Polishing pad and method for producing the same

Abstract

To provide an abrasive pad that strikes a balance between the polishing properties of an edge of an abrasive layer and reduction of scratches.SOLUTION: An abrasive pad has an abrasive layer composed of an isocyanate-terminated prepolymer and a hardener-derived polyurethane resin. The isocyanate-terminated prepolymer has at least a polyisocyanate compound-derived constitutional unit, and a polyol-derived constitutional unit having a C5 to C10 dangling chain.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a polishing pad (particularly a polishing pad for CMP) for polishing optical materials, semiconductor wafers, semiconductor devices, substrates for hard disks, metal and ceramic surfaces, and the like. [Background technology]

[0002] Chemical mechanical polishing (CMP) is commonly used as a 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 carrying out the CMP method is provided with a polishing pad 3, which contacts an object 8 to be polished held on a holding platen 16 and includes a polishing layer 4, which is a layer for polishing, and a cushion layer 6 for supporting the polishing layer 4. The polishing pad 3 is rotated while the object 8 to be polished is pressed against it, and polishes the object 8 to be polished. At that time, 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 grains, and the chemical components and abrasive grains in the slurry are flowed and move relative to the object 8 to increase the polishing effect. The slurry 9 is supplied to the polishing surface through grooves or holes and discharged.

[0004] In the field of hard polyurethane polishing pads manufactured by the molding method, prepolymers have been studied to obtain the desired polishing performance. In particular, the chemical structure portion derived from the polyol in the prepolymer is important because it becomes the main chain of the polyurethane resin.

[0005] Patent Document 1 discloses a polyurethane polishing pad derived from a polyol having a repeating unit of ethylene oxide in the side chain.

[0006] Patent Document 2 discloses a polishing pad derived from a polyol having an alkylene glycol with a molecular weight of 50-300. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2012-714 A [Patent Document 2] JP 2016-190313 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, these conventional polishing pads leave something to be desired in terms of flatness, which allows the workpiece to be polished evenly from the center to the edge, and in particular, there is a problem with the over-polishing phenomenon known as "edge sagging," in which the very edge of the workpiece 8 is polished more than the center. In order to solve the problem of edge sagging, a method of hardening the polishing pad to such an extent that it does not follow the edge shape can be considered, but hardening this then causes a problem of increased scratches, making it difficult to achieve both edge polishing characteristics and scratch reduction.

[0009] The present invention has been made in consideration of the above problems, and has an object to provide a polishing pad which achieves both polishing characteristics at the end of the polishing layer and reduced scratches. [Means for solving the problem]

[0010] As a result of intensive research, the inventors of the present invention found that flatness and scratches can be improved by forming a polishing pad containing a polyurethane polishing layer containing a component derived from a prepolymer of a specific composition, and thus achieved the present invention. [1] A polishing pad having a polishing layer made of a polyurethane resin derived from an isocyanate-terminated prepolymer and a curing agent, The polishing pad, wherein the isocyanate-terminated prepolymer contains at least a structural unit derived from a polyisocyanate compound and a structural unit derived from a polyol having a dangling chain having 5 to 10 carbon atoms. [2] The polishing pad described in [1], wherein the dangling chain is a linear alkyl group. [3] The polishing pad according to [1] or [2], wherein the polishing layer contains hollow microspheres. [4] The density of the polishing layer is 0.7 to 0.9 g / cm 3 and the polishing layer has a D hardness of 50 to 70 degrees. [5] The polishing pad according to any one of [1] to [4], wherein the curing agent contains at least 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA). [6] The polishing pad according to any one of [1] to [5], which is a laminated polishing pad further comprising a cushion layer having teardrop-shaped bubbles laminated thereon. [7] A method for producing a polishing pad having a polishing layer made of a polyurethane resin, comprising: A step of reacting a polyisocyanate compound with a polyol having a dangling chain having 5 to 10 carbon atoms to obtain an isocyanate-terminated prepolymer; a step of reacting the isocyanate-terminated prepolymer with a curing agent to obtain the polyurethane resin; and forming the polyurethane resin into a shape of a polishing layer. Effect of the Invention

[0011] By using a specific polyol as a raw material for the isocyanate-terminated prepolymer, it is possible to provide a polishing pad that achieves both the flatness polishing characteristics of the polishing layer (polishing characteristics of the edges) and reduced scratches. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view of a polishing apparatus 1. As shown in FIG. [Diagram 2]FIG. 2 is a cross-sectional view of the polishing pad. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, a mode for carrying out the invention will be described, however, the present invention is not limited to the mode for carrying out the invention.

