JP2010242064A - Method for producing interpenetrating polymer network structure and polishing pad - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an interpenetrating polymer network structure having high thermal resistance, to provide a method of producing the interpenetrating polymer network structure, and to provide a polishing pad made of the interpenetrating polymer network structure. <P>SOLUTION: The method for producing the interpenetrating polymer network structure includes: a process of immersing a polymer molding body into a radically polymerizable composition A consisting of an ethylenic unsaturated compound A, a radical polymerization initiator A and a chain transfer agent A; a process of polymerizing the ethylenic unsaturated compound A while swelling the polymer molding body impregnated with the radically polymerizable composition A; a process of further immersing the polymer molding body in which the ethylenic unsaturated compound A is polymerized into a radically polymerizable composition B consisting of an ethylenic unsaturated compound B, a radical polymerization initiator B and a chain transfer agent B; and a process of polymerizing the ethylenic unsaturated compound B while swelling the polymer molding body which has the polymerized ethylenic unsaturated compound A therein and is impregnated with the radically polymerizable composition B, in this order. The polishing pad including the interpenetrating polymer network structure is also disclosed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing an interpenetrating polymer network structure. The present invention also relates to a polishing pad. In particular, the present invention relates to a polishing pad used for polishing and planarizing an interlayer insulating film and a wiring forming metal film formed on a semiconductor substrate such as silicon and for polishing an optical member.

  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.

  Patent Document 3 discloses a method for producing a graft polymer-containing resin composition in which a propylene-based polymer is impregnated with a vinyl monomer and then impregnated with a different vinyl monomer and an initiator and polymerized.

International Publication No. 00/12262 JP 2000-218551 A JP-A-5-295047

  The objective of this invention is providing the manufacturing method of the interpenetrating network structure excellent in heat resistance. It is another object of the present invention to provide a polishing pad in which a change in physical properties due to temperature hardly occurs, a fluctuation in polishing rate is small, dishing generated in wiring is reduced, and a pad life is extended.

  The present inventors have focused on increasing the intermolecular interaction as a method for improving heat resistance. Therefore, the radically polymerizable composition can be uniformly infiltrated into the polymer molding by impregnating and polymerizing the radically polymerizable composition into the polymer molding in two stages. The region where the polymer polymerized from the composition interacts, that is, the effective surface area increases, and the intermolecular interaction may increase.

  Here, the method for producing a graft polymer-containing resin composition in which the propylene-based polymer described above in Patent Document 3 is impregnated with a vinyl monomer and then impregnated with a different vinyl monomer and an initiator, is polymerized. After the impregnation with the monomer, different monomers and polymerization initiators are impregnated without polymerization, and the idea is different from the present invention.

  Therefore, as a result of intensive studies, the inventors of the present invention have prepared a polishing pad having a high heat resistance in the polishing pad preparation method disclosed in JP-A-2006-233198. The step of immersing the polymer molded body in the radical polymerizable composition A comprising the polymerization initiator A and the chain transfer agent A, and the ethylenically unsaturated compound in the swollen state of the polymer molded body impregnated with the radical polymerizable composition A step of polymerizing A, a step of immersing a polymer molded body obtained by polymerizing ethylenically unsaturated compound A in radical polymerizable composition B comprising ethylenically unsaturated compound B, radical polymerization initiator B, and chain transfer agent B In the swollen state of the polymer molded body obtained by polymerizing the ethylenically unsaturated compound B impregnated with the radical polymerizable composition, Step engaged, it was found that the object of the present invention is achieved by making the polishing pad from the interpenetrating polymer network structure produced by including in this order.

  That is, the present invention has the following configuration.

