Polishing pad

Abstract

To provide a polishing pad that can polish an object to be polished at a high polishing rate in a polishing step and can be stably dressed.SOLUTION: There is provided a polishing pad containing 5 mass% or more of a hydrogenated block copolymer (A) that satisfies the following conditions (1) and (2), and having a static friction coefficient of 1.2 or less as measured in accordance with JIS K7125. Condition (1): The hydrogenated block copolymer (A) is a hydrogenated product of a block copolymer containing vinyl aromatic monomer units and conjugated diene monomer units. Condition (2): The hydrogenated block copolymer (A) contains at least one polymer block (a) mainly composed of vinyl aromatic monomer units, and a content of the polymer block (a) mainly composed of vinyl aromatic monomer units in the hydrogenated block copolymer (A) is 10 mass% or more.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] In the fabrication of integrated circuits and other electronic devices, multiple layers of conductive, semiconductive, and dielectric materials are deposited on or removed from the surface of a semiconductor wafer. Thin layers of conductive, semiconductive, and dielectric materials can be deposited by a number of deposition techniques. Common deposition techniques in modern processing include physical vapor deposition (PVD), also known as sputtering, chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), and electrochemical plating (ECP). As layers of material are sequentially deposited and removed, the top surface of the wafer becomes non-planar. Subsequent semiconductor processing (e.g., metallization) requires the wafer to have a flat surface, so the wafer requires planarization. Planarization is useful for removing undesirable surface topography and surface defects, such as rough surfaces, agglomerated materials, crystal lattice damage, scratches, and contaminated layers or materials.

[0003] Chemical mechanical planarization, or chemical mechanical polishing (CMP), is a common technique used to planarize substrates such as semiconductor wafers. In conventional CMP, a wafer is mounted on a carrier assembly and positioned in contact with a polishing pad in a CMP apparatus. The carrier assembly provides a controllable pressure to the wafer, pressing it against the polishing pad. The pad is moved (e.g., rotated) relative to the wafer by an external driving force. Simultaneously, a chemical composition ("slurry") or other polishing solution is provided between the wafer and the polishing pad. In this manner, the wafer surface is polished and planarized by the chemical and mechanical action of the pad surface and the slurry. A wide variety of compositions and methods are used to manufacture polishing pads. As used herein, the term "semiconductor wafer" is intended to encompass semiconductor substrates, such as unpatterned or patterned semiconductors, semiconductor devices, and various packages for various levels of interconnection, including single-chip or multi-chip wafers, substrates for light-emitting diodes (LEDs), or other assemblies requiring solder connections. Patent Document 1 discloses that a high polishing rate can be achieved by using a polishing pad containing a styrene-based thermoplastic elastomer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2023-58442 Summary of the Invention

[0005] However, it has been found that the polishing pad described in Patent Document 1 has a high coefficient of friction due to the inclusion of a styrene-based thermoplastic elastomer, and therefore dressing is not stable. [Problem to be solved by the invention]

[0006] In view of the above problems, an object of the present invention is to provide a polishing pad that can polish an object to be polished at a high polishing rate in a polishing process and can be stably dressed. [Means for solving the problem]

[0007] [1] A polishing pad containing 5% by mass or more of a hydrogenated block copolymer (a) that satisfies the following conditions (1) and (2), and having a static friction coefficient of 1.2 or less as measured in accordance with JIS K7125: <Condition (1)>: The hydrogenated block copolymer (a) is a hydrogenated product of a block copolymer containing vinyl aromatic monomer units and conjugated diene monomer units. <Condition (2)>: The hydrogenated block copolymer (a) contains at least one polymer block (a) mainly composed of vinyl aromatic monomer units, The content of the polymer block (a) mainly composed of vinyl aromatic monomer units in the hydrogenated block copolymer (i) is 10% by mass or more. [2] The hydrogenated block copolymer (a) contains at least one hydrogenated copolymer block (b) consisting of a vinyl aromatic monomer unit and a conjugated diene monomer unit, The polishing pad according to [1], wherein the content of vinyl aromatic monomer units in the hydrogenated copolymer block (b) is 5% by mass or more and 79% by mass or less. [3] The polishing pad according to [2], wherein the content of vinyl aromatic monomer units in the hydrogenated copolymer block (b) is 45% by mass or more and 79% by mass or less. [4] The polishing pad according to any one of [1] to [3], which contains 40% by mass or more of the hydrogenated block copolymer (i). [5] The polishing pad according to any one of [1] to [4], which contains 70% by mass or more of the hydrogenated block copolymer (i). [6] The polishing pad according to any one of [1] to [5], which has a dynamic friction coefficient of 0.6 or less as measured in accordance with JIS K7125. [7] The polishing pad according to any one of [1] to [6], wherein the content of the polymer block (a) mainly composed of vinyl aromatic monomer units in the hydrogenated block copolymer (i) is 15% by mass or more and 40% by mass or less. [Effects of the Invention]

[0008] A polishing pad capable of polishing an object to be polished at a high polishing rate in a polishing process and capable of being stably dressed can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0009] <Polishing pad> The polishing pad of this embodiment contains 5% by mass or more of a hydrogenated block copolymer (a) that satisfies the following conditions (1) and (2), and has a static friction coefficient of 1.2 or less as measured in accordance with JIS K7125. <Condition (1)>: The hydrogenated block copolymer (a) is a hydrogenated product of a block copolymer containing vinyl aromatic monomer units and conjugated diene monomer units. <Condition (2)>: The hydrogenated block copolymer (a) contains at least one polymer block (a) mainly composed of vinyl aromatic monomer units, The content of the polymer block (a) mainly composed of vinyl aromatic monomer units in the hydrogenated block copolymer (i) is 10% by mass or more.

[0010] The polishing pad of this embodiment includes the above-described configuration, and thus can polish an object to be polished at a high polishing rate in a polishing process and can perform stable dressing.

[0011] There are no particular limitations on the method for reducing the static friction coefficient to 1.2 or less. For example, if the amount of vinyl bonds in all conjugated diene monomer units of the hydrogenated block copolymer (i) is set to a certain value or less, the stickiness is reduced, and a polishing pad with a low coefficient of static friction can be obtained, which tends to exhibit stable dressing properties. When the content of all vinyl aromatic monomer units is equal to or greater than a certain value, the hydrogenated block copolymer (a) tends to produce a polishing pad with reduced stickiness and a low static friction coefficient, and exhibits stable dressing properties. When the content of polymer block (a) mainly composed of vinyl aromatic monomer units is equal to or greater than a certain value, the stickiness of hydrogenated block copolymer (a) is reduced, resulting in a decrease in the static friction coefficient, and the static friction coefficient of the polishing pad of this embodiment is also reduced, tending to exhibit stable dressing properties.

[0012] One example of a method for reducing the static friction coefficient is to reduce stickiness, for example, by reducing the amount of vinyl bonds in all conjugated diene monomer units in the hydrogenated block copolymer (a), or by increasing the content of polymer block (a) mainly composed of vinyl aromatic monomer units in the hydrogenated block copolymer (a). By distributing the bubble diameters over a relatively wide range, the static friction coefficient can be reduced when the polishing pad is formed. For example, if the difference between the bubble diameter at a cumulative volume frequency of 80% and the bubble diameter at a cumulative volume frequency of 20% (bubble diameter at a cumulative volume frequency of 80% - bubble diameter at a cumulative volume frequency of 20%) is large, the static friction coefficient can be reduced.

[0013] The polishing pad of this embodiment can also have its dynamic friction coefficient adjusted. Methods for reducing the dynamic friction coefficient include reducing the static friction coefficient of the hydrogenated block copolymer (A) itself, and adding an olefin resin (B).

[0014] (Hydrogenated Block Copolymer (A)) The hydrogenated block copolymer (a) used in the polishing pad of this embodiment is a hydrogenated product of a block copolymer containing vinyl aromatic monomer units and conjugated diene monomer units (the above-mentioned condition (1)).

