JP2007246805A - Polishing pad and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively obtain a polishing pad that slightly causes scratch in polishing, has further excellent polishing uniformity, attains high flattening, is usable for an extremely long time and has a low metal content. <P>SOLUTION: The polishing pad has a polishing layer of foam structure comprising a copolymer composed of a structural unit derived from a urethane (meth)acrylate (A) and a structural unit derived from an ethylenic unsaturated monomer (B) except the urethane (meth)acrylate (A). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polishing pad having a foamed structure polishing layer containing a copolymer having a structural unit derived from urethane (meth) acrylate and a structural unit derived from an ethylenically unsaturated monomer, and a method for producing the same. . The polishing pad of the present invention is useful, for example, for polishing a silicon wafer, a semiconductor wafer or the like with high accuracy and high polishing efficiency.

  Conventionally, a polishing pad is used for mirror processing of a silicon wafer used as a substrate for forming an integrated circuit, or for flattening unevenness of an insulating film or a conductor film during manufacturing of a semiconductor device. It is used for chemical mechanical polishing (CMP). As such a polishing pad, a relatively soft polishing pad in which a polyurethane resin is impregnated with a polyurethane resin, a hard polishing pad made of foamed polyurethane, or two layers in which a soft polishing pad and a hard polishing pad are bonded together A structure pad or the like is used (see, for example, Patent Documents 1 to 3).

  In recent years, as semiconductor devices are highly integrated and multi-layered, there is an increasing demand for further improvements in quality and lower prices in semiconductor wafers, such as high flatness and less metal impurities. ing. Along with this, even for polishing pads used for manufacturing semiconductor wafers, higher leveling is possible than before, the metal content of the polishing pad itself is extremely low, and scratching during polishing There is a demand for extremely low occurrence, low use for a long time, and low cost.

  However, since the above-described conventional polishing pad is mainly composed of a polyurethane resin, the polishing characteristics of the polishing pad may change due to hydrolysis of urethane bonds when used for a long time. Usually, the polyurethane resin raw material is mixed with a kneader or an extruder to produce the polyurethane resin. However, in many cases, the inner surface is a metal, so that the metal may partially mix in the polyurethane resin. There is also. In order to prevent this metal contamination, measures such as coating the inside of a kneader or an extruder with a fluorine-based resin or the like can be considered. However, in this case, it is very expensive and there is a concern that the coated fluororesin or the like may be mixed into the polyurethane resin due to abrasion or peeling, which adversely affects the polishing characteristics.

  On the other hand, a polishing pad made of (meth) acrylic resin has also been proposed. For example, a polishing pad having a structure in which polymer microelements such as microhollow particles are dispersed in an acrylic resin is known (see Patent Document 4). Further, a polishing pad obtained by photocuring a specific photopolymer composition having a urethane bond is known (see Patent Document 5). Further, a polishing pad made of an acrylic resin having a specific acid value and hydroxyl value is known (see Patent Document 6). Furthermore, a polishing pad containing a polyurethane photopolymer resin obtained by curing a specific prepolymer, an ethylenically unsaturated monomer and a photopolymerization initiator is known (see Patent Document 7).

Japanese Patent Laid-Open No. 5-8178 JP 2000-178374 A JP 2001-89548 A Japanese Patent Application Laid-Open No. 2001-291685 JP 2003-45830 A JP 2005-166766 A US Pat. No. 5,965,460

  However, the polishing pad of the above-mentioned Patent Document 4 does not contain a soft component at all, or even if it contains only a small amount, the hardness of the polishing pad is very high, and scratches are likely to occur on the object to be polished. Particularly, in recent years, the miniaturization of wiring in a semiconductor device has progressed, and it is desired that even a fine scratch that has been allowed in the past is not generated as much as possible. A polishing pad that generates less is desired. Moreover, since the dispersion | distribution of the polymer microelement in an acrylic resin tends to become non-uniform | heterogenous in the polishing pad of patent document 4, hardness differs according to a place also in one polishing pad, and dispersion | variation in polishing performance tends to appear. There is also a problem.

  Moreover, since the polishing pad of the said patent document 5 and 6 is a non-segment structure which does not have a soft segment and a hard segment, when the glass transition temperature of resin which comprises a polishing pad is high, the hardness of a polishing pad becomes high too much. On the other hand, when the glass transition temperature is low, the polishing pad is inferior in heat resistance, so that the polishing pad is deformed by the temperature rise during polishing, and the polishing speed is within the surface of the polishing object. There is a problem that is likely to be uneven. Further, since the polishing pad of Patent Document 7 does not have a foamed structure, the polishing uniformity and the stability of the polishing rate are not satisfactory.

  In view of the above circumstances, the problem to be solved by the present invention is that the occurrence of scratches at the time of polishing is extremely low, the polishing uniformity is even better, higher leveling is possible, and it can be used for a long time, It is to provide a polishing pad with a low metal content at low cost.

  In order to solve the above-described problems, the present inventors have conducted intensive studies. As a result, a copolymer having a structural unit derived from urethane (meth) acrylate (A) and a structural unit derived from ethylenically unsaturated monomer (B) other than urethane (meth) acrylate (A) is obtained. The present inventors have found that a polishing pad having a polishing layer having a foam structure contained therein can solve the above-mentioned problems, and completed the present invention.

  [1] The present invention has a structural unit derived from urethane (meth) acrylate (A) and a structural unit derived from an ethylenically unsaturated monomer (B) other than urethane (meth) acrylate (A). A polishing pad having a foamed polishing layer containing a copolymer.

  [2] The present invention is the polishing pad according to [1], wherein the urethane (meth) acrylate (A) has a number average molecular weight of 1000 or more.

  [3] The present invention is the polishing pad according to [1] or [2], wherein the ethylenically unsaturated monomer (B) has an average molecular weight of 500 or less.

  [4] The present invention relates to a ratio of the mass of structural units derived from the urethane (meth) acrylate (A) and the mass of structural units derived from the ethylenically unsaturated monomer (B) in the copolymer. Is [mass of structural unit derived from urethane (meth) acrylate (A)] / [mass of structural unit derived from ethylenically unsaturated monomer (B)] = 20/80 to 60/40 [ The polishing pad according to any one of [1] to [3].

  [5] The present invention is obtained by reacting the urethane (meth) acrylate (A) with at least three components of a polyol (a1), an organic diisocyanate (a2), and a (meth) acrylic acid derivative (a3) having a hydroxyl group. The polishing pad according to any one of [1] to [4], which is a urethane (meth) acrylate.

  [6] The present invention is the polishing pad according to [5], wherein the polyol (a1) has a number average molecular weight of 500 to 5,000.

  [7] In the present invention, when the ethylenically unsaturated monomer (B) is a polymer composed only of the ethylenically unsaturated monomer (B), the glass transition temperature of the polymer is 60 ° C. or higher. ] To [6].

  [8] In the present invention, the ethylenically unsaturated monomer (B) is a (meth) acrylic acid derivative, or a mixture of a (meth) acrylic acid derivative and an ethylenically unsaturated monomer other than the (meth) acrylic acid derivative. The polishing pad according to any one of [1] to [7].

[9] The present invention is the polishing pad according to any one of [1] to [8], wherein the polishing layer has a density of 0.6 to 1.1 g / cm ³ .

  [10] The present invention is the polishing pad according to any one of [1] to [9], wherein an average diameter of bubbles constituting the foam structure of the polishing layer is 1 to 100 μm.

  [11] The invention according to any one of [1] to [10], wherein the foam structure of the polishing layer is formed by removing a volatile liquid dispersed in the copolymer. It is a polishing pad.

[12] The present invention is the polishing pad according to any one of [1] to [11], wherein the polishing layer has a dynamic elastic modulus at 50 ° C. of 9 × 10 ⁸ Pa or less.

[13] The present invention is the polishing pad according to any one of [1] to [12], wherein the polishing layer has a dynamic elastic modulus at 50 ° C. of 1 × 10 ⁸ Pa or more.

  [14] The present invention is the polishing pad according to any one of [1] to [13], wherein the main dispersion peak temperature of the polishing layer is 80 ° C. or higher.

  [15] The present invention includes a step of curing a mixture (S) containing urethane (meth) acrylate (A), an ethylenically unsaturated monomer (B) other than urethane (meth) acrylate (A), and a volatile liquid ( A method of manufacturing a polishing pad having a polishing layer having a foam structure, which includes a step 1) and a step of removing a volatile liquid (step 2).

  [16] The present invention is the production method according to [15], wherein the volatile liquid is water or a mixture containing water.

  [17] The present invention is the production method according to [16], wherein water or a mixture containing water is dispersed in the W / O type in the mixture (S).

  [18] The present invention is the production method according to any one of [15] to [17], wherein the mixture (S) further contains a dispersant.

  [19] The production method according to [18], wherein the dispersant is a copolymer of a (meth) acrylic acid alkyl ester and a polyoxyalkylene mono (meth) acrylate compound.

  [20] The present invention is a method for polishing a silicon wafer or a semiconductor wafer using the polishing pad according to any one of [1] to [14].

  [21] The present invention is a semiconductor device manufactured using the polishing pad according to any one of [1] to [14].

  According to the present invention, it is possible to provide a polishing pad that generates very little scratches during polishing, is more excellent in polishing uniformity, can be more highly planarized, and can be used for a considerably long time. Moreover, according to this invention, a polishing pad with little metal content can be provided at low cost. The polishing pad of the present invention is particularly useful for chemical mechanical polishing (CMP) and the like. Further, by polishing a silicon wafer or semiconductor wafer using the polishing pad of the present invention, the yield of the obtained silicon wafer or semiconductor wafer is improved, so that the silicon wafer, the semiconductor wafer, or a semiconductor formed from them can be obtained. It becomes possible to manufacture the device with high quality and low cost. Furthermore, according to the manufacturing method of the present invention, the polishing pad of the present invention can be easily manufactured.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the polishing pad of the present invention will be described in detail.
The polishing pad of the present invention has a polishing layer having a foam structure. The polishing layer has a structural unit derived from urethane (meth) acrylate (A) and a structural unit derived from an ethylenically unsaturated monomer (B) other than urethane (meth) acrylate (A). Contains a copolymer.

  Although the polishing pad of the present invention is not limited in any way, in the above copolymer, the structural unit derived from urethane (meth) acrylate (A) forms a soft segment, while the ethylenically unsaturated monomer The structural unit derived from (B) tends to form a hard segment. Therefore, the copolymer tends to have a segment structure having these soft segments and hard segments. A polishing pad having a polishing layer containing a copolymer having a segment structure has less scratching during polishing, and the polishing rate within the surface of the polishing object due to deformation of the polishing pad due to temperature rise during polishing It tends to be possible to suppress non-uniformity.

<About urethane (meth) acrylate (A)>
The urethane (meth) acrylate (A) used in the present invention is a compound containing one or more urethane bonds and (meth) acryloyl groups in one molecule. The position of the urethane bond or (meth) acryloyl group in the urethane (meth) acrylate (A) is not particularly limited, but it may have (meth) acryloyl groups at both ends of the urethane (meth) acrylate (A). Preferably, in this case, since the free copolymer does not have a free end in the obtained copolymer, a polishing pad with improved durability can be obtained.

