JP7575328B2 - Polishing pad and method for producing the same - Google Patents

Description

The present invention relates to a polishing pad and a manufacturing method thereof, and in particular to a polishing pad for chemical mechanical polishing (CMP) having a light-transmitting region and a manufacturing method thereof. More specifically, the present invention relates to a polishing pad having an end point detection window that allows optical detection of the polishing end point.

Chemical mechanical polishing (hereinafter referred to as "CMP") is used in the manufacturing process of semiconductor integrated circuits (hereinafter referred to as "LSI") (particularly, planarization of interlayer insulating films in the multilayer wiring formation process, metal plug formation, or embedded wiring formation). CMP is a technique for polishing a wafer by using a slurry in which abrasive grains are dispersed while the surface to be polished is pressed against the polishing surface of a polishing pad. Polishing pads used in CMP are broadly classified into hard polishing pads and soft polishing pads. Hard polishing pads are mainly used in the dry molding method in which a curable composition containing a urethane prepolymer is poured into a mold and cured, while soft polishing pads are mainly used in the wet film formation method in which a urethane resin solution is formed into a film in a coagulation bath and dried. In recent years, low defectivity and step elimination of the polished object have been highly required, and the number of cases in which soft polishing pads are used in the finish polishing process and the like is increasing.
In recent years, semiconductor elements have been rapidly multi-layered and highly fine, and further improvement in the yield and throughput of semiconductor elements is required, and polishing pads are required to be defect-free and have high planarization without dishing. In addition, if the time to end polishing cannot be accurately detected, over-polishing will cause defective products, so performance that does not cause over-polishing is required. In order to meet these requirements and perform high-precision CMP, it is necessary to determine the polishing end point, and it is necessary to detect the time when the desired surface characteristics and flatness are reached, and the end point has been detected by optical measurement.

Optical measurement is a method of observing the surface of a wafer through a measurement window provided in the polishing pad. When providing a measurement window in the polishing pad for optical measurement, a transparent material of a different material from the polishing pad must be placed in the window area because polishing pads are generally not transparent. If the surface of this transparent material is scratched during polishing, the light transmittance decreases. This makes it difficult to maintain high accuracy in determining the polishing end point from the beginning to the end of the polishing process. In addition, when a soft polishing pad is used in the finish polishing process, the window protrudes onto the polishing surface when the polishing pad is pressed against the wafer, and this hard window, which does not have the protruding polishing ability, may come into contact with the wafer and cause polishing scratches.

To solve these problems, a polishing pad with a window for detecting the end point has been proposed, in which the window member is located in a recessed position below the polishing surface (Patent Document 1, Patent Document 2).

JP 2014-104521 A JP 2002-1652 A

However, the polishing pad of Patent Document 1 has a problem in that the polishing slurry sinks into the recessed window area, reducing light transmittance. The polishing pad of Patent Document 2 has a window groove near the light-transmitting window, which can promote the discharge of the polishing slurry from the top surface of the light-transmitting window, but has a problem in that the light transmittance value varies, making accurate optical measurement difficult.

The present invention has been made in consideration of the above, and aims to provide a polishing pad that can reduce variations in light transmittance.

By applying a specific resin to the polishing surface side of the translucent resin member, the present invention suppresses the large variation in light transmittance that occurs between when slurry is present and when it is not present on the surface of the translucent resin member, thereby enabling more accurate determination of the polishing end point. That is, the present invention provides the following.

[1] A polishing pad having a light-transmitting resin member and a polishing layer,
the polishing layer has a polishing surface for polishing an object to be polished, and the polishing pad has a through hole extending from the polishing surface to an opposite surface thereof;
the light-transmitting resin member is disposed so as to be present in the through-hole when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad, and the light-transmitting resin member has a resin containing a constitutional unit derived from a polyfunctional (meth)acrylate monomer having two or more polymerizable functional groups and having a _-C2-4 alkylene-O- unit, at least on the surface of the polishing surface side of the polishing pad.
The polishing pad.
[2] The polyfunctional (meth)acrylate monomer is selected from the group consisting of the following:
The polishing pad according to [1] is at least one selected from the group consisting of a monomer in which a compound having a _-C2-4 alkylene-O- unit and (meth)acrylic acid are ester-bonded, and a monomer in which a trihydric or higher alcohol to which a _C2-4 alkylene oxide has been added is ester-bonded with (meth)acrylic acid.
[3] The polishing pad according to [2], wherein the trihydric or higher alcohol is selected from the group consisting of glycerin, diglycerin, triglycerin, trimethylolpropane, ditrimethylolpropane, erythritol, pentaerythritol and dipentaerythritol.
[4] The polishing pad according to any one of [1] to [3], wherein the _-C2-4 alkylene-O- unit is derived from ethylene oxide and/or propylene oxide.
[5] The polishing pad according to any one of [1] to [4], wherein the polyfunctional (meth)acrylate monomer is at least one selected from the group consisting of polyethylene glycol diacrylate, polypropylene glycol diacrylate, ethoxylated pentaerythritol tetraacrylate, propoxylated pentaerythritol tetraacrylate, ethoxylated glycerin triacrylate, propoxylated glycerin triacrylate, ethoxylated trimethylolpropane triacrylate, and propoxylated trimethylolpropane triacrylate.
[6] The polishing pad according to any one of [1] to [5], wherein when the polishing surface is the upper surface and the opposite surface is the lower surface, the surface of the polishing surface side of the translucent resin member is lower than the polishing surface.
[7] The polishing pad according to any one of [1] to [6], wherein the polishing surface has grooves.
[8] The polishing pad according to [7], wherein the groove is an embossed groove.
[9] The polishing pad according to [7] or [8], wherein when the polishing surface is the upper surface and the opposite surface is the lower surface, the surface of the polishing surface side of the translucent resin member is at the same position as or higher than the lowest part of the groove.
[10] The polishing pad according to any one of [1] to [9], wherein the through holes have a circular shape when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad.
[11] When the through hole of the polishing layer is a first through hole, the polishing pad further includes another layer having a second through hole having a smaller circle equivalent diameter than the first through hole,
The other layer is located on the opposite side to the polishing surface of the polishing layer,
When the polishing pad is viewed in a thickness direction from a polishing surface side, the first through hole and the second through hole at least partially overlap each other,
The polishing pad according to any one of claims 1 to 10, wherein the translucent resin member is arranged so that the translucent resin member is present within the first through hole when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad.
[12] A step of preparing a polishing layer and a light-transmitting resin member having, on at least one surface thereof, a resin containing a structural unit derived from a polyfunctional (meth)acrylate monomer having two or more polymerizable functional groups and having a _-C2-4 alkylene-O- unit;
providing a through hole in the polishing layer; and disposing the light-transmitting resin member so that the light-transmitting resin member is present in the through hole when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad, wherein the light-transmitting resin member is disposed so that a surface of the light-transmitting resin member having a resin containing a structural unit derived from the polyfunctional (meth)acrylate monomer faces the polishing surface.
The method for producing a polishing pad according to any one of [1] to [11], comprising:

According to the present invention, it is possible to provide a polishing pad that can suppress variations in light transmittance. This makes it possible to determine the polishing end point with high accuracy.

FIG. 1 is a perspective view of a polishing pad according to one embodiment of the present invention, as viewed in the thickness direction from the polishing surface. FIG. 2 is a schematic cross-sectional view (cut end surface) in the thickness direction of a polishing pad according to one embodiment of the present invention. FIG. 3 is a schematic cross-sectional view (cut end surface) in the thickness direction of a polishing pad according to one embodiment of the present invention. FIG. 4 is a schematic cross-sectional view (cut end surface) in the thickness direction of a polishing pad according to one embodiment of the present invention.

The following describes how to implement the present invention.

<<Polishing pad>>
The polishing pad of the present invention is a polishing pad having a light-transmitting resin member and a polishing layer, wherein the polishing layer has a polishing surface for polishing an object to be polished, the polishing pad has a through hole penetrating from the polishing surface to the opposite surface, the light-transmitting resin member is arranged such that, when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad, the light-transmitting resin member is present in the through hole, and the light-transmitting resin member has, at least on the surface on the polishing surface side, a resin that contains a constituent unit derived from the polyfunctional (meth)acrylate monomer having two or more polymerizable functional groups and having a _-C2-4 alkylene-O- unit.
Hereinafter, a resin containing a structural unit derived from a polyfunctional (meth)acrylate monomer having two or more polymerizable functional groups and having a _-C2-4 alkylene-O- unit may be abbreviated as a resin containing a structural unit derived from a polyfunctional (meth)acrylate monomer. Similarly, a polyfunctional (meth)acrylate monomer having two or more polymerizable functional groups and having a _-C2-4 alkylene-O- unit may be abbreviated as a polyfunctional (meth)acrylate monomer.

In the present specification and claims, a polishing layer is a layer having a surface (polishing surface) that contacts and polishes an object to be polished, such as a semiconductor device. The object to be polished is not particularly limited, and examples thereof include substrates such as product substrates including multiple memory or processor dies, test substrates, bare substrates, and gate substrates. The substrates can be at various stages of integrated circuit manufacturing, for example, the substrate can be a bare wafer or one or more deposition layers and/or patterned layers.
Also, with reference to Figures 2 to 4, at least the surface on the polished side of the translucent resin member refers to the surface portion 9 on the polished side of the translucent resin member 4 when the polished surface is the upper surface and the opposite surface is the lower surface.

<Light-transmitting resin member>
The polishing pad of the present invention has a light-transmitting resin member, i.e., a window member. By irradiating the workpiece with light through the light-transmitting resin member, it is possible to detect the time when the workpiece reaches the desired surface characteristics and flatness. A visible light (white light) laser, lamp, or the like is used for optical end point detection.

