JP2010077288A - Interpenetrating polymer network structure, polishing pad, and method for producing interpenetrating polymer network structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an interpenetrating polymer network structure having high heat resistance and high elongation, and a method for producing the same; and also to provide a polishing pad with a high polishing rate, small variation of the polishing rate, and reduced dishing occurring in wiring so that service life of the pad is extended. <P>SOLUTION: There are provided (1) an interpenetrating polymer network structure with added cross-linking agent containing an epoxy group and (2) a polishing pad comprising the interpenetrating polymer network structure described in (1). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an interpenetrating polymer network structure, a polishing pad, and a method for producing an interpenetrating polymer network structure. 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.

  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, the metal wiring is made thinner by polishing the metal thin film such as copper to form fine wiring, and the central portion of the metal wiring is thinner than the edge in the wiring-insulator planarization step. 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. This dishing is thought to be caused by the deflection of the polishing pad. However, when polishing a metal such as copper, the surface temperature of the polishing pad reaches about 70 ° C, so the rigidity must not change even at high temperatures. It is.

Moreover, although the polishing pad which consists of a substance which has functional groups, such as a crosslinked elastomer and an epoxy group, is indicated by patent document 3, this is increasing the retention amount of a slurry by functional groups, such as an epoxy group, The polishing rate is improved, and functional groups such as epoxy groups are used as they are.
International Publication No. 00/12262 JP 2000-218551 A JP 2002-134445 A

  An object of the present invention is to provide an interpenetrating network structure having high heat resistance and high elongation and a method for producing the same. In addition, since the change in physical properties due to temperature is difficult to occur, the polishing rate is high, the fluctuation of the polishing rate is small, the dishing generated in the wiring is reduced, the pad life is extended, and the elongation is high, so the polishing rate is higher. It is an object of the present invention to provide a polishing pad having a high level and a longer pad life.

  The present inventors have focused on increasing the cross-linking distance in a cross-linked structure as a method for improving heat resistance and elongation. However, it may be difficult to impregnate the interpenetrating polymer network structure by adding a crosslinking agent having a long crosslinking distance from the beginning, that is, having a long molecular chain. Therefore, the idea was to add a cross-linking agent containing an epoxy group. Even when the crosslinking distance is not long at the time of addition, that is, a crosslinking agent having a short molecule, by having an epoxy group, the chemical reaction between the epoxy groups by heat proceeds and the crosslinking distance is doubled. The structure was formed and the elongation was considered to improve.

  Here, as described above, the polishing pad made of a substance having a functional group such as a crosslinked elastomer and an epoxy group described in Patent Document 3 described above increases the amount of slurry retained by the functional group such as an epoxy group. Thus, the polishing rate is improved, which is different in concept from the present invention, and the functional group such as an epoxy group is used as it is. The structure is different.

  Therefore, as a result of intensive studies, the present inventors have included an epoxy group in order to produce a polishing pad having high heat resistance and high elongation in the polishing pad preparation method disclosed in JP-A-2006-233198. It has been found that the object of the present invention can be achieved by adding a crosslinking agent.

  That is, the present invention has the following configuration.

  (1) An interpenetrating polymer network structure to which a crosslinking agent containing an epoxy group is added.

  (2) A polishing pad comprising the interpenetrating polymer network structure according to claim 1.

  (3) The polishing pad according to claim 2, comprising polyurethane.

  (4) The polishing pad according to claim 3, wherein the polishing pad is used for polishing a semiconductor substrate.

  (5) A step of immersing a polymer molded article in a radical polymerizable composition containing a crosslinking agent containing an epoxy group and a compound having a radical reactive group and a radical polymerization initiator, and a high impregnation with the radical polymerizable composition A method for producing an interpenetrating polymer network, comprising a step of copolymerizing a radically polymerizable compound under a swollen state of a molecular molded body.

  (6) The method for producing an interpenetrating polymer network according to claim 5, wherein a weight ratio of the crosslinking agent containing the epoxy group and the radical polymerizable composition is 5/100 to 300/100.

  An interpenetrating polymer network structure having high heat resistance and high elongation can be obtained. In addition, since the change in physical properties due to temperature is difficult to occur, the polishing rate is high, the fluctuation of the polishing rate is small, the dishing generated in the wiring is reduced, the pad life is extended, and the elongation is high, so the polishing rate is higher. A polishing pad having a high length and a longer pad life can be produced.

  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 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.