  The urethane (meth) acrylate (A) used in the present invention is a urethane (meta) obtained by reacting at least three components of a polyol (a1), an organic diisocyanate (a2), and a (meth) acrylic acid derivative (a3) having a hydroxyl group. ) Acrylate is preferable because the desired urethane (meth) acrylate (A) can be easily produced.

  As polyol (a1) used for manufacture of urethane (meth) acrylate (A), a well-known polyol can be used, for example, polyether polyol, polyester polyol, polycarbonate polyol, polyester carbonate polyol, etc. are mentioned. These polyols (a1) may be used alone or in combination of two or more. Among these, it is preferable to use a polyether polyol. The number of hydroxyl groups per molecule of polyol (a1) is preferably 2.

  Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, poly (methyltetramethylene glycol), and glycerin-based polyalkylene ether glycol.

  As the above-mentioned polyester polyol, for example, according to a conventional method, an ester-forming derivative such as dicarboxylic acid or its ester or acid anhydride and a low molecular weight polyol are directly subjected to esterification reaction or transesterification reaction, or lactone is opened. It can be produced by ring polymerization.

  As the low-molecular polyol constituting the polyester polyol, those generally used in the production of polyester can be used. For example, ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3 -Propanediol, 2-methyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 2-methyl-1,4- Butanediol, neopentyl glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 2-methyl- 1,8-octanediol, 2,7-dimethyl-1,8-octanedioe Aliphatic diols such as 1,9-nonanediol, 2-methyl-1,9-nonanediol, 2,8-dimethyl-1,9-nonanediol, 1,10-decanediol; And alicyclic diols such as cyclohexanedimethanol and dimethylcyclooctanedimethanol; and aromatic dihydric alcohols such as 1,4-bis (β-hydroxyethoxy) benzene. These low molecular polyols may be used alone or in combination of two or more. Moreover, said low molecular polyol can contain a small amount of trimolecular or more low molecular polyol in the range which does not impair the effect of this invention. Examples of the trifunctional or higher functional low molecular polyol include trimethylolpropane, trimethylolethane, glycerin, 1,2,6-hexanetriol, and the like.

  As the dicarboxylic acid constituting the polyester polyol, those generally used in the production of polyester can be used. For example, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid Azelaic acid, sebacic acid, dodecanedioic acid, methylsuccinic acid, 2-methylglutaric acid, 3-methylglutaric acid, 2-methyladipic acid, 3-methyladipic acid, trimethyladipic acid, 2-methyloctanedioic acid, 3 Aliphatic dicarboxylic acids such as 1,8-dimethyldecanedioic acid and 3,7-dimethyldecanedioic acid; Alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; Aromatics such as terephthalic acid, isophthalic acid, orthophthalic acid, and naphthalenedicarboxylic acid List dicarboxylic acid or its ester-forming derivatives Door can be. These dicarboxylic acids may be used alone or in combination of two or more.

  Examples of the lactone include ε-caprolactone, δ-valerolactone, and β-methyl-δ-valerolactone.

  Specific polyester polyols include, for example, polybutylene adipate diol, polybutylene sebacate diol, polyhexamethylene adipate diol, poly (3-methyl-1,5-pentylene adipate) diol, and poly (3-methyl-1 , 5-pentylene sebacate) diol, polycaprolactone diol, and the like.

  As said polycarbonate polyol, what is obtained by reaction with carbonate compounds, such as a low molecular polyol and dialkyl carbonate, alkylene carbonate, diaryl carbonate, can be used, for example. As the low-molecular polyol constituting the polycarbonate polyol, the low-molecular polyol exemplified above as a constituent component of the polyester polyol can be used. Examples of the dialkyl carbonate include dimethyl carbonate and diethyl carbonate. Furthermore, examples of the alkylene carbonate include ethylene carbonate, and examples of the diaryl carbonate include diphenyl carbonate.

  Specific examples of the polycarbonate polyol include polyhexamethylene carbonate diol and poly (3-methyl-1,5-pentylene carbonate) diol.

  As the polyester carbonate polyol, for example, those obtained by simultaneously reacting a low molecular polyol, a dicarboxylic acid and a carbonate compound can be used. Alternatively, a polyester polyol and a polycarbonate polyol can be synthesized in advance by the method described above and then reacted with a carbonate compound, or obtained by reacting with a low molecular polyol and a dicarboxylic acid.

  Moreover, as a preferable polyol (a1) among the various polyols (a1) mentioned above, polytetramethylene glycol and poly (methyltetramethylene glycol) can be mentioned. In particular, polytetramethylene glycol is preferably used as the polyol (a1) because of excellent water resistance.

  In addition, the number average molecular weight of the polyol (a1) is preferably in the range of 500 to 5,000. In this case, the polyol (a1) can be easily obtained while providing an appropriate flexibility to the polishing pad. . When the number average molecular weight of the polyol (a1) is less than 500, the urethane group concentration in the urethane (meth) acrylate (A) becomes too high, and the resulting polishing pad is not flexible enough to cause many scratches during polishing. Tend to occur. On the other hand, when the number average molecular weight of the polyol (a1) is larger than 5,000, the production of the polyol (a1) tends to be difficult, or the viscosity becomes high and the handling tends to be difficult. A more preferable number average molecular weight of the polyol (a1) is 700 to 4500, and a more preferable number average molecular weight is 900 to 4000. In addition, the number average molecular weight of the polyol (a1) in this specification is a number average molecular weight calculated based on the hydroxyl value measured based on JIS K-1557.

  As the organic diisocyanate (a2) used in the production of the urethane (meth) acrylate (A), known organic diisocyanates can be used. For example, ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2 , 2,4- or 2,4,4-trimethylhexamethylene diisocyanate, dodecamethylene diisocyanate, isophorone diisocyanate, isopropylidenebis (4-cyclohexylisocyanate), cyclohexylmethane diisocyanate, methylcyclohexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate Bis (2-isocyanatoethyl) fumarate, bis (2-isocyanatoethyl) carbonate Aliphatic or alicyclic diisocyanates such as cyclohexylene diisocyanate, bis (2-isocyanatoethyl) -4-cyclohexene, norbornene diisocyanate; 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 Examples include aromatic diisocyanates such as -4,4'-diisocyanatobiphenyl, 3,3'-dimethyl-4,4'-diisocyanatodiphenylmethane, chlorophenylene-2,4-diisocyanate, and tetramethylxylylene diisocyanate. This Can be, can be used alone or two or more of them.

  Among these, it is preferable to use an organic diisocyanate having a large reactivity difference between two isocyanate groups such as isophorone diisocyanate and 2,4-tolylene diisocyanate. In this case, urethane (meth) acrylate (A ) Molecular weight distribution can be narrowed, derived from structural units derived from urethane (meth) acrylate (A) and structural units derived from ethylenically unsaturated monomer (B) in the polishing pad The segments to be separated can be appropriately phase separated.

  As the (meth) acrylic acid derivative (a3) having a hydroxyl group used in the production of the urethane (meth) acrylate (A), a known (meth) acrylic acid derivative having a hydroxyl group can be used. For example, (meth) Examples include 2-hydroxyethyl acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and the like. These (meth) acrylic acid derivatives (a3) having a hydroxyl group may be used alone or in combination of two or more. Among these, it is preferable to use 2-hydroxyethyl methacrylate or 4-hydroxybutyl methacrylate. In this case, spontaneous polymerization of the (meth) acrylic acid derivative due to heat can be suppressed, and Therefore, urethane (meth) acrylate (A) can be easily produced.

  Although it does not specifically limit as a manufacturing method of urethane (meth) acrylate (A), For example, polyol (a1) and organic diisocyanate (a2), Preferably [number of moles of polyol (a1)]: [Organic diisocyanate ( The number of moles of a2)] After reacting at a molar ratio of 1: 1.05 to 1: 2, a prepolymer having isocyanate groups at both ends was synthesized, and then the (meth) acrylic acid derivative having the prepolymer and a hydroxyl group was synthesized. A method of reacting with (a3) is preferred. When this method is used, the molecular weight distribution of urethane (meth) acrylate (A) can be narrowed, and segments derived from structural units derived from urethane (meth) acrylate (A) in the polishing pad (for example, The soft segment) and the segment derived from the structural unit derived from the ethylenically unsaturated monomer (B) (for example, a hard segment) can be appropriately phase-separated. The molar ratio of the polyol (a1) to the organic diisocyanate (a2) is more preferably [number of moles of polyol (a1)]: [number of moles of organic diisocyanate (a2)] = 1: 1.1 to 1: 1.8. Yes, and a more preferable molar ratio is [number of moles of polyol (a1)]: [number of moles of organic diisocyanate (a2)] = 1: 1.15 to 1.7.

In producing the urethane (meth) acrylate (A), a solvent may be used to reduce the viscosity. Examples of the solvent that can be used in this case include general organic solvents such as toluene, methyl ethyl ketone, ethyl acetate, tetrahydrofuran, N, N-dimethylformamide, and N-methylpyrrolidone. In addition, a part, all or excess of the ethylenically unsaturated monomer (B) used for obtaining the target copolymer should be used as a solvent for producing the urethane (meth) acrylate (A). You can also.
Further, when producing urethane (meth) acrylate (A), a catalyst (urethane reaction catalyst) for promoting urethanization reaction, (meth) acrylic acid derivative (a3) having a hydroxyl group or ethylenic acid A polymerization inhibitor or the like for preventing thermal polymerization of the saturated monomer (B) may be added.

Examples of the urethanization reaction catalyst include organotin compounds such as dibutyltin diacetate, dibutyltin dilaurate, dibutyltin bis (3-mercaptopropionic acid ethoxybutyl ester) salt; titanic acid; tetraisopropyl titanate, tetra-n-butyl. Organic titanium compounds such as titanate, polyhydroxytitanium stearate, titanium acetylacetonate; triethylenediamine, N-methylmorpholine, N, N, N ′, N′-tetramethylethylenediamine, N, N, N ′, N ′ -Tertiary amine compounds such as tetramethylhexamethylenediamine, triethylamine, N, N-dimethylaminoethanol, etc. can be mentioned, and one or more of these can be used.
The amount of the urethanization reaction catalyst used is 0.1 ppm to 2% by mass, more preferably 0.5 ppm to 0.2% by mass, and particularly 1 ppm to 0.00% based on the total mass of the polyol (a1) and the organic diisocyanate (a2). It is preferable to be in the range of 1% by mass. The urethanization reaction catalyst may be added at once, or may be added in a plurality of times.

  Examples of the polymerization inhibitor include a phenol polymerization inhibitor, a phosphorus polymerization inhibitor, an amine polymerization inhibitor, a sulfur polymerization inhibitor, a hydroquinone polymerization inhibitor, and a quinoline polymerization inhibitor. It is done.