  (1) A step of immersing a polymer molding in a radical polymerizable composition A comprising an ethylenically unsaturated compound A, a radical polymerization initiator A, and a chain transfer agent A, a polymer impregnated with the radical polymerizable composition A The step of polymerizing the ethylenically unsaturated compound A under the swollen state of the molded body, the polymer molded body obtained by polymerizing the ethylenically unsaturated compound A further comprising the ethylenically unsaturated compound B, the radical polymerization initiator B, and the chain transfer agent B A step of immersing in a radically polymerizable composition B comprising: an ethylenically unsaturated compound B is polymerized in a swollen state of a polymer molded body obtained by polymerizing the ethylenically unsaturated compound A impregnated with the radically polymerizable composition B A method for producing an interpenetrating polymer network structure comprising the steps in this order.

  (2) The weight ratio (a / (a + b)) is 15/100 to 35/100 or 65/100 to 85, where a is the weight of ethylenically unsaturated compound A and b is the weight of ethylenically unsaturated compound B. The method for producing an interpenetrating polymer network structure according to (1), which is / 100.

  (3) The method for producing an interpenetrating polymer network according to (1), wherein the ethylenically unsaturated compound B is a styrene monomer and the ethylenically unsaturated compound A is a monomer other than the styrene monomer.

  (4) A polishing pad comprising an interpenetrating polymer network produced by the method for producing an interpenetrating polymer network described in (1).

  (5) The polishing pad according to (4), wherein the polymer molded body contains polyurethane.

  (6) The weight ratio of the weight of the polymer molded body to the total weight of the polymer polymerized from the impregnated ethylenically unsaturated compound A and ethylenically unsaturated compound B is 100/5 to 100/300 ( The polishing pad according to 4) or (5).

  (7) The polishing pad according to any one of (4) to (6), which is used for polishing a semiconductor substrate and / or polishing an optical member.

  An interpenetrating polymer network having high heat resistance is obtained. In addition, since a change in physical properties due to temperature is unlikely to occur, a polishing pad with a small variation in the polishing rate, a reduced dishing in the wiring, and an extended pad life can be manufactured.

  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, a step of immersing a polymer molding in a radical polymerizable composition A comprising an ethylenically unsaturated compound A, a radical polymerization initiator A, and a chain transfer agent A, a polymer impregnated with the radical polymerizable composition The step of polymerizing the ethylenically unsaturated compound A under the swollen state of the molded body, the polymer molded body obtained by polymerizing the ethylenically unsaturated compound A further comprising the ethylenically unsaturated compound B, the radical polymerization initiator B, and the chain transfer agent B A step of immersing in a radical polymerizable composition B comprising: a step of polymerizing an ethylenically unsaturated compound in a swollen state of a polymer molded body obtained by polymerizing an ethylenically unsaturated compound B impregnated with the radical polymerizable composition; The reason why the interpenetrating polymer network structure produced by containing the components in this order has high heat resistance is not necessarily clear, but is a polymer molded body The radical polymerizable composition can be uniformly infiltrated into the polymer molded body by being impregnated and polymerized in two or more stages, and polymerized from the polymer molded body and the radical polymerizable composition. It is presumed that the heat resistance is improved by increasing the region where the polymer interacts, that is, the effective surface area.

  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 it is difficult for the rigidity to be lowered, it is presumed that the polishing rate is high, the fluctuation of the polishing rate is small, the dishing generated in the wiring is reduced, and the pad life is extended.

  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 ethylenically unsaturated compound A and the ethylenically unsaturated compound B may be the same compound or different compounds. Furthermore, the ethylenically unsaturated compound A and the ethylenically unsaturated compound B may include different ethylenically unsaturated compounds. That is, the ethylenically unsaturated compound B may be contained in the ethylenically unsaturated compound A, or the ethylenically unsaturated compound A may be contained in the ethylenically unsaturated compound B. In addition, the impregnation / polymerization of the radically polymerizable composition into the polymer molded body is not limited to two stages, and may be further multistaged.

  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. Further, the radical polymerization initiator A and the radical polymerization initiator B may be the same compound or different compounds.

  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.

  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.

