JP2024051638A - Polishing pad and method for manufacturing polished product - Google Patents

Abstract

[Problem] To provide a polishing pad or the like that can ensure a sufficiently long product life even when used in polishing with a strong oxidizing agent. [Solution] A polishing pad having a polishing layer with a resin sheet, the resin sheet containing a polyurethane resin, a water repellent, and a hydrolysis inhibitor. [Selected Figures] None

Description

The present invention relates to a polishing pad and a method for manufacturing a polished product.

Currently, power devices using semiconductors such as SiC and GaN are known. Chemical Mechanical Polishing (CMP) technology is used to put these semiconductor substrates into practical use.

The above-mentioned semiconductors generally have high hardness and excellent corrosion resistance, so when performing CMP, a polishing pad is used in combination with a solution containing a strong oxidizing agent such as potassium permanganate as a polishing liquid (see, for example, Patent Document 1). The addition of an oxidizing agent to the polishing liquid has also been considered for the purpose of improving the polishing rate and processing accuracy in mirror finish polishing of III-V compound semiconductors (see, for example, Patent Document 2).

Patent No. 6106535 International Publication No. 2022/024726

Polishing pads containing polyurethane resin sheets are widely used as polishing pads for CMP. Such polyurethane resin sheets typically have open pores on the surface and have a structure in which air bubbles formed inside are connected in a three-dimensional mesh (hereinafter, the air bubbles connected in a three-dimensional mesh in this structure are also referred to as "connected pores"). Due to this structure, the polishing liquid that permeates through the open pores on the polishing surface can move between the air bubbles, and therefore the polishing liquid tends to be retained inside the polishing pad. However, when using a polishing liquid containing a strong oxidizing agent as described in Patent Documents 1 and 2, it has been found that if the polishing liquid remains inside the polishing pad, the polyurethane resin sheet is hydrolyzed to a low molecular weight, causing a significant decrease in physical properties and a decrease in product life. This tendency is particularly noticeable in suede pads (polishing pads with a soft polishing layer manufactured by a wet film formation method) that are often used in the finishing process of polishing. The reasons for this are not entirely clear, but some of the reasons include that the wet film-forming method is a manufacturing process in which an organic solvent is replaced with water in an aqueous coagulation liquid, which makes it easy for interconnected pores to form, and that polyester polyols tend to be used as the polyol component of polyurethane resins, as they tend to produce teardrop-shaped bubbles.

The present invention was made in consideration of the above circumstances, and aims to provide a polishing pad etc. that can ensure a sufficiently long product life even when used for polishing with a strong oxidizing agent.

As a result of intensive research into solving the above problems, the inventors discovered that the above problems could be solved by using a polishing pad containing specific components, which led to the completion of the present invention.

That is, the present invention includes the following aspects.
[1]
A polishing pad having a polishing layer having a resin sheet,
The resin sheet comprises a polyurethane resin, a water repellent, and a hydrolysis inhibitor.
[2]
The polishing pad according to [1], wherein the water repellent agent comprises at least one selected from the group consisting of a fluorine-based water repellent agent, a silicone-based water repellent agent, and a hydrocarbon-based water repellent agent.
[3]
The polishing pad according to [1] or [2], wherein the water repellent agent contains a polyurethane resin having a perfluoroalkyl group.
[4]
The polishing pad according to any one of [1] to [3], wherein the hydrolysis inhibitor comprises at least one selected from the group consisting of carbodiimide compounds, oxazoline compounds, and epoxy compounds.
[5]
The polishing pad according to any one of [1] to [4], wherein the hydrolysis inhibitor contains a carbodiimide compound having a carbodiimide equivalent of 50 or more and 1000 or less.
[6]
The polishing pad according to any one of [1] to [5], wherein the resin sheet has air bubbles inside that are interconnected in a three-dimensional network pattern.
[7]
The density of the resin sheet is 0.15 g/ ^cm3 or more and 0.35 g/ ^cm3 or less,
The polishing pad according to any one of [1] to [6], wherein the Shore A hardness of the resin sheet is 15 degrees or more and 50 degrees or less.
[8]
preparing a resin solution containing a polyurethane resin, a solvent, a water repellent, and a hydrolysis inhibitor;
applying the resin solution to a surface of a film-forming substrate;
A step of coagulating and regenerating the resin in the resin solution to form a precursor sheet;
The method for producing a polishing pad according to any one of [1] to [7],
[9]
A method for producing a polished product, comprising a polishing step of polishing a workpiece using the polishing pad according to any one of [1] to [7] in the presence of a polishing liquid containing a strong oxidizing agent.

The present invention provides polishing pads and the like that can ensure a sufficiently long product life even when used for polishing with a strong oxidizing agent.

1 is a cross-sectional view showing a schematic diagram of an example of a polishing pad according to the present invention.

The following describes in detail an embodiment of the present invention (hereinafter referred to as the "present embodiment"); however, the present invention is not limited to this embodiment, and various modifications are possible without departing from the gist of the present invention.

[Polishing pad]
The polishing pad of this embodiment is a polishing pad having a polishing layer with a resin sheet, the resin sheet containing a polyurethane resin, a water repellent, and a hydrolysis inhibitor. Since the polishing pad of this embodiment is configured in this way, it can ensure a sufficiently long product life even when used for polishing using a strong oxidizing agent.

FIG. 1 is a schematic cross-sectional view showing an example of a polishing pad of this embodiment. The polishing pad 110 includes a resin sheet (hereinafter simply referred to as "resin sheet") 112 containing a polyurethane resin, a water repellent, and a hydrolysis inhibitor, and a substrate 114, laminated in this order. The resin sheet 112 and the substrate 114 are directly or indirectly bonded to each other, and in this example, the resin sheet 112 and the substrate 114 are bonded via an adhesive layer 116. Note that the substrate 114 and the adhesive layer 116 are optional components in the polishing pad of this embodiment, and the polishing pad of this embodiment is not limited to an embodiment having the substrate 114 and the adhesive layer 116.

The resin sheet functions as an abrasive layer. In the example of FIG. 1, the resin sheet 112 has an abrasive surface P. That is, at least one surface of the abrasive pad of this embodiment corresponds to the surface of the resin sheet of this embodiment, and the surface of the resin sheet becomes the abrasive surface that is pressed against the workpiece during abrasion in this embodiment.