[0015] <Vinyl aromatic monomer unit> Examples of vinyl aromatic compounds that form vinyl aromatic monomer units include, but are not limited to, monomer units derived from styrene, α-methylstyrene, p-methylstyrene, divinylbenzene, 1,1-diphenylethylene, N,N-dimethyl-p-aminoethylstyrene, and N,N-diethyl-p-aminoethylstyrene. In particular, styrene is preferred from the viewpoint of the balance between cost and the mechanical strength of the polishing pad containing the hydrogenated block copolymer (a). These may be used alone or in combination of two or more.

[0016] <Conjugated diene monomer unit> A conjugated diene monomer unit is a monomer unit derived from a diolefin having a pair of conjugated double bonds. Examples of such diolefins include, but are not limited to, 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, and 1,3-hexadiene. In particular, 1,3-butadiene and isoprene are preferred from the viewpoint of a good balance between moldability and mechanical strength. These may be used alone or in combination of two or more.

[0017] In this specification, in the composition of the hydrogenated block copolymer (a), the term "mainly composed of" means that the proportion in a given block polymer or polymer block is 85% by mass or more, preferably 90% by mass or more, and more preferably 95% by mass or more. Since the content of vinyl aromatic monomer units in the hydrogenated copolymer block (b) is 5% by mass or more and 79% by mass or less (the above-mentioned [2]), the polymer block (a) and the hydrogenated copolymer block (b) can be clearly distinguished from each other.

[0018] <Amount of vinyl bonds in all conjugated diene monomer units> The amount of vinyl bonds in all conjugated diene monomer units of the hydrogenated block copolymer (a) is not particularly limited, but is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. In addition, it is preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 70% by mass or less. In this specification, the term "vinyl bond content" refers to the total amount of conjugated diene monomer units bonded via 1,2-vinyl bonds (conjugated dienes incorporated into the polymer via 1,2-bonds) and 3,4-vinyl bonds (conjugated dienes incorporated into the polymer via 3,4-bonds) relative to all conjugated dienes (however, when 1,3-butadiene is used as the conjugated diene, this refers to the 1,2-vinyl bond content), and is a concept that also includes the state in which 1,2-vinyl bonds or 3,4-vinyl bonds are subsequently hydrogenated to form single bonds. In other words, although "vinyl" is a term that represents the state of double bonds, the "vinyl bond content" in this specification encompasses the amount of vinyl bonds that have been hydrogenated to form single bonds. When measured during the production process of a hydrogenated block copolymer, the total amount of 1,2-vinyl bonds and 3,4-vinyl bonds relative to all conjugated dienes measured before the hydrogenation process corresponds to the "vinyl bond content." When the amount of vinyl bonds in all conjugated diene monomer units of the hydrogenated block copolymer (a) is 5% by mass or more, precipitation from the solution due to crystallization of the hydrogenated conjugated diene block can be suppressed in the hydrogenation step. Furthermore, when the amount of vinyl bonds in all conjugated diene monomer units of the hydrogenated block copolymer (a) is 5% by mass or more, good compatibility with the olefin resin (b) described below is exhibited. Furthermore, when the amount of vinyl bonds in all conjugated diene monomer units of the hydrogenated block copolymer (i) is 80 mass% or less, the stickiness is reduced, and a polishing pad with a low static friction coefficient can be obtained, which tends to exhibit stable dressing properties.

[0019] The vinyl bond content in all conjugated diene monomer units of the hydrogenated block copolymer (a) can be controlled within the above numerical range by using a regulator such as a tertiary amine compound or an ether compound, which will be described later. The amount of vinyl bonds in all conjugated diene monomer units of the hydrogenated block copolymer (A) can be measured by nuclear magnetic resonance (NMR) using the block copolymer before hydrogenation as a sample, or by an infrared spectrophotometer as described in the Examples below. Furthermore, in the nuclear magnetic resonance (NMR) measurement using the hydrogenated block copolymer as a sample, the amount of vinyl bonds can be calculated by counting the total number of structures that have been hydrogenated into single bonds in addition to unhydrogenated vinyl structures.

[0020] <Total vinyl aromatic compound content> The hydrogenated block copolymer (a) preferably has a total vinyl aromatic monomer unit content of 40% by mass or more and 80% by mass or less, more preferably 50% by mass or more and 80% by mass or less, and even more preferably 60% by mass or more and 80% by mass or less. When the content of all vinyl aromatic monomer units is 40% by mass or more, the hydrogenated block copolymer (i) can produce a polishing pad with reduced stickiness and a low static friction coefficient, and tends to exhibit stable dressing properties. When the total content of vinyl aromatic monomer units is 80% by mass or less, the polishing pad of this embodiment has improved adhesion to the workpiece, and can exhibit high planarization performance in the polishing process. The total content of vinyl aromatic monomer units in the hydrogenated block copolymer (a) can be measured using an ultraviolet spectrophotometer with the block copolymer before hydrogenation and the hydrogenated block copolymer after hydrogenation as samples. The total content of vinyl aromatic monomer units in the hydrogenated block copolymer (a) can be controlled within the above-mentioned range mainly by adjusting the amount of vinyl aromatic compound added to the polymerization reactor, the reaction temperature, and the reaction time.

[0021] <Polymer block (a) mainly composed of vinyl aromatic monomer units> The hydrogenated block copolymer (a) used in the polishing pad of this embodiment contains at least one polymer block (a) mainly composed of vinyl aromatic monomer units (condition (2) above), which can prevent pellet blocking. Furthermore, the content of polymer block (a) in the hydrogenated block copolymer (i) is 10% by mass or more, preferably 15% by mass or more, and more preferably 20% by mass or more, from the viewpoint of reducing the static friction coefficient. When the content of polymer block (a) mainly composed of vinyl aromatic monomer units is 10% by mass or more, the stickiness of the hydrogenated block copolymer (a) is reduced, thereby reducing the static friction coefficient, and the static friction coefficient of the polishing pad of this embodiment is reduced, tending to exhibit stable dressing properties.

[0022] Furthermore, the hydrogenated block copolymer (i) preferably has a polymer block (a) content of 50% by mass or less, more preferably 48% by mass or less, even more preferably 46% by mass or less, and even more preferably 45% by mass or less. When the content of polymer block (a) mainly composed of vinyl aromatic monomer units in the hydrogenated block copolymer (i) is 50 mass% or less, the polishing pad of this embodiment has improved adhesion to the workpiece, and can exhibit high planarization performance in the polishing process.

[0023] The content of polymer block (a) in hydrogenated block copolymer (i) can be measured by a method using a nuclear magnetic resonance (NMR) spectrometer (the method described in Y. Tanaka, et al., RUBBER CHEMISTRY and TECHNOLOGY 54, 685 (1981), hereinafter referred to as the "NMR method") using the block copolymer before hydrogenation and the hydrogenated block copolymer as samples. The content of polymer block (a) in the hydrogenated block copolymer (i) can be controlled within the above-mentioned range mainly by adjusting the amount of vinyl aromatic compound added to the polymerization reactor, the reaction temperature, and the reaction time.

[0024] <Hydrogenated copolymer block (b)> The content of the polymer block (b) in the hydrogenated block copolymer (a) is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more. When the content of vinyl aromatic monomer units in the hydrogenated copolymer block (b) is 40% by mass or more, the polishing pad of this embodiment has improved wear resistance during the polishing process, making it possible to maintain a high polishing rate for a long period of time.

