JP4970963B2 - Polishing pad manufacturing method - 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.

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

  An object of this invention is to provide the polishing pad excellent in durability.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the above object can be achieved by the production method shown below, and have completed the present invention.

That is, the present invention is, bubbles distributed over bubbles preparing a dispersed urethane composition, the nitrogen gas permeation rate is 1 × ^{10 -7 [cm 3 / cm 2 · s ·} cmHg Hereinafter sheet A by a mechanical foaming method The step of applying the urethane composition, the step of laminating the sheet B having a nitrogen gas permeation rate of 1 × 10 ⁻⁷ [cm ³ / cm ² · s · cmHg] or less on the applied cell-dispersed urethane composition, pressing The present invention relates to a method for producing a polishing pad comprising a step of forming a thermosetting polyurethane foam layer having open cells by curing a cell-dispersed urethane composition with a uniform thickness by means.

  As described above, a gas such as air is dispersed as fine bubbles in a raw material by a mechanical foaming method to prepare a cell-dispersed urethane composition, and the cell diameter is extremely small by curing the cell-dispersed urethane composition, and A polyurethane foam layer (polishing layer) having spherical (including elliptical) open cells can be easily formed. Further, in the mechanical foaming method of the present invention, gas such as air is dispersed without being dissolved in the raw material, so that new bubbles are generated after the step of uniformly adjusting the thickness of the thermosetting polyurethane foam layer. (Post-foaming phenomenon) can be suppressed, and the thickness accuracy and specific gravity are easily controlled. Moreover, since it is not necessary to use a solvent, it is not only excellent in cost but also preferable from the environmental viewpoint.

In the production method of the present invention, by laminating sheets A and B having a nitrogen gas permeation rate of 1 × 10 ⁻⁷ [cm ³ / cm ² · s · cmHg] or less, When the fine bubbles are broken to form continuous bubbles, the gas inside the fine bubbles can be held in the composition, and can be prevented from being discharged to the external environment. Thereby, it can suppress that the thickness of a cell dispersion | distribution urethane composition changes at the time of a hardening process, and can raise the surface precision of the polyurethane foam layer after hardening.

  In the production method of the present invention, the curing step includes at least a primary cure and a secondary cure, and the primary cure has a cure temperature of 30 to 50 ° C. and a cure time of 5 to 60 minutes, and the secondary cure has a cure temperature of 60 It is preferable that it is -80 degreeC and the curing time is 30 minutes or more. In this way, by performing the curing in multiple stages, it is possible to form fine and highly uniform open cells. When curing is performed in one stage, the bubble diameter tends to increase, and the durability of the polishing pad tends to decrease. On the other hand, if it is outside the range of the above curing conditions, fine and highly uniform open cells cannot be formed, and the stability of the polishing rate tends to deteriorate.

  In the present invention, the sheets A and B are preferably polyethylene terephthalate sheets. PET is a suitable material because of its particularly low nitrogen gas transmission rate.

  The polishing pad of this invention is obtained by the said manufacturing method. Since the polishing layer of the polishing pad of the present invention has spherical fine bubbles, it has excellent durability. Therefore, when the material to be polished is polished using the polishing pad of the present invention, the stability of the polishing rate is improved.

  The present invention also relates to a method for manufacturing a semiconductor device including a step of polishing a surface of a semiconductor wafer using the polishing pad.

The method for producing a polishing pad according to the present invention includes a step of preparing a cell-dispersed urethane composition by a mechanical foaming method, a sheet A having a nitrogen gas permeation rate of 1 × 10 ⁻⁷ [cm ³ / cm ² · s · cmHg] or less. The step of applying the cell-dispersed urethane composition on top, and laminating the sheet B having a nitrogen gas permeation rate of 1 × 10 ⁻⁷ [cm ³ / cm ² · s · cmHg] or less on the applied cell-dispersed urethane composition A step of forming a thermosetting polyurethane foam layer (hereinafter referred to as a polyurethane foam layer) having open cells by curing the cell-dispersed urethane composition while making the thickness uniform by pressing means.

  The cell-dispersed urethane composition may be prepared by a mechanical foaming method (including a mechanical floss method), and the others are not particularly limited. For example, the cell-dispersed urethane composition is prepared by the following method.

