JP2019094380A - Polyurethane and polishing pad - Google Patents

Abstract

To provide a novel polyurethane suitably used as a material for a polishing layer of a polishing pad and excellent in moldability and abrasion resistance and to provide a polishing pad including a polishing layer excellent in productivity and abrasion resistance.SOLUTION: The polyurethane includes at least either one of (a) a polyurethane which includes a unit including a conjugated diene moiety, a unit including a dienophile moiety, a chain extender unit, a polymer polyol unit and an organic polyisocyanate unit and (b) a mixture of a first polyurethane which includes a unit including a conjugated diene moiety, a chain extender unit, a polymer polyol unit and an organic polyisocyanate unit and a second polyurethane which includes a unit including a dienophile moiety, a chain extender unit, a polymer polyol unit and an organic polyisocyanate unit. The polishing pad includes a polishing layer using the polyurethane.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a novel polyurethane and a polishing pad comprising the same.

  Chemical mechanical polishing (CMP) is known as a polishing method used to mirror-finish a semiconductor wafer or to planarize the surface of an insulating film or a conductor film of a semiconductor device. CMP is a method of polishing the surface of a material to be polished such as a wafer with a polishing pad in the presence of a slurry containing abrasive grains and a reaction solution.

  Integrated circuits are highly integrated and multilayered in semiconductor devices. Polishing pads used for planarization of semiconductor devices are required to have higher planarization performance. A polishing pad with high planarization performance has a high polishing rate of a portion to be polished and a low polishing rate of a portion not to be polished.

  In recent years, with the further high integration of semiconductor devices and the formation of multilayer interconnections, a high hardness polishing pad having high planarization performance is required. For example, Patent Document 1 below discloses a polishing pad provided with a thermoplastic polyurethane molded body as a polishing layer. In order to produce a high hardness thermoplastic polyurethane molded article, it is required to make the thermoplastic polyurethane a high molecular weight. However, since the thermoplastic polyurethane of high molecular weight has a high melt viscosity, there is a problem that the formability is reduced. When the composition of monomers of polyurethane is adjusted or the molecular weight of polyurethane is reduced in order to improve the moldability of thermoplastic polyurethane, the hardness is lowered to be an indicator of planarization performance and life. There is a problem that the wear resistance is reduced.

  By the way, the following patent document 2 discloses a chain-like thermoplastic resin for the purpose of achieving the contradictory properties of improving mechanical properties by increasing the degree of polymerization of the thermoplastic resin and improving fluidity at the time of molding. Do. Specifically, disclosed is a chain thermoplastic resin comprising a structure obtained by Diels-Alder reaction of a conjugated diene structure and a dienophile structure. And, as a basic skeleton of the linear thermoplastic resin, polyamide, polyester, polyethylene, polycarbonate, polypropylene, polyvinyl chloride, polystyrene, AS resin, methacrylic resin, polyvinyl alcohol, polyvinyl alcohol, polyvinylidene chloride, polyacetal, polyphenylene ether, polysulfone, polyether Disclosed are resins having thermoplasticity such as sulfone, polyphenylene sulfide, polyarylate, polyamide imide, polyether imide, polyether ether ketone, polyimide and copolymers thereof.

  Moreover, the following Patent Document 3 is capable of reversibly causing formation and collapse of a crosslinked structure by temperature change, has excellent heat resistance, has low cold flow properties, and is easily recyclable from a conjugated diene structure and a dienophile structure. Disclosed is an elastomer having a crosslinked structure formed by the Diels-Alder reaction.

  Also, conventionally, as a polishing pad, a non-woven fabric type polishing pad including a non-woven fabric impregnated with polyurethane is also known. The non-woven fabric type polishing pad is flexible and has an advantage in that it has good contact with the material to be polished. In addition, since the non-woven fabric has voids, the retention of the slurry is good. However, the non-woven fabric type polishing pad has a disadvantage that the life is easily shortened due to the low wear resistance.

JP 2014-038916 A Unexamined-Japanese-Patent No. 2003-286347 JP 2000-1529 A

  The present invention provides a novel polyurethane excellent in moldability and wear resistance, which is preferably used as a material of the polishing layer of a polishing pad, and a polishing pad including a polishing layer excellent in productivity and wear resistance. The purpose is to

  One aspect of the present invention is a polyurethane comprising (a) a unit comprising a conjugated diene moiety, a unit comprising a dienophile moiety, a chain extender unit, a polymeric polyol unit and an organic polyisocyanate unit, or (b) a conjugated diene moiety A first polyurethane comprising units comprising, chain extender units, polymeric polyol units and organic polyisocyanate units, a unit comprising dienophile moieties, chain extender units, polymeric polyol units and organic polyisocyanate units It is a polyurethane containing at least any one of the mixture with two polyurethanes.

  Such polyurethanes form a covalent bond by the Diels-Alder reaction of a conjugated diene moiety contained in a unit containing a conjugated diene moiety and a dienophile moiety contained in a unit containing a dienophile moiety, thereby forming a polymer. And the formed covalent bond is reversibly dissociated by heating to high temperature. By forming such a covalent bond, the covalent bond is dissociated by heating at the time of molding, and high fluidity is exhibited to reduce the molecular weight and reduce the viscosity. In addition, after molding, by regenerating the covalent bond, the polyurethane has a high molecular weight, and the abrasion resistance is improved.

  The unit containing a conjugated diene site and the unit containing a dienophile site do not become too high in molecular weight at the time of polymerization of the polyurethane because they are present at the end of each polyurethane main chain, and the reactivity of the Diels alder reaction is excellent. It is preferable from the point of view.

  As a preferable conjugated diene part contained in the unit containing a conjugated diene part, a 1, 3- butadiene structure, a furan ring, an imidazole ring etc. are mentioned, for example. Moreover, as a preferable dienophile site | part contained in the unit containing a dienophile site | part, a maleimide group, an acryloyl group, a vinyl ketone group etc. are mentioned, for example.

  The molar ratio between the unit containing a conjugated diene moiety and the unit containing a dienophile moiety (conjugated diene moiety / dienophile moiety) is preferably 0.1 to 10 from the viewpoint of easily achieving high molecular weight by the Diels-Alder reaction.

  In addition, it is easy to lower the viscosity when molded so that the total amount of the unit containing a conjugated diene site and the unit containing a dienophile site is 0.02 to 0.3 mmol / g, and after polymerization, the molecular weight becomes high It is preferable from the easy point.

  Moreover, when the content rate of the nitrogen atom originating in the organic polyisocyanate unit is 5-8 mass%, when using as a raw material of the polishing layer of a polishing pad, the point which the polishing layer which is especially excellent in planarization performance is obtained It is preferable from

  Moreover, it is preferable from the point which is excellent in abrasion resistance to have the covalent bond formed by making a conjugated diene site | part and a dienophile site | part make Diels-Alder reaction.

