Polishing pad and method for manufacturing the same

Abstract

To provide an abrasive pad that allows significant reduction in level differences and defects, and exhibits high wear resistance.SOLUTION: An abrasive pad has an abrasive layer composed of an isocyanate-terminated prepolymer and a hardener-derived polyurethane resin foam. The isocyanate-terminated prepolymer has a polyisocyanate compound-derived constitutional unit and a high-molecular-weight-polyol-derived constitutional unit. The high-molecular-weight-polyol-derived constitutional unit has at least a polypropylene glycol constitutional unit and a polyester diol constitutional unit. The polypropylene glycol constitutional unit is less than 60 wt.% relative to the high-molecular-weight-polyol-derived constitutional unit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a polishing pad. More particularly, the present invention relates to a polishing pad that can be suitably used for polishing optical materials, semiconductor wafers, semiconductor devices, hard disk substrates, and the like. [Background technology]

[0002] Chemical mechanical polishing (CMP) is a commonly used polishing method for planarizing the surfaces of optical materials, semiconductor wafers, semiconductor devices, and hard disk substrates.

[0003] The CMP method will be described with reference to FIG. 1. As shown in FIG. 1, a polishing apparatus 1 for performing the CMP method is equipped with a polishing pad 3. The polishing pad 3 contacts an object 8 to be polished, which is held on a holding platen 16, and includes a polishing layer 4, which is the layer that performs the polishing, and a cushion layer 6 that supports the polishing layer 4. The polishing pad 3 is rotated while pressed against the object 8 to polish the object 8. During this process, a slurry 9 is supplied between the polishing pad 3 and the object 8 to be polished. The slurry 9 is a mixture (dispersion liquid) of water, various chemical components, and hard, fine abrasive particles. As the chemical components and abrasive particles flow, the relative movement with the object 8 to be polished increases the polishing effect. The slurry 9 is supplied to and discharged from the polishing surface through grooves or holes.

[0004] In polishing semiconductor devices, a polishing pad is typically used whose polishing layer 4 is made of a hard polyurethane material obtained by reacting a prepolymer containing an isocyanate component (such as toluene diisocyanate (TDI)) and a high molecular weight polyol (such as polyoxytetramethylene glycol (PTMG)) with a diamine curing agent (such as 4,4'-methylenebis(2-chloroaniline) (MOCA)). The high molecular weight polyol contained in the prepolymer forms urethane soft segments, and PTMG, which is easy to handle and exhibits moderate rubber elasticity, has traditionally been used as the high molecular weight polyol.

[0005] However, in recent years, with the miniaturization of wiring in semiconductor devices, conventional polishing pads have sometimes been found to have insufficient step-eliminating and defect-removing performance, and the use of high-molecular-weight polyols other than PTMG has been investigated.

[0006] Patent Document 1, which examines the above-mentioned problems, discloses a polishing pad that has high step-eliminating performance and produces fewer scratches by using polypropylene glycol (PPG) as the high-molecular-weight polyol of the prepolymer.

[0007] Furthermore, Patent Document 2 discloses a polishing pad in which the defect rate is reduced by using a mixture of PPG and PTMG as a high molecular weight polyol of a prepolymer. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2020-157415 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-040737 Summary of the Invention [Problem to be solved by the invention]

[0009] However, the polishing pad described in Patent Document 1 has a problem in that the abrasion resistance of the polishing layer is poor and the life of the polishing pad is short. Also, the polishing pad described in Patent Document 2 has a problem in that the polishing pad contains PTMG and therefore has insufficient step elimination performance and defect removal performance.

[0010] The present invention has been made in view of the above problems, and has as its object to provide a polishing pad that is excellent in step-eliminating performance and defect removal performance, and also has excellent wear resistance. [Means for solving the problem]

[0011] As a result of extensive research, the inventors have discovered that by using a specific polyol as the material for the polishing layer of a polishing pad, a polishing pad can be obtained that has excellent step-eliminating performance and defect removal performance, as well as excellent wear resistance, and have arrived at the present invention. [1] A polishing pad having a polishing layer made of a polyurethane resin foam derived from an isocyanate-terminated prepolymer and a curing agent, the isocyanate-terminated prepolymer contains a polyisocyanate compound-derived constitutional unit and a high-molecular-weight polyol-derived constitutional unit; the high-molecular-weight polyol-derived structural units are composed of at least polypropylene glycol structural units and polyester diol structural units, A polishing pad, wherein the polypropylene glycol constituent units account for less than 60% by weight of the constituent units derived from the high molecular weight polyol. [2] The polishing pad according to [1], wherein the polypropylene glycol structural units account for 30 to 50% by weight of the structural units derived from the high-molecular-weight polyol. [3] The polishing pad according to [1] or [2], wherein the polyester diol constitutional unit is derived from a polyester diol having a number average molecular weight of 600 to 2,500. [4] A method for manufacturing a polishing pad having a polishing layer made of polyurethane resin foam, comprising: a step of reacting a polyisocyanate compound with a high molecular weight polyol containing at least polypropylene glycol and a polyester diol to obtain an isocyanate-terminated prepolymer; a step of reacting the isocyanate-terminated prepolymer with a curing agent to obtain the polyurethane resin foam; and forming the polyurethane resin foam into a polishing layer shape, The production method, wherein the polypropylene glycol accounts for less than 60% by weight of the total amount of the high-molecular-weight polyol. [Effects of the Invention]

