JP4237800B2 - Polishing pad - Google Patents

Description

  The present invention stabilizes flattening processing of optical materials such as lenses and reflecting mirrors, silicon wafers, glass substrates for hard disks, aluminum substrates, and materials that require high surface flatness such as general metal polishing processing, In addition, the present invention relates to a polishing pad that can be performed with high polishing efficiency. The polishing pad of the present invention is particularly useful for finish polishing of a silicon wafer or glass.

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

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

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

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

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

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

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

  However, the conventional polishing pad has a long and narrow structure of the bubbles or the mechanical strength of the material of the surface layer itself is low, so that the durability is poor, the planarization characteristics are gradually deteriorated, and the stability of the polishing rate is inferior. There was a problem. Further, the conventional polishing pad has a problem that the adhesiveness between the polishing layer and the base material layer is weak, and it is easily peeled off at the interface. Further, the conventional polishing pad has a problem that the self-dressing property is poor and the pad surface is easily clogged during polishing.

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

  An object of the present invention is to provide a polishing pad having excellent durability, good self-dressing properties, and good adhesion between a polishing layer and a base material layer.

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

  That is, the present invention is a polishing pad provided with a polishing layer on a base material layer, the polishing layer is composed of a thermosetting polyurethane foam having substantially spherical open cells having an average cell diameter of 20 to 300 μm, The polyurethane foam contains an isocyanate component and an active hydrogen-containing compound as raw material components, and the active hydrogen-containing compound has a low molecular weight polyol having 3 to 8 functional groups and a hydroxyl value of 400 to 1830 mg KOH / g and / or The present invention relates to a polishing pad comprising 1 to 20% by weight of a low molecular weight polyamine having 3 to 8 functional groups and an amine value of 400 to 1870 mg KOH / g.

  In conventional polishing pads, because bubbles have an elongated structure or because the mechanical strength of the material of the polishing layer itself is low, it is considered that when repeated pressure is applied to the polishing layer, “sagging” occurs, resulting in poor durability. It is done. 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 having an average cell diameter of 20 to 300 μm. 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. Moreover, since it has an open cell structure, it has excellent slurry retention. 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.

  When the average bubble diameter deviates from the range of 20 to 300 μm, the polishing rate decreases or the durability decreases.

  Further, the active hydrogen-containing compound which is a material for forming the thermosetting polyurethane foam is a low molecular weight polyol having 3 to 8 functional groups and a hydroxyl value of 400 to 1830 mgKOH / g and / or 3 to 8 functional groups and an amine value. Contains 1 to 20% by weight of low molecular weight polyamine of 400 to 1870 mg KOH / g. By using a specific amount of the low molecular weight polyol and / or low molecular weight polyamine, the bubble film is easily broken and not only is easy to form open cells but also the stability of the polishing rate is improved. In addition, the use of polyfunctional low molecular weight polyols and low molecular weight polyamines results in the formation of polyurethane with a well-developed crosslinked structure, which improves self-dressing performance and prevents clogging of the pad surface during polishing. Become.

  When the number of functional groups is less than 3, the cross-linked structure of polyurethane is not sufficiently developed, so that the self-dressing performance is insufficient, and when the number of functional groups exceeds 8, the cross-linked structure of polyurethane is excessively developed. It becomes too brittle and adversely affects the polishing characteristics.

  When the hydroxyl value is less than 400 mgKOH / g or the amine value is less than 400 mgKOH / g, the effect of improving open cell formation cannot be obtained sufficiently. On the other hand, when the hydroxyl value exceeds 1830 mgKOH / g or the amine value exceeds 1870 mgKOH / g, the polyurethane foam becomes too hard and scratches are likely to occur on the wafer surface.

  In addition, when using the said low molecular weight polyol and low molecular weight polyamine together, 1 to 20 weight% is used in total.