  (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 high molecular weight polyol or a low molecular weight polyol is added to the cell dispersion and mixed to prepare a cell dispersed urethane composition. A filler such as a catalyst and carbon black may be appropriately added to the second component.

  (2) A component in which a silicon-based 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-based 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.

  Thermosetting polyurethane is preferable as a material for forming a polishing layer of a polishing pad because spherical open cells can be easily formed by a mechanical foaming method.

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

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

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

  Examples of the active hydrogen-containing compound include a high molecular weight polyol having an active hydrogen that reacts with an isocyanate component, a low molecular weight polyol, and a low molecular weight polyamine.

  Examples of the high molecular weight polyol include those usually used in the technical field of thermosetting 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 100 mgKOH / g. The hydroxyl value is more preferably 25 to 60 mgKOH / g. By using the polymer polyol, the desired open cell can be stably formed, and the mechanical properties of the polishing layer are improved. When the number of functional groups is 5 or more, the cross-linking degree of the thermosetting polyurethane foam becomes too high and becomes too brittle, or scratches are likely to occur on the surface of the material to be polished. When the hydroxyl value is less than 20 mgKOH / g, the amount of polyurethane hard segments decreases and the durability decreases. When it exceeds 100 mgKOH / g, the degree of crosslinking of the thermosetting polyurethane foam becomes too high. , It becomes too brittle or scratches are likely to occur on the surface of the material to be polished.

  Moreover, it is also preferable to use a polymer polyol, and it is particularly preferable to use a polymer polyol in which polymer particles made of acrylonitrile and / or a styrene-acrylonitrile copolymer are dispersed. The polymer polyol is preferably contained in the total high molecular weight polyol to be used in an amount of 20 to 100% by weight, more preferably 30 to 60% by weight.

  These specific high molecular weight polyols are preferably contained in the active hydrogen-containing compound in an amount of 60 to 85% by weight, more preferably 70 to 80% by weight. By using a specific amount of the specific high molecular weight polyol, the cell membrane is easily broken, and the intended open cell is easily formed.

  Along with the 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, Trimethylolpropane, glycerin, 1,2,6-hexanetriol, pentaerythritol, tetramethylolcyclohexane, methylglucoside, sorbitol, mannitol, dulcitol, sucrose, 2,2,6,6-tetrakis (hydroxymethyl) Rohekisanoru, diethanolamine, N- methyldiethanolamine, and low molecular weight polyols such as triethanolamine may be used in combination. Moreover, low molecular weight polyamines, such as ethylenediamine, tolylenediamine, diphenylmethanediamine, and diethylenetriamine, can also be used in combination. Moreover, you may use together the polyol which added alkylene oxides, such as ethylene oxide and a propylene oxide, to the said low molecular weight polyol or low molecular weight polyamine. Also, alcohol amines such as monoethanolamine, 2- (2-aminoethylamino) ethanol, and monopropanolamine can be used in combination. These low molecular weight polyols and low molecular weight polyamines may be used alone or in combination of two or more.

  Among these, it is preferable to use a low molecular weight polyol having a hydroxyl value of 400 to 1830 mgKOH / g and / or a low molecular weight polyamine having an amine value of 400 to 1870 mgKOH / g. The hydroxyl value is more preferably 700 to 1250 mgKOH / g, and the amine value is more preferably 400 to 950 mgKOH / g. When the hydroxyl value is less than 400 mgKOH / g or the amine value is less than 400 mgKOH / g, the effect of improving the formation of open cells tends to be insufficient. On the other hand, when the hydroxyl value exceeds 1830 mgKOH / g or the amine value exceeds 1870 mgKOH / g, the thermosetting polyurethane foam becomes too hard and scratches are likely to occur on the surface of the material to be polished. In particular, it is preferable to use diethylene glycol, triethylene glycol, or 1,4-butanediol.

  Moreover, it is preferable to make these low molecular weight polyol and / or low molecular weight polyamine contain 2 to 15 weight% in an active hydrogen containing compound, More preferably, it is 5 to 10 weight%. By using a specific amount of the low molecular weight polyol and / or the low molecular weight polyamine, the cell membrane is easily broken and not only the target open cell is easily formed, but also the mechanical properties of the polyurethane foam layer are improved.