[0012] According to the polishing pad of the present invention, by using a high molecular weight polyol containing polypropylene glycol and polyester diol as the material for the polishing layer, a polishing pad can be obtained that has excellent step-eliminating performance and defect performance, as well as excellent wear resistance. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a perspective view of a polishing apparatus 1. As shown in FIG. [Figure 2] FIG. 2 is a cross-sectional view of a polishing pad. [Figure 3] FIG. 3 is a diagram showing a schematic diagram of the state of the step in the step polishing amount test. [Figure 4] FIG. 4 is a graph showing the change in the amount of wear (thickness) of the polishing pads of the examples and comparative examples. [Figure 5] FIG. 5 shows the test results of the step-eliminating performance of the example and the comparative example. [Figure 6] FIG. 6 shows the results of polishing tests on defect performance for the examples and comparative examples. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, the embodiments of the invention will be described, but the present invention is not limited to the embodiments of the invention.

[0015] <<Polishing pads>> The structure of the polishing pad 3 will be described with reference to Fig. 2(a). As shown in Fig. 2(a), the polishing pad 3 includes a polishing layer 4 and a cushion layer 6. The shape of the polishing pad 3 is preferably disc-shaped, but is not particularly limited thereto. The size (diameter) can also be determined appropriately depending on the size of the polishing apparatus 1 equipped with the polishing pad 3, and can be, for example, about 10 cm to 2 m in diameter. In the polishing pad 3 of the present invention, the polishing layer 4 is preferably bonded to the cushion layer 6 via an adhesive layer 7, as shown in FIG. 2(a). The polishing pad 3 is attached to the polishing platen 10 of the polishing apparatus 1 by double-sided tape or the like arranged on the cushion layer 6. The polishing pad 3 is rotated by the polishing apparatus 1 while pressing against the object 8 to be polished, thereby polishing the object 8 (see FIG. 1).

[0016] <Polishing layer> (composition) The polishing pad 3 includes a polishing layer 4 that is a layer for polishing an object to be polished 8. The material that constitutes the polishing layer 4 is a specific polyurethane resin. The size (diameter) of the polishing layer 4 is the same as that of the polishing pad 3, and can be about 10 cm to 2 mm in diameter, and the thickness of the polishing layer 4 can usually be about 1 to 5 mm. The polishing layer 4 is rotated together with the polishing table 10 of the polishing device 1, and while a slurry 9 is poured onto it, the chemical components and abrasive grains contained in the slurry 9 are moved relative to the object 8 to be polished, thereby polishing the object 8 to be polished. Hollow microspheres 4A may be dispersed in the polishing layer 4. When hollow microspheres 4A are dispersed, as the polishing layer 4 is worn, the hollow microspheres 4A are exposed to the polishing surface, generating minute voids on the polishing surface, which retain the slurry and allow polishing of the workpiece 8 to proceed more rapidly.

[0017] The polishing layer 4 is formed by casting a mixture of an isocyanate-terminated prepolymer, a curing agent (chain extender), and, if necessary, hollow microspheres 4A, and slicing the cured foam. In other words, the polishing layer 4 is dry-molded.

[0018] (Hollow microspheres) The hollow microspheres 4A that may be contained in the polishing layer 4 of the polishing pad of the present invention can be confirmed as hollow bodies on the polishing surface or cross section of the polishing layer 4, and the hollow bodies usually have an opening diameter (diameter of the hollow microspheres 4A) of 2 to 200 μm. The shape of the hollow microspheres 4A can be spherical, ellipsoidal, or similar shapes.

[0019] The hollow microspheres 4A may be commercially available balloons, and may be expanded or unexpanded. Unexpanded microspheres are heat-expandable microspheres that can be expanded by heating. In the present invention, they may be used as needed.

[0020] (Groove machining) The surface of the polishing layer 4 of the present invention facing the polished object 8 may be grooved. The grooves are not particularly limited and may be either slurry discharge grooves that communicate with the periphery of the polishing layer 4 or slurry retention grooves that do not communicate with the periphery of the polishing layer 4, or both slurry discharge grooves and slurry retention grooves. Examples of the slurry discharge grooves include lattice grooves and radial grooves, while examples of the slurry retention grooves include concentric grooves and perforations (through holes), and these can also be combined.

