JP2011235416A - Method for manufacturing polishing pad - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a polishing pad having fine and uniform bubbles and increased polishing speed, and to provide the polishing pad obtained by the method.SOLUTION: This method includes a process for preparing a bubble dispersion urethane composition containing an isocyanate compound, an active hydrogen-containing compound and a silicon-based surfactant by a mechanical foaming method, a process for injecting the bubble dispersion urethane composition into a mold, a process for preparing a thermosetting polyurethane foam block by curing the bubble dispersion urethane composition and a process for preparing a thermosetting polyurethane foam sheet by cutting the thermosetting polyurethane foam block. An average hydroxyl value of the active hydrogen containing compound is 260-400 mgKOH/g. The bubble dispersion urethane composition contains 10-40 pts.wt. of a heat storage agent having a melting point of 70-110°C and a hydroxy group or an urethane group in 100 pts.wt. of the active hydrogen containing compound.

Description

  The present invention relates to an optical material such as a lens and a reflection mirror, a compound semiconductor substrate such as a silicon wafer, silicon carbide, and sapphire, a glass substrate for a hard disk, and a polishing pad used for polishing the surface of an aluminum substrate and a method for manufacturing the same. . In particular, the polishing pad of the present invention is suitably used as a polishing pad for finishing.

  When manufacturing a semiconductor device, a process of forming a conductive film on the wafer surface and forming a wiring layer by photolithography, etching, or the like, a process of forming an interlayer insulating film on the wiring layer, etc. These steps are performed, and irregularities made of a conductor such as metal or an insulator are generated on the wafer surface. In recent years, miniaturization of wiring and multilayer wiring have been advanced for the purpose of increasing the density of semiconductor integrated circuits, and along with this, technology for flattening the irregularities on the wafer surface has become important.

  As a method for flattening the irregularities on the wafer surface, chemical mechanical polishing (hereinafter referred to as CMP) is generally employed. CMP is a technique of polishing using a slurry-like abrasive (hereinafter referred to as slurry) in which abrasive grains are dispersed in a state where the surface to be polished of a wafer is pressed against the polishing surface of a polishing pad. As shown in FIG. 1, for example, a polishing apparatus generally used in CMP includes a polishing surface plate 2 that supports a polishing pad 1 and a support base (polishing head) 5 that supports a material to be polished (semiconductor wafer) 4. And a backing material for uniformly pressing the wafer, and a slurry 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 material to be polished 4 supported by each of the polishing surface plate 2 and the support base 5 are opposed to each other, and are provided with rotating shafts 6 and 7 respectively. Further, a pressurizing mechanism for pressing the workpiece 4 against the polishing pad 1 is provided on the support base 5 side.

  As a manufacturing method of a polishing pad used for such a polishing operation, for example, the following manufacturing method has been proposed.

  A silicon-based surfactant is added to the first component containing the isocyanate-terminated prepolymer, and the first component is further stirred with a non-reactive gas to prepare a bubble dispersion in which the non-reactive gas is dispersed as fine bubbles. To do. A foaming reaction solution is prepared by mixing a second component containing a chain extender into the cell dispersion. The foaming reaction liquid is poured into a mold, heated, and cured by reaction to produce a polyurethane resin foam block. Thereafter, a method of manufacturing a polishing pad made of a polyurethane resin foam sheet by slicing a polyurethane resin foam block has been proposed (Patent Document 1).

  In the case of a method of producing a polyurethane resin foam block using an isocyanate-terminated prepolymer and a chain extender as in Patent Document 1 (so-called prepolymer method), the reaction temperature inside the block is not so high. Therefore, the bubbles inside the block do not expand so much, and fine and uniform bubbles are formed.

  However, in the case of a method for producing a polyurethane resin foam block using an isocyanate compound and an active hydrogen-containing compound having a large average hydroxyl value (so-called one-shot method), the reaction temperature inside the block becomes considerably high. Therefore, when a block having a thickness of 30 mm or more is produced, the bubbles inside the block are thermally expanded, or the bubbles are liable to be coarsened due to the combination of the bubbles due to thermal expansion. As a result, coarse bubbles and non-uniform bubbles are formed. A polishing pad made of a polyurethane resin foam sheet having coarse bubbles and non-uniform bubbles has problems such as a low polishing rate and a tendency to scratch on the surface of the material to be polished.

