JP5411862B2 - Polishing pad and polishing pad manufacturing method - Google Patents

Description

  The present invention is a polishing pad, more specifically, various devices such as various devices that are flattened or mirrored, various substrates, such as semiconductor substrates, semiconductor devices, compound semiconductor devices, compound semiconductor substrates, compound semiconductor products, LED substrates, The present invention relates to a polishing pad for polishing LED products, bare silicon wafers, silicon wafers, hard disk substrates, glass substrates, glass products, metal substrates, metal products, plastic substrates, plastic products, ceramic substrates, ceramic products, and the like, and a method for manufacturing the same.

  In recent years, with high integration of integrated circuits and multilayer wiring, semiconductor wafers on which integrated circuits are formed are required to have high precision flatness.

  As a polishing method for polishing a semiconductor wafer, chemical mechanical polishing (CMP) is known. CMP is a method of polishing a surface of a substrate to be polished with a polishing pad while dropping slurry of abrasive grains.

  The following Patent Documents 1 to 4 disclose a polishing pad used for CMP, which is made by foam-molding a two-component curable polyurethane and made of a polymer foam having a closed cell structure. Such a polishing pad is preferably used for polishing a semiconductor wafer that requires high-precision flatness because it has higher rigidity than a non-woven fabric type polishing pad described later.

  A polishing pad made of a polymer foam having a closed cell structure is produced, for example, by casting and molding a two-component curable polyurethane. Since such a polishing pad has a relatively high rigidity, a load is easily applied selectively to the convex portion of the substrate to be polished during polishing, and as a result, the polishing rate (polishing rate) is relatively high. Become. However, when agglomerated abrasive grains are present on the polished surface, a load is selectively applied to the agglomerated abrasive grains, so that the polished surface is easily scratched. In particular, as described in Non-Patent Document 1, scratches and interfacial delamination occur particularly when polishing a substrate having a copper wiring that is easily scratched or a low dielectric constant material having weak interface adhesion. It becomes easy to do. In cast foam molding, since it is difficult to uniformly foam a polymer elastic body, the flatness of the substrate to be polished and the polishing rate at the time of polishing tend to vary. Furthermore, in the polishing pad having independent holes, abrasive grains and polishing debris are clogged in the voids originating from the independent holes. As a result, when used for a long time, the polishing rate decreases as polishing progresses (this characteristic is also referred to as polishing stability).

  On the other hand, as another type of polishing pad, Patent Documents 5 to 14 disclose a nonwoven fabric type polishing pad obtained by impregnating a polyurethane resin with a nonwoven fabric and wet coagulating it. Nonwoven polishing pads are excellent in flexibility. Therefore, when there are aggregated abrasive grains on the polishing surface of the substrate to be polished, the polishing pad is deformed to suppress a load from being selectively applied to the aggregated abrasive grains. However, the non-woven polishing pad tends to change its polishing characteristics with time, and has a problem that it is difficult to use for precise planarization. In addition, since the polishing pad is too flexible and deforms following the surface shape of the substrate to be polished, high flattening performance (characteristic for flattening the substrate to be polished) is difficult to obtain, and the fineness is 2 to 2. Since it is as large as 10 dtex, there is a problem that local stress concentration cannot be avoided.

  In such a nonwoven fabric type polishing pad, in recent years, a nonwoven fabric type polishing pad obtained by using a nonwoven fabric formed from an ultrafine fiber bundle for the purpose of obtaining higher planarization performance is known ( For example, the following patent documents 15 to 18). Specifically, for example, Patent Document 15 includes, as a main component, a nonwoven fabric in which polyester microfiber bundles having an average fineness of 0.0001 to 0.01 dtex are entangled and polyurethane existing in the interior space of the nonwoven fabric. A polishing pad made of a sheet-like material composed of a polymer elastic body is described. According to such a polishing pad, it is described that polishing processing with higher accuracy than before can be realized.

  However, in the polishing pads described in Patent Documents 15 to 18, since the nonwoven fabric obtained by needle punching the ultrafine fibers having a small fineness is used, the apparent density is low and the porosity is low. It was also expensive. For this reason, only a soft and low-rigidity polishing pad can be obtained. For this reason, deformation is performed following the surface shape, so that high planarization performance cannot be sufficiently obtained.

  Further, in such a nonwoven fabric type polishing pad, the details of the polymer elastic body are not described in any literature, and the description of the stability over time is not sufficient.

JP 2000-178374 A JP 2000-248034 A JP 2001-89548 A Japanese Patent Laid-Open No. 11-322878 JP 2002-9026 A JP-A-11-99479 Japanese Patent Laying-Open No. 2005-212055 JP-A-3-234475 JP-A-10-128674 JP 2004-311731 A Japanese Patent Laid-Open No. 10-225864 JP-T-2005-518286 JP 2003-201676 A JP 2005-334997 A JP 2007-54910 A JP 2003-170347 A JP 2004-130395 A JP 2002-172555 A

Masahiro Kusunoki et al., “CMP Science”, Science Forum, Inc., August 20, 1997, p.113-119

  An object of this invention is to provide the polishing pad which is hard to generate | occur | produce a scratch and was excellent in planarization performance and polishing efficiency.

  One aspect of the present invention includes an ultrafine fiber entangled body formed from ultrafine fibers having an average fineness of 0.01 to 0.8 dtex, and a polymer elastic body, and the polymer elastic body has a glass transition temperature of −10. A polishing pad having a storage elastic modulus of 90 to 900 MPa at 23 ° C. and 50 ° C. and a water absorption of 0.2 to 5 mass% when saturated with water absorption at 50 ° C. It is.

  Objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description.

  In general, a substrate made of ultrafine fibers has characteristics of a large surface area and low flexural elasticity. Therefore, a polishing pad obtained by impregnating a conventionally known non-woven fabric made of ultrafine fibers with a polymer elastic body has a large contact area with the substrate to be polished and performs soft polishing. However, only those with low rigidity were obtained, and there were problems in planarization characteristics and polishing stability over time. In addition, the nonwoven fabric has been known for the past because the voids account for more than half of the apparent volume, although the voids serve as slurry reservoirs and the abrasive slurry slurry has high liquid retention properties, which makes it easy to increase the polishing rate. A polishing pad obtained by impregnating a non-woven fabric with a polymer elastic body can perform efficient polishing, but has a problem of low rigidity and flatness and polishing stability over time.

  The inventors have obtained 1) a polishing pad having high rigidity by using an ultrafine fiber entangled body made of ultrafine fibers and a polymer elastic body having a specific glass transition temperature, storage elastic modulus and water absorption, The structure is maintained even during polishing to improve the polishing stability over time. 2) On the surface of the polishing pad, the fibers are easily fibrillated during polishing, and the contact area with the substrate to be polished increases. Since the wettability increases, the retention of the abrasive slurry increases, and as a result, the polishing rate increases. 3) Since the surface of the polishing pad comes into soft contact with the ultrafine fibers, The inventors have found that stress concentration can be made difficult to occur, thereby making it difficult for scratches to be generated on the substrate to be polished. Furthermore, it has been found that by setting the porosity of the polishing pad to 50% or more, it is possible to improve the retention of the abrasive slurry and to have high rigidity, and it is particularly suitable for bare silicon wafer polishing.

  That is, the polishing pad according to this embodiment includes an ultrafine fiber entangled body formed from ultrafine fibers having an average fineness of 0.01 to 0.8 dtex, and a polymer elastic body, and the polymer elastic body is made of glass. The transition temperature is −10 ° C. or lower, the storage elastic modulus at 23 ° C. and 50 ° C. is 90 to 900 MPa, and the water absorption when saturated with water absorption at 50 ° C. is 0.2 to 5% by mass. It is a feature.

  Below, the structure of the polishing pad of this embodiment, a manufacturing method, and its usage are demonstrated.

[Configuration of polishing pad]
The ultrafine fiber entangled body is formed from ultrafine fibers having an average fineness of 0.01 to 0.8 dtex, and preferably in the range of 0.05 to 0.5 dtex. When the average fineness of the ultrafine fibers is less than 0.01 dtex, the ultrafine fiber bundle in the vicinity of the surface of the polishing pad is not sufficiently separated, and as a result, the holding power of the abrasive slurry is reduced, resulting in polishing efficiency and polishing. Uniformity tends to decrease. On the other hand, when the average fineness of the ultrafine fibers exceeds 0.8 dtex, the surface of the polishing pad becomes too rough, the polishing rate decreases, and the stress caused by the polishing by the fibers increases and scratches occur. It becomes easy.

  Moreover, it is preferable that the ultrafine fiber entangled body is composed of an ultrafine fiber bundle in which 5 to 70 ultrafine fibers are converged, and more preferably, 10 to 50. When the number of ultrafine fibers converging exceeds 70, the ultrafine fibers near the surface of the polishing pad are not sufficiently separated, and as a result, the holding power of the abrasive slurry is reduced. On the other hand, when the number of the ultrafine fiber bundles is less than 5, the fineness is substantially increased or the fiber density on the surface tends to decrease, the surface of the polishing pad becomes too rough, and the polishing rate decreases. The stress caused by polishing with fibers increases, and scratches are likely to occur.

  Specific examples of the ultrafine fibers include, for example, aromatic polyester fibers formed from polyethylene terephthalate (PET), isophthalic acid-modified polyethylene terephthalate, sulfoisophthalic acid-modified polyethylene terephthalate, polybutylene terephthalate, polyhexamethylene terephthalate, and the like; Aliphatic polyester fibers formed from polyethylene succinate, polybutylene succinate, polybutylene succinate adipate, polyhydroxybutyrate-polyhydroxyvalerate copolymer, etc .; polyamide 6, polyamide 66, polyamide 10, polyamide 11, polyamide 12, polyamide fiber formed from polyamide 6-12, etc .; polypropylene, polyethylene, polybutene, polymethylpentene, chlorinated polyolefin Polyolefin fibers such as tin; modified polyvinyl alcohol fibers formed from modified polyvinyl alcohol containing 25 to 70 mol% of ethylene units; and elastomers such as polyurethane elastomers, polyamide elastomers, polyester elastomers, etc. An elastomer fiber etc. are mentioned. These may be used alone or in combination of two or more. In particular, when the ultrafine fiber of this embodiment is formed from a polyester fiber, it is preferable because a dense and high-density fiber entangled body can be formed.

Among the ultrafine fibers, the glass transition temperature (T _g ) is 50 ° C. or higher, more preferably 60 ° C. or higher, and the water absorption when saturated with water absorption at 50 ° C. is 0.2 to 2% by mass. A fiber formed from a plastic resin is preferred. When the glass transition temperature of the thermoplastic resin is within such a range, higher rigidity can be maintained, so that the flattening performance is further improved. Thus, a polishing pad excellent in polishing stability and polishing uniformity can be obtained. The upper limit of the glass transition temperature is not particularly limited, but is preferably 300 ° C. or lower, and more preferably 150 ° C. or lower for industrial production.

  Moreover, it is preferable that the ultrafine fiber of this embodiment is formed from a thermoplastic resin having a water absorption rate of 0.2 to 2% by mass when water is saturated at 50 ° C. In other words, the ultrafine fiber is formed. The water absorption when the thermoplastic resin is saturated with water at 50 ° C. is preferably 0.2 to 2% by mass. By setting the water absorption to 0.2% by mass or more, the polishing slurry can be easily retained, and the polishing efficiency and the polishing uniformity are easily improved. In the case of 2% by mass or less, since the polishing pad does not absorb the abrasive slurry excessively, a decrease in rigidity with time is further suppressed. In such a case, it is possible to obtain a polishing pad that suppresses a decrease in flattening performance with time and is difficult to change in polishing rate and polishing uniformity. In addition to water absorption, the thermoplastic resin forming the ultrafine fibers of the present invention is a semi-fragrance that uses a polyester polymer, particularly an aromatic component as one component of the raw material because of its good availability and manufacturability. A group polyester-based polymer is preferred.