  The low molecular weight polyol is selected from the group consisting of trimethylolpropane, glycerin, diglycerin, 1,2,6-hexanetriol, triethanolamine, pentaerythritol, tetramethylolcyclohexane, methylglucoside, and alkylene oxide adducts thereof. The low molecular weight polyamine is preferably at least one selected from the group consisting of ethylenediamine, tolylenediamine, diphenylmethanediamine, and these alkylene oxide adducts.

  The active hydrogen-containing compound preferably contains 30 to 85% by weight of a high molecular weight polyol having 2 to 4 functional groups and a hydroxyl value of 20 to 150 mgKOH / g. By using a specific amount of the polymer polyol, the desired open cell can be stably formed, and the mechanical properties of the polishing layer are improved.

  Moreover, in this invention, it is preferable that the isocyanate component which is a forming material of a thermosetting polyurethane foam is carbodiimide modified MDI. By using the low molecular weight polyol and / or the low molecular weight polyamine in combination with the carbodiimide-modified MDI, the adhesion between the polishing layer and the base material layer is remarkably improved.

  Further, the present invention is a carbodiimide-modified MDI, a low molecular weight polyol having 3 to 8 functional groups and a hydroxyl value of 400 to 1830 mgKOH / g and / or a low molecular weight number of 3 to 8 and an amine value of 400 to 1870 mgKOH / g. A step of preparing a cell-dispersed urethane composition containing an active hydrogen-containing compound containing 1 to 20% by weight of a molecular weight polyamine as a raw material component by a mechanical foaming method, a step of applying a cell-dispersed urethane composition on a substrate layer, By curing the dispersed urethane composition, the step of forming a thermosetting polyurethane foam layer having substantially spherical open cells with an average cell diameter of 20 to 300 μm, and the thickness of the thermosetting polyurethane foam layer are uniformly adjusted. The present invention relates to a method for manufacturing a polishing pad including steps.

  Further, the present invention is a carbodiimide-modified MDI, a low molecular weight polyol having 3 to 8 functional groups and a hydroxyl value of 400 to 1830 mgKOH / g and / or a low molecular weight number of 3 to 8 and an amine value of 400 to 1870 mgKOH / g. A step of preparing a cell-dispersed urethane composition containing an active hydrogen-containing compound containing 1 to 20% by weight of a molecular weight polyamine as a raw material component by a mechanical foaming method, a step of applying a cell-dispersed urethane composition on a release sheet, and a cell A step of laminating a base material layer on a dispersed urethane composition, a thermoset having substantially spherical open cells having an average cell diameter of 20 to 300 μm by curing the cell dispersed urethane composition while making the thickness uniform by pressing means. A step of forming a porous polyurethane foam layer and a step of peeling a release sheet under the thermosetting polyurethane foam layer. A method of manufacturing a polishing pad, on.

  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 having an average cell diameter of 20 to 300 μm, 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, chain extender, 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.

  Of the above isocyanate components, aromatic diisocyanates are preferably used, and carbodiimide-modified MDI is particularly 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 2 to 4 functional groups and a hydroxyl value of 20 to 150 mgKOH / g. The hydroxyl value is more preferably 50 to 120 mgKOH / g. When the hydroxyl value is less than 20 mgKOH / g, the amount of polyurethane hard segments tends to decrease and the durability tends to decrease. When the hydroxyl value exceeds 150 mgKOH / g, the degree of crosslinking of the polyurethane foam becomes too high. Tend to be brittle. The high molecular weight polyol is preferably used in an amount of 30 to 85% by weight, more preferably 30 to 60% by weight, based on the entire active hydrogen-containing compound.

  In the present invention, a low molecular weight polyol having 3 to 8 functional groups and a hydroxyl value of 400 to 1830 mg KOH / g and / or a low molecular weight having 3 to 8 functional groups and an amine value of 400 to 1870 mg KOH / g together with a high molecular weight polyol. It is necessary to use the polyamine in an amount of 1 to 20% by weight based on the entire active hydrogen-containing compound. The addition amount of the low molecular weight polyol and / or the low molecular weight polyamine is preferably 5 to 15% by weight.