  In the present invention, the interpenetrating polymer network structure to which a crosslinking agent containing an epoxy group is added has high heat resistance and high elongation because the microbrown motion of the polymer main chain is suppressed by the crosslinked structure, and the glass transition As the point rises, unlike ordinary crosslinking agents, it is assumed that by having an epoxy group, the chemical reaction between the epoxy groups by heat proceeds and a flexible crosslinking structure in which the crosslinking distance is doubled is formed. The

  As a result, a polishing pad using this interpenetrating network polymer structure has little change in physical properties even when the temperature of the pad rises during polishing. In particular, since the decrease in rigidity is difficult to occur, the polishing rate is high, the fluctuation of the polishing rate is small, and dishing that occurs in a defeat is reduced, the pad life is extended, and the elongation is high, so the polishing rate is high, It is assumed that the pad life will be longer.

  The crosslinking agent containing an epoxy group of the present invention preferably contains a vinyl group. More preferably, it contains acrylate or methacrylate. Moreover, it is preferable that molecular weight is about 100-300. Specific examples include glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, methyl glycidyl acrylate, methyl glycidyl methacrylate, glycidyloxyethyl acrylate, glycidyloxyethyl methacrylate, 3,4-epoxycyclohexylmethyl acrylate, 3,4-epoxycyclohexyl methacrylate, 4 Examples thereof include -hydroxybutyl acrylate glycidyl ether and 4-hydroxybutyl methacrylate glycidyl ether, but are not limited thereto.

  The ethylenically unsaturated compound in the present invention refers to a compound having a radical polymerizable carbon-carbon double bond. Specifically, 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-ethylhexyl methacrylate, isodecyl methacrylate, n-lauryl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl Methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, glycidyl methacrylate , 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, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 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 the polymer molded body.

  The weight ratio of the crosslinking agent containing an epoxy group of the present invention and the radical polymerizable composition is desirably 5/100 to 300/100. When the weight ratio is smaller than 5/100, the proportion of the crosslinking agent containing an epoxy group is too small, and the crosslinking effect may not be sufficiently obtained. On the other hand, when the weight ratio is larger than 300/100, the compatibility between different polymers may be lowered, which may not be preferable. More preferably, the weight ratio of the crosslinking agent containing an epoxy group and the radical polymerizable composition is 5/100 to 100/100, more preferably 5/100 to 30/100.

  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-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 amount of radical polymerization initiator added is preferably 0.01 to 5% by weight, more preferably 0.05 to 5% by weight, based on the ethylenically unsaturated compound including the hydrogen bonding compound.

  The organic solvent of 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. “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 the 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.

  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, p-phenylenediamine, and the like. 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 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.

  As the chain transfer agent, n-butyl mercaptan, isobutyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, sec-butyl mercaptan, sec-dodecyl mercaptan, t-butyl mercaptan and the like are those having an alkyl group or a substituent alkyl group. 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 5% by weight, more preferably 0.05 to 3% by weight, based on the ethylenically unsaturated compound. When the amount used is 0.01% by weight or less, the effect as a chain transfer agent is not sufficient. On the other hand, if it is 5% by weight or more, the molecular weight of the polymer chain becomes too short, resulting in poor mechanical properties.

  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 is a polymer containing 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. A molded body is 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 1.03 to 3 times. Swells to a degree.

  The form of the polymer molded body 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 independent of 30 to 120 μm. A foam having bubbles is particularly preferable. 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 polymer-extruded article 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) K7112. 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 0.2~1.1g / cm ^3, more preferably 0.6~1.1g / 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, 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.

  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 impregnating the polymer molding with the radically 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 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 density of the polishing pad is preferably 0.2 to 1.1 g / cm ² . The density can be measured by the method described in Japanese Industrial Standard (JIS) K7112.

  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.

  [Density] The density was measured using a pycnometer (Harvard type) according to the method described in JIS K7112.

  [Average bubble diameter] The average bubble diameter was obtained by analyzing a photograph of a cross section of the pad observed at 200 times magnification with an image processing apparatus using a scanning electron microscope “SEM2400” (manufactured by Hitachi, Ltd.). All the bubble diameters present therein were measured, and the average value was taken as the average bubble diameter.

[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. Five test pieces were used as measured values.
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] Polishing evaluation was performed as follows.

  A slurry was prepared by adding and mixing 5 mL of 30 wt% hydrogen peroxide water immediately before use with respect to 1000 mL of a polishing slurry for copper (iCue 5003 manufactured by Cabot Corporation).

  A double-sided adhesive tape was bonded to the polishing layer sheet to produce a single-layer polishing pad. A single-layer polishing pad was affixed on the surface plate of the polishing machine, and the diamond conditioner was pressed in the same direction as the polishing surface plate at a pressure of 0.8 psi, a polishing surface plate rotation speed of 30 rpm, and a conditioner rotation speed of 28 rpm. The polishing pad was conditioned for 30 minutes while supplying purified water onto the polishing pad at a rate of 100 mL / min.

