JP2009214220A - Polishing pad - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing pad excellent in durability, hardly generating edge-dropping and making shortening of a dummy polishing time and long life of the pad compatible. <P>SOLUTION: In the polishing pad provided with a polishing layer on a substrate layer, the polishing layer includes a thermosetting polyurethane foam having approximately spherical open cells and is self-adhered to the substrate layer, and thickness is 0.5-1 mm. <P>COPYRIGHT: (C)2009,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).

  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).

  Moreover, it is laminated | stacked on the back surface side of the surface layer whose thickness is 0.2-2.0 mm, and an elastic compressibility is 50-4%, and this surface layer is 0.2-2 mm, It is laminated | stacked on the back surface side of the intermediate | middle support layer whose elastic compressibility is 2-0.1%, and this intermediate | middle support layer, thickness is 0.15-2.0 mm, and elastic compressibility is 50-4%. A polishing cloth having a back surface layer is proposed (Patent Document 3).

  Further, 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 4).

  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 5).

  Conventional polishing pads 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 6, a finishing polishing cloth having a substantially spherical hole having an average diameter of 1 to 30 μm is manufactured by a wet curing method.

  However, the conventional polishing pad has a problem that the durability is low and the planarization characteristics are gradually deteriorated because the bubbles have an elongated structure or the mechanical strength of the surface layer material itself is low. In addition, the conventional polishing pad has a problem that overpolishing (so-called “edge sagging”) tends to occur at the edge of the object to be polished.

JP 2003-37089 A JP 2003-1000068 A1 JP 2002-307293 A JP 2004-291155 A JP 2004-335713 A JP 2006-75914 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide a polishing pad that is excellent in durability, is less likely to cause edge sagging, and has both a reduced dummy polishing time and a longer pad life.

  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 provides a polishing pad in which a polishing layer is provided on a base material layer, wherein the polishing layer is made of a thermosetting polyurethane foam having substantially spherical open cells and is self-adhering to the base material layer. And a polishing pad having a thickness of 0.5 to 1 mm.

  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 characteristics can be maintained high for a long time. 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.

  The polishing layer needs to be self-adhering to the base material layer. Thereby, it can prevent that a grinding | polishing layer and a base material layer peel during grinding | polishing.

  Further, the polishing layer needs to have a thickness of 0.5 to 1 mm, preferably 0.8 to 1 mm. Thereby, both shortening of the dummy polishing time and extending the life of the pad can be achieved. When the thickness of the polishing layer is less than 0.5 mm, it is not preferable because the life of the pad is shortened and the productivity is lowered. On the other hand, when the thickness of the polishing layer exceeds 1 mm, the object to be polished easily sinks into the polishing layer when pressure is applied, and the edge of the object to be polished is generated. This is not preferable because the dummy polishing until the time until the slurry permeates into the open bubbles becomes long and the polishing speed becomes stable becomes long.

  The thermosetting polyurethane foam preferably has a specific gravity of 0.2 to 0.6 and an Asker C hardness of 20 to 50 degrees. When the specific gravity is less than 0.2, the durability of the polishing layer tends to decrease. On the other hand, when the specific gravity is larger than 0.6, it is necessary to make the material have a low crosslinking density in order to obtain the desired elastic modulus. In that case, permanent set tends to increase and durability tends to deteriorate. Moreover, when Asker C hardness is less than 20 degree | times, it exists in the tendency for durability of a polishing layer to fall or for the surface smoothness of the to-be-polished material after grinding | polishing to worsen. On the other hand, when the Asker C hardness exceeds 50 degrees, scratches are likely to occur on the surface of the object to be polished.

  The thermosetting polyurethane foam contains an isocyanate component and an active hydrogen group-containing compound as raw material components, the isocyanate component is an aromatic isocyanate, and the active hydrogen group-containing compound has a hydroxyl value of 100 to 250 mgKOH / It is preferable to contain 70 to 95% by weight of high molecular weight polyol of g.