  In addition, another aspect of the present invention is a polishing pad including a polishing layer, wherein the polishing layer is a polyurethane having conjugated diene moiety and dienophile moiety in one molecule, or conjugated diene moiety and dienophile moiety each other. It is a polishing pad containing the polyurethane which has respectively in a different molecule | numerator. Such a polishing pad is excellent in productivity and abrasion resistance.

  When a polishing pad includes the polishing layer which is a molded object of thermoplastic polyurethane, it is preferable from the point which it is excellent in moldability, and expresses high abrasion resistance by making high molecular weight after molding.

  In addition, when the polishing pad is provided with a polishing layer containing polyurethane inside the non-woven fabric, it is excellent in the impregnating ability of the polyurethane into the void inside the non-woven fabric, and heating is performed to covalently bond the conjugated diene site and the dienophile site. It is preferable from the point which expresses high abrasion resistance and polishing rate by making the polyurethane molecular weight increase.

  According to the present invention, a polishing pad comprising a novel polyurethane excellent in moldability and wear resistance, which is preferably used as a material of the polishing layer of the polishing pad, and a polishing layer excellent in productivity and wear resistance Can be provided.

FIG. 1 is an explanatory view for explaining how a conjugated diene site contained in a polyurethane and a dienophile site react with Diels-Alder to form a covalent bond by a reversible reaction, thereby forming a high molecular weight or a molecular weight reduction by dissociation. It is. FIG. 2 is an explanatory view for explaining a polishing method using a polishing pad.

  First, the polyurethane of one embodiment according to the present invention will be described in detail. The polyurethane of this embodiment is a polyurethane comprising (a) a unit comprising a conjugated diene moiety, a unit comprising a dienophile moiety, a chain extender unit, a polymer polyol unit and an organic polyisocyanate unit, or (b) a conjugated diene moiety And a first polyurethane comprising a chain extender unit, a polymer polyol unit and an organic polyisocyanate unit, a unit comprising a dienophile site, a chain extender unit, a polymer polyol unit and an organic polyisocyanate unit And / or a mixture with a second polyurethane.

  FIG. 1 is an explanatory view for explaining the Diels-Alder reaction between a conjugated diene site dn contained in a unit including a conjugated diene site and a dienophile site dp at the end of the main chain of the polyurethane PU of the present embodiment. The Diels-Alder reaction is a reversible reaction. Specifically, as shown in FIG. 1 (a), conjugated diene site dn between different polyurethane PU molecules is obtained by heat treatment of heating polyurethane PU before Diels-Alder reaction at an appropriate temperature (eg, 40.degree. C. or higher). The dienophile site dp undergoes Diels-Alder reaction to form a covalent bond as shown in (b) to achieve high molecular weight. Further, the polyurethane having the covalent bond shown in (b) is further heat-treated by heating at a suitable temperature (for example, 140 ° C. or more), and the formed covalent bond is dissociated to lower the molecular weight. Further, the dissociated conjugated diene site dn and the dienophile site dp are cooled to form a covalent bond and to polymerize.

  The polyurethane of this embodiment is polymerized by causing a Diels-Alder reaction between a conjugated diene site and a dienophile site contained in the polyurethane to form a covalent bond. And, as the molecular weight of the polyurethane is increased, the abrasion resistance and mechanical properties are improved. Moreover, by heating at the time of molding, the formed covalent bond is dissociated to lower the molecular weight, thereby lowering the viscosity and expressing high fluidity. In addition, after molding, the covalent bond is regenerated and the polyurethane has a high molecular weight.

  The Diels-Alder reaction is not limited to the Diels-Alder reaction in a narrow sense, which is a reaction of a conjugated diene site or dienophile site which does not contain hetero atoms such as oxygen atom, nitrogen atom and sulfur atom, but also oxygen atom, nitrogen atom, sulfur atom, etc. Also included is the Hetero Diels-Alder reaction, which is a reaction of conjugated diene or dienophile sites containing hetero atoms of

  The polyurethane (a) is obtained by reacting a compound having a conjugated diene site and an active hydrogen, a compound having a dienophile site and an active hydrogen, a chain extender, a polymer polyol and an organic polyisocyanate compound as a monomer. Obtained by In addition, the first polyurethane contained in the polyurethane (b) is to react a compound having a conjugated diene site and an active hydrogen, a chain extender, a high molecular weight polyol and an organic polyisocyanate compound as a monomer. Obtained by Moreover, the 2nd polyurethane contained in a polyurethane (b) is made to react the compound which has a dienophile site | part and active hydrogen, a chain extender, a high molecular polyol, and an organic polyisocyanate compound as a monomer. can get.

  Here, a unit containing a conjugated diene moiety is a unit derived from a compound having a conjugated diene moiety and an active hydrogen, a unit containing a dienophile moiety is a unit derived from a compound having a dienophile moiety and an active hydrogen, a chain extender unit and The term "unit derived from a chain extender", "polymer polyol unit" means a unit derived from polymer polyol, and the organic polyisocyanate unit means a unit derived from an organic polyisocyanate compound.

  The compound having a conjugated diene moiety and an active hydrogen is a compound having a conjugated diene moiety and a functional group having at least one active hydrogen.

  As a conjugated diene moiety, aliphatic hydrocarbon skeletons such as 1,3-butadiene skeleton; aromatic hydrocarbon skeletons such as anthranyl ring; cyclic dienes such as cyclopentadiene and dicyclopentadiene; imidazole ring, furan ring, triazine ring And heterocyclic skeletons such as thiophene ring and pyrrole ring can be exemplified. Among these, a 1,3-butadiene skeleton, a furan ring and an imidazole ring are preferable from the viewpoint of being excellent in reactivity and easily achieving both moldability and abrasion resistance. Moreover, as a functional group which has active hydrogen, a hydroxyl group, a primary amino group, and a secondary amino group are mentioned. In addition, when the number of functional groups having active hydrogen is one, especially one, by introducing a conjugated diene moiety at the end of the polyurethane main chain, polymerization of polyurethane can be carried out. It is preferable from the point which molecular weight does not become high too much and is excellent in the reactivity of Diels-Alder reaction.

  Specific examples of the compound having a conjugated diene moiety and active hydrogen include, for example, 2,4-hexadien-1-ol, 2- (hydroxymethyl) anthracene, 2-hydroxymethyl-1-methylimidazole, 1- (2- And hydroxyethyl) imidazole, 4 (5)-(hydroxymethyl) imidazole, 1- (3-aminopropyl) imidazole, furfuryl alcohol, 2,5-furandiol, furfurylamine, 5-methylfurfurylamine and the like. These may be used alone or in combination of two or more. Among these, compounds containing one functional group having an active hydrogen such as 2,4-hexadien-1-ol, 1- (2-hydroxyethyl) imidazole, furfuryl alcohol, furfurylamine and the like are suitable for polymerization of polyurethane. It is preferable from the viewpoint that the molecular weight does not become too high during the reaction and the reactivity of the Diels-Alder reaction is excellent.

