JP5250934B2 - Improved polishing pad manufacturing method - Google Patents

Description

  The present invention relates to an interpenetrating polymer network structure and a method for producing the same. The present invention also relates to a polishing pad for a semiconductor substrate and a method for manufacturing the same. In particular, the present invention relates to a polishing pad manufacturing method for flattening the surface of an insulating layer or metal wiring formed on a semiconductor substrate such as silicon.

  A polishing pad containing a polymer polymerized from polyurethane and a vinyl compound is disclosed in Patent Document 1. Further, Patent Document 2 discloses a method for producing a polishing pad produced from a step of causing a monomer polymerization reaction after immersing a polymer molded body in a solution containing a monomer for polymerization.

However, in the production of these polishing pads, the monomer polymerization reaction starts during the immersion and impregnation of the polymer molded body, and the viscosity increases, so the impregnation rate into the polymer molded body is slow. Therefore, there is a problem that the time required for the production becomes long. In order to avoid such an increase in viscosity, (1) it was necessary to set the impregnation temperature low, and the impregnation time required a long time because of low temperature impregnation. Furthermore, (2) the solution of the polymerization monomer was added with an organic solvent so that the impregnation rate did not decrease greatly even when the viscosity increased. Therefore, the unnecessary organic solvent was removed after the completion of polymerization. The process to do was necessary.
International Publication No. 00/122621 Pamphlet JP 2000-218551 A

  An object of the present invention is to provide an interpenetrating polymer network structure excellent in uniformity of mechanical properties such as tensile strength and tensile elongation, shortened in manufacturing time and manufacturing process, and high in manufacturing efficiency, and a manufacturing method thereof. There is to do. Another object of the present invention is to provide a polishing pad having high in-plane uniformity at the time of polishing, improving the pad life at the time of polishing, shortening the manufacturing time and the manufacturing process, and having high manufacturing efficiency, and a manufacturing method thereof. There is.

  A step of immersing the polymer molding in a radical polymerizable composition comprising an ethylenically unsaturated compound and a radical polymerization initiator, and the ethylene in a swollen state of the polymer molding impregnated with the radical polymerizable composition A method of producing an interpenetrating polymer network structure comprising the step of polymerizing a polymerizable unsaturated compound, wherein the ethylenically unsaturated compound is a methacrylic acid ester or an acrylic acid ester, and the polymer molding is a polyurethane The radical polymerizable composition is substantially free of an organic solvent, and the radical polymerization inhibitor is added before the step of immersing the polymer molded body in the radical polymerizable composition. An interpenetrating polymer network structure characterized by being added to the radical polymerizable composition and / or the polymer molded body. Method.

  As a result of examining the shortening of the production time and the production process, the inventors of the present invention can suppress / eliminate the increase in the viscosity of the monomer for polymerization by using a specific compound during the polymerization, and can impregnate at a higher temperature. Therefore, it was found that not only the time required for impregnation can be shortened, but also the process for removing the organic solvent can be omitted, so that the time required for manufacturing the entire process can be greatly shortened. Further, the obtained structure has uniform mechanical properties, and when used as a polishing pad, the in-plane uniformity is high and the pad life is improved.

  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. Further, a structure in which different polymers are in a continuous phase with each other may be stabilized by cross-linking point formation.

  The interpenetrating polymer network structure has an interpenetrating polymer network structure from a production method in which a polymer molded body is immersed in a radical polymerizable composition and an ethylenically unsaturated compound in the radical polymerizable composition is polymerized. It is clear. The polishing pad of the present invention comprises an interpenetrating polymer network structure. In the present invention, the interpenetrating polymer network produced by adding a radical polymerization inhibitor is excellent in uniformity of mechanical properties such as tensile strength and tensile elongation, and the interpenetrating polymer network is further used as a polishing pad. The reason why the in-plane uniformity at the time of polishing is high and the pad life at the time of polishing is improved is not always clear, but when a radical polymerization inhibitor is added, the start time of the polymerization reaction is the reaction system. Uniform throughout, the process from the start to the end of the polymerization reaction is almost the same throughout the reaction system, resulting in less variation in mechanical properties and polishing properties of the reaction cured product, stable and highly uniform It is assumed that an interpenetrating polymer network structure and a polishing pad are obtained.

