JP2010167512A - Polishing pad and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing pad with which polishing speed is high due to excellent wettability of a polishing pad surface with slurry and an edge of an object to be polished is hard to be excessively polished. <P>SOLUTION: The polishing pad is equipped with a polishing layer on a base material layer. The polishing layer is made of thermosetting polyurethane foam including a continuum of approximately spherical air bubbles. The thermosetting polyurethane foam is a reactive hardened body of a urethane composition containing an isocyanate component and an active-hydrogen-containing compound. The active-hydrogen-containing compound contains carboxyl-group-containing polymeric polyol. A content of the carboxyl group with respect to a total weight of the active-hydrogen-containing compound ranges from 0.3 to 3 wt.%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polishing pad (for rough polishing or finish polishing) used for polishing surfaces of optical materials such as lenses and reflection mirrors, silicon wafers, glass substrates for hard disks, and aluminum substrates. In particular, the polishing pad of the present invention is suitably used as a polishing pad for finishing.

  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).

  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 2, 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.

In Patent Document 3, for the purpose of providing a polishing pad having good flatness, in-plane uniformity, polishing rate, little change in polishing rate, and excellent life characteristics, ethylene oxide units (—CH ₂ It describes that a polishing pad is prepared using a hydrophilic isocyanate-terminated prepolymer comprising a hydrophilic high molecular weight polyol component having CH ₂ O—) and an isocyanate component as raw material components.

  However, since the polishing pad described in Patent Document 3 introduces ethylene oxide, which is a hydrophilic group, into the polyurethane main chain, the polishing pad may swell during polishing and change polishing characteristics.

  Further, Patent Document 4 discloses that a polishing pad having a large polishing rate, a small change in the polishing rate, and hardly causing scratches on the surface of an object to be polished is provided with a carboxyl group on the molecular side chain of the polyurethane resin. The introduction of at least one hydrophilic group selected from the group consisting of a group, a sulfonic acid group, a phosphoric acid group, and salts thereof is described.

  However, in Patent Document 4, since the hydrophilic group is introduced into the hard segment portion of the polyurethane resin, the effect of improving the wettability of the polishing pad surface with respect to the slurry is insufficient. Therefore, there is a tendency that a sufficient polishing rate cannot be obtained.

  Further, in recent years, in order to manufacture as many semiconductor chips as possible from one wafer, a polishing pad that can be uniformly flattened to the wafer edge portion has been demanded. However, when the above polishing pad is used, a large pressure is applied to the edge portion of the wafer due to the deformation of the pad, and there is a problem in that the edge portion called “edge fringing” is overpolished.

JP 2003-37089 A JP 2006-75914 A JP 2005-68175 A JP 2007-276061 A

  An object of the present invention is to provide a polishing pad that has a high polishing rate and is less prone to overpolishing of an edge portion of an object to be polished because wettability of a polishing pad surface to a slurry is excellent.

  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 in which a polishing layer is provided on a base material layer,
The polishing layer is made of a thermosetting polyurethane foam having substantially spherical open cells,
The thermosetting polyurethane foam is a reaction cured product of a urethane composition containing an isocyanate component and an active hydrogen-containing compound,
The active hydrogen-containing compound contains a carboxyl group-containing high molecular weight polyol,
The present invention relates to a polishing pad having a carboxyl group content of 0.3 to 3% by weight based on the total weight of the active hydrogen-containing compound.

  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.

  In addition, the present inventors introduced a carboxyl group, which is a hydrophilic group, into the molecular side chain of the polyurethane resin and into the soft segment portion of the polyurethane resin, thereby improving the wettability of the polishing pad surface to the slurry and polishing. It has been found that the speed is increased, the polishing speed at the center of the object to be polished is improved, and the overpolishing at the edge is relatively reduced.

  In the present invention, a carboxyl group-containing high molecular weight polyol is used as the active hydrogen-containing compound which is a raw material of the thermosetting polyurethane foam, and the carboxyl group content relative to the total weight of the active hydrogen-containing compound is 0.00. It must be 3 to 3% by weight. When the carboxyl group content is less than 0.3% by weight, the polishing rate cannot be increased because the wettability of the polishing pad surface to the slurry is not improved, and the polishing rate at the center of the object to be polished is low. Since it does not become large, over-polishing of the edge portion is likely to occur. On the other hand, when the carboxyl group content exceeds 3% by weight, the reaction with the isocyanate component is likely to occur, and a thermosetting polyurethane foam having the desired structure and physical properties cannot be obtained.