[0014] <<Polishing pad>> 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, if necessary, a cushion layer 6. The shape of the polishing pad 3 is preferably disc-shaped, but is not particularly limited thereto, and the size (diameter) can be appropriately determined 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 a polishing platen 10 of the polishing device 1 by double-sided tape or the like arranged on the cushion layer 6. The polishing pad 3 is rotated by the polishing device 1 while pressing against an object 8 to be polished, and polishes the object 8 (see FIG. 1).

[0015] <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 constituting 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 platen 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. In the case where hollow microspheres 4A are dispersed, when the polishing layer 4 is worn, the hollow microspheres 4A are exposed on the polishing surface, generating minute voids on the polishing surface, and these minute voids hold the slurry, thereby allowing polishing of the object 8 to proceed more rapidly.

[0016] 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. That is, the polishing layer 4 is formed by a molding method.

[0017] (Hollow microspheres) The hollow microspheres 4A contained in the polishing layer 4 of the polishing pad of the present invention can be confirmed as hollow bodies on the polishing surface of the polishing layer 4 or on the 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, elliptical, or similar shapes. From the viewpoint of improving polishing accuracy, it is preferable to have foaming by hollow microspheres, which not only makes the foaming diameter more uniform but also suppresses end sagging caused by the slurry penetrating into the polishing layer and deterioration of the polishing layer due to the formation of independent bubbles, rather than mechanical foaming in which an inert gas is mixed or a chemical foaming agent represented by water.

[0018] The hollow microspheres 4A may be commercially available balloons, and may be expanded or unexpanded. The unexpanded ones are heat-expandable microspheres, which can be expanded by heating.

[0019] (grooving) The surface of the polishing layer 4 of the present invention facing the polished object 8 may be provided with grooves. The grooves are not particularly limited, and may be either slurry discharge grooves communicating with the periphery of the polishing layer 4 or slurry holding grooves not communicating with the periphery of the polishing layer 4, or may have both slurry discharge grooves and slurry holding grooves. Examples of the slurry discharge grooves include lattice grooves and radial grooves, and examples of the slurry holding grooves include concentric grooves and perforations (through holes), and these may also be combined.

[0020] (density) In the present invention, the density of the polishing layer is not limited. However, from the viewpoint that too high density may cause scratches, and too low density may cause edge sagging, it is preferably 0.65 to 0.95 g / cm. 3 and more preferably 0.70 to 0.90 g / cm 3 It is.

[0021] (D hardness) In the present invention, the D hardness of the polishing layer is not particularly limited, but is preferably 40 to 70 degrees, more preferably 45 to 65 degrees, since too high a hardness may cause scratches, and too low a hardness may cause edge drooping. In the polishing layer, when either one of the density and the D hardness, more preferably both, are within the above preferred ranges, it tends to be possible to achieve both flatness and scratch prevention.

[0022] <Cushion layer> (composition) The polishing pad 3 of the present invention may have a cushion layer 6 as necessary. The cushion layer 6 is desirable for making the polishing layer 4 contact the polished object 8 more uniform. The material of the cushion layer 6 may be any of impregnated nonwoven fabric impregnated with resin, flexible materials such as synthetic resins and rubbers, and foams having 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 elastic modulus, flexible synthetic resins are preferred, and polyurethane is preferred as the material.