The density (bulk density) of the resin sheet is not particularly limited, but is preferably 0.15 g/cm ³ or more and 0.35 g/cm ³ or less at 25° C. When the density is 0.15 g/cm ³ or more, permanent deformation of the resin sheet is unlikely to occur, and when the density is 0.35 g/cm ³ or less, the object to be polished can be polished more uniformly over the entire resin sheet.
The density can be measured based on the method described in the Examples below.
The density can be adjusted to the above range, for example, by adopting the manufacturing method of the polishing pad of this embodiment described later. For example, in the manufacturing process of the resin sheet of this embodiment, the density of the resin sheet tends to be increased by reducing the amount of foaming agent such as water, inert gas, hollow fine particles, etc. in the case of the dry molding method, and the amount of hydrophilic activator that promotes foaming in the case of the wet film forming method.

The Shore A hardness of the resin sheet is not particularly limited, but is preferably 15 degrees or more and 50 degrees or less, and more preferably 20 degrees or more and 40 degrees or less. By having a Shore A hardness of 15 degrees or more, the polishing rate can be increased and the flatness of the polished surface of the polished object after polishing tends to be improved. In addition, by having a Shore A hardness of 50 degrees or less, the micro-defects of the polished object tend to be reduced. Furthermore, by having a Shore A hardness within the above range, the polishing pad of this embodiment tends to be applicable to a wide range of polished objects, from InP substrates, which are considered to be brittle substrates among compound semiconductors, to SiC and GaN, which are so-called difficult-to-cut materials.
The Shore A hardness is measured at 25° C. in accordance with JIS K 7311. More specifically, a plurality of samples are stacked to a total thickness of 4.5 mm or more, and the Shore A durometer is used to measure the hardness.
The Shore A hardness can be controlled, for example, by adjusting the type and composition of the resin used in the resin sheet, and the amount of additives (for example, carbon black) that can be used when producing the resin sheet.

In this embodiment, from the viewpoint of achieving both uniformity of polishing, polishing rate, and flatness after polishing, and reducing microdefects in the workpiece, it is particularly preferable that the density of the resin sheet is 0.15 g/ ^cm3 or more and 0.35 g/ ^cm3 or less, and that the Shore A hardness of the resin sheet is 15 degrees or more and 50 degrees or less.
The density and Shore A hardness can be controlled within the above-mentioned ranges, for example, by the above-mentioned methods.

The thickness of the resin sheet is not particularly limited, but is preferably 0.2 mm or more and 5.0 mm or less, and more preferably 0.3 mm or more and 2.0 mm or less. The thickness of the resin sheet is measured in accordance with the measurement method described in JIS K 6505. That is, it is the thickness when a load of 100 g per ^cm2 is applied (loaded) as an initial load in the thickness direction of the resin sheet.

The compression ratio of the resin sheet is not particularly limited, but is preferably 1% to 30%, and more preferably 3% to 20%. When the compression ratio is within the above range, the polishing pad tends to be able to adequately wipe off and remove polishing debris and the like present on the workpiece during polishing. Therefore, there is a tendency to be able to suppress micro-defects caused by agglomerates of polishing debris and the like. The compression ratio can be controlled, for example, by adjusting the size, number, shape, etc. of the air bubbles in the resin sheet. The compression ratio is measured according to the following method.

The compressive modulus of the resin sheet is not particularly limited, but is preferably 50% or more and 100% or less, and more preferably 80% or more and 100% or less. By having the compressive modulus within the above range, it tends to be possible to further reduce microdefects in the polished object. The compressive modulus can be controlled, for example, by adjusting the type and composition of the resin used in the resin sheet. The compressive modulus is measured according to the following method.

The compressibility and compressive modulus of the resin sheet are determined using a Shopper-type thickness gauge (pressure surface: circular with a diameter of 1 cm) in accordance with JIS L 1021. Specifically, at room temperature, the thickness _t0 is measured after applying an initial load for 30 seconds from an unloaded state, and then the final load is applied from the thickness _t0 state and the thickness _t1 is measured after leaving it as it is for 1 minute. Furthermore, all loads are removed from the thickness _t1 state, and after leaving it for 1 minute, the thickness _t0 ' is measured after applying the initial load again for 30 seconds. From these, the compressibility and compressive modulus are calculated according to the following formula:
Compression ratio (%)=(t ₀ −t ₁ )/t ₀ ×100
Compressive elastic modulus (%)=(t ₀ '−t ₁ )/(t ₀ −t ₁ )×100
In this case, the initial load is 100 g/cm ² and the final load is 1120 g/cm ² .

The 100% modulus of the polyurethane resin constituting the polishing layer of the resin sheet is preferably 1 MPa or more and 30 MPa or less, and more preferably 5 MPa or more and 20 MPa or less. By using a polyurethane resin with a 100% modulus of 30 MPa or less, the occurrence of scratches on the polished object tends to be suppressed, and high-precision polishing tends to be achieved. In addition, by using a polyurethane resin with a 100% modulus of 1 MPa or more, defects present on the polished object tend to be easily removed. The 100% modulus is an index of the hardness of the resin, and is the value obtained by dividing the load applied when an unfoamed resin sheet is stretched 100% (to twice the original length) by the unit area. The larger this value, the harder the resin is.

The resin sheet preferably has a plurality of bubbles (not shown) therein. Such a plurality of bubbles may be formed by a wet film-forming method or a dry molding method. An example of the wet film-forming method is, but is not limited to, a method in which a resin solution in which a resin such as a polyurethane resin is dissolved in a water-miscible organic solvent is applied to a sheet-shaped film-forming substrate, and then the organic solvent is replaced with water in a water-based coagulation liquid to obtain a resin sheet. An example of the dry molding method is, but is not limited to, a method in which a resin sheet is obtained by reacting various known polyisocyanate compounds, polyol compounds, and polyamine compounds.
Generally, resin sheets formed by wet film-forming method tend to be more susceptible to hydrolysis in terms of resin composition and specific surface area than those formed by dry molding method. Therefore, resin sheets formed by wet film-forming method tend to be more susceptible to the strong oxidizing agent used in polishing, and therefore the effect of long-term use in this embodiment tends to be more prominent.
When the resin sheet is formed by a wet film forming method, the polishing surface P side may have a skin layer with dense micropores (not shown), or the polishing surface may have holes (described later) formed by grinding (buffing). The surface of the skin layer has fine flatness. It is preferable that the inner side of the skin layer (inside the resin sheet) has rounded triangular cross-sectional holes (teardrop-shaped bubbles; not shown) with a pore diameter larger than the micropores of the skin layer along the thickness direction of the resin sheet. It is preferable that the size of the holes on the polishing surface P side is smaller than the surface side opposite to the polishing surface P. The resin sheet may have holes (fine bubbles; not shown) larger than the micropores of the skin layer and smaller than the holes on the surface of the skin layer or on the inner side of the skin layer.
When the resin sheet is formed by a dry molding method, pores having a circular or elliptical (approximately spherical) cross section may be formed and approximately uniformly distributed inside the resin sheet.
In this embodiment, the resin sheet may have bubbles (communicating holes) that are connected in a three-dimensional mesh-like manner inside. For example, the micropores, pores, and microbubbles in the skin layer may be connected to each other in a mesh-like manner through communicating holes, and the approximately spherical pores may be connected to each other in a mesh-like manner through communicating holes. In this embodiment, although not limited to the following, such a structure tends to be easily obtained when the resin sheet is formed by a wet film-forming method.