  In Patent Document 2, in order to produce a high-magnification foam with uniform and fine bubbles and a smooth surface, a thermoplastic resin is melted in an extruder, and an inorganic gas is injected into the melt. The water-absorbing polymer having absorbed 3 to 80% by weight of water is press-fitted in an amount of 0.1 to 30 parts by weight with respect to 100 parts by weight of the thermoplastic resin, and after melt-kneading, the melt is extruded from the extruder and foamed. A method for producing a featured thermoplastic resin foam is proposed.

In US Pat. No. 6,057,033, in order to prevent the quality of the foam from being deteriorated by overheating of a part of the mixture during the foaming process and to produce a high-quality polymer foam, the temperature in the foamable mixture is The addition of compounds capable of endothermic decomposition is described.

Patent Document 4 manufactures a heat storage mechanical floss type polyurethane foam that can prevent stuffiness in applications such as bedding and clothing, and that has a temperature control function in shock absorbing packaging materials such as precision OA equipment. In order to achieve this, it is described that heat storage particles are blended in a mechanical floss type polyurethane foam. As the heat storage particles, a microcapsule in which a latent heat storage agent is included in a shell is described. The invention of Patent Document 4 contains heat storage particles in polyurethane foam in order to prevent bedding, clothing, etc. from being stored and steamed, and heat storage particles to prevent bubbles from thermally expanding during production. It is not necessarily blended.

JP 2006-282993 A JP-A-5-320400 Special table 2007-50185 gazette JP 2001-294640 A

  An object of the present invention is to provide a method for producing a polishing pad having fine and uniform bubbles and a high polishing rate, and a polishing pad obtained by the production method. Moreover, it aims at providing the manufacturing method of the semiconductor device using this polishing pad.

  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 following polishing pad manufacturing method, and have completed the present invention.

That is, the present invention includes a step of preparing a cell-dispersed urethane composition containing an isocyanate compound, an active hydrogen-containing compound, and a silicon-based surfactant by a mechanical foaming method, a step of injecting the cell-dispersed urethane composition into a mold, A polishing pad comprising a step of producing a thermosetting polyurethane foam block by curing a cell-dispersed urethane composition, and a step of producing a thermosetting polyurethane foam sheet by cutting the thermosetting polyurethane foam block In the manufacturing method,
The active hydrogen-containing compound has an average hydroxyl value of 260 to 400 mgKOH / g,
The cell-dispersed urethane composition contains a heat storage agent having a melting point of 70 to 110 ° C. and a hydroxyl group or a urethane group in an amount of 10 to 40 parts by weight with respect to 100 parts by weight of the active hydrogen-containing compound. Manufacturing method.

  When the average hydroxyl value of the active hydrogen-containing compound is 260 mgKOH / g or more, the composition easily generates heat due to the reaction with the isocyanate compound, and the temperature inside the block becomes considerably high. For this reason, the bubbles inside the block are thermally expanded, or the bubbles are likely to become coarse due to the combination of the bubbles due to thermal expansion. As in the present invention, by adding a heat storage agent having a melting point of 70 to 110 ° C. and having a hydroxyl group or a urethane group to the cell-dispersed urethane composition, the bubbles inside the block are effectively expanded. Can be prevented. As a result, a polyurethane foam sheet having fine and uniform cells is obtained.

  When the average hydroxyl value of the active hydrogen-containing compound exceeds 400 mgKOH / g, the pot life becomes too short, so that the composition cannot be sufficiently stirred, and the non-reactive gas can be dispersed as fine bubbles. Can not. Further, the composition is very likely to generate heat, and even if a large amount of heat storage agent is added, it is difficult to prevent thermal expansion of bubbles. Furthermore, the degree of crosslinking of the polyurethane foam becomes too high and becomes brittle.

In the present invention, it is necessary to use a heat storage agent having a melting point of 70 to 110 ° C. and having a hydroxyl group or a urethane group. When the melting point is less than 70 ° C., the urethanization reaction does not proceed smoothly and the pot life becomes too long, which is not preferable for production. On the other hand, when the melting point exceeds 110 ° C., the melting point is too high to absorb heat generated by the urethanization reaction, and thermal expansion of bubbles inside the block cannot be prevented.