  Examples of the phenol polymerization inhibitor include 2,4-di (octylthio) methyl-6-methylphenol [Irganox 1520 manufactured by Ciba Geigy Co., Ltd.], 2- (2-hydroxy-3-t-butyl). -5-methylbenzyl) -4-methyl-6-t-butylphenyl acrylate [Sumilyzer GM manufactured by Sumitomo Chemical Co., Ltd.], 2- [1- (2-hydroxy-3,5-di-t-pentylphenyl) ) Ethyl] -4,6-di (t-pentyl) phenyl acrylate [Sumilyzer GS manufactured by Sumitomo Chemical Co., Ltd.], bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionic acid ] -Triethylene glycol ester [Irganox 245 manufactured by Ciba Geigy Co., Ltd.], hydrazobis (3, -Di-t-butyl-4-hydroxy-hydrocinnamoyl) [Irganox MD-1024, manufactured by Ciba Geigy Co., Ltd.], N, N'-hexamethylenebis (3,5-di-t-butyl- 4-hydroxy-hydrocinnamamide) [Irganox 1098 manufactured by Ciba Geigy Co., Ltd.], 3,9-bis {1,1-dimethyl-2- [β- (3-t-butyl-4-hydroxy -5-methylphenyl) propionyloxy] ethyl} -2,4,8,10-tetraoxaspiro [5,5] undecane [Sumilyzer GA80 manufactured by Sumitomo Chemical Co., Ltd.], 1,3,5-trimethyl-2 , 4,6-Tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene [ADK STAB AO-330 manufactured by Asahi Denka Kogyo Co., Ltd.] , 3,5-Tris (3 ′, 5′-di-t-butyl-4′-hydroxybenzyl) -S-triazine-2,4,6- (1H, 3H, 5H) trione [ADK STAB AO-20 Asahi Manufactured by Denka Kogyo Co., Ltd.], tetrakis [methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] methane [Irganox 1010 Ciba Specialty Chemicals Co., Ltd. ) Made].

  Examples of the phosphorus polymerization inhibitor include tris (2,4-di-t-butylphenyl) phosphite [ADK STAB 2112 manufactured by Asahi Denka Kogyo Co., Ltd.], 2,2-methylenebis (4,6-di-t -Butylphenyl) octyl phosphite [Adeka Stub HP-10 manufactured by Asahi Denka Kogyo Co., Ltd.], cyclic neopentanetetraylbis (octadecyl) phosphite [Adekastab PEP-8 manufactured by Asahi Denka Kogyo Co., Ltd.], cyclic neo Pentanetetraylbis (2,4-di-t-butylphenyl) phosphite [ADK STAB PEP-24G manufactured by Asahi Denka Kogyo Co., Ltd.], cyclic neopentanetetraylbis (2,6-di-t-butyl- 4-methylphenyl) phosphite [ADK STAB PEP-36 manufactured by Asahi Denka Kogyo Co., Ltd.] and the like.

  Amine polymerization inhibitors include aromatic amines such as phenyl-1-naphthylamine, phenyl-2-naphthylamine, N, N′-diphenyl-1,4-phenylenediamine, N-phenyl-N′-cyclohexyl- Examples include 1,4-phenylenediamine.

  Examples of the sulfur polymerization inhibitor include dilauryl 3,3-thiodipropionate, di (tridecyl) 3,3-thiodipropionate, dimyristyl 2,2-thiodiacetate, dimyristyl 3,3-thiodipropioate. Lauryl stearyl 3,3-thiodipropionate, distearyl 3,3-thiodipropionate, 3,9-di (laurylthioethyl) -2,4,8,10-tetraoxaspiro [5,5 ] Undecane etc. are mentioned.

Examples of the hydroquinone polymerization inhibitor include 2,5-di-t-butylhydroquinone and 2,5-di-t-amylhydroquinone. Examples of the quinoline polymerization inhibitor include 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline.
A polymerization inhibitor may be used individually by 1 type, or may use 2 or more types together.

  The number average molecular weight of the urethane (meth) acrylate (A) used in the present invention is preferably 1000 or more. In this case, moderate flexibility can be given to the polishing pad, and generation of scratches during polishing can be suppressed. When the number average molecular weight of the urethane (meth) acrylate (A) is less than 1000, a segment derived from a structural unit derived from the urethane (meth) acrylate in the polishing pad (for example, a soft segment) and an ethylenically unsaturated monomer In some cases, phase separation from a segment derived from the structural unit derived from (B) (for example, a hard segment) is insufficient. As a result, either the flexibility or heat resistance of the polishing pad is insufficient, and many scratches may be generated during polishing or polishing uniformity may be reduced. Polishing pad with less scratching during polishing and excellent polishing uniformity can be obtained, and polishing with excellent mixing of urethane (meth) acrylate (A) and ethylenically unsaturated monomer (B) Since manufacture of a pad becomes easy, it is more preferable that the number average molecular weight of urethane (meth) acrylate (A) exists in the range of 1500-10000, It is further more preferable in the range of 2000-8500, 2500-7000 It is especially preferable that it is in the range.

  The number average molecular weight of the urethane (meth) acrylate (A) in the present specification is a calculated value obtained from the raw materials used in producing the urethane (meth) acrylate (A) and the amount used. For example, urethane (meth) acrylate (A) is urethane (meth) acrylate obtained by reacting three components of polyol (a1), organic diisocyanate (a2), and (meth) acrylic acid derivative (a3) having a hydroxyl group. In the case, the unit of polyol (a1) present in one molecule of urethane (meth) acrylate (A), organic diisocyanate (a2), assuming that all the hydroxyl groups and isocyanate groups present in these three components have reacted. And the number of units of the (meth) acrylic acid derivative (a3) having a hydroxyl group, the number average molecular weight of the polyol (a1), the molecular weight of the organic diisocyanate (a2), and the (meth) acrylic acid having a hydroxyl group From the molecular weight of the derivative (a3), the number of urethane (meth) acrylates (A) It can be determined average molecular weight.

  More specifically, the polyol (a1) and the organic diisocyanate (a2) whose number of hydroxyl groups per molecule is n are converted into [number of moles of polyol (a1)] / [mole of organic diisocyanate (a2). Number] = X / Y (where 2Y> nX) to synthesize a prepolymer having an isocyanate group at the end, and then the prepolymer and a (meth) acrylic acid derivative (a3) having one hydroxyl group. The urethane (meth) acrylate (A) is reacted by reacting such that the total number of hydroxyl groups in the (meth) acrylic acid derivative (a3) having a hydroxyl group is equal to or greater than the total number of all isocyanate groups of the prepolymer. In the case of production, the unit of the polyol (a1) existing in one molecule of the prepolymer is calculated as X / {Y- (n-1) X} units. The number of units of the organic diisocyanate (a2) present in the child Y / {Y- (n-1) X} pieces to be calculated. The number of terminal isocyanate groups present in one molecule of the prepolymer is calculated as (2Y-nX) / {Y- (n-1) X}. Therefore, the number average molecular weight of the urethane (meth) acrylate (A) obtained is expressed by the formula: [number average molecular weight of the polyol (a1)] × [X / {Y− (n−1) X}] + [organic diisocyanate ( Molecular weight of a2)] × [Y / {Y- (n-1) X}] + [Molecular weight of (meth) acrylic acid derivative (a3) having a hydroxyl group] × [(2Y-nX) / {Y- (n -1) X}].

  In addition, as described above, the urethane (meth) acrylate (A) used reacts at least three components of the polyol (a1), the organic diisocyanate (a2), and the (meth) acrylic acid derivative (a3) having a hydroxyl group. When it is obtained, the proportion of the segment derived from the polyol (a1) in the urethane (meth) acrylate (A) is preferably in the range of 70 to 90% by mass. Appropriate flexibility can be provided, and the generation of scratches during polishing can be suppressed. When the ratio of the segment derived from the polyol (a1) is less than 70% by mass, the polishing pad is not flexible enough to tend to cause scratching during polishing. On the other hand, when the ratio of the segment derived from the polyol (a1) exceeds 90% by mass, the number average molecular weight of the urethane (meth) acrylate (A) becomes too large, so that the urethane (meth) acrylate (A) and the ethylenic group It tends to be difficult to uniformly mix the unsaturated monomer (B). The proportion of the segment derived from the polyol (a1) in the urethane (meth) acrylate (A) is more preferably in the range of 72 to 88% by mass, and further preferably in the range of 74 to 86% by mass. In addition, the ratio of the segment derived from the polyol (a1) in the urethane (meth) acrylate (A) in this specification is the total of the used polyol (a1) with respect to the total mass of the urethane (meth) acrylate (A). Equal to mass percentage.

<About ethylenically unsaturated monomer (B)>
The ethylenically unsaturated monomer (B) used in the present invention is a compound other than urethane (meth) acrylate (A) having an ethylenically unsaturated bond in the molecule. The average molecular weight of the ethylenically unsaturated monomer (B) is preferably 500 or less. If the average molecular weight of the ethylenically unsaturated monomer (B) is greater than 500, the glass transition temperature of the polymer consisting only of the ethylenically unsaturated monomer (B) becomes too low, and the heat resistance of the polishing pad is lowered, resulting in uniform polishing. Tend to decrease. A more preferable average molecular weight of the ethylenically unsaturated monomer (B) is 400 or less, a further preferable average molecular weight is 30 to 350, and a particularly preferable average molecular weight is 50 to 300. The average molecular weight of the ethylenically unsaturated monomer (B) means the molecular weight of the monomer when the ethylenically unsaturated monomer (B) is composed of one type of monomer. ) Is composed of a plurality of types, it means the sum of products of the molecular weight of each monomer and the molar fraction of each monomer in the whole ethylenically unsaturated monomer (B).

  As the ethylenically unsaturated monomer (B) used in the present invention, a known ethylenically unsaturated monomer can be used. For example, other than (meth) acrylic acid derivative (b1) and (meth) acrylic acid derivative (b1) One or more ethylenically unsaturated monomers (b2) (hereinafter sometimes simply referred to as “other ethylenically unsaturated monomers (b2)”) may be used. The saturated monomer (B) may be a (meth) acrylic acid derivative (b1) alone or a mixture of the (meth) acrylic acid derivative (b1) and another ethylenically unsaturated monomer (b2). preferable.

  As the (meth) acrylic acid derivative (b1), known (meth) acrylic acid derivatives can be used. For example, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, (Meth) acrylic acid 2-ethylhexyl, (meth) acrylic acid lauryl, (meth) acrylic acid stearyl, (meth) acrylic acid cyclohexyl, (meth) acrylic acid isobornyl, (meth) acrylic acid dicyclopentanyl, (meth) Benzyl acrylate, (meth) acrylic acid, glycidyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (meth) acrylic acid 2 -Hydroxypropyl, 4-hydroxybutyl (meth) acrylate, etc. Functional (meth) acrylic acid derivatives; ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, 1,4-butanediol di ( (Meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, 2-methyl-1,8-octanediol di (meth) acrylate, neopentyl glycol di (meth) ) Bifunctional (meth) acrylic acid derivatives such as acrylate, dimethylol tricyclodecane di (meth) acrylate, glycerin di (meth) acrylate, allyl (meth) acrylate, vinyl (meth) acrylate; trimethylol proppant Examples include trifunctional (meth) acrylic acid derivatives such as (meth) acrylate and pentaerythritol tri (meth) acrylate; tetrafunctional (meth) acrylic acid derivatives such as pentaerythritol tetra (meth) acrylate and the like. , One or more of these can be used.

  Of the various (meth) acrylic acid derivatives (b1) described above, preferred (meth) acrylic acid derivatives (b1) are methyl methacrylate, ethyl methacrylate, 2-hydroxyethyl methacrylate, methacrylic acid, and ethyl acrylate. More preferred (meth) acrylic acid derivatives (b1) are methyl methacrylate, 2-hydroxyethyl methacrylate, and ethyl acrylate.

