal layer, etc. is formed on a semiconductor wafer.

[0002] The polishing pad used for polishing semiconductor devices and the like has a polishing layer made of synthetic resin such as polyurethane, and voids are formed inside the polishing layer.The voids are open on the surface of the polishing layer, and during polishing, the abrasive grains contained in the polishing slurry are held in the open pores on the surface of the polishing layer, thereby polishing the object to be polished.As one of the methods for forming voids inside the polishing layer, a method of mixing microspheres in resin is known, and in recent years, in order to achieve more precise polishing, the reduction in the diameter and uniformity of the voids (openings) have been studied.

[0003] Patent Document 1 discloses a polishing pad using unexpanded microspheres with an average particle size of 20 to 30 μm.

[0004] JP 2010-274362 A

[0005] However, the polishing pad using the microspheres described in Patent Document 1 has many openings with a diameter of about 150 μm on the surface of the polishing layer, and polishing debris and the like may remain in these openings, causing scratches on the workpiece to be polished. As described above, there is a demand for a polishing pad that can suppress the generation of scratches on the workpiece to be polished.

[0006] The present invention has been made in consideration of the above problems, and aims to provide a polishing pad that can suppress the occurrence of scratches on the object to be polished, a method for manufacturing such a polishing pad, and a method for polishing the surface of an optical material or a semiconductor material using such a polishing pad. Another aim of the present invention is to provide a polishing pad that can suppress the occurrence of scratches on the object to be polished and exhibits a high removal rate, a method for manufacturing such a polishing pad, and a method for polishing the surface of an optical material or a semiconductor material using such a polishing pad.

[0007] As a result of intensive research aimed at solving the above-mentioned problems, the inventors have discovered that the above-mentioned problems can be solved by ensuring that the pores present on the surface of the polishing layer satisfy certain conditions, and have thus completed the present invention. Specific aspects of the present invention are as follows.

[0008] [1] A polishing pad having a polishing layer containing microspheres, wherein pores are present on the surface of the polishing layer, and a pore size distribution curve based on the number fraction on the surface of the polishing layer has a peak top in a region of pore size 15 μm or less, and the number fraction of the pores at the peak top is 15% or more. [2] A polishing pad having a polishing layer containing microspheres, wherein pores are present on the surface of the polishing layer, and a pore size distribution curve based on the pore perimeter x number fraction on the surface of the polishing layer has a peak top in a region of pore size 15 μm or less. [3] The polishing pad according to [1], wherein the number fraction of the pores at the peak top is 17% or more. [4] The polishing pad according to any one of [1] to [3], wherein the average pore size on the surface of the polishing layer is 5 to 20 μm. [5] The number of the pores per unit area on the surface of the polishing layer is 1,200 to 2,500 / mm ２[6] The polishing pad according to any one of [1] to [5], wherein the surface porosity of the polishing layer is 10 to 50%. [7] The polishing pad according to any one of [1] to [6], wherein the polishing layer further contains a polyurethane resin. [8] The polishing pad according to any one of [1] to [7], wherein the polyurethane resin is a cured product of a curable resin composition containing an isocyanate-terminated urethane prepolymer, a curing agent, and heat-expandable microspheres. [9] A method for producing a polishing pad having a polishing layer containing microspheres, comprising: (a) preparing a curable resin composition containing heat-expandable microspheres having an average particle size (D50) of 1 to 20 μm; and (b) heating the curable resin composition under heating conditions including a temperature increase rate of 1.5 to 7.5°C / min, to cure the curable resin composition to form the polishing layer and expand the heat-expandable microspheres to form the microspheres.

[10] The method for producing a polishing pad according to [9], wherein the polishing pad is the polishing pad according to any one of [1] to [8].

[11] A method for polishing the surface of an optical material or a semiconductor material, comprising the step of polishing the surface of the optical material or the semiconductor material using the polishing pad according to any one of [1] to [8].

[12] The polishing pad according to any one of [2] to [8], wherein a pore size distribution curve based on the number fraction on the surface of the polishing layer has a peak top in a region of pore sizes of 15 μm or less, and the number fraction of the pores at the peak top is 15% or more.

[13] The polishing pad according to any one of [1] to [8] and

[12] , wherein a pore size distribution curve based on the number fraction on the surface of the polishing layer has a total number fraction (integral value) of 55 to 90% of the pores present in a region of pore sizes of 15 μm or less.

[14] The polishing pad according to any one of [1] to [8],

[12] , and

[13] , wherein the total number fraction (integral value) of pores present in an area where the pore diameter is 20 μm or less in a distribution curve of pore diameters based on the number fraction on the surface of the polishing layer is 80 to 90%.

[15] The polishing pad according to any one of [1] to [8] and

[12] to

[14] , wherein in a pore diameter distribution curve on the surface of the polishing layer based on the pore perimeter x number fraction, there is a peak top in a region of pore diameters of 15 μm or less, and the pore perimeter x number fraction at the peak top is 12 μm·% or more.

[16] The polishing pad according to any one of [1] to [8] and

[12] to

[15] , wherein in a pore diameter distribution curve on the surface of the polishing layer based on the pore perimeter x number fraction, the total value (integral value) of the pore perimeter x number fraction of pores present in a region of pore diameters of 15 μm or less is 40 to 75 μm·%.

[17] The polishing pad according to any one of [1] to [8] and

[12] to

[16] , wherein in a distribution curve of opening diameters on the surface of the polishing layer based on the opening diameter x number fraction, the total value (integral value) of opening diameter x number fraction of openings present in a region where the opening diameter is 20 μm or less is 60 to 90 μm·%.

[18] The method for manufacturing a polishing pad according to [9], wherein the polishing pad is the polishing pad according to any one of

[12] to

[17] .

[19] A method for polishing the surface of an optical material or a semiconductor material, the method comprising the step of polishing the surface of an optical material or a semiconductor material using the polishing pad according to any one of

[12] to

[17] .

[0009] (Definitions) In this specification, when a numerical range is expressed using "X to Y," the range includes the numerical values ​​X and Y at both ends. In this specification, a "peak" in a pore size distribution curve refers to a mountain-shaped portion when viewed across the entire distribution curve. In a distribution curve, a large mountain-shaped portion may contain a small mountain-shaped portion, but such a small mountain-shaped portion is not included in the "peak" in this specification. In this specification, a "peak top" in a pore size distribution curve refers to the apex of the peak. In this specification, the "number fraction" of pores in a pore size distribution curve means the ratio (%) of the number of pores having a corresponding pore size (when the pore size is expressed as a numerical range, the total number of pores falling within that numerical range) to the total number of pores. In this specification, the "pore perimeter" in a pore size distribution curve refers to the length of the circumference of a circle when the pores are considered to be circles, and can be calculated by multiplying the diameter of the corresponding pore (pore diameter) by pi.