  The aromatic isocyanate is preferably carbodiimide-modified MDI.

  The active hydrogen group-containing compound preferably contains a total of 2 to 15% by weight of at least one low molecular weight component selected from the group consisting of low molecular weight polyols, low molecular weight polyamines, and alcohol amines.

  The low molecular weight component is preferably a compound having 3 functional groups having a hydroxyl group and / or an amino group.

  By forming a thermosetting polyurethane foam from these raw materials, a polishing layer having excellent durability can be obtained.

  Furthermore, this invention relates to the manufacturing method of the semiconductor device including the process of grind | polishing the surface of a semiconductor wafer using the said polishing pad.

  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 comprises an isocyanate component, a polyol component (high molecular weight polyol, low molecular weight polyol, alcohol amine, 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, 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.

  Among the high molecular weight polyols, it is preferable to use a high molecular weight polyol having a hydroxyl value of 100 to 250 mgKOH / g. The hydroxyl value is more preferably 100 to 150 mgKOH / g. When the hydroxyl value is less than 100 mgKOH / g, the amount of polyurethane hard segments tends to decrease and the durability tends to decrease. When the hydroxyl value exceeds 250 mgKOH / g, the degree of crosslinking of the polyurethane foam becomes too high. Tend to be brittle.

  The high molecular weight polyol is preferably contained in the active hydrogen group-containing compound in an amount of 70 to 95% by weight, more preferably 80 to 95% 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.

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

  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.

  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 Low molecular weight polyols such as xanol, diethanolamine, N-methyldiethanolamine, and triethanolamine; low molecular weight polyamines such as ethylenediamine, tolylenediamine, diphenylmethanediamine, and diethylenetriamine; monoethanolamine, 2- (2-aminoethylamino) ethanol , And low molecular weight components such as alcohol amines such as monopropanolamine may be used in combination. These low molecular weight components may be used alone or in combination of two or more.

  Among these, it is preferable to use a low molecular weight component having a hydroxyl value or an amine value of 1000 to 2000 mgKOH / g. The hydroxyl value or amine value is more preferably 1000 to 1500 mgKOH / g. When the hydroxyl value or the amine value is less than 1000 mgKOH / g, the effect of improving the formation of open cells tends to be insufficient. On the other hand, when the hydroxyl value or amine value exceeds 2000 mgKOH / g, scratches tend to occur on the wafer surface. In particular, it is preferable to use diethylene glycol, 1,2-propylene glycol, 1,3-butanediol, or 1,4-butanediol.

  Further, it is preferable to use a low molecular weight component having 3 functional groups having a hydroxyl group and / or an amino group. Examples of the low molecular weight component include trimethylolpropane, glycerin, diethanolamine, triethanolamine, and 1,2,6-hexanetriol.

  In order to make the polyurethane foam into an open cell structure, the low molecular weight component is preferably contained in the active hydrogen group-containing compound in a total amount of 2 to 15% by weight, more preferably 2 to 10% by weight. 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.

  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 the silicon surfactant include SH-192, L-5340, B8443 (manufactured by Toray Dow Corning Silicone) and the like as suitable compounds.

  The silicon-based surfactant is preferably added to the polyurethane foam in an amount of 0.1 to 15% by weight, more preferably 2 to 10% 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 silicon-based surfactant was 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 group-containing compound, and the silicon-based surfactant was added. The components are mechanically stirred in the presence of a non-reactive gas, and 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.

  (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 group-containing compound, and the first component and the second component are added. Is mechanically stirred in the presence of a non-reactive gas, and the 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 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.

  In the present invention, it is necessary to uniformly adjust the thickness of the polyurethane foam in the range of 0.5 to 1 mm after forming the polyurethane foam on the base material layer or simultaneously with forming the polyurethane foam. . The method for adjusting the thickness of the polyurethane foam to 0.5 to 1 mm is not particularly limited, and examples thereof include a method of buffing with an abrasive, a method of pressing with a press plate, and a method of slicing with a slicer.