  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. Further, the chain transfer agent A and the chain transfer agent B may be the same compound or different compounds.

  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 less than 3000, 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 ethylenically unsaturated compound A and the ethylenically unsaturated compound B is the weight ratio (a / (a + b)) where the weight of the ethylenically unsaturated compound A is a and the weight of the ethylenically unsaturated compound B is b. Is preferably 15/100 to 35/100 or 65/100 to 85/100. When the weight ratio between the ethylenically unsaturated compound A and the ethylenically unsaturated compound B is less than 15/100, the characteristics are not so different from those when only the ethylenically unsaturated compound B is impregnated and polymerized. The merit of impregnating and polymerizing the saturated compound A and the ethylenically unsaturated compound B may be small. On the other hand, when the weight ratio of the ethylenically unsaturated compound A and the ethylenically unsaturated compound B is greater than 85/100, the characteristics are not so different from the case where only the ethylenically unsaturated compound A is impregnated and polymerized. The merit of impregnating and polymerizing the ethylenically unsaturated compound A and the ethylenically unsaturated compound B may be small.

  Moreover, when the weight ratio of the ethylenically unsaturated compound A and the ethylenically unsaturated compound B is 35/100 to 65/100, that is, the difference in weight between the ethylenically unsaturated compound A and the ethylenically unsaturated compound B is If it is small, the effect that the radical polymerizable composition uniformly penetrates into the polymer molded body is reduced, and the merit of impregnating and polymerizing the ethylenically unsaturated compound A and the ethylenically unsaturated compound B may be small.

  The ratio of the weight of the polymer molded body to the total weight of the polymer polymerized from the impregnated ethylenically unsaturated compound A and the ethylenically unsaturated compound B is preferably 100/5 to 100/300, and preferably 100/50. ~ 100/200 is more preferred. When the ratio of the weight of the polymer molded body to the total weight of the polymer polymerized from the impregnated ethylenically unsaturated compound A and the ethylenically unsaturated compound B is less than 100/5, only the polymer molded body In some cases, the characteristics do not change so much and the merit of impregnation and polymerization is small. On the other hand, when the ratio of the weight of the polymer molded body to the total weight of the polymer polymerized from the impregnated ethylenically unsaturated compound A and the ethylenically unsaturated compound B is greater than 100/300, the time required for impregnation May become unpreferable because it 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 [Glass transition temperature] The glass transition temperature is tan δ maximum when measured under the following measurement conditions using a dynamic viscoelasticity measuring device “DVE-V4” (manufactured by Rheology Co., Ltd.). Value temperature. When two or more tan δ maximum temperatures exist, the lower one was set as the glass transition point.
Jig: Distance between tension chucks: 20 mm
Waveform: Sine wave Distortion frequency: 10Hz
Displacement amplitude: 3.0 μm
Measurement temperature: 0 to 150 ° C
Temperature increase rate: 2 ° C / 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 (registered trademark) 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 slurry for copper (iCue (registered trademark) 5003 manufactured by Cabot Corporation) was fed at 220 mL / min for 1 minute at a polishing pressure of 4 psi, 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. The smaller the difference between the polishing rates of the 50th and 400th sheets, the smaller the fluctuation of the polishing rate, which is desirable.

  [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. The smaller the number of particles, the better.

  [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). The smaller the dishing amount, the better.

(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 0.84 g / cm ³ , and closed cells having an average cell diameter of 31 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. (Impregnation process)
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 and then in an oven at 100 ° C. for 3 hours to obtain an interpenetrating polymer network. (Polymerization process)
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 interpenetrating polymer network thus obtained was sliced and ground to a thickness of 2 mm. The apparent density was 0.80 g / cm ³ , and the average cell diameter of closed cells was 43 μm. Openings derived from 213 bubbles / mm ² bubbles were observed on the surface. The tensile elongation at break was 124%.