[0023] More preferably, a cushion layer 6 made of polyurethane resin is used, which is desolvated with a water-based coagulation liquid (coagulation liquid mainly composed of water) and formed into a sheet (wet film formation). The cushion layer 6 has a foam structure with teardrop-shaped bubbles 6A formed therein. The cushion layer 6 is also preferably made of polyurethane resin having sponge-like fine bubbles. By using a cushion layer made of a wet film-formed polyurethane resin, it tends to have appropriate cushioning properties to suppress scratches while maintaining flatness.

[0024] 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. In the following, an example of the polishing pad of the present invention using a cushion layer made of a polyurethane resin formed by a wet film process will be described, but the cushion layer may not be used, and other cushion layers may be used.

[0025] <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 adhesive. The double-sided tape or adhesive may be any known double-sided tape or adhesive in the art (e.g., an adhesive sheet). The polishing layer 4 and the cushion layer 6 are bonded together by an adhesive layer 7. The adhesive layer 7 can be made 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.

[0026] <<Polishing pad manufacturing method>> A method for producing the polishing pad 3 of the present invention will now be described.

[0027] <Abrasive layer material> In the present invention, the material of the polishing layer is mainly composed of a polyurethane resin. A specific example of the main component is a polyurethane resin material obtained by reacting an isocyanate-terminated prepolymer with a curing agent.

[0028] 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 an isocyanate-terminated prepolymer; a material preparation step of preparing an 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.

[0029] The process will be explained below in detail, with each process being divided into a preparation process, a material preparation process, a mixing process, and a molding process.

[0030] <Preparation process> The isocyanate-terminated prepolymer used in the present invention contains at least a polyisocyanate compound-derived structural unit and a polyol-derived structural unit having a dangling chain with 5 to 10 carbon atoms, and the isocyanate-terminated prepolymer contains an isocyanate group at the molecular end. The isocyanate-terminated prepolymer can be obtained by reacting a polyisocyanate compound with a polyol having a dangling chain with 5 to 10 carbon atoms. There is no particular limitation on the reaction, and the addition polymerization reaction may be carried out using a method and conditions known in the production of polyurethane resins. For example, the polyisocyanate compound heated to 50°C is added to a polyol compound having a dangling chain with 5 to 10 carbon atoms heated to 40°C while stirring in a nitrogen atmosphere, and the polyol compound can be produced by a method in which the polyisocyanate compound heated to 50°C is added to the polyol compound having a dangling chain with 5 to 10 carbon atoms heated to 40°C, and the polyol compound is heated to 80°C after 30 minutes and further reacted at 80°C for 60 minutes.

[0031] Each component will be described below.

[0032] (Polyisocyanate compounds) The isocyanate-terminated prepolymer uses a polyisocyanate compound as a raw material.

[0033] The polyisocyanate compound is not particularly limited and may be a commercially available product. In this specification, the polyisocyanate compound means 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 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 in combination of a plurality of polyisocyanate compounds.

[0034] The polyisocyanate compound preferably contains 2,4-TDI and / or 2,6-TDI, more preferably contains 2,4-TDI and 2,6-TDI, and even more preferably consists of 2,4-TDI and 2,6-TDI. The mass ratio of 2,4-TDI to 2,6-TDI is preferably 100:0 to 50:50, more preferably 90:10 to 60:40, even more preferably 90:10 to 70:30, and even more preferably 80:20.

[0035] (Polyols as raw materials for isocyanate-terminated prepolymers) In the present invention, the isocyanate-terminated prepolymer can be obtained by using a polyol having a dangling chain having 5 to 10 carbon atoms. In this specification, the term "polyol compound" refers to a compound having two or more hydroxyl groups (OH) in the molecule. In this specification, the polyol compound has a main chain and a dangling chain. The main chain is a portion that forms the main skeleton of the polyol. Meanwhile, the "dangling chain" refers to a branched chain that is branched from the main chain and has one free end, and the "dangling chain having 5 to 10 carbon atoms" refers to a dangling chain having 5 or more and 10 or less carbon atoms. In this specification, the polyol compound is used as a raw material for an isocyanate-terminated prepolymer, so that the longest carbon chain having hydroxyl groups at both ends is treated as the main chain. In other words, the "dangling chain" refers to a branched chain that does not have a hydroxyl group at its end.