  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 foam-dispersed urethane composition may be cured by adjusting the thickness with a pressing means to form a polyurethane foam.

  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 foam-dispersed urethane composition may be cured by adjusting the thickness with a pressing means to form a polyurethane foam.

  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.

  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.

  The hardness of the polyurethane foam is preferably 20 to 50 degrees, more preferably 30 to 50 degrees, using an Asker C hardness meter.

  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 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 needs to be 0.5 to 1 mm, preferably 0.8 to 1 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 semiconductor device is manufactured through a step of polishing the surface of the 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 method and apparatus for polishing the semiconductor wafer are not particularly limited. For example, as shown in FIG. 1, a polishing surface plate 2 that supports the polishing pad 1, a support table (polishing head) 5 that supports the semiconductor wafer 4, and the wafer. This is performed using a backing material for performing uniform pressurization and a polishing apparatus equipped with a polishing agent 3 supply mechanism. 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.

  Thereby, 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. Further, a glass substrate for a lens or hard disk can be finished and polished by the same method as described above.

  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 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 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 C type hardness meter, pressure surface height: 3 mm), the hardness 60 seconds after contacting the pressure surface was measured.

(Dummy polishing time measurement)
The polishing rate was measured every 10 minutes while polishing the workpiece under the following conditions using the prepared polishing pad, and the time taken to reach the steady value from the initial value was defined as the dummy polishing time.
Polishing machine: BC-15, manufactured by MAT
Pressure: 100 g / cm ²
Head speed: 50 rpm
Surface plate speed: 40 rpm
Slurry: Cerium oxide (Showa Denko, SHOROX F-3) / Water (100 g / L)
Slurry supply amount: 100 mL / min
Workpiece: φ76 0.8t B270 (manufactured by SCHOTT DES AG)
However, the initial polishing rate stability (%) obtained from the following formula from the average polishing rate from the (n-5) th sheet to the nth sheet and the maximum polishing speed and the minimum polishing speed of the five consecutive polishing speeds. ) Was 10% or less, and was determined to be a steady value.
Initial polishing rate stability (%) = {(maximum polishing rate−minimum polishing rate) / average polishing rate} × 100

(Rating evaluation)
Using the New View 6300 manufactured by ZYGO, measure the outer periphery of the workpiece (region of 34.0 mm to 38.0 mm from the center of the workpiece) after dummy polishing is completed under the conditions of a lens magnification of 2.5 and a zoom magnification of 0.5. did. The points 34.0 mm, 35.0 mm, and 37.6 mm from the center of the workpiece are point A, B, and C in order, and the extension line that connects point A and point B intersects the straight line in the thickness direction at point C. The point to be used was D point, and the distance between C point and D point was edge sag (nm). It can be said that the smaller the value, the better the edge sagging.

(Evaluation of pad life)
The pad life was defined as when the polishing rate stability obtained by the following formula exceeded 10%. The average polishing rate was calculated by taking the workpiece when the polishing rate reached a steady value as the first piece, measuring the polishing rate every minute thereafter, and averaging the polishing rates from the first to the tenth piece. . The maximum polishing rate is the maximum value of the polishing rate from the first sheet to the n-th processed sheet, and the minimum polishing rate is the minimum value of the polishing speed from the first sheet to the n-th processed sheet.
Polishing rate stability (%) = {(maximum polishing rate−minimum polishing rate) / average polishing rate} × 100