[0010] The polishing pad of the present invention can suppress the occurrence of scratches on the object to be polished.

[0011] FIG. 1 is a graph showing the heating conditions used to form the polishing layers in Examples 1 to 3 and Comparative Examples 1 and 2. FIG. 2 is a graph showing the distribution curve of pore size versus number fraction on the surface of the polishing layer in Example 1. FIG. 3 is a graph showing the distribution curve of pore size versus number fraction on the surface of the polishing layer in Example 2. FIG. 4 is a graph showing the distribution curve of pore size versus number fraction on the surface of the polishing layer in Example 3. FIG. 5 is a graph showing the distribution curve of pore size versus number fraction on the surface of the polishing layer in Comparative Example 1. FIG. 6 is a graph showing the distribution curve of pore size versus number fraction on the surface of the polishing layer in Comparative Example 2. FIG. 7 is a graph showing the distribution curve of pore size versus pore circumference × number fraction on the surface of the polishing layer in Example 1. FIG. 8 is a graph showing the distribution curve of pore size versus pore circumference × number fraction on the surface of the polishing layer in Example 2. FIG. 9 is a graph showing the distribution curve of pore size versus pore circumference × number fraction on the surface of the polishing layer in Example 3. Fig. 10 is a graph showing the distribution curve of opening diameter - opening perimeter x number fraction on the surface of the polishing layer of Comparative Example 1. Fig. 11 is a graph showing the distribution curve of opening diameter - opening perimeter x number fraction on the surface of the polishing layer of Comparative Example 2.

[0012] (Function) The present inventors have conducted extensive research into the relationship between the pores on the surface of the polishing layer and scratches on the object to be polished, and as a result, they have unexpectedly found that, in the distribution curve of pore diameters based on the number fraction, there is a peak top in the region of pore diameters of 15 μm or less, and the number fraction of the pores at this peak top is 15% or more, and / or, in the distribution curve of pore diameters based on the perimeter of pores x number fraction, there is a peak top in the region of pore diameters of 15 μm or less, and scratches on the object to be polished can be suppressed.The details of why such characteristics are obtained are not clear, but it is presumed as follows.

[0013] The inventors have considered that scratches on the polished object are caused by the edges of the pores (the boundary between the hollow (pore) portion where no components of the polishing layer are present and the solid portion where components of the polishing layer are present). In this case, it is thought that large-diameter pores present on the surface of the polishing layer are more likely to cause scratches due to their long edges, while small-diameter pores are less likely to cause scratches due to their short edges. Therefore, it is thought that scratches can be suppressed by increasing the proportion of small-diameter pores in all pores. In the distribution curve of pore diameters based on the number fraction on the surface of the polishing layer, the region of pore diameters of 15 μm or less can be said to represent the region corresponding to small-diameter pores. A peak top exists in this region, and it can be inferred that scratches can be suppressed because the number fraction of pores at this peak top is relatively high, at 15% or more. Furthermore, for pores having a specific diameter, the perimeter of the pores (the length of the circumference when the pores are considered as circles) can be multiplied by the number fraction of the pores, and the edge length of the pores having a specific diameter can be weighted and expressed. By creating a distribution curve of aperture diameters using this aperture perimeter x number fraction, the relationship between scratches and aperture edges can be more directly expressed. In the aperture diameter distribution curve based on aperture perimeter x number fraction, the presence of a peak top in the region of aperture diameters of 15 μm or less can be said to mean that there are a relatively large number of apertures with short edge lengths, and it can be inferred that scratches can be suppressed as a result.

[0014] The polishing pad of the present invention, the method for producing the polishing pad, and the method for polishing the surface of an optical material or a semiconductor material will be described below.

[0015] 1. Polishing Pad <First Embodiment> A polishing pad according to a first embodiment of the present invention is a polishing pad having a polishing layer containing microspheres, wherein open pores are present on the surface of the polishing layer, and a distribution curve of open pore diameters based on the number fraction on the surface of the polishing layer has a peak top in a region of open pore diameters of 15 μm or less, and the number fraction of the open pores at the peak top is 15% or more.

[0016] (1) Microspheres A foam can be formed by mixing microspheres with the components (such as polyurethane resin) that make up the polishing layer. The microspheres are not particularly limited, but examples include unexpanded heat-expandable microspheres consisting of a thermoplastic resin shell (polymer shell) and a low-boiling-point hydrocarbon encapsulated in the shell, spheres obtained by heating and expanding the unexpanded heat-expandable microspheres, and combinations thereof.

[0017] The average particle size (D50, median diameter) of the unexpanded heat-expandable microspheres is not particularly limited, but is preferably 1 to 20 μm, more preferably 3 to 15 μm, and most preferably 6 to 10 μm. When the average particle size is within the above range, the average pore size of the surface of the polishing layer remains 20 μm or less even after the heat-expandable microspheres are expanded, enabling more precise polishing of the workpiece. The average particle size (D50, median diameter) can be measured using a laser diffraction particle size analyzer (e.g., Mastersizer 2000, manufactured by Spectris Co., Ltd.).

[0018] The expansion starting temperature of the unexpanded heat-expandable microspheres is not particularly limited, but from the viewpoint of the heat of reaction due to the polymerization reaction of the prepolymer, it is preferably 50 to 200° C., more preferably 80 to 150° C., and most preferably 90 to 120° C. The maximum expansion temperature of the unexpanded heat-expandable microspheres is not particularly limited, but from the viewpoint of the heat of reaction due to the polymerization reaction of the prepolymer, it is preferably 90 to 200° C., more preferably 110 to 170° C., and most preferably 120 to 150° C.

[0019] Examples of polymers that can be used to form the polymer shell include thermoplastic resins such as polyvinyl alcohol, polyvinylpyrrolidone, poly(meth)acrylic acid, polyacrylamide, polyethylene glycol, polyhydroxyether acrylate, maleic acid copolymers, polyethylene oxide, polyurethane, poly(meth)acrylonitrile, polyvinylidene chloride, polyvinyl chloride, and organic silicone resins, as well as copolymers of two or more of the monomers that constitute these resins (e.g., acrylonitrile-vinylidene chloride copolymer, acrylonitrile-methyl methacrylate copolymer, vinyl chloride-ethylene copolymer, etc.). Of these, acrylonitrile-methyl methacrylate copolymer is preferred in terms of achieving the effects of the present invention. Examples of low-boiling hydrocarbons that can be used within the polymer shell include isobutane, pentane, isopentane, petroleum ether, and combinations of two or more of these.