[0021] <Cushion layer> (composition) The polishing pad 3 of the present invention has a cushion layer 6. The cushion layer 6 desirably allows the polishing layer 4 to contact the workpiece 8 more uniformly. The cushion layer 6 may be made of any material, such as an impregnated nonwoven fabric impregnated with a resin, a flexible material such as a synthetic resin or rubber, or a foam with a cellular structure. Examples of the material include resins such as polyurethane, polyethylene, polybutadiene, and silicone, and rubbers such as natural rubber, nitrile rubber, and polyurethane rubber. From the viewpoint of adjusting the density and compressive modulus, an impregnated nonwoven fabric is preferred, and polyurethane is preferably used as the resin material impregnated into the nonwoven fabric.

[0022] The cushion layer 6 is preferably made of polyurethane resin having sponge-like fine bubbles.

[0023] The compressive elastic modulus, density, and bubbles of the cushion layer 6 in the polishing pad 3 of the present invention are not particularly limited, and a cushion layer 6 having known characteristic values ​​can be used.

[0024] <Adhesive layer> The adhesive layer 7 is a layer for adhering the cushion layer 6 and the polishing layer 4, and is usually made of a double-sided tape or an adhesive. Any double-sided tape or adhesive known in the art (e.g., an adhesive sheet) can be used. The polishing layer 4 and the cushion layer 6 are bonded together by an adhesive layer 7. The adhesive layer 7 can be formed of at least one adhesive selected from, for example, acrylic, epoxy, and urethane adhesives. For example, an acrylic adhesive is used, and the thickness can be set to 0.1 mm.

[0025] The polishing pad of the present invention has excellent step-eliminating and defect-removing properties, and also has excellent wear resistance. Here, step-eliminating performance refers to the ability to reduce steps (convex and concave) on patterned wafers during polishing. Figure 3 shows a schematic diagram of the experiment to measure step-eliminating performance. When a 3500 Å step is present on the workpiece, the results show the elimination of the step when a polishing pad with high step-eliminating performance (dotted line) is used, compared with a polishing pad with relatively poor step-eliminating performance (solid line). While there is no difference at the time of (a) in Figure 3, as polishing progresses and the removal amount reaches 2000 Å, the polishing pad with good step-eliminating performance (dotted line) shows less step-eliminating performance than the polishing pad with relatively poor step-eliminating performance (solid line) ((b)), and the polishing pad with high step-eliminating performance eliminates the step relatively quickly ((c)). It can be said that the polishing pad indicated by the dotted line has relatively better step-eliminating performance than the polishing pad indicated by the solid line.

[0026] Furthermore, "defect" is a general term that includes imperfections such as "particles," which refer to fine particles remaining on the surface of the object being polished, "pad debris," which refers to scraps of the polishing layer adhering to the surface of the object being polished, and "scratch," which refers to scratches on the surface of the object being polished, and defect performance refers to the ability to reduce these "defects."

[0027] The abrasion resistance refers to the resistance to abrasion.

[0028] <<Polishing pad manufacturing method>> A method for producing the polishing pad 3 of the present invention will be described.

[0029] <Abrasive layer material> In the present invention, the polishing layer is mainly made of a polyurethane resin, and a specific example of the main component is a polyurethane resin foam material obtained by reacting an isocyanate-terminated prepolymer with a curing agent.

[0030] Examples of methods for producing the polishing layer 4 using an isocyanate-terminated prepolymer and a curing agent include a production method including: a preparation step of preparing the isocyanate-terminated prepolymer; a material preparation step of preparing the isocyanate-terminated prepolymer, a curing agent, optional additives, and optional hollow microspheres; a mixing step of mixing the isocyanate-terminated prepolymer, the curing agent, optional additives, and optional hollow microspheres to obtain a mixture for molding a molded body; and a curing step of molding the mixture for molding a molded body into a polishing layer.

[0031] The preparation process will be explained below, divided into the material preparation process, the mixing process, and the molding process.

[0032] <Preparation process> The isocyanate-terminated prepolymer used in the present invention can be obtained by reacting a polyisocyanate compound with a high-molecular-weight polyol containing at least polypropylene glycol and polyester diol, and contains an isocyanate group at the molecular end. Commercially available isocyanate-terminated prepolymers can be used, but typically, a prepolymer obtained by partially reacting a polyisocyanate compound with a polyol compound is used. The reaction is not particularly limited, and an addition polymerization reaction can be carried out using methods and conditions known in the production of polyurethane resins. For example, the isocyanate-terminated prepolymer can be produced by adding a polyisocyanate compound heated to 50°C to a polyol compound heated to 40°C while stirring in a nitrogen atmosphere, then heating the mixture to 80°C after 30 minutes and continuing the reaction at 80°C for 60 minutes.

[0033] Each component will be described below.

[0034] (Polyisocyanate compounds) The isocyanate-terminated prepolymer uses a polyisocyanate compound as a raw material.