  The ethylenically unsaturated compound in the present invention refers to a compound having a radical polymerizable carbon-carbon double bond. Specifically, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, isodecyl methacrylate, n-lauryl methacrylate, tridecyl methacrylate, n-stearyl methacrylate, 2-hydroxyethyl methacrylate 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, methacrylic acid, glycidyl methacrylate, tetrahydrofurfuryl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, 2-phenoxyethyl methacrylate, isobornyl methacrylate, polyethylene Methacrylic acid ester such as recall monomethacrylate, polypropylene glycol monomethacrylate, isoamyl acrylate, lauryl acrylate, stearyl acrylate, phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, isobornyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, Acrylic acid esters such as trimethylolpropane trimethacrylate, neopentyl glycol diacrylate, 3-methyl-1,5-pentanediol diacrylate, 1,6-hexanediol diacrylate, 2-butyl-2-ethyl-1, 3-propanediol diacrylate, 1,9-nonane diacrylate, dimethylol tricyclodecane diacrylate , It may be mentioned trimethylolpropane triacrylate, pentaerythritol tetraacrylate, etc. polyfunctional ethylenically unsaturated compound having two or more ethylenically unsaturated bonds in one molecule, and the like.

  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 such as 4′-azobis (4-cyanovaleric acid), 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), etc. Polymerization initiator, cumene hydroperoxide, t-butyl hydroperoxide, dicumyl peroxide, di-t-butyl peroxide, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobuty Rate, t-butyl peroxybivalate, t-butyl peroxybenzoate, t-butyl peroxyacetate, diisopropyl peroxydicarbonate , It may be mentioned di -s- butyl peroxydicarbonate, benzoyl peroxide, acetyl peroxide, lauroyl peroxide, a peroxide polymerization initiator such as. The amount of radical polymerization initiator added is preferably 0.01 to 5% by weight, more preferably 0.05 to 3% by weight, based on the ethylenically unsaturated compound.

  The radical polymerization inhibitor of the present invention is a compound having high reactivity with radicals in the radical polymerization reaction system, and reacts with radicals to produce inactive products.

  Specifically, phenol compounds such as hydroquinone, hydroquinone monomethyl ether, topanol A, catechol, t-butylcatechol, 2,6-di-t-butyl-4-methylphenol, phenothiazine, bis (α-methylbenzyl) Phenothiazine compounds such as phenothiazine, 3,7-dioctylphenothiazine, bis (α, α-dimethylbenzyl) phenothiazine, p-nitrosophenol, N-nitrosodiphenylamine, ammonium salt of N-nitrosophenylhydroxyamine (cuperon), etc. Nitroso compounds, diphenylamine, N, N′-diphenyl-p-phenylenediamine, α-naphthylamine, phenyl-β-naphthylamine, N, N′-di-sec-butyl-p-phenylenediamine, p-phenyle Amine compounds such as diamine, 6-ethoxy-2,2,4-triethyl-1,2-dihydroquinoline, N-phenyl-N′-isopropyl-p-phenylenediamine, 4,4′-dioctyl-diphenylamine, Metal salt compounds such as copper salts or manganese salts such as dimethyldithiocarbamic acid, diethyldithiocarbamic acid, dipropyldithiocarbamic acid, dibutyldithiocarbamic acid, diphenyldithiocarbamic acid, formic acid, acetic acid, octanoic acid, naphthenic acid, ethylenediaminetetraacetic acid, etc. Can be mentioned. One or two or more compounds selected from these compounds can be used. The addition amount of the radical polymerization inhibitor of the present invention is preferably 0.001 to 0.5% by weight, more preferably 0.001 to 0.3% by weight, based on the ethylenically unsaturated compound.