  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 460 nm / min and 320 nm / min, respectively. The dishing amount was 63 nm. The number of particles was 65.

Example 1
Using the polyurethane molded product obtained in the same manner as in Comparative Example 1, the following radical polymerizable composition was prepared at a weight ratio of 100/110 between the polyurethane molded product and the radical polymerizable composition. When the body was immersed at 20 ° C. for 7 days, the entire amount of the radical polymerizable composition was impregnated in the polyurethane molded body. (Impregnation step A)
Methyl methacrylate 300 parts by weight Azobisisobutyronitrile 0.8 part by weight Polymerized and cured in the same manner as in Comparative Example 1. (Polymerization step A)
Further, the following radical polymerizable composition was prepared in this polymerized cured product at a ratio of the weight of the polyurethane molded product to the weight of the radical polymerizable composition of 100/30, and immersed at 20 ° C. for 7 days. The entire composition was impregnated in the polymerized cured product. (Impregnation step B) a / (a + b) was 110 / (110 + 30) or 79/100.
Methyl methacrylate 300 parts by weight Azobisisobutyronitrile 0.8 part by weight Polymerization and curing was carried out in the same manner as in Comparative Example 1 to obtain an interpenetrating polymer network. (Polymerization process B)
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 interpenetrating polymer network thus obtained was sliced and ground to a thickness of 2 mm. The apparent density was 0.78 g / cm ³ and the average cell diameter of closed cells was 44 μm. On the surface, openings derived from bubbles of 219 / mm ² were observed. The tensile elongation at break was 123%.

  Next, when polishing evaluation was performed in the same manner as in Comparative Example 1, the polishing rates were 560 nm / min and 510 nm / min, respectively. The dishing amount was 38 nm. The number of particles was 52.

(Example 2)
In the impregnation step A, the weight ratio of the polyurethane molded product to the radical polymerizable composition is adjusted to a ratio of 100/35, and in the impregnation step B, the weight ratio of the polyurethane molded product to the radical polymerizable composition is 100/105. An interpenetrating polymer network structure was obtained in the same manner as in Example 1 except that the ratio was adjusted. a / (a + b) was 35 / (35 + 105) or 25/100.

  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 interpenetrating polymer network thus obtained was sliced and ground to a thickness of 2 mm. The apparent density was 0.79 g / cm ³ , and the average cell diameter of closed cells was 45 μm. On the surface, openings derived from 210 bubbles / mm ² were observed. The tensile elongation at break was 106%.

  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 540 nm / min and 500 nm / min, respectively. The dishing amount was 39 nm. The number of particles was 63.

(Comparative Example 2)
Using the polyurethane molded product obtained in the same manner as in Comparative Example 1, the following radical polymerizable composition was prepared at a weight ratio of 100/140 between the polyurethane molded product and the radical polymerizable composition. When the body was immersed at 20 ° C. for 7 days, the entire amount of the radical polymerizable composition was impregnated in the polyurethane molded body. (Impregnation process)
Methyl methacrylate 150 parts by weight Styrene 150 parts by weight Azobisisobutyronitrile 0.8 part by weight Polymerization and curing was carried out in the same manner as in Comparative Example 1 to obtain an interpenetrating polymer network structure. (Polymerization process)
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 interpenetrating polymer network thus obtained was sliced and ground to a thickness of 2 mm. The apparent density was 0.89 g / cm ³ , and the average cell diameter of closed cells was 41 μm. Moreover, the opening part derived from the bubble of 185 piece / mm < ² > was observed on the surface. In addition, from the scanning electron microscope image, it was observed that the radical polymerizable composition had entered into the bubbles in the polymer molded body. Therefore, the apparent density of the radical polymerizable composition-impregnated cured product of the polyurethane molded body was It is thought that became higher. The tensile elongation at break was 116%.

  Next, when polishing evaluation was performed in the same manner as in Comparative Example 1, the polishing rates were 460 nm / min and 260 nm / min, respectively. The dishing amount was 103 nm. The number of particles was 72.