  Further, a compound having a dienophile site and an active hydrogen is a compound having a dienophile site and a functional group having at least one active hydrogen.

  The dienophile moiety is preferably a double bond adjacent to an electron withdrawing group such as a carbonyl group, a cyano group or a nitro group from the viewpoint of excellent reactivity of the Diels-Alder reaction. As a specific example of the dienophile site, for example, maleimide group, vinyl ketone group, acryloyl group, benzoquinone skeleton and the like can be mentioned. Moreover, as a functional group which has active hydrogen, a hydroxyl group, a primary amino group, and a secondary amino group are mentioned. In addition, when the number of functional groups having active hydrogen is one, especially one, by introducing a conjugated diene moiety at the end of the polyurethane main chain, polymerization of polyurethane can be carried out. It is preferable from the point which molecular weight does not become high too much and is excellent in the reactivity of Diels-Alder reaction.

  Specific examples of the compound having a dienophile site and an active hydrogen include, for example, N- (2-hydroxyethyl) maleimide, N- (2-aminoethyl) maleimide, N- (4-aminophenyl) maleimide, hydroxymethyl vinyl ketone , 2-hydroxyethyl acrylate, 4-hydroxybutyl acrylate and the like. These may be used alone or in combination of two or more.

  Moreover, as a chain extender, a low molecular weight compound having two active hydrogen-containing functional groups such as a hydroxyl group and an amino group, which are conventionally used in the production of polyurethanes, which do not contain conjugated diene sites and dienophile sites Be Specific examples of the chain extender include, for example, ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,4-bis (β-hydroxyethoxy) benzene, Diols such as 1,4-cyclohexanediol, cyclohexanedimethanol (1,4-cyclohexanedimethanol etc.), bis (β-hydroxyethyl) terephthalate, 1,9-nonanediol, spiro glycol etc .; ethylene diamine, trimethylene diamine, Tetramethylenediamine, Hexamethylenediamine, Octamethylenediamine, Nonamethylenediamine, Hydrazine, Xylylene Diamine, isophorone diamine, piperazine, o-phenylene diamine, m-phenylene diamine, p-phenylene diamine, adipic acid dihydrazide, isophthalic acid dihydrazide, diamine such as 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, etc. Can be mentioned. These may be used alone or in combination of two or more. Among these, compounds having two hydroxyl groups such as 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol and the like are preferable. .

  Further, as the high molecular weight polyol, high molecular weight polyols conventionally used for the production of polyurethane are used without particular limitation. Specific examples thereof include polyether diols such as poly (ethylene glycol), poly (propylene glycol), poly (tetramethylene glycol), poly (methyl tetramethylene glycol), etc .; polybutylene adipate, polycaprolactone, poly (3 And polyester diols such as -methyl-1,5-pentamethylene adipate); polycarbonate diols such as polyhexamethylene carbonate diol and the like. These may be used alone or in combination of two or more. Among these, polyether diols and polyester diols, particularly polyether diols, are preferred.

  The polymer polyol has a number average molecular weight of 500 to 3,000, more preferably 550 to 2,500, and particularly 600 to 2,000, and is excellent in mechanical properties such as hardness and tensile modulus, and used as a polishing layer of a polishing pad In this case, the planarization performance tends to be high. The number average molecular weight of the polymer polyol is a value calculated based on the hydroxyl value measured in accordance with JIS K 1557.

  Moreover, as an organic polyisocyanate compound, the organic polyisocyanate compound currently used for manufacture of the polyurethane conventionally is used without limitation. As specific examples thereof, for example, ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2,2,4- or 2,4,4'-trimethylhexamethylene diisocyanate, dodecamethylene diisocyanate, isophorone diisocyanate, isopropylidene Bis (4-cyclohexylisocyanate), 1,3-bis (isocyanatomethyl) cyclohexane, dicyclohexylmethane 4,4'-diisocyanate, lysine diisocyanate, 2,6-diisocyanatomethyl caproate, bis (2-isocyanate) Natoethyl) fumarate, bis (2-isocyanatoethyl) carbonate, 2-isocyanatoethyl-2,6-diisocyanatohexanoate, cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, 1,4- Aliphatic or alicyclic diisocyanates such as bis (isocyanatomethyl) cyclohexane; 2,4'- or 4,4'-diphenylmethane diisocyanate, 2,4- or 2,6-tolylene diisocyanate, m- or p-phenylene Diisocyanate, m- or p-xylylene diisocyanate, 1,5-naphthylene diisocyanate, 4,4'-diisocyanatobiphenyl, 3,3-dimethyl-4,4'-diisocyanatobiphenyl, 3,3-dimethyl And aromatic diisocyanates such as -4,4'-diisocyanatodiphenylmethane, chlorophenylene-2,4-diisocyanate and tetramethyl xylylene diisocyanate. These may be used alone or in combination of two or more. Among these, 4,4′-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, isophorone diisocyanate, 1,4-bis (isocyanatomethyl) cyclohexane, dicyclohexylmethane 4,4 ′ -At least one selected from diisocyanates, in particular 4,4'-diphenylmethane diisocyanate, is preferred from the viewpoint that a polyurethane having particularly excellent abrasion resistance can be easily obtained.

  The polyurethane (a) is obtained by reacting a compound having a conjugated diene site and an active hydrogen, a compound having a dienophile site and an active hydrogen, a chain extender, a polymer polyol and an organic polyisocyanate compound as a monomer. Obtained by In addition, the first polyurethane contained in the polyurethane (b) is to react a compound having a conjugated diene site and an active hydrogen, a chain extender, a high molecular weight polyol and an organic polyisocyanate compound as a monomer. Obtained by Moreover, the 2nd polyurethane contained in a polyurethane (b) is made to react the compound which has a dienophile site | part and active hydrogen, a chain extender, a high molecular polyol, and an organic polyisocyanate compound as a monomer. can get. The blend ratio of each component is suitably adjusted according to the target characteristic. For example, an isocyanate group contained in the organic polyisocyanate compound is 0.95 to 1.3 mol, and more preferably 0.96 to 1.10 per 1 mol of active hydrogen atoms contained in the polymer diol and the chain extender. It is preferable to mix | blend in the ratio used as a mole, especially 0.97 to 1.05 mole.

  The polymerization method of each polyurethane is not particularly limited, and each component described above can be polymerized as a monomer by a known melt polymerization method such as a prepolymer method or a one shot method, a solution polymerization method, or the like. The melt polymerization method can be produced, for example, by melt-kneading and polymerizing a mixture of each component used as a monomer in a predetermined ratio substantially in the absence of a solvent. As melt-kneading, for example, a method of continuous melt polymerization using a multi-screw extruder is mentioned. Moreover, as a solution-polymerizing method, it can manufacture, for example by mixing and polymerizing the mixture of these monomers in a predetermined ratio in an organic solvent.