上記式において、ｎはポリオール成分の数、ａｉは水酸基価、ｂｉは官能基数、ｃｉは添加重量部である。
例えば、使用する活性水素含有化合物が第１〜第ｎポリオール成分まである場合、第１ポリオール成分の水酸基価をａ１、官能基数をｂ１、及び添加重量部をｃ１とし、・・・、第ｎポリオール成分の水酸基価をａｎ、官能基数をｂｎ、及び添加重量部をｃｎとする。ただし、ポリマーポリオールについてはポリマー粒子が分散しているため、どの種類においても官能基数は３として計算する。 Moreover, it is preferable that the average hydroxyl value (OHVav) of the active hydrogen containing compound to be used exists in the range of a following formula.
(350-80 × fav−120 / fav) ≦ OHVav ≦ (350-80 × fav + 120 / fav)
In the above formula, OHVav and fav (average functional group number) are calculated by the following formula.

In the above formula, n is the number of polyol components, ai is the hydroxyl value, bi is the number of functional groups, and ci is the weight part added.
For example, when the active hydrogen-containing compound to be used is from the first to the n-th polyol component, the hydroxyl value of the first polyol component is a1, the number of functional groups is b1, and the addition part by weight is c1,. The hydroxyl value of the component is an, the number of functional groups is bn, and the added weight part is cn. However, since polymer particles are dispersed with respect to the polymer polyol, the number of functional groups is calculated as 3 in any kind.

  In the case of producing polyurethane by the prepolymer method, the type and blending ratio of the active hydrogen-containing compound used at the time of synthesizing and curing the isocyanate-terminated prepolymer are not particularly limited. It is preferable to use 80% by weight or more of high molecular weight polyol and 80% by weight or more of low molecular weight polyol and / or low molecular weight polyamine in the active hydrogen-containing compound when the isocyanate-terminated prepolymer is cured. Use of such active hydrogen-containing compounds is a preferable method from the viewpoint of the stability and productivity of the physical properties of the resulting polyurethane.

  The ratio of the isocyanate component, the high molecular weight polyol, the low molecular weight polyol, and the low molecular weight polyamine can be variously changed depending on the respective molecular weight, desired physical properties of the polyurethane foam layer, and the like. In order to obtain a polishing layer 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) is preferably 0.80 to 1.20, more preferably 0.8. 99 to 1.15. When the number of isocyanate groups is out of the above range, curing failure occurs and the required open cells, specific gravity, hardness and the like tend not to be obtained.

  As the isocyanate-terminated prepolymer, those having a molecular weight of about 1000 to 10,000 are preferable because they have excellent processability and physical characteristics. Further, when the prepolymer is solid at normal temperature, it is preheated to an appropriate temperature and melted before use.

  Examples of the silicon-based surfactant include those containing a copolymer of polyalkylsiloxane and polyether. Examples of suitable silicon surfactants include SH-192 and L5340 (manufactured by Toray Dow Corning Silicone).

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

  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, etc. 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 stirring for preparing the cell dispersion in the foaming step and 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.

Then, the cell-dispersed urethane composition prepared by the above method is applied onto the sheet A having a nitrogen gas transmission rate of 1 × 10 ⁻⁷ [cm ³ / cm ² · s · cmHg] or less. The nitrogen gas permeation rate of the sheet A is preferably 1 × 10 ⁻⁸ [cm ³ / cm ² · s · cmHg] or less.

  Examples of the material for forming the sheet A include polyethylene terephthalate, polypropylene, and polyethylene. The sheet A may be a double-sided tape having adhesive layers on both sides of a base material sheet made of the above material.

  The thickness of the sheet A (base sheet in the case of double-sided tape) is not particularly limited, but is 0.025 to 25% from the viewpoint of suppressing the permeability of gas contained in the polyurethane foam layer, strength, flexibility and the like. It is preferable that it is 0.3 mm, More preferably, it is 0.05-0.2 mm.

  The sheet A may be a release sheet that has been subjected to a release process. Further, the sheet A may be used as it is as a support layer without being peeled after the production of the polyurethane foam layer (polishing layer).

  As a method for applying the cell-dispersed urethane composition on the sheet A, 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 may be employed. However, any method may be used as long as a uniform coating film can be formed on the sheet A.