The resin sheet is not particularly limited as long as it has a composition that includes polyurethane resin. For example, the resin sheet may contain 80% by mass or more and 100% by mass or less of polyurethane resin relative to its total amount (100% by mass). The resin sheet preferably contains 85% by mass or more and 100% by mass or less of polyurethane resin relative to its total amount (100% by mass), more preferably 90% by mass or more and 100% by mass or less, and even more preferably 90% by mass or more and 95% by mass or less.

Examples of polyurethane resins include polyester-based polyurethane resins, polyether-based polyurethane resins, and polycarbonate-based polyurethane resins, depending on the type of polyol component contained, and these are used alone or in combination of two or more. Among these, polyester-based polyurethane resins are preferred because they are prone to forming teardrop-shaped bubbles that promote circulation of the polishing liquid by storing and discharging the polishing liquid during polishing. In general, resin sheets formed from polyester-based polyurethane resins are easily affected by strong oxidizing agents used in polishing, and therefore, when polyester-based polyurethane resins are used, the effects of long-term use in this embodiment tend to be more pronounced.

The polyurethane resin may be synthesized by a conventional method, or may be a commercially available product. Examples of commercially available products include CRISBON (trade name, manufactured by DIC Corporation), SANPREN (trade name, manufactured by Sanyo Chemical Industries, Ltd.), and REZAMIN (trade name, manufactured by Dai-Nippon Seika Kogyo Co., Ltd.). The polyurethane resin may be used alone or in combination of two or more kinds.

The resin sheet may contain other resins such as polysulfone resin and/or polyimide resin in addition to polyurethane resin. The polysulfone resin may be synthesized by a conventional method or may be commercially available. An example of a commercially available product is Udel (manufactured by Solvay Advanced Polymers, trade name). The polyimide resin may be synthesized by a conventional method or may be commercially available. An example of a commercially available product is Auram (manufactured by Mitsui Chemicals, trade name).

The resin sheet contains a water repellent in addition to the polyurethane resin. The water repellent is an agent that, when contained in the resin sheet, has the effect of improving the water repellency of the surface of the resin sheet. Here, the water repellency can be, for example, an index of the contact angle between the polishing surface and water. By containing the water repellent, the resin sheet can suppress the penetration of the polishing liquid containing a strong oxidizing agent into the inside of the pad. In particular, when the resin sheet is manufactured by a wet film forming method and has bubbles connected in a three-dimensional network shape inside, the resin sheet can suppress the penetration of the strong oxidizing agent into the fine bubbles present in the walls of the teardrop-shaped bubbles while allowing the polishing liquid to be held inside the teardrop-shaped bubbles.
Whether the resin sheet contains a water repellent agent can be confirmed by using a known analysis method such as elemental analysis.

Examples of water repellents include fluorine-based water repellents, silicone-based water repellents, and hydrocarbon-based water repellents. Among these, fluorine-based water repellents (water repellents containing fluorine atoms) are preferred from the standpoint of chemical resistance, uniformity of mixing with polyurethane resin, etc. Water repellents may be used alone or in combination of two or more types.

Examples of fluorine-based water repellents include compounds having a perfluoroalkyl group, preferably containing a polyurethane resin having a perfluoroalkyl group, and more preferably having a structure derived from a fluorotelomer represented by the following formula (1). This is presumably because the bond energy between the C-F bond is 116 kcal/mol, giving the compound particularly high stability, which prevents the compound from bonding (adhesion) with other molecules (although the cause is not limited to this).
Rf-R-X (1)
In formula (1), Rf represents a perfluoroalkyl group having 3 to 8 carbon atoms, preferably 4 to 8, more preferably 6 to 8, and even more preferably 6. R represents an alkylene group having 1 to 6 carbon atoms, preferably 2 to 4, and more preferably 2. X represents a functional group, and examples of the functional group include a hydroxy group, CH ₂ ═CHC(═O)CO—, H(OCH ₂ CH ₂ ) _x O—, and YSO ₃ —[Y represents a hydrogen atom or NH ₄ ], and is preferably a hydroxy group.

Furthermore, examples of fluorine-based water repellents having a perfluoroalkyl group include fluorine-based water repellents in which a resin is modified with a perfluoroalkyl group. From the viewpoint of improving dispersibility in the resin sheet and stability over time, the resin may be the same type of resin as that which can constitute the resin sheet of the polishing pad, such as a polyurethane resin. Modification methods include, for example, a method of introducing a perfluoroalkyl group into the end and/or side chain of the resin, and the perfluoroalkyl group can be introduced into the resin by using the fluorine telomer listed in the above formula (1). Fluorine-based water repellents having a perfluoroalkyl group may be used alone or in combination of two or more.

In this embodiment, from the viewpoint of long-term use when subjected to polishing using a strong oxidizing agent, among the above fluorotelomers, those having 6 carbon atoms in Rf are preferred, and those having 1 or 2 carbon atoms in R, that is, those having a perfluorohexylmethyl group (C ₆ F ₁₃ CH ₂ -) or a perfluorohexylethyl group (C ₆ F ₁₃ C ₂ H ₄ -) are more preferred. In addition, in consideration of dispersibility in a resin sheet and stability over time, a fluoro-based water repellent in which a fluorotelomer is introduced into the resin is preferred as a fluoro-based water repellent in which a resin is modified with a perfluoroalkyl group, for example, a resin having a group represented by Rf-R- in the above formula (1), and a polyurethane resin having a group represented by Rf-R- in the above formula (1) is more preferred. Examples of such resins include polyurethane resins described in International Publication No. 2012/172936.