  Moreover, since the heat storage agent having a hydroxyl group or a urethane group can react with an isocyanate compound or an active hydrogen-containing compound and can be bonded to a polyurethane molecule, the generation of bloom can be effectively prevented. . In addition, when a heat storage agent having a hydroxyl group or a urethane group is used, dispersibility in the cell-dispersed urethane composition is improved, so that thermal expansion of the cells can be effectively prevented throughout the block. As a result, a polyurethane foam sheet having fine and uniform cells is obtained.

  It is necessary to add 10 to 40 parts by weight of the heat storage agent with respect to 100 parts by weight of the active hydrogen-containing compound. When the addition amount of the heat storage agent is less than 10 parts by weight, the heat generated by the urethanization reaction cannot be sufficiently absorbed, and thus thermal expansion of bubbles inside the block cannot be prevented. On the other hand, when the amount exceeds 40 parts by weight, the physical properties of the urethane matrix itself are lowered by plasticization, so that the polishing characteristics (particularly the polishing rate) of the polishing pad are deteriorated.

  The heat storage agent is preferably a modified wax-based latent heat storage agent having a heat of fusion of 100 kJ / kg or more. When the amount of heat of fusion is less than 100 kJ / kg, the heat generated by the urethanization reaction cannot be sufficiently absorbed, so it is necessary to increase the amount of heat storage agent added. The latent heat type heat storage agent is preferable because it has a large endothermic effect and can sufficiently absorb the generated heat even when added in a small amount. In addition, a hydrate type heat storage agent is not preferable because moisture is vaporized at the time of melting and voids are easily generated in the block. Therefore, it is preferable to use a modified wax-based heat storage agent.

Moreover, this invention relates to the polishing pad obtained by the said manufacturing method.

  Furthermore, the present invention relates to a semiconductor device manufacturing method including a step of polishing a surface of a semiconductor wafer using the polishing pad.

  The polishing pad obtained by the production method of the present invention has fine and uniform bubbles, has a high polishing rate, and can effectively suppress the generation of scratches.

It is the schematic which shows an example of the grinding | polishing apparatus used by CMP grinding | polishing.

  The method for producing a polishing pad of the present invention comprises a step of preparing a cell-dispersed urethane composition containing an isocyanate compound, an active hydrogen-containing compound, and a silicon surfactant by a mechanical foaming method, and a cell-dispersed urethane composition in a mold. A step of injecting, a step of producing a thermosetting polyurethane foam block (hereinafter referred to as a polyurethane foam block) by curing the cell-dispersed urethane composition, and a thermosetting polyurethane foam by cutting the polyurethane foam block A step of producing a sheet (hereinafter referred to as a polyurethane foam sheet) is included.

  Polyurethane resin is excellent in abrasion resistance, and it is possible to easily obtain polymers having desired physical properties by changing the raw material composition. Also, it is easy to form almost spherical fine bubbles by mechanical foaming (including mechanical flossing). Since it can be formed, it is a preferable material for forming the polishing layer.

  The polyurethane resin is composed of an isocyanate compound and an active hydrogen-containing compound (high molecular weight polyol, low molecular weight polyol, low molecular weight polyamine, etc.).

  The manufacturing method of the polishing pad of the present invention is an effective manufacturing method when the average hydroxyl value of the active hydrogen-containing compound is 260 to 400 mgKOH / g, and the average hydroxyl value of the active hydrogen-containing compound is 260 to 400 mgKOH / g. It is necessary to adjust each component so that it becomes.

  As the isocyanate compound, 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 compound, in addition to the diisocyanate compound, a polyfunctional polyisocyanate compound having three or more functions can be used. 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 compounds, 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.

  The number average molecular weight of the high molecular weight polyol is not particularly limited, but is preferably 500 to 2000 from the viewpoint of the elastic properties of the resulting polyurethane resin. When the number average molecular weight is less than 500, a polyurethane resin using the number average molecular weight does not have sufficient elastic properties and becomes a brittle polymer. Therefore, the polishing layer produced from this polyurethane resin becomes too hard and causes a scratch on the wafer surface. Moreover, since it becomes easy to wear, it is not preferable from the viewpoint of the pad life. On the other hand, when the number average molecular weight exceeds 2000, a polyurethane resin using the number average molecular weight becomes too soft, and a polishing layer produced from this polyurethane resin tends to have poor planarization characteristics.