Specific examples of the thermoplastic resins include polyethylene terephthalate (PET, T g ₇₇ ℃, water absorption when imbibed saturated at 50 ° C. (hereinafter, simply referred to as water absorption.) 1 wt%), isophthalic acid-modified Polyethylene terephthalate (T _g 67 to 77 ° C., water absorption 1% by mass), sulfoisophthalic acid modified polyethylene terephthalate (T _g 67 to 77 ° C., water absorption 1 to 3% by mass), polybutylene naphthalate (T _g 85 ° C., water absorption 1 wt%), polyethylene naphthalate _(T g 124 ° C., water absorption 1 wt%) aromatic polyester fibers formed from such; terephthalic acid and nonanediol and methyl octanediol copolyamide _(T g 125 to And semi-aromatic polyamide fibers formed from 140 ° C., water absorption of 1 to 3% by mass) and the like. In particular, modified PET, such as PET and isophthalic acid-modified PET, is a dense and high-density fiber because it is crimped greatly in a wet heat treatment process for forming ultrafine fibers from a web-entangled sheet composed of sea-island type composite fibers described later. It is also preferable from the viewpoints that an entangled body can be formed, that the rigidity of the polishing sheet can be easily increased, and that a change with time due to moisture hardly occurs during polishing.

  The polishing pad according to the present embodiment preferably includes an ultrafine fiber entangled body formed from an ultrafine fiber bundle in which the ultrafine fibers are converged, and a polymer elastic body.

  Specific examples of the elastic polymer used in the present embodiment are not particularly limited as long as the glass transition temperature, storage elastic modulus, and water absorption described below are satisfied. For example, polyurethane resins and polyamide resins are used. , (Meth) acrylic ester resin, (meth) acrylic ester-styrene resin, (meth) acrylic ester-acrylonitrile resin, (meth) acrylic ester-olefin resin, (meth) acrylic ester -(Hydrogenated) isoprene-based resin, (meth) acrylic ester-butadiene-based resin, styrene-butadiene-based resin, styrene-hydrogenated isoprene-based resin, acrylonitrile-butadiene-based resin, acrylonitrile-butadiene-styrene-based resin, vinyl acetate Resin, (meth) acrylic acid ester-vinyl acetate resin Ethylene - vinyl acetate resin, ethylene - olefin resins, silicone resins, fluorine resins, and include an elastic body made of a polyester resin.

  As the polymer elastic body of the present embodiment, a hydrogen-bonding polymer elastic body is preferable from the viewpoints of converging properties with respect to ultrafine fibers and high binding property of the ultrafine fiber bundle. The resin that forms the hydrogen-bonding polymer elastic body is a polymer elastic body that crystallizes or aggregates by hydrogen bonding, such as a polyurethane-based resin, a polyamide-based resin, and a polyvinyl alcohol-based resin. The hydrogen-bonding polymer elastic body has high adhesiveness, enhances the binding property of the fiber bundle, and suppresses the fiber from coming off.

  The polymer elastic body used in the present embodiment has a glass transition temperature of −10 ° C. or lower. When the glass transition temperature is higher than −10 ° C., the polymer elastic body becomes brittle, and the polymer elastic body is easily dropped during polishing, and scratches are easily generated. In addition, the focusing force of the ultrafine fibers by the polymer elastic body becomes weak, and the stability over time during polishing tends to deteriorate. Preferably, the glass transition temperature is −15 ° C. or lower. Although it does not specifically limit about a minimum, About -100 degreeC or more is preferable from availability. The glass transition temperature is calculated from the peak temperature of the loss elastic modulus in the tensile mode in the dynamic viscoelasticity measurement. Since the glass transition temperature depends on the α dispersion peak temperature of the polymer elastic body, the components constituting the polymer elastic body are appropriately selected in order to make the glass transition temperature of the polymer elastic body -10 ° C. or lower. It is preferable to do. For example, when a polyurethane-based resin is used as the polymer elastic body, in order to set the glass transition temperature to −10 ° C. or lower, the composition of polyol as a soft component or a hard component (isocyanate component or chain extender component) And the ratio of soft ingredients. Specifically, a polyol having a glass transition temperature of −10 ° C. or lower, preferably −20 ° C. or lower is selected, and the mass ratio of the polyol component in the polyurethane is 30% by mass or more, preferably 40% by mass or more. It is preferable.

  Moreover, the polymer elastic body used in the present embodiment has a storage elastic modulus at 23 ° C. and 50 ° C. in the range of 90 to 900 MPa. The storage elastic modulus at 23 ° C. and 50 ° C. of general polyurethane is less than 90 MPa, but when the storage elastic modulus in the range of 23 ° C. and 50 ° C. is less than 90 MPa, the polymer elasticity restraining the fiber bundle The body is easily deformed and the pad rigidity in polishing is insufficient, and the flatness is lowered. Also, the polymer elastic body tends to swell with slurry during polishing, and the stability over time tends to decrease. When the storage elastic modulus in the range of 23 ° C. and 50 ° C. exceeds 900 MPa, the polymer elastic body becomes brittle and the polymer elastic body tends to fall off during polishing, and scratches are likely to occur. In addition, the focusing force of the ultrafine fibers is reduced, and the stability over time during polishing tends to deteriorate. The storage elastic modulus in the range of 23 ° C. and 50 ° C. is preferably 200 to 800 MPa. The storage elastic modulus of the polymer elastic body depends on the composition of the polymer elastic body, that is, the elastic modulus and the mass ratio of each of the hard component and the soft component constituting the polymer elastic body. For this purpose, it is preferable to select the composition of the hard component and the soft component and the mass ratio thereof.

  For example, when a polyurethane-based resin is used as the polymer elastic body, a polyether-based polyol such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, poly (methyltetramethylene glycol) is used as the soft component (polyol component). And copolymers thereof; polybutylene adipate diol, polybutylene sebacate diol, polyhexamethylene adipate diol, poly (3-methyl-1,5-pentylene adipate) diol, poly (3-methyl-1,5-penty Polyester polyols such as rensebacate) diol, isophthalic acid copolymer polyol, terephthalic acid copolymer polyol, cyclohexanol copolymer polyol, polycaprolactone diol, and copolymers thereof; poly Xamethylene carbonate diol, poly (3-methyl-1,5-pentylene carbonate) diol, polypentamethylene carbonate diol, polytetramethylene carbonate diol, poly (methyl-1.8-octamethylene carbonate) diol, polynonamethylene Polycarbonate polyols such as carbonate diol and polycyclohexane carbonate and their copolymers; polyester carbonate polyols and the like. If necessary, a trifunctional alcohol such as trimethylolpropane or a polyfunctional alcohol such as tetrafunctional alcohol such as pentaerythritol, or ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol. Etc. You may use together short chain alcohols, such as. These may be used alone or in combination of two or more. In particular, 60-100% by mass of the total amount of polyol components such as alicyclic polycarbonate-based polyol, linear polycarbonate-based polyol and branched polycarbonate-based polyol is included. Adding an amorphous polycarbonate-based polyol in an amount of 60 to 100% by mass of the total amount of the polyol component has high resistance to the slurry used in polishing, so that stability over time during polishing is good, and water absorption and storage The elastic modulus is preferable because it is easily within the range of the present embodiment.

  And in order to make the storage elastic modulus in the range of 23 degreeC and 50 degreeC into the range of 90-900 MPa, it is preferable to select the polyol whose glass transition temperature is -10 degrees C or less, Preferably it is -20 degrees C or less. For example, specifically, the above-mentioned branched polycarbonate-based polyols; polyether-based polyols such as polypropylene glycol, polytetramethylene glycol, poly (methyltetramethylene glycol) and their copolymers; polybutylene sebacate diol, poly Polyester polyols such as (3-methyl-1,5-pentylene adipate) diol, poly (3-methyl-1,5-pentylene sebacate) diol, polycaprolactone diol, and copolymers thereof; poly (3- Polycarbonate polyols such as methyl-1,5-pentylene carbonate) diol and poly (methyl-1.8-octamethylene carbonate) diol, and copolymers thereof; polyester carbonate polyol and the like. In addition to the above-described polyol, a polyol having a glass transition temperature of −10 ° C. or lower by copolymerization can also be exemplified.

  In addition, the polyurethane resin containing a polyalkylene glycol group having 5 or less carbon atoms, particularly 3 or less carbon atoms has a particularly good wettability with respect to water. It is also preferable to use a polyurethane resin containing about mass%.

  Using a soft component (polyol component) having a glass transition temperature of −10 ° C. or less, the glass transition temperature of the polyurethane is set to −10 ° C. or less, and such a polyol component is selected and the mass ratio of the polyol component in the polyurethane By adjusting the storage modulus, the storage elastic modulus of polyurethane at 23 ° C. and 50 ° C. can be set in the range of 90 to 900 MPa.

  When a polyurethane resin is used as the polymer elastic body, the isocyanate component is represented by hexamethylene diisocyanate, isophorone diisocyanate, norbornene diisocyanate, or 4,4′-dicyclohexylmethane diisocyanate in the hard component (isocyanate component or chain extender component). Non-yellowing diisocyanates of aliphatic or cycloaliphatic diisocyanates, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, aromatic diisocyanates represented by xylylene diisocyanate polyurethane Can be used. Moreover, you may use together polyfunctional isocyanates, such as trifunctional isocyanate and tetrafunctional isocyanate, as needed. These may be used alone or in combination of two or more. Among these, 4,4′-dicyclohexylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, and xylylene diisocyanate have high adhesion to ultrafine fibers. It is preferable from the viewpoint of improving the focusing force of ultrafine fibers and obtaining a polishing pad having high hardness.

  Examples of the chain extender component include diols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,4-bis (β-hydroxyethoxy) benzene, 1,4-cyclohexanediol; trimethylolpropane, etc. Triols of the following: pentaols such as pentaerythritol; short-chain polyols represented by amino alcohols such as aminoethyl alcohol and aminopropyl alcohol, hydrazine, ethylenediamine, propylenediamine, hexamethylenediamine, xylylenediamine, isophoronediamine, Typical examples include piperazine and its derivatives, diamines such as adipic acid dihydrazide and isofluric acid dihydrazide; triamines such as diethylenetriamine; and tetramines such as triethylenetetramine. High hard component cohesiveness of high elastic modulus comprising a combination of such short-chain polyamine may be selected to be. In addition, during the chain extension reaction, together with the chain extender, monoamines such as ethylamine, propylamine, and butylamine; carboxyl group-containing monoamine compounds such as 4-aminobutanoic acid and 6-aminohexanoic acid; methanol, ethanol, propanol, butanol, etc. Monools may be used in combination and contain carboxyl groups such as 2,2-bis (hydroxymethyl) propionic acid, 2,2-bis (hydroxymethyl) butanoic acid, 2,2-bis (hydroxymethyl) valeric acid The wettability with respect to water can be further improved by introducing an ionic group such as a carboxyl group into the skeleton of the polyurethane elastic body in combination with a diol.

  From the viewpoint of setting the storage elastic modulus of polyurethane at 23 ° C. and 50 ° C. in the range of 90 to 900 MPa, the ratio of the soft component (polyol component) is preferably 40 to 65% by mass, and 45 to 60% by mass. Is more preferable. When the amount of the soft component is less than 40% by mass, the temperature dependence of the storage elastic modulus in the range of 23 ° C. and 50 ° C. is high, and it is difficult to be in the range of 90 to 900 MPa. On the contrary, when the amount of the soft component exceeds 65% by mass, the storage elastic modulus tends to be less than 90 MPa.