The translucent resin member is arranged so that it is present in the through hole when viewed from the polishing surface side of the polishing pad in the thickness direction of the polishing pad. Here, "arranged so that the translucent resin member is present in the through hole when viewed from the polishing surface side of the polishing pad in the thickness direction of the polishing pad" is intended to be arranged so that the translucent resin member can be confirmed when the through hole is viewed in the thickness direction from the polishing surface of the polishing pad, and includes the following concepts: (1) the translucent resin member is arranged so as to contact (or be bonded to) the side (side wall) of the through hole provided in the polishing layer as shown in FIG. 2, (2) as shown in FIG. 3, another layer having a through hole with a circle equivalent diameter smaller than the circle equivalent diameter of the through hole of the polishing layer is provided under the polishing layer, and the translucent resin member is arranged on the exposed portion 7 resulting from the difference in size between the through hole of the polishing layer and the through hole of the other layer, and (3) as shown in FIG. 4, the translucent resin member is sandwiched between the polishing layer and the other layer, and a part of the translucent resin member is arranged so as to be exposed in the through hole. Among these, (1) or (2) is preferred, and (2) is more preferred.

The translucent resin member is not particularly limited as long as it is a resin that has a transparency sufficient to transmit light. For example, thermosetting resins such as polyurethane resin, polyester resin, phenol resin, urea resin, melamine resin, epoxy resin, and acrylic resin, thermoplastic resins such as polyurethane resin, polyester resin, polyamide resin, cellulose-based resin, acrylic resin, polycarbonate resin, halogen-based resin (polyvinyl chloride, polytetrafluoroethylene, polyvinylidene fluoride, etc.), polystyrene resin, and olefin-based resin (polyethylene, polypropylene, etc.), rubber such as butadiene rubber and isoprene rubber, photocurable resins that are cured by ultraviolet rays or electron beams, and photosensitive resins can be used. Among these, acrylic resin, polyurethane resin, polyester resin, and polystyrene resin are preferred, and acrylic resin is more preferred. By using these resin members, adhesion to resins containing polyfunctional (meth)acrylate monomers as constituent units is improved, making them less likely to peel off.

There are no particular limitations on the translucent resin member as long as it is a resin that has a degree of transparency that allows light to pass through it, but it is preferable that the visible light transmittance (sometimes simply referred to as light transmittance in this specification) when irradiated with light having a wavelength of 380 nm to 780 nm is 60% or more, more preferably 65% or more, even more preferably 70% or more, even more preferably 75% or more, and even more preferably 80% or more. Visible light transmittance can be measured by measuring the transmission spectrum at wavelengths of 300 to 1000 nm with a spectrophotometer and calculating the visible light transmittance (%) according to the Japanese Industrial Standards (JIS A5759:2008).

(Polyfunctional (meth)acrylate monomer)
The polishing pad of the present invention has a resin, at least on the polishing surface side of the light-transmitting resin member, which contains a constitutional unit derived from a polyfunctional (meth)acrylate monomer having two or more polymerizable functional groups and having a _-C2-4 alkylene-O- unit.
"Having -C _2-4 alkylene-O- units" means having one or more -C _2-4 alkylene-O- basic units. When having one basic unit or having multiple repeating basic units, it can be rephrased as having (-C _2-4 alkylene-O-) _n (n is an integer of 1 or more). There are no particular restrictions on the number of basic units or the number n, but 1 to 30 is preferred, 2 to 28 is more preferred, 3 to 25 is even more preferred, and 4 to 25 is even more preferred.
The polyfunctional (meth)acrylate monomer may have one kind of —C _2-4 alkylene-O— unit, or may have two or more different kinds of —C _2-4 alkylene-O— units.
The number of -C _2-4 alkylene-O- per polyfunctional (meth)acrylate monomer is preferably 1-30, more preferably 2-28, even more preferably 3-25, and even more preferably 4-25.
The _-C2-4 alkylene-O- unit is preferably a _-C2-3 alkylene-O- unit. The _-C2-4 alkylene-O- unit is preferably one derived from ethylene oxide ( _-CH2 - _CH2 -O-) and/or one derived from propylene oxide ( _-CH2- CH( _CH3 )-O- or -CH( _CH3 )-CH2 _- O- (preferably -CH2 _- CH( _CH3 )-O-)). The polyfunctional (meth)acrylate monomer is preferably a polyfunctional (meth)acrylate monomer having a _-CH2 - _CH2 -O- unit and/or a _-CH2 -CH( _CH3 )-O- unit.

The polyfunctional (meth)acrylate monomer contains a _-C2-4 alkylene-O- unit. The _-C2-4 alkylene-O- unit may be present in any manner in the polyfunctional (meth)acrylate monomer, and may be, for example, bonded via an ester bond to a carboxyl group of (meth)acrylic acid, or bonded (via an ester bond, ether bond, etc.) to a group bonded (via an ester bond, amide bond, etc.) to the carboxyl group of (meth)acrylic acid.

The light-transmitting resin member may be coated with a resin containing a structural unit derived from a polyfunctional (meth)acrylate monomer at least on the polishing surface side of the light-transmitting resin member, or the light-transmitting resin member itself may be composed of a resin containing a structural unit derived from a polyfunctional (meth)acrylate monomer, but it is more preferable that the light-transmitting resin member is coated with a resin containing a structural unit derived from a polyfunctional (meth)acrylate monomer at least on the polishing surface side of the light-transmitting resin member. By coating the surface on the polishing surface side with the resin, the wettability with the slurry is improved, and the variation in light transmittance caused by the presence or absence of slurry on the surface of the light-transmitting resin member can be suppressed. This makes it possible to determine the polishing end point with higher accuracy.
In addition, the translucent resin member may be coated with the resin not only on the surface facing the polishing surface, but also on the surface opposite the polishing surface (back surface) and side surfaces. However, coating the back surface and side surfaces will increase costs, while coating the back surface and side surfaces is not related to the effects of the present invention, so it is preferable that only the surface facing the polishing surface be coated with the resin.
The thickness of the surface layer of the light-transmitting member coated with the resin is not particularly limited, but is preferably 1 to 50 μm. If the thickness of the surface layer is within the above range, high light transmittance can be obtained.

The polyfunctional (meth)acrylate monomer is preferably at least one selected from the group consisting of (i) a monomer in which a compound having a _-C2-4 alkylene-O- unit is bonded to (meth)acrylic acid via an ester bond, and (ii) a monomer in which a trivalent or higher alcohol to which a _C2-4 alkylene oxide has been added is bonded to (meth)acrylic acid via an ester bond.
As the monomer (i), a monomer in which a compound having a _-C2-3 alkylene-O- unit and (meth)acrylic acid are bonded via an ester bond is preferred.
As the monomer (ii), a monomer in which a trihydric or higher alcohol to which ethylene oxide and/or propylene oxide has been added is bonded via an ester bond with (meth)acrylic acid is preferred.

The above (i) polyfunctional (meth)acrylate monomer is an ester bond between a compound having a _-C2-4 alkylene-O- unit and (meth)acrylic acid, and is a compound having both a (meth)acryloyl group and a _-C2-4 alkylene-O- unit in the molecule.
The polyfunctional (meth)acrylate monomer of (i) above is preferably a difunctional (meth)acrylate monomer. Resins containing structural units derived from difunctional (meth)acrylates have relatively excellent flexibility, and therefore have high adhesion to substrates and can prevent peeling.
The number of —C _2-4 alkylene-O— groups per polyfunctional (meth)acrylate monomer of (i) above is preferably 1-30, more preferably 4-30, even more preferably 5-25, and even more preferably 9-25.
Examples of compounds having a _-C2-4 alkylene-O- unit include compounds obtained by binding mono(meth)acrylic acid to (poly)ethylene oxide, (poly)propylene oxide, (poly)tetramethylene glycol, such as ethylene oxide, propylene oxide, ditetramethylene glycol, triethylene oxide, tripropylene oxide, and tritetramethylene glycol. Among these, compounds obtained by binding mono(meth)acrylic acid to (poly)ethylene oxide and/or (poly)propylene oxide are preferred. By further reacting the compound with another (meth)acrylic acid, a polyfunctional, preferably bifunctional (meth)acrylate monomer can be obtained.
Examples of the monomer (i) above include (poly)C2-4 alkylene glycol di(meth)acrylates such as (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, (poly)tetramethylene glycol di(meth)acrylate, and methoxy-(poly) _C2-4 alkylene glycol di(meth)acrylates such as methoxy-(poly)ethylene glycol (meth)acrylate. Of these, (poly) _C2-3 alkylene glycol di( _meth )acrylates ((poly)ethylene glycol di(meth)acrylate and/or (poly)propylene glycol di(meth)acrylate) are preferred, with (poly)ethylene glycol di(meth)acrylate being more preferred.

In this specification and the claims, (poly)ethylene glycol is used as a concept including both one ethylene glycol (monoethylene glycol) and two or more ethylene glycols (diethylene glycol, triethylene glycol, tetraethylene glycol, etc.).
Similarly, (poly)propylene glycol is used as a concept including both one propylene glycol (monopropylene glycol) and two or more propylene glycols (dipropylene glycol, tripropylene glycol, tetrapropylene glycol, etc.).
Similarly, (poly)tetramethylene glycol is used as a concept including both one tetramethylene glycol (monotetramethylene glycol) and two or more tetramethylene glycols (ditetramethylene glycol, tritetramethylene glycol, tetratetramethylene glycol, etc.).
The mass average molecular weight of the monomer (i) is preferably 200 to 1500, more preferably 300 to 1200, even more preferably 400 to 1400, even more preferably 500 to 1300, and even more preferably 600 to 1200.