In addition, when a fluorine-based water repellent such as fluorine telomer is used as the water repellent and the fluorine-based water repellent contains a fluorine-based water repellent having an Rf of 6 carbon atoms, it is preferable that 60 mol % or more and 100 mol % or less of the fluorine-based water repellent contained in the resin sheet is a fluorine-based water repellent having an Rf of 6 carbon atoms. This limits compounds containing many fluorine atoms such as fluorine telomers having an Rf of more than 6 carbon atoms and compounds containing few fluorine atoms such as fluorine telomers having an Rf of less than 6 carbon atoms. This makes it possible to reduce the content of compounds containing many fluorine atoms and retain the polishing liquid while more effectively suppressing penetration into the communicating holes, and also tends to reduce the content of compounds containing few fluorine atoms and more effectively ensure the above-mentioned moderate water repellency.

The fluorine-based water repellent may be synthesized by a conventional method, or may be a commercially available product. Examples of commercially available products include CRISBON ASISTOR SD series (manufactured by DIC Corporation, product name), ASAHIGUARD E series (manufactured by AGC SEIMI CHEMICAL Co., Ltd., product name), NK GUARD S series (manufactured by NICCA CHEMICAL Co., Ltd., product name), and UNIDYNE MULTI series (manufactured by DAIKIN INDUSTRIES, LTD., product name).

The content of the water repellent in the resin sheet is not particularly limited, but is preferably 0.01% by mass or more and 5% by mass or less, more preferably 0.02% by mass or more and 1% by mass or less, and even more preferably 0.05% by mass or more and 0.5% by mass or less, relative to the resin sheet (100% by mass). When the content of the water repellent is 0.01% by mass or more relative to the resin sheet (100% by mass), the penetration of the polishing liquid into the communicating holes tends to be suppressed. In addition, when the content of the water repellent is 5% by mass or less relative to the resin sheet (100% by mass), the elution of the water repellent tends to be prevented, and the polishing liquid tends to easily penetrate into teardrop-shaped bubbles in the resin sheet, and the polishing liquid tends to be preferably retained, and the circulation of the polishing liquid by storing and discharging the polishing liquid becomes better, and the polishing rate and polishing accuracy tend to improve.

The resin sheet contains a hydrolysis inhibitor in addition to the polyurethane resin. The hydrolysis inhibitor is a substance that, when contained in the resin sheet, has the effect of suppressing hydrolysis of the resin sheet caused by the surrounding environment. By containing the hydrolysis inhibitor, the resin sheet can suppress hydrolysis caused by a strong oxidizing agent.
Whether the resin sheet contains the hydrolysis inhibitor can be confirmed by using a known analysis method such as elemental analysis.

In this embodiment, from the viewpoint of long-term use when subjected to polishing using a strong oxidizing agent, it is preferable that the hydrolysis inhibitor contains at least one selected from the group consisting of carbodiimide compounds, oxazoline compounds, and epoxy compounds, and it is more preferable that the hydrolysis inhibitor contains a carbodiimide compound because of its high effect of eliminating the catalytic activity of protons derived from the carboxyl group terminals generated by hydrolysis of ester bonds and urethane bonds.

The carbodiimide compound is not particularly limited as long as it contains a carbodiimide group in the molecule. A polycarbodiimide compound containing two or more carbodiimide groups in the molecule is preferred, and a carbodiimide compound represented by the following formula (2) is more preferred.
(-N=C=N-R-) _n (2)
In formula (2), n is an integer of 1 or more and 50 or less, preferably an integer of 5 or more and 40 or less, and more preferably an integer of 10 or more and 30 or less. R is a structure derived from any one of an aliphatic polyisocyanate, an alicyclic polyisocyanate, and an aromatic polyisocyanate, and these may be used alone or in combination of two or more.
Specifically, R is 1,5-naphthalene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, hexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone. Examples of the polycarbodiimide compounds include polycarbodiimide compounds which are structures derived from diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, methylcyclohexane diisocyanate, tetramethylxylylene diisocyanate, 2,6-diisopropylphenyl isocyanate, 1,3,5-triisopropylbenzene-2,4-diisocyanate, or the like, and are produced by subjecting these polyisocyanate compounds to a decarboxylation condensation reaction in the presence of a carbodiimide catalyst, and these may be used alone or in combination of two or more.

In this embodiment, in order to prevent foaming due to a side reaction (decarboxylation reaction) with the water of the coagulation bath that may be used when preparing the resin sheet and to achieve a more uniform film formation, it is preferable that the carbodiimide compound is a compound that does not contain an isocyanate group at the end, and examples of such compounds include polycarbodiimides in which both ends of a polyisocyanate polycarbodiimide compound are blocked with a monoisocyanate, a monoalcohol, a monoamine, or the like.

In the present embodiment, from the viewpoint of preventing elution of the polycarbodiimide compound, the hydrolysis inhibitor preferably contains a carbodiimide compound having a carbodiimide equivalent of 50 or more and 1000 or less, more preferably contains a carbodiimide compound having a carbodiimide equivalent of 100 or more and 800 or less, and further preferably contains a carbodiimide compound having a carbodiimide equivalent of 150 or more and 500 or less. The carbodiimide equivalent can be determined by dividing the "molecular weight of the carbodiimide compound" by the "number of carbodiimide groups in one molecule of the carbodiimide compound".
The polycarbodiimide compound may be synthesized by a conventional method, or may be commercially available, such as Carbodilite series (manufactured by Nisshinbo Chemical Co., Ltd., product name), Carbodista series (manufactured by Teijin Ltd., product name), and Stavaxol series (manufactured by Rhein Chemie AG, product name).

The oxazoline compound is not particularly limited as long as it contains an oxazoline group in the molecule. A bisoxazoline compound is preferred, and specific examples thereof include, but are not limited to, 2,2'-bis(2-oxazoline), 2,2'-bis(4-methyl-2-oxazoline), 2,2'-bis(4,4-dimethyl-2-oxazoline), 2,2'-bis(4-ethyl-2-oxazoline), 2,2'-bis(4,4'-diethyl-2-oxazoline), 2,2'-bis(4-propyl-2-oxazoline), 2,2'-bis(4-butyl-2-oxazoline), and 2,2'-bis(4-butyl-2-oxazoline). 2,2'-bis(4-hexyl-2-oxazoline), 2,2'-bis(4-phenyl-2-oxazoline), 2,2'-bis(4-cyclohexyl-2-oxazoline), 2,2'-bis(4-benzyl-2-oxazoline), 2,2'-p-phenylenebis(2-oxazoline), 2,2'-m-phenylenebis(2-oxazoline), 2,2'-o-phenylenebis(2-oxazoline), 2,2'-p-phenylenebis(4-methyl-2-oxazoline), -oxazoline), 2,2'-p-phenylenebis(4,4-dimethyl-2-oxazoline), 2,2'-m-phenylenebis(4-methyl-2-oxazoline), 2,2'-m-phenylenebis(4,4-dimethyl-2-oxazoline), 2,2'-ethylenebis(2-oxazoline), 2,2'-tetramethylenebis(2-oxazoline), 2,2'-hexamethylenebis(2-oxazoline), 2,2'-octamethylenebis(2-oxazoline), Examples include 2,2'-decamethylenebis(2-oxazoline), 2,2'-ethylenebis(4-methyl-2-oxazoline), 2,2'-tetramethylenebis(4,4-dimethyl-2-oxazoline), 2,2'-9,9'-diphenoxyethanebis(2-oxazoline), 2,2'-cyclohexylenebis(2-oxazoline) and 2,2'-diphenylenebis(2-oxazoline), which may be used alone or in combination of two or more.