  The carboxyl group-containing high molecular weight polyol is preferably a lactone high molecular weight polyol obtained by a ring-opening polymerization reaction of a lactone monomer and dimethylolalkanoic acid. By using the lactone-based high molecular weight polyol, swelling of the polishing layer due to the slurry can be suppressed, and deterioration of the dimensional stability and hardness of the polishing layer can be suppressed.

  In addition, the present invention provides a process for preparing a cell-dispersed urethane composition containing an isocyanate component, an active hydrogen-containing compound containing a carboxyl group-containing high-molecular-weight polyol, and a silicon surfactant by a mechanical foaming method, on the base material layer The step of applying the cell-dispersed urethane composition, the step of forming a thermosetting polyurethane foam having substantially spherical open cells by curing the cell-dispersed urethane composition, and the thickness of the thermosetting polyurethane foam The present invention relates to a polishing pad manufacturing method including a step of uniformly forming a polishing layer.

  Further, the present invention provides a process for preparing a cell-dispersed urethane composition containing an isocyanate component, an active hydrogen-containing compound containing a carboxyl group-containing high molecular weight polyol, and a silicon surfactant by a mechanical foaming method, on a release sheet. A step of applying a cell-dispersed urethane composition, a step of laminating a base material layer on the cell-dispersed urethane composition, a substantially spherical continuous cell by curing the cell-dispersed urethane composition while making the thickness uniform by pressing means Forming a thermosetting polyurethane foam having a surface, removing a release sheet under the thermosetting polyurethane foam, and removing a skin layer on the surface of the exposed thermosetting polyurethane foam to form a polishing layer The manufacturing method of the polishing pad including the process to do.

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

  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.

  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 and an active hydrogen-containing compound (high molecular weight polyol, low molecular weight polyol, low molecular weight polyamine, etc.).

  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.

  In the present invention, it is necessary to use a carboxyl group-containing high molecular weight polyol as the high molecular weight polyol, and in particular, to use a lactone-based high molecular weight polyol obtained by a ring-opening polymerization reaction between a lactone monomer and dimethylolalkanoic acid. preferable.

  Examples of the lactone monomer include δ-valerolactone, β-methyl-δ-valerolactone, ε-caprolactone, α-methyl-ε-caprolactone, β-methyl-ε-caprolactone, γ-methyl-ε-caprolactone, β , δ-dimethyl-ε-caprolactone, 3,3,5-trimethyl-ε-caprolactone, enanthlactone, dodecanolactone and the like. These may be used alone or in combination of two or more. Among these, it is preferable to use an ε-caprolactone monomer.

  Examples of dimethylolalkanoic acid include dimethylolpropionic acid, dimethylolbutanoic acid, dimethylolpentanoic acid, dimethylolheptanoic acid, dimethyloloctanoic acid, dimethylolnonanoic acid, and the like. These may be used alone or in combination of two or more. Of these, dimethylolpropionic acid and dimethylolbutanoic acid are preferably used.

  The lactone high molecular weight polyol can be synthesized by a known method using an organotin catalyst used for ring-opening polymerization of a lactone monomer. The carboxyl group may be neutralized in advance using an appropriate basic compound (such as amine) so as not to react with the isocyanate group.

  The number average molecular weight of the lactone-based high molecular weight polyol is not particularly limited, but is preferably 500 to 2000, more preferably 500 to 1500 from the viewpoints of reactivity, compatibility, and elastic properties of polyurethane. It is.

  From the viewpoint of reactivity and wettability of the polishing pad surface, the lactone-based high molecular weight polyol is preferably contained in the total active hydrogen-containing compound in an amount of 3 to 40% by weight, more preferably 5 to 30% by weight.

  Moreover, in this invention, the content rate of the carboxyl group with respect to the total weight of an active hydrogen containing compound (however, when the carboxyl group is neutralized and it is converted into a salt, it calculates by converting into a carboxyl group). It is necessary to adjust so that it may become 0.3 to 3 weight%. The carboxyl group content is preferably 0.4 to 2.7% by weight.

  In the present invention, it is preferable to use polycaprolactone polyol together with the lactone-based high molecular weight polyol. Examples of the polycaprolactone polyol include polycaprolactone diol, polycaprolactone triol, and polycaprolactone tetraol. These may be used alone or in combination of two or more. In particular, it is preferable to use polycaprolactone triol that can increase the strength of the polishing pad by crosslinking. The polycaprolactone polyol is preferably used in an amount of 10 to 70% by weight, more preferably 20 to 60% by weight in the total active hydrogen group-containing compound.