[0035] The polyisocyanate compound is not particularly limited and may be a commercially available product. In this specification, the term "polyisocyanate compound" refers to a compound having two or more isocyanate groups in the molecule. The polyisocyanate compound is not particularly limited as long as it has two or more isocyanate groups in the molecule. For example, diisocyanate compounds having two isocyanate groups in the molecule include m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-tolylene diisocyanate (2,6-TDI), 2,4-tolylene diisocyanate (2,4-TDI), naphthalene-1,4-diisocyanate, diphenylmethane-4,4'-diisocyanate (MDI), 4,4'-methylene-bis(cyclohexyl isocyanate) (hydrogenated MDI), 3,3'-dimethoxy-4,4'-biphenyl diisocyanate, 3,3'-dimethyl- Examples of the polyisocyanate compound include diphenylmethane-4,4'-diisocyanate, xylylene-1,4-diisocyanate, 4,4'-diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, cyclohexylene-1,2-diisocyanate, cyclohexylene-1,4-diisocyanate, p-phenylene diisothiocyanate, xylylene-1,4-diisothiocyanate, ethylidine diisothiocyanate, etc. These polyisocyanate compounds may be used alone, or multiple polyisocyanate compounds may be used in combination.

[0036] The polyisocyanate compound preferably contains 2,4-TDI and / or 2,6-TDI.

[0037] (High molecular weight polyols as raw materials for isocyanate-terminated prepolymers) In this specification, "polyol" refers to a compound having two or more hydroxyl groups (OH) in the molecule, and "high molecular weight" refers to a molecular weight of 500 or more. In the present invention, at least polypropylene glycol and polyester diol are used as the high molecular weight polyols used as raw materials for the isocyanate-terminated prepolymer. The polypropylene glycol used in the present invention is not particularly limited, and examples thereof include polypropylene glycols having a number average molecular weight (Mn) of 500 to 2,000, more preferably 650 to 1,000. The number average molecular weight can be measured by gel permeation chromatography (GPC). When measuring the number average molecular weight of a polyol compound from a polyurethane resin, each component can be decomposed by a conventional method such as amine decomposition, and then the molecular weight can be estimated by GPC.

[0038] In the present invention, a polyester diol is used as a high molecular weight polyol used as a raw material for the isocyanate-terminated prepolymer. In this specification, the polyester diol has two or more ester bonds and two hydroxyl (OH) groups. The polyester diol can be obtained, for example, by reacting a dicarboxylic acid compound with a diol compound. Examples of dicarboxylic acid compounds include aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decanedioic acid, and dodecanedioic acid; unsaturated bond-containing dicarboxylic acids such as maleic anhydride, maleic acid, and fumaric acid; alicyclic polycarboxylic acids such as 1,3-cyclopentanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid; and aromatic dicarboxylic acids such as orthophthalic acid, terephthalic acid, isophthalic acid, 1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, naphthalic acid, biphenyldicarboxylic acid, diphenic acid, and anhydrides thereof; and the like, which may be used alone or in combination.

[0039] Examples of diol compounds used in the synthesis of polyester diols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, and 1,6-hexanediol, and these can be used alone or in combination.

[0040] Among the above, polyester diols of adipic acid and 1,4-butanediol and polyester diols of adipic acid and diethylene glycol are preferred.

[0041] The number average molecular weight of the polyester diol is preferably 600 to 2500 from the viewpoint of exhibiting the rubber elasticity required for the polishing pad as a soft segment.

[0042] The amount of polypropylene glycol is less than 60% by weight based on the total amount of high molecular weight polyol. If it exceeds 60% by weight, the abrasion resistance will deteriorate. Preferably, the amount of polypropylene glycol is 30 to 50% by weight based on the total amount of high molecular weight polyol. The polyester diol is less than 70% by weight based on the total amount of the high molecular weight polyol. If it exceeds 70% by weight, the step-eliminating performance deteriorates. Preferably, the polyester diol is 50 to 70% by weight based on the total amount of the high molecular weight polyol. The total amount of polypropylene glycol and polyester diol is preferably 80% by weight or more based on the total amount of high molecular weight polyol, because the effect is more pronounced when it is 80% by weight or more.

[0043] In the present invention, a high molecular weight polyol other than polypropylene glycol and polyester diol may be used as the high molecular weight polyol if necessary, but it is used within a range that does not impair the effects of the present invention. For example, polyoxytetramethylene glycol is preferably 10% by weight or less, more preferably 5% by weight or less, and even more preferably 3% by weight or less, based on the total high molecular weight polyol. If it is contained in an amount exceeding 10% by weight, the step-eliminating performance and defect-reducing performance may be insufficient.

[0044] <Material preparation process> To manufacture the polishing layer 4 of the present invention, an isocyanate-terminated prepolymer, a curing agent, optional additives, and optional hollow microspheres are prepared. The isocyanate-terminated prepolymer has already been described, so the curing agent, additives, and hollow microspheres will now be described.

