JP2009214275A - Polishing pad - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing pad which has superior durability and can be used in both polishing of rough polishing and finish polishing. <P>SOLUTION: In a polishing pad provided with a polishing layer on a base material layer, the polishing layer is composed of a thermosetting polyurethane foaming body containing substantially spherical continuous bubbles. In the polishing layer, a glass transition temperature (Tg) is set in a range of 20°C to 90°C, and a ratio of a storage elastic modulus E'(Tg) in the glass transition temperature (Tg) to a storage elastic modulus E'(Tg-20°C) at a temperature 20°C lower than the glass transition temperature (Tg), i.e. E'(Tg-20°C)/E'(Tg) is 10 or more. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polishing pad (for rough polishing and finish polishing) used for polishing surfaces of optical materials such as lenses and reflection mirrors, semiconductor wafers, glass substrates for hard disks, and aluminum substrates.

  In general, mirror polishing of semiconductor wafers such as silicon wafers, lenses, and glass substrates mainly involves rough polishing for the purpose of adjusting flatness and in-plane uniformity, improvement of surface roughness, and removal of scratches. There is intended finish polishing.

  The finish polishing is usually performed by attaching a suede-like artificial leather made of soft urethane foam on a rotatable surface plate and supplying an abrasive containing colloidal silica to an alkali-based aqueous solution. (Patent Document 1).

  In addition to the above, the following have been proposed as polishing pads used for finish polishing.

  A suede-like finish polishing pad consisting of a nap layer in which polyurethane foam is formed with a number of elongated fine holes (nap) formed in the thickness direction using a foaming agent and a base fabric that reinforces the nap layer has been proposed. (Patent Document 2).

  In addition, a polishing cloth for finish polishing that is suede-like and has a surface roughness of 5 μm or less in arithmetic mean roughness (Ra) has been proposed (Patent Document 3).

  Also, a polishing cloth for finishing polishing comprising a base material part and a surface layer (nap layer) formed on the base material part, wherein the surface layer contains a polyvinyl halide or a vinyl halide copolymer. Has been proposed (Patent Document 4).

  Conventional polishing pads for finishing have been manufactured by a so-called wet curing method. The wet curing method is a method in which a urethane resin solution in which a urethane resin is dissolved in a water-soluble organic solvent such as dimethylformamide is applied onto a substrate, which is treated in water and wet solidified to form a porous silver surface layer. The surface layer (nap layer) is formed by grinding the surface of the silver surface layer after washing and drying. For example, in Patent Document 5, a polishing pad for finishing having a substantially spherical hole with an average diameter of 1 to 30 μm is manufactured by a wet curing method.

  However, the conventional polishing pad for finishing has a long and slender structure or the mechanical strength of the material of the surface layer itself is low. Therefore, the durability is poor, the flattening characteristics are gradually deteriorated, and the polishing rate is stable. There was a problem of being inferior.

  On the other hand, the following has been proposed as a polishing pad used for rough polishing.

  A polishing pad has been proposed in which the polishing layer has a ratio of E ′ at 30 ° C. to 90 ° C. of about 1 to 3.6 (Patent Document 6).

  The storage elastic modulus E ′ (30 ° C.) at 30 ° C. of the polishing substrate is 120 MPa or less, and the ratio of the storage elastic modulus E ′ (30 ° C.) at 30 ° C. to the storage elastic modulus E ′ (60 ° C.) at 60 ° C. ( A chemical mechanical polishing pad in which E ′ (30 ° C.) / E ′ (60 ° C.) is 2.5 or more has been proposed (Patent Document 7).

  Since the polishing characteristics required for rough polishing and the polishing characteristics required for final polishing differ greatly, conventionally, a polishing pad for rough polishing and a polishing pad for final polishing have been selectively used. For this reason, it is necessary to replace two types of polishing pads with a polishing surface plate in accordance with the purpose of use during the polishing process, and there is a problem that the polishing process becomes complicated.

JP 2003-37089 A JP 2003-1000068 A1 JP 2004-291155 A JP 2004-335713 A JP 2006-75914 A Japanese translation of PCT publication No. 2004-507076 JP 2006-114485 A

  An object of this invention is to provide the polishing pad which is excellent in durability and can be used for both rough polishing and finish polishing.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above object can be achieved by the polishing pad described below, and have completed the present invention.

That is, the present invention is a polishing pad provided with a polishing layer on a base material layer, the polishing layer comprises a thermosetting polyurethane foam containing substantially spherical open cells,
The polishing layer has a glass transition temperature (Tg) in the range of 20 ° C. to 90 ° C., and 20 ° C. from the storage elastic modulus E ′ (Tg) at the glass transition temperature (Tg) and the glass transition temperature (Tg). The present invention relates to a polishing pad having a ratio [E ′ (Tg−20 ° C.) / E ′ (Tg)] to a storage elastic modulus E ′ (Tg−20 ° C.) at a low temperature of 10 or more.