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

  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, dipropylene glycol, triethylene glycol, 1,4-bis (2-hydroxyethoxy) ) Benzene, trimethylolpropane, glycerin, 1,2,6-hexanetriol, pentaerythritol, tetramethylolcyclohexane, methylglucoside, sorbitol, mannitol, dulcitol, sucrose, 2,2,6,6-tetrakis ( Dorokishimechiru) cyclohexanol, diethanolamine, N- methyldiethanolamine, and can be used in combination of low molecular weight polyols such as triethanolamine. 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 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 1830 mgKOH / g and / or a low molecular weight polyamine having an amine value of 400 to 1870 mgKOH / g. The hydroxyl value is more preferably 900 to 1500 mgKOH / g, and the amine value is more preferably 400 to 950 mgKOH / g. When the hydroxyl value is less than 400 mgKOH / g or the amine value is less than 400 mgKOH / g, the effect of improving the formation of open cells tends to be insufficient. On the other hand, when the hydroxyl value exceeds 1830 mgKOH / g or the amine value exceeds 1870 mgKOH / g, scratches tend to occur on the wafer surface. In particular, it is preferable to use diethylene glycol, dipropylene glycol, 1,2-propylene glycol, 1,3-butanediol, 1,4-butanediol, or trimethylolpropane.

  The low molecular weight polyol, the low molecular weight polyamine, and the alcohol amine are preferably contained in a total amount of 30% by weight or less, more preferably 5 to 20% by weight, in the total active hydrogen-containing compound. By using a specific amount of the low molecular weight polyol or the like, not only the bubble film is easily broken and it becomes easy to form open cells, but also the mechanical properties of the polyurethane foam are improved.

  The ratio of the isocyanate component and the active hydrogen-containing compound can be variously changed depending on the molecular weight of each and the desired physical properties of the polyurethane foam. 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 active hydrogen-containing compound is preferably 0.80 to 1.20, More 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.

  In the present invention, the polyurethane foam is produced by the one-shot method. Specifically, the polyurethane foam which is the 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-based 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 surfactants include SH-192 and L-5340 (manufactured by Toray Dow Corning Silicone), B8443, B8465 (manufactured by Goldschmidt), and the like.

  The silicon-based surfactant is preferably added in an amount of 0.1 to 10% by weight, more preferably 0.5 to 5% by weight, in the polyurethane foam.

  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) A silicon-based surfactant is added to at least one of the first component containing the isocyanate component and the second component containing the active hydrogen-containing compound, and the component to which the silicon-based surfactant is added is present as a non-reactive gas. Under mechanical stirring, the non-reactive gas is dispersed 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.

  (2) A silicon-based surfactant is added to at least one of the first component containing the isocyanate component and the second component containing the active hydrogen-containing compound, and the first component and the second component are added in the presence of a non-reactive gas. Then, a non-reactive gas is dispersed as fine bubbles to prepare a cell-dispersed urethane composition.

  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 specific gravity 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 a 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. Further, the stirring time is appropriately adjusted according to the target specific gravity.

  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 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 slicing. Moreover, you may slice to predetermined thickness in order to adjust the thickness of a polishing layer. 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 polishing layer produced by the above method has an open cell structure, and the average cell diameter of the open cells is about 35 to 200 μm, preferably 40 to 100 μm.

  When the average bubble diameter of the continuous bubbles is less than 35 μm, polishing scraps (particularly, pad scraps) are accumulated, and the bubbles tend not to sufficiently perform the role of holding the slurry. On the other hand, when the average bubble diameter exceeds 200 μm, the surface roughness of the polished object after polishing becomes large, or “sagging” is likely to occur when pressure is repeatedly applied to the polishing layer, resulting in durability. Since it becomes scarce, it is not preferable.

  The specific gravity of the polishing layer is preferably 0.3 to 0.7, more preferably 0.35 to 0.6. When the specific gravity is less than 0.3, the durability of the polishing layer tends to decrease. On the other hand, when the ratio is larger than 0.7, it is necessary to make the material 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 hardness of the polishing layer is preferably 10 to 95 degrees, more preferably 40 to 90 degrees, using an Asker A hardness meter. When the Asker A hardness is less than 10 degrees, the durability of the polishing layer tends to decrease, or the surface smoothness of the polished object after polishing tends to deteriorate. On the other hand, if it exceeds 95 degrees, scratches are likely to occur on the surface of the object to be polished.

  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.

