JP2013203782A - Composition, polishing pad and method for producing composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composition having high elongation, a method for producing the composition, and a polishing pad causing few defects on a wafer surface and having an extended pad service life.SOLUTION: A composition includes a polymer obtained from an ethylenically unsaturated compound by polymerization and polyurethane, wherein a compound represented by formula (1) is included as the ethylenically unsaturated compound. In the formula, Rand Rare hydrogen; Ris hydrogen or alkyl; and Ris an organic group including a structure in which six or more carbon atoms and/or oxygen atoms link together in a straight chain.

Description

  The present invention relates to a composition containing polyurethane, a method for producing the same, and a polishing pad using the same. In particular, the present invention relates to a polishing pad for polishing and flattening an interlayer insulating film and a wiring forming metal film formed on a semiconductor substrate such as silicon.

  As electronic devices such as mobile phones and personal computers become higher in performance, higher integration and higher speed of LSI are expected. As a means for this, multilayering and miniaturization are being pursued. One of the most important techniques in multilayer wiring is a planarization process for ensuring the depth of focus (DOF) of lithography. This is because, in multilayer wiring, if there are uneven steps in the interlayer insulating film or wiring metal film, focusing cannot be performed and a fine wiring structure cannot be formed. As the planarization processing method, CMP (Chemical Mechanical Polishing) is most practically used at present.

  In general, a CMP apparatus includes a polishing head that holds a semiconductor wafer that is an object to be processed, a polishing pad for polishing the object to be processed, and a polishing surface plate that holds the polishing pad. The polishing process of the semiconductor wafer uses a slurry to move the semiconductor wafer and the polishing pad relative to each other, thereby removing the protruding portion of the layer on the surface of the semiconductor wafer and flattening the layer on the surface of the wafer.

  Characteristics required for the polishing pad include ensuring local flatness and global flatness of the semiconductor wafer surface, preventing the occurrence of defects, and maintaining a high polishing rate. Currently, there is a demand for further cost reduction of semiconductor wafers, and further improvement of yield and long life by preventing defects on the wafer surface are also demanded for polishing pads.

  Patent Document 1 discloses a polishing pad made of a polymer polymerized from polyurethane and a vinyl compound. Patent Document 2 discloses a method for producing a polishing pad including a step of causing a polymerization reaction of a monomer after immersing a polymer molded body in a solution containing a monomer for polymerization. Further, Patent Document 3 discloses a polishing pad comprising a high elastic modulus component and a low elastic modulus component.

International Publication No. 00/12262 JP 2000-218551 A JP 2008-168422 A

  However, the present inventors have found that the polishing pads described in Patent Documents 1 and 2 have many defects on the wafer surface, and the life of the pad is insufficient. Further, it has been found that the cause is that the interpenetrating polymer network constituting the polishing pad is insufficient in flexibility and elongation. Moreover, in the polishing pad of patent document 3, it discovered that the pad scraps derived from a high elastic modulus component were hard, and might increase the defect on the wafer surface.

  Then, the objective of this invention is providing the composition which has high elongation, and its manufacturing method. It is another object of the present invention to provide a polishing pad with fewer defects on the wafer surface and a longer pad life.

  As a method for improving the elongation, the present inventors reduce the glass transition point of the polymer polymerized from the ethylenically unsaturated compound so that the soft segment portion expressing the elongation of the polyurethane can freely expand and contract. Inspired. Then, as the method, the idea was to use an ethylenically unsaturated compound having a long side chain on a straight chain.

  Here, the polishing pad composed of the high elastic modulus component and the low elastic modulus component described in Patent Document 3 described above has a low elastic modulus component in the high elastic modulus component, and increases the impact resistance. It is intended and is different in concept from the present invention.

  As a result of intensive studies, the inventors of the present invention are represented by the formula (1) in order to produce a polishing pad having a high elongation in the polishing pad production method disclosed in Japanese Patent Application Laid-Open No. 2006-233198. It has been found that the object of the present invention can be achieved by using an ethylenically unsaturated compound.

  That is, this invention is a composition characterized by including the polymer and polyurethane which are polymerized from an ethylenically unsaturated compound, and the compound represented by Formula (1) as said ethylenically unsaturated compound.

(R ¹ and R ³ are hydrogen, R ² is hydrogen or an alkyl group, and R ⁴ is an organic group containing a structure in which six or more carbon atoms and / or oxygen atoms are connected in a straight chain.)

  According to the present invention, a composition having high elongation can be obtained. In addition, since the elongation is high and flexible, a polishing pad with few defects on the wafer surface and a longer pad life can be produced.

  The composition in the present invention contains a polymer polymerized from an ethylenically unsaturated compound and polyurethane, regardless of whether it is liquid or solid.

  The composition in the present invention is not particularly limited as long as it contains a polymer polymerized from an ethylenically unsaturated compound and polyurethane, but is preferably an interpenetrating polymer network structure. In the present invention, the interpenetrating polymer network structure refers to a polymer in which independent different types of polymer networks enter each other without chemically bonding to each other in the polymer mixed system. Specifically, a structure in which a plurality of types of polymers are dispersed at several nm to several hundred nm is formed. The degree of dispersion is preferably 5 nm to 300 nm, and particularly preferably 5 nm to 100 nm. In addition, a structure in which different types of polymers are continuous layers may be stabilized by forming cross-linking points.