[0025] The hydrogenated block copolymer (i) used in the polishing pad of this embodiment preferably contains at least one hydrogenated copolymer block (b) consisting of a vinyl aromatic monomer unit and a conjugated diene monomer unit. The content of vinyl aromatic monomer units in the hydrogenated copolymer block (b) is preferably 5% by mass or more, more preferably 15% by mass or more, even more preferably 30% by mass or more, and particularly preferably 45% by mass or more. When the content of vinyl aromatic monomer units in the hydrogenated copolymer block (b) is 5% by mass or more, the polishing pad of this embodiment has improved wear resistance during the polishing step, allowing it to maintain a high polishing rate for a long period of time, resulting in excellent durability. The content of vinyl aromatic monomer units in the hydrogenated copolymer block (b) is preferably 79% by mass or less, more preferably 75% by mass or less, and even more preferably 70% by mass or less. When the content of vinyl aromatic monomer units in the hydrogenated copolymer block (b) is 79 mass% or less, the polishing pad of this embodiment has improved adhesion to the workpiece, and can exhibit high planarization performance in the polishing process.

[0026] The content of the vinyl aromatic monomer unit in the hydrogenated copolymer block (b) can be measured by a nuclear magnetic resonance (NMR) spectrometer or the like. The content of the vinyl aromatic monomer unit in the hydrogenated copolymer block (b) can be controlled within the above-mentioned range by adjusting the amounts of the vinyl aromatic compound and conjugated diene added to the polymerization reactor, the reaction temperature, etc.

[0027] <Weight average molecular weight of hydrogenated block copolymer (a)> The weight-average molecular weight (Mw) of the hydrogenated block copolymer (A) used in the polishing pad of this embodiment is preferably 10,000 or more, more preferably 30,000 or more, and even more preferably 50,000 or more, from the viewpoints of extrusion moldability during pellet production of the hydrogenated block copolymer (A) and obtaining good mechanical strength and low stickiness in the polishing pad of this embodiment. The upper limit is preferably 400,000 or less, more preferably 300,000 or less, and even more preferably 250,000 or less. When the weight average molecular weight (Mw) is 300,000 or less, the hydrogenated block copolymer (A) tends to be easily melted during pellet production (extrusion molding) of the hydrogenated block copolymer (A), resulting in stable strands and improved extrusion moldability. The weight average molecular weight of the hydrogenated block copolymer (a) is determined by gel permeation chromatography (GPC) using a calibration curve (prepared using the peak molecular weight of the standard polystyrene) obtained from measurements of commercially available standard polystyrene.

[0028] <Molecular weight distribution (Mw / Mn) of hydrogenated block copolymer (A)> The hydrogenated block copolymer (A) used in the polishing pad of this embodiment has a molecular weight distribution (Mw / Mn) that is not particularly limited, but from the viewpoint of processability, is preferably 10 or less, more preferably 3 or less, and even more preferably 1.5 or less. From the viewpoint of processability, the lower limit of Mw / Mn is preferably 1 or more, more preferably 1.005 or more, and even more preferably 1.01 or more. The weight average molecular weight (Mw) and number average molecular weight (Mn) of the hydrogenated block copolymer (A) are measured by gel permeation chromatography (GPC), and the molecular weight of the peak in the chromatogram is determined using a calibration curve (created using the peak molecular weight of the standard polystyrene) obtained from measurements of commercially available standard polystyrene. The molecular weight distribution (Mw / Mn) of the hydrogenated block copolymer (A) is determined from the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn).

[0029] <Hydrogenation rate of double bonds of conjugated diene monomer units in hydrogenated block copolymer (a)> The hydrogenation rate of the double bonds of the conjugated diene monomer units in the hydrogenated block copolymer (i) used in the polishing pad of this embodiment is not particularly limited, but from the viewpoint of obtaining good heat resistance, it is preferably 30% or more, more preferably 50% or more, even more preferably 85% or more, and even more preferably 92% or more. The hydrogenation rate of the double bonds of the conjugated diene monomer units in the hydrogenated block copolymer (A) can be controlled within the above-mentioned range by adjusting the amount of hydrogenation. The hydrogenation rate of the hydrogenated block copolymer (A) can be measured using a nuclear magnetic resonance (NMR) spectrometer or the like.

[0030] <Structure of hydrogenated block copolymer (A)> (Structure of hydrogenated block copolymer (A)) The structure of the hydrogenated block copolymer (a) of this embodiment is not particularly limited, but examples thereof include those having a structure represented by the following general formula: aba, (ab) n -X, c-(ba) n , c-(ab) n , c-(aba) n , c-(bab) n , c-(bca) n , a-(cbca) n , ac-(ba) n , ac-(ab) n , ac-(ba) n -b, ca-(ba) n -c, ac-(ba) n -c, ab-(ca) n -b, ac-(bc) n -ac, c-(abc) n -ac, a-(cb) n -ca, c-(ac) n -bcac, [(abc) n ] m -X, [a-(bc) n ] m -X, [(ab) n -c]m -X, [(aba) n -c] m -X, [(bab) n -c] m -X, [(cba) n ] m -X, [c-(ba) n ] m -X, [c-(aba) n ] m -X, [c-(bab) n ] m -X In each of the above general formulas, a represents a polymer block (a) mainly composed of vinyl aromatic monomer units, b represents a hydrogenated copolymer block (b) composed of vinyl aromatic monomer units and conjugated diene monomer units, and c represents a hydrogenated polymer block (c) mainly composed of conjugated diene monomer units. n is an integer of 1 or more, and preferably an integer of 1 to 5. m is an integer of 2 or more, and preferably an integer of 2 to 11. X represents a residue of a coupling agent or a residue of a multifunctional initiator.

[0031] <Static friction coefficient of hydrogenated block copolymer (a)> The static friction coefficient of the hydrogenated block copolymer (i) used in the polishing pad of this embodiment is preferably 2.5 or less, more preferably 2 or less, and even more preferably 1.7 or less, from the viewpoint of reducing the static friction coefficient of the polishing pad. One example of a method for reducing the static friction coefficient is to reduce stickiness, for example, the above-mentioned (ab) n In -X polymer polymerization, the unreacted components during the diblock polymer coupling reaction are reduced, the amount of vinyl bonds in all conjugated diene monomer units in the hydrogenated block copolymer (A) is reduced, and the content of polymer block (a) mainly composed of vinyl aromatic monomer units in the hydrogenated block copolymer (A) is increased. The static friction coefficient can be measured in accordance with JIS K7125.

[0032] <Dynamic friction coefficient of hydrogenated block copolymer (a)> The dynamic friction coefficient of the hydrogenated block copolymer (i) used in the polishing pad of this embodiment is preferably 1 or less, more preferably 0.8 or less, and even more preferably 0.5 or less, from the viewpoint of reducing the dynamic friction coefficient of the polishing pad. Methods for reducing the dynamic friction coefficient include the above-mentioned method of lowering the static friction coefficient and a method of increasing the content of vinyl aromatic monomer units in the hydrogenated copolymer block (b). The dynamic friction coefficient can be measured in accordance with JIS K7125.

[0033] <Hardness of hydrogenated block copolymer (A)> When the hydrogenated block copolymer (i) is used in a polishing pad, the instantaneous hardness measured with a durometer type A according to JIS K6253 is preferably 60 or more, more preferably 70 or more, even more preferably 80 or more, and even more preferably 85 or more, from the viewpoint of suppressing edge droop of the semiconductor during semiconductor polishing. Furthermore, when used in a polishing pad, from the viewpoint of suppressing scratches on the substrate, the instantaneous hardness measured with a durometer type D according to JIS K6253 is preferably 70 or less, more preferably 60 or less, and even more preferably 50 or less.