  The conventional polishing pad for finishing has a long and slender structure or the mechanical strength of the material of the polishing layer itself is low. Therefore, when pressure is repeatedly applied to the polishing layer, “sagging” occurs, resulting in poor durability. It is considered to be. On the other hand, as described above, the durability of the polishing layer can be improved by forming the polishing layer with a thermosetting polyurethane foam having substantially spherical open cells. Therefore, when the polishing pad of the present invention is used, the planarization characteristic can be kept high for a long time, and the stability of the polishing rate is also improved. Here, the substantially spherical shape means a spherical shape and an elliptical shape. Oval and spherical bubbles are those having a major axis L to minor axis S ratio (L / S) of 5 or less, preferably 3 or less, more preferably 1.5 or less.

  Further, the present inventors have found that a polishing pad that can be used for both rough polishing and final polishing can be obtained by using a polishing layer whose storage elastic modulus E ′ varies greatly depending on temperature. In the case of the polishing pad for rough polishing, the storage elastic modulus E ′ of the polishing layer is usually preferably 70 MPa or more. In the case of the polishing pad for finish polishing, the storage elastic modulus E ′ of the polishing layer is usually 10 MPa or less. It is preferable. When the polishing pad of the present invention is used, the storage elastic modulus E ′ of the polishing layer can be easily changed so as to be suitable for rough polishing or finish polishing. Accordingly, it is not necessary to replace the two types of polishing pads with the polishing surface plate, and the efficiency of the polishing process is improved.

  The polishing layer needs to have a glass transition temperature (Tg) in the range of 20 ° C to 90 ° C. This is because if the Tg is outside the range of 20 ° C. to 90 ° C., the slurry may solidify or boil when cooled or heated to such a temperature, and a large amount of energy may be generated when the polishing layer is cooled or heated. This is because the thermal efficiency deteriorates because it is necessary.

  Ratio of storage elastic modulus E ′ (Tg) and storage elastic modulus E ′ (Tg−20 ° C.) [E ′ (Tg−20 ° C.) / E ′ (Tg)] (hereinafter referred to as storage elastic modulus ratio A) Is less than 10, since the storage elastic modulus E ′ does not change significantly before and after the glass transition temperature of the polishing layer, it is not possible to develop polishing characteristics suitable for rough polishing or finish polishing.

  The polishing layer preferably has a storage elastic modulus E ′ (Tg−20 ° C.) of 70 MPa or more. When the storage elastic modulus E ′ (Tg−20 ° C.) is less than 70 MPa, it is difficult to exhibit polishing characteristics suitable for rough polishing.

  The polishing layer has a storage elastic modulus E ′ (Tg−20 ° C.) at a temperature 20 ° C. lower than the glass transition temperature (Tg) and a storage elastic modulus E ′ (Tg) at a temperature 40 ° C. lower than the glass transition temperature (Tg). The ratio [E ′ (Tg−40 ° C.) / E ′ (Tg−20 ° C.)] (hereinafter referred to as storage elastic modulus ratio B) is preferably 2 or less. When the storage elastic modulus ratio B exceeds 2, the storage elastic modulus of the polishing layer tends to change due to temperature change during rough polishing, and the polishing characteristics tend to become unstable.

  Furthermore, the present invention uses the polishing pad, performs rough polishing in a temperature environment where the storage elastic modulus E ′ of the polishing layer is 70 MPa or more, and the storage elastic modulus E ′ of the polishing layer is 10 MPa or less. The present invention relates to a polishing method for an object to be polished, characterized by performing finish polishing in an environment.

  The polishing pad of the present invention includes a polishing layer made of a thermosetting polyurethane foam (hereinafter referred to as polyurethane foam) having substantially spherical open cells, and a base material layer. The polishing layer has a glass transition temperature (Tg) in the range of 20 ° C. to 90 ° C., and 20 from the storage elastic modulus E ′ (Tg) at the glass transition temperature (Tg) and the glass transition temperature (Tg). The ratio [E ′ (Tg−20 ° C.) / E ′ (Tg)] with the storage elastic modulus E ′ (Tg−20 ° C.) at a low temperature is 10 or more.

  Polyurethane resin is excellent in abrasion resistance, and it is possible to easily obtain polymers having desired physical properties by changing the raw material composition. Also, it is easy to form almost spherical fine bubbles by mechanical foaming (including mechanical flossing). Since it can be formed, it is a preferable material for forming the polishing layer.

  The polyurethane resin is composed of an isocyanate component, a polyol component (high molecular weight polyol, low molecular weight polyol, etc.), and a chain extender.