[0036] The main chain of a polyol having a dangling chain having 5 to 10 carbon atoms may contain a nitrogen atom and an oxygen atom in addition to a carbon atom, a hydrogen atom and a hydroxyl group. On the other hand, the dangling chain may contain a carbon atom, a nitrogen atom and an oxygen atom in addition to a carbon atom and a hydrogen atom, but from the viewpoint of controlling the reaction and physical properties, a preferred dangling chain is one composed of a hydrocarbon composed of carbon atoms and hydrogen atoms, and a more preferred dangling chain is one composed of an alkyl group.

[0037] The dangling chain itself may be linear or may have a branched chain, but in order to ensure the flatness and scratch suppression effects, it is preferably linear (not branched), and is most preferably a linear alkyl group.

[0038] The carbon number of the dangling chain is usually 5 or more and 10 or less. If the carbon number of the dangling chain is less than 5, the branched chain is too short, and the cohesive force (intermolecular force) of the resin molecules constituting the polishing layer increases, resulting in insufficient elasticity, and the end shape, especially the end of the polished object, may become uneven, and the flatness improvement effect may not be obtained. Also, if the carbon number exceeds 10, the main chain of the isocyanate-terminated prepolymer must be shortened accordingly, so the polishing layer becomes too hard and it becomes difficult to obtain the scratch suppression effect. The preferred carbon number of the dangling chain is 6 or more and 9 or less. The number of carbon atoms in the main chain of the polyol having a dangling chain with 5 to 10 carbon atoms is not particularly limited, but is, for example, 25 to 65, preferably 30 to 60. If the main chain has 25 or more carbon atoms, the polyol main chain length is sufficiently long relative to the tangling chain, so that the effect of steric hindrance of the tangling chain on the reaction can be reduced, which is preferable, and if it is 65 or less, the hardness derived from the main chain length can be maintained high, so that sagging at the ends can be suppressed, which is preferable. Examples of polyols having a dangling chain with 5 to 10 carbon atoms include 5-octyl-1,30-triacontanediol (main chain carbon number: 30, dangling chain carbon number: 8), and other examples include 1,36-hentetracontanediol (main chain carbon number: 36, dangling chain carbon number: 5) and 1,31-hentetracontanediol (main chain carbon number: 31, dangling chain carbon number: 10) used in the examples of this specification. Note that the above compounds are merely examples, and the connection position of the dangling chain to the main chain is not particularly limited.

[0039] The number average molecular weight of the polyol having a dangling chain having 5 to 10 carbon atoms used in the present invention is not particularly limited, but from the viewpoint of more reliably obtaining the effects of the present invention by controlling the length of the main chain and from the viewpoint of controlling the reaction in accordance with the NCO equivalent (described later) of the isocyanate-terminated prepolymer, a polyol having a number average molecular weight (Mn) of preferably 500 to 1100, more preferably 600 to 1000, can be mentioned. 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 number average molecular weight can be estimated by GPC.

[0040] The polyol used as the raw material for the isocyanate-terminated prepolymer may contain, in addition to the polyol having a dangling chain having 5 to 10 carbon atoms, other polyols within the scope of the present invention, but are not usually used in combination with other polyols. On the other hand, known isocyanate-terminated prepolymers may be used in combination within the scope of the present invention.

[0041] <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. Since the isocyanate-terminated prepolymer has already been described, the curing agent, additives, and hollow microspheres will be described here.

[0042] (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 the isocyanate-terminated prepolymer 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 in the subsequent molding step, which then hardens. 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, trimethylethylene bis-4-aminobenzoate, and polytetramethylene oxide-di-p-aminobenzoate; ethylene glycol, 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.In addition, 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. From the viewpoint of controlling the reaction, it is preferable to use a polyvalent amine compound, more preferably a diamine compound, and even more preferably 3,3'-dichloro-4,4'-diaminodiphenylmethane (methylenebis-o-chloroaniline) (hereinafter abbreviated as MOCA).

[0043] (Additives) Additives such as an oxidizing agent can be added as necessary 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.