  The interpenetrating polymer network structure can be formed by a production method in which polyurethane is immersed in a radical polymerizable composition and an ethylenically unsaturated compound in the radical polymerizable composition is polymerized. The polishing pad of the present invention preferably includes an interpenetrating polymer network.

  The ethylenically unsaturated compound in the present invention refers to a compound having a radical polymerizable carbon-carbon double bond. And the composition of this invention contains the polymer superposed | polymerized from the ethylenically unsaturated compound containing the compound represented by Formula (1).

R ¹ and R ³ are hydrogen, R ² is hydrogen or an alkyl group, and R ⁴ is an organic group containing a structure in which six or more carbon atoms and / or oxygen atoms are connected in a straight chain.

A structure in which six or more carbon atoms and / or oxygen atoms are connected in a straight chain (hereinafter referred to as “six-series structure”) means that carbon atoms and / or oxygen atoms are either single bonds, double bonds or triple bonds. This refers to a structure in which six or more chains are connected in a straight chain. The structure is not particularly limited. For example, a hexylene structure represented by (CH ₂ ) _{6 in} which six carbon atoms are connected in a straight chain, or two carbon atoms and one oxygen atom are alternately linear. Examples thereof include an ethylene oxide structure represented by (CH ₂ CH ₂ O) _k (where k is an integer of 2 or more). Two types of single bonds, double bonds, and triple bonds may be included in one 6-series structure. Further, the straight chain means that a branched structure is not included. For example, a neohexyl structure represented by (CH ₃ ) ₃ CCH ₂ CH ₂ is not included in the straight chain.

If the 6-series structure is included, a branched structure may be included in the 6-series structure, for example, CH ₂ CH ₂ CH (CH ₃ ) CH ₂ CH ₂ CH ₂ . In addition, a structure in which 6 to 30 carbon atoms and / or oxygen atoms are connected in a straight chain is preferable in terms of low molecular weight and easy impregnation into polyurethane and polymerization. Furthermore, the structure in which carbon atoms and / or oxygen atoms are connected in a straight chain of 9 to 30 is that the composition has higher elongation, fewer defects on the wafer surface, and more padding. This is more preferable because a polishing pad having an extended life can be obtained.

The organic group R ⁴ only needs to have at least one 6-series structure in the molecule, and the structure of the other portions is not particularly limited. Preferably, the portion other than the 6-series structure of the organic group R ⁴ is composed of an atom selected from the group consisting of a carbon atom, a hydrogen atom and an oxygen atom. R ⁴ may contain an aliphatic ring or an aromatic ring. Note that six atoms in these ring structures are not included in the series structure.

  As a specific example of the compound represented by the formula (1), for example, a group represented by any of the following formulas (2) to (6) is preferable.

  In the formulas (2) to (6), m is an integer of 5 or more, n and l are integers satisfying “n is 1 and 1 is 2 or more” or “n is 2 or more and 1 is 0 or more”, p and q is an integer satisfying “p is 1 and q is 1 or more” or “p is 2 or more and q is 0 or more”, and r and s are “r is 1 and s is 5 or more” or “r is 2 or more” And s is an integer satisfying “0 or more”.

  m is preferably 8 or more, and preferably 29 or less. n is preferably 9 or less. l is preferably 26 or less. p is preferably 7 or less. q is preferably 25 or less. r is preferably 10 or less. s is preferably 29 or less.

  The reason why the polymer polymerized using the ethylenically unsaturated compound represented by formula (1) and the composition containing polyurethane has high elongation is estimated as follows. In a composition comprising a polymer polymerized from an ethylenically unsaturated compound and polyurethane, when the glass transition point of the polymer polymerized from the ethylenically unsaturated compound is high, the soft segment of the polyurethane exhibiting elongation is ethylenically unsaturated. The elongation is lowered because the polymer is polymerized from a saturated compound and cannot freely expand and contract. However, since the polymer containing the ethylenically unsaturated compound represented by the formula (1) has a long linear side chain, the glass transition point is lowered, and the force for restraining the soft segment portion exhibiting elongation is weak. Become. For this reason, it is considered that the soft segment portion that exhibits elongation becomes flexible. As a result, since the polishing pad using this composition has high elongation and is flexible, it is presumed that there are few defects on the wafer surface and the pad life is longer.