The epoxy compound is not particularly limited as long as it contains an epoxy group in the molecule. Preferred examples of the epoxy compound include glycidyl ester compounds and glycidyl ether compounds.

Specific examples of glycidyl ester compounds include, but are not limited to, benzoic acid glycidyl ester, t-Bu-benzoic acid glycidyl ester, p-toluic acid glycidyl ester, cyclohexane carboxylic acid glycidyl ester, pelargonic acid glycidyl ester, stearic acid glycidyl ester, lauric acid glycidyl ester, palmitic acid glycidyl ester, behenic acid glycidyl ester, versatic acid glycidyl ester, oleic acid glycidyl ester, linoleic acid glycidyl ester, linoleic acid glycidyl ester, behenolic acid glycidyl ester, stearolic acid glycidyl ester, terephthalic acid diglycidyl ester, isophthalic acid Examples of such glycidyl esters include diglycidyl esters of phthalic acid, diglycidyl esters of naphthalenedicarboxylic acid, diglycidyl esters of methyl terephthalic acid, diglycidyl esters of hexahydrophthalic acid, diglycidyl esters of tetrahydrophthalic acid, diglycidyl esters of cyclohexanedicarboxylic acid, diglycidyl esters of adipic acid, diglycidyl esters of succinic acid, diglycidyl esters of sebacic acid, diglycidyl esters of dodecanedioic acid, diglycidyl esters of octadecanedicarboxylic acid, triglycidyl esters of trimellitic acid, and tetraglycidyl esters of pyromellitic acid. These may be used alone or in combination of two or more.

Specific examples of glycidyl ether compounds include, but are not limited to, phenyl glycidyl ether, o-phenyl glycidyl ether, 1,4-bis(β,γ-epoxypropoxy)butane, 1,6-bis(β,γ-epoxypropoxy)hexane, 1,4-bis(β,γ-epoxypropoxy)benzene, 1-(β,γ-epoxypropoxy)-2-ethoxyethane, 1-(β,γ-epoxypropoxy)-2-benzyloxyethane, 2,2-bis-[р-(β,γ-epoxypropoxy)phenyl]propane, and bisglycidyl polyethers obtained by reacting bisphenols such as 2,2-bis-(4-hydroxyphenyl)propane and 2,2-bis-(4-hydroxyphenyl)methane with epichlorohydrin, and these may be used alone or in combination of two or more.

In this embodiment, the content of the hydrolysis inhibitor in the resin sheet is not particularly limited, but is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.05% by mass or more and 7% by mass or less, and even more preferably 0.1% by mass or more and 5% by mass or less, relative to the resin sheet (100% by mass). When the content of the hydrolysis inhibitor is 0.01% by mass or more relative to the resin sheet (100% by mass), hydrolysis of the polishing layer tends to be sufficiently suppressed. In addition, when the content of the hydrolysis inhibitor is 10% by mass or less relative to the resin sheet (100% by mass), elution of the hydrolysis inhibitor tends to be prevented, and the hydrolysis inhibitor tends to be uniformly dispersed in the resin sheet, and changes in the physical properties of the polishing layer itself tend to be prevented.

The reason why the polishing pad of this embodiment can ensure a sufficiently long product life even when subjected to polishing using a strong oxidizing agent is presumed to be as follows, although this is not intended to be limiting.
In this embodiment, the resin sheet may typically have a structure in which air bubbles formed in the resin sheet are interconnected in a three-dimensional network. In this case, the polishing liquid can move between the air bubbles through the openings on the polishing surface, and the polishing liquid has the property of being held throughout the inside of the polishing pad. Here, if the polishing liquid containing a strong oxidizing agent remains inside the polishing pad, the polyurethane resin sheet will be hydrolyzed to a low molecular weight, causing a significant decrease in physical properties and shortening the product life. As a result of intensive research, the present inventors have found that the combined use of a water repellent and a hydrolysis inhibitor contributes to the extension of the product life. For example, when a carbodiimide compound is used as the hydrolysis inhibitor, when a strong oxidizing agent penetrates, the carboxyl group generated by hydrolysis reacts with the carbodiimide compound, causing the carboxyl group to disappear, and the further hydrolysis of the polyurethane resin constituting the polishing layer to a low molecular weight can be suppressed. When only the hydrolysis inhibitor is added, the penetration of the polishing liquid containing a strong oxidizing agent into the interconnecting holes cannot be suppressed, and the contact area between the polyurethane resin sheet and the polishing liquid does not change, so the hydrolysis of the polyurethane resin sheet cannot be sufficiently suppressed. Therefore, in this embodiment, by using the water repellent together with the hydrolysis inhibitor, the degree of penetration of the polishing liquid containing a strong oxidizing agent can be controlled while suppressing the low molecular weight of the polyurethane resin that constitutes the polishing layer, and therefore, it is presumed that even when polishing with a strong oxidizing agent is performed, a sufficiently long product life can be ensured.In addition, when only the water repellent is added, the penetration of the polishing liquid containing a strong oxidizing agent into the communicating hole can be suppressed, but since the polishing liquid is always present on the polishing surface, hydrolysis of the polishing surface surface cannot be avoided.When the polishing load is applied to the polishing surface, the polyurethane resin sheet may tear, which may cause polishing defects.

In this embodiment, from the viewpoint of further improving the polishing rate and polishing accuracy, it is preferable that the resin sheet further contains carbon black. The reason why the polishing rate is improved by including carbon black is that when the resin sheet is manufactured by a wet film-forming method, the resin sheet can form a uniform foam shape by including carbon black, which improves the retention ability of the polishing liquid (however, the cause is not limited to this). In addition, since carbon black has an effect of stabilizing foam formation in polyurethane resin, it is presumed that the flatness of the polished object is further improved. Furthermore, since carbon black imparts brittleness to the resin sheet, it tends to suppress the clogging of pores due to fuzzing (resin elongation) of the polyurethane resin, and it is presumed that the polishing accuracy is further improved. When carbon black is included, it is preferable that the resin sheet (100 mass%) contains 1 mass% to 35 mass%, more preferably 3 mass% to 30 mass%, and even more preferably 5 mass% to 25 mass%.