  On the other hand, as the other ethylenically unsaturated monomer (b2), known ethylenically unsaturated monomers can be used. For example, monofunctional aromatics such as styrene, α-methylstyrene, and p-methylstyrene are used. Vinyl compounds; amides of unsaturated carboxylic acids such as (meth) acrylamide and diacetone (meth) acrylamide; maleic acid, fumaric acid, itaconic acid or derivatives thereof; heterocyclic vinyl compounds such as vinylpyrrolidone; vinyl chloride; Examples include vinyl compounds such as acrylonitrile, vinyl ether, vinyl ketone, and vinyl amide; α-olefins such as ethylene and propylene; and polyfunctional aromatic vinyl compounds such as divinylbenzene and trivinylbenzene. Or by using two or more wear.

  As a ratio of the (meth) acrylic acid derivative (b1) and the other ethylenically unsaturated monomer (b2) in the ethylenically unsaturated monomer (B), the (meth) acrylic acid derivative (b1) is 50 to 100% by mass, It is preferable that it consists of other ethylenically unsaturated monomer (b2) 50-0 mass%, and in this case, manufacture of a polishing pad can be made easy and the outstanding polishing performance can be provided. The ratio is more preferably 40 to 0% by mass of the other ethylenically unsaturated monomer (b2) with respect to 60 to 100% by mass of the (meth) acrylic acid derivative (b1), and further preferably (meth) acrylic acid. The other ethylenically unsaturated monomer (b2) is 30 to 0% by mass relative to 70 to 100% by mass of the derivative (b1).

  In the present invention, it is particularly preferable that 50 to 100% by mass of the ethylenically unsaturated monomer (B) is composed of methyl methacrylate. In this case, the heat resistance of the polishing pad and the wettability to the polishing slurry are excellent. Therefore, the uniformity during polishing can be improved, and the occurrence of scratches can be significantly suppressed. More preferably, 60 to 100% by mass of the ethylenically unsaturated monomer (B) is composed of methyl methacrylate, and more preferably 70 to 100% by mass of the ethylenically unsaturated monomer (B) is methacrylic acid. This is the case when it is composed of methyl.

  The average number of ethylenic double bonds per molecule of the ethylenically unsaturated monomer (B) (hereinafter sometimes simply referred to as “average functional group number”) is preferably 1 to 1.5. . If the average number of functional groups is larger than 1.5, the crosslinking density in the copolymer containing urethane (meth) acrylate (A) and ethylenically unsaturated monomer (B) becomes too high, and the flexibility of the polishing pad is increased. There is a tendency that scratches at the time of polishing tend to occur due to shortage. The average functional group number of the ethylenically unsaturated monomer (B) is more preferably 1 to 1.4, and still more preferably the average functional group number is 1 to 1.3.

  Further, the ethylenically unsaturated monomer (B) preferably has a glass transition temperature of 60 ° C. or higher when the polymer is composed of only the ethylenically unsaturated monomer (B). The heat resistance of the polishing pad can be made excellent, and the polishing uniformity can be made better. When the polymer is composed of only ethylenically unsaturated monomer (B), the glass transition temperature of the polymer is more preferably 70 ° C or higher, and further preferably 80 ° C or higher.

In addition, when the ethylenically unsaturated monomer (B) is a polymer composed only of the ethylenically unsaturated monomer (B), the glass transition temperature of the polymer is “Polymer Data Handbook (Basics)” published by Baifukan Co., Ltd. "John Wiley & Sons, Inc." Values described in publications such as “POLYMER HANDBOOK FOURTH EDITION” issued by the company can be used. In addition, when using 2 or more types of ethylenically unsaturated monomers (B), the mass fraction of each monomer occupying the whole ethylenically unsaturated monomer (B) is determined by the homopolymer of each monomer component described above. The reciprocal of the sum of the values divided by the glass transition temperature (unit: K), that is, the value calculated by the following equation (1) can be used.
1 / Tg _t = w ₁ / Tg ₁ + w ₂ / Tg ₂ +... + W _i / Tg _i (1)
(However, Tg _t : Glass transition temperature (unit: K) of the polymer consisting only of ethylenically unsaturated monomer (B), w ₁ , w ₂ ,..., W _i : ethylene used in the copolymer , Tg ₁ , Tg ₂ ,..., Tg _i : each monomer component constituting the polymer composed only of the ethylenically unsaturated monomer (B) alone Glass transition temperature of polymer (unit: K))
It can also be obtained by separately synthesizing a polymer consisting only of the ethylenically unsaturated monomer (B) and measuring with a DSC (differential scanning calorimeter) or TMA (thermomechanical measuring device).

  The mass of structural units derived from urethane (meth) acrylate (A) and the mass of structural units derived from ethylenically unsaturated monomer (B) in the copolymer constituting the polishing layer of the polishing pad of the present invention. The ratio is [mass of structural unit derived from urethane (meth) acrylate (A)] / [mass of structural unit derived from ethylenically unsaturated monomer (B)] = 20/80 to 60/40. It is preferable that it exists in. When the mass ratio is smaller than 20/80 (when there are fewer structural units derived from urethane (meth) acrylate (A)), it is derived from urethane (meth) acrylate (A) in the polishing layer. There is a tendency that the content of segments derived from structural units (for example, soft segments) becomes too small, and the polishing pad is not flexible enough to cause scratches during polishing. On the other hand, when the mass ratio is larger than 60/40 (when there are more structural units derived from urethane (meth) acrylate (A)), the heat resistance of the polishing pad is insufficient, and polishing uniformity and polishing are reduced. There is a tendency for speed stability to decrease. A more preferred ratio of the mass of the structural unit derived from the urethane (meth) acrylate (A) and the mass of the structural unit derived from the ethylenically unsaturated monomer (B) is [from urethane (meth) acrylate (A) Mass of derived structural unit] / [Mass of structural unit derived from ethylenically unsaturated monomer (B)] = 25/75 to 50/50, and a more preferable ratio is [urethane (meth) The mass of the structural unit derived from the acrylate (A)] / [the mass of the structural unit derived from the ethylenically unsaturated monomer (B)] = 30/70 to 45/55.

  The copolymer used in the polishing pad of the present invention is not limited to the structural unit derived from the urethane (meth) acrylate (A) and the structural unit derived from the ethylenically unsaturated monomer (B). In the range which does not impair the effect of, the structural unit derived from the other copolymerizable monomer (C) may be contained. The monomer (C) is preferably a monomer species that does not inhibit the copolymerization reaction between the urethane (meth) acrylate (A) and the ethylenically unsaturated monomer (B). The monomer (C) is a structural unit derived from the urethane (meth) acrylate (A) and a structure derived from the ethylenically unsaturated monomer (B) even after the structural unit constituting the copolymer is formed. Monomer species that do not inhibit the physical properties of the unit are preferred. Such monomers include, for example, functional groups that do not have an ethylenically unsaturated bond and are reactive with ethylenically unsaturated monomers (for example, carbon-carbon triple bonds, hydroxyl groups, amino groups, carboxyl groups, and derivatives thereof) , A carbonyl group, a hydrosilyl group, a halogen atom, etc.). The content of the structural unit derived from the monomer (C) varies depending on the chemical characteristics of the monomer (C), but is suppressed to, for example, 0 to 30% by mass with respect to the total mass of the copolymer. Is preferable, it is more preferable to suppress to 0-5 mass%, and it is further more preferable to suppress to 0-1 mass%. That is, the total ratio of the mass of the structural unit derived from the urethane (meth) acrylate (A) and the mass of the structural unit derived from the ethylenically unsaturated monomer (B) in the copolymer is 100 to 70. It is preferably in the range of mass%, more preferably in the range of 100 to 95 mass%, further preferably in the range of 100 to 99 mass%. As a particularly preferred embodiment, the copolymer consists of a structural unit derived from urethane (meth) acrylate (A) and a structural unit derived from ethylenically unsaturated monomer (B).

  The polishing pad of the present invention has a polishing layer containing the above copolymer. Although the content rate of the copolymer in a grinding | polishing layer is not specifically limited, It is preferable to contain 80-100 mass% of copolymers with respect to the total mass of a grinding | polishing layer, and it contains 90-100 mass%. It is more preferable, and it is more preferable to contain 94-100 mass%. The polishing layer may be composed only of the above copolymer. The term “polishing layer” as used herein means a layer constituting the polishing surface of the polishing pad.

  The polishing layer may contain components other than the above copolymer. Examples of such other components include resins, pigments, dyes, antifouling agents, antifungal agents, cross-linking agents, fillers, cross-linking accelerators, cross-linking aids, softening agents, and adhesives other than the above-mentioned copolymers. Imparting agent, anti-aging agent, foaming agent, processing aid, adhesion imparting agent, inorganic filler, organic filler, crystal nucleating agent, heat stabilizer, weathering stabilizer, antistatic agent, colorant, lubricant, flame retardant, Examples include flame retardant aids (such as antimony oxide), blooming inhibitors, mold release agents, thickeners, antioxidants, ultraviolet absorbers, and conductive agents.

  The polishing layer has a foam structure. When the polishing layer has a foam structure, a recess for holding the polishing slurry is easily formed on the surface of the polishing pad, and the polishing uniformity and polishing rate are improved compared to the case where the polishing layer does not have a foam structure. To withstand long-term use. The foam structure is preferably a closed cell structure.

The density of the polishing layer is preferably in the range of 0.6 to 1.1 g / cm ³ . When the density of the polishing layer exceeds 1.1 g / cm ³ , the recess for holding the polishing slurry is not sufficiently formed on the surface of the polishing layer, and the improvement effect such as polishing uniformity and polishing rate is insufficient. Tend to be. On the other hand, when the density of the polishing layer is less than 0.6 g / cm ³ , it is difficult to produce the polishing pad, and the wear rate of the polishing layer itself is increased, and the service life tends to be shortened. The density of the polishing layer is more preferably in the range of 0.7~1.05g / cm ^3, and still more preferably in the range of 0.8~1.0g / cm ^3. The density of the polishing layer is a value measured according to JIS K-7112.

  The average diameter of the bubbles constituting the foam structure of the polishing layer is preferably in the range of 1 to 100 μm. When the average diameter is in this range, the size of the recess for holding the polishing slurry formed on the polishing layer surface can be made desired. On the other hand, when the average diameter is less than 1 μm, it becomes difficult to ensure a sufficient size compared to the size of the abrasive grains in the polishing slurry liquid, the holding capacity of the polishing slurry is lowered, and polishing uniformity and polishing are reduced. There is a tendency for speed to be insufficient. When the average diameter exceeds 100 μm, the interval between the bubbles becomes too wide, the variation in the polishing rate per unit area of the polishing pad increases, and the polishing uniformity tends to be insufficient. The average diameter is more preferably in the range of 5 to 90 μm, and still more preferably in the range of 10 to 80 μm. The average diameter of the bubbles in the polishing layer will be described in detail in the items of the following examples. The number of bubbles per unit area is obtained by taking a photograph of a cross section of the polishing layer with a scanning electron microscope (SEM). The (bubble number density) is calculated, and from the value, the density of the polishing layer, and the density of the non-foamed material separately produced, it means the diameter when the bubbles are assumed to be true spherical.