[0020] The content of the microspheres in the entire polishing layer or the entire cured product of the curable resin composition described below is not particularly limited, but is preferably 0.1 to 10.0 wt %, more preferably 1.0 to 5.0 wt %, and most preferably 2.0 to 4.0 wt %. When the content of the microspheres is within the above numerical range, the density of the polishing layer is made uniform.

[0021] (2) Pores In the first embodiment of the present invention, the characteristics of the pores are defined based on a distribution curve of pore diameters based on the number fraction on the surface of the polishing layer. As the distribution curve of pore diameters based on the number fraction on the surface of the polishing layer, a distribution curve can be used in which the horizontal axis is the pore diameter and the vertical axis is the ratio of the number of each pore to the total number of pores (number fraction). The distribution curve can be obtained based on the procedures and conditions described in (2) of the (Evaluation Method) in the Examples below.

[0022] In the distribution curve of the first embodiment, the upper limit of the pore size in the region where the peak top exists is 15 μm or less, and can also be 14 μm or less, 13 μm or less, or 12 μm or less. The lower limit of the pore size in the region where the peak top exists is not particularly limited, but can also be 6 μm or more, 7 μm or more, or 8 μm or more. The above upper and lower limits of the pore size in the region where the peak top exists can be combined in any way.

[0023] In the distribution curve of the first embodiment, the lower limit of the number fraction of the pores at the peak top is 15% or more, and can also be 16% or more, 17% or more, 18% or more, or 19% or more. The upper limit of the number fraction of the pores at the peak top is not particularly limited, but can also be 30% or less or 25% or less. The upper and lower limits of the number fraction of the pores at the peak top can be combined in any way.

[0024] In the polishing pad of the first embodiment of the present invention, the occurrence of scratches on the workpiece can be suppressed by setting the pore size in the region where the peak top exists in the distribution curve to 15 μm or less and setting the number fraction of the pores at the peak top to 15% or more. The pores on the surface of the polishing layer having such characteristics can be formed by using specific unexpanded heat-expandable microspheres and expanding them under specific heating conditions, as in Examples 1 to 3 described below.

[0025] In the distribution curve of the first embodiment, the number of peak tops is not particularly limited, but is preferably 1. In the distribution curve of the first embodiment, the total number fraction (integral value) of pores present in the region where the pore diameter is 15 μm or less is not particularly limited, but can be 55 to 90%, 60 to 85%, or 70 to 80%. Furthermore, the total number fraction (integral value) of pores present in the region where the pore diameter is 20 μm or less is not particularly limited, but can be 75 to 95%, or 80 to 90%.

[0026] In the first embodiment, the average pore size on the surface of the polishing layer is not particularly limited, but is preferably 5 to 20 μm, more preferably 8 to 18 μm, and most preferably 10 to 15 μm. By having the average pore size within the above numerical range, the workpiece can be polished more precisely.

[0027] In the first embodiment, the number of openings per unit area on the surface of the polishing layer is not particularly limited, but is preferably 1200 to 2500 openings / mm ２ is preferably 1500 to 2500 pieces / mm ２ More preferably, 1600 to 2000 pieces / mm ２ is most preferred.

[0028] In the first embodiment, the porosity of the surface of the polishing layer is not particularly limited, but is preferably 10 to 50%, more preferably 15 to 45%, and most preferably 20 to 40%. When the porosity is within the above range, the slurry retention is good and the workpiece can be polished stably. Here, the porosity of the surface of the polishing layer means the ratio (%) of the total area of ​​the pores present on the surface to the area of ​​the surface of the polishing layer.

[0029] The average pore size, number of pores per unit area, and pore rate on the surface of the above-mentioned polishing layer can be measured based on the procedures and conditions described in item (2) of (Evaluation Method) in the [Examples] below.

[0030] In the first embodiment, the density of the polishing layer is not particularly limited, but is preferably 0.60 to 0.95 g / cm ３ is preferred, and 0.65 to 0.90 g / cm ３ More preferably, 0.70 to 0.85 g / cm ３is most preferable. When the density is within the above numerical range, the occurrence of scratches due to polishing by-products (polishing debris) can be suppressed. In the first embodiment, the Shore D hardness of the polishing layer is not particularly limited, but is preferably 35 to 75, more preferably 40 to 70, and most preferably 45 to 65. If the Shore D hardness is too low, it becomes difficult to flatten minor irregularities. If the Shore D hardness is too high, scratches may occur on the polished object. The density and Shore D hardness of the polishing layer can be measured based on the procedures and conditions described in item (1) of (Evaluation Method) in [Examples] below.

[0031] The polishing pad of the present invention has a polishing layer. The polishing layer is positioned in direct contact with the material to be polished, and the other parts of the polishing pad may be made of a material for supporting the polishing pad, for example, a highly elastic material such as rubber. Depending on the rigidity of the polishing pad, the polishing layer can be used as a polishing pad.

[0032] The polishing pad of the present invention has no significant difference in shape from a general polishing pad, except that it can suppress the occurrence of scratches, and can be used in the same way as a general polishing pad.For example, the polishing pad can be rotated while the polishing layer is pressed against the material to be polished, or the material to be polished can be rotated while the material is pressed against the polishing layer to polish it.

[0033] The polishing pad of the present invention can be produced by commonly known manufacturing methods such as molding and slab molding. First, a block of polyurethane resin or the like is formed by such a manufacturing method, and the block is then sliced ​​or otherwise formed into a sheet to form the polishing layer, which is then attached to a support or the like. Alternatively, the polishing layer can be formed directly on the support.

[0034] More specifically, a double-sided tape is attached to the polishing layer on the side opposite the polishing surface of the polishing layer, and the polishing pad is cut into a predetermined shape. There are no particular limitations on the double-sided tape, and any double-sided tape known in the art can be selected and used. In addition, the polishing pad may have a single-layer structure consisting of only the polishing layer, or may be a multi-layer structure in which another layer (underlayer, support layer) is attached to the side opposite the polishing surface of the polishing layer.

[0035] The polishing layer may further contain a polyurethane resin. The polyurethane resin is not particularly limited, but may be a cured product of a curable resin composition containing an isocyanate-terminated urethane prepolymer, a curing agent, and heat-expandable microspheres. The polishing layer may be formed by preparing a curable resin composition containing an isocyanate-terminated urethane prepolymer, a curing agent, and heat-expandable microspheres, and then foaming and curing the curable resin composition. The curable resin composition may be a two-component composition prepared by mixing, for example, a liquid A containing an isocyanate-terminated urethane prepolymer and a liquid B containing a curing agent component. The other components may be contained in either liquid A or liquid B, but if problems arise, the composition may be further divided into multiple liquids and mixed to form a composition consisting of three or more liquids.