  Of the above high molecular weight polyols, it is preferable to use a trifunctional polyol having a hydroxyl value of 150 to 400 mgKOH / g. The hydroxyl value is more preferably 200 to 350 mgKOH / g. The trifunctional polyol is more preferably polycaprolactone triol. When the hydroxyl value is less than 150 mgKOH / g, the amount of polyurethane hard segments tends to decrease and durability tends to decrease. When the hydroxyl value exceeds 400 mgKOH / g, the degree of crosslinking of the polyurethane foam becomes too high. Tend to be brittle.

  The blending amount of the trifunctional polyol having a hydroxyl value of 150 to 400 mgKOH / g is not particularly limited, and is appropriately determined depending on the properties required for the polishing layer. However, the active hydrogen-containing compound may contain 10 to 70% by weight. Preferably, it is 20 to 60% by weight.

  Moreover, it is preferable to use the bifunctional polyol whose hydroxyl value is 50-250 mgKOH / g with the trifunctional polyol whose hydroxyl value is 150-400 mgKOH / g. The hydroxyl value of the bifunctional polyol is more preferably 100 to 150 mgKOH / g. The bifunctional polyol is more preferably polycaprolactone diol.

  The blending amount of the bifunctional polyol having a hydroxyl value of 50 to 250 mgKOH / g is not particularly limited and is appropriately determined depending on the properties required for the polishing layer, but 20 to 80% by weight is contained in the active hydrogen-containing compound. Preferably, it is 30 to 70% by weight.

  Along with high molecular weight polyol, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol, diethylene glycol, triethylene glycol, 1,4-bis (2-hydroxyethoxy) benzene, tri Methylolpropane, glycerin, 1,2,6-hexanetriol, pentaerythritol, tetramethylolcyclohexane, methyl glucoside, sorbitol, mannitol, dulcitol, sucrose, 2,2,6,6-tetrakis (hydroxymethyl) cyclo Hexanol, 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. 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. In particular, it is preferable to use diethylene glycol, 1,4-butanediol, or trimethylolpropane. The blending amount of the low molecular weight polyol and the like is not particularly limited and is appropriately determined depending on the properties required for the polishing layer, but is preferably 5 to 25% by weight in the active hydrogen-containing compound.

  The ratio of the isocyanate compound and the active hydrogen-containing compound can be variously changed depending on the molecular weight of each and the desired physical properties of the polyurethane foam. In order to obtain a foam having desired characteristics, the number of isocyanate groups of the isocyanate compound relative to the total number of active hydrogen groups (hydroxyl group + amino group) of the active hydrogen-containing compound is preferably 0.80 to 1.20, More preferably, it is 0.99 to 1.15. When the number of isocyanate groups is outside the above range, curing failure occurs and the required specific gravity, hardness, compression ratio, etc. tend not to be obtained.

  In the present invention, a polyurethane foam block is produced by a one-shot method.

  The polyurethane foam block is produced by a mechanical foaming method (including a mechanical floss method) using a silicon-based surfactant.

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

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

  If necessary, stabilizers such as antioxidants, lubricants, pigments, fillers, antistatic agents, and other additives may be added. Moreover, you may add the catalyst which accelerates | stimulates well-known polyurethane reactions, such as a tertiary amine type | system | group. The type and amount of the catalyst are selected in consideration of the flow time that flows into the mold after the mixing step.

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

  (1) A silicon-based surfactant and a heat storage agent having a melting point of 70 to 110 ° C. and a hydroxyl group or a urethane group are added to at least one of the first component containing the isocyanate compound and the second component containing the active hydrogen-containing compound. Then, the component to which the silicon-based surfactant is added is mechanically stirred in the presence of the 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.