  An 8-inch wafer for evaluation is mounted on a polishing head of a polishing apparatus, rotated at 33 rpm, a single-layer polishing pad is fixed to a platen of a polishing machine, and rotated at 30 rpm in the same direction as the rotation direction of the polishing head. Polishing was performed for 1 minute at a polishing pressure of 4 psi while supplying a copper polishing slurry (iCue5003 manufactured by Cabot Corporation) at 220 mL / min, and the polishing rate of the copper film was measured. The polishing rates of the 50th and 400th copper films were measured. After measuring the polishing rate of the 50th wafer, the wafer with a pattern for dishing evaluation was polished, and the dishing amount was measured. The polishing was completed by detecting an optical end point signal. Subsequently, the copper solid film was polished, and the number of particles was measured.

  [Polishing Rate] The amount of polishing (polishing rate) per unit time was calculated by measuring the wafers before and after polishing with a resistivity meter VR-120S (made by Kokusai Denki Alpha Co., Ltd.). A copper film having a thickness of 10,000 angstroms formed on an 8-inch silicon wafer was used.

  [Number of Particles] The number of particles on the wafer without pattern was evaluated using a defect / foreign particle inspection apparatus (SP-1 manufactured by KLA Tencor). The total number of particles of 0.2 μm or more was measured.

  [Dishing Amount] Polishing was performed using a patterned wafer having copper wiring (wiring width 10 μm) isolated in the oxide film, and evaluation was performed using a surface measurement profiler (P-15 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 100/140 of the polyurethane molded product and the radical polymerizable composition, and the polyurethane molded product was immersed at 20 ° C. for 7 days. 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 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. The polymer was cured by heating at 70 ° C. for 5 hours followed by heating in a 100 ° C. oven for 3 hours. 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 cured product impregnated with the radical polymerizable composition of the obtained polyurethane molded product was 0.81 g / cm ³ , and the average cell diameter of closed cells was 42 μm. On the surface, openings derived from 247 bubbles / mm ² bubbles were observed. The tensile elongation at break was 116%.

  Next, after bonding the double-sided tape, it was punched out into a circle with a diameter of 600 nm, 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 side.

  When the polishing evaluation was performed, the polishing rates were 470 nm / min and 340 nm / min, respectively. The dishing amount was 50 nm. The number of particles was 63.

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.
Methyl methacrylate 300 parts by weight 4-hydroxybutyl acrylate glycidyl ether (4-HBAGE, Nippon Kasei Co., Ltd.) 75 parts by weight Triethylamine 7.5 parts by weight Azobisisobutyronitrile 1.0 part by weight Radially polymerizable composition of polyurethane molded product The apparent density of the product-impregnated cured product was 0.79 g / cm ³ , and the average cell diameter of closed cells was 43 μm. On the surface, openings derived from 214 bubbles / mm ² bubbles were observed. The tensile elongation at break was 141%.

  When the polishing evaluation was performed, the polishing rates were 680 nm / min and 630 nm / min, respectively. The dishing amount was 22 nm. The number of particles was 38.

(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 300 parts by weight 4-hydroxybutyl acrylate glycidyl ether (4-HBAGE, manufactured by Nippon Kasei Co., Ltd.) 30 parts by weight Triethylamine 3.0 parts by weight Azobisisobutyronitrile 0.9 part by weight Radially polymerizable composition of polyurethane molded product The apparent density of the product-impregnated cured product was 0.80 g / cm ³ , and the average cell diameter of closed cells was 41 μm. Openings derived from 232 bubbles / mm ² bubbles were observed on the surface. The tensile elongation at break was 133%.

  When the polishing evaluation was performed, the polishing rates were 650 nm / min and 580 nm / min, respectively. The dishing amount was 26 nm. The number of particles was 38.

  From the above, a polishing pad made from an interpenetrating polymer network structure obtained by radical copolymerization of a crosslinking agent containing an epoxy group and a compound having a radical reactive group is unlikely to change in physical properties due to temperature and has high elongation. Therefore, the polishing rate is high, the fluctuation of the polishing rate is small, and the life is long. It can also be seen that dishing that occurs in the wiring is reduced.

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 (6)

  An interpenetrating polymer network structure to which a crosslinking agent containing an epoxy group is added.   A polishing pad comprising the interpenetrating polymer network structure according to claim 1.   The polishing pad according to claim 2, comprising polyurethane.   The polishing pad according to claim 3, wherein the polishing pad is used for polishing a semiconductor substrate.   A step of immersing a polymer molded body in a radical polymerizable composition containing a crosslinking agent containing an epoxy group, a compound having a radical reactive group and a radical polymerization initiator, and a polymer molded article impregnated with the radical polymerizable composition A process for producing an interpenetrating polymer network, comprising a step of copolymerizing a radically polymerizable compound under a swollen state.   The method for producing an interpenetrating polymer network structure according to claim 5, wherein a weight ratio of the crosslinking agent containing the epoxy group and the radical polymerizable composition is 5/100 to 300/100.