[0036] (3) Isocyanate-Terminated Urethane Prepolymer The isocyanate-terminated urethane prepolymer can be a product obtained by reacting a polyol component with a polyisocyanate component.

[0037] (Polyol Component) As the polyol component, a low molecular weight polyol, a high molecular weight polyol, or a combination thereof can be used. In this specification, a low molecular weight polyol is a polyol having a number average molecular weight of 30 to 300, and a high molecular weight polyol is a polyol having a number average molecular weight of more than 300. The number average molecular weights of the high molecular weight polyol and the low molecular weight polyol can be measured as molecular weights converted into polyethylene glycol / polyethylene oxide (PEG / PEO) based on gel permeation chromatography (GPC) under the following conditions. <Measurement Conditions> Column: Ohpak SB-802.5HQ (exclusion limit 10,000) + SB-803HQ (exclusion limit 100,000) Mobile phase: 5 mM LiBr / DMF Flow rate: 0.3 ml / min (26 kg / cm ２ ) Oven: 60°C Detector: RI 40°C Sample volume: 20 μl

[0038] Examples of the low molecular weight polyol include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, and combinations of two or more of these.

[0039] Examples of the high molecular weight polyol include polyether polyols such as polytetramethylene ether glycol (PTMG), polyethylene glycol, and polypropylene glycol; polyester polyols such as a reaction product of ethylene glycol and adipic acid, and a reaction product of butylene glycol and adipic acid; polycarbonate polyols; polycaprolactone polyols; and combinations of two or more of these.

[0040] (Polyisocyanate Component) Examples of the polyisocyanate component include m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-tolylene diisocyanate (2,6-TDI), 2,4-tolylene diisocyanate (2,4-TDI), naphthalene-1,4-diisocyanate, diphenylmethane-4,4'-diisocyanate (MDI), 4,4'-methylene-bis(cyclohexyl isocyanate) (hydrogenated MDI), 3,3'-dimethoxy-4,4'-biphenyl diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, xylylene-1,4-diisocyanate, 4,4'-diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, Examples of suitable diisocyanates include propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, cyclohexylene-1,2-diisocyanate, cyclohexylene-1,4-diisocyanate, p-phenylene diisothiocyanate, xylylene-1,4-diisothiocyanate, ethylidine diisothiocyanate, and combinations of two or more thereof. Among these, tolylene diisocyanates such as 2,6-tolylene diisocyanate (2,6-TDI) and 2,4-tolylene diisocyanate (2,4-TDI) are preferred from the viewpoint of polishing properties.

[0041] The NCO equivalent (g / eq) of the isocyanate-terminated urethane prepolymer is preferably less than 600, more preferably 350 to 550, and most preferably 400 to 500. Having an NCO equivalent (g / eq) within the above range allows the polishing layer to exhibit appropriate hardness. The NCO equivalent (g / eq) is calculated by the formula "(parts by mass of polyisocyanate compound + parts by mass of polyol compound) / [(number of functional groups per polyisocyanate compound molecule × parts by mass of polyisocyanate compound / molecular weight of polyisocyanate compound) - (number of functional groups per polyol compound molecule × parts by mass of polyol compound / molecular weight of polyol compound)]", and is a numerical value indicating the molecular weight of the prepolymer per NCO group.

[0042] (4) Curing Agent Examples of the curing agent contained in the curable resin composition include the amine-based curing agents described below. Examples of polyamines constituting the amine-based curing agent include diamines, such as alkylenediamines such as ethylenediamine, propylenediamine, and hexamethylenediamine; diamines having an aliphatic ring such as isophoronediamine and dicyclohexylmethane-4,4'-diamine; diamines having an aromatic ring such as 3,3'-dichloro-4,4'-diaminodiphenylmethane (also known as methylenebis-o-chloroaniline) (hereinafter abbreviated as MOCA); diamines having a hydroxyl group such as 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, and di-2-hydroxypropylethylenediamine, particularly hydroxyalkylalkylenediamines; or combinations of two or more of these. Furthermore, trifunctional triamine compounds and tetrafunctional or higher functional polyamine compounds can also be used.

[0043] A particularly preferred amine-based curing agent is the above-mentioned MOCA, the chemical structure of which is as follows:

[0044]

[0045] The total amount of curing agent is determined by the ratio of the number of moles of active hydrogen groups (NH ２ The ratio of the number of moles of the active hydrogen groups to the number of moles of NCO is preferably 0.70 to 1.10, more preferably 0.80 to 1.00, and most preferably 0.85 to 0.95.

[0046] (5) Other Components Other catalysts commonly used in the industry may also be added to the curable resin composition. The polyisocyanate component described above can also be added later to the curable resin composition. The weight ratio of the additional polyisocyanate component to the total weight of the isocyanate-terminated urethane prepolymer and the additional polyisocyanate component is preferably 0.1 to 10.0 wt %, more preferably 0.5 to 8.0 wt %, and particularly preferably 1.0 to 5.0 wt %. The polyisocyanate component additionally added to the polyurethane resin curable composition can be any of the polyisocyanate components described above without any particular limitations, but 4,4'-methylene-bis(cyclohexyl isocyanate) (hydrogenated MDI) is preferred.

[0047] <Second embodiment> A polishing pad according to a second embodiment of the present invention is a polishing pad having a polishing layer containing microspheres, in which pores are present on the surface of the polishing layer, and in a distribution curve of pore diameters on the surface of the polishing layer based on the pore perimeter x number fraction, there is a peak top in a region of pore diameters of 15 μm or less.

[0048] (1) Microspheres A foam can be formed by mixing microspheres with the components (such as polyurethane resin) that make up the polishing layer. The types, characteristics, content, and other components of the microspheres are not particularly limited and can be the same as those of the microspheres described in the first embodiment.

[0049] (2) Pores In a second embodiment of the present invention, the characteristics of the pores are defined based on a distribution curve of pore diameters on the surface of the polishing layer, based on the perimeter of the pores multiplied by the number fraction. The distribution curve of pore diameters on the surface of the polishing layer, based on the perimeter of the pores multiplied by the number fraction, can be a distribution curve with the horizontal axis representing the pore diameter and the vertical axis representing the perimeter of the pores multiplied by the number fraction. The distribution curve can be obtained based on the procedures and conditions described in (2) of the (Evaluation Method) in the Examples below.

[0050] The polishing pad of the second embodiment of the present invention can have the characteristics of the openings based on the distribution curve of the opening diameters on the surface of the polishing layer described above, which is based on the opening circumference x number fraction, as well as the characteristics of the openings based on the distribution curve of the opening diameters on the surface of the polishing layer, which is based on the number fraction on the surface of the polishing layer, as described in the first embodiment above.