  The molar ratio of the unit containing a conjugated diene moiety contained in the polyurethane to the unit containing a dienophile moiety (number of moles of conjugated diene moiety / number of moles of dienophile moiety) is 0.2 to 5, further 0.3 to 3, In particular, it is preferable that it is 0.5 to 2 because it is easy for the polyurethane to have a high molecular weight by the Diels-Alder reaction, whereby the abrasion resistance and the mechanical properties are easily improved. When the molar ratio between the conjugated diene moiety and the dienophile moiety is too low or too high, it tends to be difficult to simultaneously achieve moldability and wear resistance and planarization performance when used as a polishing layer.

  Further, the total amount of the unit containing a conjugated diene site and the unit containing a dienophile site contained in the polyurethane is 0.02 to 0.3 mmol / g, further 0.03 to 0.2 mmol / g, particularly preferably 0. It is preferable that it is 05-0.15 mmol / g from the point which is easy to make moldability and abrasion resistance compatible. If the total amount of the unit containing a conjugated diene site and the unit containing a dienophile site is too low or too high, the effect of the high molecular weight formation by the Diels-Alder reaction tends to be small. The total amount of the unit containing a conjugated diene moiety contained in the polyurethane and the unit containing a dienophile moiety is calculated as the sum of the number of moles per unit mass of the polyurethane.

  Moreover, it is polished that the nitrogen content rate derived from the polyisocyanate compound of polyurethane is 5-8 mass%, further 5.3-7.7 mass%, especially 5.6-7.4 mass%. When used as a material of the polishing layer of a pad, it is preferable from the point which the polishing layer which is especially excellent in planarization performance is obtained.

  The polyurethane may be a thermoplastic polyurethane or a thermosetting polyurethane. In addition, thermoplasticity means the characteristic which can be shape | molded by the forming method which passes through the process of making it heat-melt, such as extrusion molding, injection molding, calendar molding, 3D printer molding etc. The molded article of the thermoplastic polyurethane is obtained by molding the thermoplastic polyurethane by the various molding methods described above. When manufacturing a sheet-like molded article such as the polishing layer of a polishing pad, adopting extrusion molding using a T-die is advantageous in that a sheet-like molded article having a uniform thickness can be easily obtained. preferable.

  The polyurethane of this embodiment has a covalent bond formed by Diels-Alder reaction between a conjugated diene site and a dienophile site during polymerization of the polyurethane. This covalent bond is dissociated by reverse Diels-Alder reaction by heating at the time of molding. As a result, the moldability is improved by appropriately reducing the molecular weight of the polyurethane during molding. Also, after molding, the conjugated diene moiety and dienophile moiety react with Diels-Alder to form a covalent bond, whereby the polyurethane has a high molecular weight. Thereby, the wear resistance is improved, and when used as a material of the polishing layer, the planarization performance is improved.

  The Diels-Alder reaction can be promoted by further heat-treating the molded polyurethane molded body at an appropriate temperature. As a heat treatment condition, heat treatment at a temperature of 50 to 130 ° C., and further 60 to 120 ° C. for about 1 to 24 hours is preferable from the viewpoint that the Diels-Alder reaction can be sufficiently promoted.

  The conjugated diene moiety and the dienophile moiety are preferably at the end of the main chain of the polyurethane, from the viewpoint that the Diels alder reaction between the conjugated diene moiety and the dienophile moiety by heat treatment of the molded polyurethane molded body is likely to occur.

  The polyurethane of the present embodiment can be used in various applications that make use of the excellent properties of moldability and abrasion resistance. In particular, it is preferably used as a material for producing a polishing layer of a polishing pad for polishing a semiconductor wafer, a semiconductor device, a silicon wafer, a hard disk, a glass substrate, an optical product, or various metals.

  The polyurethane of this embodiment is a polishing pad provided with a non-foamed or foamed thermoplastic polyurethane molded article as a polishing layer, a non-woven fabric type polishing layer in which polyurethane is contained in an internal void of non-woven fabric, and cast foam curing. It is used as a polyurethane material of various types of abrasive layers, such as an abrasive layer mainly based on the polyurethane foam manufactured. The polyurethane may be a thermoplastic polyurethane or a thermosetting polyurethane. Among these, an abrasive layer of a thermoplastic polyurethane molded article is preferable from the viewpoint of being capable of continuous production by continuous melt polymerization and being excellent in sheet formability. In addition, the polishing layer of the non-foamed thermoplastic polyurethane molded article is particularly preferable in that the polishing characteristics do not easily change and stable polishing can be realized. For example, in the case of a polishing layer using a polyurethane foam produced by casting, foaming and curing, polishing characteristics such as flatness and planarization efficiency tend to fluctuate due to variations in the foam structure. Also, there is a tendency that it is difficult to achieve high hardness to improve the flatness.

  As a method of producing a non-woven fabric type polishing layer containing polyurethane in the internal void of non-woven fabric, a polyurethane solution produced by solution polymerization or polyurethane produced by melt polymerization is dissolved in an organic solvent such as dimethylformamide (DMF) There is a method in which the non-woven fabric is impregnated with the polyurethane solution and the polyurethane is contained in the internal void of the non-woven fabric by wet coagulation or dry coagulation. In particular, it is preferable to wet-set the polyurethane after impregnating the polyurethane solution into the non-woven fabric from the viewpoint that the polyurethane having a fine foamed structure can be uniformly applied to the non-woven fabric. In addition, since the polyurethane of this embodiment is reduced in molecular weight in a solution and has a low solution viscosity, the polyurethane solution can be uniformly penetrated to the inside even to a nonwoven fabric with a high fiber density. Further, after solidification of the polyurethane, the Diels alder reaction between the conjugated diene site and the dienophile site is promoted by heat treatment, whereby the polyurethane has a high molecular weight, and the abrasion resistance, the polishing rate and the planarization performance are improved.

  As a heat treatment condition for promoting the Diels-Alder reaction, for example, a condition of heat treatment at a temperature of 60 to 120 ° C. for about 1 to 24 hours may be mentioned.

As the non-woven fabric used for the non-woven fabric type polishing layer, those conventionally used for the non-woven fabric type polishing layer are used without particular limitation. In addition, since the solution of the polyurethane of the present embodiment has a low solution viscosity, it has been difficult to impregnate the solution uniformly to the inside conventionally, the apparent density is 0.4 g / cm ³ or more, further, 0. Even if it is a non-woven fabric having a high density of 5 g / cm ³ or more, the polyurethane solution can uniformly penetrate to the inside.

The weight ratio of the non-woven fabric to the polyurethane in the non-woven fabric type polishing layer is not particularly limited, but non-woven fabric / polyurethane is preferably 50/50 to 90/10 from the viewpoint of excellent polishing rate and abrasion resistance. The apparent density of the non-woven fabric type polishing layer is not particularly limited either, but is preferably 0.6 to 1.2 g / cm ³ from the viewpoint of excellent polishing rate and flattening performance.