  Examples of the low molecular weight polyol having the number of functional groups and the hydroxyl value include, for example, trimethylolpropane, glycerin, diglycerin, 1,2,6-hexanetriol, triethanolamine, pentaerythritol, tetramethylolcyclohexane, methylglucoside, and these And adducts of alkylene oxide (EO, PO, etc.). These may be used alone or in combination of two or more. In particular, trimethylolpropane is preferably used.

  Examples of the low molecular weight polyamine having the number of functional groups and an amine value include ethylenediamine, tolylenediamine, diphenylmethanediamine, and alkylene oxide (EO, PO, etc.) adducts thereof. These may be used alone or in combination of two or more. It is particularly preferable to use an EO adduct of ethylenediamine.

  Further, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,6 -Low molecular weight polyols such as hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol, diethylene glycol and triethylene glycol may be used in combination. Further, alcohol amines such as monoethanolamine, diethanolamine, 2- (2-aminoethylamino) ethanol, and monopropanolamine may be used in combination.

  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 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 0.90 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.

  The thermosetting polyurethane foam, which is a material for forming the polishing layer, is produced by a mechanical foaming method (including a mechanical floss method).

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

  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 thermosetting 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 an active hydrogen-containing compound such as a low molecular weight polyol or a low molecular weight polyamine is added to the cell dispersion and mixed to prepare a cell dispersed urethane composition. A catalyst may be appropriately added to the second component.

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

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

  The cell dispersed urethane composition may be prepared by a mechanical floss method. The mechanical floss method is a method in which raw material components are put into a mixing chamber of a mixing head and a non-reactive gas is mixed and mixed and stirred by a mixer such as an Oaks mixer to make the non-reactive gas into a fine bubble state in the raw material mixture. It is a method of dispersing in. The mechanical floss method is a preferable method because the density of the polyurethane foam can be easily adjusted by adjusting the amount of the non-reactive gas mixed therein. Moreover, since the polyurethane foam which has a substantially spherical fine cell with an average cell diameter of 20-300 micrometers can be continuously shape | molded, manufacturing efficiency is good.

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

  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 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.

  The base material layer is not particularly limited. For example, plastic films such as nylon, polypropylene, polyethylene, polyester, 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 nylon, polypropylene, polyethylene, polyester, 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 40 to 70 ° C. for 10 minutes to 24 hours, and it is preferable to perform at normal pressure because the bubble shape is 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 manufacturing method of the polishing pad of the present invention, it is necessary to uniformly adjust the thickness of the polyurethane foam after forming the polyurethane foam on the base material layer or simultaneously with forming the polyurethane foam. . 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. When buffing, a polishing layer having no skin layer on the surface of the polyurethane foam is obtained, and when pressed, a polishing layer having a skin layer on the surface of the polyurethane foam is obtained. The conditions for pressing are not particularly limited, but it is preferable to adjust the temperature above the glass transition point.

  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. This method is particularly preferable because the thickness of the polishing layer can be controlled very uniformly.

  The material for forming the release sheet is not particularly limited, and examples thereof include the same resin and paper as the base material layer. 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 release sheet, the cell-dispersed urethane composition (cell-dispersed urethane layer), and the base material layer 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 foamed layer become about 1.2 to 2 times larger after compression, the (coater or nip clearance)-(base layer and release sheet thickness) = (after curing) The thickness of the polyurethane foam is preferably 50 to 85%. Moreover, in order to obtain a polyurethane foam having a specific gravity of 0.2 to 0.5, the specific gravity of the cell-dispersed urethane composition before passing through the roll is preferably 0.24 to 1.

  Then, after the thickness of the sandwich sheet is made uniform, the reacted polyurethane foam is heated and post-cured until it no longer flows. Post cure conditions are the same as described above.