  Specific examples of the ethylenically unsaturated compound represented by formula (1) include hexyl acrylate, heptyl acrylate, octyl acrylate, nonyl acrylate, decyl acrylate, undecyl acrylate, lauryl acrylate, and tridecyl. Acrylate, tetradecyl acrylate, pentadecyl acrylate, hexadecyl acrylate, stearyl acrylate, behenyl acrylate, 2-ethylhexyl acrylate, isodecyl acrylate, methoxydiethylene glycol acrylate, methoxytriethylene glycol acrylate, methoxypolyethylene glycol acrylate, methoxydipropylene glycol acrylate, Ethoxydiethylene glycol acrylate, ethoxytrie Ren glycol acrylate, ethoxy polyethylene glycol acrylate, butoxy ethyl acrylate, butoxy diethylene glycol acrylate, butoxy triethylene glycol acrylate, butoxy polyethylene glycol acrylate, 2-ethylhexyl diglycol acrylate, phenoxy diethylene glycol acrylate, phenoxy triethylene glycol acrylate, phenoxy polyethylene glycol acrylate, Nonylphenol EO adduct acrylate, alkylphenoxy polyethylene glycol acrylate, nonylphenol PO adduct acrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, nonyl methacrylate, decyl methacrylate, un Sil methacrylate, lauryl methacrylate, tridecyl methacrylate, tetradecyl methacrylate, pentadecyl methacrylate, hexadecyl methacrylate, stearyl methacrylate, behenyl methacrylate, 2-ethylhexyl methacrylate, isodecyl methacrylate, methoxydiethylene glycol methacrylate, methoxytriethylene glycol methacrylate, methoxypolyethylene glycol Methacrylate, methoxydipropylene glycol methacrylate, ethoxydiethylene glycol methacrylate, ethoxytriethylene glycol methacrylate, ethoxy polyethylene glycol methacrylate, butoxyethyl methacrylate, butoxydiethylene glycol methacrylate, butoxyto Reethylene glycol methacrylate, butoxy polyethylene glycol methacrylate, 2-ethylhexyl diglycol methacrylate, phenoxy diethylene glycol methacrylate, phenoxy triethylene glycol methacrylate, phenoxy polyethylene glycol methacrylate, nonylphenol EO adduct methacrylate, alkylphenoxy polyethylene glycol methacrylate, nonylphenol PO adduct methacrylate, etc. Can be mentioned. These may be used alone or in combination of two or more.

  Among these, hexyl acrylate, heptyl acrylate, octyl acrylate, nonyl acrylate, decyl acrylate, undecyl acrylate, lauryl acrylate, tridecyl acrylate, 2-ethylhexyl acrylate, isodecyl acrylate, methoxydiethylene glycol acrylate, methoxytriethylene glycol acrylate, methoxy Polyethylene glycol acrylate, methoxydipropylene glycol acrylate, ethoxydiethylene glycol acrylate, ethoxytriethylene glycol acrylate, ethoxy polyethylene glycol acrylate, butoxyethyl acrylate, butoxydiethylene glycol acrylate, butoxytriethylene glycol acrylate, Toxipolyethylene glycol acrylate, 2-ethylhexyl diglycol acrylate, phenoxy diethylene glycol acrylate, phenoxy triethylene glycol acrylate, phenoxy polyethylene glycol acrylate, nonylphenol EO adduct acrylate, alkylphenoxy polyethylene glycol acrylate, nonylphenol PO adduct acrylate, hexyl methacrylate, heptyl methacrylate Octyl methacrylate, nonyl methacrylate, decyl methacrylate, undecyl methacrylate, lauryl methacrylate, tridecyl methacrylate, 2-ethylhexyl methacrylate, isodecyl methacrylate, methoxydiethylene glycol methacrylate, methoxytri Tylene glycol methacrylate, methoxy polyethylene glycol methacrylate, methoxy dipropylene glycol methacrylate, ethoxy diethylene glycol methacrylate, ethoxy triethylene glycol methacrylate, ethoxy polyethylene glycol methacrylate, butoxy ethyl methacrylate, butoxy diethylene glycol methacrylate, butoxy triethylene glycol methacrylate, butoxy polyethylene glycol methacrylate, 2 -Ethylhexyl diglycol methacrylate, phenoxydiethylene glycol methacrylate, phenoxytriethylene glycol methacrylate, phenoxypolyethylene glycol methacrylate, nonylphenol EO adduct methacrylate, alkylphenol Enoxypolyethylene glycol methacrylate and nonylphenol PO adduct methacrylate are preferred because they have a small molecular weight and are easy to impregnate and polymerize polyurethane. In addition, it is preferable that the molecular weight of the compound represented by Formula (1) is about 100-600.

  The content of the ethylenically unsaturated compound represented by the formula (1) in the entire ethylenically unsaturated compound is preferably 3 to 60% by weight. By making the content 3% by weight or more, the effect of using the ethylenically unsaturated compound represented by the formula (1) is more remarkably exhibited, there are fewer defects on the wafer surface, and the pad life is more Can be extended. Further, the content is preferably 60% by weight or less from the viewpoint of easy impregnation and polymerization in polyurethane. As an upper limit, More preferably, it is 50 weight% or less, More preferably, it is 30 weight% or less. Further, the lower limit is more preferably 10% by weight or more.