  In the interpenetrating polymer network structure of the present invention, it is essential to add a radical polymerization inhibitor during production. The radical polymerization inhibitor may be used by being added to the radical polymerizable composition. Moreover, you may add beforehand at the time of polymer molded object manufacture. Furthermore, you may make it contain in both a radically polymerizable composition and a polymer molded object. There may be one kind of radical polymerization inhibitor, or two or more kinds. When a radical polymerization inhibitor is used for both the radical polymerizable composition and the polymer molded article, 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 radical polymerization inhibitors that are preferably impregnated and / or polymerized in the presence of oxygen gas or oxygen-containing gas include phenothiazine, hydroquinone, hydroquinone monomethyl ether, t-butylcatechol, phenyl-β-naphthylamine, and p-phenylenediamine. Can be mentioned.

  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 radically polymerizable composition is preferably a composition that does not substantially contain an organic solvent from the viewpoint that an organic solvent removing step becomes unnecessary. The organic solvent as used herein refers to an organic compound that is liquid at room temperature and does not substantially react during the polymerization of the ethylenically unsaturated compound. Specific examples include hexane, dimethylformamide, dimethyl sulfoxide, ethanol and methanol. “Substantially free of organic solvent” means that the organic solvent is less than 1% by weight based on the ethylenically unsaturated compound.

  The radically polymerizable composition of the present invention contains the ethylenically unsaturated compound and the radical polymerization initiator. You may contain a radical polymerization inhibitor, antioxidant, anti-aging agent, a filler, a coloring agent, an antifungal agent, an antibacterial agent, a flame retardant, and an ultraviolet absorber. Antioxidants, anti-aging agents, fillers, colorants, antifungal agents, antibacterial agents, flame retardants, compounds that are effective as UV absorbers, those that are solid at room temperature, those that contain inorganic elements, It does not correspond to the organic solvent here. The amount of these compounds added is preferably within a range not exceeding 3% by weight based on the ethylenically unsaturated compound.

  The polymer molded body of the present invention refers to a polymer substance that is solid at room temperature. The molded body may be solid, hollow or foamed. The characteristics are not particularly limited, but it is necessary that the composition can be taken into the molded body and impregnated by being immersed in the radical polymerizable composition. Therefore, it is necessary to be made of a material having an affinity for the radical polymerizable composition, and to be flexible enough to take in the radical polymerizable composition and swell the polymer molded body itself. As the polymer molded body, a polymer molded body containing a polyethylene glycol chain, a polypropylene glycol chain, and a polytetramethylene glycol chain as a chemical structure that is flexible and can be swollen by a radically polymerizable composition is preferable. Specific examples include polyester and polyurethane. Although depending on the apparent density of the radically polymerizable composition, the volume of the polymer molded body swells to about 1.03 to 5 times the original volume by impregnation, and about 1.5 to 3 times the original volume. Swells.

As a form of the polymer molded body, a foam containing closed cells having an average cell diameter of 10 to 120 μm is preferable, and a foam containing closed cells of 20 to 60 μm is more preferable. The average bubble diameter is determined by observing the surface or slice surface of the polymer molded body with a laser microscope, scanning electron microscope, etc., and processing the image for all the bubbles in the image. The diameter distribution can be determined. From this data, the average bubble diameter and the number of bubbles per unit area can be calculated. Moreover, as an apparent density of a polymer molded object, 0.1-1.2 g / cm < ³ > is preferable and 0.5-1.0 g / cm < ³ > is more preferable. The apparent density can be measured by the method described in Japanese Industrial Standard JIS K 7112.