  The foamed structure of the polishing layer may be formed in any manner, and examples thereof include a method of forming by foaming with supercritical gas, blending of fine hollow particles, removal of volatile liquid, and the like. Among these, since the foam structure can be uniformly formed and the density and bubble diameter of the polishing layer can be easily controlled, the foam structure removes the volatile liquid dispersed in the copolymer. It is preferable that it is formed by this. A specific method for removing the volatile liquid includes a method for volatilizing the volatile liquid. In this case, the present invention is not limited in any way, but it is assumed that the volatile liquid diffuses into the material constituting the polishing layer (such as the copolymer and other components) and then volatilizes. Is done.

The dynamic elastic modulus at 50 ° C. of the polishing layer is preferably 9 × 10 ⁸ Pa or less. In this case, moderate flexibility can be imparted to the polishing pad, and the generation of scratches during polishing can be more effectively suppressed. The dynamic elastic modulus at 50 ° C. is more preferably 8 × 10 ⁸ Pa or less, and the dynamic elastic modulus at 50 ° C. is more preferably 7 × 10 ⁸ Pa or less.
On the other hand, if the polishing pad is too flexible, the polishing pad tends to be excessively deformed during polishing, and the polishing uniformity tends to decrease. For this reason, the dynamic elastic modulus at 50 ° C. of the polishing layer is preferably 1 × 10 ⁸ Pa or more, more preferably 2 × 10 ⁸ Pa or more, and 3 × 10 ⁸ Pa or more. Further preferred.
Such a polishing layer having a dynamic elastic modulus at 50 ° C. is, for example, a segment derived from a structural unit derived from urethane (meth) acrylate (A) in a copolymer contained in the polishing layer (for example, soft Segment) and a segment derived from a structural unit derived from the ethylenically unsaturated monomer (B) (for example, a hard segment) can be obtained by appropriate phase separation. In addition, the dynamic elastic modulus at 50 ° C. of the polishing layer in the present specification is a value measured by a viscoelasticity measuring device, as described in detail in the items of the examples.

  The temperature of the main dispersion peak of the polishing layer is preferably 80 ° C. or higher. In this case, the heat resistance of the polishing pad can be made excellent, and the polishing uniformity can be made better. A more preferable main dispersion peak temperature is 90 ° C. or higher, and a more preferable main dispersion peak temperature is 100 ° C. or higher. The polishing layer having such a main dispersion peak temperature is, for example, a segment derived from a structural unit derived from urethane (meth) acrylate (A) in a copolymer contained in the polishing layer (for example, a soft segment). And a segment derived from a structural unit derived from the ethylenically unsaturated monomer (B) (for example, a hard segment) can be obtained by appropriate phase separation. In addition, the temperature of the peak of the main dispersion of the polishing layer in the present specification is a value measured by a viscoelasticity measuring device as described in detail in the items of the examples.

  The contact angle of the polishing layer with water is preferably 90 degrees or less. In this case, the wettability of the polishing pad to the polishing slurry can be improved, and the generation of scratches during polishing can be more effectively suppressed. A more preferable contact angle with water is 88 degrees or less, and a more preferable contact angle with water is 86 degrees or less. In addition, the contact angle with water of the polishing layer in this specification is a value measured by the method described in detail in the items of the examples.

  The water absorption after the polishing layer is immersed in 50 ° C. water for 3 days is preferably less than 10% by mass. In this case, it is possible to reduce the change with time of the polishing pad hardness due to water absorption during polishing and to improve the stability of the polishing performance. More preferable water absorption is 8% by mass or less, and further preferable water absorption is 6% by mass or less. Moreover, about the lower limit of this water absorption, what is necessary is just a water absorption which can maintain the effect of this invention, Preferably it is 0.3 mass%, More preferably, it is 0.5 mass%. In addition, the water absorption rate of the polishing layer in this specification after being immersed in water at 50 ° C. for 3 days is a value measured by the method described in detail in the items of the examples.

  Although there is no restriction | limiting in particular in the manufacturing method of the polishing pad of this invention, At least 3 component of ethylenically unsaturated monomer (B) other than urethane (meth) acrylate (A) and urethane (meth) acrylate (A), and a volatile liquid It is preferable to include the process (process 1) of hardening the mixture (S) containing, and the process (process 2) of removing a volatile liquid.

  The mixture (S) contains at least three components of urethane (meth) acrylate (A), ethylenically unsaturated monomer (B) other than urethane (meth) acrylate (A), and volatile liquid. By the curing in Step 1, the urethane (meth) acrylate (A) and the ethylenically unsaturated monomer (B) other than the urethane (meth) acrylate (A) form a copolymer. The volatile liquid preferably forms a dispersed phase in the copolymer.

  The proportion of the urethane (meth) acrylate (A) in the mixture (S) and the ethylenically unsaturated monomer (B) other than the urethane (meth) acrylate (A) is appropriately selected according to the desired copolymer. Although adjusted, [mass of urethane (meth) acrylate (A)] / [mass of ethylenically unsaturated monomer (B)] is preferably in the range of 20/80 to 60/40, 25/75 to It is more preferably in the range of 50/50, and further preferably in the range of 30/70 to 45/55.

The volatile liquid means a liquid having volatility. The volatile liquid preferably has a boiling point in the range of 20 to 200 ° C. at atmospheric pressure (1 atm), more preferably in the range of 50 to 150 ° C. Examples of the volatile liquid include water; alcohols such as methanol, ethanol, and propanol; ketones such as acetone, 2-butanone, methyl isopropyl ketone, and methyl-isobutyl ketone; N, N-dimethylformamide, and N, N-dimethylacetamide. Amides such as N-methylpyrrolidinone; sulfoxides such as dimethyl sulfoxide; esters such as ethyl acetate and butyl acetate; ethers such as diethyl ether, diisopropyl ether and tetrahydrofuran; hydrocarbons such as pentane, hexane, octane, benzene, toluene and xylene A halogen compound such as methylene chloride, chloroform, carbon tetrachloride and the like, and one of them can be used alone or two or more of them can be used in combination. Among these, there is almost no volatilization in Step 1, and removal of volatilization etc. is easy in Step 2, and it is easy to form a dispersed phase in the mixture (S), and also has an influence on the environment and the human body. Since it is small, water or a mixture containing water is preferable, and water is more preferable. When water or a mixture containing water is used as the volatile liquid, it is preferable that water or a mixture containing water is dispersed in the W / O type (water-in-oil type) in the mixture (S).
The amount of the volatile liquid in the mixture (S) can be appropriately adjusted according to the desired density of the polishing layer, but urethane (meth) acrylate (A) and ethylenically unsaturated monomer (B ) Is preferably in the range of 5 to 90 parts by mass, more preferably in the range of 10 to 70 parts by mass, and still more preferably in the range of 15 to 50 parts by mass. .

The mixture (S) preferably contains a dispersant. By containing the dispersant, the volatile liquid can be easily dispersed in the mixture (S), and a polishing layer having a uniform bubble size and distribution can be obtained with good reproducibility.
Although the usage-amount of a dispersing agent can be suitably selected with the kind, usage-amount, etc. of a volatile liquid, with respect to a total of 100 mass parts of urethane (meth) acrylate (A) and an ethylenically unsaturated monomer (B). , Preferably in the range of 0.01 to 10 parts by mass, more preferably in the range of 0.05 to 8 parts by mass, and still more preferably in the range of 0.1 to 6 parts by mass.

The dispersant is appropriately selected depending on the type of volatile liquid to be used, and for example, a polymer having one or more segments having different polarities is used. In particular, when water or a mixture containing water is used as the volatile liquid, a dispersant having the ability to stably disperse W / O type (water-in-oil type) in the mixture (S) is used. It is preferable. Examples of the dispersant include a polymer having a hydrophilic component and a hydrophobic component in the same molecule, and an emulsifier. Among these, since the dispersion of volatile liquid such as water or a mixture containing water can be stably maintained during the curing of the mixture (S) and the influence on the polishing characteristics of the resulting polishing pad is small, the dispersant Is preferably a polymer of an ethylenically unsaturated monomer having a hydrophilic group. Examples of the hydrophilic group in the dispersant include a polyoxyalkylene group such as a polyoxyethylene group, a hydroxyl group, a carboxyl group, an amino group, etc., but it is particularly excellent in dispersion stability of water and the like, and has an influence on polishing characteristics. A polyoxyalkylene group is preferred because it is extremely small and the production of the dispersant is easy. In particular, when the dispersant is a copolymer of a (meth) acrylic acid alkyl ester and a polyoxyalkylene mono (meth) acrylate compound, it is easy to produce the dispersant itself, and water in the mixture (S) Or it is further more preferable from the further excellent dispersibility of volatile liquids, such as a mixture containing water. In addition, a dispersing agent may be used individually by 1 type, or may use 2 or more types together.
The polyoxyalkylene mono (meth) acrylate compound is a general term for compounds in which only one of the terminal hydroxyl groups of the polyoxyalkylene compound is replaced with a (meth) acryloyloxy group, and the (meth) acryloyloxy There is no particular limitation on the structure of the terminal opposite to the terminal having a group.

  The copolymer of the (meth) acrylic acid alkyl ester and the polyoxyalkylene mono (meth) acrylate compound is obtained by copolymerizing the (meth) acrylic acid alkyl ester and the polyoxyalkylene mono (meth) acrylate compound. be able to. In the copolymer of (meth) acrylic acid alkyl ester and polyoxyalkylene mono (meth) acrylate compound, the mass of the structural unit derived from (meth) acrylic acid alkyl ester, and from the polyoxyalkylene mono (meth) acrylate compound The ratio of the derived structural unit to the mass is preferably particularly excellent in the ability to stably disperse water or a mixture containing water into the W / O type (water-in-oil type) in the mixture (S). , [Mass of structural unit derived from (meth) acrylic acid alkyl ester] / [mass of structural unit derived from polyoxyalkylene mono (meth) acrylate compound] = 20/80 to 70/30, and more Preferably it is 30 / 70-60 / 40.

  Examples of the (meth) acrylic acid alkyl ester include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, ( Stearyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, benzyl (meth) acrylate, glycidyl (meth) acrylate, dimethyl (meth) acrylate Monofunctional (meth) acrylic such as aminoethyl, diethylaminoethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate Acid derivative; ethylene glycol di (meth) acrylate Diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, 2-methyl-1,8-octanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, dimethylol tricyclodecane di (meth) acrylate, glycerin di Bifunctional (meth) acrylic acid derivatives such as (meth) acrylate, allyl (meth) acrylate, vinyl (meth) acrylate; trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, etc. May be used alone or two or more of such tetrafunctional (meth) acrylic acid derivatives such as pentaerythritol tetra (meth) acrylate; trifunctional (meth) acrylic acid derivative. Among these, since the production of the dispersant is easy, and water or a mixture containing water is stably dispersed in the W / O type (water-in-oil type) in the mixture (S), Monofunctional (such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate A meth) acrylic acid derivative is preferred.