[0051] In the distribution curve of the second embodiment, the upper limit of the pore size in the region where the peak top exists is 15 μm or less, and can also be 14 μm or less, or 13 μm or less. The lower limit of the pore size in the region where the peak top exists is not particularly limited, but can also be 6 μm or more, 7 μm or more, or 8 μm or more. The upper and lower limits of the pore size in the region where the peak top exists can be combined in any way.

[0052] In the distribution curve of the second embodiment, the lower limit of the pore perimeter x number fraction at the peak top is not particularly limited, but can be 10 μm-% or more, 11 μm-% or more, 12 μm-% or more, or 13 μm-% or more. The upper limit of the pore perimeter x number fraction at the peak top is not particularly limited, but can be 20 μm-% or less or 18 μm-% or less. The upper and lower limits of the pore perimeter x number fraction at the peak top can be combined in any way.

[0053] In the polishing pad of the second embodiment of the present invention, the pore size in the region where the peak exists in the distribution curve can be set to 15 μm or less, thereby suppressing the occurrence of scratches on the workpiece to be polished. The pores on the surface of the polishing layer having such characteristics can be formed by using specific unexpanded heat-expandable microspheres and expanding them under specific heating conditions, as in Examples 1 to 3 described below.

[0054] In the distribution curve of the second embodiment, the number of peak tops is not particularly limited, but is preferably 1. In the distribution curve of the second embodiment, the total value (integral value) of the perimeter x number fraction of the pores present in the region where the pore diameter is 15 μm or less is not particularly limited, but can be 30 to 80 μm·%, 40 to 75 μm·%, or 50 to 70 μm·%. Furthermore, the total value (integral value) of the perimeter x number fraction of the pores present in the region where the pore diameter is 20 μm or less is not particularly limited, but can be 60 to 90 μm·%, or 70 to 85 μm·%.

[0055] In the second embodiment, the characteristics of the surface of the polishing layer, such as the average pore diameter, the number of pores per unit area, and the pore rate, can be the same as those described in the first embodiment above.

[0056] In the second embodiment, the characteristics of the polishing layer, such as the density, Shore D hardness, and method of forming the polishing pad, can be the same as those described in the first embodiment above.

[0057] The polishing layer may further contain a polyurethane resin. The polyurethane resin may be, but is not limited to, a cured product of a curable resin composition containing an isocyanate-terminated urethane prepolymer, a curing agent, and heat-expandable microspheres. In the second embodiment, the characteristics of the isocyanate-terminated urethane prepolymer, the polyol component, the polyisocyanate component, the curing agent, and other components, such as their types and contents, may be the same as those described in the first embodiment.

[0058] 2. Method for Manufacturing a Polishing Pad The method for manufacturing a polishing pad of the present invention is a method for manufacturing a polishing pad having a polishing layer containing microspheres, and includes the steps of: (a) preparing a curable resin composition containing heat-expandable microspheres having an average particle size (D50) of 1 to 20 μm; and (b) heating the curable resin composition under heating conditions including a temperature increase rate of 1.5 to 7.5° C. / min to cure the curable resin composition to form the polishing layer and expand the heat-expandable microspheres to form microspheres.

[0059] The heat-expandable microspheres have an average particle size (D50) of 1 to 20 μm, more preferably 3 to 15 μm, and most preferably 6 to 10 μm.

[0060] The characteristics of the heat-expandable microspheres, such as the type, expansion initiation temperature, and maximum expansion temperature, may be the same as those of the unexpanded heat-expandable microspheres described in the first embodiment.

[0061] Step (a) may include mixing the heat-expandable microspheres, an isocyanate-terminated urethane prepolymer, and a curing agent, which may be the same as those described in the first embodiment.

[0062] Step (b) can be carried out inside a mold. In this case, the method for producing a polishing pad can further include a step (casting step) of pouring the curable resin composition obtained in step (a) into a mold between steps (a) and (b). In order to prevent the curable resin composition from curing before casting, the temperature of the mold during the casting step is preferably 130°C or less, 100°C or less, or 90°C or less.

[0063] The temperature (or mold temperature) at the start of step (b) (or at the end of casting) is not particularly limited, but is preferably 75 to 140°C, 75 to 120°C, or 75 to 100°C to prevent excessive expansion of the heat-expandable microspheres, and can also be 75 to 95°C or 75 to 92°C.

[0064] The heating conditions (heating rate) during heating in step (b) are 1.5 to 7.5°C / min, and can also be 4.0 to 7.5°C / min, 6.0 to 7.5°C / min, or 7.0 to 7.5°C / min. When the heating conditions (heating rate) are within the above range, the average particle size of the heat-expandable microspheres can be controlled within a range that achieves the effects of the present invention. The above heating rate refers to the average heating rate over a specific period. The above heating rate can be adopted for a period of 2 to 10 minutes, 2 to 7 minutes, or 2 to 5 minutes, assuming that the start of step (b) or the end of casting is 0 minutes.

[0065] The temperature increase in step (b) can be carried out over a period of 0 to 20 minutes, 0 to 15 minutes, or 0 to 10 minutes, assuming that the start of step (b) or the end of casting is 0 minutes. The temperature of the curable resin composition after the temperature increase in step (b) can be 100 to 160°C, 100 to 140°C, 110 to 135°C, or 120 to 130°C. The temperature after the temperature increase can be maintained over a period of 5 to 60 minutes, 5 to 40 minutes, 10 to 30 minutes, or 10 to 20 minutes, assuming that the start of step (b) or the end of casting is 0 minutes.

[0066] As in Examples 1 to 3 described below, step (b) can be a primary curing step performed inside the mold, and after the primary curing step, the formed resin foam can be removed from the mold and subjected to secondary curing. Even in this case, the pores in the resulting polishing pad are formed in step (b) (primary curing), and the characteristics of the pores in the polishing pad are mainly determined by the conditions in step (b).

[0067] The polishing pad of the first or second embodiment described above can be obtained by the method for producing a polishing pad of the present invention.

[0068] 3. Method for Polishing the Surface of an Optical Material or a Semiconductor Material In the present invention, the method for polishing the surface of an optical material or a semiconductor material includes a step of polishing the surface of the optical material or the semiconductor material using the polishing pad of the first or second embodiment described above. In some embodiments of the present invention, the method for polishing the surface of an optical material or a semiconductor material can further include a step of supplying a slurry to the surface of the polishing pad, the surface of the optical material or the semiconductor material, or both.

[0069] (Slurry) The liquid component contained in the slurry is not particularly limited, but may include water (pure water), acid, alkali, organic solvent, or a combination thereof, and is selected depending on the material of the workpiece to be polished, the desired polishing conditions, etc. The slurry preferably contains water (pure water) as its main component, and preferably contains 80% by weight or more of water relative to the entire slurry. The abrasive component contained in the slurry is not particularly limited, but may include silica, zirconium silicate, cerium oxide, aluminum oxide, manganese oxide, or a combination thereof. The slurry may contain other components, such as organic substances soluble in the liquid component and pH adjusters.

