JP5176639B2 - Polishing pad - Google Patents

Description

The present invention also relates to Migaku Ken pad. In particular, the present invention relates to a polishing pad for polishing and flattening an interlayer insulating film and a metal film for forming a metal wiring formed on a semiconductor substrate such as silicon.

  A polishing pad made of 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 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. However, in these polishing pads, a metal thin film such as copper is polished to form fine wiring, and in the wiring-insulator flattening step, the central portion of the metal wiring is thinner than the edge, so-called “Dishing” is noticeable. The larger the dishing, the smaller the cross-sectional area of the wiring, which is not preferable because the electrical resistance of the metal wiring increases. Moreover, it is not preferable because it causes a polishing residue when an upper wiring layer is formed. Furthermore, it has been desired to improve the polishing rate and extend the life of the pad.

On the other hand, as a polishing pad having a high polishing rate and excellent in-plane uniformity, a polishing pad composed of water-soluble particles such as cyclodextrin (hydroxyl group-containing compound) and a water-insoluble matrix is disclosed in Patent Document 3. Further, as a polishing pad that can reduce defects during polishing, Patent Document 4 discloses a polishing pad in which microspheres such as polyvinyl alcohol, various celluloses, and polyhydroxyethyl acrylate (all of which contain a hydroxyl group-containing compound) are dispersed. . Although these polishing pads are composed of a polymer material containing a hydroxyl group, they are limited to water-soluble particles and microspheres, and the polishing pad has a surface on which solute components and suspended matters in the slurry are difficult to adhere and deposit. In addition, a large number of particles were observed on the polished wafer and scratches were generated in some cases, so that the characteristics during polishing were insufficient.
International Publication No. 00/012262 Pamphlet JP 2000-218551 A Japanese Patent Laid-Open No. 11-322877 JP 2003-011066 A

  An object of the present invention is to provide an interpenetrating network structure having a surface on which solute components and suspended substances are difficult to adhere and deposit, and a method for manufacturing the same. Another object of the present invention is to provide a polishing pad having a high polishing rate, reduced dishing, and extended pad life during polishing.

In order to solve the above problems, the present invention has the following constitutions: (1) An ethylenically unsaturated compound polymer having a hydroxyl group and polyurethane are each contained as an independent network structure, and the water absorption at 23 ° C. is 10% or more. A polishing pad comprising an interpenetrating polymer network structure characterized by that.

( 2 ) The polishing pad according to ( 1 ), wherein the polishing pad is used for polishing a semiconductor substrate.

  An interpenetrating polymer network having a surface on which solute components and suspended matters in the slurry are difficult to adhere and deposit can be obtained. In addition, a polishing pad having a high polishing rate and an extended pad life can be obtained.

  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. 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 forms an interpenetrating polymer network structure from a manufacturing method in which a polymer molding is immersed in a radically polymerizable composition and the ethylenically unsaturated compound in the radically polymerizable composition is polymerized. can do. The polishing pad of the present invention comprises an interpenetrating polymer network structure.

  The interpenetrating polymer network structure of the present invention includes an ethylenically unsaturated compound polymer having a hydroxyl group. Polishing pads composed of a polymer material containing a hydroxyl group have existed in the past, but the affinity between the polymer material containing a hydroxyl group and other polymer materials is low and the dispersibility is poor. Focusing on the inability to obtain compatibility, the inventors have found that a desired effect can be obtained by including an ethylenically unsaturated compound polymer having a hydroxyl group.

  In the present invention, the reason why the interpenetrating polymer network structure containing an ethylenically unsaturated compound polymer having a hydroxyl group is difficult to adhere and deposit solute components and suspended solids and has a high water absorption rate is not necessarily clear. It is presumed that the high-order polymer structure of the molecular network structure suppresses adhesion / deposition of solute components and suspended solids, and has excellent rigidity and resistance to thermal deformation. As a result, the polishing pad using this interpenetrating polymer network structure prevents the solute component and suspended matter in the slurry from adhering to and accumulating on the pad surface during polishing, so that the pad surface is always stable. It seems that the surface is formed, and it is difficult for the polishing rate to decrease and the life to be shortened.

  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, Monofunctional ethylenically unsaturated compounds such as acrylic ester, acrylonitrile, methacrylonitrile, styrene, α-methylstyrene, hydroxystyrene, α-methylstyrene dimer, vinylpyridine, ethyleneimine, etc., ethylene glycol dimethacrylate, 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 tricyclode And polyfunctional ethylenically unsaturated compounds having two or more ethylenically unsaturated bonds in one molecule, such as candiacrylate, trimethylolpropane triacrylate, and pentaerythritol tetraacrylate.