The polyfunctional (meth)acrylate monomer (ii) above is an ester bond between a trivalent or higher alcohol having a _C2-4 alkylene oxide added thereto and (meth)acrylic acid, and is a compound having both a (meth)acryloyl group and a _-C2-4 alkylene-O- unit in the molecule.
The polyfunctional (meth)acrylate monomer of (ii) above is preferably a trifunctional to hexafunctional (meth)acrylate monomer, more preferably a trifunctional to pentafunctional (meth)acrylate monomer, and even more preferably a trifunctional to tetrafunctional (meth)acrylate monomer. Such polyfunctional (meth)acrylates can increase the curing rate during polymerization and increase the crosslinking density, thereby contributing to improved water resistance.
The number of base units of C _2-4 alkylene oxide (—C _2-4 alkylene-O—) per one polyfunctional (meth)acrylate monomer of (ii) above is preferably 1-30, more preferably 3-30, and even more preferably 3-25.
The trihydric or higher alcohol is preferably at least one selected from the group consisting of glycerin, diglycerin, triglycerin, trimethylolpropane, ditrimethylolpropane, erythritol, pentaerythritol, and dipentaerythritol, more preferably at least one selected from the group consisting of glycerin, diglycerin, trimethylolpropane, ditrimethylolpropane, pentaerythritol, and dipentaerythritol, even more preferably at least one selected from the group consisting of glycerin, pentaerythritol, and trimethylolpropane, and even more preferably at least one selected from the group consisting of glycerin and pentaerythritol.
The tri- or higher hydric alcohol having a C _2-4 alkylene oxide added thereto is preferably a tri- or higher hydric alcohol having a C _2-3 alkylene oxide (ethylene oxide (EO) and/or propylene oxide (PO)) added thereto.
Examples of the monomer (ii) include _C2-4 alkoxylated pentaerythritol tetra(meth)acrylate, _C2-4 alkoxylated glycerin tri(meth)acrylate, _C2-4 alkoxylated trimethylolpropane tri(meth)acrylate, and dipentaerythritol hexaacrylate. Among these, _C2-3 alkoxylated pentaerythritol tetra(meth)acrylate, C2-3 alkoxylated glycerin _tri (meth)acrylate and/or _C2-3 alkoxylated trimethylolpropane tri(meth)acrylate are preferred, and _C2-3 alkoxylated pentaerythritol tetra(meth)acrylate and/or _C2-3 alkoxylated glycerin tri(meth)acrylate are more preferred.

The mass average molecular weight of the monomer (ii) above is preferably 200 to 2000, more preferably 300 to 1500, even more preferably 400 to 1300, and even more preferably 500 to 1200.

The polyfunctional (meth)acrylate monomers (i) and (ii) above are preferably at least one selected from the group consisting of polyethylene glycol diacrylate, polypropylene glycol diacrylate, ethoxylated pentaerythritol tetraacrylate, propoxylated pentaerythritol tetraacrylate, ethoxylated glycerin triacrylate, propoxylated glycerin triacrylate, ethoxylated trimethylolpropane triacrylate, and propoxylated trimethylolpropane triacrylate. It is more preferable that the acrylate is at least one selected from the group consisting of polypropylene glycol diacrylate, ethoxylated pentaerythritol tetraacrylate, propoxylated pentaerythritol tetraacrylate, ethoxylated glycerin triacrylate, and propoxylated glycerin triacrylate, and it is even more preferable that the acrylate is at least one selected from the group consisting of polyethylene glycol diacrylate, ethoxylated pentaerythritol tetraacrylate, propoxylated pentaerythritol tetraacrylate, and ethoxylated glycerin triacrylate.

Specific examples of polyfunctional (meth)acrylate monomers preferably used in the present invention include polyethylene glycol diacrylate ("EBECRYL 11" manufactured by Daicel Allnex Corporation, and "A-1000" manufactured by Shin-Nakamura Chemical Co., Ltd.), C _alkoxylated pentaerythritol tetraacrylate ("EBECRYL 40" manufactured by Daicel Allnex Corporation), and ethoxylated glycerin triacrylate ("A-GLY-20E" manufactured by Shin-Nakamura Chemical Co., Ltd.).

The content of the monomer in a resin containing a structural unit derived from a polyfunctional (meth)acrylate monomer is preferably 30 to 100 parts by mass, more preferably 40 to 100 parts by mass, even more preferably 45 to 100 parts by mass, even more preferably 70 to 100 parts by mass, even more preferably 80 to 100 parts by mass, and may be 100 parts by mass, based on 100 parts by mass of all monomer components constituting the resin. The content of the monomer is also preferably 40 to 60 parts by mass based on 100 parts by mass of all components constituting the resin.

There is no particular restriction on the mass average molecular weight of the resin containing a structural unit derived from a polyfunctional (meth)acrylate monomer, and resins having various mass average molecular weights can be used. For example, the mass average molecular weight of the resin may be 500 to 30,000. If the molecular weight is 500 or more, high hydrophilicity is exhibited, and sufficient durability can be obtained due to the increase in molecular weight upon crosslinking. If the molecular weight is 30,000 or less, uniform coating is possible without excessive increase in viscosity. In addition, the mass average molecular weight of the resin may be 600 to 20,000, or 700 to 15,000.

The polyfunctional (meth)acrylate monomer has two or more polymerizable functional groups. The polyfunctional (meth)acrylate monomer preferably has 2 to 6 polymerizable functional groups, more preferably has 2 to 5 polymerizable functional groups, and further preferably has 2 to 4 polymerizable functional groups.
The polymerizable functional group is preferably an ethylenically unsaturated double bond (an unsaturated double bond between carbon atoms), and more preferably an ethylenically unsaturated double bond (an unsaturated double bond between carbon atoms) present in a (meth)acryloyl group.

In addition, the resin containing the structural unit derived from the polyfunctional (meth)acrylate may further contain a structural unit derived from the urethane (meth)acrylate. By further containing the structural unit derived from the urethane (meth)acrylate, it becomes easier to improve the adhesion and curing property to the light-transmitting resin member. In addition, it becomes easier to suppress swelling caused by the polishing slurry.
The urethane (meth)acrylate is a compound having a urethane bond formed by reacting an isocyanate group with a hydroxyl group, and a (meth)acryloyl group. The urethane (meth)acrylate preferably has two or more polymerizable functional groups, more preferably has two to four polymerizable functional groups, even more preferably has two to three polymerizable functional groups, and even more preferably has two polymerizable functional groups. As the polymerizable functional group, an ethylenically unsaturated double bond (an unsaturated double bond between carbon atoms) is preferable, and an ethylenically unsaturated double bond (an unsaturated double bond between carbon atoms) present in a (meth)acryloyl group is more preferable.
Examples of the urethane (meth)acrylate include aliphatic urethane (meth)acrylate, aromatic urethane (meth)acrylate, etc. In addition, it is preferable that the urethane (meth)acrylate does not have a structure derived from polysiloxane.
The urethane (meth)acrylate can be obtained, for example, by reacting a hydroxy compound having at least two (meth)acryloyl groups with an isocyanate, such as an aliphatic polyisocyanate or an aromatic polyisocyanate.
Aliphatic urethane (meth)acrylates can be obtained, for example, by reacting a hydroxy compound having at least two (meth)acryloyl groups with an aliphatic isocyanate, such as an aliphatic diisocyanate or an aliphatic triisocyanate.
The aromatic urethane (meth)acrylate can be obtained, for example, by reacting a hydroxy compound having at least two (meth)acryloyl groups with an aromatic isocyanate, such as an aromatic diisocyanate or an aromatic triisocyanate.
When the resin containing a structural unit derived from a polyfunctional (meth)acrylate monomer contains a structural unit derived from a urethane (meth)acrylate, the content of the urethane (meth)acrylate is preferably 70 parts by mass or less, more preferably 60 parts by mass or less, and even more preferably 55 parts by mass or less, relative to 100 parts by mass of all monomer components constituting the resin. It is also preferable that the content of the structural unit derived from the urethane (meth)acrylate monomer is 40 to 60 parts by mass, relative to 100 parts by mass of all monomer components of the resin.

The method of coating with a resin containing a structural unit derived from the polyfunctional (meth)acrylate monomer is not particularly limited, and can be carried out, for example, by polymerizing (solution polymerization/photopolymerization) the polyfunctional (meth)acrylate monomer and, if necessary, other monomers or oligomers (preferably acrylic monomers or oligomers) by a conventional method. Among these, photopolymerization is preferred.
When solution polymerization is used, a solution containing the monomer and a polymerization initiator (catalyst or the like) is applied to the surface of the light-transmitting resin member, and during drying, a polymerization reaction progresses, and a coating can be obtained.
When photopolymerization is used, a solution containing the monomer and the like and a photopolymerization initiator is applied to the surface of the light-transmitting resin member, and then the surface is irradiated with ultraviolet light to obtain a coating.
The photopolymerization initiator is not particularly limited as long as it can cure the photocurable resin by irradiation with ultraviolet rays, electron beams, etc., and any conventionally known photopolymerization initiator can be used. For example, radical polymerization initiators, cationic polymerization initiators, anionic polymerization initiators, etc. can be mentioned, and a commercially available product can be Irgacure (manufactured by IGM Resin B.V.).