  The abrasive layer is adjusted in size, shape, thickness and the like by cutting, slicing, buffing, punching and the like. The thickness of the polishing layer is not particularly limited and may be appropriately adjusted depending on the layer configuration and use of the polishing pad, and specifically, for example, 0.8 to 3.0 mm, and further 1.0 to 2 or more. It is preferably 5 mm, particularly 1.2 to 2.0 mm. Moreover, it is preferable that a recessed part like a groove | channel or a hole is formed in the grinding | polishing surface of a grinding | polishing layer by a grinding process or laser processing by the concentric-shaped predetermined | prescribed pattern. Such a recess supplies a slurry uniformly and sufficiently to the polishing surface, and also serves to discharge polishing debris that causes scratching and to prevent wafer breakage due to adsorption of the polishing layer. For example, when the grooves are formed concentrically, the distance between the grooves is preferably about 1.0 to 50 mm, more preferably 1.5 to 30 mm, and particularly preferably about 2.0 to 15 mm. The width of the groove is preferably about 0.1 to 3.0 mm, and more preferably about 0.2 to 2.0 mm. The depth of the groove is preferably 0.2 to 1.8 mm, and more preferably 0.4 to 1.5 mm. Moreover, as a cross-sectional shape of a groove | channel, shapes, such as a rectangle, a trapezoid, a triangle, and a semicircle, are suitably selected according to the objective, for example.

  The polishing pad may be formed only of the above-described polyurethane polishing layer, or may be a laminate in which a cushion layer is laminated on the non-abrasive surface of the polishing layer as necessary. The cushion layer is preferably a layer having a hardness lower than that of the polishing layer. When the hardness of the cushioning layer is lower than that of the polishing layer, the hard polishing layer follows the local unevenness of the surface to be polished, and the cushioning layer follows the warpage or waviness of the entire substrate to be polished. Thus, it is possible to achieve excellent balance between global flatness and local flatness.

  As a specific example of the material used as a cushion layer, a composite (for example, “Suba 400” (manufactured by Nitta Haas Co., Ltd.) in which a nonwoven fabric is impregnated with polyurethane); natural rubber, nitrile rubber, polybutadiene rubber, silicone rubber, etc. Thermoplastic elastomers such as polyester thermoplastic elastomers, polyamide thermoplastic elastomers, and fluorine thermoplastic elastomers; foamed plastics; polyurethanes and the like. Among these, polyurethane having a foam structure is particularly preferable in that a preferable flexibility as a cushion layer can be easily obtained.

  The thickness of the cushion layer is not particularly limited, but is preferably, for example, about 0.5 to 5 mm. If the cushion layer is too thin, the effect of following the overall warpage and waviness of the surface to be polished tends to be reduced, and the global flatness tends to be reduced. On the other hand, when the cushion layer is too thick, the entire polishing pad tends to be soft and difficult to perform stable polishing. When laminating a cushioning layer on the polishing layer, the thickness of the polishing pad is preferably about 0.3 to 5 mm.

  Next, an embodiment of CMP using a polishing pad as described above will be described.

  In CMP, for example, a CMP apparatus 10 provided with a circular rotary surface plate 2, a slurry supply nozzle 3, a carrier 4 and a pad conditioner 6 when viewed from above as shown in FIG. 2 is used. The polishing pad 1 provided with the above-described polishing layer is attached to the surface of the rotary surface plate 2 with a double-sided tape or the like. Further, the carrier 4 supports the material to be polished 5.

  In the CMP apparatus 10, the rotary surface plate 2 is rotated in the direction indicated by the arrow by a motor (not shown). Further, the carrier 4 is rotated, for example, in a direction indicated by an arrow by a motor (not shown) in the plane of the rotary surface plate 2. The pad conditioner 6 is also rotated, for example, in the direction indicated by the arrow by a motor (not shown) in the plane of the rotary surface plate 2.

  First, while flowing distilled water to the polishing surface of the rotating polishing pad 1 fixed on the rotary surface plate 2, for example, the pad conditioner 6 for CMP in which diamond particles are fixed to the carrier surface by nickel electrodeposition etc. The conditioning of the polishing surface of the polishing pad 1 is performed. By conditioning, the polishing surface is adjusted to a surface roughness suitable for polishing the surface to be polished. Next, the slurry 7 is supplied from the slurry supply nozzle 3 to the polishing surface of the rotating polishing pad 1. When performing CMP, a lubricating oil, a coolant and the like may be used in combination with the slurry, if necessary.

  Here, the slurry may be, for example, a liquid medium such as water or oil; an abrasive such as silica, alumina, cerium oxide, zirconium oxide or silicon carbide; an oxidant such as a base, an acid, a surfactant or a hydrogen peroxide solution, A slurry used for CMP containing a reducing agent, a chelating agent and the like is preferably used.

  Then, the polishing material 1 which is fixed to the carrier 4 and rotates is pressed against the polishing pad 1 on which the slurry 7 is uniformly spread on the polishing surface of the polishing layer. Then, the polishing process is continued until a predetermined flatness is obtained. The finish quality is affected by adjusting the pressing force applied during polishing and the speed of relative movement between the rotary surface plate 2 and the carrier 4.

  The polishing conditions are not particularly limited, but in order to perform polishing efficiently, the rotational speed of each of the rotary surface plate and the carrier is preferably low at 300 rpm or less, and the pressure applied to the material to be polished is scratched after polishing Preferably, the pressure is 150 kPa or less. It is preferable to continuously supply the slurry to the polishing surface with a pump or the like while polishing. Although the supply amount of the slurry is not particularly limited, it is preferable to supply so that the polishing surface is always covered with the slurry.

  Then, after the material to be polished after the completion of polishing is thoroughly washed with running water, it is preferable to use a spin drier or the like to remove water droplets adhering to the material to be polished and to dry it. Thus, by polishing the surface to be polished with a slurry, a smooth surface can be obtained over the entire surface to be polished.

  Such CMP according to this embodiment is preferably used for polishing in manufacturing processes of various semiconductor devices, MEMS (Micro Electro Mechanical Systems), and the like. Examples of the object to be polished include insulating films such as oxide films formed on a semiconductor substrate, metal films for wiring such as copper, aluminum and tungsten; barrier metal films such as tantalum, titanium, tantalum nitride and titanium nitride, In particular, it is preferably used to polish an insulating film such as an oxide film. It is also possible to polish a metal film on which a pattern such as a wiring pattern or a dummy pattern is formed. The pitch between lines in the pattern varies depending on the product, but is usually about 50 nm to 100 μm.

  Hereinafter, the present invention will be more specifically described by way of examples. The scope of the present invention is not limited to these examples.

  First, the compound having conjugated diene moiety and active hydrogen, the compound having dienophile moiety and active hydrogen, the organic polyisocyanate compound, the polymer polyol, and the chain extender used in the production of the polyurethane in this example are summarized below. .