  As the isocyanate component, a known compound in the field of polyurethane can be used without particular limitation. For example, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate, polymeric MDI, carbodiimide-modified MDI (for example, commercial products) Name Millionate MTL, manufactured by Nippon Polyurethane Industry), 1,5-naphthalene diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate, and other aromatic diisocyanates, ethylene diisocyanate, 2,2 1,4-trimethylhexamethylene diisocyanate, aliphatic diisocyanates such as 1,6-hexamethylene diisocyanate, 1,4-cyclohexane San diisocyanate, cyclohexane diisocyanate, 4,4'-dicyclohexyl methane diisocyanate, isophorone diisocyanate, and cycloaliphatic diisocyanates such as norbornane diisocyanate. These may be used alone or in combination of two or more.

  As the isocyanate component, a trifunctional or higher polyfunctional polyisocyanate compound can be used in addition to the diisocyanate compound. As a polyfunctional isocyanate compound, a series of diisocyanate adduct compounds are commercially available as Desmodur-N (manufactured by Bayer) or trade name Duranate (manufactured by Asahi Kasei Kogyo Co., Ltd.).

  Of the above isocyanate components, 4,4'-diphenylmethane diisocyanate or carbodiimide-modified MDI is preferably used.

  Examples of the high molecular weight polyol include those usually used in the technical field of polyurethane. Examples include polyether polyols typified by polytetramethylene ether glycol, polyethylene glycol, etc., polyester polyols typified by polybutylene adipate, polycaprolactone polyols, reactants of polyester glycols such as polycaprolactone and alkylene carbonate, etc. Polyester polycarbonate polyol obtained by reacting ethylene carbonate with polyhydric alcohol and then reacting the obtained reaction mixture with organic dicarboxylic acid, polycarbonate polyol obtained by transesterification of polyhydroxyl compound and aryl carbonate And polymer polyol which is a polyether polyol in which polymer particles are dispersed.These may be used alone or in combination of two or more.

  Of the high molecular weight polyols, it is preferable to use a high molecular weight polyol having a hydroxyl value of 30 to 200 mgKOH / g. The hydroxyl value is more preferably 100 to 200 mgKOH / g. When the hydroxyl value is less than 30 mg KOH / g, the amount of polyurethane hard segments tends to decrease and the durability tends to decrease. When the hydroxyl value exceeds 200 mg KOH / g, the degree of crosslinking of the polyurethane foam becomes too high. Tend to be brittle.

  In order to produce a polishing layer having the above physical properties, it is preferable to use a polyester-based polyol.

  The high molecular weight polyol is preferably contained in the polyol component in an amount of 60 to 95% by weight, more preferably 70 to 85% by weight. By using a specific amount of the high molecular weight polyol, the cell membrane is easily broken, and an open cell structure is easily formed.

  The number average molecular weight of the high molecular weight polyol is not particularly limited, but is preferably 500 to 3500 from the viewpoint of the elastic properties of the resulting polyurethane. If the number average molecular weight is less than 500, a polyurethane using the number average molecular weight does not have sufficient elastic properties and tends to be a brittle polymer. Therefore, the polishing layer made of this polyurethane foam becomes too hard, and scratches are likely to occur on the surface of the object to be polished. On the other hand, when the number average molecular weight exceeds 3500, polyurethane using the same becomes too soft. Therefore, the durability of the polishing layer made of this polyurethane foam tends to deteriorate.

  In order to make the polyurethane foam into an open cell structure, a polymer polyol may be used. Examples of the polymer polyol include a polymer polyol in which polymer particles made of acrylonitrile and / or a styrene-acrylonitrile copolymer are dispersed.

  Along with high molecular weight polyol, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol, diethylene glycol, triethylene glycol, 1,4-bis (2-hydroxyethoxy) benzene, tri Methylolpropane, glycerin, 1,2,6-hexanetriol, pentaerythritol, tetramethylolcyclohexane, methyl glucoside, sorbitol, mannitol, dulcitol, sucrose, 2,2,6,6-tetrakis (hydroxymethyl) cyclo Hexanol, diethanolamine, N- methyldiethanolamine, and low molecular weight polyols such as triethanolamine may be used in combination. Moreover, low molecular weight polyamines, such as ethylenediamine, tolylenediamine, diphenylmethanediamine, and diethylenetriamine, can also be used in combination. Also, alcohol amines such as monoethanolamine, 2- (2-aminoethylamino) ethanol, and monopropanolamine can be used in combination. These low molecular weight polyols and low molecular weight polyamines may be used alone or in combination of two or more.

  Among these, it is preferable to use a low molecular weight polyol having a hydroxyl value of 400 to 1900 mgKOH / g. The hydroxyl value is more preferably 700 to 1500 mgKOH / g. When the hydroxyl value is less than 400 mgKOH / g, there is a tendency that the effect of improving open cell formation cannot be obtained sufficiently. On the other hand, when the hydroxyl value exceeds 1900 mgKOH / g, scratches tend to occur on the wafer surface. In particular, it is preferable to use diethylene glycol, triethylene glycol, 1,3-butanediol, 1,4-butanediol, trimethylolpropane, or glycerin.