  As a soft component, since it is easy to increase the storage elastic modulus of polyurethane, it is particularly a polycarbonate polyol having a branch; poly (3-methyl-1,5-pentylene carbonate) diol, poly (methyl-1.8-octamethylene carbonate) ) Diol or poly (3-methyl-1,5-pentylene carbonate) diol, poly (methyl-1.8-octamethylene carbonate) diol, polyhexamethylene carbonate diol, polypentamethylene carbonate diol, polytetramethylene Polycarbonate polyols typified by polycarbonate polyols that copolymerize polycarbonate polyols such as carbonate diol, polynonanemethylene carbonate diol, and polycyclohexane carbonate are preferred. There.

  Further, the polymer elastic body of the present embodiment preferably has a ratio of storage elastic modulus at 23 ° C. to storage elastic modulus at 50 ° C. (storage elastic modulus at 23 ° C./storage elastic modulus at 50 ° C.) of 4 or less. By setting the ratio of the storage elastic modulus at 23 ° C. to the storage elastic modulus at 50 ° C. (storage elastic modulus at 23 ° C./storage elastic modulus at 50 ° C.) to 4 or less, the storage elasticity even when a temperature change during polishing occurs. Since the rate hardly changes, the stability over time during polishing is improved. In particular, the ratio of the storage elastic modulus at 23 ° C. to the storage elastic modulus at 50 ° C. (storage elastic modulus at 23 ° C./storage elastic modulus at 50 ° C.) is preferably 3 or less. Further, the lower limit is not particularly limited, but is preferably 1/3 or more from the viewpoint that a change in storage elastic modulus due to temperature during polishing hardly occurs.

  The above range can be achieved by appropriately adjusting the soft component and the hard component for achieving the above storage elastic modulus range.

  For example, when a polyurethane-based resin is used as the polymer elastic body, a soft component (polyol component) having a glass transition temperature of −10 ° C. or lower is used to set the glass transition temperature of polyurethane to −10 ° C., and a hard component (isocyanate) Ingredients and chain extender components) include alicyclic diisocyanates and aromatic diisocyanates, short chain polyols typified by diols, triols and pentaols, diamines, triamines and short amines typified by tetramines. It is preferable to select a chain extender component having a high cohesiveness and a high elastic modulus composed of a combination of a chain polyamine and the like, and the ratio of the soft component is preferably 40 to 65 mass%, more preferably 45 to 60 mass%. Moreover, as a soft component, since it is easy to raise the elasticity modulus of a polyurethane, a polycarbonate-type polyol is preferable as a soft component.

  The polymer elastic body may contain two or more kinds of polymer elastic bodies in order to adjust the performance and manufacturability of the polishing pad. The storage elastic modulus in can be theoretically calculated as the sum of values obtained by multiplying the storage elastic modulus of each polymer elastic body by the mass fraction.

  Moreover, the polymer elastic body of this embodiment has a water absorption rate of 0.2 to 5% by mass when water absorption is saturated at 50 ° C. When the water absorption is less than 0.2% by mass, it becomes difficult to hold the polishing slurry, and the polishing efficiency and the polishing uniformity are likely to be lowered. When the amount exceeds 5% by mass, the time-dependent change during polishing tends to increase due to the water absorption and softening of the polymer elastic body restraining the fiber bundle. And when the water absorption is saturated at 50 ° C., the water absorption is preferably in the range of 0.5 to 3 mass%. When the water absorption rate of the polymer elastic body is within such a range, the high wettability of the abrasive slurry with respect to the polishing pad is maintained during polishing, and the rigidity is further suppressed from decreasing over time. be able to. Thereby, a high polishing rate, polishing uniformity and polishing stability can be maintained.

  The water absorption rate of the polymer elastic body is a water absorption rate when the polymer elastic body film subjected to the drying treatment is immersed in water at room temperature and saturated and swelled, as will be described in detail later. Further, when two or more kinds of polymer elastic bodies are contained, it can be theoretically calculated as the sum of values obtained by multiplying the water absorption of each polymer elastic body by the mass fraction.

  The polymer elastic body having such a water absorption rate is such that the composition of the polymer constituting the polymer elastic body, the cross-linking density is adjusted, the hydrophilic functional group is introduced, and the amount thereof is selected. Can be achieved.

  For example, water absorption and hydrophilicity are adjusted by introducing at least one hydrophilic group selected from the group consisting of a carboxyl group, a sulfonic acid group, and a polyalkylene glycol group having 3 or less carbon atoms into the polymer elastic body. can do. Thereby, the wettability with respect to the abrasive slurry of a polishing pad in the case of grinding | polishing can be improved. Such a hydrophilic group can be introduced into the polymer elastic body by copolymerizing a monomer component having a hydrophilic group as a monomer component for producing the polymer elastic body. The copolymerization ratio of the monomer component having such a hydrophilic group is 0.1 to 10% by mass, and further 0.5 to 5% by mass while minimizing swelling and softening due to water absorption. From the point that water absorption and wettability can be improved.

  The polymer elastic bodies may be used alone or in combination of two or more. Among these, polyurethane resin is excellent in adhesiveness for bundling ultrafine fibers, constraining and binding fiber bundles, and increasing the hardness of the polishing pad, From the viewpoint of excellent mechanical stability. Further, the polyurethane resin having at least one hydrophilic group selected from the group consisting of a carboxyl group, a sulfonic acid group, and a polyalkylene glycol group having 3 or less carbon atoms is used for the rigidity, wettability and polishing of the polishing pad. This is preferable because the stability over time is high.

  When the polymer elastic body is a polyurethane resin, specific examples of the carboxyl group include 2,2-bis (hydroxymethyl) propionic acid, 2,2-bis (hydroxymethyl) butanoic acid, 2,2- A carboxyl group such as bis (hydroxymethyl) valeric acid can be used, and a carboxyl group can be introduced into the skeleton of the polyurethane elastic body in combination with a diol containing these carboxyl groups. Specific examples of the polyalkylene glycol group having 3 or less carbon atoms include polyethylene glycol, polypropylene glycol and copolymers thereof. The polyurethane resin having at least one hydrophilic group selected from the group consisting of a carboxyl group, a sulfonic acid group, and a polyalkylene glycol group having 3 or less carbon atoms has the advantage of improving wettability, but has a water absorption rate. There is a tendency to increase, and in general, the water absorption is 5 to 15% by mass. Therefore, in order to obtain a water absorption of 0.2 to 5% by mass in the present embodiment, at least one hydrophilic property selected from the group consisting of a carboxyl group, a sulfonic acid group, and a polyalkylene glycol group having 3 or less carbon atoms. The amount of the group is preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass. Furthermore, the polyol has a low water-absorbing component, for example, the above-described polyester-based polyol or polycarbonate. It is preferable to use a polyol or the like.

  For example, when the polymer elastic body is a polyurethane resin obtained by using an amorphous polycarbonate diol in combination with a carboxyl group-containing diol as a polyol component and using an alicyclic diisocyanate as a diisocyanate component, The glass transition temperature of the molecular elastic body is −10 ° C. or lower, the storage elastic modulus at 23 ° C. and 50 ° C. is 90 to 900 MPa, and the water absorption is 0.2 to 5% by mass when water is saturated at 50 ° C. From the viewpoint of ease, it is preferable to use such a polymer elastic body.

  As the hard component (isocyanate component or chain extender component) of the polyurethane resin used in the present invention, for example, the above-mentioned isocyanate component and the above-described chain extender component having high cohesiveness can be selected. The ratio of the soft component (polyol component) is preferably 65% by mass or less, more preferably 60% by mass or less. When the amount of the soft component exceeds 65% by mass, the water absorption rate tends to increase. When the polymer elastic body is an aqueous polyurethane, the aqueous polyurethane preferably has an average particle diameter of 0.01 to 0.2 μm in order to obtain a water absorption of 0.2 to 5% by mass. In the case of 0.01 μm or less or 0.2 μm or more, the water absorption rate tends to exceed 5% by mass.

  In addition, when the polymer elastic body is a polyurethane resin, in order to control the water absorption rate and the storage elastic modulus, it contains two or more functional groups that can react with the functional group of the monomer unit forming the polyurethane in the molecule. It is also preferable to form a crosslinked structure by adding a crosslinking agent or a self-crosslinking compound such as a polyisocyanate compound or a polyfunctional blocked isocyanate compound.

  As a combination of the functional group of the monomer unit and the functional group of the crosslinking agent, carboxyl group and oxazoline group, carboxyl group and carbodiimide group, carboxyl group and epoxy group, carboxyl group and cyclocarbonate group, carboxyl group and aziridine group, Examples thereof include a carbonyl group and a hydrazine derivative or a hydrazide derivative. Among these, a combination of a monomer unit having a carboxyl group and a crosslinking agent having an oxazoline group, a carbodiimide group or an epoxy group, a combination of a monomer unit having a hydroxyl group or an amino group and a crosslinking agent having a blocked isocyanate group, and carbonyl A combination of a monomer unit having a group and a hydrazine derivative or a hydrazide derivative is particularly preferred because crosslinking is easy and the resulting polishing pad has excellent rigidity and wear resistance. The crosslinked structure is preferably formed in the heat treatment step after impregnating the fiber entangled body with the aqueous polyurethane resin solution from the viewpoint of maintaining the stability of the aqueous polymer solution. Among these, a carbodiimide group and / or an oxazoline group are particularly preferable because they are excellent in crosslinking performance and pot life of an aqueous liquid and have no problem in safety. Examples of the crosslinking agent having a carbodiimide group include water-dispersed carbodiimide compounds such as “Carbodilite E-01”, “Carbodilite E-02”, and “Carbodilite V-02” manufactured by Nisshinbo Industries, Ltd. Examples of the crosslinking agent having an oxazoline group include water-dispersed oxazoline compounds such as “Epocross K-2010E”, “Epocross K-2020E”, and “Epocross WS-500” manufactured by Nippon Shokubai Co., Ltd. As a compounding quantity of a crosslinking agent, it is preferable that the active ingredient of a crosslinking agent is 1-20 mass% with respect to a polyurethane resin, and it is more preferable that it is 1.5-10 mass%.

  Moreover, the adhesiveness with the ultrafine fibers is increased to increase the rigidity of the fiber bundle, the glass transition temperature is set to −10 ° C. or lower, the storage elastic modulus at 23 ° C. and 50 ° C. is set to a range of 90 to 900 MPa, Since it is easy to adjust the water absorption rate when the water absorption is saturated at 50 ° C. to 0.2 to 5% by mass, the content of the polyol component in the polyurethane resin is 65% by mass or less, Is preferably 60% by mass or less. Moreover, it is preferable from the point which can suppress generation | occurrence | production of a scratch by providing moderate elasticity that it is 40 mass% or more, and also 45 mass% or more.

  In addition, the polyurethane-based resin is within the range that does not impair the effect of the present invention, and the penetrant, antifoaming agent, lubricant, water repellent, oil repellent, thickener, extender, curing accelerator, antioxidant, ultraviolet ray It may further contain an absorbent, an antifungal agent, a foaming agent, a water-soluble polymer compound such as polyvinyl alcohol and carboxymethyl cellulose, a dye, a pigment, inorganic fine particles and the like.

  The polymer elastic body is preferably present in an ultrafine fiber bundle in which 5 to 70 ultrafine fibers having an average fineness of 0.01 to 0.8 dtex forming an ultrafine fiber entangled body are converged. The ultrafine fibers are converged by a polymer elastic body existing inside the ultrafine fiber bundle, and the ultrafine fibers are converged so that a part or the whole of the interior of the fiber bundle is converged, and the ultrafine fiber bundle is Be bound. It is preferable that the ultrafine fibers are focused and the ultrafine fiber bundles are constrained from the viewpoint of increasing the rigidity of the polishing pad and improving the planarization performance, polishing uniformity, and stability over time.