<Compound Having Conjugated Diene Moiety and Active Hydrogen>
・ 2,4-hexadien-1-ol (HDO)
・ Furfuryl alcohol (FUR)

Compound having dienophile site and active hydrogen
・ N-2-hydroxyethyl maleimide (HEMI)
・ Acrylate 4-hydroxybutyl (HBA)
・ Hydroxymethyl vinyl ketone (HMVK)

<Polyisocyanate compound>
・ 4,4'-diphenylmethane diisocyanate (MDI)

<Polymer polyol>
・ Polyethylene glycol with a number average molecular weight of 600 (PEG 600)
・ Polytetramethylene glycol (PTG850) with a number average molecular weight of 850
・ Polytetramethylene glycol with a number average molecular weight of 2000 (PTG 2000)

Chain extender
・ 1,4-butanediol (BD)
・ 3-Methyl-1,5-pentanediol (MPD)
・ Trimethylolpropane (TMP)
・ 6-amino-1-hexanol (6AH)

Example 1
The monomer mixture mixed in the ratio of HDO: PEG600: BD: MPD: MDI = 1.0: 12.8: 14.5: 8.0: 63.7 (mass ratio) was prepared. Then, the monomer mixture is continuously supplied to a twin-screw extruder having a cylinder temperature of 75 to 260 ° C. in each zone by a metering pump and continuously melt polymerized while being kneaded, and is continuously discharged from the twin-screw extruder. The molten polyurethane strands were cooled in water and then chopped with a pelletizer to obtain thermoplastic first polyurethane pellets. The nitrogen atom content derived from the isocyanate group calculated from the raw material compounding ratio was 7.1% by mass.

  Moreover, the monomer mixture mixed in the ratio of HEMI: PEG600: BD: MPD: MDI = 1.4: 12.8: 14.4: 8.0: 63.4 (mass ratio) was prepared. Then, the monomer mixture is continuously supplied to a twin-screw extruder having a cylinder temperature of 75 to 260 ° C. in each zone by a metering pump and continuously melt-polymerized while being kneaded, thereby having a dienophile site at the end Of polyurethane. The molten polyurethane strand continuously discharged from the twin-screw extruder was continuously extruded into water and cooled, and then chopped with a pelletizer to obtain thermoplastic polyurethane pellets. The nitrogen atom content derived from the isocyanate group calculated from the raw material compounding ratio was 7.1% by mass.

  The obtained pellets of the first polyurethane and the second polyurethane were mixed such that the mass ratio of the first polyurethane to the second polyurethane was 1: 1. The molar ratio of the unit containing the conjugated diene moiety contained in the polyurethane to the unit containing the dienophile moiety (the number of moles of conjugated diene moiety / the number of moles of dienophile moiety) calculated from the raw material blending ratio was 1.03. Moreover, the total of the unit position containing the conjugated diene site | part calculated from the raw material compounding ratio, and the unit position containing the dienophile part was 0.101 mmol / g. The moldability of the polyurethane was evaluated by the following evaluation method.

<Formability>
A single-screw extruder (screw diameter 90 mm) equipped with a T-die equipped with a filter equipped with a pressure gauge was prepared. Then, polyurethane pellets are supplied to a single-screw extruder, discharged from a T-die, and passed through a pair of rolls with a gap interval of 1.8 mm, which is controlled to 60-80 ° C., to a thickness of 2 mm. A non-foamed polyurethane sheet was obtained. The conditions of the single-screw extruder were set to a feeding cylinder temperature of 215 to 240 ° C and a die temperature of 230 to 240 ° C. And the moldability at this time was evaluated by the following method.
A: No unmelted material was observed at the time of molding, and the pressure gauge did not rise.
B: Unmelted material was observed during molding, but the pressure gauge did not rise.
C: Unmelted was observed at the time of molding, and the pressure gauge rose.

  And after heat-processing the obtained polyurethane sheet at 90 degreeC in nitrogen atmosphere for 5 hours, the polyurethane molded object of thickness 1.5mm was obtained by grinding the surface of a polyurethane sheet. Next, grooves having a width of 1.0 mm and a depth of 1.0 mm were spirally formed at intervals of 6.0 mm on the main surface to be a polished surface of a polyurethane molded product having a thickness of 1.5 mm. Then, the polyurethane molded body was cut into a circle having a diameter of 38 cm to obtain an abrasive layer. Then, a cushioning layer was attached to the back surface of the polishing layer with a double-sided pressure-sensitive adhesive sheet to prepare a multilayer polishing pad. As a cushion layer, "Poron H48" manufactured by Inoac Corporation, which is a polyurethane foam sheet having a thickness of 0.8 mm, was used. And the polishing characteristic of the obtained polishing pad was evaluated by the following evaluation method.

Flattening performance
A polishing pad was attached to a polishing plate of a polishing apparatus "BC-15" manufactured by M.A.T. Then, the surface of the polishing pad was conditioned for 30 minutes using a diamond dresser while flowing pure water at a speed of 150 mL / min under the conditions of a dresser rotational speed of 140 rpm, a polishing pad rotational speed of 100 rpm and a dresser load of 5N. As a dresser, a diamond count # 100 made by Allied Material Co., Ltd. and a base diameter of 190 mm were used.
Then, under the conditions of 100 rpm of polishing pad rotation speed, 99 rpm of wafer rotation speed, and 24 kPa of polishing pressure, 1900 mass of pure water in 100 mass parts of aqueous slurry ("GPL-C1010" manufactured by Showa Denko KK) containing cerium oxide abrasive grains. 50 mm in diameter with a pattern-free silicon oxide film (PETEOS silicon oxide film formed by plasma chemical vapor deposition) with an initial film thickness of 1000 nm while supplying a mixed solution by adding parts at a rate of 100 mL / min The silicon wafer was polished for 60 seconds without conditioning.

  Then, after conditioning for 30 seconds, a new wafer was replaced and polishing and conditioning were repeated again, and in the same manner, a total of 10 wafers were polished.