  In order to make the polyurethane foam into an open-cell structure, the low molecular weight polyol having a hydroxyl value is preferably contained in the polyol component in a total amount of 2 to 25% by weight, more preferably 5 to 20% by weight. By using a specific amount of the low molecular weight polyol, the cell membrane is easily broken, and not only is it easy to form open cells, but the mechanical properties of the polyurethane foam are improved.

  When the polyurethane resin is produced by the prepolymer method, a chain extender is used for curing the isocyanate-terminated prepolymer. The chain extender is an organic compound having at least two active hydrogen groups, and examples of the active hydrogen group include a hydroxyl group, a primary or secondary amino group, and a thiol group (SH). Specifically, 4,4′-methylenebis (o-chloroaniline) (MOCA), 2,6-dichloro-p-phenylenediamine, 4,4′-methylenebis (2,3-dichloroaniline), 3,5 -Bis (methylthio) -2,4-toluenediamine, 3,5-bis (methylthio) -2,6-toluenediamine, 3,5-diethyltoluene-2,4-diamine, 3,5-diethyltoluene-2 , 6-diamine, trimethylene glycol-di-p-aminobenzoate, 1,2-bis (2-aminophenylthio) ethane, 4,4′-diamino-3,3′-diethyl-5,5′-dimethyl Diphenylmethane, N, N′-di-sec-butyl-4,4′-diaminodiphenylmethane, 3,3′-diethyl-4,4′-diaminodiphenylmethane, m-xyl Polyamines exemplified by N-diamine, N, N′-di-sec-butyl-p-phenylenediamine, m-phenylenediamine, and p-xylylenediamine, or the low molecular weight polyols and low molecular weight polyamines mentioned above. Can be mentioned. These may be used alone or in combination of two or more.

  The ratio of the isocyanate component, the polyol component, and the chain extender can be variously changed depending on the molecular weight of each, the desired physical properties of the polyurethane foam, and the like. In order to obtain a foam having desired characteristics, the number of isocyanate groups of the isocyanate component relative to the total number of active hydrogen groups (hydroxyl group + amino group) of the polyol component and the chain extender is 0.80 to 1.20. Preferably, it is 0.99 to 1.15. When the number of isocyanate groups is outside the above range, curing failure occurs and the required specific gravity, hardness, compression ratio, etc. tend not to be obtained.

  The polyurethane resin can be produced by applying a known urethanization technique such as a melting method or a solution method, but it is preferably produced by a melting method in consideration of cost, working environment, and the like.

  The polyurethane resin can be produced by either the prepolymer method or the one-shot method.

  In the case of the prepolymer method, an isocyanate-terminated prepolymer having a molecular weight of about 800 to 5000 is preferable because it has excellent processability and physical characteristics.

  In the production of the polyurethane resin, a first component containing an isocyanate group-containing compound and a second component containing an active hydrogen group-containing compound are mixed and cured. In the prepolymer method, the isocyanate-terminated prepolymer becomes an isocyanate group-containing compound, and the chain extender becomes an active hydrogen group-containing compound. In the one-shot method, the isocyanate component becomes an isocyanate group-containing compound, and the chain extender and the polyol component become active hydrogen group-containing compounds.

  The polyurethane foam, which is a material for forming the polishing layer of the present invention, can be produced by a mechanical foaming method (including a mechanical floss method) using a silicon surfactant.

  In particular, a mechanical foaming method using a silicon surfactant which is a polyalkylsiloxane or a copolymer of an alkylsiloxane and a polyetheralkylsiloxane is preferable. Examples of suitable silicon-based surfactants include SH-192 and L-5340 (manufactured by Toray Dow Corning Silicone), B8443 (manufactured by Goldschmidt), and the like.

  The silicon-based surfactant is preferably added to the polyurethane foam in an amount of 0.1 to 10% by weight, and more preferably 0.5 to 7% by weight.

  In addition, you may add stabilizers, such as antioxidant, a lubricant, a pigment, a filler, an antistatic agent, and another additive as needed.

  An example of a method for producing a polyurethane foam constituting the polishing layer will be described below. The manufacturing method of this polyurethane foam has the following processes.

  (1) The first component obtained by adding a silicon surfactant to an isocyanate-terminated prepolymer obtained by reacting an isocyanate component and a high molecular weight polyol is mechanically stirred in the presence of a non-reactive gas, and the non-reactive gas is removed. Disperse as fine bubbles to obtain a cell dispersion. Then, a second component containing a chain extender is added to the cell dispersion and mixed to prepare a cell-dispersed urethane composition. A catalyst may be appropriately added to the second component.

  (2) A component in which a silicon surfactant is added to at least one of a first component containing an isocyanate component (or an isocyanate-terminated prepolymer) and a second component containing an active hydrogen-containing compound, and a silicon surfactant is added Is mechanically stirred in the presence of a non-reactive gas to disperse the non-reactive gas as fine bubbles to obtain a bubble dispersion. Then, the remaining components are added to the cell dispersion and mixed to prepare a cell-dispersed urethane composition.

