JP5377909B2 - Polishing pad and manufacturing method thereof - Google Patents

Description

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

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

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

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

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

  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.

  In order to solve the above problem, a polishing pad provided with a polishing layer on a base material layer, wherein the polishing layer has a substantially spherical open cell having an average cell diameter of 35 to 300 μm. A polishing pad characterized by comprising a body has been proposed (Patent Document 6).

  Further, the conventional polishing pad has a problem in that the polishing property is poor and the life is short because the polishing dust (particularly, pad dust) is easily clogged in the bubbles.

  Further, as a method for producing a polyurethane foam by water foaming, (a) a raw material composition containing as a main component a polyol containing 0.01 to 0.10% by weight of water and a raw material composition containing an isocyanate as a main component are at least A step of mixing or dissolving 1 to 50% by volume of gas in at least one raw material composition of two or more raw material compositions to be included; and (b) supplying the two or more raw material compositions to the mixing head. And (c) a method for producing a polyurethane foam, which includes a step of discharging the mixed raw material composition from a mixing head to the outside (Patent Document 7).

JP 2003-37089 A JP 2003-1000068 A1 JP 2004-291155 A JP 2004-335713 A JP 2006-75914 A JP 2008-87148 A JP 2006-206625 A

  An object of this invention is to provide the polishing pad which is excellent in durability, and is excellent in the stability of a grinding | polishing characteristic, and a lifetime characteristic.

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

That is, the present invention is a polishing pad in which a polishing layer is provided on a base material layer,
The polishing layer is made of a thermosetting polyurethane foam containing substantially spherical open cells having openings,
The thermosetting polyurethane foam is a reaction cured product of a urethane composition containing an isocyanate component, an active hydrogen group-containing compound, water 0.09 to 0.55% by weight, and a silicon surfactant,
The active hydrogen group-containing compound contains 2 to 30% by weight of a low molecular weight component,
The polishing layer relates to a polishing pad having an average cell diameter of 100 to 300 μm, an average opening diameter of 40 to 90 μm, and an Asker C hardness of 40 to 95 degrees.

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

  In addition, the present inventors can expand the average opening diameter of the openings of open cells to 40 to 90 μm by adding 0.09 to 0.55% by weight of water as a foaming agent to the urethane composition. As a result, it was found that polishing debris was less likely to accumulate in the open cells, and the stability of the polishing rate and the life characteristics were further improved.

  In addition, the present inventors have incorporated a low molecular weight component in an active hydrogen group-containing compound in an amount of 2 to 30% by weight, so that a polyurethane can be formed from a raw material constituting a polyurethane resin without using an open cell agent such as inorganic particles. It has been found that the foam can be made open-celled.

  When the average bubble diameter of the polishing layer is less than 100 μm, polishing scraps (particularly pad scraps) are accumulated, and the bubbles cannot sufficiently play a role of holding the slurry. When is added, “sagging” tends to occur, resulting in poor durability.

  When the average opening diameter of the openings of the open bubbles is less than 40 μm, polishing dust (especially, pad scraps) easily accumulates in the open bubbles, and when it exceeds 90 μm, the polishing dust enters the open bubbles. However, when the pressure is repeatedly applied to the polishing layer, “sagging” tends to occur, resulting in poor durability.

  When the Asker C hardness of the polishing layer is less than 40 degrees, the opening of the open cells tends to be crushed during polishing, and polishing debris (especially, pad debris) easily accumulates in the open bubbles, and exceeds 95 degrees. Is likely to generate scratches on the object to be polished.

  The active hydrogen group-containing compound preferably contains 50 to 90% by weight of polyethylene glycol having a hydroxyl value of 50 to 200 mgKOH / g and an average hydroxyl value of 250 to 450 mgKOH / g. By using the active hydrogen group-containing compound, the affinity between the polishing layer and the slurry is increased, and the opening of the open cells during polishing can be suppressed by increasing the hardness of the polishing layer. Thereby, the discharge property of the polishing dust in the open bubbles is improved, and the stability of the polishing rate and the life characteristics are further improved.