  Thereafter, the release sheet under the polyurethane foam is peeled off. In this case, a skin layer is formed on the polyurethane foam. 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. Thus, since the lower surface side of the formed polyurethane foam is used as the polishing surface, the polishing surface has a small variation in bubbles, and thus the stability of the polishing rate is further improved. The skin layer may be removed by buffing the polyurethane foam after peeling off the release sheet.

  The thickness of the polyurethane foam is not particularly limited, but is preferably 0.2 to 3 mm, and more preferably 0.5 to 2 mm.

  The polyurethane foam has substantially spherical open cells in which circular holes are formed on the cell surface. The open bubbles are not formed by crushing.

  The average cell diameter of open cells in the polyurethane foam is 20 to 300 μm, preferably 50 to 100 μm. The average diameter of the circular holes on the bubble surface is preferably 100 μm or less, more preferably 50 μm or less.

  The specific gravity of the polyurethane foam is preferably 0.2 to 0.6, more preferably 0.3 to 0.5. When the specific gravity is less than 0.2, the bubble rate becomes too high and the durability tends to deteriorate. On the other hand, when the specific gravity exceeds 0.6, the material needs to have a low cross-linking density in order to obtain a certain elastic modulus. In that case, permanent set increases and durability tends to deteriorate.

  The hardness of the polyurethane foam is preferably 10 to 80 degrees in terms of Asker C hardness, and more preferably 20 to 70 degrees. When the Asker C hardness is less than 10 degrees, the durability tends to decrease or the flatness of the polished material after polishing tends to deteriorate. On the other hand, if it exceeds 80 degrees, scratches are likely to occur on the surface of the material to be polished.

  The shape of the polishing pad of the present invention is not particularly limited, and may be a long shape having a length of about 5 to 10 m or a round shape having a diameter of about 50 to 150 cm.

  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 slurry. For example, an X (striped) groove, an XY lattice groove, a concentric groove, a through hole, a hole that does not pass through, a polygonal column, Examples include a cylinder, a spiral groove, an eccentric circular groove, a radial groove, and a combination 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 polishing pad of the present invention may be one in which a cushion sheet is bonded to one side of the base material layer.

  The cushion sheet (cushion layer) supplements the characteristics of the polishing layer. The cushion sheet is necessary for achieving both planarity and uniformity in a trade-off relationship in CMP. Planarity refers to the flatness of a pattern portion when a material having fine irregularities generated during pattern formation is polished, and uniformity refers to the uniformity of the entire material to be polished. The planarity is improved by the characteristics of the polishing layer, and the uniformity is improved by the characteristics of the cushion sheet. In the polishing pad of the present invention, it is preferable to use a cushion sheet that is softer than the polishing layer.

  Examples of the cushion sheet include a fiber nonwoven fabric such as a polyester nonwoven fabric, a nylon nonwoven fabric, and an acrylic nonwoven fabric, a resin-impregnated nonwoven fabric such as a polyester nonwoven fabric impregnated with polyurethane, a polymer resin foam such as polyurethane foam and polyethylene foam, a butadiene rubber, Examples thereof include rubber resins such as isoprene rubber and photosensitive resins.

  Examples of means for attaching the cushion sheet include a method in which the base material layer and the cushion sheet are sandwiched and pressed with a double-sided tape.

  Moreover, the polishing pad of this invention may be provided with the double-sided tape in the surface adhere | attached with a 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. 3, 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 slide glass and observed at 200 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 open cell ratio)
The open cell ratio was measured according to the ASTM-2856-94-C method. However, 10 samples of polyurethane foam punched in a circle were used as measurement samples. The measuring instrument used was an air comparison type hydrometer 930 type (manufactured by Beckman Co., Ltd.). The open cell ratio was calculated by the following formula.
Open cell ratio (%) = [(V−V1) / V] × 100
V: Apparent volume calculated from sample size (cm ³ )
V1: Sample volume (cm ³ ) measured using an air-comparing hydrometer

(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 30 seconds after contacting the pressure surface was measured.