  Specific examples of the ethylenically unsaturated compound that can be used in addition to the compound represented by the formula (1) in the present invention include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, n- Butyl acrylate, n-butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, methyl (α-ethyl) acrylate, ethyl (α-ethyl) acrylate, propyl (α-ethyl) acrylate, butyl (α-ethyl) acrylate, 2-hydroxyethyl Methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, glycidylmeta Relate, isobornyl methacrylate, acrylic acid, methacrylic acid, fumaric acid, dimethyl fumarate, diethyl fumarate, dipropyl fumarate, maleic acid, dimethyl maleate, diethyl maleate, dipropyl maleate, N-isopropylmaleimide, N- Cyclohexylmaleimide, N-phenylmaleimide, N, N ′-(4,4′-diphenylmethane) bismaleimide, bis (3-ethyl-5-methyl-4-maleimidophenyl) methane, acrylonitrile, acrylamide, vinyl chloride, vinylidene chloride , Styrene, α-methylstyrene, divinylbenzene, ethylene glycol dimethacrylate, allyl methacrylate and the like.

  Among these, acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, n-butyl acrylate, n-butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, methyl (α-ethyl) Acrylate, ethyl (α-ethyl) acrylate, propyl (α-ethyl) acrylate, and butyl (α-ethyl) acrylate are preferable in terms of easy impregnation and polymerization of polyurethane.

  The use of the ethylenically unsaturated compound represented by the formula (1) in the production of the composition is confirmed by analyzing by pyrolysis gas chromatography / mass spectrometry method, FT-IR ATR method, solid state NMR method. it can. A double shot pyrolyzer PY-200D (manufactured by Frontier Laboratories) can be cited as a thermal decomposition apparatus, and TRIO-1 (manufactured by VG) can be cited as a gas chromatograph / mass spectrometer.

  The radical polymerizable composition in the present invention refers to a composition containing the above ethylenically unsaturated compound and a radical polymerization initiator. Chain transfer agents, radical polymerization inhibitors, antioxidants, anti-aging agents, fillers, colorants, antifungal agents, antibacterial agents, flame retardants, ultraviolet absorbers and the like are further included in the radical polymerizable composition. Also good. It is preferable to use these compounds in a range not exceeding 20% by weight in total with respect to the ethylenically unsaturated compound.

  In addition, the radically polymerizable composition is preferably a composition that does not substantially contain an organic solvent from the viewpoint of economy that the organic solvent removal step is unnecessary. “Substantially free of organic solvent” means that the organic solvent is less than 1% by weight based on the ethylenically unsaturated compound.

  The radical polymerization initiator in the present invention refers to a compound that decomposes by heating, light irradiation, radiation irradiation or the like to generate radicals. Examples of such radical polymerization initiators include azo compounds and peroxides. Specifically, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), 4, Azo-based polymerization such as 4'-azobis (4-cyanovaleric acid) 1,1'-azobis (cyclohexane-1-carbonitrile), 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile) Initiator, cumene hydroperoxide, t-butyl hydroperoxide, dicumyl peroxide, di-t-butyl peroxide, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxyisobutyrate, t-butyl peroxybivalate t-butyl peroxybenzoate, t-butyl peroxyacetate, diisopropyl peroxydicarbonate, di- - it can be exemplified butyl peroxydicarbonate, benzoyl peroxide, acetyl peroxide, lauroyl peroxide, a peroxide polymerization initiator such as. The addition amount of the radical polymerization initiator is preferably 0.01 to 5% by weight, more preferably 0.05 to 5% by weight, based on the ethylenically unsaturated compound.

  The chain transfer agent in the present invention refers to a compound that reacts with a growing radical to stop an increase in polymer chain length and generate a low-molecular radical capable of reinitiating.

  Examples of chain transfer agents include n-butyl mercaptan, isobutyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, sec-butyl mercaptan, sec-dodecyl mercaptan, t-butyl mercaptan and other alkyl groups or substituted alkyl groups. Aromatic mercaptans such as primary, secondary or tertiary mercaptan, phenyl mercaptan, thiocresol, 4-t-butyl-o-thiocresol, thioglycol such as thioglycolic acid-2-ethylhexyl, ethyl thioglycolate Examples thereof include acid esters, mercaptans having 3 to 18 carbon atoms such as ethylene thioglycol, α-methylstyrene dimer, carbon tetrachloride, toluene, ethylbenzene, triethylamine and the like. These may be used alone or in combination of two or more. Of these, alkyl mercaptans such as t-butyl mercaptan, n-butyl mercaptan, isobutyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, and α-methylstyrene dimer are preferably used.

  The amount of chain transfer agent used is preferably 0.01 to 15% by weight, more preferably 0.05 to 10% by weight, based on the ethylenically unsaturated compound. When the amount used is 0.01% by weight or more, the effect as a chain transfer agent is expressed. When the amount used is 15% by weight or less, the molecular weight of the polymer chain becomes appropriate, and the interpenetration with excellent mechanical properties is achieved. A polymer network is obtained.