[0070] The present invention will be experimentally explained by the following examples, but the following explanation is not intended to limit the scope of the present invention to the following examples.

[0071] (Materials) The materials used in Examples 1 to 3 and Comparative Examples 1 and 2 described below are listed below.

[0072] Isocyanate-terminated urethane prepolymer: Prepolymer (1)...A urethane prepolymer having an NCO equivalent of 455, containing 2,4-tolylene diisocyanate as a polyisocyanate component, polytetramethylene ether glycol having a number average molecular weight of 650 and polytetramethylene ether glycol having a number average molecular weight of 1000 as high-molecular-weight polyol components, and diethylene glycol as a low-molecular-weight polyol component.

[0073] Hardener: MOCA...3,3'-dichloro-4,4'-diaminodiphenylmethane (also known as methylenebis-o-chloroaniline) (MOCA) (NH ２ Equivalent = 133.5)

[0074] Microspheres: Microsphere (1)... Matsumoto Microsphere (registered trademark) FN-80GSD (manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.) (unexpanded type, average particle size (D50) in unexpanded state: 6 to 10 μm, expansion start temperature: 100 to 110°C, maximum expansion temperature: 125 to 135°C, shell composition: acrylonitrile-methyl methacrylate copolymer) Microsphere (2)... Expancel (registered trademark) 461DU20 (manufactured by Nippon Phillite Co., Ltd.) (unexpanded type, average particle size (D50) in unexpanded state: 6 to 9 μm, expansion start temperature: 100 to 106°C, maximum expansion temperature: 143 to 151°C, shell composition: acrylonitrile-vinylidene chloride copolymer) Microspheres (3)... Matsumoto Microsphere (registered trademark) HF-48D (manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.) (unexpanded type, average particle size (D50) in unexpanded state: 9 to 15 μm, expansion start temperature: 90 to 100°C, maximum expansion temperature: 125 to 135°C, shell composition: acrylonitrile-methyl methacrylate copolymer) Microspheres (4)... Expancel (registered trademark) 920DU20 (manufactured by Nippon Phillite Co., Ltd.) (unexpanded type, average particle size (D50) in unexpanded state: 5 to 9 μm, expansion start temperature: 120 to 145°C, maximum expansion temperature: 155 to 175°C, shell composition: acrylonitrile-methyl methacrylate copolymer)

[0075] Example 1 100 g of prepolymer (1) was prepared as component A, 26.3 g of MOCA, a curing agent, as component B, and 3.5 g of microspheres (1) as component C. Note that the amounts are expressed in g to indicate the ratio of each component, but it is sufficient to prepare the required weight (parts) depending on the size of the block. Below, the amounts are also expressed in g (parts). Component A and component C were mixed, and the resulting mixture of component A and component C was degassed under reduced pressure. Furthermore, MOCA, which is component B, was degassed under reduced pressure. The degassed mixture of component A and component C and the degassed component B were fed into a mixer to obtain a mixed solution of component A, component B, and component C. Note that in the resulting mixed solution of component A, component B, and component C, the ratio of the moles of NH of MOCA in component B to the moles of NCO of prepolymer (1) in component A was 0.01. ２ The ratio of moles of (NH ２The ratio of moles of NCO to moles of NCO was 0.9. The content of microspheres (1), which is component C, relative to the total weight of the mixed solution was 2.7% by weight. The resulting mixed solution of components A, B, and C was poured into a mold (850 mm x 850 mm square) heated to 90°C. The temperature was increased over a period of 2 to 10 minutes, with an average temperature increase rate of 7.3°C / min from 2 to 5 minutes after the end of the pouring, until the temperature reached 130°C 10 minutes after the end of the pouring. The temperature was then maintained at 130°C for 10 to 20 minutes after the end of the pouring to effect primary curing. The relationship between time and temperature from the end of the pouring during primary curing is shown in Figure 1. The formed resin foam was removed from the mold and subjected to secondary curing in an oven at 120°C for 4 hours. The resulting resin foam was allowed to cool to 25°C and then heated again in an oven at 120°C for 5 hours. The obtained resin foam was sliced ​​in the thickness direction to a thickness of 1.3 mm to prepare a urethane sheet, and a double-sided tape was attached to the back surface of this urethane sheet to prepare a polishing pad.

[0076] (Example 2) A urethane sheet was produced in the same manner as in Example 1, except that the amount of microspheres (1) used as component C in Example 1 was changed from 3.5 g to 2.7 g, and a polishing pad of Example 2 was obtained. The relationship between the time from the end of casting and the temperature in the primary curing was the same as in Example 1, as shown in Figure 1. In addition, in the obtained mixed solution of components A, B, and C, the ratio of the moles of NH of MOCA of component B to the moles of NCO of prepolymer (1) of component A was 0.01. ２ The ratio of moles of (NH ２ The ratio (moles of NCO / moles of NCO) was 0.9. The content of the microspheres (1) as component C relative to the total amount of the mixed solution was 2.1% by weight.

[0077] Example 3 A mixed solution of components A, B, and C was obtained in the same manner as in Example 1, except that 3.5 g of microspheres (4) was used instead of 3.5 g of microspheres (1) of component C in Example 1. In the obtained mixed solution of components A, B, and C, the ratio of the moles of NH of MOCA of component B to the moles of NCO of prepolymer (1) of component A was 0.01. ２ The ratio of moles of (NH ２The ratio of moles of NCO to moles of NCO was 0.9. The content of microspheres (4), which is component C, relative to the total weight of the mixed solution was 2.7% by weight. The resulting mixed solution of components A, B, and C was poured into a mold (850 mm x 850 mm square) heated to 120°C. The temperature was increased over a period of 2 to 15 minutes, with an average temperature increase rate of 6.9°C / min from 2 to 5 minutes after the end of the pouring, until the temperature reached 150°C 15 minutes after the end of the pouring. The temperature was then maintained at 150°C for 15 to 20 minutes after the end of the pouring to effect primary curing. The relationship between time and temperature from the end of the pouring during primary curing is shown in Figure 1. The formed resin foam was removed from the mold and subjected to secondary curing in an oven at 120°C for 4 hours. The resulting resin foam was allowed to cool to 25°C and then heated again in an oven at 120°C for 5 hours. The obtained resin foam was sliced ​​in the thickness direction to a thickness of 1.3 mm to prepare a urethane sheet, and a double-sided tape was attached to the back surface of this urethane sheet to prepare a polishing pad.