  When the hydroxyl value of polyethylene glycol is less than 50 mgKOH / g, the polishing pad expands during polishing and the stability of the polishing characteristics tends to decrease. On the other hand, when it exceeds 200 mgKOH / g, the polishing layer and slurry As a result, the polishing rate stability becomes difficult to improve. In addition, when the content of polyethylene glycol is less than 50% by weight, the affinity between the polishing layer and the slurry becomes insufficient and it becomes difficult to improve the polishing rate stability. On the other hand, when the content exceeds 90% by weight The polishing pad expands during polishing and the stability of the polishing characteristics tends to decrease. Further, when the average hydroxyl value of the active hydrogen group-containing compound is less than 250 mgKOH / g, the hardness of the polishing layer is not sufficiently increased by crosslinking, so that the opening of open cells tends to be crushed during polishing, and 450 mgKOH / g is reduced. When exceeding, the hardness of the polishing layer becomes too high and scratches are likely to occur on the object to be polished.

  The polishing layer preferably has a specific gravity of 0.2 to 0.6. Thereby, a decrease in the hardness of the polishing layer over time can be suppressed.

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

Further, the present invention mechanically stirs a urethane composition containing an isocyanate component, an active hydrogen group-containing compound containing 2 to 30% by weight of a low molecular weight component, a silicon surfactant, and 0.09 to 0.55% by weight of water. The step of preparing the cell-dispersed urethane composition, the step of applying the cell-dispersed urethane composition on the base material layer, and the curing of the cell-dispersed urethane composition, the thermosetting having substantially spherical open cells with openings. A step of forming a porous polyurethane foam and a step of forming a polishing layer by uniformly adjusting the thickness of the thermosetting polyurethane foam,
The said polishing layer is related with the manufacturing method of the polishing pad whose average bubble diameter is 100-300 micrometers, average opening diameter is 40-90 micrometers, and Asker C hardness is 40-95 degree | times.

Further, the present invention mechanically stirs a urethane composition containing an isocyanate component, an active hydrogen group-containing compound containing 2 to 30% by weight of a low molecular weight component, a silicon surfactant, and 0.09 to 0.55% by weight of water. The step of preparing the cell-dispersed urethane composition, the step of applying the cell-dispersed urethane composition on the release sheet, the step of laminating the base material layer on the cell-dispersed urethane composition, and making the thickness uniform by pressing means A step of forming a thermosetting polyurethane foam having substantially spherical open cells having openings by curing the cell-dispersed urethane composition, a step of peeling the release sheet under the thermosetting polyurethane foam, and Removing the exposed skin layer on the surface of the thermosetting polyurethane foam to form a polishing layer;
The said polishing layer is related with the manufacturing method of the polishing pad whose average bubble diameter is 100-300 micrometers, average opening diameter is 40-90 micrometers, and Asker C hardness is 40-95 degree | times.

  In the method for producing a polishing pad of the present invention, the active hydrogen group-containing compound contains 50 to 90% by weight of polyethylene glycol having a hydroxyl value of 50 to 200 mgKOH / g and an average hydroxyl value of 250 to 450 mgKOH / g. It is preferable.

  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) containing substantially spherical open cells having an opening, 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 foam is a urethane containing an isocyanate component, an active hydrogen group-containing compound (high molecular weight polyol, low molecular weight component (including a chain extender)), water 0.09 to 0.55% by weight, and a silicon-based surfactant. It is the reaction hardening body of a composition. When a polyurethane foam is produced by the prepolymer method, it is a high molecular weight polyol (which may further contain a low molecular weight component) that is a raw material for the isocyanate-terminated prepolymer, and a curing agent for the isocyanate-terminated prepolymer. The chain extender is an active hydrogen group-containing compound.