Example 3
Using the polyurethane molded product obtained in the same manner as in Comparative Example 1, the following radical polymerizable composition was prepared at a weight ratio of 100/70 between the polyurethane molded product and the radical polymerizable composition. When the body was immersed at 20 ° C. for 7 days, the entire amount of the radical polymerizable composition was impregnated in the polyurethane molded body. (Impregnation step A)
Methyl methacrylate 300 parts by weight Azobisisobutyronitrile 0.8 part by weight Polymerized and cured in the same manner as in Comparative Example 1. (Polymerization step A)
Further, the following radical polymerizable composition was prepared in this polymerized cured product at a ratio of 100/70 by weight ratio of the weight of the polyurethane molded product to the radical polymerizable composition, and immersed at 20 ° C. for 7 days. The entire composition was impregnated in the polymerized cured product. (Impregnation step B) a / (a + b) was 70 / (70 + 70) or 50/100.
Styrene 300 parts by weight Azobisisobutyronitrile 0.8 parts by weight Polymerized and cured in the same manner as in Comparative Example 1 to obtain an interpenetrating polymer network. (Polymerization process B)
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 interpenetrating polymer network thus obtained was sliced and ground to a thickness of 2 mm. The apparent density was 0.78 g / cm ³ , and the average cell diameter of closed cells was 41 μm. Further, openings derived from 205 / mm ² bubbles were observed on the surface. In addition, penetration by the radically polymerizable composition into the bubbles in the polymer molded body was not observed. The tensile elongation at break was 124%.

  Next, when the polishing evaluation was performed in the same manner as in Comparative Example 1, the polishing rates were 470 nm / min and 320 nm / min, respectively. The dishing amount was 79 nm. The number of particles was 52.

(Comparative Example 3)
Using the polyurethane molded product obtained in the same manner as in Comparative Example 1, the following radical polymerizable composition was prepared at a weight ratio of 100/140 between the polyurethane molded product and the radical polymerizable composition. When the body was immersed at 20 ° C. for 7 days, the entire amount of the radical polymerizable composition was impregnated in the polyurethane molded body. (Impregnation process)
Methyl methacrylate 150 parts by weight Acrylonitrile 150 parts by weight Azobisisobutyronitrile 0.8 part by weight Polymerized and cured in the same manner as in Comparative Example 1 to obtain an interpenetrating polymer network structure. (Polymerization process)
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 interpenetrating polymer network thus obtained was sliced and ground to a thickness of 2 mm. The apparent density was 0.83 g / cm ³ , and the average cell diameter of closed cells was 41 μm. On the surface, the opening was observed from bubbles 192 / mm ^2. The tensile elongation at break was 122%.

  Next, when the polishing evaluation was performed in the same manner as in Comparative Example 1, the polishing rates were 510 nm / min and 390 nm / min, respectively. The dishing amount was 57 nm. The number of particles was 66.

Example 4
Using the polyurethane molded product obtained in the same manner as in Comparative Example 1, the following radical polymerizable composition was prepared at a weight ratio of 100/70 between the polyurethane molded product and the radical polymerizable composition. When the body was immersed at 20 ° C. for 7 days, the entire amount of the radical polymerizable composition was impregnated in the polyurethane molded body. (Impregnation step A)
Methyl methacrylate 300 parts by weight Azobisisobutyronitrile 0.8 part by weight Polymerized and cured in the same manner as in Comparative Example 1. (Polymerization step A)
Further, the following radical polymerizable composition was prepared in this polymerized cured product at a ratio of 100/70 by weight ratio of the weight of the polyurethane molded product to the radical polymerizable composition, and immersed at 20 ° C. for 7 days. The entire composition was impregnated in the polymerized cured product. (Impregnation step B) a / (a + b) was 70 / (70 + 70) or 50/100.
Acrylonitrile 300 parts by weight Azobisisobutyronitrile 0.8 part by weight Polymerized and cured in the same manner as in Comparative Example 1 to obtain an interpenetrating polymer network. (Polymerization process B)
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 interpenetrating polymer network thus obtained was sliced and ground to a thickness of 2 mm. The apparent density was 0.80 g / cm ³ , and the average cell diameter of closed cells was 43 μm. On the surface, openings derived from 207 bubbles / mm ² bubbles were observed. The tensile elongation at break was 140%.

