JP2011235419A - Method of manufacturing polishing pad - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a polishing pad having good quality with good manufacturing efficiency even if a low-reactive active-hydrogen-containing compound is used.SOLUTION: In a method of manufacturing the polishing pad containing a bubble dispersed urethane composition, the active-hydrogen-containing compound contains 6-40 wt.% of secondary low-molecular-weight polyol, and the bubble dispersed urethane composition contains 10-50 pts.wt. of a thermal storage medium with a fusing point of 70-90°C and including hydroxyl groups or urethane groups for 100 pts.wt. of the active-hydrogen-containing compound and 0.1-1 pts.wt. of a thermosensitive catalyst having an activation temperature higher than the fusing point of the thermal storage medium for 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.

  The step of preparing a cell-dispersed urethane composition by a mechanical foaming method, the step of applying a cell-dispersed urethane composition on a base material layer, and curing the cell-dispersed urethane composition to form a polyurethane foam layer having substantially spherical open cells And a polishing pad manufacturing method including a step of uniformly adjusting the thickness of the polyurethane foam layer has been proposed (Patent Document 1).

  In the case of a method for producing a polyurethane foam sheet using a cell-dispersed urethane composition containing an isocyanate compound and an active hydrogen-containing compound (so-called one-shot method), the reaction temperature tends to rise and the urethanization reaction proceeds rapidly. Therefore, gelation of the cell-dispersed urethane composition is likely to occur before application. Therefore, there was a problem that the pot life could not be sufficiently secured, and the cell-dispersed urethane composition could not be uniformly applied on the release sheet or the like.

  Further, when an active hydrogen-containing compound with low reactivity is used, the time until the polyurethane foam is completely cured (tack-free time) becomes long. When the polyurethane foam sheet is continuously produced, the long polyurethane foam sheet cannot be cut unless it is in a tack-free state (non-adhesive state). Therefore, the productivity of the polyurethane foam sheet is lowered, or the production line has to be lengthened in order to hold the polyurethane foam sheet until the tack-free state is reached.

  On the other hand, in Patent Document 2, in order to produce a high-magnification foam having a smooth surface with uniform and fine bubbles, a thermoplastic resin is melted in an extruder, and an inorganic gas is injected into the melt. A water-absorbing polymer in which 0.3 to 80% by weight of water is absorbed 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 an extruder and foamed. The manufacturing method of the thermoplastic resin foam characterized by this is proposed.

In addition, Patent Document 3 discloses that in order to prevent the foam quality from being deteriorated by overheating of a part of the mixture during the foaming process and to produce a high-quality polymer foam, at least 80 ° C. in the foamable mixture. The addition of compounds that can endothermically decompose at temperature is described.

  When a compound that absorbs heat is added to the raw material composition as in Patent Documents 2 and 3, the thermal expansion of bubbles can be prevented, but the curing time until the foam is completely cured becomes longer. There is a problem.

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. In the invention of Patent Document 4, heat storage particles are blended with polyurethane foam to prevent bedding and clothing from being stored and steamed, and heat storage particles are blended to adjust pot life during production. I don't mean.

JP 2008-284675 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 high-quality polishing pad with high production efficiency even when an active hydrogen-containing compound having low reactivity is used, and a polishing pad obtained by the production method. To do. 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 provides a process for preparing a cell-dispersed urethane composition containing an isocyanate compound, an active hydrogen-containing compound, and a silicon surfactant by a mechanical foaming method, on a release sheet, a base material layer, or a cushion layer. Including a step of applying a cell-dispersed urethane composition, a step of curing the cell-dispersed urethane composition to form a thermosetting polyurethane foam sheet, and a step of uniformly adjusting the thickness of the thermosetting polyurethane foam sheet. In the manufacturing method of the polishing pad,
The active hydrogen-containing compound contains 6 to 40% by weight of a secondary low molecular weight polyol,
The cell-dispersed urethane composition comprises a heat storage agent having a melting point of 70 to 90 ° C. and a hydroxyl group or a urethane group of 10 to 50 parts by weight with respect to 100 parts by weight of the active hydrogen-containing compound, and an activation temperature of the heat storage agent. It is related with the manufacturing method of the polishing pad characterized by containing 0.1-1 weight part of temperature sensitive catalysts higher than a melting point with respect to 100 weight part of active hydrogen containing compounds.