  Specific examples of the ethylenically unsaturated compound having a hydroxyl group in the present invention include 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate, glycerol mono Methacrylate, polyethylene glycol monomethacrylate, polypropylene glycol monomethacrylate, polyethylene glycol-polypropylene glycol monomethacrylate, poly (ethylene glycol-tetramethylene glycol) monomethacrylate, poly (propylene glycol-tetramethylene glycol) monomethacrylate, various fatty acid-modified glycidyl methacrylates , "Freamer G-FA series" manufactured by NOF Corporation Can be mentioned. 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, α-hydroxymethyl acrylate, methyl α-hydroxymethyl acrylate, ethyl α-hydroxymethyl acrylate, butyl Alkyl α-hydroxymethyl acrylates such as α-hydroxymethyl acrylate and hexyl α-hydroxymethyl acrylate may be mentioned, and derivatives to which sugars such as ethylene oxide and glucose are added may also be used. In addition, 2-acryloyloxyethyl-2-hydroxyethylphthalic acid, polyethylene glycol monoacrylate, polypropylene glycol monoacrylate, polyethylene glycol-polypropylene glycol monoacrylate, poly (ethylene glycol-tetramethylene glycol) monoacrylate, poly (propylene glycol- Tetramethylene glycol) monoacrylate, 2-hydroxy-3-phenoxypropyl acrylate, 1,4-cyclohexanedimethanol monoacrylate and other acrylic acid ester having a hydroxyl group, hydroxyalkylstyrene such as hydroxymethylstyrene, hydroxymethyl α-methyl Hydroxyalkyl α-methylstyrene such as styrene, 2-hydroxyethyl maleate, Monofunctional ethylenically unsaturated compounds having a hydroxyl group such as bis (2-hydroxyethyl) maleate and 2-hydroxyethyl methyl fumarate may also be used. Furthermore, glycerol dimethacrylate, glycerol acrylate methacrylate, 2-hydroxy-3-acryloyloxypropyl methacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexa (penta) acrylate, glycidyl ether compounds having epoxy groups at both ends, acrylic acid or Polyfunctional ethylenic compounds having two or more ethylenically unsaturated bonds in one molecule, such as those having methacrylic acid added, for example, Epolite acrylic acid adduct “epoxyster” series manufactured by Kyoeisha Chemical Co., Ltd. An unsaturated compound etc. can be mentioned. As long as it can be used as an impregnation solution for the above compound, it may be used alone or in combination. The weight ratio between the ethylenically unsaturated compound polymer having a hydroxyl group and the other components is preferably 5/100 to 300/100. When the weight ratio is smaller than 5/100, the ratio of the ethylenically unsaturated compound polymer having a hydroxyl group is too small, and the effect of using the ethylenically unsaturated compound polymer having a hydroxyl group cannot be sufficiently obtained. . On the other hand, when the weight ratio is larger than 300/100, the compatibility between different polymers is lowered, which is not preferable. More preferably, the weight ratio between the ethylenically unsaturated compound polymer having a hydroxyl group and the other components is 50/100 to 200/100. 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 organic solvent of the present invention refers to a compound that does not substantially react during the polymerization of the ethylenically unsaturated compound and is liquid at room temperature. 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. 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 an organic solvent that does not substantially react with the ethylenically unsaturated compound mentioned here.

  The radically polymerizable composition of the present invention refers to a composition comprising the ethylenically unsaturated compound, the radical polymerization initiator, and the chain transfer agent. A radical polymerization inhibitor, an antioxidant, an anti-aging agent, a filler, a colorant, an antifungal agent, an antibacterial agent, a flame retardant, and an ultraviolet absorber may be added to the radical polymerizable composition. The amount of these compounds added is preferably within a range not exceeding 3% by weight based on the ethylenically unsaturated compound.

  The radically polymerizable composition is preferably a composition that does not substantially contain an organic solvent from the viewpoint of economy that an organic solvent removing step is not required.

  Examples of the radical polymerization inhibitor that can be added to the radical polymerizable composition and are solid at room temperature include 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 polymer molded object manufacture. Furthermore, you may make it contain in both a radically polymerizable composition and a polymer molded object. 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.

  As radical polymerization inhibitors that are preferably impregnated and / or polymerized in the presence of oxygen gas or oxygen-containing gas, phenothiazine, hydroquinone, hydroquinone monomethyl ether, t-butylcatechol, phenyl-β-naphthylamine, p-phenylenediamine, and topanol A etc. 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 chain transfer agent that can be added to the radically polymerizable composition refers to a compound that reacts with a growing radical to stop an increase in the polymer chain length and generate a low-molecular radical capable of reinitiating.