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

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

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

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

  In the present invention, polyethylene glycol having a hydroxyl value of 50 to 200 mgKOH / g is preferably used as the high molecular weight polyol. The hydroxyl value of polyethylene glycol is more preferably 50 to 150 mgKOH / g.

  The polyethylene glycol is preferably blended in an amount of 50 to 90% by weight in the active hydrogen group-containing compound, more preferably 55 to 85% by weight.

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

  Among these, it is preferable to use a low molecular weight polyol having a hydroxyl value of 400 to 1830 mgKOH / g and / or a low molecular weight polyamine having an amine value of 400 to 1870 mgKOH / g. The hydroxyl value is more preferably 900 to 1500 mgKOH / g, and the amine value is more preferably 400 to 950 mgKOH / g. When the hydroxyl value is less than 400 mgKOH / g or the amine value is less than 400 mgKOH / g, the effect of improving the formation of open cells tends to be insufficient. On the other hand, when the hydroxyl value exceeds 1830 mgKOH / g or the amine value exceeds 1870 mgKOH / g, scratches are likely to occur on the wafer surface. In particular, it is preferable to use at least one selected from the group consisting of diethylene glycol, 1,2-propylene glycol, 1,3-butanediol, 1,4-butanediol, and trimethylolpropane.

  In order to make the polyurethane foam into an open-cell structure, the low molecular weight component needs to be contained in a total of 2 to 30% by weight in the active hydrogen group-containing compound, preferably 5 to 30% by weight. By using a specific amount of the low molecular weight component, the cell membrane is easily broken and not only is easy to form open cells, but also the mechanical properties of the polyurethane foam are improved.

  When the polyurethane foam 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 Njiamin, N, N'-di -sec- butyl -p- phenylenediamine, m- phenylenediamine, and polyamines are illustrated in the p- xylylenediamine, or can include low molecular weight components described above. These may be used alone or in combination of two or more.

  The active hydrogen group-containing compound preferably has an average hydroxyl value of 250 to 450 mgKOH / g, more preferably 270 to 430 mgKOH / g.

上記式において、ｎは高分子量ポリオール及び低分子量成分の成分数、ａｉは水酸基価、ｃｉは添加重量部である。
例えば、使用する活性水素基含有化合物が第１〜第ｎ成分まである場合、第１成分の水酸基価をａ１、及び添加重量部をｃ１とし、・・・、第ｎ成分の水酸基価をａｎ、及び添加重量部をｃｎとする。 The average hydroxyl value (OHVav) is calculated by the following formula.

In the above formula, n is the number of components of the high molecular weight polyol and the low molecular weight component, ai is the hydroxyl value, and ci is the added part by weight.
For example, when the active hydrogen group-containing compound to be used is from the first to the n-th component, the hydroxyl value of the first component is a1, the added weight part is c1, ..., the hydroxyl value of the n-th component is an, And the added weight part is cn.

  The ratio of the isocyanate component and the active hydrogen group-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 in the isocyanate component relative to the total number of active hydrogen groups (hydroxyl groups + amino groups) in the active hydrogen group-containing compound is preferably 0.80 to 1.20. More preferably, it is 0.99 to 1.15. When the number of isocyanate groups is outside the above range, curing failure occurs and the required specific gravity, hardness, compression ratio, etc. tend not to be obtained.

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

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

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

  In particular, a mechanical foaming method using a silicon surfactant which is a polyalkylsiloxane or a copolymer of an alkylsiloxane and a polyetheralkylsiloxane is preferable. Examples of suitable silicon surfactants include SH-192 and L-5340 (manufactured by Toray Dow Corning Silicone), B8443, B8465 (manufactured by Goldschmidt), and the like.

  The silicon-based surfactant is preferably added to the urethane composition in an amount of 0.1 to 5% by weight, more preferably 0.2 to 3% by weight.

  In the present invention, in order to form a polishing layer having a specific open-cell structure, it is necessary to add 0.09 to 0.55% by weight of water as a foaming agent to the urethane composition. Is added in an amount of 0.1 to 0.3% by weight.