[0044] (Hollow microspheres) The polishing layer 4 contains hollow microspheres 4A, which have an outer shell and are hollow inside, as necessary. As described above, the material of the hollow microspheres 4A can be a commercially available product. Alternatively, a product obtained by synthesis using a conventional method can be used. The material of the outer shell of the hollow microspheres 4A is not particularly limited, and examples thereof 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, and copolymers of two or more types of monomers constituting these resins. In addition, examples of commercially available hollow microspheres include, but are not limited to, Expancel series (trade name manufactured by Akzo Nobel), Matsumoto Microsphere (trade name manufactured by Matsumoto Yushi Co., Ltd.), and the like.

[0045] 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 2 to 4 parts by mass, based on 100 parts by mass of the isocyanate-terminated prepolymer.

[0046] In addition to the above components, conventionally used blowing agents may be used together 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 each of the above components may be blown in during the mixing step described below. Examples of the blowing agent include water and blowing agents mainly composed of hydrocarbons 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.

[0047] <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 in a state where the components are heated to a temperature that ensures the fluidity of each component. However, care must be taken when the components are heated too much, since the hollow microspheres expand and lose the desired aperture distribution.

[0048] <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 body). 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, the flowability is deteriorated, and it becomes difficult to mix uniformly during mixing. If the temperature is increased to decrease the viscosity, the pot life is shortened, and the mixing unevenness occurs, resulting in variation in the size of the hollow microspheres formed in the obtained molded product. For this reason, it is preferable to set the viscosity of the isocyanate-terminated prepolymer at a temperature of 50 to 80°C in the range of 500 to 4000 mPa·s. 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 about 50 to 80°C to be in a flowable state.

[0049] In the molding process, the mixture is reacted in a mold as necessary 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. At the same time as this crosslinking and hardening progresses, the isocyanate group of the isocyanate-terminated prepolymer reacts with the water dispersed and diluted in the dispersion liquid, generating carbon dioxide.

[0050] After obtaining the molded body, it is sliced ​​into sheets to form a plurality of polishing layers 4. A general slicing machine can be used for slicing. When slicing, the lower layer of the molded body is held, and the molded body is sliced ​​to a predetermined thickness starting from the upper layer. The slice thickness is set to, for example, a range of 1.3 to 2.5 mm. In the case of a foam molded in a 50 mm thick mold, for example, about 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 about 30 mm of the center. In the hardening and molding step, a foam is obtained in which hollow microspheres 4A are formed approximately uniformly inside.

[0051] If necessary, grooves may be formed on the polishing surface of the resulting polishing layer 4. In the present invention, the method of forming the grooves and their shape are not particularly limited.

[0052] Thereafter, a double-sided tape is attached to the surface of the polishing layer 4 opposite to the polishing surface of the polishing layer 4 obtained in this manner. There are no particular limitations on the double-sided tape, and any double-sided tape known in the art can be selected and used.

[0053] <Method of manufacturing the cushion layer 6> In the process of forming the cushion layer 6, the cushion layer 6 is formed by a wet film formation. That is, the cushion layer 6 is formed through each of the steps of a preparation step of preparing a resin solution in which a polyurethane resin is dissolved substantially uniformly in an organic solvent, a coagulation regeneration step of spreading the resin solution prepared in the preparation step into a sheet shape and removing the organic solvent from the resin solution in a water-based coagulation liquid to coagulate and regenerate a polyurethane body, and a washing and drying step of washing and drying the polyurethane body coagulated and regenerated in the coagulation regeneration step to form the cushion layer 6, which will be described in the order of steps below.

[0054] (preparation process) In the preparation step, a polyurethane resin and additives are dissolved in an organic solvent to prepare a resin solution. The resin solution is prepared by dissolving the polyurethane resin and additives substantially uniformly in a water-miscible organic solvent capable of dissolving the polyurethane resin, removing aggregates by filtration, and then degassing under vacuum. As the organic solvent, N,N-dimethylformamide (hereinafter abbreviated as DMF), dimethylacetamide (hereinafter abbreviated as DMAc), etc. can be used. For example, DMF is used as the organic solvent. The polyurethane resin can be selected from polyester-based, polyether-based, polycarbonate-based, and other resins.