  (3) A silicon-based surfactant is added to at least one of the first component containing the isocyanate component (or isocyanate-terminated prepolymer) and the second component containing the active hydrogen-containing compound, and the first component and the second component are added. A foam-dispersed urethane composition is prepared by mechanically stirring in the presence of a non-reactive gas and dispersing the non-reactive gas as fine bubbles.

  The cell dispersed urethane composition may be prepared by a mechanical floss method. The mechanical floss method is a method in which raw material components are put into a mixing chamber of a mixing head and a non-reactive gas is mixed and mixed and stirred by a mixer such as an Oaks mixer to make the non-reactive gas into a fine bubble state in the raw material mixture. It is a method of dispersing in. The mechanical floss method is a preferable method because the density of the polyurethane foam can be easily adjusted by adjusting the amount of the non-reactive gas mixed therein. Moreover, since the polyurethane foam which has a substantially spherical fine cell can be continuously shape | molded, manufacturing efficiency is good.

  As the non-reactive gas used to form the fine bubbles, non-flammable gases are preferable, and specific examples include nitrogen, oxygen, carbon dioxide, rare gases such as helium and argon, and mixed gases thereof. In view of cost, it is most preferable to use air that has been dried to remove moisture.

  As the stirring device for dispersing the non-reactive gas in the form of fine bubbles, a known stirring device can be used without any particular limitation. Specifically, a homogenizer, a dissolver, a two-axis planetary mixer (planetary mixer), a mechanical A floss foaming machine etc. are illustrated. The shape of the stirring blade of the stirring device is not particularly limited, but it is preferable to use a whipper type stirring blade because fine bubbles can be obtained. In order to obtain the target polyurethane foam, the rotational speed of the stirring blade is preferably 500 to 2000 rpm, more preferably 800 to 1500 rpm. The stirring time is appropriately adjusted according to the target density.

  In addition, it is also a preferable aspect that the stirring for preparing the cell dispersion in the foaming step and the stirring for mixing the first component and the second component use different stirring devices. The agitation in the mixing step may not be agitation that forms bubbles, and it is preferable to use an agitation device that does not involve large bubbles. As such an agitator, a planetary mixer is suitable. There is no problem even if the same stirring device is used as the stirring device for the foaming step for preparing the bubble dispersion and the mixing step for mixing each component, and the stirring conditions such as adjusting the rotation speed of the stirring blades are adjusted as necessary. It is also suitable to use after adjustment.

  Thereafter, the cell-dispersed urethane composition prepared by the above method is applied onto the base material layer, and the cell-dispersed urethane composition is cured to form a polyurethane foam (polishing layer) directly on the base material layer.

  The substrate layer is not particularly limited. For example, plastic films such as polypropylene, polyethylene, polyester, polyamide, and polyvinyl chloride, polymer resin foams such as polyurethane foam and polyethylene foam, rubber properties such as butadiene rubber and isoprene rubber. Examples thereof include resins and photosensitive resins. Among these, it is preferable to use polymer resin foams such as plastic films such as polypropylene, polyethylene, polyester, polyamide, and polyvinyl chloride, polyurethane foam, and polyethylene foam. Moreover, you may use a double-sided tape and a single-sided adhesive tape (a single-sided adhesive layer is for affixing on a platen) as a base material layer.

  The base material layer is preferably as hard as a polyurethane foam or harder in order to impart toughness to the polishing pad. Moreover, the thickness of the base material layer (the base material in the case of double-sided tape and single-sided adhesive tape) is not particularly limited, but is preferably 20 to 1000 μm, more preferably 50 to 50 μm from the viewpoint of strength, flexibility, and the like. 800 μm.

  As a method for applying the cell-dispersed urethane composition onto the base material layer, for example, a roll coater such as gravure, kiss, or comma, a die coater such as slot or phanten, a squeeze coater, or a curtain coater is adopted. Any method may be used as long as a uniform coating film can be formed on the base material layer.

  Heating and post-curing the polyurethane foam that has reacted until the cell-dispersed urethane composition is applied to the base material layer and no longer flows is effective in improving the physical properties of the polyurethane foam and is extremely suitable. is there. Post-cure is preferably performed at 30 to 80 ° C. for 10 minutes to 6 hours, and it is preferable to perform at normal pressure because the bubble shape becomes stable.

  In the production of a polyurethane foam, a known catalyst for promoting a polyurethane reaction such as a tertiary amine may be used. The type and addition amount of the catalyst are selected in consideration of the flow time for coating on the substrate layer after the mixing step of each component.

  The polyurethane foam may be produced by a batch method in which each component is weighed and put into a container and mechanically stirred, and each component and a non-reactive gas are continuously supplied to a stirring device and mechanically stirred. Further, a continuous production method in which a cell-dispersed urethane composition is sent out to produce a molded product may be used.