Example 1
In a container, polycaprolactone diol (Daicel Chemical Industries, Plaxel 210N, hydroxyl value: 110 mgKOH / g, functional group number 2) 80 parts by weight, polycaprolactone triol (Daicel Chemical Industries, Plaxel 305, hydroxyl value: 305 mgKOH / g) , Functional group number 3) 18 parts by weight, trimethylolpropane (hydroxyl value: 1254 mg KOH / g, functional group number 3) 2 parts by weight, silicon surfactant (manufactured by Toray Dow Corning Silicone, B8443) 6 parts by weight, and catalyst ( A second component (25 ° C.) was prepared by adding 0.1 parts by weight of Kao, No. 25) and mixing them. 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, 47.7 parts by weight of carbodiimide-modified MDI (manufactured by Nippon Polyurethane Industry, Millionate MTL, NCO wt%: 29 wt%, 25 ° C.) as the first component was added to the container (NCO / OH = 1.1), about 1 The foam-dispersed urethane composition was prepared by stirring for a minute.

  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 is made 1.5 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: 72 μm, specific gravity: 0.40, C hardness: 39 degrees. ) Was formed. Thereafter, the release sheet under the polyurethane foam was peeled off. Next, the surface of the polyurethane foam is sliced using a band saw type slicer (manufactured by Fecken) to a thickness of 0.6 mm, and the thickness accuracy is adjusted by buffing to obtain a 0.5 mm thick polishing layer. Formed. The polyurethane foam had substantially spherical open cells. 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.

Example 2
A polishing pad was produced in the same manner as in Example 1 except that the surface was sliced to a thickness of 0.9 mm, and the thickness accuracy was adjusted by buffing to form a 0.8 mm thick polishing layer.

Example 3
A polishing pad was prepared in the same manner as in Example 1 except that the surface was sliced to a thickness of 1.1 mm, and the thickness accuracy was adjusted by buffing to form a 1.0 mm thick polishing layer.

Example 4
In a container, polycaprolactone diol (Daicel Chemical Industries, Plaxel 210N, hydroxyl value: 110 mgKOH / g, functional group number 2) 80 parts by weight, polycaprolactone triol (Daicel Chemical Industries, Plaxel 305, hydroxyl value: 305 mgKOH / g) , Functional group number 3) 18 parts by weight, trimethylolpropane (hydroxyl value: 1254 mg KOH / g, functional group number 3) 2 parts by weight, silicon surfactant (manufactured by Toray Dow Corning Silicone, B8443) 10 parts by weight, and catalyst ( A second component (25 ° C.) was prepared by adding 0.1 parts by weight of Kao, No. 25) and mixing them. And it stirred vigorously for about 7 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, 47.7 parts by weight of carbodiimide-modified MDI (manufactured by Nippon Polyurethane Industry, Millionate MTL, NCO wt%: 29 wt%, 25 ° C.) as the first component was added to the container (NCO / OH = 1.1), about 1 The foam-dispersed urethane composition was prepared by stirring for a minute.
Thereafter, a polyurethane foam (open cell structure, average cell diameter: 120 μm, specific gravity: 0.20, C hardness: 35 degrees) and a polishing pad were produced in the same manner as in Example 2.

Example 5
In a container, polycaprolactone diol (Daicel Chemical Industries, Plaxel 210N, hydroxyl value: 110 mgKOH / g, functional group number 2) 80 parts by weight, polycaprolactone triol (Daicel Chemical Industries, Plaxel 305, hydroxyl value: 305 mgKOH / g) , Functional group number 3) 18 parts by weight, trimethylolpropane (hydroxyl value: 1254 mg KOH / g, functional group number 3) 2 parts by weight, silicon surfactant (manufactured by Toray Dow Corning Silicone, B8443), 3 parts by weight, and catalyst ( A second component (25 ° C.) was prepared by adding 0.1 parts by weight of Kao, No. 25) and mixing them. And it stirred vigorously for about 3 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, 47.7 parts by weight of carbodiimide-modified MDI (manufactured by Nippon Polyurethane Industry, Millionate MTL, NCO wt%: 29 wt%, 25 ° C.) as the first component was added to the container (NCO / OH = 1.1), about 1 The foam-dispersed urethane composition was prepared by stirring for a minute.
Thereafter, a polyurethane foam (open cell structure, average cell diameter: 58 μm, specific gravity: 0.60, C hardness: 47 degrees) and a polishing pad were prepared in the same manner as in Example 2.