  A polishing method and a polishing apparatus for the polishing target object 4 such as a semiconductor wafer, a lens, and a glass plate are not particularly limited. For example, as shown in FIG. A polishing table equipped with a support 5 (polishing head) 5 for supporting the wafer, a backing material for uniformly pressing the wafer, a supply mechanism for the abrasive 3, and the like. 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 arranged so that the polishing pad 1 and the object to be polished 4 supported on each of them are opposed to each other, and are provided with rotating shafts 6 and 7 respectively. Further, a pressure mechanism for pressing the polishing object 4 against the polishing pad 1 is provided on the support base 5 side. At the time of polishing, the polishing object 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. Thereby, the surface roughness of the surface of the polishing object 4 is improved, and scratches are removed.

  Hereinafter, the present invention will be described with reference to examples, but the present 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 Corp.), the obtained images were measured for the bubble diameter (diameter) of all open bubbles in an arbitrary range, and the average bubble diameter was calculated. However, in the case of elliptical bubbles, the area was converted to the area of a circle, 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 hardness)
This was performed according to JIS K-7312. The produced polyurethane foam was cut into a size of 5 cm × 5 cm (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%. At the time of measurement, the samples were overlapped to have a thickness of 10 mm or more. Using a hardness meter (manufactured by Kobunshi Keiki Co., Ltd., Asker A type hardness meter, pressure surface height: 3 mm), the hardness 60 seconds after contacting the pressure surface was measured.

(Measurement of elongation)
Non-foamed polyurethane (solid) was prepared according to the formulation shown in Table 1, and samples of 50 mm length × 20 mm width × 2 mm thickness were cut out. Each sample was immersed in water at 23 ° C. for 1 week, and then the sample was taken out and the vertical length (L) was measured. The elongation was calculated according to the following formula.
Elongation rate (%) = {(L-50) / 50} × 100

(Measurement of wetting tension)
This was performed in accordance with JIS K-6768. A reagent (manufactured by Wako Pure Chemical Industries, Ltd., a wet tension test mixed solution) was dropped on the surface of the polyurethane foam after the buff treatment, and the measurement was performed. The higher the wetting tension (mN / m), the better the surface wettability.

(Measurement of polishing rate)
Using SPP600S (manufactured by Okamoto Machine Tool Co., Ltd.) as a polishing apparatus, the polishing rate of the manufactured polishing pad was measured. Table 2 shows the polishing rate of the 100th glass plate. The polishing conditions are as follows.
Glass plate: 6 inches φ, thickness 1.1 mm (optical glass, BK7)
Slurry: Ceria slurry (Showa Denko GPL C1010)
Slurry amount: 100 ml / min
Polishing pressure: 10kPa
Polishing platen rotation speed: 55rpm
Glass plate rotation speed: 50 rpm
Polishing time: 10 min / number of polished glass plates: 100 The method for calculating the polishing rate is as follows.
Polishing rate (Å / min) = [weight change amount of glass plate before and after polishing [g] / (glass plate density [g / cm ³ ] × glass plate polishing area [cm ² ] × polishing time [min])] × 10 ⁸

(Rating evaluation)
Using New View 6300 manufactured by ZYGO, the outer peripheral portion of the 100th glass plate after the polishing (region of 61 mm to 66 mm from the center of the glass plate) under the conditions of lens magnification 2.5 and zoom magnification 0.5 ) Was measured. Points 61.5 mm, 62.5 mm, and 65.1 mm from the center of the glass plate are A point, B point, and C point in order, and the extension line connecting point A and B is a straight line in the thickness direction at C point. The intersecting point was defined as D point, and the distance between C point and D point was defined as edge sag (nm). It can be said that the smaller the value, the better the edge sagging.

Example 1
In a container, 10 parts by weight of a lactone-based polyol (produced by Daicel Chemical Industries, PCL205BA, number average molecular weight: 500) obtained by a ring-opening polymerization reaction of ε-caprolactone and dimethylolbutanoic acid, polytetramethylene ether glycol (manufactured by Mitsubishi Chemical, PTMG1000, number of functional groups: 2, hydroxyl value: 112 mgKOH / g) 20 parts by weight, polycaprolactone triol (manufactured by Daicel Chemical, PCL305, number of functional groups: 3, hydroxyl value: 305 mgKOH / g), 55 parts by weight, dipropylene glycol (DPG, The number of functional groups: 2, hydroxyl value: 835 mg KOH / g) 15 parts by weight, and 3 parts by weight of a silicon surfactant (manufactured by Goldschmidt, B8443) 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, 95.77 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 (manufactured by 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). Thereafter, the release sheet was peeled from the polyurethane foam. Next, the surface of the polyurethane foam was sliced using a band saw type slicer (manufactured by Fecken) to a thickness of 1.0 mm, and the thickness accuracy was adjusted by buffing (# 120). 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 2-7, Comparative Examples 1-4
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.
PCL210BA (manufactured by Daicel Chemical Industries, lactone-based polyol obtained by ring-opening polymerization reaction of ε-caprolactone and dimethylolbutanoic acid, number average molecular weight: 1000)
PCL205 (manufactured by Daicel Chemical Industries, polycaprolactone diol, number of functional groups: 2, hydroxyl value: 212 mgKOH / g)
PCL210N (manufactured by Daicel Chemical Industries, polycaprolactone diol, number of functional groups: 2, hydroxyl value: 110 mgKOH / g)
PEG1000 (Daiichi Kogyo Seiyaku, polyethylene glycol, number average molecular weight: 1000)
DEG (diethylene glycol, functional group number: 2, hydroxyl value: 1057 mg KOH / g)
・ No. 25 (manufactured by Kao, Kao Riser No. 25, catalyst)