  Next, when polishing evaluation was performed in the same manner as in Comparative Example 1, the polishing rates were 580 nm / min and 550 nm / min, respectively. The dishing amount was 41 nm. The number of particles was 52.

(Examples 5 to 8)
The weight ratio of the polyurethane molded article and the radical polymerizable composition in the impregnation step A and the weight ratio of the polyurethane molded article and the radical polymerizable composition in the impregnation step B were adjusted as shown in Table 1, respectively. Except for the above, an interpenetrating polymer network structure was obtained in the same manner as in Example 1.

  These results are summarized in Table 1, including the glass transition temperature of each interpenetrating polymer network.

  From the above, the step of immersing the polymer molding in the radical polymerizable composition A comprising the ethylenically unsaturated compound A, the radical polymerization initiator A, and the chain transfer agent A, the polymer impregnated with the radical polymerizable composition A The step of polymerizing the ethylenically unsaturated compound A under the swollen state of the molded body, the polymer molded body obtained by polymerizing the ethylenically unsaturated compound A further comprising the ethylenically unsaturated compound B, the radical polymerization initiator B, and the chain transfer agent B A step of immersing in a radically polymerizable composition B comprising: an ethylenically unsaturated compound B is polymerized in a swollen state of a polymer molded body obtained by polymerizing the ethylenically unsaturated compound A impregnated with the radically polymerizable composition B The polishing pad made from the interpenetrating polymer network produced by including the steps in this order is less susceptible to changes in physical properties due to temperature. Variations in the polishing rate is small, a long lifetime. 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 (7)

  A step of immersing the polymer molded article in a radical polymerizable composition A comprising an ethylenically unsaturated compound A, a radical polymerization initiator A, and a chain transfer agent A, and a polymer molded article impregnated with the radical polymerizable composition A. A step of polymerizing the ethylenically unsaturated compound A in a swollen state, a polymer molded body obtained by polymerizing the ethylenically unsaturated compound A, and a radical comprising an ethylenically unsaturated compound B, a radical polymerization initiator B, and a chain transfer agent B A step of immersing in the polymerizable composition B, a step of polymerizing the ethylenically unsaturated compound B in a swollen state of the polymer molded body obtained by polymerizing the ethylenically unsaturated compound A impregnated with the radical polymerizable composition B, The manufacturing method of the interpenetrating polymer network structure characterized by including in this order.   The weight ratio (a / (a + b)) is 15/100 to 35/100 or 65/100 to 85/100, where a is the weight of ethylenically unsaturated compound A and b is the weight of ethylenically unsaturated compound B. The method for producing an interpenetrating polymer network structure according to claim 1.   The method for producing an interpenetrating polymer network according to claim 1, wherein the ethylenically unsaturated compound B is a styrene monomer, and the ethylenically unsaturated compound A is a monomer other than the styrene monomer.   A polishing pad comprising an interpenetrating polymer network structure produced by the method for producing an interpenetrating polymer network structure according to claim 1.   The polishing pad according to claim 4, wherein the polymer molded body contains polyurethane.   The weight ratio of the weight of the polymer molding to the total weight of the polymer polymerized from the impregnated ethylenically unsaturated compound A and ethylenically unsaturated compound B is 100/5 to 100/300. 5. The polishing pad according to 5.   The polishing pad according to claim 4, which is used for polishing a semiconductor substrate and / or polishing an optical member.