[0034] The hardness of the hydrogenated block copolymer (a) can be controlled within the above-mentioned range by adjusting the weight-average molecular weight of the hydrogenated block copolymer (a), the content of polymer block (a), the content of vinyl aromatic monomer units in the hydrogenated copolymer block (b), the content of hydrogenated polymer block (c), the amount of vinyl bonds in the conjugated diene monomer units, and the hydrogenation rate of double bonds in the conjugated diene monomer units. Furthermore, the hardness may be controlled within the above-mentioned range by adjusting the tan δ peak temperature (loss tangent) between −25° C. and 60° C. in the viscoelasticity measurement chart of the hydrogenated block copolymer (a), i.e., the glass transition temperature derived from the hydrogenated copolymer block (b), by carrying out a polymerization reaction under the conditions described below using a predetermined adjuster that adjusts the vinyl bond amount in the hydrogenated copolymer block (b), the content of the vinyl aromatic monomer unit in the hydrogenated copolymer block (b), and the copolymerizability between the vinyl aromatic compound and the conjugated diene. For example, increasing the content of polymer block (a) in hydrogenated block copolymer (a), increasing the content of vinyl aromatic monomer units in hydrogenated copolymer block (b), decreasing the content of hydrogenated polymer block (c), decreasing the hydrogenation rate of double bonds in conjugated diene monomer units, and increasing the tan δ peak temperature (°C) from -20 to 60°C tend to improve the hardness of hydrogenated block copolymer (a). Increasing the content of vinyl aromatic monomer units in hydrogenated copolymer block (b) and increasing the vinyl bond content of hydrogenated copolymer block (b) are particularly effective in improving the tan δ peak temperature (°C) from -20 to 60°C. The tan δ peak temperature (°C) can also be controlled by adjusting the copolymerizability of the vinyl aromatic compound and the conjugated diene by adjusting the polymerization conditions, as described below.

[0035] (Tan δ (loss tangent) peak temperature in the viscoelasticity measurement chart of hydrogenated block copolymer (A)) In the viscoelasticity measurement chart, the hydrogenated block copolymer (A) of this embodiment preferably has at least one tan δ (loss tangent) peak between −25° C. and 60° C. More preferably, it has at least one peak between −15° C. and 50° C., even more preferably between −5° C. and 40° C., and even more preferably between 0° C. and 30° C. This tan δ peak is a peak due to the hydrogenated copolymer block (b) in the hydrogenated block copolymer (a). The presence of at least one such peak in the range of −25° C. to 60° C. is preferred from the viewpoint of improving the planarization performance of the polishing pad during polishing. As described above, the hydrogenated copolymer block (b) is obtained by hydrogenating a copolymer block composed of conjugated diene monomer units and vinyl aromatic monomer units. In the hydrogenated block copolymer (a) of this embodiment, in order to have at least one peak of tanδ (loss tangent) in the range of −25° C. or higher and 60° C. or lower, it is effective to control the conjugated diene monomer unit / vinyl aromatic monomer unit (mass ratio), and the conjugated diene monomer unit / vinyl aromatic monomer unit (mass ratio) is preferably 79 / 21 to 16 / 84, more preferably 75 / 35 to 18 / 82, and even more preferably 70 / 30 to 25 / 75. In order to have at least one peak of tanδ (loss tangent) in the range of 0°C or higher and 30°C or lower, it is effective to control the conjugated diene monomer unit / vinyl aromatic monomer unit (mass ratio), and the conjugated diene monomer unit / vinyl aromatic monomer unit (mass ratio) is preferably 65 / 35 to 16 / 84, more preferably 60 / 40 to 25 / 75, and even more preferably 55 / 45 to 30 / 70. To obtain the hydrogenated block copolymer (a) having at least one peak of tanδ (loss tangent) in the range of −25° C. to 60° C., a block copolymer obtained by carrying out a polymerization reaction under the conditions described below using a predetermined regulator that adjusts the vinyl bond amount in the hydrogenated copolymer block (b), the content of the vinyl aromatic monomer unit in the hydrogenated copolymer block (b), and the copolymerizability between the vinyl aromatic compound and the conjugated diene may be subjected to a hydrogenation reaction. The tan δ of the hydrogenated block copolymer (a) can be measured using a viscoelasticity measuring device (ARES, manufactured by TA Instruments Co., Ltd.) under conditions of a strain of 0.5%, a frequency of 1 Hz, and a heating rate of 3° C. / min.

[0036] (Method for producing hydrogenated block copolymer composition) The hydrogenated block copolymer composition that is the raw material for the polishing pad of this embodiment can be produced by a conventionally known method. The method for producing the hydrogenated block copolymer composition of this embodiment is not limited to the following, but examples thereof include a method of melt-kneading the components (the hydrogenated block copolymer (A), the polyolefin resin (B) described below, and other additives as necessary) using a mixer such as a Banbury mixer, a single-screw extruder, a twin-screw extruder, a co-kneader, or a multi-screw extruder, and a method of dissolving or dispersing the components and then removing the solvent by heating. In particular, the melt-kneading method using an extruder is preferable from the viewpoint of productivity and good kneading properties. The shape of the hydrogenated block copolymer composition is not limited to the following, and it may be in any shape, such as pellets, sheets, strands, chips, etc. Alternatively, after melt-kneading, a molded article may be produced directly.

[0037] (Hardness of Hydrogenated Block Copolymer Composition) The hydrogenated block copolymer composition used as the raw material for the polishing pad of this embodiment preferably has a viscosity of 60 or more, more preferably 70 or more, even more preferably 80 or more, and even more preferably 85 or more, from the viewpoint of suppressing edge droop of the semiconductor during polishing, when used in the polishing pad. Furthermore, when used in a polishing pad, in order to prevent scratches on the substrate, the instantaneous hardness measured with a durometer type D according to JIS K6253 is preferably 70 or less, more preferably 60 or less, and even more preferably 50 or less.

[0038] The hardness of the hydrogenated block copolymer composition can be controlled by adjusting the hardness of the hydrogenated block copolymer (A) contained in the hydrogenated block copolymer composition, the flexural modulus of component (B), and the composition ratio of components (A) to (B).

[0039] (Static Friction Coefficient of Hydrogenated Block Copolymer Composition) The static friction coefficient of the hydrogenated block copolymer composition used in the polishing pad of this embodiment is preferably 2.5 or less, more preferably 2 or less, and even more preferably 1.7 or less, from the viewpoint of reducing the static friction coefficient of the polishing pad. In addition to reducing the static friction coefficient of the hydrogenated block copolymer (a) itself, the static friction coefficient can be reduced by adding an olefin resin (b). The static friction coefficient can be measured in accordance with JIS K7125.

[0040] (Dynamic Friction Coefficient of Hydrogenated Block Copolymer Composition) The static friction coefficient of the hydrogenated block copolymer composition used in the polishing pad of this embodiment is preferably 1 or less, more preferably 0.8 or less, and even more preferably 0.5 or less, from the viewpoint of reducing the dynamic friction coefficient of the polishing pad. The dynamic friction coefficient can be reduced by adding an olefin resin (ii) to the hydrogenated block copolymer (ii) in addition to reducing the static friction coefficient of the hydrogenated block copolymer (ii). The dynamic friction coefficient can be measured in accordance with JIS K7125.

[0041] <Olefin resin (b)> The hydrogenated block copolymer composition constituting the foam of the present embodiment contains an olefin resin (ii). The olefin-based resin (ii) used in the foam of this embodiment includes, but is not limited to, homopolymers of α-olefins such as polyethylene (PE), polypropylene (PP), 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 4-methyl-1-pentene, 1-octene, etc. Also included are random copolymers or block copolymers made of a combination of olefins selected from ethylene, propylene, butene, pentene, hexene, octene, etc. Specific examples include ethylene and / or propylene-α-olefin copolymers such as ethylene-propylene copolymer, ethylene-1-butene copolymer, ethylene-3-methyl-1-butene copolymer, ethylene-4-methyl-1-pentene copolymer, ethylene-1-hexene copolymer, ethylene-1-octene copolymer, ethylene-1-decene copolymer, propylene-1-butene copolymer, propylene-1-hexene copolymer, propylene-1-octene copolymer, propylene-4-methyl-1-pentene copolymer, ethylene-propylene-1-butene copolymer, propylene-1-hexene-ethylene copolymer, and propylene-1-octene-ethylene copolymer. Furthermore, the copolymers with ethylene and / or propylene also include copolymers with other unsaturated monomers other than the above α-olefins. Examples of the copolymer with other unsaturated monomers include, but are not limited to, copolymers of ethylene and / or propylene with unsaturated organic acids or derivatives thereof, such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, methyl acrylate, methyl methacrylate, maleic anhydride, arylmaleimide, and alkylmaleimide; copolymers of ethylene and / or propylene with vinyl esters, such as vinyl acetate; and copolymers of ethylene and / or propylene with non-conjugated dienes, such as dicyclopentadiene, 4-ethylidene-2-norbornene, 4-methyl-1,4-hexadiene, and 5-methyl-1,4-hexadiene. (b) The olefin-based resin preferably contains at least one type of polypropylene-based resin from the viewpoints of economy and of achieving good compatibility in the hydrogenated block copolymer composition constituting the foam of the present embodiment and thereby obtaining high transparency.