  Next, one SKW STI polishing evaluation pattern wafer “SKW3-2” having a concavo-convex pattern in which convex portions and concave portions were alternately and repeatedly arranged was polished under the same conditions as described above. The pattern wafer has areas of various patterns, and as a film thickness measurement target, an area (pattern 1) consisting of a pattern with a convex portion width of 100 μm and a concave portion width of 100 μm and only 4 mm square convex portions An area (pattern 2) and an area (pattern 3) consisting only of 4 mm square recesses were selected. This pattern 1 has an initial step difference of 550 nm between the projections and recesses, and the pattern projections are a silicon oxide film with a film thickness of 15 nm on a silicon wafer, a silicon nitride film with a film thickness of 140 nm, and a film thickness of 700 nm thereon. Is a laminated structure of a silicon oxide film (HDP silicon oxide film formed by high density plasma chemical vapor deposition), and the pattern concave portion is a groove formed by etching a silicon wafer to form an HDP silicon oxide film having a thickness of 700 nm. Structure. The pattern 2 consisting only of the convex portion has the same structure as the convex portion of the pattern 1, and the pattern 3 consisting only of the concave portion has the same structure as the concave portion of the pattern 1. The pattern wafer is polished for a time until the silicon oxide film laminated on the silicon nitride film of the convex portion of pattern 1 disappears, and the polishing amount of the convex portion of pattern 2 and the polishing amount of the concave portion of pattern 3 are Otsuka It measured using the electronic corporation | Co., Ltd. | KK product film thickness meter "FE-3300", respectively. Ratio of polishing amount of convex portions of pattern 2 to polishing amount of concave portions of pattern 3 (“polishing amount of silicon oxide film of convex portions of pattern 2” / “polishing amount of silicon oxide film of concave portions of pattern 3”) It was used as an indicator of flattening performance. As the value is larger, the convex portion is preferentially polished and indicates that the planarization performance is excellent.

Wear amount
A polishing pad was attached to a polishing plate of a polishing apparatus "BC-15" manufactured by M.A.T. Then, the surface of the polishing pad was conditioned for 2 hours using a diamond dresser while flowing pure water at a speed of 150 mL / min under the conditions of a dresser rotational speed of 140 rpm, a polishing pad rotational speed of 100 rpm and a dresser load of 5N. In addition, as a dresser, a diamond count # 100 made of Allied Material Co., Ltd., a diamond shape irregular type, and a base diameter of 190 mm were used. The depth of the groove before and after conditioning was measured at a point 100 mm from the center of the pad, and the amount of wear of the pad was measured.

  The results are shown in Table 1 below.

Example 2
Prepare a monomer mixture mixed in the ratio of HDO: HEMI: PEG 600: BD: MPD: MDI = 0.6: 0.8: 12.8: 14. 4: 7.9: 63.5 (mass ratio) did. Then, the monomer mixture is continuously supplied to a twin-screw extruder having a cylinder temperature of 75 to 260 ° C. in each zone by a metering pump and continuously melt polymerized while being kneaded, and is continuously discharged from the twin-screw extruder. The molten polyurethane strand was cooled in water and then cut with a pelletizer to obtain a thermoplastic polyurethane having a conjugated diene site and a dienophile site at the end. The nitrogen atom content derived from the isocyanate group calculated from the raw material compounding ratio was 7.1% by mass. Further, the molar ratio of the conjugated diene moiety to the dienophile moiety (the number of moles of conjugated diene moiety / the number of moles of dienophile moiety) contained in the polyurethane calculated from the raw material blending ratio is 1.08, and the polyurethane calculated from the raw material blending ratio The total amount of conjugated diene and dienophile sites contained therein was 0.118 mmol / g.
Then, using the obtained polyurethane, in the same manner as in Example 1, a polishing layer and a polishing pad comprising a polyurethane molded body were produced and evaluated in the same manner. The results are shown in Table 1.

[Examples 3 to 5]
A first polyurethane and a second polyurethane were produced in the same manner as in Example 1 except that the composition of the polymer composition of the polyurethane was changed to the composition shown in Table 1. Then, in the same manner as in Example 1, a polishing layer and a polishing pad made of a polyurethane molded body were prepared and evaluated in the same manner. The results are shown in Table 1.

[Example 6, Comparative Examples 1 to 6]
A polyurethane was produced in the same manner as Example 2, except that the composition of the polymer composition of the polyurethane was changed to the composition shown in Table 1. Then, in the same manner as in Example 1, a polishing layer and a polishing pad made of a polyurethane molded body were prepared and evaluated in the same manner. The results are shown in Table 1.

  From the results of Table 1, the following can be seen. Similar monomers except that the thermoplastic polyurethane obtained in Examples 1 and 2 using a monomer containing a conjugated diene site and a dienophile site and a monomer containing a conjugated diene site and a dienophile site are not used When the polyurethanes obtained in Comparative Examples 1 and 2 were compared with the polyurethanes obtained in Comparative Examples 1 and 2 of the composition, those excellent in formability, planarization performance and abrasion resistance were not obtained. In contrast, the polyurethanes obtained in Example 1 and Example 2 have excellent formability, planarization performance and abrasion resistance. It can be seen that similar results can be obtained by comparing Examples 3 and 4 with Comparative Examples 3 and 4, and Examples 5 and 6 with Comparative Examples 5 and 6.

[Example 7]
Core-sheath composite staple fiber (1.7 dtex, 51 mm long, core-sheath mass ratio = 60/40), wherein the core component is polyethylene terephthalate and the sheath component is modified polyethylene terephthalate (modified amount of isophthalic acid 32 mol%, melting point 140 ° C.) 21 crimps / 25 mm) were prepared. Using 100% by mass of the core-sheath type composite staple fiber, a carded web with a basis weight of about 2600 g / m ² was produced by the carding method. The carded web was needle-punched to obtain an entangled web having a basis weight of about 900 g / m ² , a thickness of about 3 mm, and an apparent density of 0.28 g / m ³ . Next, heat pressing was performed for 5 minutes under conditions of 135 ° C. and 20 MPa using a spacer of 1.5 mm in thickness to obtain an entangled nonwoven fabric densified to an apparent density of 0.55 g / m ³ .

  On the other hand, the pellets of the first polyurethane and the second polyurethane obtained in Example 1 are each dissolved in N, N-dimethylformamide so that the concentration of polyurethane becomes 18% by mass, and then the first polyurethane and The polyurethane solution was mixed such that the mass ratio of the second polyurethane was 1: 1. Then, the entangled nonwoven fabric obtained above is impregnated with a polyurethane solution adjusted to a temperature of 30 ° C., wet coagulated in a mixed solution of DMF and water at 40 ° C. (DMF concentration 30 mass%), then washed with water and dried. Thus, a sheet was obtained in which the polyurethane was applied to the inside of the nonwoven fabric. At this time, the amount of polyurethane per 100 g of entangled nonwoven fabric was 22 g. The impregnating property of the polyurethane solution at this time was evaluated by the following evaluation method.

<Impregnability>
A part of the sheet having polyurethane adhered to the inside of the non-woven fabric was cut out, and the cross section was observed with a scanning electron microscope. From the adhesion unevenness in the thickness direction and the adhesion amount of polyurethane, the impregnating property was evaluated by the following method.
A: When observed with an electron microscope, no difference was found in the amount of polyurethane between the surface layer and the inner layer, and the adhesion amount of polyurethane to 100 g of the entangled nonwoven fabric was 20 g or more.
B: No difference was observed in the amount of polyurethane between the surface layer and the inner layer when observed with an electron microscope, and the adhesion amount of polyurethane to 100 g of the entangled nonwoven fabric was 16 g or more.
C: When observed with an electron microscope, the amount of polyurethane in the inner layer was clearly smaller than that in the surface layer, or the amount of polyurethane attached to 100 g of the entangled nonwoven fabric was less than 16 g.