  Further, the polishing pad has voids in the range where the volume ratio excluding the voids (hereinafter also referred to as the polishing pad filling rate) is in the range of 40 to 95%, that is, in the range in which the voidage is 5 to 60%. It is preferable that it has both moderate rigidity and liquid retention of the polishing pad.

  In this case, if the porosity of the polishing pad impregnated with the polymer elastic body is 50% or more, it is preferable in terms of excellent bare silicon wafer polishing because it has both slurry retention and moderate rigidity and cushioning properties. In this case, the upper limit is preferably 70% or less from the viewpoint of excellent polishing rate and flatness in rough polishing typified by bare silicon wafer polishing.

  Further, it is more preferable that a part of the voids form a communication hole that communicates with the inside of the polishing pad in terms of improving the liquid retention of the slurry.

  The polymer elastic body is preferably an aqueous polyurethane because the wettability of the polishing slurry is good, and the aqueous polyurethane preferably has an average particle diameter of 0.01 to 0.2 μm. When the average particle size is 0.01 μm or more, the water resistance is good and the stability over time during polishing is excellent. When the average particle size is 0.2 μm or less, the binding force of the fiber bundle is improved, the flatness is excellent, the pad life during polishing is prolonged, and the stability over time is excellent. In order to adjust the above particle size, for example, at least one hydrophilic group selected from the group consisting of a polymer elastic body consisting of a carboxyl group, a sulfonic acid group, and a polyalkylene glycol group having 3 or less carbon atoms is used. It is preferable to contain.

  The ratio of the ultrafine fiber entangled body to the polymer elastic body (ultrafine fiber entangled body / polymer elastic body) is preferably 55/45 to 95/5 in mass ratio. When the mass ratio of the ultrafine fiber entangled body is 55% or more, the stability over time during polishing is excellent and the polishing efficiency tends to be improved. When the mass ratio of the ultrafine fiber entangled body is 95% or less, the binding force of the polymer elastic body in the fiber bundle is maintained, and the pad wear during polishing is reduced with excellent flatness. In particular, the mass ratio of the ultrafine fiber entangled body and the polymer elastic body is preferably in the range of 60/40 to 90/10.

The apparent density of the polishing pad of the present embodiment is 0.4 to 1.2 g / cm ³ , and further 0.5 to 1.0 g because the slurry retention is kept good and the rigidity is kept high. / Cm ³ is preferable. In the case of bare silicon wafer polishing, it is preferably 0.3 to 0.75 g / cm ³ , and preferably 0.4 to 0.65 g / cm ^{3 in} terms of having both an improvement in polishing rate and flatness. It is preferable that

  In the present embodiment, the average length of the ultrafine fiber bundle is not particularly limited. However, the fiber density of the ultrafine fiber can be easily increased by being 100 mm or more, and further 200 mm or more, and the rigidity of the polishing pad. It is preferable from the viewpoint that the fiber can be easily increased and the loss of fibers can be suppressed. When the length of the fiber bundle is too short, it is difficult to increase the density of the ultrafine fibers, sufficient rigidity is not obtained, and the ultrafine fibers tend to come off easily during polishing. An upper limit is not specifically limited, For example, when it contains the fiber entanglement body derived from the nonwoven fabric manufactured by the spunbond method mentioned later, unless it cut | disconnects physically, several m, several hundred m, several km Alternatively, longer fiber lengths may be included.

  The polishing pad of the present embodiment preferably has a structure in which the fiber entangled body is filled with a polymer elastic body and combined.

  In the polishing pad of the present embodiment, it is preferable that the polymer elastic body is present inside the ultrafine fiber bundle from the viewpoint of increasing the rigidity of the polishing pad, and the ultrafine fiber forming the ultrafine fiber bundle is a polymer elastic body. It is more preferable that the light is focused. Thus, the rigidity of the polishing pad becomes higher due to the ultrafine fibers being focused. Since the ultrafine fibers are converged and each of the ultrafine fibers is difficult to move, the rigidity of the polishing pad is increased, so that high planarization performance is easily obtained. Further, the loss of fibers is reduced, and it is possible to prevent the abrasive grains from aggregating on the lost fibers, thereby making it difficult for scratches to occur. Here, the fact that the ultrafine fibers are converged means that most of the ultrafine fibers existing in the ultrafine fiber bundle (preferably the number is 10% or more, more preferably 20% or more, further preferably 50% or more, most preferably Means 60% or more) is bonded and restrained by the polymer elastic body existing inside the ultrafine fiber bundle.

  It is also preferable that the plurality of ultrafine fiber bundles are bound together by a polymer elastic body existing outside the ultrafine fiber bundle and exist in a lump (bulk) shape. In this way, by binding the ultrafine fiber bundles, the form stability of the polishing pad is improved and the polishing stability is improved.

  The focused / restrained state of the ultrafine fibers and the binding state of the ultrafine fiber bundles can be confirmed by an electron micrograph of the cross section of the polishing pad.

  The polymer elastic body in which the ultrafine fibers are bundled and the polymer elastic body in which the ultrafine fiber bundles are bound to each other are preferably non-porous. The non-porous state is a state substantially free of voids (closed cells) as possessed by a porous or sponge-like (hereinafter also simply referred to as porous) polymer elastic body. Means. Specifically, it means that it is not a polymer elastic body having a large number of fine bubbles, for example, obtained by coagulating solvent-based polyurethane. When the polymer elastic body that is focused or bound is non-porous, the polishing stability becomes high, and the slurry waste and pad waste during polishing are less likely to accumulate in the voids. And a high polishing rate can be maintained for a long time. Furthermore, since the adhesive strength with respect to the ultrafine fibers is increased, it is possible to suppress the occurrence of scratches due to the loss of the fibers. Furthermore, since higher rigidity is obtained, a polishing pad having excellent planarization performance can be obtained.

  In addition, the polishing pad of the present embodiment preferably has a water absorption rate of 10 to 80% by mass, more preferably 15 to 70% by mass when saturated and swollen with 50 ° C. warm water. If the water absorption is 10% by mass or more, it is easy to hold the abrasive slurry, the polishing rate is improved, and the polishing uniformity tends to be improved. If the water absorption is 80% by mass or less, a high polishing rate can be obtained, and characteristics such as hardness are difficult to change during polishing, and thus there is a tendency that the temporal stability of the planarization performance is excellent.

The polishing pad of the present embodiment is present in the vicinity of the surface by performing a pad flattening process by buffing or the like, a seasoning process (conditioning process) before polishing using a pad dressing such as diamond, or a dressing process at the time of polishing. By dividing or fibrillating the ultrafine fiber bundle to be formed, ultrafine fibers can be formed on the surface of the polishing pad. The fiber density of the ultrafine fibers on the surface of the polishing pad is preferably 600 fibers / mm ² or more, more preferably 1000 fibers / mm ² or more, and particularly preferably 2000 fibers / mm ² or more. When the fiber density is too low, the retention of abrasive grains tends to be insufficient. The upper limit of the fiber density is not particularly limited, but is about 1,000,000 pieces / mm ² from the viewpoint of productivity. Further, the ultrafine fibers on the surface of the polishing pad may be raised or not raised. When the ultrafine fibers are raised, the surface of the polishing pad becomes softer and the effect of reducing scratches becomes higher. On the other hand, when the degree of napping of the ultrafine fibers is low, it is advantageous for applications in which microflatness is important. Thus, it is preferable to appropriately select the surface state according to the application.

[Production method of polishing pad]
Next, an example of the manufacturing method of the polishing pad of this embodiment will be described in detail.

  The polishing pad of the present embodiment includes, for example, a web manufacturing process for manufacturing a long fiber web made of sea-island type composite fibers obtained by melt spinning a water-soluble thermoplastic resin and a water-insoluble thermoplastic resin, and the long fibers A web entanglement step of forming a web entanglement sheet by entanglement with a plurality of webs, and moist heat to shrink the area shrinkage rate to 30% or more by subjecting the web entanglement sheet to wet heat shrinkage A shrinkage treatment step, a fiber entanglement forming step for forming a fiber entangled body made of ultrafine fibers by dissolving the water-soluble thermoplastic resin in the web entangled sheet in hot water, and the fiber entangled body It can be obtained by a method for producing a polishing pad comprising a polymer elastic body filling step of impregnating and drying and solidifying an aqueous liquid of a polymer elastic body.

  In the above manufacturing method, the web entangled sheet containing the long fibers is subjected to the heat and heat shrinkage process, so that the web entangled sheet is largely contracted as compared with the case where the web entangled sheet containing the short fibers is subjected to the heat and heat shrinkage. For this reason, the fiber density of the ultrafine fibers becomes dense. And the fiber entanglement body which consists of an ultrafine fiber bundle is formed by melt-extracting the water-soluble thermoplastic resin of a web entanglement sheet. At this time, voids are formed in the portion where the water-soluble thermoplastic resin is dissolved and extracted. The voids are sufficiently impregnated with an aqueous liquid of a high-concentration polymer elastic body and dried and solidified, whereby the ultrafine fibers constituting the ultrafine fiber bundle are converged and the ultrafine fiber bundles are also converged. In this way, a polishing pad having a high fiber density, a low porosity, and a high rigidity in which ultrafine fibers are focused is obtained.

  Also, by adjusting the amount of the polymer elastic body impregnated in the shrinkage treatment and the voids, the porosity of the polishing pad is set to 50% or more, so that appropriate rigidity, abrasive slurry retention and cushioning properties can be obtained. A polishing pad suitable for a bare silicon wafer having both improvements can be obtained.

  Each step will be described in detail below.

(1) Web manufacturing process In this process, first, a long fiber web made of sea-island composite fibers obtained by melt spinning a water-soluble thermoplastic resin and a water-insoluble thermoplastic resin is manufactured.

  The sea-island type composite fiber is obtained by melt spinning each of a water-soluble thermoplastic resin and a water-insoluble thermoplastic resin having low compatibility with the water-soluble thermoplastic resin, and then combining them. Then, the ultrafine fiber is formed by dissolving or removing the water-soluble thermoplastic resin from the sea-island type composite fiber. The thickness of the sea-island type composite fiber is preferably 0.5 to 3 dtex from the viewpoint of industrial properties.

  In this embodiment, the sea-island type composite fiber will be described in detail as the composite fiber for forming the ultra-fine fiber, but a known ultra-fine fiber generating type fiber such as a multilayer laminated cross-section fiber is used instead of the sea-island type fiber. May be.

  The water-soluble thermoplastic resin is preferably a thermoplastic resin that can be dissolved or removed by water, an alkaline aqueous solution, an acidic aqueous solution, or the like and that can be melt-spun. Specific examples of such a water-soluble thermoplastic resin include, for example, polyvinyl alcohol resins (PVA resins) such as polyvinyl alcohol and polyvinyl alcohol copolymers; copolymers of polyethylene glycol and / or alkali metal sulfonates. Modified polyesters contained as components; polyethylene oxide and the like. Among these, PVA-based resins are particularly preferably used for the following reasons.

  When a sea-island type composite fiber having a PVA-based resin as a water-soluble thermoplastic resin component is used, the ultrafine fibers formed by dissolving the PVA-based resin are greatly crimped. As a result, a fiber entangled body having a high fiber density can be obtained. In addition, when a sea-island type composite fiber containing a PVA resin as a water-soluble thermoplastic resin component is used, when the PVA resin is dissolved, the formed ultrafine fibers and polymer elastic body are not substantially decomposed or dissolved. Therefore, the physical properties of the ultrafine fiber and the polymer elastic body are hardly lowered. Furthermore, the environmental load is small.