Furthermore, the radically polymerizable composition incorporated into the polymer molded body does not enter the bubbles in the polymer molded body, and the polymer is molded after polymerization of the ethylenically unsaturated compound under the swelling state of the polymer molded body. It is preferable that the body bubbles remain as bubbles. 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 polymer molded body of the present invention is particularly preferably a polyurethane molded body obtained by mixing two liquids of polyol and polyisocyanate. Here, the polyol refers to a compound having two or more hydroxyl groups. Examples thereof include one or a mixture of two or more selected from polyether polyol, polyester polyol, polycarbonate polyol, polycaprolactone polyol, ethylene glycol, propylene glycol, glycerin and the like. 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. In preparation of the polymer molded body, in addition to polyol and polyisocyanate, crosslinking agent, chain extender, foam stabilizer, foaming agent, resination catalyst, foaming catalyst, antioxidant, anti-aging agent, filler, It may contain a plasticizer, a colorant, an antifungal agent, an antibacterial agent, a flame retardant, and an ultraviolet absorber, and may be molded. Although the preparation method of a polymer molded object is not specifically limited, It can prepare by methods, such as injection molding and reaction injection 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 between the polymer molded body and the polymer polymerized from the impregnated ethylenically unsaturated compound is preferably 100/5 to 100/300, more preferably 100/50 to 100/200. Advantages of impregnation / polymerization when the weight ratio of the polymer molded from the polymer unsaturated polymer to be impregnated is smaller than 100/5, and the characteristics are not much different from those of the polymer molded product alone. Is small. On the other hand, when the weight ratio between the polymer molded body and the polymer polymerized from the ethylenically unsaturated compound to be impregnated is larger than 100/300, it is not preferable because the time required for impregnation becomes too long. The step of immersing the polymer molded body in the radical polymerizable composition is preferably 3 hours to 20 days at a temperature of 15 to 60 ° C., more preferably 3 hours to 10 days.

The polishing pad of the present invention preferably has closed cells having an average cell diameter of 10 to 120 μm, and more preferably has closed cells of 20 to 60 μm. 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 density can be measured by the method described in Japanese Industrial Standard JIS K 7112.

  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, which is an object to be polished, for the purpose of planarizing the 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.

  The polishing pad of the present invention can be used for polishing optical members such as optical lenses, optical prisms, optical filters, and optical waveguides. Examples of the material of the optical member to be polished include glass, quartz, crystal, sapphire, transparent resin, lithium tantalate, and lithium niobate.

  In other applications, it can be used for polishing gallium arsenide, gallium phosphide, indium phosphide, ferrite, alumina, silicon carbide, silicon nitride, ceramics, alloys, resins, and the like.

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

  [Average bubble diameter] The surface or sliced surface of the polishing pad was observed at a magnification of 200 times with a scanning electron microscope “SEM2400” (Hitachi), and the image was analyzed with an image processing apparatus. The bubble diameter was measured, and the average value was taken as the average bubble diameter.

  [Density] Measured using a pycnometer (Harvard type) according to the method described in JIS K7112.

[Tensile Test] Using a tensile tester RTM-100 (manufactured by Orientec Co., Ltd.), breaking strength and breaking elongation were measured under the following measurement conditions. The average value of the five test pieces was taken as the measured value.
Test room temperature: 23 ° C
Test room humidity: 50%
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] “Suba400” (manufactured by Rodel Nitta Co., Ltd.) was used as a cushion layer, and was bonded to a polishing pad to be evaluated with a double-sided adhesive tape to produce a laminated polishing pad. The laminated polishing pad was affixed on the surface plate of the polishing apparatus, and the diamond conditioner was pressed and rotated in the same direction as the polishing surface plate at a pressure of 0.06 MPa, a polishing surface plate rotation speed of 34 rpm, and a conditioner rotation speed of 32 rpm. The polishing pad was conditioned for 5 minutes while supplying purified water onto the polishing pad at a rate of 100 mL / min.

  A 6-inch silicon wafer for evaluation was mounted on a polishing head of a polishing apparatus, rotated at 42 rpm, a laminated polishing pad was fixed to a platen of a polishing machine, and rotated at 42 rpm in the same direction as the rotation direction of the polishing head. While supplying the slurry at 150 mL / min, polishing was performed at a polishing pressure of 0.05 MPa for 1 minute, and the polishing rate of the oxide film was measured. The wafer surface was washed with a polyvinyl alcohol sponge while supplying purified water immediately without drying the wafer surface, and dried by blowing dry compressed air.