<Arrangement of light-transmitting resin member>
In the polishing pad of the present invention, when the polishing surface is the upper surface and the opposite surface is the lower surface, the top of the light-transmitting resin member may be at the same height as the polishing surface or lower than the polishing surface, but it is preferable that it is lower than the polishing surface (FIGS. 2 to 4). By having the top of the light-transmitting resin member lower than the polishing surface, it is possible to prevent the occurrence of polishing scratches caused by the light-transmitting resin member, which is harder than the polishing layer. In addition, if the top of the light-transmitting resin member is lower than the polishing surface, the slurry will enter the recess surrounded by the light-transmitting resin member and the side of the through hole, and most of it will move to the side of the through hole by centrifugal force and be discharged through the groove, so that it is easy to cause a small amount of slurry to remain on the surface of the light-transmitting resin member and a case where it does not remain. When a conventional polishing pad is used, there is a difference in light transmittance between a case where a small amount of slurry remains on the surface of the light-transmitting resin member and a case where it does not remain, making it difficult to determine the polishing end point with high accuracy. In contrast, the polishing pad of the present invention has a resin containing a structural unit derived from the polyfunctional (meth)acrylate monomer present on the surface of the polishing surface side of the translucent resin member, which improves compatibility with the slurry, and even when a small amount of slurry is present, the slurry spreads evenly over the window surface, resulting in less variation in light transmittance from the beginning to the end of polishing, and the end point of polishing can be determined with high accuracy even if the top of the translucent resin member is lower than the polishing surface.

(Transmittance)
In the polishing pad of the present invention, the difference between the visible light transmittance (sometimes simply referred to as light transmittance in this specification) when no water is attached to the polishing surface of the translucent resin member and the visible light transmittance when water is attached to the polishing surface of the translucent resin member is preferably within 10%. By having the difference in light transmittance within the above range, the difference in light transmittance between the case where there is a slurry on the surface of the translucent resin member and the case where there is no slurry on the surface of the translucent resin member is unlikely to occur, and the polishing end point can be determined with high accuracy.
The light transmittance can be measured by measuring the transmission spectrum of wavelengths from 300 to 1000 nm with a spectrophotometer, and determining the visible light transmittance (%) according to the Japanese Industrial Standards (JIS A5759:2008). That is, the transmittance is determined by measuring the transmittance at each wavelength in the range of 380 to 780 nm, multiplying the transmittance at each wavelength by a weighting coefficient obtained from the spectral distribution of CIE (Commission Internationale de Illumination) daylight D65, the wavelength distribution and wavelength interval of the CIE photopic standard relative luminous efficiency, and calculating the weighted average.
Furthermore, the measurement of light transmittance when water is applied to the surface of the polished side of the light-transmitting resin member can be performed using the light-transmitting resin member by spraying a sufficient amount of water (for example, about 0.01 to 0.03 mL for a light-transmitting resin member cut into a size of 9 mm x 50 mm) onto the entire surface of the light-transmitting resin member on the polished side, and then draining the water by placing the light-transmitting resin member perpendicular to the ground and leaving it to stand for 60 seconds.

(Through hole)
The through holes are holes that penetrate from the polishing surface to the opposite surface when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad. The through holes preferably penetrate the polishing layer parallel to the thickness direction or perpendicular to the polishing surface.
The polishing layer may have one through-hole, or two or more through-holes that are spaced apart and independent from each other.
The shape of the through hole when viewed from the polishing surface side of the polishing pad in the thickness direction of the polishing pad or the shape of the through hole on the polishing surface may be a circle, an ellipse, a triangle, a rectangle, a hexagon, an octagon, etc. Alternatively, the shape may be a shape in which the same or different multiple shapes partially overlap each other. Among these, a circle is particularly preferred because it does not form corners where polishing debris is likely to accumulate.

(Circle equivalent diameter)
In this specification and the claims, the term "circle equivalent diameter" refers to the diameter of a perfect circle that corresponds to the area of the figure to be measured.
The circular equivalent diameter of the through hole is the circular equivalent diameter of the through hole when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad, and corresponds to the diameter when the shape of the through hole when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad is circular.
The equivalent circle diameter of the through hole is not particularly limited, but is preferably 5 to 40 mm, more preferably 5 to 30 mm, and even more preferably 8 to 28 mm.
The area of the through holes in the polished surface is preferably 0.003 to 0.5% of the total area of the polished surface, more preferably 0.004 to 0.4%, and even more preferably 0.005 to 0.3%.

(Configuration of the polishing layer)
Examples of resins constituting the polishing layer include polyurethane-based resins such as polyurethane and polyurethane polyurea, acrylic-based resins such as polyacrylate and polyacrylonitrile, vinyl-based resins such as polyvinyl chloride, polyvinyl acetate and polyvinylidene fluoride, polysulfone-based resins such as polysulfone and polyethersulfone, acylated cellulose-based resins such as acetylated cellulose and butyrylated cellulose, polyamide-based resins, and polystyrene-based resins. Among these, polyurethane resins are more preferable in terms of compression characteristics and flexibility.
The abrasive layer may be made of one type of resin, or may be made of two or more types of resins.
The polishing layer preferably has open cells. The open cells referred to here refer to foams in which adjacent cells are connected to each other by communicating holes. Specifically, the foam may be made of resin by a wet film-forming method, or by dry molding or injection molding. The wet film-forming method is preferable, as it is expected to allow good bending and stretching movements.
In this specification, the resin by the wet film-forming method means a resin (preferably a polyurethane resin) formed by the wet film-forming method. The wet film-forming method is a method in which the resin to be formed into a film is dissolved in an organic solvent, the resin solution is applied to a sheet-like substrate, and then the resin is passed through a coagulating liquid to coagulate the resin. The resin formed by the wet film-forming method generally has a plurality of teardrop-shaped bubbles (anisotropic, with a structure in which the diameter increases from the polishing surface of the polishing pad to the bottom). Therefore, the resin formed by the wet film-forming method can also be referred to as a resin having a plurality of teardrop-shaped bubbles. The plurality of teardrop-shaped bubbles are preferably in the form of continuous bubbles.
The polishing layer constituting the polishing pad of the present invention is preferably a resin sheet (preferably a polyurethane sheet) formed by a wet film formation method, more preferably a polyurethane sheet containing a plurality of teardrop-shaped bubbles, and even more preferably a polyurethane sheet containing a plurality of teardrop-shaped bubbles and having continuous bubbles in which some or all of the bubbles are connected by communicating holes.

(groove)
The polishing pad of the present invention preferably has grooves formed on the polishing surface of the polishing layer. The grooves do not penetrate the polishing layer and can be distinguished from through-holes.
Examples of the groove include an embossed groove obtained by embossing the polishing surface, and a cut groove obtained by cutting with a cutting tool. Among these, an embossed groove is preferred. By providing a groove such as an embossed groove, it is possible to obtain a polishing pad that is less likely to produce burrs on the polishing surface and is suitable for finish polishing.
The depth of the groove is not particularly limited as long as it is smaller than the thickness of the polishing layer, but it is preferably 50-90% of the thickness of the polishing layer, and more preferably 60-80%. If the groove disappears due to polishing of the object to be polished, the flow and discharge of the polishing slurry is lost, and the polishing performance is reduced, so the polishing pad reaches the end of its life, so the groove depth is preferably deep. On the other hand, in order to increase the groove depth of the embossed groove, it is necessary to increase the processing pressure or the processing temperature, which may cause the substrate (PET) on the back surface of the polishing layer to deform or the surface of the polishing layer to deteriorate. If the depth of the groove is within the above range, these problems are unlikely to occur.
The cross-sectional shape of the groove is not particularly limited, and may be an arc shape, a U-shape, a V-shape, a rectangle, a trapezoid, or other polygonal shape, or a combination of two or more of these shapes. The number and shape of the grooves are also not particularly limited, and may be adjusted appropriately according to the purpose of use of the polishing pad. Examples of shapes include a lattice shape, a radial shape, a concentric circle shape, a honeycomb shape, and the like, and these may be combined.
Furthermore, in the polishing pad of the present invention, the surface of the polishing layer may be opened by grinding (buffing) or may be sliced.

In the polishing pad of the present invention, when the polishing surface is the upper surface and the opposite surface is the lower surface, the uppermost portion 4' of the translucent resin member (i.e., the upper surface of the resin containing a structural unit derived from a polyfunctional (meth)acrylate monomer) may be higher than the lowermost portion 8' of the groove, at the same position as the lowermost portion 8', or at a lower position than the lowermost portion 8', but it is preferable that it is at the same position as the lowermost portion 8' of the groove or at a higher position, and it is more preferable that the uppermost portion 4' of the translucent resin member is at a higher position than the lowermost portion 8' of the groove. In the polishing pad of one embodiment of the present invention (the polishing pad of FIG. 3), the slurry and polishing debris that have entered the recess in the first through hole are moved to the groove by the centrifugal force during polishing, and a decrease in light transmittance can be prevented. Furthermore, even if only a small amount of slurry remains on the surface of the translucent resin member after most of the slurry has moved to the groove, the decrease in light transmittance due to the slurry is unlikely to occur, and stable light detection is possible.

(Shore A hardness)
In this specification, the Shore A hardness refers to a value measured in accordance with Japanese Industrial Standards (JIS K7311).
In the polishing pad of the present invention, the Shore A hardness of the polishing layer is preferably 5 to 70 degrees (°), more preferably 8 to 65 degrees. When the Shore A hardness of the polishing layer is within the above range, excessive contact of polishing debris with the workpiece is suppressed, making it difficult for scratches to occur.
In the polishing pad of the present invention, the polishing layer is preferably softer than the light-transmitting resin member, and more preferably has a lower Shore A hardness than the light-transmitting resin member.