  The PVA-based resin can be obtained by saponifying a copolymer mainly composed of vinyl ester units. Specific examples of vinyl monomers for forming the vinyl ester unit include, for example, vinyl acetate, vinyl formate, vinyl propionate, vinyl valelate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, Examples include vinyl pivalate and vinyl versatate. These may be used alone or in combination of two or more. Among these, vinyl acetate is preferable from the viewpoint of industrial properties.

  The PVA-based resin may be a homo PVA composed only of vinyl ester units or a modified PVA containing a comonomer unit other than the vinyl ester unit as a constituent unit. Modified PVA is more preferable from the viewpoint of controlling melt spinnability, water solubility, and fiber properties. Specific examples of the comonomer unit other than the vinyl ester unit include, for example, α-olefins having 4 or less carbon atoms such as ethylene, propylene, 1-butene and isobutene; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether. And vinyl ethers such as isopropyl vinyl ether and n-butyl vinyl ether. The content ratio of the comonomer units other than the vinyl ester unit is preferably 1 to 20 mol%, more preferably 4 to 15 mol%, and particularly preferably 6 to 13 mol%. Among these, ethylene-modified PVA containing 4 to 15 mol%, more preferably 6 to 13 mol% of ethylene units is preferable from the viewpoint of improving the physical properties of the sea-island composite fibers.

  The viscosity average degree of polymerization of the PVA-based resin is 200 to 500, more preferably 230 to 470, and particularly 250 to 450, so that a stable sea-island structure is formed and the melt spinnability is excellent. It is preferable from the point which shows melt viscosity and the point whose melt | dissolution rate at the time of melt | dissolution is quick. The degree of polymerization is measured according to JIS-K6726. That is, after re-saponifying and purifying the PVA resin, it is obtained from the intrinsic viscosity [η] measured in water at 30 ° C. by the following equation.

Viscosity average degree of polymerization P = ([η] × 103 / 8.29) (1 / 0.62)
The saponification degree of the PVA-based resin is 90 to 99.99 mol%, more preferably 93 to 99.98 mol%, particularly 94 to 99.97 mol%, particularly 96 to 99.96 mol%. It is preferable that it is the range of these. When the saponification degree is in such a range, a PVA resin having excellent water solubility, excellent thermal stability, excellent melt spinnability, and excellent biodegradability can be obtained.

  The melting point of the PVA-based resin is 160 to 250 ° C., more preferably 170 to 227 ° C., particularly 175 to 224 ° C., particularly 180 to 220 ° C., in view of mechanical properties and thermal stability. It is preferable from the point which is excellent, and the point which is excellent in melt spinnability. When the melting point of the PVA-based resin is too high, the melting point and the decomposition temperature are close to each other, so that the melt spinnability tends to be reduced by causing decomposition during melt spinning.

  Moreover, when the melting point of the PVA-based resin is too low as compared with the melting point of the water-insoluble thermoplastic resin, it is not preferable because the melt spinnability is lowered. From this point of view, it is preferable that the melting point of the PVA-based resin is not lower than 60 ° C. or even 30 ° C. or higher compared to the melting point of the water-insoluble thermoplastic resin.

  As the water-insoluble thermoplastic resin, a resin that can be melt-spun and is a thermoplastic resin that is not dissolved or removed by water, an alkaline aqueous solution, an acidic aqueous solution, or the like.

  As a specific example of the water-insoluble thermoplastic resin, various thermoplastic resins used for forming the ultrafine fibers constituting the polishing pad described above can be used.

  The water-insoluble thermoplastic resin may contain various additives. Specific examples of the additive include, for example, a catalyst, an anti-coloring agent, a heat-resistant agent, a flame retardant, a lubricant, an antifouling agent, a fluorescent whitening agent, a matting agent, a coloring agent, a gloss improving agent, an antistatic agent, and an aroma. Agents, deodorants, antibacterial agents, acaricides, inorganic fine particles and the like.

  Next, a method for forming a sea-island composite fiber by melt spinning the water-soluble thermoplastic resin and the water-insoluble thermoplastic resin and forming a long fiber web from the obtained sea-island composite fiber will be described in detail. To do.

  The long fiber web can be obtained, for example, by combining the water-soluble thermoplastic resin and the water-insoluble thermoplastic resin by melt spinning and then stretching and depositing by a spunbond method. In this way, by forming the web by the spunbond method, a long fiber web made of sea-island type composite fibers with less fiber loss, high fiber density, and good shape stability can be obtained. In addition, a long fiber is a fiber manufactured without passing through a cutting process like manufacturing a short fiber.

  In the production of a sea-island type composite fiber, a water-soluble thermoplastic resin and a water-insoluble thermoplastic resin are melt-spun and combined. The mass ratio of the water-soluble thermoplastic resin to the water-insoluble thermoplastic resin is preferably in the range of 5/95 to 50/50, more preferably 10/90 to 40/60. When the mass ratio of the water-soluble thermoplastic resin to the water-insoluble thermoplastic resin is within such a range, a high-density fiber entangled body can be obtained, and the formability of ultrafine fibers is excellent.

  A method for forming a long fiber web by a spunbond method after combining a water-soluble thermoplastic resin and a water-insoluble thermoplastic resin by melt spinning will be described in detail below.

  First, a water-soluble thermoplastic resin and a water-insoluble thermoplastic resin are melted and kneaded by separate extruders, and molten resin strands are simultaneously discharged from different spinnerets. Then, after the discharged strands are combined with the composite nozzle, the sea-island type composite fibers are formed by discharging from the nozzle holes of the spinning head. In melt composite spinning, the number of islands in a sea-island type composite fiber is 4 to 4000 islands / fiber, more preferably 10 to 1000 islands / fiber, so that a fiber bundle having a small single fiber fineness and a high fiber density can be obtained. To preferred.

After the sea-island type composite fiber is cooled by a cooling device, it is stretched by a high-speed air current at a speed corresponding to a take-up speed of 1000 to 6000 m / min so as to obtain a desired fineness using a suction device such as an air jet nozzle. The Thereafter, the stretched composite fibers are deposited on a movable collection surface to form a long fiber web. At this time, the long fiber web deposited may be partially crimped as necessary. The basis weight of the fiber web is preferably in the range of ^{20 to} 500 g / m ² , so that a uniform fiber entangled body can be obtained, and it is preferable from the viewpoint of industrial properties.

(2) Web entanglement process Next, the web entanglement process which forms a web entanglement sheet | seat by accumulating and entwining a plurality of the said long fiber webs is demonstrated.

  The web entangled sheet is formed by performing an entanglement treatment on the long fiber web using a known nonwoven fabric manufacturing method such as needle punching or high-pressure water flow treatment. Below, the entanglement process by a needle punch is demonstrated in detail as a typical example.

  First, a silicone oil agent or a mineral oil agent such as a needle breakage prevention oil agent, an antistatic oil agent, and an entanglement improving oil agent is applied to the long fiber web. In order to reduce unevenness in weight per unit area, two or more fiber webs may be overlapped with a cross wrapper and an oil agent may be applied.

Thereafter, for example, an entanglement process is performed in which the fibers are entangled three-dimensionally by a needle punch. By performing the needle punching process, a web entangled sheet having a high fiber density and hardly causing the fiber to come off can be obtained. The basis weight of the web-entangled sheet is appropriately selected according to the thickness of the target polishing pad, and specifically, for example, the handling property is in the range of 100 to 1500 g / m ² . From the point which is excellent in it.

The conditions such that the delamination force of the web entangled sheet is increased as appropriate for the needle conditions such as the type and amount of the oil agent and the needle shape, needle depth, and number of punches in the needle punch. The number of barbs is preferably as large as possible without causing needle breakage. Specifically, for example, the number of barbs is selected from 1 to 9 barbs. The needle depth is preferably set so that the barb penetrates to the overlapped web surface, and in a range where the pattern after needle punching is not strong on the web surface. The number of needle punches is adjusted depending on the shape of the needle, the type and amount of oil used, and specifically, 500 to 5000 punches / cm ² is preferable. In addition, the fiber density can be obtained by performing the entanglement process so that the basis weight after the entanglement process is 1.2 times or more by mass ratio of the basis weight before the entanglement process, and further 1.5 times or more. A high fiber entangled body can be obtained, and it is preferable from the viewpoint that the loss of fibers can be reduced. The upper limit is not particularly limited, but is preferably 4 times or less from the viewpoint of avoiding an increase in manufacturing cost due to a decrease in processing speed.

  Further, when a polishing pad for bare silicon wafer polishing is used, the porosity of the polishing pad is preferably 50% or more. For this purpose, depending on whether the fiber density is increased or decreased, polymer elasticity is increased. You may adjust with the filling amount of a body.

  The delamination force of the web entangled sheet is 2 kg / 2.5 cm or more, more preferably 4 kg / 2.5 cm or more, the shape retention is good, the fibers are not easily pulled out, and the fiber density is high. This is preferable from the viewpoint of obtaining a fiber entangled body. Note that the delamination force is a measure of the degree of three-dimensional entanglement. When the delamination force is too small, the fiber density of the fiber entangled body is not sufficiently high. Moreover, although the upper limit of the delamination force of an entangled nonwoven fabric is not specifically limited, It is preferable that it is 30 kg / 2.5 cm or less from the point of an entanglement process efficiency.

  In addition, for the purpose of adjusting the hardness of the polishing pad, the web entangled sheet, which is a nonwoven fabric obtained as described above, is further made of ultrafine fibers, as long as the effects of the present invention are not impaired. A knitted fabric or a woven fabric (knitted fabric) is entangled by needle punching and / or high-pressure water flow treatment, and the knitted fabric is entangled and integrated, for example, a knitted fabric / entangled nonwoven fabric. A laminated structure such as entangled nonwoven fabric / knitted fabric / entangled nonwoven fabric may be used as the web entangled sheet.

  The ultrafine fibers that constitute the knitted fabric are not particularly limited. Specifically, for example, polyester fiber formed from polyethylene terephthalate (PET), polytrimethylene terephthalate, polybutylene terephthalate (PBT), polyester elastomer, etc .; from polyamide 6, polyamide 66, aromatic polyamide, polyamide elastomer, etc. Polyamide fibers to be formed; fibers made of urethane polymers, olefin polymers, acrylonitrile polymers and the like are preferably used. In these, the fiber formed from PET, PBT, polyamide 6, polyamide 66 etc. is preferable from an industrial point.

  Specific examples of the removal component of the sea-island type composite fiber forming the knitted fabric include polystyrene and its copolymer, polyethylene, PVA resin, copolymer polyester, copolymer polyamide and the like. Among these, PVA-based resins are preferably used because they cause large shrinkage when dissolved and removed.

(3) Wet heat shrinkage treatment step Next, a wet heat shrinkage treatment step for increasing the fiber density and the degree of entanglement of the web entangled sheet by shrinking the web entangled sheet with heat and moisture will be described. In this step, the web-entangled sheet containing long fibers is contracted by wet heat, so that the web-entangled sheet is contracted greatly compared to the case where the web-entangled sheet containing short fibers is contracted by wet heat. As a result, the fiber density of the ultrafine fibers is particularly high.

  The wet heat shrinkage treatment is preferably performed by steam heating. As the steam heating condition, it is preferable to perform heat treatment for 60 to 600 seconds at an ambient temperature of 60 to 130 ° C. and a relative humidity of 75% or more, and further a relative humidity of 90% or more. Such heating conditions are preferable because the web-entangled sheet can be shrunk at a high shrinkage rate. In addition, when relative humidity is too low, there exists a tendency for shrinkage | contraction to become inadequate because the water | moisture content which contacted the fiber dries rapidly.