In addition to the above-mentioned components, the resin sheet may contain materials that are typically used in resin sheets for polishing pads. Furthermore, the resin sheet may contain some residual materials, such as solvents, that were used in the manufacturing process of the resin sheet.

Microbubbles may be present on the polished surface P of the resin sheet. The microbubbles can be formed, for example, by adding a pore-forming agent to form microbubbles on the surface of the skin layer or further inside the skin layer when the resin sheet is formed.

The substrate 114 provided in the polishing pad 110 is a member that can be used to support a resin sheet, and is not particularly limited, and may be a material that is included as a substrate in conventional polishing pads. Specific examples of substrates include resin films such as polyethylene terephthalate (hereinafter referred to as "PET") film, nonwoven fabrics bonded with polyurethane resin, and foam sheets such as foamed polyurethane resin and polyethylene foam.

The adhesive layer 116 may also contain an adhesive or pressure sensitive adhesive that is used in conventional polishing pads. Examples of materials for the adhesive layer 116 include various thermoplastic adhesives such as acrylic, nitrile, nitrile rubber, polyamide, polyurethane, and polyester.

The substrate 114 and adhesive layer 116 in the polishing pad 110 may be derived from a double-sided tape that includes them. The double-sided tape has adhesive layers containing an adhesive or pressure-sensitive adhesive on both sides of the substrate 114, one of the adhesive layers corresponding to the adhesive layer 116. The other adhesive layer is for attaching the polishing pad 110 to the holding platen of the polishing machine. The double-sided tape may be one included in conventional polishing pads, and may have a release paper (not shown) on the side opposite the substrate 114.

[Method of manufacturing polishing pad]
Next, an example of a method for manufacturing the polishing pad of this embodiment will be described. Here, a case where the resin sheet 112 is manufactured by a wet film forming method will be described, but the manufacturing method of the resin sheet 112 is not limited to this. For example, the polishing pad of this embodiment may be formed by a known dry molding method. The dry molding method is not limited to the following, but may be, for example, a method of obtaining a resin sheet by reacting a polyisocyanate compound, a polyol compound, and a polyamine compound.

An example of a wet film formation method that can be used in this embodiment is a manufacturing method that includes a step of preparing a resin sheet 112 and a step of bonding a substrate 114 to the resin sheet 112 to obtain a polishing pad 110.

The process of preparing the resin sheet 112 further includes a process of preparing a resin solution containing a resin, a solvent, a water repellent, and a hydrolysis inhibitor (resin solution preparation process), a process of applying the resin solution to the surface of the film-forming substrate (application process), a process of solidifying and regenerating the resin in the resin solution to form a precursor sheet (solidification and regeneration process), a process of removing the solvent from the precursor sheet to obtain the resin sheet 112 (solvent removal process), and a process of grinding and/or partially removing the resin sheet 112 by buffing or slicing (grinding and removal process). Each process will be described below.

First, in the resin solution preparation process, a resin such as the polyurethane resin described above, a solvent capable of dissolving the resin and which is miscible with the coagulation liquid described below, and a water repellent, a hydrolysis inhibitor, and other materials (e.g., additives such as carbon black, other pigments, hydrophilic activators, and hydrophobic activators) to be contained in the resin sheet 112 are mixed together, and the mixture is degassed under reduced pressure as necessary to prepare a resin solution.
The solvent is not particularly limited, but examples thereof include N,N-dimethylformamide (hereinafter referred to as "DMF") and N,N-dimethylacetamide. The content of the resin relative to the total amount of the resin solution is not particularly limited, but may be, for example, in the range of 10% by mass to 50% by mass, or in the range of 15% by mass to 35% by mass.
As the water repellent, the water repellent listed in the section on [Polishing pad] can be used. The amount of the water repellent is preferably 0.01 parts by mass or more and 5 parts by mass or less, more preferably 0.02 parts by mass or more and 1 part by mass or less, and even more preferably 0.05 parts by mass or more and 0.5 parts by mass or less, relative to the polyurethane resin (100 parts by mass) in the resin solution.
As the hydrolysis inhibitor, the hydrolysis inhibitors listed in the section on [Polishing Pad] can be used. The amount of the hydrolysis inhibitor is preferably 0.01 parts by mass or more and 15 parts by mass or less, more preferably 0.1 parts by mass or more and 10 parts by mass or less, and even more preferably 1 part by mass or more and 5 parts by mass or less, relative to the polyurethane resin (100 parts by mass) in the resin solution.
As another material, carbon black as mentioned in the section on [Polishing Pad] can be used. The amount of carbon black is preferably 1 part by mass or more and 35 parts by mass or less, more preferably 3 parts by mass or more and 30 parts by mass or less, and even more preferably 5 parts by mass or more and 25 parts by mass or less, relative to the polyurethane resin (100 parts by mass) in the resin solution.
From the viewpoint of adjusting the density, Shore A hardness, etc. of the resulting resin sheet, water and a film-forming assistant such as a pore-forming agent represented by a cellulose derivative may be added to the resin solution.

Next, in the coating process, the resin solution is applied to the surface of the strip-shaped film-forming substrate using a coating device such as a knife coater, preferably at room temperature, to form a coating film. The thickness of the resin solution applied at this time may be appropriately adjusted so that the final resin sheet 112 has the desired thickness. Examples of materials for the film-forming substrate include resin films such as PET films, fabrics, and nonwoven fabrics. Among these, resin films such as PET films, which are difficult for liquid to penetrate, are preferred.

Next, in the solidification and regeneration process, the coating of the resin solution applied to the film-forming substrate is continuously guided into a solidification liquid mainly composed of a poor solvent for the resin (for example, water in the case of polyurethane resin). In order to adjust the regeneration speed of the resin, an organic solvent such as a polar solvent other than the solvent in the resin solution may be added to the solidification liquid. The temperature of the solidification liquid is not particularly limited as long as it is a temperature at which the resin can be solidified, and may be, for example, 15°C or higher and 65°C or lower. In the solidification liquid, a film (skin layer) is first formed at the interface between the coating of the resin solution and the solidification liquid, and countless dense micropores are formed in the resin immediately adjacent to the film. After that, the regeneration of the resin having a three-dimensional network structure proceeds due to the cooperative phenomenon of the diffusion of the solvent contained in the resin solution into the solidification liquid and the infiltration of the poor solvent into the resin. At this time, if the substrate for film formation is one that is difficult for liquid to penetrate (for example, a PET film), the solidification liquid will not penetrate the substrate for film formation, and the solvent in the resin solution will be replaced by the poor solvent preferentially near the skin layer, and larger voids (teardrop-shaped bubbles) tend to form in the region inside the skin layer rather than near it. In this way, a precursor sheet is formed on the substrate for film formation.