[0042] The olefin resin (ii) may be modified with a predetermined functional group. The functional group is not particularly limited, but examples thereof include an epoxy group, a carboxy group, an acid anhydride group, and a hydroxyl group. The functional group-containing compound or modifier for modifying the olefin resin (ii) is not particularly limited, but the following compounds may be mentioned. Examples include unsaturated epoxides such as glycidyl methacrylate, glycidyl acrylate, vinyl glycidyl ether, and allyl glycidyl ether, and unsaturated organic acids such as maleic acid, fumaric acid, itaconic acid, citraconic acid, allyl succinic acid, maleic anhydride, fumaric anhydride, and itaconic anhydride.Other examples include, but are not limited to, ionomers and chlorinated polyolefins.

[0043] The olefin-based resin (b) is preferably a polypropylene-based resin such as a polypropylene homopolymer or an ethylene-propylene random or block copolymer, from the viewpoints of economy and achieving good compatibility in the hydrogenated block copolymer composition constituting the foam of this embodiment and thereby achieving high transparency. In particular, ethylene-propylene random copolymers are more preferable in terms of transparency and flexibility. The olefin-based resin (ii) may be composed of only one type of material, or may be composed of two or more types in combination.

[0044] <Content of Component (A) in the Hydrogenated Block Copolymer Composition> The content of hydrogenated block copolymer (A) in the hydrogenated block copolymer composition serving as a raw material for the polishing pad of this embodiment is 5% by mass or more, preferably 40% by mass or more, and more preferably 70% by mass or more, from the viewpoint of improving the polishing rate and planarization performance in the polishing process of semiconductors when used as a polishing pad. The upper limit may be 100% by mass. Furthermore, when the content of the hydrogenated block copolymer (a) in the hydrogenated block copolymer composition is 40% by mass or more, the polishing rate is superior.

[0045] [Foam] The polishing pad of this embodiment is preferably a foam. In this embodiment, the foam comprises air bubbles. Since the polishing pad of this embodiment is made of foam, the static friction coefficient can be easily adjusted to fall within a predetermined range.

[0046] (Average cell diameter, distribution, and closed cell ratio of foam) The average cell diameter of the foam used in this embodiment is not particularly limited, but from the viewpoint of suppressing clogging of slurry particles while maintaining good particle retention, it is preferably 20 to 500 μm, more preferably 30 to 300 μm, and particularly preferably 40 to 200 μm. The average cell diameter of the foam used in this embodiment can be determined as the arithmetic mean value of the cell diameters determined from the volume of each cell, as described below.

[0047] The cell diameter distribution of the foam can be determined from the volumetric cell diameter distribution curve described below. From the viewpoint of adjusting the static friction coefficient within the above range, the difference between the bubble diameter at a cumulative volume frequency of 80% and the bubble diameter at a cumulative volume frequency of 20% is preferably 50 μm or more. If the difference between the bubble diameter at a cumulative volume frequency of 80% and the bubble diameter at a cumulative volume frequency of 20% (bubble diameter at a cumulative volume frequency of 80% - bubble diameter at a cumulative volume frequency of 20%) is large, the bubble diameters can be distributed over a relatively wide range, which reduces the static friction coefficient of the resulting polishing pad.

[0048] The closed cell ratio of the foam is determined by measuring the closed cell ratio (%) of the foam in accordance with ASTM D1940-62T. The closed cell ratio is not particularly limited, but is preferably 5% or more, more preferably 7% or more, and particularly preferably 10% or more, from the viewpoint of maintaining good slurry particle retention.

[0049] The average cell diameter, cell distribution and closed cell ratio of the foam used in the polishing pad can be adjusted by changing the amount of the foaming agent, the viscosity of the composition and the foaming conditions.

[0050] The volume-based bubble diameter distribution curve can be determined as follows using an X-ray CT scanner (for example, TDM1000H-I manufactured by Yamato Scientific Co., Ltd.). That is, the volume of each bubble contained in the measurement area of ​​the resin foam is measured, and the diameter of each bubble is determined as the diameter of a sphere having the same volume as this volume. Here, the above-mentioned "average bubble diameter" means the arithmetic mean value of the bubble diameters calculated from the volume of each bubble [= total value of "each bubble diameter" / (number of bubbles)]. The volume-based bubble diameter distribution curve can be determined based on data on the number-based bubble diameter distribution curve. That is, the number of bubbles is calculated at regular intervals starting from a bubble diameter of 0 μm, and the "number of bubbles at each interval" is set as the "number of bubbles at the upper limit of each interval." This is used to calculate a number-based bubble diameter distribution curve. Based on this number-based bubble diameter distribution curve data, the total volume of bubbles is calculated at regular intervals starting from a bubble diameter of 0 μm, and the "total volume of bubbles" is set as the "volume at the upper limit of each interval." This is used to calculate a volume-based bubble diameter distribution curve. It is preferable that the above-mentioned fixed interval be set to 20 μm or less in order to determine the peak position with higher accuracy.

[0051] [Method for producing foam] The method for producing the polishing pad foam of this embodiment is not particularly limited, but for example, a method is available in which a foam is produced by adding a blowing agent and a crosslinking agent to a hydrogenated block copolymer composition, melting and kneading the mixture, and then heating and foaming the mixture in a mold. The foam can be cut to a desired size and used as a polishing pad.

[0052] The crosslinking agent used in this embodiment is not particularly limited, but is preferably a radical generator that has a decomposition temperature equal to or higher than the flow initiation temperature of the resin used and that decomposes upon heating to generate free radicals that cause inter- or intra-molecular crosslinking. Specific examples include organic peroxides such as dicumyl peroxide, 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di-t-butylperoxyhexane, 2,5-dimethyl-2,5-di-tert-butylperoxyhexyne, α,α-ditert-butylperoxydiisopropylbenzene, tert-butyl peroxyketone, and tert-butyl peroxybenzoate. However, the optimum organic peroxide must be selected depending on the type of resin used.

[0053] The foaming agent is not particularly limited, but inorganic foaming agents, organic foaming agents, and physical foaming agents can be used. Examples of inorganic foaming agents include, but are not limited to, sodium bicarbonate, ammonium carbonate, ammonium bicarbonate, ammonium nitrite, azide compounds, sodium borohydride, aluminum acetate, and metal powder. Examples of organic blowing agents include, but are not limited to, azodicarbonamide, azobisformamide, azobisisobutyronitrile, barium azodicarboxylate, N,N'-dinitrosopentamethylenetetramine, N,N'-dinitroso-N,N'-dimethylterephthalamide, benzenesulfonyl hydrazide, p-toluenesulfonyl hydrazide, p,p'-oxybisbenzenesulfonyl hydrazide, and p-toluenesulfonylsemicarbazide. Examples of physical blowing agents include, but are not limited to, hydrocarbons such as pentane, butane, and hexane; halogenated hydrocarbons such as methyl chloride and methylene chloride; gases such as nitrogen, carbon dioxide, and air; and fluorinated hydrocarbons such as trichlorofluoromethane, dichlorodifluoromethane, trichlorotrifluoroethane, chlorodifluoroethane, and hydrofluorocarbons. These blowing agents may also be used in combination.