[0078] Comparative Example 1 A mixed solution of components A, B, and C was obtained in the same manner as in Example 1, except that 2.9 g of microspheres (2) was used instead of 3.5 g of microspheres (1) of component C in Example 1. In the obtained mixed solution of components A, B, and C, the ratio of the moles of NH of MOCA of component B to the moles of NCO of prepolymer (1) of component A was 0.01. ２ The ratio of moles of (NH ２The ratio of moles of NCO to moles of NCO was 0.9. The content of microspheres (2), which is component C, relative to the total weight of the mixed solution was 2.2% by weight. The resulting mixed solution of components A, B, and C was poured into a mold (850 mm x 850 mm square) heated to 80°C. The temperature was increased over a period of 2 to 15 minutes, with an average temperature increase rate of 8.0°C / min from 2 to 5 minutes after the end of pouring, until the temperature reached 128°C 15 minutes after the end of pouring. The primary curing was then carried out by maintaining the temperature at 128°C for 15 to 20 minutes after the end of pouring. The relationship between time and temperature during the primary curing period from the end of pouring is shown in Figure 1. The formed resin foam was removed from the mold and subjected to secondary curing in an oven at 120°C for 4 hours. The resulting resin foam was allowed to cool to 25°C and then heated again in an oven at 120°C for 5 hours. The obtained resin foam was sliced ​​in the thickness direction to a thickness of 1.3 mm to prepare a urethane sheet, and a double-sided tape was attached to the back surface of this urethane sheet to prepare a polishing pad.

[0079] (Comparative Example 2) A mixed solution of components A, B, and C was obtained in the same manner as in Comparative Example 1, except that 2.7 g of microspheres (3) was used instead of 2.9 g of microspheres (2) of component C in Comparative Example 1. In the obtained mixed solution of components A, B, and C, the ratio of the moles of NH of MOCA of component B to the moles of NCO of prepolymer (1) of component A was 0.01. ２ The ratio of moles of (NH ２The ratio of moles of NCO to moles of NCO was 0.9. The content of microspheres (3), which constitute component C, relative to the total weight of the mixed solution was 2.1% by weight. The resulting mixed solution of components A, B, and C was poured into a mold (850 mm x 850 mm square) heated to 80°C. The temperature was increased over a period of 2 to 15 minutes, with an average temperature increase rate of 7.6°C / min from 2 to 5 minutes after the end of pouring, until the temperature reached 128°C 15 minutes after the end of pouring. The primary curing was then carried out by maintaining the temperature at 128°C for 15 to 20 minutes after the end of pouring. The relationship between time and temperature during the primary curing period from the end of pouring is shown in Figure 1. The formed resin foam was removed from the mold and subjected to secondary curing in an oven at 120°C for 4 hours. The resulting resin foam was allowed to cool to 25°C and then heated again in an oven at 120°C for 5 hours. The obtained resin foam was sliced ​​in the thickness direction to a thickness of 1.3 mm to prepare a urethane sheet, and a double-sided tape was attached to the backside of this urethane sheet to prepare a polishing pad.

[0080] (Comparative Example 3) An attempt was made to produce a urethane sheet using the mixed solution of components A, B, and C obtained in Example 1 under the same curing conditions as in Comparative Example 1, but component C did not expand, and no pores were observed. As a result, an appropriate urethane sheet and polishing pad with pores could not be obtained, and therefore the evaluation of the urethane sheet and polishing pad described below for Comparative Example 3 could not be carried out.

[0081] (Evaluation Method) The following measurements or evaluations were made for the urethane sheets (before the double-sided tape was attached) or polishing pads of Examples 1 to 3 and Comparative Examples 1 and 2: (1) density and Shore D hardness, (2) average pore size, pore rate, pore number, and distribution curve, (3) scratches, and (4) polishing rate. The measurement results are shown in Tables 1 to 4 and Figures 2 to 11.

[0082] (1) Density and Shore D Hardness (Density) The density of the urethane sheet (g / cm ３ ) was measured in accordance with Japanese Industrial Standards (JIS K 6505).

[0083] (Shore D Hardness) The Shore D hardness of the urethane sheet was measured using a D-type hardness tester in accordance with Japanese Industrial Standards (JIS-K-6253). Here, the measurement sample was obtained by stacking multiple urethane sheets as necessary to achieve a total thickness of at least 4.5 mm.

[0084] (2) Average pore size, pore ratio, number of pores, and distribution curve Three regions (each 0.5 mm long x 0.7 mm wide rectangle) were randomly selected from the surface of the polishing layer of the polishing pad so as not to be biased, and each region was observed at 400x magnification using a laser microscope (VK-X1000, manufactured by KEYENCE). Each of the obtained images (0.5 mm long x 0.7 mm wide rectangle) was binarized using image processing software (WinROOF2018 Ver. 4.0.2, manufactured by Mitani Shoji) to confirm the pores, and the circle equivalent diameter (pore size) was calculated from the area of ​​each pore. The cutoff value (lower limit) of the pore size was set to 5 μm to exclude noise components. Average pore size The average pore size for each region was calculated by averaging all the pore sizes contained in each of the above regions (images). The average pore diameters of the three regions thus obtained were further averaged to calculate the final average pore diameter. - Opening rate The ratio (%) of the total area of ​​the open pores per area of ​​each of the above regions (images) (total area of ​​the open pores / area of ​​the image (region) x 100) was calculated. The opening rates of the three regions thus obtained were further averaged to calculate the final opening rate. - Number of openings The number of openings per area of ​​each of the above regions (images) (number / mm ２) was calculated. The number of pores in the three regions thus obtained was further averaged to calculate the final number of pores. Distribution curve: For the pore diameters calculated by the image observation described above in each of the above regions (images), a pore diameter histogram was represented by a broken line, with one class per 2 μm range (for example, 15.0 μm or more, less than 17.0 μm, etc.). In the pore diameter histogram, the ratio (number fraction) (%) of the number of pores in each class to the total number of pores in all classes was calculated (number of pores in each class / total number of pores in all classes × 100). In addition, the minimum value of the pore diameter in each class (for example, 15.0 μm for the class of 15.0 μm or more and less than 17.0 μm) was multiplied by pi to calculate the pore circumference (the length of the circumference of the pores) in each class. Then, a distribution curve of pore size-number fraction and a distribution curve of pore size-pore perimeter x number fraction were obtained for each region (image). The distribution curves of pore size-number fraction and the distribution curves of pore size-pore perimeter x number fraction obtained in this manner for the three regions were further averaged to obtain a final distribution curve of pore size-number fraction and a distribution curve of pore size-pore perimeter x number fraction.