  As a radical polymerization inhibitor that can be contained in a radical polymerizable composition and is solid at room temperature, hydroquinone, hydroquinone monomethyl ether, topanol A, catechol, t-butylcatechol, 2,6-di-t-butyl-4-methylphenol Phenothiazine, diphenylamine, N, N′-diphenyl-p-phenylenediamine, p-phenylenediamine and the like. One or two or more compounds selected from these compounds can be used. The radical polymerization inhibitor may be used by being added to the radical polymerizable composition. Moreover, you may add beforehand at the time of polyurethane manufacture. Furthermore, you may make it contain in both a radically polymerizable composition and a polyurethane. When a radical polymerization inhibitor is used for both the radical polymerizable composition and the polyurethane, the type of radical polymerization inhibitor may be the same compound or different. In addition, for the purpose of enhancing the polymerization inhibition effect, it is preferable to perform impregnation and / or polymerization in the presence of oxygen gas or oxygen-containing gas.

  Examples of the radical polymerization inhibitor that is preferably impregnated and / or polymerized in the presence of oxygen gas or oxygen-containing gas include hydroquinone, hydroquinone monomethyl ether, topanol A, catechol, t-butylcatechol, and p-phenylenediamine. it can. As the oxygen-containing gas, air, oxygen, or a gas obtained by diluting oxygen with an inert gas is used. Examples of the inert gas include nitrogen, helium, and argon. The oxygen concentration when diluted is not particularly limited, but is preferably 1% by volume or more. As the oxygen-containing gas to be used, dry air or a gas obtained by diluting dry air with nitrogen is preferable because it is inexpensive.

  The organic solvent in the present invention is a compound that does not substantially react during the polymerization of the ethylenically unsaturated compound and is an organic compound that is liquid at room temperature. Specific examples include hexane, dimethylformamide, dimethyl sulfoxide, ethanol, methanol, and the like. Carbon tetrachloride, toluene, ethylbenzene, etc. are usually known as organic solvents, but in the radical polymerization process, the growing radicals extract hydrogen and chlorine to become stable polymers, and the newly generated radicals become ethylenically unsaturated compounds. Since the effect as a chain transfer agent that the polymerization proceeds by addition to is known, these compounds do not hit the organic solvent that does not substantially react with the ethylenically unsaturated compound mentioned here.

  The polyurethane in the present invention may be solid, hollow or foamed. The characteristics are not particularly limited, but it is necessary that the composition can be taken into the polyurethane and impregnated by being immersed in the radically polymerizable composition. Therefore, it is necessary to be made of a material having an affinity with the radical polymerizable composition, and to have flexibility that allows the polyurethane itself to swell by incorporating the radical polymerizable composition.

  Depending on the density and amount of impregnation of the radical polymerizable composition, the volume of the polyurethane after impregnation swells to about 1.03 to 5 times the original volume, and most swells to about 1.03 to 3 times. To do.

  The form of polyurethane is preferably a foam having closed cells having an average cell diameter of 10 to 200 μm, more preferably a foam having closed cells of 20 to 150 μm, and having closed cells of 30 to 120 μm. A foam is particularly preferred. The average bubble diameter can be obtained by forming the surface or sliced surface of the polishing pad into a scanning electron microscope (SEM) image at a magnification of 200 times and subjecting the average bubble diameter to image processing.

As the apparent density of the polyurethane is preferably 0.1~1.2g / cm ^3, more preferably 0.5 to 1.0 g / cm ^3. The apparent density can be measured by the method described in Japanese Industrial Standard (JIS) K 7112 (1999 edition). Furthermore, the radically polymerizable composition taken into the polyurethane does not enter the bubbles in the polyurethane, and the polyurethane bubbles remain as bubbles even after the ethylenically unsaturated compound is polymerized under the swollen state of the polyurethane. It is preferable. Apparent density of the polishing pad obtained as a result is preferably 0.2~1.1g / cm ^3, more preferably 0.6~1.1g / cm ^3.

  The polyurethane in the present invention is preferably a polyurethane molded product obtained from a polyol and a polyisocyanate, and particularly preferably a polyurethane molded product obtained by mixing two liquids of a polyol and a polyisocyanate. Here, the polyol refers to a compound having two or more hydroxyl groups. For example, 1 type and 2 or more types of mixtures chosen from polyether polyol, polyester polyol, polycarbonate polyol, polycaprolactone polyol, ethylene glycol, propylene glycol, glycerol etc. can be mentioned. The molecular weight of the polyol is preferably a number average molecular weight of 3000 or more. When the number average molecular weight is 3000 or less, the crosslinking agent containing an epoxy group and the radical polymerizable composition may not be impregnated.

  Polyisocyanates include aromatic isocyanates such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polymeric MDI, and naphthalene diisocyanate, aliphatic diisocyanates such as tetramethylene diisocyanate and hexamethylene diisocyanate, isophorone diisocyanate, hydrogen Examples thereof include alicyclic diisocyanates such as added TDI and hydrogenated MDI. It can be used as a mixture of one or more selected from these isocyanates. Moreover, the isocyanurate group may be contained in the polyurethane.