  The chain transfer agent is a first alkyl group or substituted alkyl group such as n-butyl mercaptan, isobutyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, sec-butyl mercaptan, sec-dodecyl mercaptan, t-butyl mercaptan. Aromatic mercaptans such as secondary, tertiary or tertiary mercaptan, phenyl mercaptan, thiocresol, 4-t-butyl-o-thiocresol, thioglycolic acid esters such as 2-ethylhexyl thioglycolate and ethyl thioglycolate And C3-C18 mercaptan such as ethylenethioglycol, 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, n-octyl mercaptan, and n-dodecyl mercaptan, and α-methylstyrene dimer are preferably used.

  The amount of chain transfer agent used is preferably 0.01 to 5% by weight, more preferably 0.05 to 3% by weight, based on the ethylenically unsaturated compound. When the amount used is less than 0.01% by weight, the effect of the chain transfer agent is not exhibited. On the other hand, when the content is more than 5% by weight, mechanical properties such as strength and elastic modulus are lowered.

  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.

  The polymer molded body has a high chemical structure that includes a polyethylene glycol chain, a polypropylene glycol chain, a polytetramethylene glycol chain, a poly (oxyethylene / oxypropylene) chain, etc. as a chemical structure that is flexible and can be swollen by a radically polymerizable composition. Molecular shaped bodies are preferred. Specific examples include polyester and polyurethane. Although depending on the density and the amount of impregnation of the radical polymerizable composition, the volume of the polymer molded body after impregnation swells to about 1.03 to 5 times the original volume, and most of the volume is about 1.03 to 3 Swells about twice.

  The polymer molded body is preferably a foam containing closed cells having an average cell diameter of 10 to 200 μm, more preferably a foam containing closed cells of 20 to 150 μm, and 30 to 120 μm. Particularly preferred is a foam containing the closed cells. 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.

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 taken into the polymer molded body does not enter into the bubbles in the polymer molded body, and the polymer is polymerized after the ethylenically unsaturated compound is polymerized under the swelling state of the polymer molded body. It is preferable that the air bubbles in the molded body remain as air bubbles. The density of the obtained polishing pad as a result of which, preferably 0.2~1.4g / cm ^3, more preferably 0.6 to 1.2 g / cm ^3.

  The polymer molded body of the present invention is preferably a polyurethane molded body obtained from a polyol and a polyisocyanate, and particularly preferably a polyurethane molded body 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, one or a mixture of two or more selected from polyether polyol, polyester polyol, polycarbonate polyol, polycaprolactone polyol, ethylene glycol, propylene glycol, glycerol and the like can be mentioned.

  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 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. When the content weight ratio of the polymer polymerized from the polymerized polymer impregnated with the polymer molded product is smaller than 100/5, the characteristics are not so different from those of the polymer molded product alone, and the polymer is impregnated and polymerized. The benefits may be small. On the other hand, when the weight ratio of the polymer polymerized from the polymer molded body and the polymer polymerized from the impregnated ethylenically unsaturated compound is larger than 100/300, it may not be preferable because the time required for impregnation becomes too long. The step of immersing the polymer molded article 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 10 to 200 μm closed cells, more preferably a foam containing 20 to 150 μm closed cells, and a foam containing 30 to 120 μm closed cells. It is 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 density of the polishing pad is preferably 0.2 to 1.4 g / cm ³ . The density can be measured by the method described in Japanese Industrial Standard JIS K7112.

  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.

  [Water Absorption Rate] The sample was vacuum-dried at room temperature for 24 hours, and then the weight was measured to obtain the dry weight. After immersing in ion-exchanged water for 24 hours and wiping off water adhering to the surface, the weight was measured to obtain a wet weight.

Water absorption rate = (Wet weight-dry weight) × 100 / dry weight.

  [Polishing Evaluation] “Suba400” (Rodel Nitta Co., Ltd.) was used as a cushion layer and 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 0.05 MPa, a polishing surface plate rotation speed of 32 rpm, and a conditioner rotation speed of 30 rpm. The polishing pad was conditioned for 5 minutes while supplying purified water onto the polishing pad at a rate of 200 mL / min.

  An 8-inch silicon wafer for evaluation is mounted on a polishing head of a polishing apparatus, rotated at 40 rpm, a laminated polishing pad is fixed to a platen of a polishing machine, and rotated at 40 rpm in the same direction as the rotation direction of the polishing head. While supplying the slurry at 110 mL / min, polishing was performed at a polishing pressure of 0.06 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.

20 evaluation wafers were polished, and the 20th 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 having a thermal oxide film of about 1.2 μm formed on an 8-inch silicon wafer was used.

  [Defect Inspection] Using a wafer surface inspection apparatus SP1 manufactured by KLA-Tencor, the number of particles adhered to the wafer surface of 0.15 μm or more and the number of scratches generated were measured.