Another aspect of the present invention is 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 on a release sheet. The step of applying, the step of laminating the release sheet, the base material layer, or the cushion layer on the applied cell-dispersed urethane composition, the thermosetting by curing the cell-dispersed urethane composition while making the thickness uniform by pressing means In a method for producing a polishing pad comprising a step of forming a polyurethane foam sheet, and a step of peeling the release sheet from the thermosetting polyurethane foam sheet,
The active hydrogen-containing compound contains 6 to 40% by weight of a secondary low molecular weight polyol,
The cell-dispersed urethane composition comprises a heat storage agent having a melting point of 70 to 90 ° C. and a hydroxyl group or a urethane group of 10 to 50 parts by weight with respect to 100 parts by weight of the active hydrogen-containing compound, and an activation temperature of the heat storage agent. It is related with the manufacturing method of the polishing pad characterized by containing 0.1-1 weight part of temperature sensitive catalysts higher than a melting point with respect to 100 weight part of active hydrogen containing compounds.

  In the case of a method for producing a polyurethane foam sheet using a cell-dispersed urethane composition containing an isocyanate compound and an active hydrogen-containing compound (so-called one-shot method), the reaction temperature tends to rise and the urethanization reaction proceeds rapidly. Therefore, gelation of the cell-dispersed urethane composition is likely to occur before application. Therefore, the pot life cannot be sufficiently secured, and it is difficult to uniformly apply the cell-dispersed urethane composition on the release sheet or the like. As in the present invention, by adding a heat storage agent having a melting point of 70 to 90 ° C. and a hydroxyl group or a urethane group to the cell-dispersed urethane composition, it is possible to suppress an increase in the reaction temperature. The gelation of the cell-dispersed urethane composition before coating can be effectively prevented. Therefore, the pot life can be sufficiently secured, and the cell-dispersed urethane composition can be uniformly applied on a release sheet or the like.

  In the present invention, it is necessary to use a heat storage agent having a melting point of 70 to 90 ° C. and having a hydroxyl group or a urethane group. When the melting point is less than 70 ° C., the melting point becomes lower than the urethane reaction temperature, and therefore the urethane reaction does not proceed smoothly, thereby undesirably increasing the pot life. On the other hand, when the melting point exceeds 90 ° C., the melting point is too high to absorb the heat generated by the urethanization reaction, and it is possible to prevent gelation of the cell-dispersed urethane composition before coating. Can not.

  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. . Moreover, when the thermal storage agent which has a hydroxyl group or a urethane group is used, since the dispersibility in a cell dispersion | distribution urethane composition improves, it becomes easy to prevent gelatinization in the whole composition. As a result, high-quality polyurethane foam sheets can be continuously produced with high productivity.

  It is necessary to add 10 to 50 parts by weight of the heat storage agent with respect to 100 parts by weight of the active hydrogen-containing compound. When the amount of the heat storage agent added is less than 10 parts by weight, the heat generated by the urethanization reaction cannot be sufficiently absorbed, and thus the gelation of the cell dispersed urethane composition before application cannot be prevented. On the other hand, when the amount exceeds 50 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.