  In preparation of polyurethane, in addition to polyol and polyisocyanate, crosslinking agent, chain extender, foam stabilizer, foaming agent, resination catalyst, foaming catalyst, antioxidant, anti-aging agent, filler, plasticizer, It may contain a coloring agent, an antifungal agent, an antibacterial agent, a flame retardant, and an ultraviolet absorber and may be molded. The method for preparing polyurethane is not particularly limited, but it can be prepared by methods such as injection molding and reaction molding. In particular, in the preparation of a polyurethane molded body, a high-pressure injection machine that instantaneously mixes raw materials by colliding with each other in a mixing head, and a so-called low-pressure injection machine that mechanically mixes each raw material supplied to the mixing head with a stirring blade or the like. It is preferable to use it and apply it to molding or slab molding.

  The weight ratio of the polyurethane and the polymer polymerized from the impregnated ethylenically unsaturated compound is preferably 100/5 to 100/300, and more preferably 100/50 to 100/200. When the weight ratio of the polyurethane and the polymer polymerized from the impregnated ethylenically unsaturated compound is 100/5 or more, the effect of containing the polymer polymerized from the ethylenically unsaturated compound is expressed, and , 100/300 or less can prevent the time required for impregnation from becoming long. Analysis of the weight ratio of the polymer polymerized from the polyurethane and the impregnated ethylenically unsaturated compound can be measured by a pyrolysis gas chromatography / mass spectrometry technique. The step of impregnating the radically polymerizable composition with polyurethane is preferably 15 hours to 60 ° C. for 3 hours to 20 days, and more preferably 3 hours to 10 days.

  A polishing pad comprising the composition of the present invention can be produced, for example, as follows. A radical polymerizable composition containing an ethylenically unsaturated compound represented by formula (1) is prepared so that the weight ratio of the polyurethane molded product and the radical polymerizable composition is a predetermined ratio, and the polyurethane molded product is impregnated. Let The polyurethane molded body swollen by the impregnation is placed in a sealed container, heated at a predetermined time and at a predetermined temperature, and then dried at a predetermined time and at a predetermined temperature. Heating is preferably performed at 30 to 150 ° C. for 1 to 120 hours. You may change heating temperature on the way. Drying is preferably performed at room temperature to 150 ° C. for 30 minutes to 24 hours. The impregnated cured product of the polyurethane molded product thus obtained can be sliced and ground to form a polishing layer used for a polishing pad. A cushion layer is bonded to the polishing layer obtained by the above method, the laminate is punched into a circular shape, and groove processing is performed on one surface thereof to obtain a polishing pad.

The polishing pad of the present invention preferably has a closed cell of 10 to 200 μm, more preferably a foam having a closed cell of 20 to 150 μm, and a foam having a closed cell of 30 to 120 μm. Particularly preferred. The average bubble diameter is obtained by imaging the surface of the polishing pad or the sliced surface with an image of a scanning electron microscope (SEM) at a magnification of 200 and processing the average bubble diameter. It is preferable that the surface of the polishing pad has a flat surface and openings derived from bubbles at an appropriate ratio. Cell count at any slice plane is preferably 20 to 1000 pieces / mm ^2, and more preferably 200 to 600 pieces / mm ^2. The apparent density of the polishing pad is preferably 0.2 to 1.1 g / cm ² . The apparent density can be measured by the method described in Japanese Industrial Standard (JIS) K 7112 (1999 edition).

  The object to be polished in the polishing pad of the present invention is not particularly limited. Specific examples include semiconductor substrates, optical glass, optical lenses, magnetic heads, hard disks, color filters for liquid crystal displays, optical members such as a back plate for plasma displays, ceramics, sapphire, and the like. Among these, it is particularly preferable to use for polishing for the purpose of planarization of a semiconductor wafer by a chemical mechanical polishing (CMP) technique. In the CMP process, a polishing pad made up of a polishing agent and a chemical solution is used to polish the semiconductor wafer surface by moving the semiconductor wafer and the polishing pad relative to each other, thereby making the semiconductor wafer surface flat and smooth. Is used.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, these do not limit this invention. The evaluation method was performed as follows.

  [Apparent Density] Measured using a pycnometer (Harvard type) according to the method described in JIS K 7112 (1999 edition).

[Average Bubble Diameter and Number of Surface Bubbles] The average bubble diameter is analyzed with an image processing apparatus using a scanning electron microscope “SEM2400” (manufactured by Hitachi, Ltd.) and a photograph of the cross section of the pad observed at a magnification of 200 times. Thus, all the bubble diameters present in the photograph were measured, and the average value was taken as the average bubble diameter. The number of all bubbles present in the photograph was measured, and the number of bubbles per 1 mm ² was defined as the number of surface bubbles.

  [Wet hardness] A sample obtained by cutting out the prepared composition into a size of 3 cm × 3 cm (thickness: arbitrary) is used as a hardness measurement sample, vacuum-dried at 70 ° C. for 12 hours, and humidity-controlled in a temperature-controlled room for 24 hours. Then, it was immersed in ultrapure water for 24 hours, measured at three points with an Asker D type hardness meter (manufactured by Kobunshi Keiki Co., Ltd.), and the average value was defined as wet hardness.