  In the production of the polyurethane foam layer, a known catalyst that promotes 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 application on the sheet A after the mixing step of each component.

  The polyurethane foam layer may be produced by a batch method in which each component is weighed and put into a container and mechanically stirred. In addition, each component and a non-reactive gas are continuously supplied to a stirrer 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 method for producing a polishing pad of the present invention, after the cell-dispersed urethane composition is applied on the sheet A, the sheet B is laminated on the cell-dispersed urethane composition. Thereafter, the cell-dispersed urethane composition is cured while the thickness is made uniform by the pressing means to form a polyurethane foam layer.

The sheet B to be used must have a nitrogen gas permeation rate of 1 × 10 ⁻⁷ [cm ³ / cm ² · s · cmHg] or less, preferably 1 × 10 ⁻⁸ [cm ³ / cm ² · s · cmHg] or less. Examples of the forming material satisfying the conditions include polyethylene terephthalate, polypropylene, and polyethylene. The sheet B preferably has a small dimensional change due to heat. The sheet B may be a double-sided tape having adhesive layers on both surfaces of a base material sheet made of the above material. Further, the sheet B may be a release sheet that has been subjected to a release process. Further, the sheet B may be used as it is as a support layer without being peeled after the production of the polyurethane foam layer (polishing layer).

  The thickness of the sheet B (a base sheet in the case of double-sided tape) is not particularly limited, but is 0.025 to 25% from the viewpoint of suppressing the permeability of gas contained in the polyurethane foam layer, strength, flexibility, and the like. It is preferable that it is 0.3 mm, More preferably, it is 0.05-0.2 mm.

  The pressing means for making the thickness of the sandwich sheet consisting of the sheet A, the cell-dispersed urethane composition (cell-dispersed urethane layer), and the sheet B uniform is not particularly limited, but is compressed to a constant thickness by, for example, a coater roll, a nip roll, etc. The method of doing is mentioned. In consideration of the fact that the bubbles in the foamed layer become about 1.2 to 2 times larger after compression, (compressor or nip clearance) − (thickness of sheets A and B) = (cured polyurethane foam) The thickness is preferably 50 to 85% of the thickness of the layer. In order to obtain a polyurethane foam layer having a specific gravity of 0.2 to 0.7, the specific gravity of the cell-dispersed urethane composition before passing through the roll is preferably 0.24 to 1.

  Then, 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 polyurethane foam layer. Post-curing has the effect of improving the physical properties of the polyurethane foam and is very suitable. The post cure is preferably performed at 60 to 80 ° C. for 30 minutes or more, and is preferably performed at normal pressure because the bubble shape is stabilized.

  In the present invention, it is preferable to cure the cell-dispersed urethane composition in multiple stages while making the thickness uniform by the pressing means. Such a curing step includes at least a primary cure and a secondary cure, and the primary cure is a cure temperature of 30 to 50 ° C. and a cure time of 5 to 60 minutes, and the secondary cure is a cure temperature of 60 to 80 ° C. The time is preferably 30 minutes or more. In addition, the temperature may be raised as it is after the primary cure, or the secondary cure may be performed, or after the primary cure, it may be once cooled to about room temperature and then the secondary cure.

  Then, the polyurethane foam layer upper and / or lower sheet (release sheet) is peeled off. In this case, a skin layer is formed on the surface of the polyurethane foam layer. In addition, after peeling off a release sheet, you may buff a polyurethane foam layer and may remove a skin layer by slicing. When the sheets A and B are used as the support layer, by cutting the polyurethane foam layer into two, two polishing sheets having a polyurethane foam layer (polishing layer) on the support layer can be produced.

  When the polyurethane foam layer 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 layer. Therefore, by setting the lower surface side of the formed polyurethane foam layer as the polishing surface, the polishing surface has a small variation in bubbles, and the stability of the polishing rate is further improved.

  The thickness of the polyurethane foam layer is not particularly limited, but is preferably 0.2 to 2 mm, and more preferably 0.5 to 1.5 mm.

  The polyurethane foam layer produced by the above method mainly has an open cell structure, and the open cell ratio is 50% or more, preferably 60% or more.

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

  The average cell diameter of the bubbles in the polyurethane foam layer is preferably 20 to 300 μm, more 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. When deviating from this range, the polishing rate decreases or the durability decreases.