Ten wafers for evaluation were polished, and the 10th oxide film polishing rate was measured. Then, polishing was performed, and the 100th oxide film polishing rate was measured.
Polishing rate: Polishing amount per unit time (polishing rate) by measuring wafer thickness before and after polishing with optical interference film pressure measuring device “Lambda Ace” VM-8000J (manufactured by Dainippon Screen Mfg. Co., Ltd.) Was calculated. An evaluation test wafer in which a thermal silicon oxide film was formed on a 6-inch silicon wafer at about 10,000 angstroms was used.

[In-plane uniformity] The polishing rate was measured at 49 points in the diameter direction of the wafer, and the value obtained by dividing the difference between the maximum and minimum values by twice the average value of 49 points was multiplied by 100 to obtain the in-plane uniformity ( %).
In-plane uniformity (%) = (MAX−MIN) × 100/2 × AV
(Comparative Example 1)
The following raw material compositions were charged into the first raw material tank and the second raw material tank of the RIM molding machine, respectively, poured into a mold, and cured to obtain a polyurethane molded body of 850 mm × 850 mm and thickness 12 mm. The apparent density of the polyurethane molded product was 0.77 g / cm ³ , and closed cells having an average cell diameter of 32 μm were observed.
<First raw material tank>
Polypropylene glycol 85 parts by weight Diethylene glycol 15 parts by weight Triethylamine 1 part by weight Tin octylate 0.5 part 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 is prepared, and the weight ratio of the polyurethane molded product to the radical polymerization composition is 100/160 (the organic solvent component is removed after curing, so polyurethane molding) When the polyurethane molded body was observed after being immersed for 3 days at 20 ° C., the total amount of the radical polymerizable composition was still in the polyurethane molded body. Since it was not soaked, soaking was continued. When immersed for a further 7 days at 20 ° C. for a total of 7 days, the entire amount of the radical polymerizable composition was impregnated in the polyurethane molded product.
Methyl methacrylate 300 parts by weight Azobisisobutyronitrile 1.5 parts by weight n-decane 100 parts by weight The polyurethane molded body swollen by impregnation was sandwiched between two glass plates through a vinyl chloride gasket, and the periphery was fixed. And then cured by heating in a 70 ° C. water bath for 5 hours, followed by heating in a 100 ° C. oven for 3 hours. After the impregnated cured product of the polyurethane molded product was released from the glass plate, it was vacuum-dried at 50 ° C. for 12 hours and then at 100 ° C. for 12 hours to remove components that can be removed under reduced pressure. A central part in the thickness direction of the impregnated cured product of the polyurethane molded body was sliced and surface-ground to obtain a sheet having a thickness of 2 mm. A No. 1 small test piece was punched out from the center of this sheet, and the tensile strength and tensile elongation were measured to be 10.3 MPa and 260%, respectively. Further, No. 1 small test piece was punched out from the end of this sheet, and the tensile strength and tensile elongation were measured and found to be 9.2 MPa and 190%, respectively. Then, after punching out into a circle with a diameter of 600 mm, it was ground to a thickness of 2 mm, and a grid-like groove having a width of 2 mm, a depth of 0.6 mm, and a pitch of 40 mm was formed on one surface to prepare a polishing pad. The apparent density of the radically polymerizable composition-impregnated cured product of the polyurethane molded product was 0.80 g / cm ³ , and the average cell diameter of closed cells was 39 μm. Openings derived from 350 bubbles / mm ² bubbles were observed on the surface.

  As a result of polishing evaluation, the polishing rates of the first and tenth sheets were 1700 Å / min and 1650 Å / min, respectively, and the in-plane uniformity was 16% and 17%, respectively. The polishing rate after polishing 100 sheets was 1400 Å / min, and the in-plane uniformity was 28%.

(Comparative Example 2)
Except that the impregnation condition was 60 ° C., the polyurethane molded body was immersed in the radical polymerizable composition for 5 hours in exactly the same manner as in Comparative Example 1, and the curing proceeded before the radical polymerizable composition was completely impregnated, The polyurethane molded product and the cured product of the radical polymerizable composition were not integrated.