  In the wet heat shrinkage treatment, the web entangled sheet is preferably shrunk so that the area shrinkage rate is 30% or more, preferably 35% or more, and further 40% or more. By shrinking at such a high shrinkage rate, a high fiber density can be obtained. The upper limit of the area shrinkage rate is not particularly limited, but is preferably about 80% or less from the viewpoint of shrinkage limit and processing efficiency.

The area shrinkage rate (%) is expressed by the following formula (1):
(Area of sheet surface before shrinking process−Area of sheet surface after shrinking process) / Area of sheet surface before shrinking process × 100 (1) The said area means the average area of the area of the surface of a sheet | seat, and the area of a back surface.

  The web-entangled sheet thus subjected to the wet heat shrinkage treatment can be adjusted in porosity by heating roll or hot pressing at a temperature equal to or higher than the heat deformation temperature of the sea-island type composite fiber, thereby strengthening the hot press conditions. Thus, the fiber density can be increased and densified.

  In addition, as a change in the basis weight of the web-entangled sheet before and after the wet heat shrinkage treatment, the basis weight after the shrinkage treatment is 1.2 times (mass ratio) or more compared to the basis weight before the shrinkage treatment, It is preferably 1.5 times or more, 4 times or less, and more preferably 3 times or less.

(4) Fiber bundle binding step The purpose of increasing the form stability of the web entangled sheet and adjusting or reducing the porosity of the resulting polishing pad before performing the ultrafine fiber treatment of the web entangled sheet As necessary, the fiber bundle may be bound in advance by impregnating the web-entangled sheet subjected to the shrink treatment with an aqueous liquid of a polymer elastic body and drying and solidifying the sheet.

  In this step, the web entangled sheet is filled with the polymer elastic body by impregnating the contracted web entangled sheet with the aqueous liquid of the polymer elastic body and drying and solidifying it. The aqueous liquid of the polymer elastic body has a low viscosity even at a high concentration and is excellent in impregnation permeability, so that it can be easily filled in the web entangled sheet. Moreover, the adhesiveness with respect to a fiber is also excellent. Therefore, it is possible to firmly restrain the sea-island type composite fiber by performing this step.

  The aqueous liquid of the polymer elastic body is an aqueous solution in which the component forming the polymer elastic body is dissolved in the aqueous medium, or the aqueous dispersion liquid in which the component forming the polymer elastic body is dispersed in the aqueous medium. The aqueous dispersion includes a suspension dispersion and an emulsion dispersion. In particular, it is more preferable to use an aqueous dispersion from the viewpoint of excellent water resistance.

  The method for making the polyurethane resin into an aqueous solution or an aqueous dispersion is not particularly limited, and a known method can be used. Specifically, for example, by adding a monomer unit having a hydrophilic group such as a carboxyl group, a sulfonic acid group, or a hydroxyl group, a method of imparting dispersibility to an aqueous medium to a polyurethane resin, or a surface activity of the polyurethane resin. The method of emulsifying or suspending by adding an agent is mentioned. Further, such an aqueous polymer elastic body has excellent wettability to water, and thus has excellent characteristics for holding a large amount of abrasive grains.

  Specific examples of the surfactant used for the emulsification or suspension include, for example, sodium lauryl sulfate, ammonium lauryl sulfate, sodium polyoxyethylene tridecyl ether acetate, sodium dodecylbenzene sulfonate, sodium alkyldiphenyl ether disulfonate, dioctyl sulfosuccinate. Anionic surfactants such as sodium oxide; nonions such as polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene-polyoxypropylene block copolymer Surfactants and the like. Moreover, you may use what is called reactive surfactant which has reactivity. Moreover, heat-sensitive gelation property can also be provided to a polyurethane resin by selecting the cloud point of surfactant suitably. However, when a large amount of surfactant is used, it may have an adverse effect on the polishing performance and its stability over time, so it is preferable to minimize the necessary amount.

  By setting the solid content concentration of the aqueous liquid of the polymer elastic body to 10% by mass or more, and further to 15% by mass or more, the porosity can be reduced.

  Examples of the method of impregnating the web entangled sheet with the aqueous polymer elastic liquid include a method using a knife coater, a bar coater, or a roll coater, or a dipping method.

  The polymer elastic body can be solidified by drying the web entangled sheet impregnated with the aqueous liquid of the polymer elastic body. As a drying method, the method of heat-processing in a 50-200 degreeC drying apparatus, the method of heat-processing in a dryer after infrared heating, etc. are mentioned.

  When the web entangled sheet is impregnated with an aqueous liquid of a polymer elastic body and then dried, the aqueous liquid migrates to the surface layer of the web entangled sheet, thereby obtaining a uniform filling state. It may not be possible. In such a case, the particle size of the polymer elastic body of the aqueous liquid is adjusted; the kind and amount of ionic groups of the polymer elastic body are adjusted, or the stability is adjusted by pH or the like. Monovalent or divalent alkali metal salts or alkaline earth metal salts, nonionic emulsifiers, associative water-soluble thickeners, associative thermosensitive gelling agents such as water-soluble silicone compounds, water-soluble polyurethane compounds, Alternatively, migration can be suppressed by, for example, reducing the water dispersion stability at about 40 to 100 ° C. by using, for example, an organic substance or an inorganic substance whose pH is changed by heat. In addition, you may make it migrate so that a polymeric elastic body may be unevenly distributed on the surface as needed.

(5) Ultrafine fiber formation process Next, the ultrafine fiber formation process, which is a process of forming ultrafine fibers by dissolving a water-soluble thermoplastic resin in hot water, will be described.

  This step is a step of forming ultrafine fibers by removing the water-soluble thermoplastic resin. At this time, voids are formed in the portion of the web entangled sheet where the water-soluble thermoplastic resin is dissolved and extracted. Then, the microfibers are focused by filling the voids with a polymer elastic body in a subsequent polymer elastic body filling step. In addition, the ultrafine fiber bundle is restrained.

  The ultrafine fiber treatment is performed by hydrothermally treating a web entangled sheet or a composite of a web entangled sheet and a polymer elastic body with water, an aqueous alkaline solution, an acidic aqueous solution, etc. It is a process of dissolving and removing or decomposing and removing.

  As a specific example of the hot water heat treatment conditions, for example, as a first stage, after being immersed in hot water at 65 to 90 ° C. for 5 to 300 seconds, further as a second stage, hot water at 85 to 100 ° C. It is preferable to perform the treatment for 100 to 600 seconds. Moreover, in order to improve dissolution efficiency, you may perform the nip process by a roll, a high pressure water flow process, an ultrasonic process, a shower process, a stirring process, a stagnation process, etc. as needed.

  In this step, when the ultrafine fiber is formed by dissolving the water-soluble thermoplastic resin from the sea-island type composite fiber, the ultrafine fiber is greatly shrunk. Since the fiber density becomes dense by this shrinkage, a high-density fiber entangled body is obtained.

(6) Polymer Elastic Body Filling Step Next, by filling a polymer elastic body inside the ultrafine fiber bundle formed from the ultrafine fibers, the ultrafine fibers are focused, the ultrafine fiber bundles are constrained, and the ultrafine fibers are confined. The process of further binding the fiber bundles will be described.

  In the ultrafine fiber forming step (5), the sea-island type composite fiber is subjected to ultrafine fiber treatment, whereby the water-soluble thermoplastic resin is removed and voids are formed inside the ultrafine fiber bundle. In this step, by appropriately filling a polymer elastic body into such voids, the ultrafine fibers are focused, the ultrafine fiber bundles are constrained, and the ultrafine fiber bundles are bound to each other. For example, the porosity can be 50% or less. Further, by sufficiently filling the polymer elastic body, the porosity can be lowered and the polishing pad can be made into a dense structure. When the ultrafine fibers form an ultrafine fiber bundle, since the aqueous polymer liquid is easily impregnated by capillary action, the ultrafine fibers are more focused and the ultrafine fiber bundle is more easily restrained.

  As the aqueous liquid of the polymer elastic body used in this step, the same liquid as the aqueous liquid of the polymer elastic body described in the fiber bundle binding step (4) can be used.

  A method similar to the method used in the fiber bundle binding step (4) can be applied to the method of filling the polymer elastic body into the ultrafine fiber bundle formed from the ultrafine fibers in this step. And it can adjust to a desired porosity by combining a fiber binding process (4) and a polymeric elastic body filling process (6) suitably. In this way, a polishing pad is formed.

[Post-processing of polishing pad]
The obtained polishing pad may be subjected to post-processing treatment such as molding treatment, flattening treatment, raising treatment, laminating treatment, surface treatment, and washing treatment, if necessary.

  The molding process and the flattening process are processes in which the obtained polishing pad is hot press molded to a predetermined thickness by grinding or cut into a predetermined outer shape. The polishing pad is preferably ground to a thickness of about 0.5 to 3 mm.

  The raising process is a process for separating the focused ultrafine fibers by applying mechanical frictional force or polishing force to the surface of the polishing pad with sandpaper, needle cloth, diamond or the like. By such raising treatment, the fiber bundle existing in the surface portion of the polishing pad is fibrillated, and a large number of ultrafine fibers are formed on the surface.

  The laminating process is a process of adjusting rigidity by laminating the obtained polishing pad on a base material. For example, by laminating the polishing pad with an elastic sheet having low hardness, the global flatness of the surface to be polished (flatness of the entire non-polishing substrate) can be further improved. The adhesion at the time of lamination may be fusion adhesion or adhesion via an adhesive or a pressure-sensitive adhesive. Specific examples of the substrate include, for example, an elastic sponge body made of polyurethane or the like; a nonwoven fabric impregnated with polyurethane (for example, trade name Suba400 manufactured by Nita Haas Co.); natural rubber, nitrile rubber, polybutadiene rubber, silicone Examples thereof include elastic resin films composed of rubbers such as rubber, thermoplastic elastomers such as polyester-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, and fluorine-based thermoplastic elastomers; foamed plastics; sheet-like substrates such as knitted fabrics and woven fabrics.

  The surface treatment is a treatment for forming grooves, holes such as lattices, concentric circles, and spirals on the surface of the polishing pad in order to adjust the retention and discharge of the abrasive slurry.

  In the cleaning treatment, impurities such as particles and metal ions adhering to the obtained polishing pad are washed with cold water or warm water, or an aqueous solution containing an additive having a cleaning action such as a surfactant or the like. This is a process of washing with a solvent.

  The polishing pad of this embodiment is a silicon wafer, a compound semiconductor wafer, a semiconductor wafer, a semiconductor device, a liquid crystal member, an optical element, a crystal, an optical substrate, an electronic circuit substrate, an electronic circuit mask substrate, a multilayer wiring substrate, a hard disk, MEMS (micro -Electro-mechanical systems) It is preferably used for polishing a substrate or the like. In addition, the polishing pad of this embodiment is particularly excellent for polishing a bare silicon wafer by setting the porosity of the polishing pad to 50% or more.

  Specific examples of semiconductor wafers and semiconductor devices include, for example, insulating films such as silicon, silicon oxide, silicon oxyfluoride, and organic polymers; wiring material metal films such as copper, aluminum, and tungsten; tantalum, titanium, tantalum nitride, and nitride Examples thereof include a base material having a barrier metal film such as titanium on the surface.

  In the polishing, it is used for any polishing such as primary polishing, secondary polishing (adjustment polishing), finish polishing, mirror polishing and the like. Moreover, as a grinding | polishing part, any of the surface of a base material, a back surface, and an end surface may be sufficient.

  Hereinafter, the present invention will be specifically described by way of examples. In addition, this invention is not limited at all by the Example.