  (2) A silicon-based surfactant and a heat storage agent having a melting point of 70 to 110 ° C. and a hydroxyl group or a urethane group are added to at least one of the first component containing the isocyanate compound and the second component containing the active hydrogen-containing compound. The first component and the second component 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 heat storage agent having a melting point of 70 to 110 ° C. and having a hydroxyl group or a urethane group is not coated with a microcapsule or the like (uncoated type), and is preferably a solid-liquid phase change type heat storage agent. . The liquid phase-gas phase change type heat storage agent is not preferable because water is vaporized at the time of melting and voids are easily generated in the block. The melting point is preferably 75 to 100 ° C. In addition, a hydrate type heat storage agent is not preferable because moisture is vaporized at the time of melting and voids are easily generated in the block. Therefore, it is preferable to use a modified wax-based heat storage agent. The heat of fusion of the heat storage agent is preferably 100 kJ / kg or more, more preferably 120 kJ / kg or more.

  Examples of the heat storage agent having the above-described characteristics include a modified wax-based latent heat storage agent having a melting point of 75 ° C. and a hydroxyl group (Nippon Seiwa Co., Ltd., NPS9210, heat of fusion: 150 kJ / kg), melting point of 80 ° C. and urethane group Modified wax-based latent heat storage agent (manufactured by Nippon Seiwa Co., Ltd., NPS 6115, heat of fusion: 150 kJ / kg), modified wax-based latent heat storage agent having a melting point of 100 ° C. and having a urethane group (manufactured by Nippon Seiwa Co., Ltd., HAD5150, Heat of fusion: 130 kJ / kg).

  In the case of a solid-liquid phase change type heat storage agent, the particle size is preferably 10 μm or less, more preferably 1 μm or less.

  The heat storage agent needs to be added in an amount of 10 to 40 parts by weight, preferably 15 to 40 parts by weight, based on 100 parts by weight of the active hydrogen-containing compound.

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

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

  As the stirring device for dispersing the non-reactive gas in the form of fine bubbles, a known stirring device can be used without any particular limitation. Specifically, a homogenizer, a dissolver, a two-axis planetary mixer (planetary mixer), a mechanical A floss foaming machine etc. are illustrated. The shape of the stirring blade of the stirring device is not particularly limited, but it is preferable to use a whipper type stirring blade because fine bubbles can be obtained. In order to obtain the target polyurethane foam, the rotational speed of the stirring blade is preferably 1000 to 2000 rpm, more preferably 1000 to 1500 rpm. Moreover, although stirring time needs to be suitably adjusted according to the target specific gravity, it is about 2 to 5 minutes normally.

  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. The number of rotations of the stirring blade in the mixing step is preferably 1000 to 2000 rpm, and the stirring time is usually about 1 to 3 minutes. 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, a polyurethane foam block is produced by injecting the cell-dispersed urethane composition into the mold and curing the cell-dispersed urethane composition.

  In the method for producing a polyurethane foam block, heating and post-curing the foam that has reacted until the cell-dispersed urethane composition flows into the mold and does not flow has the effect of improving the physical properties of the foam. Is very suitable. The temperature of the post cure is usually about 40 to 70 ° C. The foam-dispersed urethane composition may be poured into a mold and immediately placed in a heating oven for post cure. The curing reaction is preferably performed at normal pressure because the bubble shape is stable.

  According to the production method of the present invention, even if the thickness of the polyurethane foam block is 30 mm or more, and even 50 mm or more, the thermal expansion of bubbles inside the block can be effectively prevented by the effect of the heat storage agent. Therefore, a polyurethane foam sheet having fine and uniform cells can be obtained.

  Thereafter, the polyurethane foam block is cut to a predetermined thickness using a band saw type or canna type slicer to produce a polyurethane foam sheet (polishing layer).

  The thickness variation of the polyurethane foam sheet is preferably 100 μm or less. When the thickness variation exceeds 100 μm, the polishing layer has a large waviness, and there are portions where the contact state with the material to be polished is different, which adversely affects the polishing characteristics. In order to eliminate the thickness variation of the polishing layer, in general, the surface of the polishing layer is dressed with a dresser in which diamond abrasive grains are electrodeposited and fused in the initial stage of polishing. As a result, the dressing time becomes longer and the production efficiency is lowered.

  Examples of the method for suppressing the variation in the thickness of the polyurethane foam sheet include a method of buffing the sheet surface sliced to a predetermined thickness. Moreover, when buffing, it is preferable to carry out stepwise with abrasives having different particle sizes.

  The thickness of the polyurethane foam sheet is not particularly limited, but is usually about 0.8 to 4 mm, and preferably 1.5 to 2.5 mm.