Next, the obtained sheet is heat-treated at 90 ° C. for 5 hours in a nitrogen atmosphere, then buffed with # 60 sandpaper to make the sheet thickness 1.2 mm, and then buffed with # 240 sandpaper The surface was adjusted to obtain a sheet for abrasive layer having an apparent density of 0.62 g / m ³ . The abrasion resistance of this abrasive layer sheet was evaluated by the following evaluation method.

<Abrasion resistance>
The Taber abrasion test was conducted according to JIS K6264 to measure the amount of abrasion. In addition, it measured on condition of wear ring | wheel: H-22, load: 4.9N, rotation speed 60rpm, and 500 times. The abrasion loss (mg), which is the difference between the mass before the abrasion test and the mass after the abrasion test, was determined.

  Then, after forming a grating groove having a groove width of 2.0 mm, a groove depth of 0.5 mm, and a pitch of 15 mm on the main surface to be a polishing surface of the polishing layer sheet, cut into a circle with a diameter of 38 cm to obtain a single layer type. The polishing pad of And the polishing characteristic of the obtained polishing pad was evaluated by the following evaluation method.

A polishing pad was attached to a polishing plate of a polishing apparatus "BC-15" manufactured by M.A.T. Then, under the conditions of 100 rpm of polishing pad rotation speed, 99 rpm of wafer rotation number, and 55 kPa of polishing pressure, 1900 mass parts of pure water with respect to 100 mass parts of polishing slurry ("Granzox 1302" manufactured by Fujimi Co., Ltd.) containing silicon oxide abrasive grains. The single crystal silicon wafer (density 2.33 g / cm ³ ) with a diameter of 100 mm was polished for 120 seconds while supplying the mixed solution with adding a portion at a rate of 200 mL / min. Then, the operation of replacing with a new silicon wafer and polishing again was repeated, and in the same manner, a total of 20 silicon wafers were polished. The polishing rate and the wafer surface roughness were measured for the twentieth polished silicon wafer.

Polishing speed
The mass of the wafer before and after polishing was measured, and the polishing rate was determined from the mass difference before and after polishing, and the area and density of the wafer.

<Wafer surface roughness>
Arithmetic mean roughness (Ra) and maximum height difference under the conditions of 2.5 times magnification and measuring range 2.8 mm × 2.1 mm using a white interference microscope “NewView 6000” manufactured by Zygo Co., Ltd. after polishing. (PV) was measured. The smaller the Ra, the better the smoothness, and the smaller the PV, the better the flatness.

  The results are shown in Table 2 below.

[Example 8]
In Example 7, instead of using a solution of the mixture of thermoplastic polyurethane (A) and polyurethane (B) obtained in Example 1, N, N- of the thermoplastic polyurethane (C) obtained in Example 2 is used. A sheet for polishing layer and a polishing pad were prepared and evaluated in the same manner as in Example 7 except that a dimethylformamide solution (the concentration of polyurethane was 18% by mass) was used. The results are shown in Table 2.

Comparative Examples 7 and 8
A sheet for polishing layer and a polishing pad were prepared and evaluated in the same manner as in Example 7 except that the composition of the monomer mixture of thermoplastic polyurethane to be impregnated into the non-woven fabric was changed to the composition shown in Table 2. The results are shown in Table 2.

  From the results of Table 2, the following can be seen. Examples 7 and 8 in which a thermoplastic polyurethane using a monomer containing a conjugated diene site and a dienophile site is impregnated in a non-woven fabric is similar to Examples 7 and 8 except that a monomer containing a conjugated diene site and a dienophile site is not used. Comparing Comparative Examples 7 and 8 in which the thermoplastic polyurethane of the monomer composition is impregnated into the non-woven fabric, Comparative Examples 7 and 8 are inferior in the impregnating property of the polyurethane to the non-woven fabric and also inferior in wear resistance and polishing rate. On the other hand, in Examples 7 and 8, all of the impregnatability, the abrasion resistance and the polishing rate were excellent.

  The polyurethane, the sheet for polishing layer and the polishing pad of the present invention are useful for polishing applications such as semiconductor substrates and glass. In particular, it is suitable for chemical mechanical polishing of substrate materials such as semiconductors, hard disks and liquid crystal displays, or optical parts such as lenses and mirrors.

DESCRIPTION OF SYMBOLS 1 Polishing pad 2 Rotating surface plate 3 Slurry supply nozzle 4 Carrier 5 Abrasive material 6 Pad conditioner 10 CMP apparatus

Claims (11)

  (A) A polyurethane containing a unit containing a conjugated diene moiety, a unit containing a dienophile moiety, a chain extender unit, a high molecular weight polyol unit and an organic polyisocyanate unit, or (b) a unit containing a conjugated diene moiety and a chain extender Mixture of a first polyurethane comprising units, a polymeric polyol unit and an organic polyisocyanate unit, and a second polyurethane comprising a unit comprising a dienophile site, a chain extender unit, a polymeric polyol unit and an organic polyisocyanate unit And at least one of them.   The polyurethane according to claim 1, wherein the unit comprising the conjugated diene moiety and the unit comprising the dienophile moiety are present at the end of each polyurethane main chain.   The polyurethane according to claim 1 or 2, wherein the unit containing the conjugated diene moiety contains at least one conjugated diene moiety selected from the group consisting of a 1,3-butadiene skeleton, a furan ring, and an imidazole ring.   The polyurethane according to any one of claims 1 to 3, wherein the unit containing the dienophile site comprises at least one dienophile site selected from the group consisting of a maleimide group, an acryloyl group, and a vinyl ketone group.   The polyurethane according to any one of claims 1 to 4, wherein the molar ratio of the unit containing the conjugated diene moiety to the unit containing the dienophile moiety (conjugated diene moiety / dienophile moiety) is 0.1 to 10.   The polyurethane according to any one of claims 1 to 5, wherein a total amount of the unit including the conjugated diene moiety and the unit including the dienophile moiety is 0.02 to 0.3 mmol / g.   The polyurethane according to any one of claims 1 to 6, wherein the content of the nitrogen atom derived from the organic polyisocyanate unit is 5 to 8% by mass.   The polyurethane according to any one of claims 1 to 7, which has a covalent bond formed by Diels-Alder reaction between the conjugated diene site and the dienophile site. A polishing pad comprising a polishing layer, wherein
The polishing pad comprises a polyurethane having a conjugated diene site and a dienophile site in one molecule, or a polyurethane having a conjugated diene site and a dienophile site in different molecules, respectively.   10. The polishing pad according to claim 9, wherein the polyurethane is a thermoplastic polyurethane, and the polishing layer is a molded article of the thermoplastic polyurethane.   The polishing pad according to claim 9, wherein the polishing layer comprises a non-woven fabric, and the polyurethane is contained inside the non-woven fabric.

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