[0045] (hardening agent) In the method for producing the polishing layer 4 of the present invention, a curing agent (also called a chain extender) is mixed with an isocyanate-terminated prepolymer or the like in the mixing step. By adding the curing agent, the main chain end of the urethane bond-containing polyisocyanate compound bonds with the curing agent to form a polymer chain and harden in the subsequent molding step. Examples of the curing agent include ethylenediamine, propylenediamine, hexamethylenediamine, isophoronediamine, dicyclohexylmethane-4,4'-diamine, 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA), 4-methyl-2,6-bis(methylthio)-1,3-benzenediamine, 2-methyl-4,6-bis(methylthio)-1,3-benzenediamine, 2,2-bis(3-amino-4-hydroxyphenyl)propane, 2,2-bis[3-(isopropylamino)-4- polyamine compounds such as 2,2-bis[3-(1-methylpropylamino)-4-hydroxyphenyl]propane, 2,2-bis[3-(1-methylpentylamino)-4-hydroxyphenyl]propane, 2,2-bis(3,5-diamino-4-hydroxyphenyl)propane, 2,6-diamino-4-methylphenol, trimethylethylenebis-4-aminobenzoate, and polytetramethyleneoxide-di-p-aminobenzoate; ethylene glycol, propane, Pyrene glycol, diethylene glycol, trimethylene glycol, tetraethylene glycol, triethylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,2-butanediol, 3-methyl-1,2-butanediol, 1,2-pentanediol, 1,4-pentanediol, 2,4-pentanediol, 2,3-dimethyltrimethylene glycol, tetramethylene glycol, 3-methyl-4,3-pentanediol, 3- Examples of polyhydric alcohol compounds include methyl-4,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,6-hexanediol, 1,5-hexanediol, 1,4-hexanediol, 2,5-hexanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, glycerin, trimethylolpropane, trimethylolethane, trimethylolmethane, poly(oxytetramethylene) glycol, polyethylene glycol, and polypropylene glycol.Furthermore, the polyvalent amine compound may have a hydroxyl group, and examples of such amine compounds include 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, di-2-hydroxypropylethylenediamine, etc. As the polyvalent amine compound, a diamine compound is preferred, and it is more preferred to use, for example, 3,3'-dichloro-4,4'-diaminodiphenylmethane (methylenebis-o-chloroaniline) (hereinafter abbreviated as MOCA).

[0046] (additives) Additives such as an oxidizing agent may be added as needed to the material of the polishing layer 4. In the present invention, there are no particular limitations on the additives as long as they do not impair the effects of the present invention.

[0047] (Hollow microspheres) The polishing layer 4 optionally contains hollow microspheres 4A, each having an outer shell and a hollow interior. As described above, commercially available materials can be used for the hollow microspheres 4A. Alternatively, microspheres obtained by conventional synthesis can be used. The material for the outer shell of the hollow microspheres 4A is not particularly limited, but examples include polyvinyl alcohol, polyvinylpyrrolidone, poly(meth)acrylic acid, polyacrylamide, polyethylene glycol, polyhydroxyether acrylate, maleic acid copolymer, polyethylene oxide, polyurethane, poly(meth)acrylonitrile, polyvinylidene chloride, polyvinyl chloride, and organic silicone resins, as well as copolymers of two or more of the monomers constituting these resins. Commercially available hollow microspheres include, but are not limited to, the Expancel series (trade names, manufactured by Akzo Nobel) and Matsumoto Microsphere (trade names, manufactured by Matsumoto Yushi Co., Ltd.).

[0048] The material for the hollow microspheres 4A is added in an amount of preferably 0.1 to 10 parts by mass, more preferably 1 to 5 parts by mass, and even more preferably 1 to 3 parts by mass, per 100 parts by mass of the isocyanate-terminated prepolymer.

[0049] In addition to the above components, conventional blowing agents may be used in combination with the hollow microspheres 4A within the range that does not impair the effects of the present invention, and a gas that is non-reactive with the above components may be blown into the hollow microspheres 4A during the mixing step described below. Examples of the blowing agent include water and blowing agents whose main component is a hydrocarbon having 5 or 6 carbon atoms. Examples of the hydrocarbon include linear hydrocarbons such as n-pentane and n-hexane, and alicyclic hydrocarbons such as cyclopentane and cyclohexane.

[0050] The prepolymer may be produced, for example, by mixing and reacting a polyisocyanate compound, polypropylene glycol, and polyester diol, or by mixing a mixture 1 of a polyisocyanate compound and polypropylene glycol with a mixture 2 of a polyisocyanate compound and polyester diol, and then reacting them.

[0051] <Mixing process> In the mixing step, the isocyanate-terminated prepolymer obtained in the preparation step, the curing agent, optional additives, and optional hollow microspheres are fed into a mixer and stirred and mixed. The mixing step is carried out at a temperature that ensures the fluidity of each of the above components. However, care must be taken not to overheat the hollow microspheres, as they will expand and lose their desired aperture distribution.