[0054] (foaming aid) In the step of producing the foam, a foaming assistant may be used together with the foaming agent. The foaming aid is not particularly limited, and any foaming aid that has been conventionally used for general purposes can be used. Examples include urea compounds, zinc compounds such as zinc oxide, zinc stearate, zinc benzenesulfinate, zinc toluenesulfonate, zinc trifluoromethanesulfonate and zinc carbonate, lead compounds such as lead dioxide and lead tribasic.

[0055] (foam nucleating agent) In the foam production process, a foam nucleating agent may be used. The foam nucleating agent is not particularly limited, and any of those conventionally used as foam nucleating agents can be used. Examples include titanium oxide, talc, kaolin, clay, calcium silicate, silica, sodium citrate, calcium carbonate, diatomaceous earth, calcined perlite, zeolite, bentonite, glass, limestone, calcium sulfate, aluminum oxide, titanium oxide, magnesium carbonate, sodium carbonate, ferric carbonate, and polytetrafluoroethylene powder.

[0056] (Expansion ratio) The expansion ratio of the foam used in this embodiment is not particularly limited, but is preferably 1.5 to 4 times, more preferably 1.7 to 3.5 times or more, and particularly preferably 2 to 3 times or more from the viewpoint of obtaining a good polishing rate.

[0057] The expansion ratio of the foam can be adjusted by changing the amount of the foaming agent, the viscosity of the composition, and the foaming conditions.

[0058] The shape of the polishing substrate of the polishing pad of this embodiment is not particularly limited, but can be, for example, disc-shaped, polygonal pillar-shaped, etc., and can be selected appropriately depending on the polishing apparatus to which the polishing pad of this embodiment is attached and used. The size of the polishing substrate is not particularly limited, but for example, in the case of a disc-shaped polishing pad, the diameter may be 150 to 1200 mm, preferably 500 to 800 mm, and the thickness may be 1.0 to 5.0 mm, preferably 1.5 to 3.0 mm.

[0059] The polishing substrate of the polishing pad of this embodiment may have grooves on the polishing surface, which hold the aqueous dispersion supplied during polishing and distribute it more uniformly over the polishing surface, and also serve as a path for temporarily retaining and discharging waste such as polishing debris and used aqueous dispersion to the outside. The shape of the grooves is not particularly limited, but may be, for example, spiral, concentric, or radial. The polishing substrate of the polishing pad of this embodiment may have recesses on the non-polishing surface (back surface), which serve to relieve localized excessive stress that may occur during polishing and more effectively suppress the occurrence of surface defects such as scratches on the polished surface.

[0060] The shape of the recesses is not particularly limited, but may be, for example, circular, polygonal, spiral, concentric, radial, or the like. The polishing pad of this embodiment may also include a portion having a function other than the polishing portion. Examples of portions having other functions include a window portion for detecting the end point using an optical end point detector. For example, the window portion may be made of a material having a thickness of 2 mm, a transmittance of light at any wavelength between 100 and 300 nm of preferably 0.1% or more, more preferably 2% or more, or an integrated transmittance in any wavelength range between 100 and 300 nm of preferably 0.1% or more, more preferably 2% or more. The material for the window portion is not particularly limited as long as it satisfies the above optical properties, but may have a composition similar to that of the polishing substrate described above.

[0061] The method for manufacturing the polishing substrate constituting the polishing pad of this embodiment is not particularly limited, and the method for forming the grooves and recesses (hereinafter, both are collectively referred to as "grooves, etc.") that the polishing substrate may optionally have is also not particularly limited. For example, a chemical mechanical polishing pad composition that will serve as the polishing substrate of the polishing pad is prepared in advance, and this composition is molded into the desired general shape, and then grooves, etc. can be formed by cutting. Furthermore, by mold-molding the polishing pad composition using a mold on which a pattern that will become grooves, etc. is formed, grooves, etc. can be formed simultaneously with the general shape of the polishing substrate.

[0062] The method for obtaining the composition for a polishing pad is not particularly limited. For example, the composition can be obtained by kneading necessary materials such as predetermined organic materials using a kneader or the like. As the kneader, a conventionally known kneader can be used. For example, kneaders such as a roll, a kneader, a Banbury mixer, and an extruder (single-screw or multi-screw) can be used.

[0063] The polishing pad of this embodiment may consist of only the polishing substrate as described above, or may be a multi-layer pad having a support layer on the non-polishing surface side of the polishing substrate as described above.

[0064] The support layer is a layer that supports the polishing substrate on the back side of the polishing surface. The properties of this support layer are not particularly limited, but it is preferable that it is softer than the polishing substrate. By providing a softer support layer, even if the polishing substrate is thin, for example, 1.0 mm or less, it can prevent the polishing substrate from floating up during polishing, or the surface of the polishing layer from curving, and can perform polishing stably.

[0065] The support layer may be porous (foamed) or non-porous. Furthermore, its planar shape is not particularly limited, and may be the same as or different from the polishing layer. The planar shape of the support layer may be, for example, circular, polygonal (e.g., rectangular), or the like. The thickness is not particularly limited, but is preferably 0.1 to 5 mm, and more preferably 0.5 to 2 mm. The material for forming the support layer is not particularly limited, but it is preferable to use an organic material, since it can be easily molded into a predetermined shape and properties and can be given appropriate elasticity. The polishing pad of this embodiment as described above can suppress the occurrence of scratches on the surface to be polished, and can provide a high-quality polished surface.

[0066] The polishing pad may be a polishing pad in which a nonwoven fabric substrate or a suede substrate is impregnated with a solution of the hydrogenated block copolymer (a).

[0067] The fibers contained in the nonwoven fabric of the nonwoven fabric substrate are not particularly limited, and examples thereof include aromatic polyester fibers including one or more of polyethylene terephthalate (PET), isophthalic acid-modified polyethylene terephthalate, sulfoisophthalic acid-modified polyethylene terephthalate, polybutylene terephthalate, and polyhexamethylene terephthalate; and aliphatic polyesters including one or more of polylactic acid, polyethylene succinate, polybutylene succinate, polybutylene succinate adipate, and polyhydroxybutyrate-polyhydroxyvalerate copolymers. These include polyamide fibers containing one or more of polyamide 6, polyamide 66, polyamide 10, polyamide 11, polyamide 12, and polyamide 6-12; polyolefin fibers containing one or more of polypropylene, polyethylene, polybutene, polymethylpentene, and chlorinated polyolefins; modified polyvinyl alcohol fibers containing modified polyvinyl alcohol containing 25 to 70 mol% of ethylene units; and elastomeric fibers containing elastomers such as polyurethane elastomers, polyamide elastomers, and polyester elastomers. These may be used alone or in combination of two or more.

[0068] The solvent used for solution impregnation is not particularly limited, but examples thereof include methyl ethyl ketone (MEK); aliphatic hydrocarbons such as n-butane, isobutane, n-pentane, n-hexane, n-heptane, and n-octane; alicyclic hydrocarbons such as cyclohexane, cycloheptane, and methylcycloheptane; and aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene.

[0069] <Hardness of polishing pad> When used as a polishing pad, the instantaneous hardness value of the polishing pad, measured using a durometer type A in accordance with JIS K6253 or a spring-type Asker C type in accordance with SRIS 0101, is preferably 30C or more, more preferably 35C or more, even more preferably 40C (equivalent to 20A) or more, and even more preferably 45C or more (equivalent to 22A) from the viewpoint of suppressing edge droop of the semiconductor during semiconductor polishing. Furthermore, when used in a polishing pad, from the viewpoint of suppressing scratches on the substrate, the instantaneous hardness measured with a durometer type A or D according to JIS K6253 is preferably 35D (equivalent to 90A) or less, more preferably 80A or less, and even more preferably 70A or less.