[Tensile Test] Using a tensile tester RTM-100 (manufactured by Orientec Co., Ltd.), the tensile elongation at break was measured under the following measurement conditions. The average value of the five test pieces was taken as the measured value.
Test temperature: 25 ° C
Test piece shape: No. 1 type small test piece Test piece thickness: 1-2 mm
Distance between chucks: 58mm
Test speed: 50 mm / min.

[Polishing Evaluation] A polishing pad was attached to a surface plate of a polishing machine (“MIRRA3400” manufactured by Applied Materials), and 200 8-inch oxide oxide wafers were polished under the following conditions.
Retainer ring pressure: 41 kPa (6 psi)
Inner tube pressure: 28 kPa (4 psi)
Membrane pressure: 28 kPa (4 psi)
Platen rotation speed: 76rpm
Polishing head rotation speed: 75 rpm
Slurry: SS-25 (manufactured by Cabot), flow rate 150 mL / min dresser: manufactured by SAESOL, load 17.6 N (4 lbf)
Polishing time: 1 minute.

  [Average Polishing Rate and In-Plane Uniformity] The polishing rate was measured in the diameter direction, excluding the outermost periphery of 10 mm of the 8-inch wafer. 37 points were measured every 5 mm within a surface within a radius of 90 mm from the center, and the average value was taken as the average polishing rate (nm / min). Further, for the 37 polishing rates measured, the value obtained by dividing the standard deviation by the difference between the maximum value and the minimum value was defined as in-plane uniformity.

[Polishing Rate Fluctuation Rate] After polishing 200 wafers and measuring the average polishing rate for each wafer, it was calculated according to the following formula.
Polishing rate fluctuation rate (%) = {(maximum average polishing rate) − (minimum average polishing rate)} / (200th wafer average polishing rate) × 100.

[Amount of pad wear] The groove depth (D1) mm of the polishing pad after polishing 20 sheets with a depth gauge and the groove depth (D2) after polishing 200 sheets are measured, and from the dressing time (t) minutes by the dresser, according to the following formula Calculated.
Pad wear amount (μm / min) = (D1−D2) × 1000 / t
The life of the pad depends on the amount of wear of the pad and the groove depth. When the groove depth is the same, the life of the pad is longer when the amount of wear of the pad is smaller.

  [Number of Defects] As an enhancement treatment, a polished wafer is immersed in 0.5 wt% hydrofluoric acid for 10 minutes, washed with water, and then mixed with 1.0 wt% ammonia aqueous solution and 1.0 wt% hydrogen peroxide water. It was washed with a solution, washed with water and dried. For the cleaned wafer, the number of defects of 0.155 μm or more on the wafer was measured using a defect / foreign particle inspection apparatus (SP-1 manufactured by KLA Tencor).

(Comparative Example 1)
The raw material composition is charged into the first raw material tank and the second raw material tank of the RIM molding machine as shown below, and after loading nitrogen gas into the first raw material tank, the raw material composition is injected from both tanks into a mold and cured. Thus, a polyurethane molded body having a size of 750 mm × 750 mm and a thickness of 10 mm was obtained. The apparent density of the polyurethane was 0.82 g / cm ³ , and closed cells having an average cell diameter of 33 μm were formed.

<First raw material tank>
Polypropylene glycol 85 parts by weight 1,2-butanediol 15 parts by weight Tin octylate 0.5 parts by weight Silicone foam stabilizer 3 parts by weight Purified water 0.3 part by weight <Second raw material tank>
120 parts by weight of diphenylmethane diisocyanate.

Next, the following radical polymerizable composition was prepared at a weight ratio of the polyurethane molded product to the radical polymerizable composition of 100/140, and the polyurethane molded product was immersed at 20 ° C. for 7 days. The total amount of the composition was impregnated in the polyurethane molded body.
300 parts by weight of methyl methacrylate 0.8 parts by weight of azobisisobutyronitrile.

The polyurethane molded body swollen by impregnation was sandwiched between two glass plates via a vinyl chloride gasket, and the periphery was fixed and sealed, then heated at 70 ° C. for 5 hours, and then in a 100 ° C. oven for 3 hours. The polymer was cured by heating for a period of time. After releasing from between the glass plates, the weight was measured. Thereafter, drying was performed at 50 ° C. for 12 hours and subsequently at 100 ° C. for 12 hours. Furthermore, when it dried at normal temperature for 12 hours and measured immediately after that, there was no weight reduction before and after normal temperature drying. The central portion in the thickness direction of the impregnated cured product of the polyurethane molded product thus obtained was sliced and ground to a thickness of 2 mm. The apparent density of the radically polymerizable composition-impregnated cured product of the obtained polyurethane molded product was 0.80 g / cm ³ , and the average cell diameter of closed cells was 43 μm. On the surface, openings derived from 233 bubbles / mm ² bubbles were observed. The wet hardness was 51. The tensile elongation at break was 180%. A thermoplastic polyurethane (cushion layer thickness: 0.3 μm) manufactured by Nippon Matai Co., Ltd. having a strain constant of 0.15 × 10 ⁻⁴ μm / Pa as a cushion layer is applied to the polishing layer obtained by the above method, and a roll coater is used. It was laminated through a MA-6203 adhesive layer manufactured by Mitsui Chemicals Polyurethane Co., Ltd., and Sekisui Chemical Co., Ltd. double-sided tape 5604TDM was bonded to the back as a back tape. This laminated body was punched into a circle having a diameter of 508 mm, and a lattice-like groove with a width of 1.0 mm, a depth of 0.5 mm, and a pitch width of 30 mm was applied to one surface thereof. When the polishing evaluation was performed, the average polishing rate was 210 nm / min for the 20th sheet and 176 nm / min for the 200th sheet. The polishing rate fluctuation rate was 19%, the in-plane uniformity was 13.1%, and the number of defects was 710. The pad wear amount was 1.47 μm / min.