  If necessary, stabilizers such as antioxidants, lubricants, pigments, fillers, antistatic agents, and other additives may be added.

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

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

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

  (3) A silicon-based surfactant and water are added to at least one of the first component containing the isocyanate component (or isocyanate-terminated prepolymer) and the second component containing the active hydrogen group-containing compound, and the first component and the first component are added. The two components are mechanically stirred in the presence of a non-reactive gas, and the non-reactive gas is dispersed as fine bubbles to prepare a cell-dispersed urethane composition.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

  The polishing layer produced by the above method has an open cell structure with an average cell diameter of 100 to 300 μm and an average opening diameter of 40 to 90 μm. The average bubble diameter is preferably 140 to 250 μm, and the average opening diameter is preferably 45 to 80 μm.

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

  The hardness of the polishing layer needs to be 40 to 95 degrees with an Asker C hardness meter.

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

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

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

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

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

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

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

(Measurement of hardness)
This was performed according to JIS K-7312. The produced polyurethane foam was cut into a size of 5 cm × 5 cm (thickness: arbitrary) as a sample and allowed to stand for 16 hours in an environment of temperature 23 ° C. ± 2 ° C. and humidity 50% ± 5%. At the time of measurement, the samples were overlapped to have a thickness of 10 mm or more. Using a hardness meter (manufactured by Kobunshi Keiki Co., Ltd., Asker C type hardness meter, pressure surface height: 3 mm), the hardness 60 seconds after contacting the pressure surface was measured.

(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 sheet to the number of processed sheets) 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
In a container, 60 parts by weight of polyethylene glycol having a number average molecular weight of 1000 (PEG 1000, hydroxyl value: 112 mg KOH / g, functional group number 2), polycaprolactone triol (manufactured by Daicel Chemical Industries, PCL305, hydroxyl value: 305 mg KOH / g, functional group number 3) ) 25 parts by weight, 5 parts by weight of trimethylolpropane (TMP, hydroxyl value: 1255 mg KOH / g, functional group number 3), 10 parts by weight of diethylene glycol (DEG, hydroxyl value: 1057 mg KOH / g, functional group number 3), 0.5 weight of water Part, silicon surfactant (manufactured by Goldschmidt, B8443) 1 part by weight and catalyst (manufactured by Kao, No. 25) 0.14 part by weight were mixed to prepare a second component (25 ° C.). . 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, 97 parts by weight of carbodiimide-modified MDI (manufactured by Nippon Polyurethane Industry, Millionate MTL, NCO wt%: 29 wt%, 25 ° C.) as the first component was added to the container (NCO / OH = 1.1) and stirred for about 30 seconds. Thus, a cell dispersed urethane composition was prepared.

  The prepared cell-dispersed urethane composition was applied onto a release-treated release sheet (manufactured by Toyobo, polyethylene terephthalate, thickness: 0.1 mm) to form a cell-dispersed urethane layer. And the base material layer (polyethylene terephthalate, thickness: 0.2 mm) was covered on this cell dispersion | distribution urethane layer. The cell-dispersed urethane layer is made 1.5 mm thick with a nip roll, and then cured at 70 ° C. for 3 hours to form a polyurethane foam (open cell structure, average cell diameter: 157 μm, average opening diameter: 63 μm, specific gravity: 0.39) , C hardness: 83 degrees). Thereafter, the release sheet under the polyurethane foam was peeled off. Next, the surface of the polyurethane foam is sliced by using a band saw type slicer (manufactured by Fecken) to a thickness of 1.2 mm, and the thickness accuracy is adjusted by buffing to obtain a polishing layer having a thickness of 1.0 mm. Formed. The polyurethane foam had substantially spherical open cells. Thereafter, a double-sided tape (double tack tape, manufactured by Sekisui Chemical Co., Ltd.) was bonded to the surface of the base material layer using a laminator to prepare a polishing pad.