Next, in the solvent removal process, the formed precursor sheet is peeled off from the film-forming substrate, and the solvent remaining in the precursor sheet is removed to obtain a resin sheet 112. A conventionally known cleaning solution can be used to remove the solvent. Furthermore, the resin sheet 112 after the solvent has been removed may be dried as necessary. For example, a cylinder dryer equipped with a cylinder having a heat source inside may be used to dry the resin sheet 112, but the drying method is not limited to this. When a cylinder dryer is used, the precursor sheet is dried by passing it along the circumferential surface of the cylinder. Furthermore, the obtained resin sheet 112 may be wound into a roll.

Next, in the grinding and removal process, at least one of the main surface of the resin sheet 112, preferably the skin layer side, and the back surface, which is the opposite side, is ground and/or partially removed by buffing or slicing. The thickness of the resin sheet 112 can be made uniform by buffing or slicing, so the pressing force against the object to be polished can be made more uniform, further suppressing damage to the object to be polished and improving the flatness of the object to be polished.

Next, the base material 114 is bonded to the resin sheet 112 to obtain the polishing pad 110. In this process, for example, a double-sided tape having the base material 114 and an adhesive layer 116 is used to bond the base material 114 to the surface of the resin sheet 112 opposite the polishing surface P via the adhesive layer 116. Furthermore, the other adhesive layer of the double-sided tape and release paper may be provided on the side of the base material 114 opposite the adhesive layer 116. In this way, the polishing pad 110 is obtained.

[Method for manufacturing polished product]
Next, a method of polishing using the polishing pad 110 of this embodiment will be described.
The method for producing a polished product of this embodiment includes a polishing step of polishing a workpiece with the polishing pad of this embodiment in the presence of a polishing liquid.
The object to be polished in the polishing process is not particularly limited, but may be, for example, a semiconductor wafer, a semiconductor device, a glass substrate, a substrate for various recording disks, or a glass substrate for liquid crystal display.Among these, the object to be polished is preferably a semiconductor wafer, and the material of the semiconductor wafer is preferably a compound semiconductor made of two or more elements.In addition, the polishing pad of this embodiment can be suitably used as a polishing pad for polishing a compound semiconductor wafer using a polishing solution containing a strong oxidizing agent.

An example of polishing is described below. First, a holding pad is attached to the workpiece holder of the polishing machine, and the workpiece is held by the holding pad. To attach the holding pad to the workpiece holder, remove the release paper of the double-sided tape as necessary, and use the exposed adhesive layer to adhere and fix the holding pad to the workpiece holder so that the holding surface faces downward (or upward). Alternatively, if the holding pad does not have double-sided tape, the holding pad is adhered and fixed to the workpiece holder with a separately prepared adhesive or pressure sensitive adhesive. Next, an appropriate amount of water is applied to the holding surface, and the workpiece is pressed against it, so that the workpiece is held by the workpiece holder via the holding pad due to the surface tension of the water. At this time, the polished surface (processed surface) of the workpiece faces downward (or upward). On the other hand, a polishing pad 110 is attached to the surface of a polishing platen arranged below (or above) the workpiece holder so as to face the workpiece holder, with the polishing surface P facing upward (or downward).

Next, the workpiece holder is moved toward the polishing platen to transport the workpiece so that the surface of the workpiece contacts the polishing surface P of the polishing pad 110. Then, a polishing liquid containing chemical components such as abrasive grains (polishing particles; for example, SiO ₂ , CeO ₂ , Al ₂ O ₃ ) and a strong oxidizing agent such as potassium permanganate is circulated between the workpiece and the polishing pad. At the same time, the workpiece holder and the polishing platen are rotated while the workpiece holder presses the workpiece against the polishing pad 110, so that the processed surface of the workpiece is polished by the polishing pad by CMP.

Although the present embodiment has been described in detail above, the present invention is not limited to this embodiment. For example, in the above embodiment, the adhesive layer 116 is used to bond the resin sheet 112 and the substrate 114, but the bonding between them is not limited to using the adhesive layer 116. Furthermore, the polishing pad of this embodiment does not need to have a substrate, but it is preferable that the polishing pad has a substrate from the viewpoint of handling the polishing pad. Also, the grinding and removal process may be omitted in the manufacturing method of the polishing pad.

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

Example 1
A polyurethane resin solution of Example 1 was obtained by mixing 100 parts by mass of a polyester polyurethane resin solution having a 100% modulus of 15 MPa (30 parts by mass as polyester polyurethane resin), 50 parts by mass of DMF, 8 parts by mass of water, 0.06 parts by mass of a fluorine-modified polyurethane resin (water repellent) having perfluorohexylethyl groups at its terminals, 1 part by mass of a carbodiimide compound (carbodiimide equivalent: 200) having isocyanate groups blocked at both terminals, and 15 parts by mass of a carbon black dispersion (2.8 parts by mass as carbon black).
Next, a PET film was prepared as a film-forming substrate, and the polyurethane resin solution was applied thereto using a knife coater, immersed in a coagulation bath (coagulation liquid is water), and the polyurethane resin solution was coagulated. The film-forming substrate was then peeled off, washed and dried to obtain a polyurethane resin sheet. Then, the skin layer was buffed to open the surface, and a PET film was attached to the side opposite to the buffed side of the polyurethane resin sheet, and a double-sided tape was attached to the side opposite to the side of the PET film attached to the polyurethane resin sheet to obtain the polishing pad of Example 1. When the cross section of the resin sheet of this polishing pad was observed, it was confirmed that the resin sheet had fine bubbles present in the walls of the teardrop-shaped bubbles inside. Note that these fine bubbles were obtained by a wet film-forming method, and were bubbles that were connected in a three-dimensional network shape.