(Compressibility and Compressive Elasticity)
In this specification, the compressibility is an index of softness, and the compressive elastic modulus is an index of the ease of return to normal after compressive deformation.
The compressibility and compressive elastic modulus can be determined using a Chopper-type thickness gauge (pressure surface: circular with a diameter of 1 cm) in accordance with the Japanese Industrial Standards (JIS L1021). Specifically, the method is as follows.
The thickness _t0 is measured after the initial load is applied for 30 seconds from the no-load state, and then the thickness _t1 is measured after the final load is applied for 5 minutes from the thickness _t0 state. Next, all loads are removed from the thickness _t1 state, and the specimen is left for 5 minutes (to be in a no-load state), after which the initial load is again applied for 30 seconds and the thickness _t0 ' is measured.
The compression ratio can be calculated by the formula: compression ratio (%)=100×(t ₀ −t ₁ )/t ₀ (initial load is 100 g/cm ² , final load is 1120 g/cm ² ).
The compressive elastic modulus can be calculated by the formula: compressive elastic modulus (%)=100×(t ₀ '-t ₁ )/(t ₀ -t ₁ ) (initial load is 100 g/cm ² , final load is 1120 g/cm ² ).
The compressibility of the polishing layer is preferably 1 to 60%, more preferably 3 to 50%. The compressive elastic modulus of the polishing layer is preferably 50 to 100%, more preferably 60 to 98%. When the compressibility and compressive elastic modulus are within the above ranges, the polishing layer is compressed when the object to be polished passes over the through-hole, and has excellent recovery after being pressed by the object to be polished. Therefore, the bending and stretching movement of the polishing layer creates a flow of slurry inside the through-hole, and the slurry circulates without remaining in the through-hole, and the polishing waste that enters the through-hole together with the slurry is easily discharged outside the through-hole by the compression and recovery action. This makes it easier to prevent the polishing waste from accumulating in the through-hole.

(Thickness)
The thickness can be measured using a Chopper-type thickness measuring instrument (pressure surface: circular with a diameter of 1 cm) in accordance with the Japanese Industrial Standards (JIS K6505). Specifically, the thickness is measured as follows.
Prepare a sample that is 10 cm square by 10 cm long. Place the sample on the measuring device with the surface facing up. Place a pressure surface with a load of 100 g/ ^cm2 on the sample and measure the thickness after 5 seconds. Measure 5 points on each sheet and take the average thickness. If a 10 cm square sample cannot be obtained, use the average of the 5 points.
There is no particular limitation on the thickness of the polishing layer, but it is preferably 0.5 to 2 mm, and more preferably 0.75 to 1.55 mm.

(Layers other than the polishing layer)
The polishing pad of the present invention may have a layer (another layer) other than the polishing layer. The other layer may be present in one or more layers on the surface opposite to the polishing surface of the polishing layer. The other layer has through holes like the polishing layer.
The through holes of the polishing layer and the other layers may have the same or different shapes, but it is preferable that the through holes of the polishing layer and the other layers at least partially overlap when the polishing pad is viewed in the thickness direction from the polishing surface side, so that when light is irradiated onto the light-transmitting resin member, the light passes through the light-transmitting resin member.

In one embodiment of the present invention, when the polishing pad has another layer, the polishing pad may have another layer having a through hole (second through hole) having a smaller circle equivalent diameter than the through hole (first through hole) present in the polishing layer (FIG. 3). The other layer is a layer located on the opposite side of the polishing surface of the polishing layer.
In the polishing pad of this aspect, it is preferable that the first through hole and the second through hole at least partially overlap when viewed in the thickness direction from the polishing surface side of the polishing pad, and the light-transmitting resin member is preferably disposed so that the light-transmitting resin member is present in the first through hole when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad.

In this embodiment of the polishing pad, when viewed in the thickness direction from the polishing surface side of the polishing pad, it is preferable that the outer periphery of the first through hole 5 is arranged to cover part or all of the outer periphery of the second through hole 6, it is more preferable that the outer periphery of the first through hole 5 is arranged to cover the entire outer periphery of the second through hole 6, and it is even more preferable that both the first through hole 5 and the second through hole 6 are cylindrical and that the cylindrical central axis of the first through hole 5 and the cylindrical central axis of the second through hole 6 coincide (see Figure 3).
When the outer periphery of the first through hole covers the entire outer periphery of the second through hole, it means that the diameter of the first through hole 5 is larger than the diameter of the second through hole 6, and the outer periphery of the first through hole 5 exists outside the outer periphery of the second through hole 6, as shown in a double circle.

Here, when viewed in the thickness direction from the polishing surface side, the first through hole and the second through hole at least partially overlap means that when viewed in the thickness direction from the polishing surface side, the opening position of the first through hole and the opening position of the second through hole at least partially coincide. In this embodiment of the polishing pad, when viewed in the thickness direction, the opening position of the first through hole and the opening position of the second through hole at least partially coincide, so that the first through hole and the second through hole are connected in the thickness direction of the polishing pad. Since the positions of the first through hole and the second through hole at least partially overlap when viewed in the thickness direction from the polishing surface side, light can be transmitted from the second through hole side to the first through hole side through the translucent resin member provided in the first through hole, and the surface condition of the polished object during polishing can be optically detected.

In the polishing pad of this embodiment, when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad, the light-transmitting resin member 4 is preferably disposed so that the light-transmitting resin member 4 is present in the first through hole 5. In addition, the light-transmitting resin member 4 is preferably provided in the first through hole 5.
Here, when the light-transmitting resin member is arranged so that it is present within the first through hole when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad, this means that the light-transmitting resin member can be confirmed when viewing inside the first through hole in the thickness direction of the polishing pad from the polishing surface side of the polishing pad.
In addition, the first through hole 5 is preferably arranged so that a part of the other layer 3 (hereinafter, referred to as the exposed portion 7 of the other layer) and at least a part of the second through hole 6 are exposed when the polishing pad 1 is viewed in the thickness direction from the polishing surface side. This allows the translucent resin member 4 to be disposed in the first through hole 5 and on the second through hole 6 and the exposed portion 7 of the other layer 3. Preferably, the first through hole 5 is arranged so that a part of the other layer 3 and all of the second through hole 6 are exposed when the first through hole 5 is viewed from the polishing surface side. In addition, the translucent resin member 4 is preferably provided in the first through hole 5 and bonded to the exposed portion 7 of the other layer 3.
3, in the thickness direction cross section of the polishing pad 1 of the present invention, the first through hole 5 is provided in the polishing layer 2 on the second through hole 6 and the exposed portion 7. An additional layer may be provided between the polishing layer 2 and the other layer 3 having the exposed portion 7. In this case, it is preferable that the through hole in the additional layer has the same cross-sectional shape (cross-sectional shape in a horizontal direction to the polishing surface) as the through hole (first through hole) of the polishing layer 2, and completely overlaps with the first through hole 5 when viewed in the thickness direction from the polishing surface. It is preferable that the light-transmitting resin member 4 is disposed on the second through hole 6 and the exposed portion 7, and inside the first through hole 5 of the polishing layer 2 and the through hole of the additional layer.

The second through hole may be provided in one other layer, or two or more through holes that are spaced apart and independent from each other may be provided. It is preferable that the number of first through holes is equal to the number of second through holes. When multiple first through holes and multiple second through holes are provided, it is preferable that each first through hole is provided on each second through hole provided in the other layer and its exposed portion.

The second through holes preferably penetrate the other layer parallel to the thickness direction or perpendicular to the polishing surface.
In the polishing pad of the present invention, the cross-sectional shape of the first through hole and the cross-sectional shape of the second through hole when cut perpendicular to the thickness direction may be the same or different, but it is preferable that they have the same shape.
The shape of the second through hole when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad, the cross-sectional shape of the second through hole when cut perpendicularly to the thickness direction of the polishing pad, and/or the shape of the second through hole on the surface of the other layer may be a circle, an ellipse, a triangle, a rectangle, a hexagon, an octagon, or a combination of these shapes. Alternatively, the shape may be a shape in which the same or different multiple shapes partially overlap each other. Among these, a circle is particularly preferable.

(Circle equivalent diameter)
In this specification and claims, the circle equivalent diameter of the second through hole is the circle equivalent diameter of the second through hole when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad, and corresponds to the diameter when the shape of the second through hole when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad is circular.
The circle-equivalent diameter of the first through hole is preferably larger than the circle-equivalent diameter of the second through hole. As long as the circle-equivalent diameter of the first through hole is larger than the circle-equivalent diameter of the second through hole, there is no particular restriction on the circle-equivalent diameter of the second through hole, but the circle-equivalent diameter of the second through hole is preferably 1 to 20 mm, more preferably 2 to 18 mm, and even more preferably 5 to 15 mm. In addition, there is no particular restriction on the difference between the circle-equivalent diameter of the first through hole and the circle-equivalent diameter of the second through hole, but the circle-equivalent diameter of the first through hole is preferably 5 to 30 mm larger than the circle-equivalent diameter of the second through hole, more preferably 6 to 25 mm larger, and even more preferably 7 to 20 mm larger.
Furthermore, when viewed in the thickness direction from the polishing surface side of the polishing pad, the outer periphery of the first through hole is arranged to cover the entire outer periphery of the second through hole, and the circle equivalent diameter of the first through hole is preferably 5 to 30 mm larger than the circle equivalent diameter of the second through hole, more preferably 6 to 25 mm larger, and even more preferably 7 to 20 mm larger.
Furthermore, when viewed in the thickness direction from the polishing surface side of the polishing pad, the outer periphery of the first through hole is arranged to cover the entire outer periphery of the second through hole, and the circular equivalent diameter of the first through hole is preferably 1.5 to 4 times the circular equivalent diameter of the second through hole, more preferably 2 to 4 times, and even more preferably 2 to 3 times.