  Moreover, in this invention, it is necessary to use the temperature sensitive catalyst whose activation temperature is higher than the melting point of the said thermal storage agent with the said thermal storage agent. When an active hydrogen-containing compound containing 6% by weight or more of a low-reactivity secondary low molecular weight polyol is used, the time until the polyurethane foam is completely cured (tack-free time) becomes long. In addition, when the heat storage agent is added to the cell-dispersed urethane composition, the heat applied during the primary curing is absorbed by the heat storage agent, and the tack-free time becomes longer. When the polyurethane foam sheet is continuously produced, the long polyurethane foam sheet cannot be cut unless it is in a tack-free state (non-adhesive state). For this reason, the productivity of the polyurethane foam sheet is lowered, or the production line must be lengthened to hold the polyurethane foam sheet until the tack-free state is reached, resulting in a problem that the equipment cost is increased. As in the present invention, in the cell-dispersed urethane composition, a temperature-sensitive catalyst having an activation temperature higher than the melting point of the heat storage agent is added and heated to the activation temperature of the temperature-sensitive catalyst during the primary curing. By doing so, the temperature sensitive catalyst is activated and the polyurethane foam can be rapidly cured. Therefore, a polyurethane foam sheet can be produced with high production efficiency, and there is no need to lengthen the production line. Moreover, since the tack free time can be shortened, it is possible to prevent the bubbles in the sheet from being combined and the bubbles from becoming coarse. However, when an active hydrogen-containing compound containing 40% by weight or more of a secondary low molecular weight polyol is used, the polyurethane foam becomes very brittle and cannot be used as a polishing pad.

  The temperature-sensitive catalyst needs to be added in an amount of 0.1 to 1 part by weight with respect to 100 parts by weight of the active hydrogen-containing compound. When the addition amount of the temperature-sensitive catalyst is less than 0.1 parts by weight, the polyurethane foam cannot be rapidly cured during the primary curing. On the other hand, when it exceeds 1 part by weight, the pot life becomes too short, and it becomes difficult to mold the polyurethane foam sheet.

The active hydrogen-containing compound preferably has an average hydroxyl value of less than 350 mgKOH / g. The production method of the present invention is particularly effective when an active hydrogen-containing compound having a relatively low reactivity is used.

  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. Also, 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 sheet. Therefore, it is preferable to use a modified wax-based heat storage agent.

  The temperature sensitive catalyst preferably has an activation temperature of 80 to 110 ° C. The temperature at the time of mixing an isocyanate compound and an active hydrogen containing compound is normally set to about 40-50 degreeC. When the mixed solution is mechanically stirred for 2 to 3 minutes, the temperature of the mixed solution usually rises to about 70 ° C. In order not to activate the temperature-sensitive catalyst when the temperature of the cell dispersed urethane composition is about 70 ° C, the activation temperature of the temperature-sensitive catalyst is preferably 80 ° C or higher. Also, if the activation temperature of the temperature-sensitive catalyst is low, the temperature-sensitive catalyst is activated when preparing the cell-dispersed urethane composition, and the urethanization reaction proceeds rapidly. The composition is easily gelled. On the other hand, when the activation temperature of the temperature-sensitive catalyst exceeds 110 ° C., the urethane curing reaction does not proceed smoothly, so that the bubbles are bonded together and the bubbles are coarsened, or the physical properties of the resulting polyurethane foam vary. Tend to occur.

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.

  According to the production method of the present invention, even when an active hydrogen-containing compound having low reactivity is used, a high-quality polishing pad can be produced with high production efficiency.

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, a release sheet, a base material layer, or It includes a step of applying a cell-dispersed urethane composition on the cushion layer, a step of curing the cell-dispersed urethane composition to form a polyurethane foam sheet, and a step of uniformly adjusting the thickness of the polyurethane foam sheet.

  Another method for producing a polishing pad of the present invention is 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, and cell-dispersing on a release sheet The step of applying the urethane composition, the step of laminating the release sheet, the base material layer, or the cushion layer on the applied cell-dispersed urethane composition, and curing the cell-dispersed urethane composition while making the thickness uniform by pressing means Forming a polyurethane foam sheet and peeling the release sheet from the polyurethane foam sheet.