(Comparative Example 1)
A polyurethane resin solution of Comparative Example 1 was obtained by mixing 100 parts by mass of a polyester-based polyurethane resin solution having a 100% modulus of 15 MPa (30 parts by mass as polyester-based polyurethane resin), 50 parts by mass of DMF, 8 parts by mass of water, 1 part by mass of a carbodiimide compound (carbodiimide equivalent: 200) having isocyanate groups blocked at both ends, and 15 parts by mass of a carbon black dispersion (2.8 parts by mass as carbon black).
A polishing pad of Comparative Example 1 was obtained in the same manner as in Example 1, except that the polyurethane resin solution of Example 1 was changed to the polyurethane resin solution of Comparative Example 1.

(Comparative Example 2)
A polyurethane resin solution of Comparative Example 2 was obtained by mixing 100 parts by mass of a polyester-based polyurethane resin solution having a 100% modulus of 15 MPa (30 parts by mass as polyester-based polyurethane resin), 50 parts by mass of DMF, 8 parts by mass of water, 0.06 parts by mass of a fluorine-modified polyurethane resin (water repellent) having a perfluorohexylethyl group at its end, and 15 parts by mass of a carbon black dispersion (2.8 parts by mass as carbon black).
A polishing pad of Comparative Example 2 was obtained in the same manner as in Example 1, except that the polyurethane resin solution of Example 1 was changed to the polyurethane resin solution of Comparative Example 2.

(Comparative Example 3)
A polyurethane resin solution of Comparative Example 3 was obtained by mixing 100 parts by mass of a polyester-based polyurethane resin solution having a 100% modulus of 8.3 MPa (30 parts by mass as polyester-based polyurethane resin), 50 parts by mass of DMF, 3 parts by mass of water, 0.5 parts by mass of a hydrophilic additive, 0.6 parts by mass of a hydrophobic activator, and 44 parts by mass of a carbon black dispersion (8.1 parts by mass as carbon black).
A polishing pad of Comparative Example 3 was obtained in the same manner as in Example 1, except that the polyurethane resin solution of Example 1 was changed to the polyurethane resin solution of Comparative Example 3.

(Tensile strength retention rate)
Using a universal tensile tester (Tensilon RTC-1210A, manufactured by A&D Co., Ltd.), the tensile strength (a) [kg/mm ² ] of the polyurethane resin sheet before immersion in the test polishing liquid was measured in accordance with JIS K 6550. Next, the polyurethane resin sheet was immersed in a test polishing liquid prepared by adjusting the pH of the potassium permanganate-based polishing liquid (DSC-201, manufactured by Fujimi Incorporated Co., Ltd.) to 3.0 with an aqueous nitric acid solution for 24 hours at 25°C. After 24 hours from the start of immersion, the polyurethane resin sheet was taken out of the test polishing liquid, washed with running water, and dried, and then the tensile strength (b) [kg/mm ² ] of the polyurethane resin sheet was measured in the same manner as above. From the values of the tensile strength (a) and tensile strength (b) measured in this way, the tensile strength retention rate was calculated by the following formula. The results are shown in Table 1.
Tensile strength retention rate [%] = tensile strength (b) / tensile strength (a) × 100

(thickness)
The thickness of the resin sheet was measured in accordance with the measurement method described in JIS K 6505. That is, the thickness was measured when a load of 100 g per ^cm2 was applied (loaded) as an initial load in the thickness direction of the resin sheet.

(density)
The density was calculated from the volume and weight of a sample cut out from the resin sheet.

(Compressibility and Compressive Elasticity)
The compressibility and compressive modulus of the resin sheet were determined using a Shopper-type thickness gauge (pressure surface: circular with a diameter of 1 cm) in accordance with JIS L 1021. That is, at room temperature, the thickness t ₀ was measured after applying an initial load for 30 seconds from an unloaded state, and then the final load was applied from the thickness t ₀ state and the thickness t ₁ was measured after leaving it as it is for 1 minute. Furthermore, all loads were removed from the thickness t ₁ state, and after leaving it for 1 minute, the thickness t ₀ ' was measured after applying the initial load again for 30 seconds. From these, the compressibility and compressive modulus were calculated according to the following formula:
Compression ratio (%)=(t ₀ −t ₁ )/t ₀ ×100
Compressive elastic modulus (%)=(t ₀ '−t ₁ )/(t ₀ −t ₁ )×100
Here, the initial load was 100 g/cm ² , and the final load was 1120 g/cm ² .

(Shore A hardness)
The Shore A hardness was measured at 25° C. in accordance with JIS K 7311. That is, a plurality of samples cut out from a resin sheet were stacked to a total thickness of 4.5 mm or more, and the Shore A durometer was used to measure the hardness.

The addition of a water repellent and a carbodiimide compound improved the tensile strength retention rate. It was also confirmed that a sufficiently high tensile strength retention rate could not be obtained with either one alone. It is presumed that this is due to the combined use of two types of additives, which are thought to have different mechanisms of action. A high tensile strength retention rate indicates that deterioration caused by the polishing liquid is suppressed, and as a result, an improvement in the product lifespan is expected.

Claims (9)

A polishing pad having a polishing layer having a resin sheet,
The resin sheet comprises a polyurethane resin, a water repellent, and a hydrolysis inhibitor. The polishing pad according to claim 1, wherein the water repellent agent comprises at least one selected from the group consisting of fluorine-based water repellents, silicone-based water repellents, and hydrocarbon-based water repellents. The polishing pad according to claim 1, wherein the water repellent agent comprises a polyurethane resin having a perfluoroalkyl group. The polishing pad according to claim 1, wherein the hydrolysis inhibitor comprises at least one selected from the group consisting of carbodiimide compounds, oxazoline compounds, and epoxy compounds. The polishing pad according to claim 1, wherein the hydrolysis inhibitor comprises a carbodiimide compound having a carbodiimide equivalent of 50 or more and 1000 or less. The polishing pad according to claim 1, wherein the resin sheet has air bubbles inside that are interconnected in a three-dimensional network pattern. The density of the resin sheet is 0.15 g/ ^cm3 or more and 0.35 g/ ^cm3 or less,
2. The polishing pad according to claim 1, wherein the resin sheet has a Shore A hardness of 15 degrees or more and 50 degrees or less. preparing a resin solution containing a polyurethane resin, a solvent, a water repellent, and a hydrolysis inhibitor;
applying the resin solution to a surface of a film-forming substrate;
A step of coagulating and regenerating the resin in the resin solution to form a precursor sheet;
The method for producing the polishing pad according to any one of claims 1 to 7, comprising: A method for producing a polished product, comprising a polishing step of polishing a workpiece using the polishing pad according to any one of claims 1 to 7 in the presence of a polishing liquid containing a strong oxidizing agent.

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