Furthermore, when viewed from the polishing surface side of the polishing pad in the thickness direction of the polishing pad, it is preferable that the shortest distance between the outer periphery of the second through hole and the outer periphery of the first through hole (i.e., the shortest distance between any point on the outer periphery of the second through hole and any point on the outer periphery of the first through hole) is greater than 0, it is more preferable that the shortest distance is 2 to 15 mm, it is even more preferable that the shortest distance is 3 to 12 mm, and it is even more preferable that the shortest distance is 4 to 10 mm.
When the difference in size between the first through hole and the second through hole is within the above range, the slurry and polishing debris that have entered the recess in the first through hole are moved to the outer periphery of the first through hole by the centrifugal force during polishing and are difficult to see from the second through hole with a smaller circle equivalent diameter, so that it is possible to prevent the polishing debris from blocking the light path when light is irradiated onto the translucent resin member. Therefore, it is possible to maintain excellent light transmittance and obtain a stable signal strength for end point detection during polishing. In addition, since the area of the exposed portion is sufficiently large, it is possible to maintain the adhesive strength between the translucent resin member and other layers and prevent the translucent resin member from peeling off.
Furthermore, even if most of the slurry migrates to the side of the recess and only a small amount of slurry remains on the surface of the translucent resin member, the polishing pad of the present invention is less likely to experience variations in light transmittance due to the presence or absence of slurry, making stable light detection possible.

In another embodiment, when the polishing pad of the present invention includes another layer, a sheet-like light-transmitting resin member may be sandwiched between the polishing layer and the other layer, and a part of the light-transmitting resin member may be exposed in the through-hole (FIG. 4). In this case, when viewed in the thickness direction from the polishing surface side, it is preferable that the through-hole (second through-hole) in the other layer and the through-hole (first through-hole) in the polishing layer at least partially overlap, and more preferably completely overlap. In this case, it is preferable that the polishing layer has continuous cells with communicating holes.
When the polishing layer has open cells with communicating holes, the open cells also open on the side of the first through holes provided in the polishing layer, and some of them communicate with the polishing surface or the groove region. As a result, the slurry and polishing debris that enter the first through holes during polishing moves to the side of the first through holes by the centrifugal force generated during polishing and is discharged to the polishing surface or the groove region through the open cells with communicating holes, which prevents a decrease in light transmittance over time due to the polishing debris accumulating in the first through holes, leading to a longer life for the polishing pad.

(Configuration of other layers)
Examples of materials constituting the other layer include polyolefin-based sheets such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymers, polyester-based sheets such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN), vinyl chloride-based sheets, vinyl acetate-based sheets, polyimide-based sheets, polyamide-based sheets, fluororesin-based sheets, resin-impregnated nonwoven fabrics, nonwoven fabrics, and woven fabrics. The other layer is preferably a non-porous sheet into which the slurry does not penetrate. Among these, the other layer is more preferably a polyester-based sheet, which is a non-porous sheet into which the slurry does not penetrate, from the viewpoint of physical properties (e.g., dimensional stability, thickness accuracy, processability, tensile strength), and economic efficiency, and among these, a sheet made of polyethylene terephthalate (hereinafter abbreviated as PET) is particularly preferred.
As a method for bonding the other layer to the polishing layer or the other layer to another other layer, for example, a sheet such as a PET sheet coated with an adhesive on one or both sides can be used as the other layer, and the other layer can be bonded to the polishing layer or the other other layer via the adhesive. It is also possible to prepare a sheet such as a PET sheet not coated with an adhesive as the other layer, and separately prepare the polishing layer or the other other layer and an adhesive, and bond the other layer to the polishing layer or the other other layer via the adhesive.

(advantage)
In the polishing pad of the present invention, at least the polishing surface side of the light-transmitting member has a resin containing a constitutional unit derived from a polyfunctional (meth)acrylate monomer, so that the wettability with respect to the slurry is improved, and the light transmittance hardly changes depending on the presence or absence of the slurry on the polishing surface side of the light-transmitting member, which allows the polishing end point to be determined with high accuracy.
In addition, when the polishing surface is the upper surface and the opposite surface is the lower surface, the polishing pad of the present invention exerts its effect whether the surface of the polishing surface of the light-transmitting member is at the same height as the polishing surface or at a lower position than the polishing surface, but it exerts its effect more when the surface of the polishing surface of the light-transmitting member is at a lower position than the polishing surface. That is, when the surface of the polishing surface of the light-transmitting member is at a lower position than the polishing surface, a recess (for example, a cylindrical recess) surrounded by the surface of the light-transmitting member and the side of the through hole is present, and the slurry enters into this recess. Since most of the slurry that enters into the recess is moved to the side by the influence of centrifugal force and can be discharged through the embossed groove, there may be times when the slurry is present in the area of the surface of the light-transmitting member through which the laser light passes (time when a lot of slurry flows into the recess or time when it cannot be discharged, etc.) and times when it is not present. The polishing pad of the present invention contains a resin containing a structural unit derived from the polyfunctional (meth)acrylate monomer on the surface of the polishing surface side of the light-transmitting member, thereby reducing the variation in light transmittance that occurs between when slurry is attached and when it is not attached, thereby suppressing variations in light transmittance during polishing processing.
In addition, in the polishing pad of the present invention, the translucent resin member has a resin containing a structural unit derived from a polyfunctional (meth)acrylate monomer on at least the surface on the polishing side, and therefore has high chemical resistance and can prevent deterioration of the translucent resin member whether an acidic slurry or an alkaline slurry is used.
The polishing pad of the present invention can be produced, for example, by the following method.

<<Method of manufacturing polishing pad>>
The manufacturing method of the present invention is a method for manufacturing a polishing pad, comprising the steps of: preparing a polishing layer; and a light-transmitting resin member having on at least one surface a resin that contains a structural unit derived from a polyfunctional (meth)acrylate monomer having two or more polymerizable functional groups and that contains a _-C2-4 alkylene-O- unit; providing a through hole in the polishing layer; and arranging the light-transmitting resin member so that the light-transmitting resin member is present in the through hole when viewed from the polishing surface side of the polishing pad in the thickness direction of the polishing pad (wherein the surface of the light-transmitting resin member having the resin that contains a structural unit derived from the polyfunctional (meth)acrylate monomer is arranged so that it faces the polishing surface).
Each step will be described.

<1. Step of preparing a polishing layer and a light-transmitting resin member having, on at least one surface thereof, a resin containing a structural unit derived from a polyfunctional (meth)acrylate monomer having two or more polymerizable functional groups and having a _—C2-4 alkylene-O— unit>
In this step, a light-transmitting resin member having on at least one surface a resin containing a structural unit derived from a polyfunctional (meth)acrylate monomer having two or more polymerizable functional groups and having a _-C2-4 alkylene-O- unit, and a polishing layer are prepared.
The above-mentioned materials can be used as the polishing layer, the light-transmitting resin member, and the resin containing a structural unit derived from a polyfunctional (meth)acrylate monomer. The polishing layer and the light-transmitting resin member may be commercially available or manufactured. Commercially available light-transmitting resin members include Mitsubishi Chemical Corporation's "Diafoil T910E" and "Diafoil T600E" made of polyester resin, Toyobo Co., Ltd.'s "Cosmoshine A4300", "Cosmoshine A2330", "Cosmoshine TA017", "Cosmoshine TA015", "Cosmoshine TA042", "Cosmoshine TA044", "Cosmoshine TA048", and "Soft Shine TA009", Mitsubishi Chemical Corporation's "Acryplene HBXN47" and "Acryplene HBS010" made of polymethyl methacrylate resin, and Teijin Chemical Co., Ltd.'s "Panlite Film PC-2151". , "SUNDUREN SD009" and "SUNDUREN SD010" manufactured by Kaneka Corporation, "C000" manufactured by Sumitomo Chemical Co., Ltd. made of polycarbonate resin, "Iupilon H-3000" manufactured by Teijin Chemical Co., Ltd., "C001" manufactured by Sumitomo Chemical Co., Ltd. made of acrylic resin/polycarbonate resin, "S000", "S001G", and "S014G" manufactured by Sumitomo Chemical Co., Ltd. made of acrylic resin, "ACRYPLEN HBS006" manufactured by Mitsubishi Chemical Corporation, "ZEONOR ZF14" and "ZEONOR ZF16" manufactured by Zeon Corporation made of alicyclic polyolefin resin, "ARTON FILM" manufactured by JSR Corporation, and the like can be obtained as commercially available products. When manufacturing the polishing layer, for example, it can be manufactured by wet-forming a polyurethane resin with reference to Patent No. 5421635 and Patent No. 5844189, and laminating it with a flexible sheet made of PET resin.

The manufacturing method of the present invention may further include a step of coating at least one surface of the light-transmitting resin member with a resin containing a constitutional unit derived from a polyfunctional (meth)acrylate monomer.
There is no particular limitation on the method for coating at least one surface of the light-transmitting resin member with the resin. For example, the resin can be coated on the surface of the light-transmitting resin member by utilizing a polymerization reaction or a photocuring reaction.
When using a photocuring reaction, the resin may be mixed with a photocurable resin and a photopolymerization initiator, applied to the surface of a light-transmitting resin member, and then cured by irradiating with ultraviolet light, etc. Examples of the photocurable resin and photopolymerization initiator include those mentioned above.
Therefore, the manufacturing method of the present invention may further include a step of applying a mixture containing a monomer component including a polyfunctional (meth)acrylate monomer and a photopolymerization initiator onto a light-transmitting resin member, and a step of photopolymerizing the mixture.