[0052] <Forming process> In the molding process, the mixture for molding prepared in the mixing process is poured into a rod-shaped mold preheated to 30 to 100°C for primary curing, and then heated at about 100 to 150°C for about 10 minutes to 5 hours for secondary curing to form a cured polyurethane resin (polyurethane resin molded product). At this time, the isocyanate-terminated prepolymer and the curing agent react to form a polyurethane resin foam, thereby curing the mixture. If the viscosity of the isocyanate-terminated prepolymer is too high, its fluidity will be poor, making it difficult to achieve uniform mixing. Increasing the temperature to lower the viscosity shortens the pot life and, conversely, causes uneven mixing, resulting in variations in the size of the hollow microspheres contained in the resulting foam. In particular, if the reaction temperature is too high, unexpanded hollow microspheres will expand more than necessary, making it difficult to obtain the desired pore size. Conversely, if the viscosity is too low, air bubbles will migrate in the mixture, making it difficult to obtain a foam with uniformly dispersed hollow microspheres. For this reason, it is preferable to set the viscosity of the isocyanate-terminated prepolymer in the range of 500 to 4000 mPa·s at a temperature of 50 to 80°C. This can be achieved, for example, by changing the molecular weight (degree of polymerization) of the isocyanate-terminated prepolymer. The isocyanate-terminated prepolymer is heated to approximately 50 to 80°C to become flowable.

[0053] In the molding process, the mixture is reacted in a mold as needed to form a foam. At this time, the isocyanate-terminated prepolymer is crosslinked and hardened by the reaction between the isocyanate-terminated prepolymer and the curing agent.

[0054] After obtaining the molded body, it is sliced ​​into sheets to form multiple polishing layers 4. A general slicing machine can be used for slicing. During slicing, the lower layer of the polishing layer 4 is held, and the polishing layer 4 is sliced ​​to a predetermined thickness starting from the upper layer. The slice thickness is set, for example, in the range of 1.3 to 2.5 mm. For a foam molded in a 50 mm thick mold, for example, approximately 10 mm of the upper and lower layers of the foam are not used due to scratches, etc., and 10 to 25 polishing layers 4 are formed from approximately 30 mm of the center. A foam with hollow microspheres 4A formed approximately uniformly inside is obtained in the hardening and molding step.

[0055] If necessary, grooves may be formed on the polishing surface of the resulting polishing layer 4. In the present invention, the method of forming grooves and the shape thereof are not particularly limited.

[0056] After that, a double-sided tape is attached to the surface of the polishing layer 4 opposite to the polishing surface of the polishing layer 4. There are no particular restrictions on the double-sided tape, and any double-sided tape known in the art can be selected and used.

[0057] <Method of manufacturing cushion layer 6> The cushion layer 6 is preferably made of an impregnated nonwoven fabric impregnated with a resin. Resins to be impregnated into the nonwoven fabric include polyurethanes such as polyurethane and polyurethane polyurea, acrylics such as polyacrylate and polyacrylonitrile, vinyls such as polyvinyl chloride, polyvinyl acetate and polyvinylidene fluoride, polysulfones such as polysulfone and polyethersulfone, acylated celluloses such as acetylated cellulose and butyrylated cellulose, polyamides, and polystyrenes. The density of the nonwoven fabric before impregnation with the resin (web state) is preferably 0.3 g / cm. 3 or less, more preferably 0.1 to 0.2 g / cm 3 The density of the nonwoven fabric after resin impregnation is preferably 0.7 g / cm. 3 or less, more preferably 0.25 to 0.5 g / cm 3When the density of the nonwoven fabric before and after resin impregnation is equal to or less than the upper limit, processing accuracy is improved. When the density of the nonwoven fabric before and after resin impregnation is equal to or greater than the lower limit, penetration of the polishing slurry into the base layer can be reduced. The adhesion rate of the resin to the nonwoven fabric is expressed as the weight of the adhered resin relative to the weight of the nonwoven fabric, and is preferably 50% by weight or more, and more preferably 75 to 200% by weight. When the adhesion rate of the resin to the nonwoven fabric is equal to or less than the upper limit, the desired cushioning properties can be achieved.

[0058] <Joining process> In the bonding step, the formed polishing layer 4 and cushion layer 6 are bonded together (bonded) with an adhesive layer 7. For example, an acrylic adhesive is used for the adhesive layer 7, and the adhesive layer 7 is formed to a thickness of 0.1 mm. That is, the acrylic adhesive is applied to a substantially uniform thickness on the surface of the polishing layer 4 opposite the polishing surface P. The surface of the polishing layer 4 opposite the polishing surface P and the surface of the cushion layer 6 are pressed together via the applied adhesive, and the polishing layer 4 and cushion layer 6 are bonded together with the adhesive layer 7. Then, after cutting into a desired shape such as a circle, an inspection is performed to check for the absence of dirt or foreign matter, and the polishing pad 3 is completed. [Example]

[0059] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0060] In each example and comparative example, unless otherwise specified, "parts" means "parts by mass."