Example 1
The following radical polymerizable composition was prepared, and the polyurethane molded body produced in Comparative Example 1 was immersed at 40 ° C. for 3 days in a weight ratio of 100/120 of the polyurethane molded body and the radical polymerizable composition. The entire amount of the polymerizable composition was impregnated in the polyurethane molded body.
Methyl methacrylate 300 parts by weight Azobisisobutyronitrile 1.5 parts by weight 2,6-di-t-butyl-4-methylphenol
0.2 parts by weight A polyurethane molded body swollen by impregnation was sandwiched between two glass plates via a vinyl chloride gasket, the periphery was fixed and sealed, and then heated in a 70 ° C. water bath for 5 hours, followed by Cured by heating in a 100 ° C. oven for 3 hours. The impregnated cured product of the polyurethane molded product was released from the glass plate, and then the central portion in the thickness direction of the impregnated cured product of the polyurethane molded product was sliced and surface ground to obtain a sheet having a thickness of 2 mm. A No. 1 small test piece was punched out from the center of this sheet, and the tensile strength and tensile elongation were measured to be 10.3 MPa and 260%, respectively. Further, a No. 1 small test piece was punched from the end of this sheet, and the tensile strength and tensile elongation were measured and found to be 10.2 MPa and 260%, respectively. After punching out into a circle having a diameter of 600 mm, it was ground to a thickness of 2 mm, and a grid-like groove having a width of 2 mm, a depth of 0.6 mm, and a pitch of 40 mm was formed on one surface to prepare a polishing pad. The apparent density of the radically polymerizable composition-impregnated cured product of the polyurethane molded product was 0.80 g / cm ³ , and the average cell diameter of closed cells was 39 μm. Openings derived from 350 bubbles / mm ² bubbles were observed on the surface.

  When the polishing evaluation was performed, the polishing rates of the first and tenth sheets were 1700 Å / min and 1650 Å / min, respectively, and the in-plane uniformity was 8% and 8%, respectively. The polishing rate after polishing 100 sheets was 1700 Å / min, and the in-plane uniformity was 8%.

(Example 2)
The following raw material compositions were charged into the first raw material tank and the second raw material tank of the RIM molding machine, respectively, poured into a mold, and cured to obtain a polyurethane molded body of 850 mm × 850 mm and thickness 12 mm. The apparent density of the polyurethane molded product was 0.77 g / cm ³ , and closed cells having an average cell diameter of 32 μm were observed.
<First raw material tank>
Polypropylene glycol 85 parts by weight Diethylene glycol 15 parts by weight Triethylamine 1 part by weight Tin octylate 0.5 part by weight Silicone foam stabilizer 3 parts by weight Purified water 0.3 part by weight 2,6-di-t-butyl-4-methylphenol
0.1 parts by weight <second raw material tank>
120 parts by weight of diphenylmethane diisocyanate Next, the following radical polymerizable composition was prepared, and the polyurethane molded body was immersed at 40 ° C. for 3 days in a weight ratio of 100/120 of the polyurethane molded body and the radical polymerizable composition. As a result, the entire amount of the radical polymerizable composition was impregnated in the polyurethane molded product.
Methyl methacrylate 300 parts by weight Azobisisobutyronitrile 1.5 parts by weight 2,6-di-t-butyl-4-methylphenol
0.1 parts by weight The polyurethane molded body swollen by impregnation was sandwiched between two glass plates via a vinyl chloride gasket, the periphery was fixed and sealed, and then heated in a 70 ° C. water bath for 5 hours, followed by Cured by heating in a 100 ° C. oven for 3 hours. The impregnated cured product of the polyurethane molded product was released from the glass plate, and then the central portion in the thickness direction of the impregnated cured product of the polyurethane molded product was sliced and surface ground to obtain a sheet having a thickness of 2 mm. A No. 1 small test piece was punched out from the center of this sheet, and the tensile strength and tensile elongation were measured to be 10.3 MPa and 260%, respectively. Further, a No. 1 small test piece was punched from the end of this sheet and measured for tensile strength and tensile elongation, which were 10.3 MPa and 260%, respectively. After punching out into a circle having a diameter of 600 mm, it was ground to a thickness of 2 mm, and a grid-like groove having a width of 2 mm, a depth of 0.6 mm, and a pitch of 40 mm was formed on one surface to prepare a polishing pad. The apparent density of the radically polymerizable composition-impregnated cured product of the polyurethane molded product was 0.80 g / cm ³ , and the average cell diameter of closed cells was 39 μm. An opening derived from 350 mm ² bubbles was observed on the surface.