<2. Step of Providing Through Holes in the Polishing Layer>
In this step, a through hole is provided in the polishing layer. The through hole is a hole that penetrates from the polishing surface of the polishing layer to the opposite surface. For example, the method of providing a through hole in the polishing layer can be provided by using a die having a circular, elliptical, polygonal shape, etc. (preferably a circular die) to open a hole in the thickness direction of the polishing layer. By using a die, the circle equivalent diameter of the through hole in any polishing layer cross section obtained by cutting the polishing layer of the polishing pad perpendicularly to the thickness direction can be made the same as the circle equivalent diameter of the through hole in any other polishing layer cross section.

<3. Step of arranging the light-transmitting resin member so that the light-transmitting resin member is present in the through-hole when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad>
In this step, the light-transmitting resin member is disposed so that it is present in the through-hole when viewed from the polishing surface side of the polishing pad in the thickness direction of the polishing pad, and the surface of the light-transmitting resin member having the resin containing the constitutional unit derived from the polyfunctional (meth)acrylate monomer faces the polishing surface.
The method of arranging the light-transmitting resin member so that it is present in the through-hole includes, for example, (1) a method of arranging the light-transmitting resin member so that it is in contact with (or bonded to) the side of the through-hole provided in the polishing layer as shown in Fig. 2, (2) a method of arranging the light-transmitting resin member so that it is visible in the through-hole by providing another layer having a through-hole with a smaller circle equivalent diameter under the polishing layer as shown in Fig. 3, and arranging the light-transmitting resin member on the exposed part resulting from the difference in size between the through-hole of the polishing layer and the through-hole of the other layer, and (3) a method of sandwiching the light-transmitting resin member between the polishing layer and the other layer and exposing a part of the light-transmitting resin member in the through-hole as shown in Fig. 4. Among these, (1) or (2) is preferable, and (2) is more preferable.

In addition, the manufacturing method of the present invention may have a step of preparing a layer other than the polishing layer, or a step of bonding a layer other than the polishing layer (another layer) and the polishing layer. The other layer has a through hole that is the same as or different from the through hole of the polishing layer. The through hole in the other layer may be provided before bonding the other layer to the polishing layer, or may be provided after bonding the other layer to the polishing layer. The other layer and the through hole may be the same as those described above.
The manufacturing method of the present invention may also include a step of providing a second through hole in another layer, the second through hole having a smaller circle equivalent diameter than the through hole (first through hole) in the polishing layer.

When the polishing pad of the present invention is used, the polishing pad is attached to the polishing platen of a polishing machine so that the polishing surface of the polishing layer faces the workpiece, and the polishing platen is rotated while supplying the slurry to polish the processed surface of the workpiece.
Examples of objects to be polished with the polishing pad of the present invention include bare silicon and semiconductor devices. Among these, the polishing pad of the present invention is suitable for polishing semiconductor devices, particularly finish polishing, and is therefore preferred.
The slurry may be any slurry containing water (aqueous slurry) without any particular limitation, and examples thereof include colloidal silica slurry and cerium oxide slurry.

By using the polishing pad of the present invention, for example, during the CMP polishing process, a light beam is irradiated onto the wafer through the polishing pad via the translucent resin member in the through hole, and the interference signal generated by the reflection is monitored, so that while polishing the workpiece, the surface characteristics of the workpiece, such as a semiconductor wafer, and the point at which the workpiece reaches a flat state can be optically detected.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

Example 1
50 parts by mass of an aliphatic urethane acrylate ("EBECRYL 2000" manufactured by Daicel Allnex Corporation) and 50 parts by mass of a polyethylene glycol diacrylate ("EBECRYL 11" manufactured by Daicel Allnex Corporation, mass average molecular weight 700, number of ethylene oxide units per monomer: 13) were mixed, and 5 parts by mass of a photopolymerization initiator ("IRGACURE 184" manufactured by BASF Corporation) were added and mixed uniformly using a mixing stirrer to obtain a resin composition. The obtained resin composition was applied uniformly to one side of an acrylic resin sheet (Kurarex S manufactured by Nitto Plastics Co., Ltd., thickness 400 μm) using a bar coater. The sheet was then left in an oven maintained at 50 ° C. for 10 minutes and dried. After drying, the sheet was subjected to a UV irradiation of 900 mJ/cm using an 80 W/cm metal halide lamp. The resin composition was cured by irradiating it with ultraviolet light of ^{No. 2} to form a surface layer having a thickness of 3.5 μm. The obtained acrylic resin sheet with the surface layer was used as an end point detection window.

Example 2
58 parts by weight of polyethylene glycol diacrylate ("A-1000" manufactured by Shin-Nakamura Chemical Co., Ltd., weight average molecular weight 1140, number of ethylene oxide units per monomer: 23), 39 parts by weight of C _2-3 alkoxylated pentaerythritol tetraacrylate ("EBECRYL40" manufactured by Daicel Allnex Corporation, weight average molecular weight 571, number of ethylene/propylene oxide units per monomer: 4), 3 parts by weight of photopolymerization initiator ("IRGACURE184" manufactured by BASF Corporation), and 100 parts by weight of propylene glycol monomethyl ether as a solvent were uniformly mixed using a mixing stirrer to obtain a resin composition. The obtained resin composition was applied to an acrylic resin sheet in the same manner as in Example 1 to form a surface layer, which was used as an end point detection window.

Example 3
67 parts by mass of ethoxylated glycerin triacrylate ("A-GLY-20E" manufactured by Shin-Nakamura Chemical Co., Ltd., weight average molecular weight 1134, number of ethylene oxide units per monomer: 20), 28 parts by mass of C _2-3 alkoxylated pentaerythritol tetraacrylate ("EBECRYL40" manufactured by Daicel Allnex Corporation, weight average molecular weight 571, number of ethylene/propylene oxide units per monomer: 4), 5 parts by mass of photopolymerization initiator ("IRGACURE184" manufactured by BASF Corporation), and 100 parts by mass of propylene glycol monomethyl ether as a solvent were uniformly mixed using a mixing stirrer to obtain a resin composition. The obtained resin composition was applied to an acrylic resin sheet in the same manner as in Example 1 to form a surface layer, which was used as an end point detection window.

<Comparative Example 1>
A commercially available acrylic resin sheet (Kurarex S, thickness 400 μm, manufactured by Nitto Resin Industries Co., Ltd.) was used as the end point detection window.

<Water contact angle measurement>
Using a contact angle meter (DropMaster 500, manufactured by Kyowa Interface Science Co., Ltd.), one drop of water (2 μL) was dropped from a syringe needle, and the contact angle was measured after 3 seconds.
The water contact angle of the surface was measured by the above method, and a water contact angle that was 40 degrees or more lower than that before the formation of the surface layer was evaluated as ◯ or ×. The results are shown in Table 1.

<Light transmittance measurement>
The visible light transmittance of the light-transmitting resin members of Examples 1 to 3 and Comparative Example 1 was measured by the following method using an ultraviolet, visible, and near-infrared spectrophotometer V-770 (manufactured by JASCO Corporation).
1. Measurement when water is attached (1) Insert a quartz glass cell and measure the blank.
(2) The light-transmitting resin members of Examples 1 to 3 and Comparative Example 1 were cut into pieces measuring 9 mm x 50 mm.
(3) The light-transmitting resin member is placed on a paper rag (Kimtowel, manufactured by Nippon Paper Crecia Co., Ltd.), and purified water is sprayed three times from a distance of 20 cm onto the surface of the light-transmitting resin member (only the coated surface for Examples 1 to 3, and only one surface for Comparative Example 1) using a spray bottle (50 mL capacity, PP bottle) (amount sprayed per time: 0.160 to 0.165 mL, amount of water attached to the light-transmitting resin member surface: 0.01 to 0.03 mL). After spraying, the light-transmitting resin member is placed vertically and left to stand for 60 seconds. The light-transmitting resin member is placed in the quartz glass cell so that the surface not sprayed with water comes into contact with the inner surface of the quartz glass cell.
(3) The light-transmitting resin member is placed on the inner wall of the quartz glass cell so that the surface with the coating film of the light-transmitting resin member faces away from the light source and is in full contact with the light source side of the quartz glass cell.
(4) Using an ultraviolet, visible and near infrared spectrophotometer V-770 (manufactured by JASCO Corporation), the rectilinear transmittance for light of 250 to 1000 nnl is measured.
(5) Calculate the visible light transmittance for wavelengths of 380 to 780 nm based on J ISA 5759:2008.

2. Measurement when no water is attached (1) Insert a quartz glass cell and measure the blank.
(2) The light-transmitting resin members of Examples 1 to 3 and Comparative Example 1 were cut into pieces measuring 9 mm x 50 mm.
(3) The light-transmitting resin member is placed on the inner wall of the quartz glass cell so that the surface with the coating film of the light-transmitting resin member faces away from the light source and is in full contact with the light source side of the quartz glass cell.
(4) Using a UV-Vis-NIR spectrophotometer V-770 (manufactured by JASCO Corporation), the rectilinear transmittance for light of 250 to 1000 nm is measured.
(5) Calculate the visible light transmittance for wavelengths of 380 to 780 nm based on J ISA 5759:2008.

Using the above method, the difference between the visible light transmittance when water was attached to the surface and when water was not attached (visible light transmittance without water attached minus visible light transmittance with water attached) was determined for the light-transmitting resin members of Examples 1 to 3 and Comparative Example 1, and those with a difference in light transmittance of 10% or less were rated as ○, and those with a difference of more than 10% were rated as ×. The results are shown in Table 1.