  The average cell diameter of the polyurethane foam obtained by the production method of the present invention is about 100 to 300 μm, preferably 150 to 250 μm.

  The specific gravity of the polyurethane foam is preferably 0.3 to 0.8. When the specific gravity is less than 0.3, the durability of the polishing layer tends to decrease. On the other hand, when the ratio is larger than 0.8, the abrasive grain retention of bubbles is deteriorated, and the polishing rate tends to decrease.

  The hardness of the polyurethane foam is preferably 10 to 50 degrees with an Asker D hardness meter. When the Asker D hardness is less than 10 degrees, the durability of the polishing layer tends to decrease, or the surface smoothness of the polished material after polishing tends to deteriorate. On the other hand, when it is larger than 50 degrees, scratches are likely to occur on the surface of the material to be polished.

  The polishing surface of the polyurethane foam sheet (polishing layer) that comes into contact with the material to be polished preferably has an uneven 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 material to be polished due to adsorption with the material to be polished can be prevented. The concavo-convex structure is not particularly limited as long as it is a shape that holds and renews the slurry. 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, or pressing a resin with a press plate having a predetermined surface shape. Examples thereof include a method, a manufacturing method using photolithography, and a manufacturing method using laser light using a carbon dioxide gas laser.

  The polishing pad of the present invention may be obtained by bonding the polishing layer and the cushion layer.

  The cushion layer supplements the characteristics of the polishing layer. The cushion layer is necessary in order to achieve 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 layer. In the polishing pad of the present invention, the cushion layer is preferably softer than the polishing layer.

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

  As a means for bonding the polishing layer and the cushion layer, for example, a method in which the polishing layer and the cushion layer are sandwiched and pressed with a double-sided tape can be mentioned.

  The double-sided tape has a general configuration in which adhesive layers are provided on both sides of a substrate such as a nonwoven fabric or a film. In consideration of preventing the slurry from penetrating into the cushion layer, it is preferable to use a film for the substrate. Examples of the composition of the adhesive layer include rubber adhesives and acrylic adhesives. Considering the content of metal ions, an acrylic adhesive is preferable because the metal ion content is low. In addition, since the composition of the polishing layer and the cushion layer may be different, the composition of each adhesive layer of the double-sided tape can be made different so that the adhesive force of each layer can be optimized.

  The polishing pad of the present invention may be provided with a double-sided tape on the surface to be bonded to the platen. As the double-sided tape, a tape having a general configuration in which an adhesive layer is provided on both surfaces of a base material can be used as described above. As a base material, a nonwoven fabric, a film, etc. are mentioned, for example. In consideration of peeling from the platen after use of the polishing pad, it is preferable to use a film for the substrate. Examples of the composition of the adhesive layer include rubber adhesives and acrylic adhesives. Considering the content of metal ions, an acrylic adhesive is preferable because the metal ion content is low.

  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 a polishing pad (polishing layer) 1 and a support table (polishing head) that supports the semiconductor wafer 4. 5 and a polishing apparatus equipped with a backing material for uniformly pressing the wafer and a supply mechanism of the abrasive 3. 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.

  As a result, the protruding portion of the surface of the semiconductor wafer 4 is removed and polished flat. 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.

  Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

[Measurement and evaluation methods]
(Measurement of average bubble diameter)
A sample obtained by cutting the produced polyurethane foam sheet in parallel with a microtome cutter as thin as possible to a thickness of 1 mm or less was used as a sample for measuring the average cell diameter. The sample was fixed on a slide glass 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. Moreover, the presence or absence of a 1 mm or more void was observed.

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

(D hardness measurement)
This was performed in accordance with JIS K6253-1997. The produced polyurethane foam sheet was cut into a size of 2 cm × 2 cm (thickness: arbitrary) and used as a sample for hardness measurement, and was 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 a thickness of 6 mm or more. The hardness was measured using a hardness meter (manufactured by Kobunshi Keiki Co., Ltd., Asker D type hardness meter).

(With or without bloom)
The surface of the produced polyurethane foam sheet was observed visually and by finger touch to confirm whether or not the heat storage agent was blooming on the surface.