Examples 2-7 and Comparative Examples 1-7
A polishing pad was prepared in the same manner as in Example 1 except that the blending ratio shown in Table 1 was adopted. The compounds in Table 1 are as follows.
PTMG1000: polytetramethylene ether glycol having a number average molecular weight of 1000, hydroxyl value: 112 mgKOH / g, functional group number 2
PEG 600: polyethylene glycol having a number average molecular weight of 600, hydroxyl value: 187 mg KOH / g, number of functional groups: 2
PEG2000: polyethylene glycol having a number average molecular weight of 2000, hydroxyl value: 56 mgKOH / g, number of functional groups: 2
PCL210: Polycaprolactone diol (manufactured by Daicel Chemical Industries, hydroxyl value: 112 mg KOH / g, number of functional groups 2)
・ L5340: Silicone surfactant (manufactured by Toray Dow Corning Silicone)

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

Explanation of symbols

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

Claims (8)

In the polishing pad provided with the polishing layer on the base material layer,
The polishing layer is made of a thermosetting polyurethane foam containing substantially spherical open cells having openings,
The thermosetting polyurethane foam is a reaction cured product of a urethane composition containing an isocyanate component, an active hydrogen group-containing compound, water 0.09 to 0.55% by weight, and a silicon surfactant,
The active hydrogen group-containing compound contains 2 to 30% by weight of a low molecular weight component,
The polishing pad, wherein the polishing layer has an average bubble diameter of 100 to 300 μm, an average opening diameter of 40 to 90 μm, and an Asker C hardness of 40 to 95 degrees. The polishing pad according to claim 1, wherein the active hydrogen group-containing compound contains 50 to 90% by weight of polyethylene glycol having a hydroxyl value of 50 to 200 mgKOH / g and an average hydroxyl value of 250 to 450 mgKOH / g. The polishing pad according to claim 1, wherein the polishing layer has a specific gravity of 0.2 to 0.6. The polishing pad according to claim 1, wherein the polishing layer is self-adhering to the base material layer. Cellulose-dispersed urethane composition by mechanically stirring a urethane composition containing an isocyanate component, an active hydrogen group-containing compound containing 2 to 30% by weight of a low molecular weight component, a silicon surfactant, and 0.09 to 0.55% by weight of water Forming a product, applying a cell-dispersed urethane composition on a base material layer, and curing the cell-dispersed urethane composition to form a thermosetting polyurethane foam having substantially spherical open cells with openings. And a step of uniformly adjusting the thickness of the thermosetting polyurethane foam to form a polishing layer,
The polishing layer is a method for producing a polishing pad, wherein the average bubble diameter is 100 to 300 μm, the average opening diameter is 40 to 90 μm, and the Asker C hardness is 40 to 95 degrees. Cellulose-dispersed urethane composition by mechanically stirring a urethane composition containing an isocyanate component, an active hydrogen group-containing compound containing 2 to 30% by weight of a low molecular weight component, a silicon surfactant, and 0.09 to 0.55% by weight of water A step of preparing a product, a step of applying a cell-dispersed urethane composition on a release sheet, a step of laminating a base material layer on the cell-dispersed urethane composition, a cell-dispersed urethane composition with a uniform thickness by pressing means A step of forming a thermosetting polyurethane foam having substantially spherical open cells having openings, a step of peeling a release sheet under the thermosetting polyurethane foam, and an exposed thermosetting polyurethane Including a step of forming a polishing layer by removing the skin layer on the foam surface,
The polishing layer is a method for producing a polishing pad, wherein the average bubble diameter is 100 to 300 μm, the average opening diameter is 40 to 90 μm, and the Asker C hardness is 40 to 95 degrees. The polishing pad according to claim 5 or 6, wherein the active hydrogen group-containing compound contains 50 to 90% by weight of polyethylene glycol having a hydroxyl value of 50 to 200 mgKOH / g and an average hydroxyl value of 250 to 450 mgKOH / g. 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.

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