[0055] As additives, pigments such as carbon black, hydrophilic activators that promote foaming, and hydrophobic activators that stabilize the solidification and regeneration of polyurethane resin can be used. By changing the type and amount of additives, the size and amount (number) of teardrop-shaped bubbles 6A formed inside the cushion layer 6 can be controlled. The compressive elastic modulus and density of the cushion layer 6 can be adjusted by selecting the polyurethane resin and organic solvent, the mixing ratio of the resin and the organic solvent, the size and amount of the teardrop-shaped bubbles 6A, and the thickness of the cushion layer 6. For example, the polyurethane resin is set to 45 to 62 parts and DMF is set to 8 to 30 parts per 100 parts of the resin solution.

[0056] (Coagulation regeneration process) In the coagulation regeneration process, the resin solution prepared in the preparation process is continuously applied (spread into a sheet) to the film-forming substrate, and the polyurethane resin is coagulated and regenerated into a sheet by immersing in a water-based coagulation liquid. The resin solution prepared in the preparation process is applied substantially uniformly to the strip-shaped film-forming substrate by a coating machine such as a knife coater at room temperature. At this time, the coating thickness (coating amount) of the resin solution is adjusted by adjusting the gap (clearance) between the coater and the film-forming substrate. In this example, the coating amount is adjusted so that the thickness of the cushion layer 6 is in the range of 0.5 to 2.0 mm. Flexible films, nonwoven fabrics, woven fabrics, etc. can be used as the film-forming substrate. When nonwoven fabrics or woven fabrics are used, in order to suppress the penetration of the resin solution into the film-forming substrate when it is applied, a pretreatment (sealing) is performed by immersing the nonwoven fabrics or woven fabrics in water or a DMF aqueous solution (a mixture of DMF and water) or the like. When a flexible film such as a PET film is used as the film-forming substrate, the pretreatment is not required because it does not have liquid permeability.

[0057] The film-forming substrate coated with the resin solution is immersed in an aqueous coagulating liquid mainly composed of water, which is a poor solvent for polyurethane resin. In the aqueous coagulating liquid, micropores constituting a skin layer are first formed on the surface of the coated resin solution to a thickness of about several μm. Then, as the replacement of DMF in the resin solution with the aqueous coagulating liquid progresses, the polyurethane body is coagulated and regenerated in a sheet shape on one side of the film-forming substrate. DMF is removed from the resin solution, and DMF is replaced with the aqueous coagulating liquid, forming a large number of teardrop-shaped bubbles 6A in a three-dimensional mesh shape in the polyurethane body. At this time, since the PET film of the film-forming substrate does not allow water to penetrate, the solvent is removed from the surface side (skin layer side) of the resin solution, and teardrop-shaped bubbles 6A with a larger pore size are formed on the film-forming substrate side than on the surface side. That is, inside the polyurethane body, a large number of bubbles 6 with rounded and approximately triangular cross sections are formed in a substantially uniformly distributed state along the thickness direction of the polyurethane body.

[0058] (Cleaning and drying process) In the washing and drying process, the strip-shaped (long) polyurethane body that has been coagulated and regenerated in the coagulation and regeneration process is washed and then dried to form the cushion layer 6. That is, the polyurethane body is peeled off from the film-forming substrate and washed in a washing liquid such as water to remove the DMF remaining in the polyurethane body. After washing, the polyurethane body is dried in a cylinder dryer. The cylinder dryer is equipped with a cylinder having a heat source inside. The polyurethane body passes along the circumferential surface of the cylinder to dry, and the cushion layer 6 is formed.