  Moreover, after forming a polyurethane foam on a base material layer, or forming a polyurethane foam simultaneously, it is preferable to adjust the thickness of a polyurethane foam uniformly. The method for uniformly adjusting the thickness of the polyurethane foam is not particularly limited, and examples thereof include a method of buffing with an abrasive and a method of pressing with a press plate.

  Moreover, the cell-dispersed urethane composition prepared by the above method is applied on the base material layer, and a release sheet is laminated on the cell-dispersed urethane composition. Thereafter, the polyurethane foam may be formed by curing the cell-dispersed urethane composition while making the thickness uniform by a pressing means.

  On the other hand, the cell-dispersed urethane composition prepared by the above method is applied onto a release sheet, and a base material layer is laminated on the cell-dispersed urethane composition. Thereafter, the polyurethane foam may be formed by curing the cell-dispersed urethane composition while making the thickness uniform by a pressing means.

  The material for forming the release sheet is not particularly limited, and examples thereof include general resin and paper. The release sheet preferably has a small dimensional change due to heat. The surface of the release sheet may be subjected to a release treatment.

  The pressing means for making the thickness of the sandwich sheet composed of the base material layer, the cell-dispersed urethane composition (cell-dispersed urethane layer), and the release sheet is not particularly limited. For example, the thickness may be constant by a coater roll, a nip roll, or the like. The method of compressing is mentioned. In consideration of the fact that the bubbles in the foam are increased by about 1.2 to 2 times after compression, (coating or nip clearance)-(base layer and release sheet thickness) = (after curing) The thickness of the polyurethane foam is preferably 50 to 85%.

  Then, after the thickness of the sandwich sheet is made uniform, the reacted polyurethane foam is heated until it does not flow and post-cured to form a polishing layer. Post cure conditions are the same as described above.

  Thereafter, the release sheet on the upper surface side or the lower surface side of the polyurethane foam is peeled to obtain a polishing pad. In this case, since the skin layer is formed on the polyurethane foam, the skin layer is removed by buffing or the like. Further, when the polyurethane foam is formed by the mechanical foaming method as described above, the variation in bubbles is smaller on the lower surface side than on the upper surface side of the polyurethane foam. Therefore, when the release sheet on the lower surface side is peeled off and the lower surface side of the polyurethane foam is used as the polishing surface, the polishing surface has a small variation in bubbles, and the stability of the polishing rate is further improved.

  Alternatively, the polyurethane foam (polishing layer) may not be formed directly on the base material layer, but may be bonded to the base material layer using a double-sided tape after forming the polishing layer.

  The shape of the polishing pad of the present invention is not particularly limited, and may be a long shape of about several meters in length or a round shape having a diameter of several tens of centimeters.

  The average cell diameter of the polyurethane foam is preferably 35 to 300 μm, more preferably 35 to 100 μm, and particularly preferably 40 to 80 μm. When deviating from this range, the polishing rate decreases or the durability decreases.

  The specific gravity of the polyurethane foam is preferably 0.2 to 0.6, more preferably 0.3 to 0.5. When the specific gravity is less than 0.2, the durability of the polishing layer tends to decrease. On the other hand, if it is larger than 0.6, the material needs to have a low crosslinking density in order to obtain a certain elastic modulus. In that case, the permanent set increases and the durability tends to deteriorate.

  The polishing layer of the present invention has a glass transition temperature (Tg) in the range of 20 ° C. to 90 ° C., and a storage elastic modulus E ′ (Tg) at the glass transition temperature (Tg) and a glass transition temperature (Tg). The ratio [E ′ (Tg−20 ° C.) / E ′ (Tg)] to the storage elastic modulus E ′ (Tg−20 ° C.) at a temperature lower by 20 ° C. is 10 or more. The glass transition temperature (Tg) is preferably in the range of 30 ° C. to 80 ° C., and the storage modulus ratio A is preferably 20 or more.

  Further, the polishing layer preferably has a storage elastic modulus E ′ (Tg−20 ° C.) of 70 MPa or more, more preferably 100 MPa or more, and particularly preferably 150 MPa or more.

  The polishing layer has a storage elastic modulus E ′ (Tg−20 ° C.) at a temperature 20 ° C. lower than the glass transition temperature (Tg) and a storage elastic modulus E ′ (Tg) at a temperature 40 ° C. lower than the glass transition temperature (Tg). The ratio [E ′ (Tg−40 ° C.) / E ′ (Tg−20 ° C.)] to −40 ° C. is preferably 2 or less, and more preferably 1.7 or less.