[0085] (3) Scratches: To evaluate scratches, a substrate was polished using a polishing pad under the conditions described below (Polishing Test). The polished substrate was measured using a wafer surface inspection device (KLA-Tencor Corporation, Surfscan SP5) in high-sensitivity measurement mode to detect defects (surface defects) measuring 110 nm or more across the entire substrate. Each detected defect was analyzed using a review SEM image, which was then classified into "particles," "pad debris," and "scratches." The number of scratches among these was counted. The results are the average results for n4. Here, the category "particles" refers to fine particles remaining on the surface of the object being polished, the category "pad debris" refers to debris from the polishing layer adhering to the surface of the object being polished, and the category "scratches" refers to scratches on the surface of the object being polished.

[0086] (Polishing test) Polishing machine used: F-REX300X (manufactured by Ebara Corporation) Disk: A188 (manufactured by 3M) Abrasive temperature: 20°C Polishing platen rotation speed: 85 rpm Polishing head rotation speed: 86 rpm Polishing pressure: 3.5 psi Polishing slurry (metal film): CSL-9044C (a mixture of CSL-9044C stock solution and purified water at a weight ratio of 1:1 was used) (manufactured by Fujimi Corporation) Polishing slurry flow rate: 200 ml / min Polishing time: 60 seconds Workpiece (metal film): Cu film substrate (disc-shaped, 300 mm diameter) Pad break: 35 N, 10 minutes Conditioning: Ex-situ, 35 N, 4 scans

[0087] (4) Polishing Rate For the polishing pad, the polishing rate was measured for the polished object polished under the polishing conditions described in (3) (Polishing Test) above as follows. Measurements were performed in the diameter direction on the Cu film substrate before and after the polishing test, and the thickness at those locations before and after the polishing test was measured. Based on the measured thicknesses, the average thickness before the polishing test and the average thickness after the polishing test were calculated, and the average polished thickness was calculated by taking the difference between these average values. The obtained average polished thickness was then used as the polishing rate per 60 seconds of polishing time. The thickness was measured using a four-probe sheet resistance measurement device (manufactured by KLA Tencor Corporation, product name "RS-200", measurement: DBS mode).

[0088]

[0089]

[0090] Figures 2 to 6 are graphs showing the distribution curves of the open pore size-number fraction on the polishing layer surface of each of Examples 1 to 3 and Comparative Examples 1 and 2. Figures 7 to 11 are graphs showing the distribution curves of the open pore size-open pore circumference x number fraction on the polishing layer surface of each of Examples 1 to 3 and Comparative Examples 1 and 2. Tables 3 and 4 show the characteristics of each distribution curve in Figures 2 to 11.

[0091]

[0092]

[0093] 2 to 4 and 7 to 9 and Tables 3 and 4, the polishing pads of Examples 1 to 3 are polishing pads in which, in the distribution curve of the pore size based on the number fraction on the surface of the polishing layer, a peak top exists in a region of pore size of 15 μm or less, and the number fraction of the pores at the peak top is 15% or more. Furthermore, the polishing pads of Examples 1 to 3 are polishing pads in which, in the distribution curve of the pore size based on the pore perimeter × number fraction on the surface of the polishing layer, a peak top exists in a region of pore size of 15 μm or less. On the other hand, as can be seen from Figures 5, 6, 10 and 11 and Tables 3 and 4, the polishing pads of Comparative Examples 1 and 2 have a peak top in the region of pore diameters of 15 μm or less in the distribution curve of pore diameters based on the number fraction on the surface of the polishing layer, but the number fraction of pores at the peak top is less than 15%.Furthermore, in the distribution curve of pore diameters based on the pore circumference x number fraction on the surface of the polishing layer, the polishing pads have a peak top in the region of pore diameters of more than 15 μm.

[0094] As can be seen from the results in Table 2, the polishing pads of Examples 1 to 3 had a small number of scratches, were able to sufficiently suppress the occurrence of scratches, and also had a polishing rate exceeding 8000 Å, demonstrating sufficient polishing performance. On the other hand, the polishing pads of Comparative Examples 1 and 2 had a high polishing rate, but had a large number of scratches, and it was found that they were not able to sufficiently suppress the occurrence of scratches compared to Examples 1 to 3.

[0095] From the above results, it was found that a polishing pad in which the distribution curve of pore diameters based on the number fraction on the surface of the polishing layer of the present invention has a peak top in the region of pore diameters of 15 μm or less, and the number fraction of pores at the peak top is 15% or more, or a polishing pad in which the distribution curve of pore diameters based on the pore circumference x number fraction on the surface of the polishing layer has a peak top in the region of pore diameters of 15 μm or less, can suppress the occurrence of scratches.

Claims

1. 1. A polishing pad having a polishing layer comprising microspheres, The polishing layer has openings on its surface, The polishing pad, wherein a distribution curve of pore diameters based on the number fraction on the surface of the polishing layer has a peak top in a region of pore diameters of 15 μm or less, and the number fraction of the pores at the peak top is 15% or more.

2. 1. A polishing pad having a polishing layer comprising microspheres, The polishing layer has openings on its surface, The polishing pad, wherein a distribution curve of pore diameters on the surface of the polishing layer, based on pore circumference x number fraction, has a peak top in a region of pore diameters of 15 μm or less.

3. 2. The polishing pad according to claim 1, wherein the number ratio of the open pores at the peak top is 17% or more.

4. 4. The polishing pad according to claim 1, wherein the average pore size on the surface of the polishing layer is 5 to 20 μm.

5. The number of the openings per unit area on the surface of the polishing layer is 1200 to 2500 / mm ２ 4. The polishing pad according to claim 1, wherein

6. 4. The polishing pad according to claim 1, wherein the surface of the polishing layer has an open porosity of 10 to 50%.

7. 4. The polishing pad according to claim 1, wherein the polishing layer further comprises a polyurethane resin.

8. 8. The polishing pad according to claim 7, wherein the polyurethane resin is a cured product of a curable resin composition comprising an isocyanate-terminated urethane prepolymer, a curing agent, and heat-expandable microspheres.

9. 1. A method for manufacturing a polishing pad having a polishing layer containing microspheres, comprising: (a) preparing a curable resin composition containing heat-expandable microspheres having an average particle size (D50) of 1 to 20 μm; and (b) heating the curable resin composition under heating conditions including a temperature increase rate of 1.5 to 7.5°C / min to cure the curable resin composition to form the polishing layer and expand the heat-expandable microspheres to form the microspheres; A method for producing the polishing pad, comprising:

10. 10. The method for producing a polishing pad according to claim 9, wherein the polishing pad is the polishing pad according to any one of claims 1 to 3.

11. A method for polishing a surface of an optical material or a semiconductor material, the method comprising the step of polishing the surface of the optical material or the semiconductor material using the polishing pad according to any one of claims 1 to 3.