  When the polishing evaluation was performed, the polishing rates of the first and tenth sheets were 1700 angstrom / min and 1700 angstrom / min, respectively, and the in-plane uniformity was 8% and 8%, respectively. The polishing rate after polishing 100 sheets was 1700 Å / min, and the in-plane uniformity was 7%.

(Example 3)
A polyurethane molded body was obtained in the same manner as in Example 1 except that the raw material composition charged in the first raw material tank was changed as follows. The apparent density of the polyurethane molded product was 0.77 g / cm ³ , and closed cells having an average cell diameter of 32 μm were observed.
<First raw material tank>
Polypropylene glycol 85 parts by weight Diethylene glycol 15 parts by weight Triethylamine 1 part by weight Tin octylate 0.5 part by weight Silicone foam stabilizer 3 parts by weight Purified water 0.3 part by weight t-butylcatechol 0.3 part by weight Next, When a radical polymerizable composition was prepared and the polyurethane molded product was immersed at 60 ° C. for 5 hours, the entire amount of the radical polymerizable composition was impregnated in the polyurethane molded product.
Methyl methacrylate 300 parts by weight Azobisisobutyronitrile 0.8 parts by weight Hydroquinone monomethyl ether
0.3 parts by weight The polyurethane molded body swollen by impregnation was sandwiched between two glass plates via a vinyl chloride gasket, the periphery was fixed and sealed, and then heated in a 70 ° C. water bath for 5 hours. Cured by heating in a 100 ° C. oven for 3 hours. After the impregnated cured product of the polyurethane molded product is released from the glass plate, it is punched into a circle having a diameter of 600 mm, and then ground to a thickness of 2 mm. Then, a polishing pad was produced. The apparent density of the radically polymerizable composition-impregnated cured product of the polyurethane molded product was 0.80 g / cm ³ , and the average cell diameter of closed cells was 39 μm. Openings derived from 350 bubbles / mm ² bubbles were observed on the surface.

  When a 6-inch silicon wafer on which a silicon oxide film of about 10,000 angstroms was formed was polished for 10 minutes by applying a silica-based polishing slurry, the polishing rate of the silicon oxide film was 1800 angstroms / minute and the in-plane uniformity was 8%. It was. Even after 100 sheets, a polishing rate of 1750 Å / min and in-plane uniformity of 8% were obtained, and the decrease was small.

From the above, pad physical properties such as apparent density and average cell diameter of closed cells are equivalent, and the time required for impregnation is greatly reduced if a polymerization inhibitor is added to the radical polymerization composition and / or polymer molding. In addition, the process of removing the organic solvent is unnecessary, and the production efficiency can be improved. In addition, the polishing pad obtained by using a polymerization inhibitor has uniform tensile strength and tensile elongation in the pad, excellent in-plane uniformity during polishing, and uniform polishing rate and in-plane even in continuous polishing. It was also confirmed that the performance of the pad was good and the performance worthy of practical use was obtained.
Example 4
Using the polyurethane raw material composition of Comparative Example 1, a polyurethane molded product having closed cells with an apparent density of 0.41 g / cm ³ and an average cell diameter of 80 μm was obtained.