(Measurement of micro swell)
Using a non-contact surface shape measuring machine (New View 6300, manufactured by ZYGO), setting the lens magnification 2.5 times, the zoom magnification 0.5 times, and the bandpass filter 200 to 1250 μm, the glass as the material to be polished Ra (nm) at 5 points on the surface of the plate was measured, and the average value was defined as a microwaviness. In addition, the 100th thing grind | polished with the following grinding | polishing method was used for the said glass plate.

(Evaluation of polishing rate stability)
Using a 9B double-side polishing machine (manufactured by Speed Fam Co., Ltd.) as the polishing apparatus, the polishing rate stability of the prepared polishing pad was evaluated. The evaluation results are shown in Table 1. The polishing conditions are as follows.
Glass plate: manufactured by OHARA, TS-10SX, 2.5 inches, thickness 0.8 mm
Slurry: Ceria slurry (SHOROX A-10, manufactured by Showa Denko KK) was added to water and mixed to adjust the specific gravity to 1.06 to 1.09. Slurry supply amount: 4 L / min
Polishing pressure: 100 g / cm ²
Polishing platen rotation speed: 50rpm
Polishing time: 60 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 (the average value of each polishing rate from the first to the 500th sheet) from the first to the 500th glass plate. Is calculated by substituting the value into the following equation. As the polishing rate stability (%) is lower, the polishing rate is less likely to change even when a large number of glass plates are polished. In the present invention, the polishing rate stability after processing 500 sheets is preferably within 10%.
Polishing rate stability (%) = {(maximum polishing rate−minimum polishing rate) / total average polishing rate} × 100

(Scratch evaluation)
Using VMX-2200 manufactured by MicroMax, observe whether there is a scratch or a scratch in the 4 × 5 mm range of the 100th glass plate polished by the above method. However, the case was evaluated as x.

Example 1
In a container, 65 parts by weight of polycaprolactone diol (Daicel Chemical Industries, Plaxel 210, hydroxyl value: 112 mgKOH / g, functional group number 2), polycaprolactone triol (Daicel Chemical Industries, Plaxel 305, hydroxyl value: 305 mgKOH / g) , Functional group number 3) 20 parts by weight, diethylene glycol (hydroxyl value: 1058 mgKOH / g, functional group number 2) 13 parts by weight, propylene oxide adduct of trimethylolpropane (Asahi Glass, EX-890MP, hydroxyl value: 865 mgKOH / g, functional Number of bases: 3) 2 parts by weight, silicon surfactant (manufactured by Goldschmidt, B8443) 6 parts by weight, catalyst (manufactured by Kao, Kao No. 25) 0.03 part by weight, and modified wax-based latent heat storage agent (Japan) Made by Seiwa Co., Ltd., NPS9210, hydroxyl group-containing type , Melting point: 75 ° C., heat of fusion: 150 kJ / kg, particle size: 5 μm) 30 parts by weight were added and mixed to prepare a second component. And it stirred vigorously for 5 minutes so that a bubble might be taken in in a reaction system with the rotation speed of 1500 rpm using the stirring blade. Thereafter, 82 parts by weight of carbodiimide-modified MDI (manufactured by Nippon Polyurethane Industry, Millionate MTL, NCO wt%: 29 wt%) as the first component was added to the container (NCO / OH = 1.1), and the bubbles were dispersed by stirring for 3 minutes. A urethane composition was prepared.

  The prepared cell-dispersed urethane composition was poured into a pan-type open mold (length 1000 mm, width 1000 mm, depth 50 mm). When the fluidity of the composition disappeared, it was put in an oven and post-cured at 70 ° C. for 16 hours to obtain a polyurethane foam block (thickness 30 mm). The polyurethane foam block heated to about 80 ° C. was sliced using a slicer (AGW Tech, VGW-125) to obtain a polyurethane foam sheet. Next, using a buffing machine (Amitech Co., Ltd.), the surface of the sheet was buffed to a thickness of 1.20 mm to obtain a sheet with an adjusted thickness accuracy. This buffed sheet is punched out with a diameter of 61 cm, and an XY grid-like groove with a groove width of 2 mm, a groove pitch of 50 mm, and a groove depth of 0.5 mm is formed on the surface using a groove processing machine (manufactured by Techno). A polishing layer was obtained. Using a laminator on the surface of the polishing layer opposite to the grooved surface, a double-sided tape (manufactured by Sekisui Chemical Co., Ltd., double tack tape) was bonded to prepare a polishing pad.