(Measurement of adhesive strength)
The prepared polishing pad was cut into a size of 25 mm in width and 130 mm in length, and the polyurethane foam layer was peeled off from the base material layer leaving an end length of 50 mm. Thereafter, the polyurethane foam layer was peeled from the base material layer at a peeling angle of 180 ° and a peeling speed of 50 mm / min, the maximum stress (N) measured at that time was measured, and the value was determined as the adhesive strength (N). It was.

(Dressing speed measurement)
The surface of the prepared polishing layer was uniformly dressed while being rotated using a diamond dresser (manufactured by Asahi Diamond Co., Ltd., M type # 100, 20 cmφ circle). The dresser load at this time was 100 g / cm ² , the polishing platen rotation speed was 30 rpm, the dresser rotation speed was 15 rpm, and the dressing time was 30 min. Then, the dressing speed was calculated from the thickness of the polishing layer before and after the dressing.

(Evaluation of polishing rate stability)
Using SPP600S (manufactured by Okamoto Machine Tool Co., Ltd.) as a polishing apparatus, the polishing rate stability of the manufactured polishing pad was evaluated. The evaluation results are shown in Table 2. 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: 500 First, the polishing rate (Å / min) for each polished glass plate is calculated. The calculation method is as follows.
Polishing rate = [weight change amount of glass plate before and after polishing [g] / (glass plate density [g / cm ³ ] × polishing area of glass plate [cm ² ] × polishing time [min])] × 10 ⁸
The polishing rate stability (%) is the maximum polishing rate, the minimum polishing rate, and the total average polishing rate from the first glass plate to the number of processed sheets (100, 300, or 500 sheets). Is calculated by substituting that value into the following equation. As the polishing rate stability (%) is lower, the polishing rate is less likely to change even when a large number of glass plates are polished. In the present invention, the polishing rate stability after processing 500 sheets is preferably within 10%. Table 2 shows the average polishing rate after processing 500 sheets.
Polishing rate stability (%) = {(maximum polishing rate−minimum polishing rate) / total average polishing rate} × 100

Example 1
In a container, polytetramethylene ether glycol (Mitsubishi Chemical Corporation, PTMG1000, functional group number: 2, hydroxyl value: 110 mg KOH / g) 85 parts by weight, polycaprolactone polyol (manufactured by Daicel Chemical Industries, Plaxel 205, functional group number: 2, Hydroxyl value: 208 mg KOH / g) 5 parts by weight, polycaprolactone polyol (manufactured by Daicel Chemical Industries, Plaxel 305, functional group number: 3, hydroxyl value: 305 mg KOH / g), 5 parts by weight, trimethylolpropane (functional group number: 3, Hydroxyl value: 1245 mgKOH / g) 5 parts by weight, silicon-based surfactant (manufactured by Goldschmidt, B8443) 6 parts by weight, and catalyst (manufactured by Kao, Kao No. 25) 0.3 part by weight were mixed. And it stirred vigorously for about 4 minutes so that a bubble might be taken in in a reaction system with the rotation speed of 900 rpm using the stirring blade. Then, 33 parts by weight of carbodiimide-modified MDI (manufactured by Nippon Polyurethane Industry, Millionate MTL) 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 sheet composed of a release-treated PET sheet (Toyobo Co., Ltd., thickness: 75 μm) to form a cell-dispersed urethane layer. And the base material layer which consists of PET sheet | seat (Toyobo Co., Ltd. thickness 188 micrometers) was covered on this cell dispersion | distribution urethane layer. The cell-dispersed urethane layer was made 1.5 mm thick with a nip roll, subjected to primary curing at 40 ° C. for 30 minutes, and then secondary cured at 70 ° C. for 30 minutes to form a polyurethane foam (foamed layer). Thereafter, the release sheet was peeled off. Next, the thickness of the polyurethane foam was adjusted to 1.3 mm using a slicer (manufactured by Fecken) to adjust the thickness accuracy. Thereafter, a double-sided tape (double tack tape, manufactured by Sekisui Chemical Co., Ltd.) was bonded to the surface of the base material layer using a laminator to prepare a polishing pad.