On the other hand, specific examples of the polyoxyalkylene mono (meth) acrylate compound include, for example, polyoxyethylene methyl ether (meth) acrylate [H ₂ C═CR—CO ₂ (CH ₂ CH ₂ O) _n CH _3. Compound; provided that R represents a hydrogen atom or a methyl group, n represents an integer, polyoxyethylene ethyl ether (meth) acrylate [H ₂ C═CR—CO ₂ (CH ₂ CH ₂ O) _n CH ₂ CH A compound represented by ₃ ; wherein R represents a hydrogen atom or a methyl group, and n represents an integer], and the like; a polyoxyethylene alkyl ether (meth) acrylate; a polyoxyethylene aryl ether (meth) acrylate; a polyoxyethylene aralkyl Ether (meth) acrylate; polyoxyethylene (meth) acrylate [Compound represented by _{H 2 C = CR-CO 2} (CH 2 CH 2 O) n H; where, R represents a hydrogen atom or a methyl radical, n is an integer]; polyoxypropylene alkyl ether (meth) Polyoxypropylene aryl ether (meth) acrylate; polyoxypropylene aralkyl ether (meth) acrylate; polyoxypropylene (meth) acrylate; polyoxybutylene alkyl ether (meth) acrylate; polyoxybutylene aryl ether (meth) acrylate; Examples thereof include polyoxybutylene aralkyl ether (meth) acrylate; polyoxybutylene (meth) acrylate. A polyoxyalkylene mono (meth) acrylate compound may be used individually by 1 type, or may use 2 or more types together. Of these, polyoxyethylene alkyl ether (meth) acrylate is preferable, and polyoxyethylene methyl ether (meth) acrylate is more preferable because it is easily available and a dispersant can be easily manufactured. In addition, as a number average repeating number of the oxyethylene unit in the polyoxyethylene group which a polyoxyalkylene mono (meth) acrylate compound has, Preferably it is the range of 3-150, More preferably, it is the range of 4-120. .

  The number average molecular weight of the copolymer of the (meth) acrylic acid alkyl ester and the polyoxyalkylene mono (meth) acrylate compound is excellent in the ability to disperse the volatile liquid in the mixture (S). It is preferably in the range of 2,000,000, more preferably in the range of 10,000 to 1,500,000, and further preferably in the range of 15,000 to 1,000,000. preferable. In addition, the number average molecular weight of the copolymer of the (meth) acrylic acid alkyl ester and the polyoxyalkylene mono (meth) acrylate compound is gel permeation chromatography (GPC) as described in detail in the following examples. Is a value measured by.

  Although it does not restrict | limit especially as a manufacturing method of the copolymer of a (meth) acrylic-acid alkylester and a polyoxyalkylene mono (meth) acrylate compound, For example, radical polymerization, anionic polymerization, etc. in the presence or absence of a solvent It can manufacture by the well-known method of these.

  The mixture (S) contains other components other than the urethane (meth) acrylate (A), the ethylenically unsaturated monomer (B) other than the urethane (meth) acrylate (A), a volatile liquid, and a dispersant. It may be. Examples of such other components include resins other than polymers formed from the above monomer (C), urethane (meth) acrylate (A) and ethylenically unsaturated monomer (B), which can be added as desired. Pigments, dyes, antifouling agents, antifungal agents, crosslinking agents, fillers, crosslinking accelerators, crosslinking aids, softeners, tackifiers, anti-aging agents, foaming agents, processing aids, adhesion promoters, Inorganic filler, organic filler, crystal nucleating agent, heat stabilizer, weathering stabilizer, antistatic agent, colorant, lubricant, flame retardant, flame retardant aid (antimony oxide, etc.), blooming inhibitor, mold release agent, increase Additives such as a sticking agent, an antioxidant, an ultraviolet absorber, and a conductive agent can be mentioned. As a proportion of the urethane (meth) acrylate (A) and the ethylenically unsaturated monomer (B) other than the urethane (meth) acrylate (A), the volatile liquid, and the dispersant in the mixture (S), It is preferably 90 to 100% by mass, more preferably 95 to 100% by mass, and further preferably 99 to 100% by mass.

  The mixture (S) is preferably mixed thoroughly after the above components are blended. As a mixing method, a conventionally known method can be employed, and examples thereof include a method using a propeller type stirrer, paddle type stirrer, anchor type stirrer, homomixer, ultramixer, magnetic stirrer and the like.

  The curing method in Step 1 is not particularly limited, and a known method can be used. For example, urethane (meth) is obtained by radical polymerization using a radical polymerization initiator or anionic polymerization using an anionic polymerization initiator. It can be carried out by copolymerizing the acrylate (A) and the ethylenically unsaturated monomer (B) and, if necessary, the monomer (C).

  The start of curing by the polymerization initiator can be induced by heat or light. Among these, it is preferable to use a polymerization initiator that initiates radical polymerization by heat or light because it is less susceptible to moisture and the like and the control of polymerization is easy.

  Among the above polymerization initiators, it is particularly preferable to use a polymerization initiator that initiates radical polymerization by heat, and a known thermal radical polymerization initiator can be used. Suitable thermal radical polymerization initiators include, for example, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), dimethyl 2,2′-azobis (2- Azo compounds such as methyl propionate); benzoyl peroxide, lauroyl peroxide, dicumyl peroxide, di-t-butyl peroxide, cumene hydroperoxide, t-butyl hydroperoxide, diisopropylbenzene hydroperoxide, etc. A peroxide is mentioned, Among these, 1 type (s) or 2 or more types can be used.

  Although the usage-amount of a polymerization initiator can be adjusted according to the density | concentration of the ethylenically unsaturated group in a urethane (meth) acrylate (A) or an ethylenically unsaturated monomer (B), the molecular weight of a polymerization initiator, etc. In general, from the viewpoint of smoothly proceeding the polymerization, 0.01 to 1 mass of the polymerization initiator is based on the total mass of the urethane (meth) acrylate (A) and the ethylenically unsaturated monomer (B). % Is preferably used.

The polymerization initiator may be added in advance when preparing the mixture (S), but after adding the polymerization initiator to the prepared mixture (S) and pouring it into a mold or the like, It is preferable to start the polymerization by light or heat to perform the curing.
The temperature at the time of curing when a thermal radical polymerization initiator is used as the polymerization initiator can be appropriately selected depending on the type and amount of the thermal radical polymerization initiator to be used, but is preferably in the range of 15 to 150 ° C. More preferably, it is the range of 30-120 degreeC, More preferably, it is the range of 50-90 degreeC.
Also, the curing time can be appropriately selected depending on the type and amount of polymerization initiator used, but is preferably in the range of 1 to 24 hours, more preferably in the range of 2 to 18 hours, Preferably it is the range for 3 to 12 hours.

  As the material of the mold for injecting the mixture (S), metal, resin, glass, ceramics, etc. can be used, but it is easy to take out after the curing reaction, and the metal content is extremely small. It is preferable that the inner surface is coated with a fluorine-based resin because a polishing pad in which contamination of the object by metal hardly occurs can be easily provided.

Step 2 is a step of removing volatile liquid. Step 2 may be performed on a product in the course of curing in step 1, but is preferably performed after the curing is sufficiently performed in step 1. A specific method for removing the volatile liquid includes a method for volatilizing the volatile liquid. By removing the volatile liquid in the step 2, the volatile liquid dispersed in the copolymer is replaced with air or the like, so that a foam structure is formed.
Although it does not restrict | limit especially as temperature in the process 2, Preferably it is the range of 30-150 degreeC, More preferably, it is the range of 40-120 degreeC. Further, the pressure in step 2 is not particularly limited, and conditions such as reduced pressure conditions and atmospheric pressure conditions can be adopted. Specific pressure is preferably in the range of 1 to 500 kPa as an absolute pressure, and in the range of 3 to 300 kPa. Is more preferable.
The removal time of the volatile liquid in the step 2 is preferably a time during which the volatile liquid can be sufficiently removed, and is usually in the range of 1 hour to 1 week.

  In step 2, it is preferable that the volatile liquid does not substantially remain in the obtained polishing layer, but a part of the volatile liquid remains in the polishing layer as long as the effects of the present invention are not impaired. It may be. As a removal rate of a volatile liquid, it is preferable that it is 80-100 mass%, and it is more preferable that it is 90-100 mass%. The removal rate of the volatile liquid in the present specification refers to the difference between the mass of the cured product before removing the volatile liquid and the mass of the cured product after removing the volatile liquid. The value divided by the mass of.

  A polishing layer having a foam structure can be obtained by the above steps 1 and 2. The obtained polishing layer may be used as a polishing pad as it is, but can be processed into a polishing pad having a desired size and shape by cutting, slicing or punching. The surface of the polishing pad is preferably subjected to a forming process such as grooves and holes for the purpose of improving the retention and fluidity of the polishing slurry and improving the efficiency of removing polishing debris from the surface of the polishing pad. The method of forming the polishing pad surface is not particularly limited, but a method of forming grooves or the like by cutting the polishing pad surface after the curing reaction of the mixture (S), and heating the polishing pad surface For example, a method of forming a groove or the like by bringing a contacted mold, a heat ray or the like into contact and dissolving the contact portion, a method of forming a hole or the like with a drill, a Thomson blade, or the like, or a method of forming with a laser or the like. Further, as a mold for injecting the mixture (S), a mold having a molding part (for example, a convex part having a desired shape) on the inner surface of the mold is used, and a molding process is performed simultaneously with curing. You can also. Further, the shape and diameter of grooves and holes applied in the molding process are not particularly limited.

  The polishing pad of the present invention may be composed of only the above polishing layer, or has a multilayer structure in which the polishing layer and a layer made of another material (for example, a cushion layer) are laminated. It may be. When the polishing pad of the present invention has a cushion layer, the followability of the polishing pad to the swell of a silicon wafer, a semiconductor wafer or the like may be improved. As the cushion layer, rubber, foamed elastic material, foamed plastic, etc., as well as non-woven fabrics impregnated with polyurethane (for example, “Suba400” (made by Nitta Haas Co., Ltd.)) currently used for general purposes should be adopted. There is no particular limitation. The preferable thickness of the cushion layer is 0.1 to 10 mm. If it is smaller than 0.1 mm, the uniformity of the flatness (uniformity) of the entire surface of the semiconductor wafer may be impaired. On the other hand, if it is larger than 10 mm, the local flatness of the semiconductor wafer may be impaired. The thickness of the cushion layer is preferably 0.2 to 5 mm, more preferably 0.5 to 2 mm.

  The polishing pad of the present invention can be used for chemical mechanical polishing (CMP) together with a known polishing slurry. The polishing slurry contains components such as a liquid medium such as water and oil; an abrasive such as silica, alumina, cerium oxide, zirconium oxide, and silicon carbide; a base, an acid, and a surfactant. Further, when performing chemical mechanical polishing (CMP), a lubricating oil, a coolant, or the like may be used in combination with the polishing slurry, if necessary.

  Chemical mechanical polishing (CMP) is performed by using a known chemical mechanical polishing apparatus and bringing the surface to be polished and the polishing pad into contact with each other through a polishing slurry at a constant speed for a certain period of time under pressure. Can do. The article to be polished is not particularly limited, and examples thereof include quartz, silicon, glass, an optical substrate, an electronic circuit substrate, a multilayer wiring substrate, and a hard disk. In particular, the object to be polished is preferably a silicon wafer or a semiconductor wafer. Specific examples of semiconductor wafers include, for example, insulating films such as silicon oxide, silicon oxyfluoride, and organic polymers, wiring metal films such as copper, aluminum, and tungsten, and barrier metals such as tantalum, titanium, tantalum nitride, and titanium nitride. Examples thereof include those having a film or the like on the surface.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. The physical properties of the dispersant, resin and polishing pad described in the examples were evaluated by the following methods.