[0059] <Joining process> When a polishing pad having a laminated cushion layer is to be formed, the formed polishing layer 4 and cushion layer 6 are bonded (bonded) with an adhesive layer 7 in a bonding process. 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 the surface of the polishing layer 4 opposite to the polishing surface P with a substantially uniform thickness. The surface of the polishing layer 4 opposite to the polishing surface P and the surface of the cushion layer 6 (the surface on which the skin layer is formed) are pressed together via the applied adhesive, and the polishing layer 4 and cushion layer 6 are bonded with the adhesive layer 7. Then, after cutting into a desired shape such as a circle, an inspection is performed to confirm that there is no dirt or foreign matter attached, and the polishing pad 3 is completed. EXAMPLES

[0060] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0061] In each of the examples and comparative examples, unless otherwise specified, "parts" means "parts by mass".

[0062] The NCO equivalent is a numerical value showing the molecular weight of the prepolymer (PP) per NCO group, which is calculated by "(mass (parts) of polyisocyanate compound+mass (parts) of polyol compound) / [(number of functional groups per molecule of polyisocyanate compound×mass (parts) of polyisocyanate compound / molecular weight of polyisocyanate compound)-(number of functional groups per molecule of polyol compound×mass (parts) of polyol compound / molecular weight of polyol compound)]". The NCO equivalent of the isocyanate-terminated prepolymer used in the present invention is preferably 350 to 700, more preferably 400 to 650, from the viewpoint of more reliably obtaining the effects of the present invention.

[0063] (Manufacture of abrasive layer) As prepolymers for preparing the polishing pad, polyols A to D with different dangling chains and isocyanate-terminated prepolymers A to D derived from 2,4-TDI were prepared. The relationship between polyols A to D and isocyanate-terminated prepolymers A to D is shown in Table 1. The dangling chains of the polyols were all linear alkyl groups. Hollow microspheres (EXPANCEL461DE20D70 manufactured by Nippon Phillite Co., Ltd.) were added to the mixture, heated to 55°C, and degassed under reduced pressure. The hardener MOCA was dissolved at 120°C and degassed under reduced pressure. These were mixed in the weight ratio of prepolymer:MOCA:hollow microspheres shown in Table 2. The resulting mixture was poured into a mold, heat-cured at 80°C for 30 minutes, then demolded, heated in an oven at 120°C for 4 hours, and finally sliced ​​to a thickness of 1.3 mm to prepare a polishing layer. The polyols A to D used are listed below. Polyol A: 1,36-hexatetracontanediol (dangling chain carbon number 5) Polyol B: 1,31-tetracontanediol (dangling chain carbon number 10) Polyol C: 1,26-hexatetracontanediol (dangling chain carbon number 15) Polyol D: Polypropylene glycol (dangling chain carbon number 1)

[0064] [Table 1]

[0065] [Table 2]

[0066] (density) The density (g / cm 3 ) was calculated from the volume and weight of the measurement sample piece in accordance with the Japanese Industrial Standard (JISK6505).

[0067] (D hardness) The obtained polishing layer was subjected to D-hardness measurement using a D-type hardness tester in accordance with the Japanese Industrial Standards (JIS-K-6253). Here, the sample for measuring the D-hardness was obtained by stacking a plurality of measurement samples as necessary so that the total thickness was at least 4.5 mm.

[0068] (Manufacture of cushion layer) Polyester MDI (diphenylmethane diisocyanate) polyurethane resin was used as the polyurethane resin for preparing the cushion layer. 25 parts of DMF solvent, 40 parts of DMF dispersion containing 20% ​​carbon black as a pigment, and 2 parts of hydrophobic activator as a film formation stabilizer were added to 100 parts of 30% polyurethane resin solution and mixed to prepare a polyurethane resin solution. The obtained resin solution was applied to a PET substrate (thickness 0.188 mm) to a thickness of 0.7 mm, and the organic solvent was removed from the resin solution in a water-based coagulation liquid to prepare a cushion layer including the PET substrate. This cushion layer had a thickness of 0.7 mm and an A hardness of 59.

[0069] (Manufacture of polishing pads) The polishing layer 3 and the cushion layer 6 were attached together with a 0.1 mm thick double-sided tape (a PET substrate with an adhesive made of an acrylic resin on both sides) to produce a polishing pad.