[Example 1]
Water-soluble thermoplastic polyvinyl alcohol resin (hereinafter referred to as PVA resin) and isophthalic acid-modified polyethylene terephthalate having a degree of modification of 6 mol% (water absorption 1% by mass when saturated with water at 50 ° C., glass transition) (Temperature 77 ° C.) (hereinafter referred to as modified PET) was discharged from the melt composite spinning die at a ratio of 20:80 (mass ratio) to form a sea-island composite fiber. The melt compound spinning die had 50 islands / fiber and a die temperature of 260 ° C. Then, by adjusting the ejector pressure to a spinning speed of 4000 m / min and collecting long fibers having an average fineness of 2.0 dtex on the net, a spunbond sheet (long fiber web) having a basis weight of 40 g / m ² is collected. )was gotten.

Twelve of the obtained spunbond sheets were overlapped by cross-wrapping to create an overlap web having a total basis weight of 480 g / m ² . And the needle | hook breaking prevention oil agent was sprayed on the obtained overlapping web. Next, using the needle needle of No. 42 with 1 barb and the needle needle of No. 42 with 6 barbs, the overlap web is entangled by needle punching at 1800 punch / cm ² By doing so, a web entangled sheet was obtained. The basis weight of the obtained web entangled sheet was 750 g / m ² . Moreover, the area shrinkage rate by the needle punch process was 35%.

Next, the obtained web-entangled sheet was steam-treated for 90 seconds under the conditions of 70 ° C. and 90% RH. The area shrinkage rate at this time was 40%. And after drying in 140 degreeC oven, the web entanglement sheet | seat of the fabric weight 1250g / m < ² >, apparent density 0.65g / cm < ³ >, and thickness 1.9mm was obtained by heat-pressing at 140 degreeC. . At this time, the thickness of the web entangled sheet after hot pressing was 0.80 times the thickness before hot pressing.

Next, the hot-pressed web entangled sheet was impregnated with an aqueous dispersion of polyurethane elastic body A (solid content concentration 20% by mass) as the first polyurethane elastic body. The polyurethane elastic body A comprises an amorphous polycarbonate-based polyol (a copolymer polyol comprising 3-methyl-1,5-pentylene carbonate and hexamethylene carbonate) and a polyalkylene glycol having 2 to 3 carbon atoms. A polyol component containing 99.7: 0.3 (molar ratio) and further containing a carboxyl group-containing monomer (2,2-bis (hydroxymethyl) propionic acid) in a weight ratio of 1.5 wt% as a soft component An amorphous polycarbonate-based non-yellowing polyurethane resin obtained by polymerizing 55% by mass and polymerizing 4,4′-dicyclohexylmethane diisocyanate, a short-chain polyamine and a short-chain polyol as a hard component. The polyurethane elastic body A has a water absorption rate of 3% by mass, a storage elastic modulus at 23 ° C. of 300 MPa, a storage elastic modulus at 50 ° C. of 150 MPa, a glass transition temperature of −20 ° C., and the average particle size of the aqueous dispersion is 0.03 μm. is there. At this time, the solid content adhesion amount of the aqueous dispersion was 10% with respect to the mass of the web entangled sheet. The web-entangled sheet impregnated with the aqueous dispersion was dried and solidified at 90 ° C. in a 50% RH atmosphere, and further dried at 140 ° C. And it was hot-pressed at 140 ° C. to obtain a sheet having a basis weight of 1370 g / m ² , an apparent density of 0.76 g / cm ³ and a thickness of 1.8 mm.

Next, the web entangled sheet filled with the polyurethane elastic body A is immersed in 95 ° C. hot water for 10 minutes while being subjected to nip treatment and high-pressure water flow treatment to dissolve and remove the PVA-based resin, and further dried. As a result, a composite of polyurethane elastic body A and fiber entangled body having an average fineness of ultrafine fibers of 0.05 dtex, a basis weight of 1220 g / m ² , an apparent density of 0.66 g / cm ³ , and a thickness of 1.85 mm is obtained. It was.

Then, the composite was impregnated with an aqueous dispersion of polyurethane elastic body B (solid content concentration 30% by mass) as a second polyurethane elastic body. The polyurethane elastic body B comprises 99.9: 0.1 (molar ratio) of an amorphous polycarbonate-based polyol (copolymer polyol composed of hexamethylene carbonate and pentamethylene carbonate) and a polyalkylene glycol having 2 to 3 carbon atoms. ), 50% by mass of a soft component containing 1.5% by mass of a carboxyl group-containing monomer (2,2-bis (hydroxymethyl) propionic acid) is used as a hard component. A crosslinked structure is obtained by adding 5 parts by mass of a carbodiimide-based crosslinking agent to 100 parts by mass of a polycarbonate-based non-yellowing polyurethane resin obtained by polymerizing '-dicyclohexylmethane diisocyanate, a short-chain amine and a short-chain diol, and then heat-treating. Is a polyurethane resin formed. The polyurethane elastic body B has a water absorption rate of 2% by mass, a storage elastic modulus at 23 ° C. of 450 MPa, a storage elastic modulus at 50 ° C. of 300 MPa, a glass transition temperature of −25 ° C., and the average particle size of the aqueous dispersion is 0.05 μm. there were. At this time, the solid content adhesion amount of the aqueous dispersion was 15% by mass relative to the mass of the composite. Next, the composite impregnated with the aqueous dispersion was coagulated in an atmosphere of 90 ° C. and 50% RH, and further dried at 140 ° C. Then, it was hot pressed at 140 ° C. to obtain a polishing pad precursor. The obtained polishing pad precursor had a basis weight of 1390 g / m ² , an apparent density of 0.80 g / cm ³ , and a thickness of 1.75 mm.

  In addition, the obtained polishing pad precursor was obtained by concentrating all 50 ultrafine fibers constituting the ultrafine fiber bundle, and further having a polymer elastic body inside the ultrafine fiber bundle to restrain the ultrafine fiber bundle. It was.

The obtained polishing pad precursor was ground for surface flattening to obtain a flattened pad having a basis weight of 1120 g / m ² , an apparent density of 0.80 g / cm ³ , and a thickness of 1.4 mm. . Further, a circular polishing pad was obtained by cutting into a circular shape having a diameter of 51 cm and forming grooves having a width of 2.0 mm and a depth of 1.0 mm on the surface in a lattice shape at intervals of 15.0 mm. The mass ratio of the fiber entangled body and the polyurethane elastic body was 76/24, and the ratio of the polymer elastic body A and the polymer elastic body B was 40/60. The obtained polishing pad was evaluated by the evaluation method described later. The results are shown in Table 1.

[Example 2]
The same process as in Example 1 was performed until the web entangled sheet was created. Next, the web-entangled sheet that has been hot-pressed without impregnating the polyurethane elastic body A is immersed in hot water at 95 ° C. for 10 minutes to dissolve and remove the PVA-based resin, thereby removing the fiber bundle of ultrafine fibers. The resulting fiber entanglement was obtained. Then, the obtained fiber entangled body was impregnated with an aqueous dispersion of polyurethane elastic body B (solid content concentration: 40% by mass). At this time, the solid content adhesion amount of the aqueous dispersion was 20% by mass with respect to the mass of the fiber entangled body. Next, the fiber entangled body impregnated with the aqueous dispersion was coagulated at 90 ° C. in a 50% RH atmosphere. And after drying at 140 degreeC, the polishing pad precursor was obtained by further hot-pressing at 140 degreeC. The obtained polishing pad precursor was post-processed in the same manner as in Example 1 to obtain a flattened pad having a basis weight of 1080 g / m ² , an apparent density of 0.77 g / cm ³ , and a thickness of 1.4 mm. A circular polishing pad was obtained after groove processing. In the obtained polishing pad, all 50 ultrafine fibers constituting the ultrafine fiber bundle were converged, and a polymer elastic body was present inside the ultrafine fiber bundle, and the ultrafine fiber bundle was restrained. The obtained polishing pad was evaluated by the evaluation method described later. The results are shown in Table 1.

[Example 3]
A polishing pad was obtained in the same manner as in Example 1 except that the hot pressing treatment before impregnation with the polyurethane elastic body A and after impregnation and drying was not performed.

The obtained polishing pad precursor had a basis weight of 1360 g / m ² , an apparent density of 0.62 g / cm ³ , a thickness of 2.2 mm, and a mass ratio of the fiber entangled body and the polyurethane elastic body was 70/30. In addition, the obtained polishing pad precursor was obtained by concentrating all 50 ultrafine fibers constituting the ultrafine fiber bundle, and further having a polymer elastic body inside the ultrafine fiber bundle to restrain the ultrafine fiber bundle. It was. This was evaluated by the evaluation method described later on a polishing pad obtained by performing planarization and groove processing in the same manner as in Example 1. The results are shown in Table 1.

[Example 4]
As the first polyurethane elastic body, instead of the polyurethane elastic body A, a polyether-based polyalkylene glycol and a polycarbonate-based polyol are mixed at a 88:12 (molar ratio), and a carboxyl group-containing monomer (2,2-bis A polyol component containing 1.2 wt% of (hydroxymethyl) propionic acid) is used as a soft component in an amount of 58 mass%, and as a hard component, isophorone diisocyanate, a short chain polyamine, and a short chain polyol are polymerized. Polycarbonate non-yellowing polyurethane elastic body C (water absorption 4%, storage elastic modulus at 23 ° C. is 250 MPa, storage elastic modulus at 50 ° C. is 100 MPa, glass transition temperature is −30 ° C., and the average particle size of the aqueous dispersion is 0. 03 μm) and the polyurethane elastic body B is used as the second polyurethane elastic body. In addition, the polyurethane elastic body D obtained by increasing the polyol component of the polyurethane elastic body B by 10% by mass and the polyol component with respect to the polyurethane elastic body by 60% by mass (water absorption 4%, storage elasticity at 23 ° C.) A polishing pad was prepared in the same manner as in Example 1 except that the modulus was 300 MPa, the storage elastic modulus at 50 ° C. was 125 MPa, the glass transition temperature was −30 ° C., and the average particle size of the aqueous dispersion was 0.05 μm. did. In the obtained polishing pad, all 50 ultrafine fibers constituting the ultrafine fiber bundle were converged, and a polymer elastic body was present inside the ultrafine fiber bundle, and the ultrafine fiber bundle was restrained. And the obtained polishing pad was evaluated by the evaluation method mentioned later. The results are shown in Table 1.

[Example 5]
A polishing pad was obtained in the same manner as in Example 1 except that the PVA-based resin and the modified PET were discharged from a base having 9 islands / fibers at a ratio of 20:80 (mass ratio) and melt-spun. It was. The average fineness of the ultrafine fibers was 0.28 dtex. Further, the obtained polishing pad was one in which all nine ultrafine fibers constituting the ultrafine fiber bundle were converged, and the polymer elastic body was present inside the ultrafine fiber bundle, thereby restraining the ultrafine fiber bundle. The obtained polishing pad was evaluated by the evaluation method described later. The results are shown in Table 1.

[Example 6]
Using the polishing pad obtained in Example 1, the polishing performance of the polishing pad was evaluated in the same manner except that the polishing conditions in the polishing performance evaluation of the polishing pad described later were changed as follows. The polishing conditions are as follows.

(1) Evaluation was made in the same manner except that the silicon wafer having an oxide film was changed to a bare silicon wafer and the slurry used for polishing was changed to Granzox 1103 made by Fujimi.

(2) The slurry used for polishing was evaluated in the same manner except that the slurry was changed to Showa Denko polishing slurry GPL-C1010 and the slurry flow rate was changed to 200 ml.

(3) Evaluation was made in the same manner except that the wafer was changed to a tungsten wafer, and the slurry used for polishing was changed to Cabot W-2000 (34 g hydrogen peroxide added to 1030 g slurry).