  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 polishing pad production method of the present invention is effective when the active hydrogen-containing compound contains 6 to 40% by weight of a secondary low molecular weight polyol, and further when the average hydroxyl value of the active hydrogen-containing compound is less than 350 mgKOH / g. And adjusting each component so that the content of secondary low molecular weight polyol is 6 to 40% by weight and the average hydroxyl value of the active hydrogen-containing compound is less than 350 mgKOH / g. is required.

  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.

  In the present invention, it is necessary to use a secondary low molecular weight polyol. Examples of the secondary low molecular weight polyol include 1,2-propylene glycol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, glycerin, 1,2,6-hexanetriol, Examples include a propylene oxide adduct of trimethylolpropane, methyl glucoside, sorbitol, mannitol, dulcitol, and sucrose.

  In the present invention, the active hydrogen-containing compound needs to contain 6 to 40% by weight of a secondary low molecular weight polyol, preferably 15 to 30% by weight.

  Along with high molecular weight polyol and secondary low molecular weight polyol, ethylene glycol, 1,3-propylene glycol, 1,4-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, pentaerythritol, tetramethylolcyclohexane, 2,2,6,6-tetrakis (hydroxy) Low molecular weight polyols such as methyl) cyclohexanol, diethanolamine, N-methyldiethanolamine, and triethanolamine can 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.

  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 sheet is produced by a one-shot method.

  The cell-dispersed urethane composition is prepared 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.

  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 in at least one of a first component containing an isocyanate compound and a second component containing an active hydrogen-containing compound, a heat storage agent having a melting point of 70 to 90 ° C. and having a hydroxyl group or a urethane group, and activity Add a temperature-sensitive catalyst whose crystallization temperature is higher than the melting point of the heat storage agent, mechanically stir the component with the silicon surfactant added in the presence of the non-reactive gas, and turn the non-reactive gas into fine bubbles Disperse into 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 in at least one of the first component containing an isocyanate compound and the second component containing an active hydrogen-containing compound, a heat storage agent having a melting point of 70 to 90 ° C. and having a hydroxyl group or a urethane group, and activity A temperature-sensitive catalyst having a higher temperature than the melting point of the heat storage agent is added, 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 90 ° 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 moisture is vaporized at the time of melting and voids are easily generated in the polyurethane foam sheet. The melting point is preferably 75 to 85 ° C. Also, the hydrate type heat storage agent is not preferable because moisture is vaporized at the time of melting and voids are easily generated in the polyurethane foam. 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 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), a melting point of 80 ° C. and a urethane group. Modified wax-based latent heat storage agent (manufactured by Nippon Seiwa Co., Ltd., NPS 6115, heat of fusion: 150 kJ / kg) and the like.

  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 50 parts by weight, preferably 20 to 40 parts by weight, based on 100 parts by weight of the active hydrogen-containing compound.

  The temperature-sensitive catalyst is not particularly limited as long as the activation temperature is higher than the melting point of the heat storage agent, but it is preferable to use a non-metallic temperature-sensitive catalyst. Moreover, it is preferable that the activation temperature of a thermosensitive catalyst is 80-110 degreeC, More preferably, it is 90-110 degreeC.

  Examples of the temperature-sensitive catalyst having the above characteristics include amine-based temperature-sensitive catalysts (manufactured by Tosoh Corporation, TOYOCAT-DB60, activation temperature 90 to 110 ° C.).

  The temperature-sensitive catalyst needs to be added in an amount of 0.1 to 1 part by weight, preferably 0.4 to 0.8 part 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.

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

  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 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.

  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.

  Examples of the method for applying the cell-dispersed urethane composition on the release sheet include roll coaters such as gravure, kiss, and comma, die coaters such as slots and phantoms, squeeze coaters, and curtain coaters. Any method can be used as long as a uniform coating film can be formed.