<Chemical resistance evaluation>
Samples of Examples 1 to 3 measuring 15 mm x 15 mm were immersed in acidic slurry/alkaline slurry at 40°C for 24 hours, then removed and the moisture on the surface was wiped off with a paper cloth (Kimtowel, manufactured by Nippon Paper Crecia Co., Ltd.) and the condition of the surface layer was observed. Cases where no peeling or distortion was visually confirmed were evaluated as ◯. The following acidic and alkaline slurries were used. The results are shown in Table 1.
Acidic slurry: Potassium permanganate-based slurry (FUJIMI: DSC-201), pH 2
Alkaline slurry: colloidal silica slurry (Cabot Corporation slurry: SS25, containing KOH), pH 11

As a result of the test, in Comparative Example 1, which does not have a surface layer of resin containing a structural unit derived from a polyfunctional (meth)acrylate monomer on the polishing surface side, there was a large difference in visible light transmittance between the presence and absence of water on the surface. In contrast, in Examples 1 to 3, which have a surface layer of the resin on the polishing surface side, the difference in visible light transmittance between the presence and absence of water on the surface was reduced compared to Comparative Example 1, and there was almost no difference in visible light transmittance between the presence and absence of water on the surface. Therefore, the polishing pads containing the light-transmitting resin members of Examples 1 to 3 do not vary in visible light transmittance between the presence and absence of slurry on the surface, and the polishing end point can be determined with higher accuracy.

<Production Example 1>
To 100 parts by mass of a solution containing a polyester polyurethane resin (30 parts by mass) with a 100% modulus of 7.8 MPa and DMF (70 parts by mass), 60 parts by mass of DMF and 5 parts by mass of water were added and mixed to obtain a resin-containing solution. The obtained resin-containing solution was filtered to remove insoluble components. The solution was cast onto a polyester film using a knife coater so that the coating thickness was 0.81 mm. Thereafter, the polyester film on which the resin-containing solution was cast was immersed in a coagulation bath (coagulation liquid was water) to coagulate the resin-containing solution, and then the polyester film was peeled off, washed and dried to obtain a polyurethane resin film having a plurality of teardrop-shaped bubbles inside and the plurality of bubbles connected to each other and communicating with each other. The surface of the obtained polyurethane resin film was buffed to a thickness of 0.73 mm, and then a PET resin substrate having a thickness of 0.188 mm was bonded to the opposite side of the buffed surface with an adhesive, and the polyurethane resin film was embossed from the surface side to provide a rectangular cross-sectional lattice pattern groove with a groove width of 1 mm, a groove interval of 4 mm, and a groove depth of 0.45 mm on the surface. Three holes were drilled at equal intervals with a circular die having a diameter of 18 mm on a concentric circle at a position that is 1/2 the radius of the polishing pad from the center of the polishing pad on the groove-treated surface side to provide a first through hole. A double-sided tape having a release paper on one side was adhered to the surface of the resin substrate to which the polyurethane resin film was not bonded, and a circular die having a diameter of 9 mm was fitted into the first through hole having a diameter of 18 mm, and a second through hole was opened so as to penetrate the double-sided tape and the release paper. At this time, the holes were drilled so that the center of the first through hole and the center of the second through hole were approximately the same. As the light-transmitting member, the acrylic resin sheet with the surface layer of Example 1 was prepared and cut into three pieces with a diameter of 17 mm. The double-sided tape exposed in a ring shape in the first through hole and the light-transmitting member were attached so that the surface-treated side of the light-transmitting member became the polishing surface to produce a polishing pad.

<Production Example 2>
To 100 parts by mass of a solution containing a polyester polyurethane resin (30 parts by mass) with a 100% modulus of 7.8 MPa and DMF (70 parts by mass), 60 parts by mass of DMF and 5 parts by mass of water were added and mixed to obtain a resin-containing solution. The obtained resin-containing solution was filtered to remove insoluble components. The solution was cast onto a polyester film using a knife coater so that the coating thickness was 0.81 mm. Thereafter, the polyester film on which the resin-containing solution was cast was immersed in a coagulation bath (coagulation liquid was water) to coagulate the resin-containing solution, and then the polyester film was peeled off, washed and dried to obtain a polyurethane resin film having a plurality of teardrop-shaped bubbles inside and the plurality of bubbles connected to each other and communicating with each other. The surface of the obtained polyurethane resin film was buffed to a thickness of 0.73 mm, and then a PET resin substrate having a thickness of 0.188 mm was bonded to the opposite side of the buffed surface with an adhesive, and the polyurethane resin film was embossed from the front side to provide a rectangular cross-sectional lattice pattern groove with a groove width of 1 mm, a groove interval of 4 mm, and a groove depth of 0.45 mm on the surface. A double-sided tape having a thickness of about 0.1 mm (PET substrate thickness 0.023 mm, adhesive component thickness on the front and back sides of the PET substrate both 0.04 mm) with a release paper on one side was bonded to the side of the resin substrate to which the polyurethane resin film was not bonded. Three holes were made at equal intervals with a circular die having a diameter of 9 mm on a concentric circle from the center of the polishing pad on the groove-treated surface side to a position that is 1/2 the radius of the polishing pad, so as to penetrate to the release paper of the double-sided tape, to provide a first through hole. The release paper of the double-sided tape is peeled off, and the acrylic resin sheet with the surface layer of Example 1 cut to the same size as the polishing layer is prepared as a light-transmitting member, and the adhesive part of the double-sided tape is attached to the surface layer side of the acrylic resin sheet. As another layer, a double-sided tape with a thickness of about 0.11 mm (PET base material thickness 0.023 mm, adhesive component thickness on the front and back sides of the PET base material are both 0.04 mm) having a release paper on one side is prepared, and a second through hole is provided by opening three holes with a diameter of 9 mm at the position overlapping with the first through hole when viewed in the thickness direction, and the polishing pad is manufactured by adhering to the surface side without the coating film of the acrylic resin film light-transmitting member.

The polishing pads of Production Examples 1 and 2 have light transmittance that does not vary significantly depending on whether or not an aqueous slurry is present, making it possible to detect the polishing end point with high accuracy.

The present invention provides a polishing pad that can suppress variations in light transmittance. Therefore, the polishing pad of the present invention is extremely useful industrially.

1... polishing pad 2... polishing layer 3... other layer 4... light-transmitting resin member 4'... uppermost part of light-transmitting resin member 5... through hole (first through hole)
6: second through hole 7: exposed portion 8: groove 8': lowest portion of groove 9: surface portion on the polished surface side of the light-transmitting resin member

Claims (12)

A polishing pad having a light-transmitting resin member and a polishing layer,
the polishing layer has a polishing surface for polishing an object to be polished, and the polishing pad has a through hole extending from the polishing surface to an opposite surface thereof;
the light-transmitting resin member is disposed so as to be present in the through-hole when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad, and the light-transmitting resin member has a resin containing a constitutional unit derived from a polyfunctional (meth)acrylate monomer having two or more polymerizable functional groups and having a _-C2-4 alkylene-O- unit, at least on the surface of the polishing surface side of the polishing pad.
The polishing pad. The polyfunctional (meth)acrylate monomer is selected from the group consisting of:
The polishing pad according to claim 1, which is at least one selected from the group consisting of a monomer in which a compound having a _-C2-4 alkylene-O- unit and (meth)acrylic acid are ester-bonded, and a monomer in which a trihydric or higher alcohol to which a _C2-4 alkylene oxide has been added is ester-bonded with (meth)acrylic acid. The polishing pad according to claim 2, wherein the trihydric or higher alcohol is selected from the group consisting of glycerin, diglycerin, triglycerin, trimethylolpropane, ditrimethylolpropane, erythritol, pentaerythritol, and dipentaerythritol. 4. The polishing pad according to claim 1, wherein the -C _2-4 alkylene-O- units are derived from ethylene oxide and/or propylene oxide. The polishing pad according to any one of claims 1 to 4, wherein the polyfunctional (meth)acrylate monomer is at least one selected from the group consisting of polyethylene glycol diacrylate, polypropylene glycol diacrylate, ethoxylated pentaerythritol tetraacrylate, propoxylated pentaerythritol tetraacrylate, ethoxylated glycerin triacrylate, propoxylated glycerin triacrylate, ethoxylated trimethylolpropane triacrylate, and propoxylated trimethylolpropane triacrylate. The polishing pad according to any one of claims 1 to 5, in which, when the polishing surface is the upper surface and the opposite surface is the lower surface, the surface of the polishing surface side of the translucent resin member is lower than the polishing surface. The polishing pad according to any one of claims 1 to 6, wherein the polishing surface has grooves. The polishing pad of claim 7, wherein the grooves are embossed grooves. The polishing pad according to claim 7 or 8, in which, when the polishing surface is the upper surface and the opposite surface is the lower surface, the surface of the polishing surface of the translucent resin member is at the same position as or higher than the lowest part of the groove. The polishing pad according to any one of claims 1 to 9, wherein the through holes have a circular shape when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad. When the through hole of the polishing layer is defined as a first through hole, the polishing pad further includes another layer having a second through hole having a smaller circle equivalent diameter than the first through hole,
The other layer is located on the opposite side to the polishing surface of the polishing layer,
When the polishing pad is viewed in a thickness direction from a polishing surface side, the first through hole and the second through hole at least partially overlap each other,
The polishing pad according to any one of claims 1 to 10, wherein the translucent resin member is arranged so that the translucent resin member is present within the first through hole when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad. A step of preparing a polishing layer and a light-transmitting resin member having, on at least one surface thereof, a resin containing a structural unit derived from a polyfunctional (meth)acrylate monomer having two or more polymerizable functional groups and having a _-C2-4 alkylene-O- unit;
providing a through hole in the polishing layer; and disposing the light-transmitting resin member so that the light-transmitting resin member is present in the through hole when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad, wherein the light-transmitting resin member is disposed so that a surface of the light-transmitting resin member having a resin containing a structural unit derived from the polyfunctional (meth)acrylate monomer faces the polishing surface.
The method for producing the polishing pad according to any one of claims 1 to 11, comprising:

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