[Number average molecular weight of dispersant]
The number average molecular weight of the dispersant was determined by gel permeation chromatography (GPC) measurement under the following conditions.
Column: Showa Denko Co., Ltd. "Shodex GPC KF-806M" and "Shodex GPC KF-802.5" connected in series in this order.
Solvent: Tetrahydrofuran Measurement temperature: 35 ° C
Detector: Differential refractive index (RI) detector Standard material: Polymethyl methacrylate

[Glass transition temperature of polymer consisting only of ethylenically unsaturated monomer (B)]
The glass transition temperature of the polymer consisting only of the ethylenically unsaturated monomer (B) is described in John Wiley & Sons, Inc. The value of the glass transition temperature (unit: K) of the homopolymer described in “POLYMER HANDBOOK FOURTH EDITION” issued by the company was used.

[Density of polishing layer]
Using the foamed structures or copolymers obtained in the following Examples and Comparative Examples, the density was measured according to JIS K-7112 to obtain the density of the polishing layer.

[Average diameter of bubbles in polishing layer]
The cross section of the foam structure obtained in the following examples is photographed with a scanning electron microscope (SEM), and the number of bubbles existing in a certain area is counted to determine the number of bubbles per unit area (number density of bubbles). Calculated. From the value, the density of the polishing layer, and the density of the non-foamed material produced separately, the diameter when the bubbles were assumed to be true spheres was determined and used as the average diameter of the bubbles in the polishing layer. The above-mentioned non-foamed material is produced under the same conditions as the production of the foamed structure except that a foaming agent (supercritical gas, fine hollow particles, volatile liquid, etc.) is not used.

[Dynamic elastic modulus of polishing layer at 50 ° C. and temperature of main dispersion peak]
The dynamic elastic modulus at 50 ° C. of the polishing layer was measured using the foam structure or copolymer obtained in the following examples and comparative examples, using a viscoelasticity measuring device “FT Rheospectrer DVE-” manufactured by Rheology Co., Ltd. Measurement was performed at a frequency of 11 Hz and a heating rate of 3 ° C./min. The temperature of the main dispersion peak was the temperature of the loss tangent peak.

[Contact angle of polishing layer with water]
The contact angle of the polishing layer with water was determined by leaving the foamed structures or copolymers obtained in the following Examples and Comparative Examples for 3 days under the conditions of 20 ° C. and 65% RH, and Kyowa Interface Science Co., Ltd. Measurement was performed using “Drop Master 500”.

[Water absorption after polishing for 3 days in 50 ° C. water of polishing layer]
The water absorption after the polishing layer was immersed in 50 ° C. water for 3 days was 3 cm in length and square (3 mm × 3 mm) in cross section from the foamed structures or copolymers obtained in the following Examples and Comparative Examples. A rod-shaped sample was cut out, immersed in distilled water at 50 ° C. for 3 days, and determined from the mass before immersion and the mass after immersion by the following formula (2).
Water absorption (mass%) = (mass after immersion−mass before immersion) / mass before immersion × 100 (2)

[Polishing performance of polishing pad]
The polishing pads prepared in the following examples and comparative examples were installed in a polishing apparatus “MAT-BC15” manufactured by MT Corporation, and a diamond dresser manufactured by Applied Materials Co., Ltd. (# 100—coverage 80%, The surface of the polishing pad was ground for 1 hour at a dresser rotational speed of 40 rpm while flowing distilled water at a rate of 150 mL / min (diameter 10 cm, mass 1 kg) (hereinafter referred to as “seasoning”). Next, under the conditions of a platen rotation speed of 60 rpm, a head rotation speed of 59 rpm, and a polishing pressure of 35 kPa, a diameter of 4 while supplying a solution obtained by diluting Cabot polishing slurry “SS25” twice with distilled water at a rate of 200 mL / min. A silicon wafer having an inch oxide film surface was polished for 60 seconds and then seasoned again for 30 seconds under the above conditions. Thereafter, the wafer was replaced, and polishing and seasoning were repeated again, and a total of 300 wafers were polished for each pad.
For every 50 sheets, the film thickness of the oxide film before and after polishing was measured at 49 points on the wafer surface, and the polishing rate at each point was determined. The average value of the 49 polishing rates was defined as the polishing rate, and the polishing uniformity was evaluated by the non-uniformity obtained by the following equation (3). A smaller non-uniformity value means that the wafer is uniformly polished in the wafer surface and the polishing uniformity is better.
Nonuniformity (%) = (σ / R) × 100 (3)
(However, σ: Standard deviation of polishing rate at 49 points, R: Average value of polishing rate at 49 points)

[Production Example 1] <Preparation of urethane (meth) acrylate (A)>
In a flask, 900 g of polytetramethylene glycol having a number average molecular weight of 2000 as the polyol (a1), 150 g of isophorone diisocyanate as the organic diisocyanate (a2), 0.011 g of dibutyltin dilaurate as the urethanization reaction catalyst, and Ciba Specialty Chemicals, Inc. as the polymerization inhibitor 0.277 g of “Irganox 1010” manufactured by the Company was weighed and stirred at 90 ° C. for 15 hours in a dry nitrogen atmosphere to quantitatively react the hydroxyl groups in the system to obtain an isocyanate group-terminated prepolymer.
After adding 277 g of methyl methacrylate and stirring uniformly, the temperature in the flask was lowered to 70 ° C., and 58.6 g of 2-hydroxyethyl methacrylate was added as a (meth) acrylic acid derivative (a3) having a hydroxyl group over 1 hour. And dripped.
After completion of dropping, 0.266 g of dibutyltin dilaurate was added as a urethanization reaction catalyst, and further stirred for 6 hours to quantitatively react the isocyanate groups in the system to 1109 g of urethane methacrylate (hereinafter abbreviated as PUA-1). A liquid mixture containing 277 g of methyl methacrylate was obtained. The number average molecular weight of PUA-1 was 4900, and the proportion of segments derived from polytetramethylene glycol in PUA-1 was 81% by mass.

[Production Example 2] <Preparation of Dispersant-1>
In a flask equipped with a cooling tube, 229 g of toluene was weighed and heated to 75 ° C., and then the system was sufficiently purged with nitrogen. After adding 25.2 g of methyl methacrylate and 37.8 g of polyoxyethylene methyl ether methacrylate (number average repeating number of oxyethylene units = 9) and stirring for 20 minutes, 0.76 g of dimethyl 2,2′-azobisisobutyrate and toluene A solution consisting of 15 g was added and held at 75 ° C. for 30 minutes. Next, a mixed liquid consisting of 16.8 g of methyl methacrylate and 25.2 g of polyoxyethylene methyl ether methacrylate (number average repeating number of oxyethylene units = 9) was dropped into the flask from the dropping funnel over 150 minutes, and dropped. After completion, the temperature was raised to 85 ° C. and maintained for 240 minutes to complete the polymerization. Thereafter, toluene was removed by a rotary evaporator to obtain a dispersant (hereinafter abbreviated as Dispersant-1). Dispersant-1 is a polymer having a number average molecular weight of 145,000, comprising 40% by mass of structural units derived from methyl methacrylate and 60% by mass of structural units derived from polyoxyethylene methyl ether methacrylate. Consists of.

[Production Example 3] <Preparation of Dispersion-2>
Manufacture other than using polyoxyethylene methyl ether methacrylate (number average repeating number of oxyethylene units = 23) instead of polyoxyethylene methyl ether methacrylate (number average repeating number of oxyethylene units = 9) in Production Example 2 A dispersant was obtained in the same manner as Example 2 (hereinafter abbreviated as Dispersant-2). Dispersant-2 is a polymer having a number average molecular weight of 109,000 composed of 40% by mass of structural units derived from methyl methacrylate and 60% by mass of structural units derived from polyoxyethylene methyl ether methacrylate. Consists of.

[Production Example 4] <Preparation of Dispersant-3>
In a flask equipped with a cooling tube, 229 g of toluene was weighed and heated to 75 ° C., and then the system was sufficiently purged with nitrogen. After adding 37.8 g of methyl methacrylate and 25.2 g of polyoxyethylene methyl ether methacrylate (number average repeating number of oxyethylene units = 23) and stirring for 20 minutes, 0.76 g of dimethyl 2,2′-azobisisobutyrate and toluene A solution consisting of 15 g was added and held at 75 ° C. for 30 minutes. Next, a mixed liquid consisting of 25.2 g of methyl methacrylate and 16.8 g of polyoxyethylene methyl ether methacrylate (number average repeating number of oxyethylene units = 23) was dropped from the dropping funnel into the flask over 150 minutes. After completion, the temperature was raised to 85 ° C. and maintained for 240 minutes to complete the polymerization. Thereafter, toluene was removed by a rotary evaporator to obtain a dispersant (hereinafter abbreviated as Dispersant-3). Dispersant-3 is a polymer having a number average molecular weight of 84,500 composed of 60% by mass of structural units derived from methyl methacrylate and 40% by mass of structural units derived from polyoxyethylene methyl ether methacrylate. Consists of.

[Production Example 5] <Preparation of Dispersant-4>
In a flask equipped with a cooling tube, 229 g of toluene was weighed and heated to 75 ° C., and then the system was sufficiently purged with nitrogen. 25.2 g of methyl methacrylate, 25.2 g of polyoxyethylene methyl ether methacrylate (number average repeating number of oxyethylene units = 9) and 12.6 g of polyoxyethylene methyl ether methacrylate (number average repeating number of oxyethylene units = 90) After stirring for 20 minutes, a solution consisting of 0.76 g of dimethyl 2,2′-azobisisobutyrate and 15 g of toluene was added and kept at 75 ° C. for 30 minutes. Next, 16.8 g of methyl methacrylate, 16.8 g of polyoxyethylene methyl ether methacrylate (number average repeating number of oxyethylene units = 9) and polyoxyethylene methyl ether methacrylate (number average repeating number of oxyethylene units = 90) 8 A liquid mixture consisting of 0.4 g was dropped from the dropping funnel into the flask over 150 minutes, and after completion of the dropping, the temperature was raised to 85 ° C. and maintained for 240 minutes to complete the polymerization. Thereafter, toluene was removed by a rotary evaporator to obtain a dispersant (hereinafter abbreviated as Dispersant-4). Dispersant-4 is derived from 40% by mass of structural units derived from methyl methacrylate and polyoxyethylene methyl ether methacrylate (the sum of the number average repeating number of oxyethylene units of 9 and 90). And a polymer having a number average molecular weight of 101,000.