[0070] (Static friction coefficient of polishing pad) The static friction coefficient of the polishing pad of this embodiment is 1.2 or less, more preferably 1.0 or less, and even more preferably 0.9 or less. Methods for reducing the static friction coefficient include not only reducing the static friction coefficient of the hydrogenated block copolymer composition itself, but also improving the cell size distribution and forming grooves. When the static friction coefficient of the polishing pad is within the above range, stable dressing performance can be achieved. The static friction coefficient can be measured in accordance with JIS K7125.

[0071] (Kinematic friction coefficient of polishing pad) The static friction coefficient of the polishing pad of this embodiment is preferably 0.65 or less, more preferably 0.60 or less, and even more preferably 0.55 or less, from the viewpoint of reducing the dynamic friction coefficient of the polishing pad. Methods for reducing the dynamic friction coefficient include not only reducing the dynamic friction coefficient of the hydrogenated block copolymer composition itself, but also improving the cell size distribution and forming grooves. When the dynamic friction coefficient of the polishing pad is within the above range, the polishing pad does not wear out even when polishing semiconductors or the like for a long period of time, and a high polishing rate can be maintained. The dynamic friction coefficient can be measured in accordance with JIS K7125.

[0072] The method may include a dressing step in which the front and / or back surface of the abrasive layer is subjected to a dressing treatment (grinding treatment). The method of dressing treatment (grinding treatment) is not particularly limited, and grinding can be performed by a known method. Specifically, grinding using a diamond dresser can be mentioned.

[0073] The polishing pad of this embodiment can be attached to a commercially available polishing device and used in a polishing step by a known method. The polishing pad of this embodiment can be used in a wide range of polishing processes for manufacturing semiconductor devices. The polishing pad of the present embodiment can be used to polish objects that require flatness, such as silicon wafers, glass, magnetic disks, sapphire, and semiconductors such as SiC and GaN. Among these, the method for manufacturing a polished object of the present embodiment can be suitably used as a method for manufacturing semiconductors such as SiC and GaN. The polishing slurry may contain chemical components such as water, hydrogen peroxide, and oxidizing agents such as potassium permanganate, additives, and abrasive grains (polishing particles; e.g., SiC, SiO2, Al2O3, CeO2), depending on the object to be polished and the polishing conditions. There are no particular limitations on the double-sided tape used to fasten the polishing pad and the polishing machine, and any double-sided tape known in the art can be selected and used. [Example]

[0074] Hereinafter, the present embodiment will be described in detail with reference to specific examples and comparative examples, but the present embodiment is not limited in any way by the following examples and comparative examples. The methods for measuring and evaluating physical properties used in the examples and comparative examples are shown below.

[0075] The hydrogenated block copolymers used in the foams of the Examples and Comparative Examples were subjected to structural identification and physical property measurements as described below.

[0076] [Method for measuring the structure of hydrogenated block copolymer] ((1) Content of total vinyl aromatic monomer units (styrene) in hydrogenated block copolymer (A)) The hydrogenated block copolymer was used to measure the total vinyl aromatic monomer unit (styrene) content using an ultraviolet spectrophotometer (Shimadzu Corporation, UV-2450).

[0077] ((2) Hydrogenation rate of double bonds of conjugated diene monomer units of hydrogenated block copolymer (a)) The hydrogenation rate of the double bonds of the conjugated diene monomer units was measured using the hydrogenated block copolymer with a nuclear magnetic resonance spectrometer (ECS400, manufactured by JEOL RESONANCE).

[0078] ((3) Content of polymer block (a) in hydrogenated block copolymer (a)) The content of polymer block (a) mainly composed of vinyl aromatic monomer units was measured using a hydrogenated block copolymer by nuclear magnetic resonance (NMR) (the method described in Y. Tanaka, et al., RUBBER CHEMISTRY and TECHNOLOGY 54, 685 (1981) (hereinafter referred to as the "NMR method").

[0079] ((4) Content of hydrogenated copolymer block (b) in hydrogenated block copolymer (a)) Calculation was performed using the formula: 100 - (content of hydrogenated copolymer block (a) in hydrogenated block copolymer (a)).

[0080] ((5) Amount of vinyl bonds in hydrogenated block copolymer (a)) The amount of vinyl bonds in hydrogenated block copolymers was measured by nuclear magnetic resonance (NMR). The amount of vinyl bonds in the conjugated diene monomer units in the hydrogenated block copolymer was determined as the ratio of the total peak area of ​​1,2-bonds and 3,4-bonds to the total area of ​​all peaks related to the conjugated diene monomer units (the proportions of 1,2-bonds, 3,4-bonds, and 1,4-bonds) obtained by NMR measurement.

[0081] ((6) Content of vinyl aromatic monomer units in hydrogenated copolymer block (b) constituting hydrogenated block copolymer (a)) The vinyl aromatic monomer unit content in hydrogenated copolymer block (b) relative to the entire polymer was calculated from the difference between the total vinyl aromatic monomer unit content in hydrogenated block copolymer (a) measured in (1) above and the content of polymer block (a) mainly composed of vinyl aromatic monomer units in hydrogenated block copolymer (a) measured in (3) above, and the vinyl aromatic monomer unit content in hydrogenated copolymer block (b) was calculated from the ratio to the content of hydrogenated copolymer block (b) in hydrogenated block copolymer (a) measured in (4) above.

[0082] [Method for measuring physical properties of hydrogenated block copolymer] ((1) Hardness) According to JIS K6253, values ​​at 0 seconds and 15 seconds were measured using a durometer type A and a durometer type D, respectively. After lowering the probe of the hardness tester onto the sample for measurement, the hardness values ​​were measured at 0 seconds and 15 seconds. In the table below, the hardness is indicated as hardness (JIS-A, 0 seconds), hardness (JIS-A, 15 seconds), hardness (JIS-D, 0 seconds), and hardness (JIS-D, 15 seconds). When the hardness value is less than 20 using Durometer Type D, the value using Durometer Type A is used, and when the hardness value is more than 90 using Durometer Type A, the value using Durometer Type D is used. As a guideline, a hardness of 94 on a durometer type A corresponds to a hardness of 45 on a durometer type D.

[0083] ((2) Melt flow rate (MFR, unit: g / 10 min) The MFR was measured in accordance with JIS K7210 under conditions of a temperature of 230°C and a load of 2.16 kg.

[0084] ((3) Coefficient of static friction) In accordance with JIS K7125, a 2mm press was made using hydrogenated block copolymers (A)-1 to -4 as raw materials, and a brass specimen with a contact surface dimension of 63mm x 63mm and a load of 200g was placed on it using the method described below. The test was started within 3 seconds, and the brass specimen was moved parallel to the test piece at a test speed of 100mm / min. The static friction coefficient was calculated by dividing the test force at which the test piece began to move by the contact area.

[0085] ((4) Coefficient of kinetic friction) In accordance with JIS K7125, the test was conducted in the same manner as in (3), and the coefficient of dynamic friction was obtained by dividing the average test force when the test piece started to move and the test force stabilized by the contact area.

[0086] [Method for measuring physical properties of polishing pad] ((1) Average bubble diameter) The volume of each bubble in the polishing pad was measured using an X-ray CT scanner (e.g., TDM1000H-I manufactured by Yamato Scientific Co., Ltd.), and the diameter of each bubble was determined as the diameter of a sphere with the same volume. The arithmetic mean value of the bubble diameters calculated from the volume of each bubble [= sum of "each bubble diameter" / (number of bubbles)] was determined as the average bubble diameter.

[0087] ((2) Bubble size distribution) An X-ray CT scanning device (e.g., TDM1000H-I manufactured by Yamato Scientific Co., Ltd.) was used to obtain a volumetric bubble diameter distribution curve for bubbles in the polishing pad. When the difference between the bubble diameter at a cumulative volume frequency of 80% and the bubble diameter at a cumulative volume frequency of 20% (bubble diameter at a cumulative volume frequency of 80% - bubble diameter at a cumulative volume frequency of 20%) was 50 μm or more, the bubble diameter distribution was determined to be wide, and when it was 50 μm or less, the bubble diameter distribution was determined to be narrow.