Examples 2 to 6 and Comparative Example 1
A polishing pad was produced in the same manner as in Example 1 with the blending ratio shown in Table 1.

表２から、本発明の研磨パッドは、研磨速度安定性に優れ、セルフドレス性がよく、かつ研磨層と基材層との接着性が良好であることがわかる。 Comparative Example 2
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 layer is 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 to form a polyurethane foam. did. Next, the thickness of the polyurethane foam was adjusted to 1.3 mm using a slicer (manufactured by Fecken) to adjust the thickness accuracy. Thereafter, a double-sided tape (double tack tape, manufactured by Sekisui Chemical Co., Ltd.) was bonded to the surface of the base material layer using a laminator to prepare a polishing pad.

From Table 2, it can be seen that the polishing pad of the present invention has excellent polishing rate stability, good self-dressing properties, and good adhesion between the polishing layer and the base material layer.

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: Material to be polished (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 composed of a thermosetting polyurethane foam having substantially spherical open cells having an average cell diameter of 20 to 300 μm, and the polyurethane foam is An isocyanate component and an active hydrogen-containing compound are contained as raw material components, and the active hydrogen-containing compound has a low molecular weight polyol having 3 to 8 functional groups and a hydroxyl value of 400 to 1830 mg KOH / g and / or 3 to 8 functional groups. A polishing pad comprising 1 to 20% by weight of a low molecular weight polyamine having an amine value of 400 to 1870 mg KOH / g. The low molecular weight polyol is selected from the group consisting of trimethylolpropane, glycerin, diglycerin, 1,2,6-hexanetriol, triethanolamine, pentaerythritol, tetramethylolcyclohexane, methylglucoside, and alkylene oxide adducts thereof. The polishing pad according to claim 1, wherein the low molecular weight polyamine is at least one selected from the group consisting of ethylenediamine, tolylenediamine, diphenylmethanediamine, and alkylene oxide adducts thereof. The polishing pad according to claim 1 or 2, wherein the active hydrogen-containing compound contains 30 to 85% by weight of a high molecular weight polyol having 2 to 4 functional groups and a hydroxyl value of 20 to 150 mgKOH / g. The polishing pad according to claim 1, wherein the isocyanate component is carbodiimide-modified MDI. 1 to 20 carbodiimide-modified MDI and low molecular weight polyol having 3 to 8 functional groups and a hydroxyl value of 400 to 1830 mgKOH / g and / or low molecular weight polyamine having 3 to 8 functional groups and an amine value of 400 to 1870 mgKOH / g A step of preparing a cell-dispersed urethane composition containing, by weight, an active hydrogen-containing compound as a raw material component by a mechanical foaming method, a step of applying a cell-dispersed urethane composition on a base material layer, and curing a cell-dispersed urethane composition A polishing pad comprising a step of forming a thermosetting polyurethane foam layer having substantially spherical open cells having an average cell diameter of 20 to 300 μm, and a step of uniformly adjusting the thickness of the thermosetting polyurethane foam layer. Production method. 1 to 20 carbodiimide-modified MDI and low molecular weight polyol having 3 to 8 functional groups and a hydroxyl value of 400 to 1830 mgKOH / g and / or low molecular weight polyamine having 3 to 8 functional groups and an amine value of 400 to 1870 mgKOH / g A step of preparing a cell-dispersed urethane composition containing, as a raw material component, an active hydrogen-containing compound containing 5% by weight by a mechanical foaming method, a step of applying a cell-dispersed urethane composition on a release sheet, and a cell-dispersed urethane composition The step of laminating the base material layer, and curing the cell-dispersed urethane composition with a uniform thickness by pressing means, thereby forming a thermosetting polyurethane foam layer having substantially spherical open cells with an average cell diameter of 20 to 300 μm And a polishing pad comprising a step of peeling the release sheet under the thermosetting polyurethane foam layer Method. 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.

Images