  The surface of the polishing layer may have a concavo-convex structure for holding and renewing the slurry. The polishing layer made of foam has many openings on the polishing surface and has the function of holding and updating the slurry. By forming a concavo-convex structure on the polishing surface, the slurry can be held and updated more efficiently. It can be performed well, and destruction of the polishing object due to adsorption with the polishing object can be prevented. The concavo-convex structure is not particularly limited as long as it is a shape that holds and renews the slurry. For example, an XY lattice groove, a concentric circular groove, a through hole, a non-penetrating hole, a polygonal column, a cylinder, a spiral groove, Examples include eccentric circular grooves, radial grooves, and combinations of these grooves. In addition, these uneven structures are generally regular, but in order to make the slurry retention and renewability desirable, the groove pitch, groove width, groove depth, etc. should be changed for each range. Is also possible.

  The method for producing the concavo-convex structure is not particularly limited. For example, a method of machine cutting using a jig such as a tool of a predetermined size, pouring a resin into a mold having a predetermined surface shape, and curing. Using a press plate having a predetermined surface shape, a method of producing a resin by pressing, a method of producing using photolithography, a method of producing using a printing technique, a carbon dioxide laser, etc. Examples include a manufacturing method using laser light.

  The thickness of the polishing layer is not particularly limited, but is usually about 0.2 to 2 mm, and preferably 0.5 to 1.5 mm.

  The polishing pad of the present invention may be provided with a double-sided tape on the surface to be bonded to the platen.

  The polishing pad of the present invention is used for rough polishing and finish polishing of optical materials such as lenses and reflection mirrors, semiconductor wafers, glass substrates for hard disks, and aluminum substrates.

  For example, a semiconductor device is manufactured through a step of polishing the surface of a semiconductor wafer using the polishing pad. A semiconductor wafer is generally a laminate of a wiring metal and an oxide film on a silicon wafer. The polishing apparatus is not particularly limited. For example, as shown in FIG. 1, a polishing platen 2 that supports the polishing pad 1, a support table (polishing head) 5 that supports the semiconductor wafer 4, and uniform pressure on the wafer are performed. For example, a polishing apparatus equipped with a backing material and a supply mechanism for the abrasive 3 is used. The polishing pad 1 is attached to the polishing surface plate 2 by attaching it with a double-sided tape, for example. The polishing surface plate 2 and the support base 5 are disposed so that the polishing pad 1 and the semiconductor wafer 4 supported on each of the polishing surface plate 2 and the support table 5 face each other, and are provided with rotating shafts 6 and 7 respectively. Further, a pressurizing mechanism for pressing the semiconductor wafer 4 against the polishing pad 1 is provided on the support base 5 side. In polishing, the semiconductor wafer 4 is pressed against the polishing pad 1 while rotating the polishing surface plate 2 and the support base 5, and polishing is performed while supplying slurry. The flow rate of the slurry, the polishing load, the polishing platen rotation speed, and the wafer rotation speed are not particularly limited and are appropriately adjusted.

  When the polishing pad of the present invention is used, rough polishing is performed in a temperature environment where the storage elastic modulus E ′ of the polishing layer is 70 MPa or more, and finish polishing is performed in a temperature environment where the storage elastic modulus E ′ of the polishing layer is 10 MPa or less. It is preferable to carry out. In particular, it is preferable to use a polishing layer having a storage elastic modulus of 70 MPa or more at a temperature lower than Tg by about 10 ° C. or more and a storage elastic modulus of 10 MPa or less at a temperature lower by about 3 ° C. than Tg.

  By the polishing step, the surface roughness of the surface of the semiconductor wafer 4 is improved and scratches are removed. Thereafter, a semiconductor device is manufactured by dicing, bonding, packaging, or the like. The semiconductor device is used for an arithmetic processing device, a memory, and the like.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated, this invention is not limited to these Examples.

[Measurement and evaluation methods]
(Measurement of average bubble diameter)
A sample obtained by cutting the produced polyurethane foam in parallel with a razor blade as thin as possible to a thickness of 1 mm or less was used as a sample. The sample was fixed on a glass slide and observed at 100 times using SEM (S-3500N, Hitachi Science Systems, Ltd.). Using the image analysis software (WinRoof, Mitani Shoji Co., Ltd.) for the obtained image, the total bubble diameter in an arbitrary range was measured, and the average bubble diameter was calculated. However, in the case of an oval spherical bubble, the area was converted to a circle area, and the equivalent circle diameter was taken as the bubble diameter.

(Measurement of specific gravity)
This was performed according to JIS Z8807-1976. The produced polyurethane foam was cut into a 4 cm × 8.5 cm strip (thickness: arbitrary) as a sample and allowed to stand for 16 hours in an environment of temperature 23 ° C. ± 2 ° C. and humidity 50% ± 5%. The specific gravity was measured using a hydrometer (manufactured by Sartorius).