[0088] ((3) Coefficient of static friction) The static friction coefficient of the prepared polishing pad was measured in the same manner as for the hydrogenated block copolymer.

[0089] ((4) Coefficient of kinetic friction) The dynamic friction coefficient of the prepared polishing pad was measured in the same manner as for the hydrogenated block copolymer.

[0090] ((5) Dressing properties) Toyochem double-sided tape DF8391S was attached to the prepared polishing pad, and the polishing pad was then fixed to the platen of a 15-inch single-sided polisher (Hi-Technos), and dressing was performed using metal bond SD#270 at a platen rotation speed of 60 rpm. Those that could not be dressed because of the high friction force were rated as dressing ability B, and those that could be dressed were rated as dressing ability A.

[0091] ((6) Polishing rate) After the polishing pad was dressed for 1 hour by the method (5), a polishing test was carried out under the conditions shown in Table 1 below. The 4-inch SiC substrates used for polishing were each processed in advance to standardize the surface roughness of the substrates before use.

[0092] [Table 1]

[0093] (7) Polishing rate stability (durability) The polishing rate V0 immediately after polishing started was compared with the polishing rate V1 10 minutes after polishing started, and (V1 / V0) x 100 was evaluated as A if it was 70 or more, B if it was 50 to 70, C if it was 30 to 50, and D if it was 30 or less.

[0094] (Production of hydrogenated block copolymer (a)) <Preparation of hydrogenation catalyst> In the examples and comparative examples described later, the hydrogenation catalysts used in producing hydrogenated block copolymers were prepared by the following method. A reaction vessel equipped with a stirrer was purged with nitrogen, and 1 liter of dried and purified cyclohexane was placed in the vessel. Next, 100 mmol of bis(η5-cyclopentadienyl)titanium dichloride was added. An n-hexane solution containing 200 mmol of trimethylaluminum was added to the mixture while thoroughly stirring, and the mixture was allowed to react at room temperature for about 3 days, thereby obtaining a hydrogenation catalyst.

[0095] <Production Example 1: Hydrogenated Block Copolymer (A)-1> Batch polymerization was carried out using a tank reactor (internal volume: 10 L) equipped with a stirrer and a jacket. First, a cyclohexane solution containing 15 parts by mass of styrene (concentration: 20% by mass) was added. Next, 0.107 parts by mass of n-butyllithium per 100 parts by mass of the total monomers and 0.9 moles of N,N,N',N'-tetramethylethylenediamine (hereinafter referred to as "TMEDA") per mole of n-butyllithium were added, and polymerization was carried out at 65°C for 1 hour. Next, a cyclohexane solution (concentration 20% by mass) containing 29 parts by mass of butadiene and 41 parts by mass of styrene was added, and polymerization was carried out for 2 hours at 80° C. Finally, a cyclohexane solution (concentration 20% by mass) containing 15 parts by mass of styrene was added, and polymerization was carried out for 1 hour at 65° C. Thereafter, methanol was added to terminate the polymerization reaction. The block copolymer obtained as described above had a styrene content of 71% by mass, a polystyrene block content of 30% by mass, a vinyl bond amount of 46% by mass, and a weight average molecular weight of 60,000. Furthermore, the hydrogenation catalyst prepared as described above was added to the resulting block copolymer in an amount of 100 ppm (Ti basis) per 100 parts by mass of the block copolymer, and a hydrogenation reaction was carried out at a hydrogen pressure of 0.7 MPa and a temperature of 65°C. Next, 0.3 parts by mass of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer to 100 parts by mass of the block copolymer to obtain hydrogenated block copolymer (a)-1. The hydrogenation rate of the obtained hydrogenated block copolymer (a)-1 was 98%. Other physical properties are shown in Table 2.

[0096] <Production Examples 2 to 7: Hydrogenated Block Copolymers (A)-2 to (A)-7> In the method for producing the hydrogenated block copolymer (a)-1, the polymerization method and hydrogenation conditions were adjusted to produce (a)-2 to (a)-7. The physical properties of these copolymers are shown in Tables 2 and 3 below.

[0097] [Preparation of press-molded sheet] The hydrogenated block copolymers (a)-1 to (a)-7 prepared as described above were each rolled out at 160°C using a 4-inch roll, and then subjected to a hydraulic press at 200°C and 100 kg / cm 2 The mixture was press-molded into a press-molded sheet having dimensions of 130 mm x 220 mm and a thickness of 2 mm.

[0098] [Production of hydrogenated block copolymer composition] Hydrogenated block copolymer compositions were produced using the above-mentioned hydrogenated block copolymers (a)-1 to (a)-7 and the following component (b).

[0099] (Olefin resin (b)) <Component (b)-1> Olefin resin: Low-density polyethylene resin, L2340 (manufactured by Asahi Kasei Corporation)

[0100] [Raw materials used in Example 2, production of hydrogenated block copolymer composition] The pelletized hydrogenated block copolymer (a)-1 and the olefin resin (b) were blended in the ratios (parts by mass) shown in Table 3 below, kneaded in a twin-screw extruder (TEX-30), and pelletized to obtain a hydrogenated block copolymer composition. The extrusion conditions were a cylinder temperature of 230°C and a screw rotation speed of 300 rpm.

[0101] [Manufacture of polishing pads] As shown in Examples 1 to 9, using hydrogenated block copolymers (A)-1 to (A)-7, foams with an expansion ratio of 2.7 times were produced using a known method with the formulation shown in Table 3, and cut into cylindrical foams with an inner diameter of 400 mm and a thickness of 2 mm to form polishing pads. As shown in Comparative Examples 1 and 2, a foam with an expansion ratio of 2.7 times was produced using hydrogenated block copolymer (a)-2 or olefin resin (b) according to the formulation shown in Table 3 using a known method, and cut into a cylindrical foam with an inner diameter of 400 mm and a thickness of 2 mm to form a polishing pad.

[0102] Table 2 below shows the physical properties of the hydrogenated block copolymer (a), and Table 3 shows the evaluation results of the physical properties and characteristics of the polishing pad.

[0103] [Table 2]

[0104] [Table 3]

Claims

1. A polishing pad containing 5% by mass or more of a hydrogenated block copolymer (a) that satisfies the following conditions (1) and (2), and having a static friction coefficient of 1.2 or less as measured in accordance with JIS K7125: <Condition (1)>: The hydrogenated block copolymer (a) is a hydrogenated product of a block copolymer containing vinyl aromatic monomer units and conjugated diene monomer units. <Condition (2)>: The hydrogenated block copolymer (a) contains at least one polymer block (a) mainly composed of vinyl aromatic monomer units, The content of the polymer block (a) mainly composed of vinyl aromatic monomer units in the hydrogenated block copolymer (a) is 10% by mass or more.

2. The hydrogenated block copolymer (a) contains at least one hydrogenated copolymer block (b) composed of a vinyl aromatic monomer unit and a conjugated diene monomer unit, 2. The polishing pad according to claim 1, wherein the content of the vinyl aromatic monomer unit in the hydrogenated copolymer block (b) is 5% by mass or more and 79% by mass or less.

3. 3. The polishing pad according to claim 2, wherein the content of the vinyl aromatic monomer unit in the hydrogenated copolymer block (b) is 45% by mass or more and 79% by mass or less.

4. 2. The polishing pad according to claim 1, comprising 40% by mass or more of the hydrogenated block copolymer (i).

5. 2. The polishing pad according to claim 1, comprising 70% by mass or more of the hydrogenated block copolymer (i).

6. 2. The polishing pad according to claim 1, wherein the dynamic friction coefficient measured in accordance with JIS K7125 is 0.6 or less.

7. 2. The polishing pad according to claim 1, wherein the content of the polymer block (a) mainly composed of vinyl aromatic monomer units in the hydrogenated block copolymer (i) is 15% by mass or more and 40% by mass or less.

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