  After the cell-dispersed urethane composition is applied on a release sheet or the like, the polyurethane foam sheet is cured until it is primarily cured and tack-free. The temperature of the primary curing needs to be higher than the activation temperature of the temperature-sensitive catalyst to be used, and is usually about 80 to 120 ° C. The primary curing time is not particularly limited, but is preferably about 15 to 30 minutes when the line speed is 1 m / min.

  Thereafter, the long polyurethane foam sheet is cut, and when a release sheet is used, it is peeled off.

  Secondary curing of the cut polyurethane foam sheet has the effect of improving the physical properties of the polyurethane foam and is extremely suitable. Secondary curing is usually preferably performed at 70 to 100 ° C. for 2 to 6 hours.

  The average cell diameter of the polyurethane foam sheet is preferably 35 to 200 μm, more preferably 40 to 100 μm. The polyurethane foam sheet may have a closed cell structure or an open cell structure.

  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 specific gravity of the polyurethane foam sheet is preferably 0.2 to 0.6. 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 polyurethane foam is preferably 20 to 95 degrees, more preferably 40 to 90 degrees as measured by an Asker C hardness meter. When the Asker C hardness is less than 20 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, if it is greater than 95 degrees, scratches are likely to occur on the surface of the material to be polished.

  Although the thickness in particular of a polyurethane foam sheet is not restrict | limited, Usually, it is about 0.2-2 mm, and it is preferable that it is 0.5-1.5 mm.

  The shape of the polyurethane foam sheet is not particularly limited, and may be a long shape having a length of about 5 to 10 m or a circular shape having a diameter of about 50 to 150 cm.

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

  The pressing means for making the thickness of the sandwich sheet consisting of the release sheet, the cell-dispersed urethane composition (cell-dispersed urethane layer), the mold release sheet, the base material layer, or the mold release sheet is not particularly limited, For example, the method of compressing by fixed thickness with a coater roll, a nip roll, etc. is mentioned.

  Other manufacturing methods and the structure and physical properties of the resulting polyurethane foam sheet are the same as described above.

  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 only the polishing layer, the polishing layer and the base material layer may be integrally formed, or the polishing layer and the cushion layer may be integrally formed. Alternatively, the polishing layer and the cushion layer may be bonded together.

  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]
(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.

(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).

(C hardness)
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 C-type hardness meter).

(Pot life)
The prepared cell-dispersed urethane composition was poured into a 5 mm-thick mold, and the time required until fluidity was lost was defined as the pot life. The pot life is preferably 4 minutes or longer.

(Tack free time)
When a polyurethane foam sheet molded to a thickness of 1.2 mm was cured at 90 ° C., the time required for tack to completely disappear from the sheet surface was defined as tack-free time. The tack free time is preferably within 30 minutes.

Example 1
In a container, polycaprolactone diol (Daicel Chemical Industries, Plaxel 210, hydroxyl value: 112 mgKOH / g, functional group number 2) 65 parts by weight, 1,4-butanediol (hydroxyl value: 1245 mgKOH / g, functional group number 2) 15 Part by weight, propylene oxide adduct of trimethylolpropane, which is a secondary low molecular weight polyol (Asahi Glass, EX-400MP, hydroxyl value: 410 mgKOH / g, functional group number: 3), 20 parts by weight, silicon-based surfactant (gold) Schmidt, B8443) 6 parts by weight, modified wax-based latent heat storage agent (Nippon 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 , And amine-based temperature-sensitive catalyst (Tosoh Corporation, TOYOCAT-DB60, activation temperature 0 to 110 ° C.) were placed 0.5 part by weight, the second component was prepared by mixing. And it stirred violently for 3 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, 96.1 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 stirred for 2 minutes. A cell dispersed urethane composition was prepared.