(Measurement of storage modulus and glass transition temperature)
The storage elastic modulus of the polishing layer was measured under the following conditions using a dynamic viscoelasticity measuring device (manufactured by METTLER TOLEDO, DMA861e). The peak temperature of tan δ obtained by the measurement was defined as the glass transition temperature.
Frequency: 1.6Hz
Temperature increase rate: 2.0 ° C / min
Measurement temperature range: 0-90 ° C
Sample shape: length 19.5mm, width 3.0mm, thickness 1.0mm

Example 1
In a container, polyethylene adipate (manufactured by Nippon Polyurethane, N4002, number average molecular weight: 1000, hydroxyl value: 110 mgKOH / g) 84 parts by weight, glycerin (hydroxyl value: 1824 mgKOH / g), 3 parts by weight, 1,3-butanediol (hydroxyl value) : 1247 mg KOH / g) 13 parts by weight, silicon surfactant (manufactured by Goldschmidt, B8443) 6 parts by weight, and catalyst (No. 25, manufactured by Kao) 0.07 part by weight were mixed. And it stirred vigorously for about 4 minutes so that a bubble might be taken in in a reaction system with the rotation speed of 900 rpm using the stirring blade. Thereafter, 87.81 parts by weight of Millionate MTL (manufactured by Nippon Polyurethane) was added and stirred for about 1 minute to prepare a cell dispersed urethane composition.

  The prepared cell-dispersed urethane composition was applied onto a release-treated release sheet (Toyobo, polyethylene terephthalate, thickness: 0.1 mm) to form a cell-dispersed urethane layer. And the base material layer (polyethylene terephthalate, thickness: 0.2 mm) was covered on this cell dispersion | distribution urethane layer. The cell-dispersed urethane layer was made 1.2 mm thick with a nip roll and then cured at 70 ° C. for 3 hours to form a polyurethane foam (open cell structure, average cell diameter: 65 μm, specific gravity: 0.50). Thereafter, the release sheet on the polyurethane foam was peeled off. Next, the surface of the polyurethane foam was sliced using a band saw type slicer (manufactured by Fecken) to adjust the thickness accuracy to 1.0 mm, thereby adjusting the thickness accuracy. Thereafter, a double-sided tape (double tack tape, manufactured by Sekisui Chemical Co., Ltd.) was bonded to the surface of the base material layer using a laminator to prepare a polishing pad.

Examples 2-5, Comparative Examples 1-3
A polishing pad was prepared in the same manner as in Example 1 with the formulation shown in Table 1. The compounds in Table 1 are as follows.
N4009: Made of Nippon Polyurethane, polybutylene adipate, number average molecular weight: 1000, hydroxyl value: 110 mgKOH / g
N981: Made of Nippon Polyurethane, polycarbonate diol, number average molecular weight: 1000, hydroxyl value: 110 mgKOH / g
PTMG 2000: manufactured by Mitsubishi Chemical, hydroxyl value: 56 mgKOH / g
PCL305: manufactured by Daicel Chemical Industries, polycaprolactone triol, number average molecular weight 550, hydroxyl value: 305 mgKOH / g

Comparative Example 4
IC1000 (Rodel) was bonded to a base material layer (polyethylene terephthalate, thickness: 0.2 mm) using a double-sided tape (double tack tape, manufactured by Sekisui Chemical Co., Ltd.) to prepare a polishing pad.

Schematic configuration diagram showing an example of a polishing apparatus used in CMP polishing

Explanation of symbols

1: Polishing pad 2: Polishing surface plate 3: Abrasive (slurry)
4: Polishing target (semiconductor wafer, lens, glass plate)
5: Support base (polishing head)
6, 7: Rotating shaft

Claims (4)

In the polishing pad provided with the polishing layer on the base material layer, the polishing layer is made of a thermosetting polyurethane foam containing substantially spherical open cells,
The polishing layer has a glass transition temperature (Tg) in the range of 20 ° C. to 90 ° C., and 20 ° C. from the storage elastic modulus E ′ (Tg) at the glass transition temperature (Tg) and the glass transition temperature (Tg). A polishing pad having a ratio [E ′ (Tg−20 ° C.) / E ′ (Tg)] to a storage elastic modulus E ′ (Tg−20 ° C.) at a low temperature of 10 or more. The polishing pad according to claim 1, wherein the polishing layer has a storage elastic modulus E ′ (Tg−20 ° C.) of 70 MPa or more. The polishing layer has a storage elastic modulus E ′ (Tg−20 ° C.) at a temperature 20 ° C. lower than the glass transition temperature (Tg) and a storage elastic modulus E ′ (Tg−) at a temperature 40 ° C. lower than the glass transition temperature (Tg). The polishing pad according to claim 1, wherein the ratio [E ′ (Tg−40 ° C.) / E ′ (Tg−20 ° C.)] is 40 or less. Using the polishing pad according to any one of claims 1 to 3, rough polishing is performed in a temperature environment where the storage elastic modulus E 'of the polishing layer is 70 MPa or more, and the storage elastic modulus E' of the polishing layer is 10 MPa. A polishing method of a polishing object, comprising performing finish polishing in a temperature environment as described below.

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