  The specific gravity of the polyurethane foam layer is preferably 0.2 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 0.5, it is necessary to make the material have a low crosslinking 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 layer is preferably 10 to 80 degrees in terms of Asker C hardness, more preferably 15 to 35 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 have a cushion sheet bonded to one side of the polishing layer or one side of the support 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 a polishing layer and a 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 nitrogen gas transmission rate)
The nitrogen gas permeation rate [cm ³ / cm ² · s · cmHg] of the sheet was measured according to ASTM-D-1434. Specifically, it was measured by the following method. A sheet was cut into a size of 12 cmφ to prepare a sample. The sample was sandwiched between two plates having a gas permeation area of 10 cmφ, a pressure difference was applied to both surfaces of the sample, and the nitrogen gas permeation rate was calculated from the gradient of the change in nitrogen gas permeation volume at 25 ° C with respect to time. However, the pressure difference was 0.5 MPa when the sample was resin, and the pressure difference was 0.3 MPa when the sample was paper.

(Measurement of average bubble diameter)
A sample obtained by cutting the produced polyurethane foam layer 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 from the value.

(Measurement of open cell ratio)
The open cell ratio was measured according to the ASTM-2856-94-C method. However, 10 polyurethane foam layers punched into a circle were stacked as a measurement sample. As a measuring instrument, an air comparison type hydrometer 930 type (manufactured by Beckman Co., Ltd.) was used. 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 layer was cut into a 4 cm × 8.5 cm strip (thickness: arbitrary) and used 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. A sample obtained by cutting the produced polyurethane foam layer into a size of 5 cm × 5 cm (thickness: arbitrary) was used as a sample and allowed to stand for 16 hours in an environment of a temperature of 23 ° C. ± 2 ° C. and a humidity of 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.

(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 1. 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 15%, more preferably within 10%.
Polishing rate stability (%) = {(maximum polishing rate−minimum polishing rate) / total average polishing rate} × 100

Example 1
High-molecular-weight polyol EX-5030 (Asahi Glass Co., Ltd., OHV: 33, functional group number: 3) 70 parts by weight, polycaprolactone triol (manufactured by Daicel Chemical Industries, Plaxel 305, OHV: 305, functional group number: 3) 30 parts by weight, 5 parts by weight of a silicon-based surfactant (L-5340, manufactured by Toray Dow Corning Silicone) and 0.18 parts by weight of a catalyst (No. 25, manufactured by Kao) are mixed and mixed to give a second. Ingredients (25 ° C.) were prepared. The average hydroxyl value (OHVav) is 114.6 mgKOH / g (calculated value), and the average functional group number (fav) is 3 (calculated value). 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, 32.5 parts by weight of carbodiimide-modified MDI (manufactured by Nippon Polyurethane Industry Co., Ltd., Millionate MTL, NCO wt%: 29 wt%, 25 ° C.) as the first component was added to the second component (NCO / OH = 1) 0.1) Stirred for about 1 minute to prepare a cell dispersed urethane composition.

A release sheet (polyethylene terephthalate, manufactured by Toyobo Co., Ltd., Toyobo Ester E7002, thickness: 0.05 mm, nitrogen gas transmission rate: 1.15 × 10 ⁻¹⁰ [cm ³ / cm ² · s · cmHg]) to form a cell-dispersed urethane layer. A support sheet (polyethylene terephthalate, manufactured by Toyobo Co., Ltd., Toyobo Ester E5001, thickness: 0.188 mm, nitrogen gas transmission rate: 3.72 × 10 ⁻¹¹ [cm ³ / cm ² · s · cmHg]). The foam-dispersed urethane layer was made 1.3 mm thick with a nip roll (clearance 1.1 mm), first cured at 40 ° C. for 10 minutes, and then second cured at 70 ° C. for 2 hours to form a polyurethane foam layer. . Thereafter, the release sheet under the polyurethane foam layer was peeled off. Next, the surface of the polyurethane foam layer was sliced using a band saw type slicer (manufactured by Fecken) to adjust the thickness accuracy to 1.0 mm, thereby adjusting the thickness accuracy. Thereafter, a double-sided tape (double tack tape, manufactured by Sekisui Chemical Co., Ltd.) was bonded to the surface of the support sheet using a laminator to prepare a polishing pad.