Next, the following radical polymerizable composition was prepared at a weight ratio of 100/40 between the polyurethane molded product and the radical polymerization composition, and the polyurethane molded product was immersed at 20 ° C. for 8 hours. The entire product was impregnated in a polyurethane molded product.
Methyl methacrylate 300 parts by weight Azobis (2-methylbutyronitrile) 2.0 parts by weight t-butylcatechol 0.3 part by weight A polyurethane molded body swollen by impregnation is sandwiched between two glass plates via a vinyl chloride gasket. After sandwiching, fixing the periphery and sealing, the mixture was heated at 70 ° C. for 3 hours, and then cured by heating in a 100 ° C. oven for 2 hours.

  From the relaxation time measurement by the solid state NMR (nuclear magnetic resonance) method of the radically polymerizable composition-impregnated cured product of the polyurethane molded product, it had a structure in which polyurethane and polymethyl methacrylate were dispersed in the order of several nanometers or less. From this, it was confirmed that two polymer chains of polyurethane and polymethylmethacrylate entered each other, and the entanglement of the polymer chains occurred.

A central part in the thickness direction of the impregnated cured product of the polyurethane molded body was sliced and surface-ground to obtain a sheet having a thickness of 1 mm. When a 3 mm square test piece was punched from the center of this sheet and a blood compatibility test was performed by the platelet adhesion test according to the following procedure, platelet adhesion was not observed and the entire surface was clean.
(Platelet adhesion test)
A test piece and phosphate buffered saline were added to an Eppendorf tube and stored at 4 ° C. After heparin-collected rat blood was centrifuged at 2500 rpm for 10 minutes at 20 ° C., 3.0 mL of the upper layer was collected, and 90 μL of 0.1 M CaCl ₂ was added to 6 mL of Ca-containing phosphate buffered saline. ) Was added and mixed, and immediately poured into phosphate buffered saline containing the test piece. Then, it stirred for 60 minutes at 37 degreeC using the rotator. After washing twice with 1 mL of phosphate buffered saline, 1 mL of 10% formalin solution was added, stirred at room temperature for 1 hour, and stored at 4 ° C.

  Next, after Pt vapor deposition, SEM (scanning electron microscope) observation was performed. The number of platelets on any 5 screens was counted at a magnification of 1000 times (93 × 105 μm), and the number of platelets per unit area was calculated.

(Comparative Example 3)
In Example 4, a 3 mm square test piece was prepared in the same manner as in Example 4 except that the following radical polymerizable composition was used, and a platelet adhesion test was performed. Of the 5 screens of the SEM photograph, adhesion of platelets was recognized on 2 screens (5 / screen). On the other hand, platelet adhesion was not observed on the other three screens (0 / screen). When the radical polymerization inhibitor was not used, there was a non-homogeneous part on the surface of the test piece, and platelet adhesion was observed.

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 a chemical mechanical polishing (CMP) technique.

Claims (4)

Ethylenically unsaturated compounds, wherein the ethylene under the swollen state of the radical polymerization initiator, a radical polymerizable step of dipping the polymer molded article to the composition, and the radical polymerizable composition polymer molded body impregnated with consisting A method of producing an interpenetrating polymer network structure comprising the step of polymerizing a polymerizable unsaturated compound, wherein the ethylenically unsaturated compound is a methacrylic acid ester or an acrylic acid ester, and the polymer molding is a polyurethane a molded body, the radical polymerizable composition are those substantially free of organic solvents, before the step of immersing the polymer-extruded article to the radical polymerizable composition, the radical polymerization inhibitor is Made in interpenetrating polymer network structure, characterized in that it is added to the radical polymerizable composition and / or the polymer moldings Method. A method for producing a polishing pad, comprising the method for producing an interpenetrating polymer network structure according to claim 1 . Wherein the weight ratio of polymer produced from the ethylenically unsaturated compound impregnated with a polymeric molded article, the production method of the polishing pad according to claim 2 is 100 / 5-100 / 300. The method for producing a polishing pad according to claim 2 or 3 , wherein the apparent density of the polymer molded body is 0.1 to 1.2 g / cm ³ .