[0070] (Polishing performance evaluation (creation of edge profile)) Polishing was carried out under the following polishing conditions for the polishing pads of the examples and comparative examples. The polishing rate (RR) was measured at 121 points in diameter during polishing. The inside of the radius of 140 mm was measured at a pitch of 2.5 mm, and the outside was measured at a pitch of 1 mm. After that, the polishing rate of the most edge part of the polished object (part 149 mm from the center) was divided by the average of the polishing rates of the parts 100 to 140 mm from the center to calculate the "most edge rate" and evaluate the edge sagging. The closer the most edge rate is to 1.00, the more uniform the polishing rate is at the center and the edge of the polished object, and the polished object can be polished flatly to the edge. In addition, when unevenness of 2% or more was confirmed above and below the part 143 to 147 mm in the polishing rate at the part outside 140 mm from the center of the polished object (corresponding to the over-polished part and its reaction part) was confirmed, it was evaluated as "with rebound".

[0071] (polishing conditions) Polishing machine used: Ebara Corporation, F-REX300X Disk: 3M A188(#100) Rotation speed: (table) 85 rpm, (top ring) 86 rpm Grinding pressure: 3.5psi Abrasive: Fujimi Incorporated, product number: PL6115 (PL6115 stock solution: pure water = 1:1 mixture by weight) Abrasive temperature: 20℃ Abrasive discharge rate: 200ml / min Polished object: 12-inch silicon wafer with tetraethoxysilane formed on it by PE-CVD to an insulating film thickness of 1 μm Pad break: 35N 10 minutes Conditioning: Ex-situ, 35N, 4 scans Number of polished sheets: 25 sheets

[0072] (Polishing performance evaluation (scratch resistance)) The scratch resistance of the polishing pads of the examples and comparative examples was evaluated. After polishing, the polished object was subjected to a high sensitivity measurement mode of a wafer surface inspection device (KLA Tencor, SurfscanSP2xpDLS) to detect defects (surface defects) with a size of 90 nm or more. Each detected defect was analyzed using a review SEM (Hitachi High-Technologies Corporation, RS-4000) to count the number of "scratches". The polishing test results are shown in Table 3.

[0073] [Table 3]

[0074] The polishing pads of Example 1 and Example 2 obtained good results in both the maximum edge rate and the number of scratches. On the other hand, in Comparative Example 1, in which the dangling chains were long, good flatness was obtained, but the number of scratches was significantly worse. In Comparative Example 2, in which the dangling chains were short, the number of scratches was good, but the flatness was worse. Therefore, it was confirmed that the flatness was good when the dangling chains were appropriately long, and that scratches could be suppressed when the dangling chains were not too long. [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 Cushioning Layer 6A Teardrop bubble 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 derived from an isocyanate-terminated prepolymer and a curing agent, The isocyanate-terminated prepolymer comprises at least a structural unit derived from a polyisocyanate compound and a structural unit derived from a polyol having a main chain having 30 to 60 carbon atoms and a dangling chain having 5 to 10 carbon atoms.

2. The polishing pad of claim 1 , wherein the dangling chain is a linear alkyl group.

3. The polishing pad of claim 1 or 2, wherein the polishing layer contains hollow microspheres.

4. The polishing pad according to any one of claims 1 to 3, wherein the polishing layer has a density of 0.7 to 0.9 g / cm3 and a D hardness of 50 to 70 degrees.

5. The polishing pad of any one of claims 1 to 4, wherein the curing agent comprises at least 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA).

6. 6. The polishing pad according to claim 1, wherein the polishing pad is a laminated polishing pad further comprising a cushion layer having teardrop-shaped bubbles laminated thereon.

7. A method for producing a polishing pad having a polishing layer made of a polyurethane resin, comprising: A step of reacting a polyisocyanate compound with a polyol having a main chain having 30 to 60 carbon atoms and a dangling chain having 5 to 10 carbon atoms to obtain an isocyanate-terminated prepolymer; reacting the isocyanate-terminated prepolymer with a curing agent to obtain the polyurethane resin; and forming the polyurethane resin into a shape of a polishing layer.

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