[0061] The NCO equivalent is a numerical value showing the molecular weight of the prepolymer (PP) per NCO group, which is calculated by the formula "(mass (parts) of the polyisocyanate compound + mass (parts) of the polyol compound) / [(number of functional groups per molecule of the polyisocyanate compound × mass (parts) of the polyisocyanate compound / molecular weight of the polyisocyanate compound) - (number of functional groups per molecule of the polyol compound × mass (parts) of the polyol compound / molecular weight of the polyol compound)]".

[0062] (Production of abrasive layer) A mixed solution was obtained by adding 100 parts of an isocyanate-terminated urethane prepolymer with an NCO equivalent of 520, prepared by reacting 2,4-tolylene diisocyanate (TDI) with the high molecular weight polyol shown in Table 1, to 3 parts of pre-expanded hollow microspheres, the shell of which is made of acrylonitrile-vinylidene chloride copolymer and containing isobutane gas. The resulting mixed solution was then placed in a first liquid tank and kept warm. Next, 23.1 parts of MOCA was placed in a second liquid tank as a curing agent, separately from the first liquid, and kept warm in the second liquid tank. The liquids from the first and second liquid tanks were each poured into a mixer equipped with two injection ports so that the R value, which represents the equivalent ratio of amino and hydroxyl groups in the curing agent to the terminal isocyanate groups in the prepolymer, was 0.90. The two injected liquids were mixed and stirred while being injected into a mold of a molding machine preheated to 80°C, then the mold was clamped and heated for 30 minutes for primary curing. The primarily cured molded product was demolded and then subjected to secondary curing in an oven at 120°C for 4 hours to obtain a urethane molded product. The obtained urethane molded product was allowed to cool to 25°C, heated again in an oven at 120°C for 5 hours, and then sliced ​​to a thickness of 1.3 mm to obtain each polishing layer.

[0063] (Cushion layer manufacturing) A nonwoven fabric made of polyester fibers was immersed in a urethane resin solution (manufactured by DIC Corporation, product name "C1367"). After immersion, the resin solution was squeezed out using a mangle roller that can apply pressure between a pair of rollers, allowing the nonwoven fabric to be substantially uniformly impregnated with the resin solution. The fabric was then immersed in a coagulation liquid consisting of water at room temperature to coagulate and regenerate the impregnated resin, yielding a resin-impregnated nonwoven fabric. The resin-impregnated nonwoven fabric was then removed from the coagulation liquid and further immersed in a washing liquid consisting of water to remove N,N-dimethylformamide (DMF) from the resin, followed by drying. After drying, the surface skin layer was removed by buffing to produce a cushion layer with a thickness of 1.3 mm.

[0064] Examples and Comparative Examples Each polishing layer and cushion layer formed from the components shown in Table 1 were bonded with 0.1 mm thick double-sided tape (a PET substrate with an acrylic resin adhesive on both sides) to produce the polishing pads of Examples 1 to 4 and Comparative Examples 1 to 3. In addition, a conventionally known polishing pad, IC1000 (manufactured by Nitta Haas Corporation), was used as Comparative Example 4. Furthermore, Ester A represents a polyester diol having a number average molecular weight of 1,000 obtained by reacting adipic acid with diethylene glycol, Ester B represents a polyester diol having a number average molecular weight of 1,000 obtained by reacting adipic acid with butanediol, and PPG represents a polypropylene glycol having a number average molecular weight of 1,000.

[0065] [Table 1]

[0066] (density) Density of the polishing layer (g / cm 3 ) was measured in accordance with the Japanese Industrial Standard (JIS K 6505).

[0067] (D hardness) The D hardness of the abrasive layer was measured using a D-type hardness tester in accordance with the Japanese Industrial Standards (JIS-K-6253). Here, the measurement sample was obtained by stacking multiple abrasive layers as necessary to achieve a total thickness of at least 4.5 mm.

[0068] (wear test) The resulting polishing pad was subjected to a wear test using a small friction and wear tester under the following conditions: Figure 4 shows the wear amount (thickness) on the vertical axis and the PPG compounding ratio on the horizontal axis.

[0069] (Wear test conditions) Polishing machine used: Small friction and wear tester Indenter side: PAD (17φ) Plate side: #180 sandpaper Load: 300g Liquid: water Flow rate: 45ml / min Plate rotation speed: 40 rpm Time: 10 minutes Thickness measurement load: 300g

[0070] As can be seen from Figure 4, increasing the PPG blend ratio in the high molecular weight polyol increases the amount of wear and deteriorates the wear resistance. When the PPG blend ratio is less than 60% by weight, the increase in the amount of wear is suppressed. On the other hand, when the PPG blend ratio exceeds 60% by weight, the amount of wear increases sharply. This tendency was similar for both Ester A and B. Furthermore, when the PPG blend ratio was less than 60% by weight, the wear was comparable to that of the conventional polishing pad (0.10 mm) of Comparative Example 4. It should be noted that the mixture containing 100% of esters A and B had poor step-eliminating performance, as described below.

[0071] (Polishing performance evaluation) Using the resulting polishing pads of Example 1, Comparative Example 1 and Comparative Example 4, a polishing test was carried out under the following polishing conditions.