Example 6
A cell-dispersed urethane composition was prepared in the same manner as in Example 1, except that the amount of Plaxel 210N was changed to 91 parts by weight and the amount of Plaxel 305 was changed to 7 parts by weight. A polishing pad was prepared in the same manner as in Example 3 except that the cell-dispersed urethane composition was used.

Example 7
A cell-dispersed urethane composition was prepared in the same manner as in Example 1 except that the amount of plaquecel 210N was changed to 72 parts by weight and the amount of trimethylolpropane was changed to 10 parts by weight. A polishing pad was prepared in the same manner as in Example 3 except that the cell-dispersed urethane composition was used.

Example 8
A cell-dispersed urethane composition was prepared in the same manner as in Example 1 except that polycaprolactone diol (manufactured by Daicel Chemical Industries, Plaxel 205, hydroxyl value: 208 mgKOH / g, functional group number 2) was used instead of Plaxel 210N. did. A polishing pad was prepared in the same manner as in Example 1 except that the cell-dispersed urethane composition was used.

Comparative Example 1
A polishing pad was prepared in the same manner as in Example 1 except that the surface was sliced to a thickness of 0.5 mm, and the thickness accuracy was adjusted by buffing to form a polishing layer having a thickness of 0.2 mm.

Comparative Example 2
Use a nip roll to make the cell-dispersed urethane layer 2.0 mm thick, slice the surface of the polyurethane foam to 1.6 mm, and adjust the thickness accuracy by buffing to polish 1.5 mm thick A polishing pad was produced in the same manner as in Example 1 except that the layer was formed.

Comparative Example 3
A urethane solution was prepared by dissolving 10 parts by weight of thermoplastic urethane (Rezamin 7285, manufactured by Dainichi Seika) in 90 parts by weight of dimethylformamide. The urethane solution was applied onto a base material layer (Toyobo Co., Ltd., Borance 4211N, Asker C hardness 22) whose thickness was adjusted to 0.8 mm by buffing to form a urethane film. Thereafter, the urethane membrane-base material layer was immersed in a DMF-water mixture (DMF / water = 30/70) for 30 minutes, and further immersed in water for 24 hours to replace dimethylformamide with water, thereby forming a polyurethane foam (specific gravity). : 0.26, C hardness: 27 degrees). Next, the surface of the polyurethane foam was buffed using a buffing machine to a thickness of 0.2 mm, and the thickness accuracy was adjusted to form a polishing layer. The polyurethane foam had elongated cocoon-shaped cells. 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.

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 (7)

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, is self-adhering to the base material layer, and has a thickness. A polishing pad having a thickness of 0.5 to 1 mm. The polishing pad according to claim 1, wherein the thermosetting polyurethane foam has a specific gravity of 0.2 to 0.6 and an Asker C hardness of 20 to 50 degrees. The thermosetting polyurethane foam contains an isocyanate component and an active hydrogen group-containing compound as raw material components, the isocyanate component is an aromatic isocyanate, and the active hydrogen group-containing compound has a hydroxyl value of 100 to 250 mgKOH / The polishing pad according to claim 1 or 2, comprising 70 to 95% by weight of g of a high molecular weight polyol. The polishing pad according to claim 3, wherein the aromatic isocyanate is carbodiimide-modified MDI. The polishing according to claim 3 or 4, wherein the active hydrogen group-containing compound contains a total of 2 to 15% by weight of at least one low molecular weight component selected from the group consisting of a low molecular weight polyol, a low molecular weight polyamine, and an alcohol amine. pad. The polishing pad according to claim 5, wherein the low molecular weight component is a compound having 3 functional groups having a hydroxyl group and / or an amino group. A method for manufacturing a semiconductor device, comprising a step of polishing a surface of a semiconductor wafer using the polishing pad according to claim 1.

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