  The prepared cell-dispersed urethane composition was continuously applied onto a release-treated release sheet (Toyobo, polyethylene terephthalate, thickness: 0.1 mm) to form a cell-dispersed urethane layer. And the base material layer (polyethylene terephthalate, thickness: 0.2 mm) was covered on this cell dispersion | distribution urethane layer. Thereafter, the cell-dispersed urethane layer was made 1.2 mm thick with a nip roll, and further subjected to primary curing at 90 ° C. for 30 minutes to form a long polyurethane foam sheet. Thereafter, the long polyurethane foam sheet was cut, and the release sheet was peeled off from the cut polyurethane foam sheet, followed by secondary curing at 90 ° C. for 3 hours. 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. 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 2-12 and Comparative Examples 1-4
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. In Comparative Examples 2 and 4, gelation occurred when the cell-dispersed urethane composition was applied on the release sheet.
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)
PTMG2000: polytetramethylene ether glycol (Mitsubishi Chemical Corporation, hydroxyl value:
56 mg KOH / g, number of functional groups: 2)
1,2-PG: 1,2-propylene glycol (hydroxyl value: 1472 mgKOH / g, number of functional groups 2)
DEG: Diethylene glycol (hydroxyl value: 1057 mg KOH / g, functional group number 2)
1,4-BG: 1,4-butanediol (hydroxyl value: 1245 mg KOH / g, number of functional groups 2)
EX-400MP: Propylene oxide adduct of trimethylolpropane (Asahi Glass, hydroxyl value: 410 mgKOH / g, functional group number: 3)
T400: propylene oxide adduct of glycerin (Mitsui Chemicals, hydroxyl value: 415 mgKOH / g, functional group number: 3)
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)
TOYOCAT-DB60: amine-based temperature-sensitive catalyst (manufactured by Tosoh Corporation, activation temperature 90 to 110 ° C.)
・ 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)
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 (7)

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 cell-dispersed urethane composition on a release sheet, a base material layer, or a cushion layer In a method for producing a polishing pad comprising a step of applying, a step of curing a cell-dispersed urethane composition to form a thermosetting polyurethane foam sheet, and a step of uniformly adjusting the thickness of the thermosetting polyurethane foam sheet ,
The active hydrogen-containing compound contains 6 to 40% by weight of a secondary low molecular weight polyol,
The cell-dispersed urethane composition comprises a heat storage agent having a melting point of 70 to 90 ° C. and a hydroxyl group or a urethane group of 10 to 50 parts by weight with respect to 100 parts by weight of the active hydrogen-containing compound, and an activation temperature of the heat storage agent. A method for producing a polishing pad, comprising 0.1 to 1 part by weight of a temperature-sensitive catalyst higher than the melting point with respect to 100 parts by weight of an active hydrogen-containing compound. 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 applying a cell-dispersed urethane composition on a release sheet, and a coated cell dispersion A step of laminating a release sheet, a base material layer, or a cushion layer on the urethane composition, a step of forming a thermosetting polyurethane foam sheet by curing the cell dispersed urethane composition while making the thickness uniform by pressing means In the manufacturing method of the polishing pad including the step of peeling the release sheet from the thermosetting polyurethane foam sheet,
The active hydrogen-containing compound contains 6 to 40% by weight of a secondary low molecular weight polyol,
The cell-dispersed urethane composition comprises a heat storage agent having a melting point of 70 to 90 ° C. and a hydroxyl group or a urethane group of 10 to 50 parts by weight with respect to 100 parts by weight of the active hydrogen-containing compound, and an activation temperature of the heat storage agent. A method for producing a polishing pad, comprising 0.1 to 1 part by weight of a temperature-sensitive catalyst higher than the melting point with respect to 100 parts by weight of an active hydrogen-containing compound. The method for producing a polishing pad according to claim 1, wherein the active hydrogen-containing compound has an average hydroxyl value of less than 350 mg KOH / g. The method for producing a polishing pad according to any one of claims 1 to 3, 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. The method for producing a polishing pad according to any one of claims 1 to 4, wherein the temperature-sensitive catalyst has an activation temperature of 80 to 110 ° C. The polishing pad obtained by the manufacturing method in any one of Claims 1-5. 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 6.

Images