Example 2
A polishing pad was prepared in the same manner as in Example 1 except that the primary curing was performed at 70 ° C. for 2 hours in Example 1 and then the secondary curing was not performed.

Example 3
Instead of the release sheet described in Example 1, a release sheet (polypropylene, manufactured by Toyobo Co., Ltd., Toyopearl SS P4256, thickness: 0.05 mm, nitrogen gas permeation rate: 2.33 × 10 ⁻⁹ [cm ³ / Cm ² · s · cmHg]) was used to prepare a polishing pad in the same manner as in Example 1.

表１から、本発明の研磨パッドは、研磨速度安定性に優れていることがわかる。比較例１のように、窒素ガス透過速度が大きい離型シート及び支持シートを用いた場合には、ポリウレタン発泡層が収縮し、また球状の気泡構造にならなかった。 Comparative Example 1
Instead of the release sheet and the support sheet described in Example 1, a release sheet (paper, manufactured by Oji Paper Co., Ltd., separator 70GS, thickness: 0.058 mm, nitrogen gas transmission rate: 1.06 × 10 ⁻⁶ [ cm ³ / cm ² · s · cm Hg]) and support sheet (paper, manufactured by Oji Paper Co., Ltd., separator 70GS, thickness: 0.058 mm, nitrogen gas transmission rate: 1.06 × 10 ⁻⁶ [cm ³ / cm ² · s · cmHg]) was used to form a polyurethane foam layer in the same manner as in Example 1. Thereafter, the release sheet and the support sheet above and below the polyurethane foam layer were peeled off. Next, both surfaces of the polyurethane foam layer were sliced using a band saw type slicer (manufactured by Fecken) to adjust the thickness accuracy to 1.0 mm, and the thickness accuracy was adjusted. Thereafter, a double-sided tape (base material: polyethylene terephthalate) was bonded to the polyurethane foam layer using a laminator to prepare a polishing pad.

From Table 1, it can be seen that the polishing pad of the present invention is excellent in polishing rate stability. As in Comparative Example 1, when a release sheet and a support sheet having a high nitrogen gas permeation rate were used, the polyurethane foam layer contracted and did not have a spherical cell structure.

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 (6)

A step of preparing a cell-dispersed urethane composition by a mechanical foaming method, wherein the cell-dispersed urethane composition is applied onto a sheet A having a nitrogen gas transmission rate of 1 × 10 ⁻⁷ [cm ³ / cm ² · s · cmHg] or less. Step, layering sheet B having a nitrogen gas permeation rate of 1 × 10 ⁻⁷ [cm ³ / cm ² · s · cmHg] or less on the applied cell-dispersed urethane composition, uniform thickness by pressing means The cell-dispersed urethane composition is cured while having a cell structure in which the open cell ratio is 50% or more, the average cell diameter is 20 to 300 μm, and the average diameter of circular holes on the surface of the open cell is 100 μm or less . a step of forming a polishing layer comprising a polyurethane foam layer seen including,
The sheet A and B are each independently a polyethylene terephthalate sheet having a thickness of 0.025 to 0.3 mm, a polypropylene sheet, or a polyethylene sheet, or a polishing pad manufacturing method that is a double-sided tape having an adhesive layer on both sides of the sheet. . The curing step includes at least a primary cure and a secondary cure, and the primary cure is a cure temperature of 30 to 50 ° C. and a cure time of 5 to 60 minutes, and the secondary cure is a cure temperature of 60 to 80 ° C. and a cure time of 30 minutes. The method for producing a polishing pad according to claim 1, which is described above. The manufacturing method of the polishing pad of Claim 1 or 2 including the process of peeling the sheet | seat A of the lower surface side of a thermosetting polyurethane foam layer. The cell-dispersed urethane composition includes an isocyanate component and an active hydrogen-containing compound, and the isocyanate component is 4,4′-diphenylmethane diisocyanate or carbodiimide-modified MDI, and the active hydrogen-containing compound has 2 to 4 functional groups. The manufacturing method of the polishing pad in any one of Claims 1-3 which contain 60-85 weight% of high molecular weight polyols with a hydroxyl value of 20-100 mgKOH / g. The polishing pad manufactured by the method in any one of Claims 1-4 . 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 5.

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