[Example 1]
In a flask, the mixed liquid containing PUA-1 obtained in Production Example 1 and additional methyl methacrylate were weighed so that PUA-1 was 320 g and methyl methacrylate was 680 g, and further, as a volatile substance. 200 g of distilled water and 50 g of Dispersant-1 obtained in Production Example 2 as a dispersant were weighed and stirred at 300 rpm for 8 hours to obtain a mixture (S) in which water was uniformly dispersed in the W / O type. . To this mixture (S), 2 g of dimethyl 2,2′-azobis (2-methylpropionate) as a polymerization initiator was added and mixed uniformly, and then the inner surface was coated with a fluororesin. It was poured into a mold (inner dimensions: width 45 cm × height 50 cm × thickness 3 mm), and the air inside the mold was replaced with dry nitrogen, and then heated to 65 ° C. and held for 5 hours for polymerization and curing. The obtained polymerized cured product was dried at 50 ° C. for 3 days to evaporate the internal water to obtain a foamed structure having a closed cell structure.
The density of the obtained foamed structure was 0.97 g / cm ³ , the average diameter of the bubbles was 20 μm, the dynamic elastic modulus at 50 ° C. was 5.4 × 10 ⁸ Pa, the temperature of the main dispersion peak was 107 ° C., water The water absorption after immersion for 3 days in water at 77 ° C. and 50 ° C. was 3.3% by mass. The water removal rate before and after drying was 96% by mass. In addition, the glass transition temperature at the time of setting it as the polymer which consists only of ethylenically unsaturated monomer (methyl methacrylate monomer) is 105 degreeC.
Next, the foamed structure was punched into a circular shape having a diameter of 38 cm, and then a grid-like groove having a width of 1.5 mm, a depth of 1 mm, and a pitch of 10 mm was formed on the surface by grinding to produce a polishing pad. As a result of evaluating the polishing performance, as shown in Table 1, both the polishing rate and the polishing uniformity were good and the change with time was small.

[Example 2]
In Example 1, instead of 50 g of Dispersant-1 obtained in Production Example 2 as a dispersant, 5 g of Dispersant-1 obtained in Production Example 2 and Dispersant-2 obtained in Production Example 3 were used. A foamed structure and a polishing pad having a closed cell structure were produced in the same manner as in Example 1 except that 2.5 g was used in combination, and the polishing performance was evaluated. The density of the foam structure is 0.96 g / cm ³ , the average diameter of the bubbles is 40 μm, the dynamic elastic modulus at 50 ° C. is 5.4 × 10 ⁸ Pa, the temperature of the main dispersion peak is 108 ° C., and contact with water The water absorption after immersing in water at 79 degrees and 50 ° C. for 3 days was 2.9% by mass. The water removal rate before and after drying was 98% by mass. In addition, the glass transition temperature at the time of setting it as the polymer which consists only of ethylenically unsaturated monomer (methyl methacrylate monomer) is 105 degreeC. As a result of the evaluation of the polishing performance, as shown in Table 1, both the polishing rate and the polishing uniformity were good and the change with time was small.

[Example 3]
In Example 1, instead of 50 g of Dispersant-1 obtained in Production Example 2 as a dispersant, 5 g of Dispersant-2 obtained in Production Example 3 and Dispersant-3 obtained in Production Example 4 were used. A foamed structure and a polishing pad having a closed cell structure were produced in the same manner as in Example 1 except that 5 g was used together, and the polishing performance was tested. The density of the foam structure is 0.96 g / cm ³ , the average diameter of the bubbles is 30 μm, the dynamic elastic modulus at 50 ° C. is 5.3 × 10 ⁸ Pa, the temperature of the main dispersion peak is 108 ° C., and contact with water The water absorption after immersion for 3 days in water at 81 ° and 50 ° C. was 3.1% by mass. The water removal rate before and after drying was 97% by mass. In addition, the glass transition temperature at the time of setting it as the polymer which consists only of ethylenically unsaturated monomer (methyl methacrylate monomer) is 105 degreeC. As a result of the evaluation of the polishing performance, as shown in Table 1, both the polishing rate and the polishing uniformity were good and the change with time was small.

[Example 4]
In Example 1, the same procedure as in Example 1 was performed except that 10 g of Dispersant-4 obtained in Production Example 5 was used instead of 50 g of Dispersant-1 obtained in Production Example 2 as a dispersant. A foam structure and a polishing pad having a closed cell structure were produced, and polishing performance was tested. The density of the foam structure is 0.96 g / cm ³ , the average diameter of the bubbles is 60 μm, the dynamic elastic modulus at 50 ° C. is 5.3 × 10 ⁸ Pa, the temperature of the main dispersion peak is 107 ° C., and contact with water The water absorption after immersion for 3 days in water at 81 ° and 50 ° C. was 3.3% by mass. The water removal rate before and after drying was 96% by mass. In addition, the glass transition temperature at the time of setting it as the polymer which consists only of ethylenically unsaturated monomer (methyl methacrylate monomer) is 105 degreeC. As a result of the evaluation of the polishing performance, as shown in Table 1, both the polishing rate and the polishing uniformity were good and the change with time was small.

[Example 5]
In Example 4, a foamed structure and a polishing pad having a closed cell structure were produced in the same manner as in Example 4 except that the amount of distilled water was changed from 200 g to 300 g, and the polishing performance was tested. The density of the foam structure is 0.89 g / cm ³ , the average diameter of the bubbles is 70 μm, the dynamic elastic modulus at 50 ° C. is 3.6 × 10 ⁸ Pa, the temperature of the main dispersion peak is 101 ° C., and contact with water The water absorption after immersion for 3 days in water at an angle of 82 degrees and 50 ° C. was 3.4% by mass. The water removal rate before and after drying was 97% by mass. In addition, the glass transition temperature at the time of setting it as the polymer which consists only of ethylenically unsaturated monomer (methyl methacrylate monomer) is 105 degreeC. As a result of the evaluation of the polishing performance, as shown in Table 1, both the polishing rate and the polishing uniformity were good and the change with time was small.

[Comparative Example 1]
In a stainless steel mold (inner dimensions: width 45 cm × height 50 cm × thickness 3 mm) whose inner surface is coated with a fluororesin, a mixed liquid containing PUA-1 obtained in Production Example 1 is added. Methyl methacrylate, dimethyl 2,2′-azobis (2-methylpropionate) as a polymerization initiator, PUA-1: methyl methacrylate: dimethyl 2,2′-azobis (2-methylpropionate) = 70 : After pouring the mixed mixture to a mass ratio of 30: 0.15 and replacing the air inside the mold with dry nitrogen, the temperature was raised to 65 ° C. and held for 5 hours, and then raised to 120 ° C. Held for 30 minutes for polymerization and curing.
The density of the obtained copolymer was 1.08 g / cm ³ , the dynamic elastic modulus at 50 ° C. was 9.8 × 10 ⁷ Pa, the temperature of the main dispersion peak was 49 ° C., and the contact angle with water was 82 degrees. The water absorption after immersion in water at 50 ° C. for 3 days was 1.7% by mass. In addition, the glass transition temperature at the time of setting it as the polymer which consists only of ethylenically unsaturated monomer (methyl methacrylate monomer) is 105 degreeC.
Next, the copolymer was punched into a circle having a diameter of 38 cm, and then a grid-like groove having a width of 1.5 mm, a depth of 1 mm, and a pitch of 10 mm was formed on the surface by grinding to produce a polishing pad. As a result of evaluating the polishing performance, as shown in Table 1, the polishing rate and the polishing uniformity were inferior, and the change with time was also large.

  As is apparent from Table 1, in Examples 1 to 5 using the polishing pad composed of the polishing layer having a foam structure, it is understood that the polishing uniformity during polishing of the wafer and the stability of the polishing rate are extremely excellent. . On the other hand, in Comparative Example 1 using a polishing pad composed of a polishing layer having no foamed structure, the polishing uniformity and polishing rate at the time of wafer polishing are low, and the temporal stability thereof is as in Examples 1 to 5. It turns out that it is inferior compared.

According to the present invention, it is possible to provide a polishing pad useful for polishing a semiconductor wafer or the like with higher accuracy and higher efficiency and a method for manufacturing the same.

Claims (21)

  Foam containing a copolymer having a structural unit derived from urethane (meth) acrylate (A) and a structural unit derived from an ethylenically unsaturated monomer (B) other than urethane (meth) acrylate (A) A polishing pad having a structured polishing layer.   The polishing pad according to claim 1, wherein the urethane (meth) acrylate (A) has a number average molecular weight of 1000 or more.   The polishing pad according to claim 1 or 2, wherein the ethylenically unsaturated monomer (B) has an average molecular weight of 500 or less.   In the copolymer, the ratio of the mass of the structural unit derived from the urethane (meth) acrylate (A) to the mass of the structural unit derived from the ethylenically unsaturated monomer (B) is [urethane (meth). The mass of the structural unit derived from the acrylate (A)] / [the mass of the structural unit derived from the ethylenically unsaturated monomer (B)] = 20/80 to 60/40. The polishing pad described in 1.   The urethane (meth) acrylate (A) is a urethane (meth) acrylate obtained by reacting at least three components of a polyol (a1), an organic diisocyanate (a2), and a (meth) acrylic acid derivative (a3) having a hydroxyl group. The polishing pad according to any one of claims 1 to 4.   The polishing pad according to claim 5, wherein the polyol (a1) has a number average molecular weight of 500 to 5,000.   The glass transition temperature of the polymer when the ethylenically unsaturated monomer (B) is a polymer composed only of the ethylenically unsaturated monomer (B) is 60 ° C or higher. The polishing pad as described.   The ethylenically unsaturated monomer (B) is a (meth) acrylic acid derivative or a mixture of a (meth) acrylic acid derivative and an ethylenically unsaturated monomer other than the (meth) acrylic acid derivative. A polishing pad according to any one of the above. The polishing pad according to claim 1, wherein the polishing layer has a density of 0.6 to 1.1 g / cm ³ .   The polishing pad according to any one of claims 1 to 9, wherein an average diameter of bubbles constituting the foam structure of the polishing layer is 1 to 100 µm.   The polishing pad according to any one of claims 1 to 10, wherein the foamed structure of the polishing layer is formed by removing a volatile liquid dispersed in a copolymer. The polishing pad according to claim 1, wherein the polishing layer has a dynamic elastic modulus at 50 ° C. of 9 × 10 ⁸ Pa or less. The polishing pad according to claim 1, wherein the polishing layer has a dynamic elastic modulus at 50 ° C. of 1 × 10 ⁸ Pa or more.   The polishing pad according to claim 1, wherein a peak temperature of main dispersion of the polishing layer is 80 ° C. or higher.   A step (step 1) of curing a mixture (S) containing urethane (meth) acrylate (A), an ethylenically unsaturated monomer (B) other than urethane (meth) acrylate (A) and a volatile liquid (step 1), and volatile A method for producing a polishing pad having a foamed polishing layer, comprising a step of removing a liquid (step 2).   The manufacturing method according to claim 15, wherein the volatile liquid is water or a mixture containing water.   The manufacturing method according to claim 16, wherein in the mixture (S), water or a mixture containing water is dispersed in a W / O type.   The manufacturing method according to any one of claims 15 to 17, wherein the mixture (S) further contains a dispersant.   The production method according to claim 18, wherein the dispersant is a copolymer of an alkyl (meth) acrylate and a polyoxyalkylene mono (meth) acrylate compound.   A method for polishing a silicon wafer or a semiconductor wafer using the polishing pad according to claim 1. A semiconductor device manufactured using the polishing pad according to claim 1.