(Comparative Example 2 and Examples 1-9)
A polishing pad was prepared in exactly the same manner as in Comparative Example 1 except that each radical polymerizable composition was used as shown in Table 1. The methoxypolyethylene glycol methacrylate in Table 1 is a compound in which n is 9 and l is 0 in formula (3). Nonylphenol EO adduct acrylate is a compound in which r is 1 and s is 8 in formula (5). Furthermore, nonylphenol PO adduct acrylate is a compound in which r is 5 and s is 8 in formula (6).

  These physical properties and polishing characteristics are summarized in Table 2.

  As mentioned above, it is a polymer polymerized from an ethylenically unsaturated compound, comprising the compound represented by the formula (1) in the ethylenically unsaturated compound, and comprising a polyurethane. It can be seen that the polishing pad produced from the above has high elongation and is flexible, and the polishing pad using the polishing pad has fewer defects on the wafer surface and has a longer pad life.

  The polishing pad of the present invention can be used for polishing semiconductor substrates such as silicon wafers, optical members such as lenses, electronic materials such as magnetic heads and hard disks. In particular, it can be used as a polishing pad for polishing a semiconductor wafer as an object to be polished for the purpose of flattening the semiconductor wafer by chemical mechanical polishing (CMP) technology.

Claims (10)

A composition comprising a polymer polymerized from an ethylenically unsaturated compound and polyurethane, and a compound represented by the formula (1) as the ethylenically unsaturated compound.

(R ¹ and R ³ are hydrogen, R ² is hydrogen or an alkyl group, and R ⁴ is an organic group containing a structure in which six or more carbon atoms or oxygen atoms are connected in a straight chain.) The composition according to claim 1, wherein in the formula (1), R ⁴ is an organic group containing a structure in which nine or more carbon atoms or oxygen atoms are connected in a straight chain. The composition according to claim 1 or 2, wherein the compound represented by the formula (1) is a compound represented by any one of the formulas (2) to (6).

(In the formulas (2) to (6), m is an integer of 5 or more, n and l are integers satisfying “n is 1 and 1 is 2 or more” or “n is 2 or more and l is 0 or more”, p And q are integers satisfying “p is 1 and q is 1 or more” or “p is 2 or more and q is 0 or more”, and r and s are “r is 1 and s is 5 or more” or “r is 2 And an integer satisfying “s is 0 or more”.) The composition according to any one of claims 1 to 3, wherein the content of the compound represented by the formula (1) in the ethylenically unsaturated compound is 3 to 60% by weight. The composition according to any one of claims 1 to 3, wherein the content of the compound represented by the formula (1) in the ethylenically unsaturated compound is 10 to 60% by weight. A step of immersing polyurethane in a radical polymerizable composition containing an ethylenically unsaturated compound and a radical polymerization initiator, and polymerizing the ethylenically unsaturated compound in a swollen state of the polyurethane impregnated with the radical polymerizable composition And a process for producing a composition comprising the compound represented by the formula (1) as the ethylenically unsaturated compound.

(R ¹ and R ³ are hydrogen, R ² is hydrogen or an alkyl group, and R ⁴ is an organic group containing a structure in which six or more carbon atoms or oxygen atoms are connected in a straight chain.) The method for producing a composition according to claim 6, wherein in the formula (1), R ⁴ is an organic group containing a structure in which nine or more carbon atoms or oxygen atoms are connected in a straight chain. The method for producing a composition according to claim 1 or 2, wherein the compound represented by the formula (1) is a compound represented by any one of the formulas (2) to (6).

(In the formulas (2) to (6), m is an integer of 5 or more, n and l are integers satisfying “n is 1 and 1 is 2 or more” or “n is 2 or more and l is 0 or more”, p And q are integers satisfying “p is 1 and q is 1 or more” or “p is 2 or more and q is 0 or more”, and r and s are “r is 1 and s is 5 or more” or “r is 2 And an integer satisfying “s is 0 or more”.)   The method for producing a composition according to any one of claims 6 to 8, wherein the content of the compound represented by the formula (1) in the ethylenically unsaturated compound is 3 to 60% by weight.   The polishing pad obtained using the composition in any one of Claims 1-5.