[0072] (polishing conditions) Polishing machine used: F-REX300X (manufactured by Ebara Corporation) Disk: A188 (3M) Polishing agent temperature: 20℃ Polishing platen rotation speed: 85 rpm Polishing head rotation speed: 86 rpm Grinding pressure: 3.5psi Polishing slurry (metal film): CSL-9044C (a mixture of CSL-9044C stock solution and purified water at a weight ratio of 1:9) (manufactured by Fujimi Corporation) Polishing slurry flow rate: 200 ml / min Polishing time: 60 seconds Object to be polished (metal film): Cu film substrate Pad break: 35N 10 minutes Conditioning: Ex-situ, 35N, 4 scans

[0073] (Step-eliminating performance test) The polishing pad was placed in the designated position on the polishing machine using double-sided tape with an acrylic adhesive, and polishing was performed under the above polishing conditions. The step elimination performance was evaluated by measuring 100 μm / 100 μm dishing using a step / surface roughness / microprofile measuring device (KLA Tencor, P-16+). The evaluation results are shown in Figure 5. A patterned wafer with a film thickness of 7000 angstroms and a step height of 3000 angstroms was polished by adjusting the polishing rate so that the amount of polishing per step was 1000 angstroms. The polishing was performed in stages, and the wafer step height was measured each time. The step height on the vertical axis represents the step height. In Figure 5, 120 μm in the upper left indicates polishing of a wiring width of 120 μm, 100 / 100 in the upper right indicates a wiring with a Cu wiring width of 100 μm and an insulating film width of 100 μm, 50 / 50 in the lower left indicates a wiring with a Cu wiring width of 50 μm and an insulating film width of 50 μm, and 10 / 10 in the lower right indicates a wiring with a Cu wiring width of 10 μm and an insulating film width of 10 μm.The smaller the number, the finer the wiring. (Defect performance evaluation) The 15th, 25th, and 50th polished substrates were inspected for defects (surface defects) of 90 nm or larger using the high-sensitivity measurement mode of a surface inspection device (KLA-Tencor, Surfscan SP2XP). For each defect detected, SEM images taken with a review SEM were analyzed, and the number of scratches was counted. The results are shown in Figure 6.

[0074] As can be seen from Figure 5, the polishing pad of Example 1 had a faster step-eliminating speed than the conventionally known polishing pad of Comparative Example 4, and had step-eliminating performance almost the same as that of the polishing pad of Comparative Example 1, which had excellent step-eliminating performance. Furthermore, as can be seen from FIG. 6, the polishing pad of Example 1 had significantly fewer scratches than the conventionally known polishing pads of Comparative Example 4 and Comparative Example 1, and exhibited excellent defect performance. Although not shown in the figures, Examples 2 to 4 also had the same level difference eliminating performance and defect reduction performance as Example 1. [Industrial Applicability]

[0075] The present invention contributes to the manufacture and sale of polishing pads and has industrial applicability.

[0076] 1 Polishing equipment 3 polishing pads 4 Polishing layer 4A Hollow microsphere 6 Cushion layer 7 Adhesive layer 8 Object to be polished 9. Slurry 10 Polishing plate

Claims

1. A polishing pad having a polishing layer made of a polyurethane resin foam derived from an isocyanate-terminated prepolymer and a curing agent, the isocyanate-terminated prepolymer contains a polyisocyanate compound-derived constitutional unit and a high-molecular-weight polyol-derived constitutional unit; the high-molecular-weight polyol-derived structural units include at least polypropylene glycol structural units and polyester diol structural units derived from a dicarboxylic acid compound and a diol compound; the dicarboxylic acid compound is at least one selected from the group consisting of an aliphatic dicarboxylic acid, an unsaturated bond-containing dicarboxylic acid, and an alicyclic polycarboxylic acid; A polishing pad, wherein the polypropylene glycol constituent units account for 30 to 50% by weight of the constituent units derived from the high-molecular-weight polyol.

2. A polishing pad as described in claim 1, wherein the polyester diol constituent unit is derived from a polyester diol having a number average molecular weight of 600 to 2,500.

3. A method for manufacturing a polishing pad having a polishing layer made of polyurethane resin foam, comprising: a step of reacting a polyisocyanate compound with a high molecular weight polyol containing at least polypropylene glycol and a polyester diol to obtain an isocyanate-terminated prepolymer; a step of reacting the isocyanate-terminated prepolymer with a curing agent to obtain the polyurethane resin foam; and forming the polyurethane resin foam into a polishing layer shape, the polyester diol is obtained by reacting a dicarboxylic acid compound with a diol compound, the dicarboxylic acid compound is at least one selected from the group consisting of an aliphatic dicarboxylic acid, an unsaturated bond-containing dicarboxylic acid, and an alicyclic polycarboxylic acid; The production method, wherein the polypropylene glycol is 30 to 50% by weight based on the total amount of the high-molecular-weight polyol.

Images