Comparative Example 5
In a reaction vessel, polytetramethylene glycol (manufactured by Mitsubishi Chemical Corporation, PTMG-1000, number average molecular weight 1018) 543 parts by weight, 2,2-bis (hydroxymethyl) butanoic acid (manufactured by Nippon Kasei Co., Ltd., DMBA) 16 parts by weight, and 45 parts by weight of diethylene glycol (DEG) was added, and dehydration under reduced pressure was performed for about 1 hour with stirring. Thereafter, the inside of the reaction vessel was purged with nitrogen. Then, 278 parts by weight of toluene diisocyanate (mixture of Mitsui Takeda Chemical Co., TDI-80, 2,4-isomer / 2,6-isomer = 80/20) and isophorone diisocyanate (degussa, IPDI) were added to the reaction vessel. 118 parts by weight were added. And it was made to react for about 4 hours, maintaining the temperature in a reaction system at about 80 degreeC, and the isocyanate terminal prepolymer was synthesize | combined. Thereafter, 11 parts by weight of triethylamine was added to completely neutralize the carboxyl group of the isocyanate-terminated prepolymer.

  100 parts by weight of the prepolymer and 3 parts by weight of a silicon surfactant (manufactured by Goldschmidt, B8443) were mixed, adjusted to 60 ° C. and degassed under reduced pressure. Thereafter, the mixture was vigorously stirred for about 4 minutes so that bubbles were taken into the reaction system at a rotation speed of 900 rpm using a stirring blade. Thereto was added 26 parts by weight of 4,4′-methylenebis (o-chloroaniline) (Ihara Chemical Amine, Iharacamine MT) previously melted at 120 ° C. and stirred for about 1 minute to obtain a cell dispersed urethane composition. Prepared. Thereafter, a polishing pad was produced in the same manner as in Example 1.

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 having substantially spherical open cells,
The thermosetting polyurethane foam is a reaction cured product of a urethane composition containing an isocyanate component and an active hydrogen-containing compound,
The active hydrogen-containing compound contains a carboxyl group-containing high molecular weight polyol,
A polishing pad, wherein the content of carboxyl groups is 0.3 to 3% by weight relative to the total weight of the active hydrogen-containing compound. The polishing pad according to claim 1, wherein the carboxyl group-containing high molecular weight polyol is a lactone-based high molecular weight polyol obtained by a ring-opening polymerization reaction between a lactone monomer and dimethylolalkanoic acid. A step of preparing a cell-dispersed urethane composition containing an isocyanate component, an active hydrogen-containing compound containing a carboxyl group-containing high-molecular-weight polyol, and a silicon-based surfactant by a mechanical foaming method, a cell-dispersed urethane composition on a substrate layer The step of applying, the step of forming a thermosetting polyurethane foam having substantially spherical open cells by curing the cell-dispersed urethane composition, and the thickness of the thermosetting polyurethane foam are uniformly adjusted and polished A method for producing a polishing pad, comprising a step of forming a layer. A step of preparing a cell-dispersed urethane composition containing an isocyanate component, an active hydrogen-containing compound containing a carboxyl group-containing high-molecular-weight polyol, and a silicon surfactant by a mechanical foaming method, and a cell-dispersed urethane composition on a release sheet The step of applying, the step of laminating the base material layer on the cell-dispersed urethane composition, the thermosetting polyurethane having substantially spherical open cells by curing the cell-dispersed urethane composition while making the thickness uniform by pressing means A polishing pad comprising a step of forming a foam, a step of peeling a release sheet under the thermosetting polyurethane foam, and a step of forming a polishing layer by removing the skin layer on the surface of the exposed thermosetting polyurethane foam Manufacturing method.

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