(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 650 mm × 650 mm and a thickness of 25 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 90 parts by weight 1,4-butanediol 10 parts 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 was prepared at a weight ratio of the polyurethane molded product to the radical polymerization composition of 100/200, and the polyurethane molded product was immersed at 20 ° C. for 7 days. However, the entire amount of the radical polymerizable composition was impregnated in the polyurethane molded product.
Methyl methacrylate 300 parts by weight Azobisisobutyronitrile 0.8 part by weight 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. Curing was carried out by heating at 0 ° C. 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, the weight was measured. Drying was carried out 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 the weight immediately, there was no weight reduction before and after normal temperature drying.

A central portion in the thickness direction of the impregnated cured product of the polyurethane molded body was sliced and subjected to surface grinding to obtain a sheet having a thickness of 1.5 mm. The apparent density of the radically polymerizable composition-impregnated cured product of the polyurethane molded product was 0.85 g / cm ³ , the average cell diameter of closed cells was 40 μm, and the water absorption was 3.0%.

  Next, after bonding a double-sided adhesive tape, it was punched into a circle having a diameter of 600 mm, and a grid-like groove having a width of 1.0 mm, a depth of 0.6 mm, and a pitch of 15 mm was formed on one side.

  When the polishing evaluation was performed, the polishing rate was 1200 angstroms / minute. The number of adhered particles was 322, and the number of scratches generated was 25.

(Reference Example 1)
The same polishing pad as that of Comparative Example 1 was used, and polishing was performed under the same conditions except that the amount of silica-based slurry supplied during polishing was 200 mL / min, and wafer evaluation was performed. The polishing rate was 1680 Å / min. The number of adhered particles was 15, and the number of scratches was 3.

Example 1
A polishing pad was produced in exactly the same manner as in Comparative Example 1 except that the following composition was used as the radical polymerizable composition.
Hydroxyethyl methacrylate 300 parts by weight Azobisisobutyronitrile 1.0 part by weight The apparent density of the radical-polymerizable composition-impregnated cured product of the polyurethane molded product is 0.79 g / cm ³ , the average cell diameter of closed cells is 41 μm, water absorption The rate was 30%.

  When the polishing evaluation was performed, the polishing rate was 2000 angstrom / min. Further, the number of adhered particles was 2, and the number of scratches generated was 0.

(Example 2)
A polishing pad was produced in exactly the same manner as in Comparative Example 1 except that the following composition was used as the radical polymerizable composition.
Methyl methacrylate 180 parts by weight Hydroxyethyl acrylate 120 parts by weight Azobisisobutyronitrile 0.9 part by weight The apparent density of the radically polymerizable composition-impregnated cured product of the polyurethane molded product is 0.78 g / cm ³ , and the average cell size of closed cells The diameter was 47 μm, and the water absorption was 12.5%.

  When the polishing evaluation was performed, the polishing rate was 1820 angstrom / min. Further, the number of adhered particles was 10, and the number of scratches generated was 0.

(Example 3)
A polishing pad was produced in exactly the same manner as in Comparative Example 1 except that the following composition was used as the radical polymerizable composition.
Methyl methacrylate 240 parts by weight Glycerol dimethacrylate 60 parts by weight Azobisisobutyronitrile 0.7 part by weight The apparent density of the radically polymerizable composition-impregnated cured product of the polyurethane molded product is 0.77 g / cm ³ , and the average cell of closed cells The diameter was 43 μm, and the water absorption was 10.3%.

  When the polishing evaluation was performed, the polishing rate was 1850 angstroms / minute. Further, the number of adhered particles was 12, and the number of scratches generated was 0.

From the above, a polishing pad made from an interpenetrating polymer network obtained by polymerizing an ethylenically unsaturated compound having a hydroxyl group in a polymer molded body such as polyurethane has a high water absorption and is hydrophilic. Since it has a high surface, the number of adhered particles and the number of scratches generated on the wafer surface after polishing were small. Further, even when polishing was performed under a condition where the slurry supply amount was small, the polishing rate was high and the productivity was excellent.
Example 4
About the radically polymerizable composition-impregnated cured product of the polyurethane molded product used in Example 1, relaxation time measurement was performed by a solid-state NMR (nuclear magnetic resonance) method. It had a structure in which polyurethane and polyhydroxyethyl methacrylate were dispersed on the order of several nanometers or less. From this, it was confirmed that two polymer chains of polyurethane and polyhydroxyethyl methacrylate 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 (0 pieces / screen). ).
(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 platelet count on any 5 screens was counted at a magnification of 1000 times (93 × 105 μm), and the platelet count per unit area was calculated.

  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. . In addition, the interpenetrating polymer network structure of the present invention is excellent in blood compatibility and can be used as a medical material.

Claims (2)

A polishing pad comprising an interpenetrating polymer network characterized by comprising an ethylenically unsaturated compound polymer having a hydroxyl group and polyurethane as independent network structures , each having a water absorption at 23 ° C of 10% or more. The polishing pad according to claim 1 , wherein the polishing pad is used for polishing a semiconductor substrate.