Examples 2-8 and Comparative Examples 1-6
A polishing pad was produced in the same manner as in Example 1 except that the blending ratios shown in Tables 1 and 2 were adopted. The compounds in Tables 1 and 2 are as follows.
PCL210: Polycaprolactone diol (manufactured by Daicel Chemical Industries, hydroxyl value: 112 mg KOH / g, number of functional groups 2)
PTMG1000: polytetramethylene ether glycol (manufactured by Mitsubishi Chemical Corporation, hydroxyl value: 112 mgKOH / g, number of functional groups: 2)
DEG: Diethylene glycol (hydroxyl value: 1058 mg KOH / g, number of functional groups 2)
1,4-BG: 1,4-butanediol (hydroxyl value: 1245 mg KOH / g, number of functional groups 2)
PCL305: Polycaprolactone triol (manufactured by Daicel Chemical Industries, hydroxyl value: 305 mgKOH / g, functional group number 3)
EX-890MP: Propylene oxide adduct of trimethylolpropane (manufactured by Asahi Glass, hydroxyl value: 865 mgKOH / g, number of functional groups: 3)
B8443: Silicon-based surfactant (manufactured by Goldschmidt)
・ Kao No. 25: Catalyst (manufactured by Kao)
NPS9210: Modified wax-based latent heat storage agent (Nippon Seiwa Co., Ltd., hydroxyl group-containing type, melting point: 75 ° C., heat of fusion: 150 kJ / kg, particle size: 5 μm)
NPS 6115: Modified wax-based latent heat storage agent (Nippon Seiwa Co., Ltd., urethane group-containing type, melting point: 80 ° C., heat of fusion: 150 kJ / kg, particle size: 5 μm)
HAD5150: Modified wax-based latent heat storage agent (Nippon Seiwa Co., Ltd., urethane group-containing type, melting point: 100 ° C., heat of fusion: 130 kJ / kg, particle size: 5 μm)
PW155: Paraffin-based latent heat storage agent (Nippon Seiwa Co., Ltd., no functional group, melting point: 70 ° C., heat of fusion: 200 kJ / kg, particle size: 5 μm)
FT0070: Paraffin-based latent heat storage agent (Nippon Seiwa Co., Ltd., no functional group, melting point: 70 ° C., heat of fusion: 220 kJ / kg, particle size: 5 μm)
Millionate MTL: Carbodiimide-modified MDI (Nippon Polyurethane Industry, NCO wt%: 29 wt%)

  The polishing pad of the present invention is used to flatten optical materials such as lenses and reflection mirrors, silicon wafers, glass substrates for hard disks, aluminum substrates, and materials that require high surface flatness such as general metal polishing. Used for processing. The polishing pad of the present invention is particularly suitable for a step of planarizing a silicon wafer and a device having an oxide layer, a metal layer, etc. formed thereon, before further laminating and forming these oxide layers and metal layers. Used for.

1: Polishing pad 2: Polishing surface plate 3: Abrasive (slurry)
4: Material to be polished (semiconductor wafer)
5: Support base (polishing head)
6, 7: Rotating shaft

Claims (4)

A step of preparing a cell-dispersed urethane composition containing an isocyanate compound, an active hydrogen-containing compound, and a silicon surfactant by a mechanical foaming method, a step of injecting a cell-dispersed urethane composition into a mold, and a cell-dispersed urethane composition In a method for producing a polishing pad comprising a step of producing a thermosetting polyurethane foam block by curing, and a step of producing a thermosetting polyurethane foam sheet by cutting the thermosetting polyurethane foam block,
The active hydrogen-containing compound has an average hydroxyl value of 260 to 400 mgKOH / g,
The cell-dispersed urethane composition contains a heat storage agent having a melting point of 70 to 110 ° C. and a hydroxyl group or a urethane group in an amount of 10 to 40 parts by weight with respect to 100 parts by weight of the active hydrogen-containing compound. Production method. The method for producing a polishing pad according to claim 1, wherein the heat storage agent is a modified wax-based latent heat storage agent having a heat of fusion of 100 kJ / kg or more. A polishing pad obtained by the production method according to claim 1. 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 3.

Images