(4) The evaluation was made in the same manner except that the wafer was changed to a GaAs wafer, the slurry used for polishing was changed to INSEC-FP manufactured by Fujimi, and the polishing pressure was changed to 20 kPa.

  The results are shown in Table 3.

[Example 7]
The same procedure as in Example 1 was performed until the polyurethane elastic body A was impregnated and dried and solidified inside the hot-pressed web entangled sheet (weight per unit area 1280 g / m ² , apparent density 0.56 g / cm ³ , thickness 2.3 mm). The sheet having a basis weight of 1340 g / m ² , an apparent density of 0.69 g / cm ³ , and a thickness of 1.95 mm was obtained without performing the heating press.

Next, the web entangled sheet filled with the polyurethane elastic body A is immersed in 95 ° C. hot water for 10 minutes while being subjected to nip treatment and high-pressure water flow treatment to dissolve and remove the PVA-based resin, and further dried. Thus, a composite of the polyurethane elastic body A and the fiber entangled body having an average fineness of the ultrafine fiber of 0.05 dtex, a basis weight of 1050 g / m ² , an apparent density of 0.57 g / cm ³ , and a thickness of 1.85 mm is obtained. It was.

And the polishing pad precursor was obtained by impregnating the elastic body with polyurethane elastic body B as the second polyurethane elastic body, solidifying and drying the composite, and not performing hot pressing. The obtained polishing pad precursor had a basis weight of 1170 g / m ² , an apparent density of 0.60 g / cm ³ , and a thickness of 1.95 mm.

The obtained polishing pad precursor was ground for surface flattening to obtain a flattened pad having a basis weight of 1000 g / m ² , an apparent density of 0.57 g / cm ³ , and a thickness of 1.75 mm. . Further, a circular polishing pad was obtained by cutting into a circular shape having a diameter of 51 cm and forming grooves having a width of 2.0 mm and a depth of 1.0 mm on the surface in a lattice shape at intervals of 15.0 mm. The mass ratio of the fiber entangled body and the polyurethane elastic body was 76/24, and the ratio of the polymer elastic body A and the polymer elastic body B was 40/60. The obtained polishing pad was evaluated by the evaluation method described later. The results are shown in Table 1.

[Example 8]
Using the polishing pad obtained in Example 7, polishing was performed in the same manner except that the polishing conditions in the polishing performance evaluation of the polishing pad described later were changed in the same manner as in (1) to (3) of Example 6. The polishing performance of the pad was evaluated.

  The results are shown in Table 4.

[Comparative Example 1]
By spinning Ny6, Ny long fibers with an average fineness of 2 dtex are melt spun, and the resulting long fibers are collected on a net to obtain a spunbond sheet (long fiber web) with a basis weight of 30 g / m ² Got.

A superposed web was prepared from the obtained spunbond sheet in the same manner as in Example 2. And the web entangled sheet was obtained by carrying out the needle punch process and entangled the obtained overlapping web similarly to Example 1. FIG. The basis weight of the obtained web entangled sheet was 800 g / m ² . Next, a web entangled sheet having an apparent density of 0.42 g / cm ³ and a thickness of 1.9 mm was obtained by hot pressing at 140 ° C.

Next, the hot-pressed web entangled sheet was impregnated with an aqueous dispersion of polyurethane elastic body B (solid content concentration 30 mass%). At this time, the solid content adhesion amount of the aqueous dispersion was 20% by mass relative to the mass of the web entangled sheet. The web entangled sheet impregnated with the aqueous dispersion was coagulated at 90 ° C. and 90% RH atmosphere, further dried at 140 ° C., and then hot-pressed at 140 ° C., with a basis weight of 920 g / m. ² , a polishing pad precursor with an apparent density of 0.54 g / m ² and a thickness of 1.7 mm was obtained. Then, a buffing process was performed to flatten the front surface and the back surface to obtain a polishing pad. The obtained polishing pad was evaluated by an evaluation method described later. The results are shown in Table 2.

[Comparative Example 2]
Instead of forming a polyurethane elastic body using an aqueous dispersion of polyurethane elastic body A as a polymer elastic body, an aqueous dispersion of polyurethane elastic body E (solid content concentration 20% by mass) was impregnated. The polyurethane elastic body E is a polyol (60% by mass with respect to the polyurethane elastic body) in which polyethylene glycol / polytetramethylene glycol is mixed at 15/85, isophorone diisocyanate, short chain polyamine and short chain polyol as hard components. Is a non-yellowing polyurethane resin obtained by polymerizing The polyurethane elastic body E has a water absorption of 12% by mass, a storage elastic modulus at 23 ° C. of 200 MPa, a storage elastic modulus at 50 ° C. of 80 MPa, a glass transition temperature of −48 ° C., and the average particle size of the aqueous dispersion is 0.4 μm. there were. Otherwise, a polishing pad was prepared in the same manner as in Example 2. The obtained polishing pad was evaluated by the evaluation method described later. The results are shown in Table 2.

[Comparative Example 3]
Polyurethane elastic body F obtained by increasing the polyol component of polyurethane elastic body B to 65% by mass (water absorption 8%, storage elastic modulus at 23 ° C. is 80 MPa, storage elastic modulus at 50 ° C. is 30 MPa, glass transition temperature is A polishing pad was prepared in the same manner as in Example 2 except that −32 ° C. and the average particle size of the aqueous dispersion was 0.02 μm. The obtained polishing pad was evaluated by the evaluation method described later. The results are shown in Table 2.
[Comparative Example 4]
Polyurethane elastic body B polyol component is hexamethylene carbonate diol, soft (polyol) component is used in 30% by mass, and 4,4′-dicyclohexylmethane diisocyanate, short chain amine and short chain diol are polymerized as hard component. Polyurethane elastic body G (water absorption 1%, storage elastic modulus at 23 ° C. is 1000 MPa, storage elastic modulus at 50 ° C. is 200 MPa, glass transition temperature is 0 ° C., average particle size of aqueous dispersion is 0.08 μm) A polishing pad was prepared in the same manner as in Example 2 except that. The obtained polishing pad was evaluated by the evaluation method described later. The results are shown in Table 2.

  The obtained polishing pad was evaluated by the following evaluation method.

[Evaluation method]
(1) Confirmation of average fineness of ultrafine fibers and converging state of ultrafine fibers inside fiber bundle The obtained polishing pad was cut in the thickness direction using a cutter blade to form a cut surface in the thickness direction. The obtained cut surface was stained with osmium oxide. Then, the cut surface was observed with a scanning electron microscope (SEM) at 500 to 1000 times, and an image thereof was taken. And the cross-sectional area of the ultrafine fiber which exists in a cut surface was calculated | required from the obtained image. A value obtained by averaging 100 randomly selected cross-sectional areas was defined as an average cross-sectional area, and the density was calculated from the density of the resin forming the fiber. In addition, by observing the obtained image, the case where the state in which not only the ultrafine fibers constituting the outer periphery of the fiber bundle but also the internal ultrafine fibers are bonded and integrated by the polymer elastic body is focused. "No" when the polymer elastic body does not exist inside the fiber bundle or only a few exist, and the state where the ultrafine fibers are hardly bonded and integrated is not focused. It was judged.

(2) Storage elastic modulus of polymer elastic body at 23 ° C. and 50 ° C. A film sample having a length of 4 cm × width 0.5 cm × thickness 400 μm ± 100 μm was prepared from the polymer elastic body constituting the polishing pad. Then, after measuring the sample thickness with a micrometer, using a dynamic viscoelasticity measuring device (DVE Rheospectr, manufactured by Rheology Co., Ltd.), the temperature is 23 ° C. under conditions of a frequency of 11 Hz and a temperature rising rate of 3 ° C./min. The dynamic viscoelastic modulus at 50 ° C. was measured, and the storage elastic modulus was calculated. In addition, when using 2 types of polymer elastic bodies, the sample was created and measured separately, respectively, and the sum multiplied by the mass ratio was used as the storage elastic modulus of the polymer elastic body.

(3) Glass transition temperature of polymer elastic body A film having a length of 4 cm, a width of 0.5 cm, and a thickness of 400 μm ± 100 μm was prepared from the polymer elastic body constituting the polishing pad. Then, after measuring the sample thickness with a micrometer, using a dynamic viscoelasticity measuring device (DVE Rheospectr, manufactured by Rheology Co., Ltd.) Viscoelasticity was measured, and the main dispersion peak temperature of the loss elastic modulus was taken as the glass transition temperature. In addition, when using 2 types of polymer elastic bodies, the sample was created and measured separately, respectively, and the sum which multiplied the mass ratio was made into the glass transition temperature of a polymer elastic body.

(4) Water absorption rate when polymer elastic body is saturated with water absorption at 50 ° C. A 200 μm thick film obtained by drying polymer elastic body at 50 ° C. is heat-treated at 130 ° C. for 30 minutes, then 20 A sample left for 3 days under conditions of 65 ° C. and 65% RH was used as a dry sample, and the dry sample was immersed in water at 50 ° C. for 2 days. And immediately after taking out from 50 degreeC water, the thing after wiping off the excess water drop etc. of the outermost surface of a film with JK wiper 150-S (made by Crecia Corporation) was used as the water swelling sample. The masses of the dried sample and the water-swelled sample were measured, and the water absorption rate was determined according to the following formula.

Water absorption (mass%) = [(mass of water swollen sample−mass of dry sample) / mass of dry sample] × 100
In addition, when using 2 types of polymer elastic bodies, a sample was created and measured separately, respectively, and the sum of the weight ratio was used as the water absorption rate of the polymer elastic body.

(5) Water absorption rate when water is saturated at 50 ° C (water absorption rate when the thermoplastic resin constituting the ultrafine fiber is water saturated at 50 ° C)
A film having a thickness of 200 μm obtained by hot pressing the thermoplastic resin constituting the ultrafine fibers at a temperature of melting point + 20-100 ° C. was heat-treated at 130 ° C. for 30 minutes. Then, what was left to stand on 20 degreeC and 65% RH conditions for 3 days was made into the dry sample. After the dried sample is immersed in water at 50 ° C. for 2 days, the excess water droplets etc. on the outermost surface of the film immediately after taking out from the water are wiped with JK Wiper 150-S (manufactured by Crecia Co., Ltd.). A swollen sample was obtained. The masses of the dried sample and the water-swelled sample were measured, and the water absorption rate was determined according to the following formula.

  Water absorption (mass%) = [(mass of water swollen sample−mass of dry sample) / mass of dry sample] × 100

(6) Average particle diameter of aqueous polyurethane Measured by dynamic light scattering method using “ELS-800” manufactured by Otsuka Chemical Co., Ltd., cumulant method (“Colloid Chemistry Volume IV Colloid Chemistry Experimental Method” The average particle size of the water-dispersed polymer elastic body was measured.When two types of polymer elastic bodies were used, the sample was measured separately and the sum of the mass ratio was multiplied. Is the value of the average particle size of the polymer elastic body.

(7) Apparent density of polishing pad and porosity of polishing pad (volume ratio of void portion of polishing pad)
The apparent density of the resulting polishing pad was measured according to JIS L1096. On the other hand, the theoretical density of the composite of the fiber entangled body and the polymer elastic body in the absence of voids was calculated from the constituent ratio of each constituent constituting the polishing pad and the density of each constituent. Then, the ratio of the apparent density to the theoretical density is regarded as the volume ratio of the filling portion of the polishing pad, and [1− (the ratio of the apparent density to the theoretical density)] × 100 (%) is determined as the gap of the polishing pad. Rate (volume ratio of the void portion of the polishing pad). In addition, the density of each component used in Example 1 is a modified PET (1.38 g / cm ³ ), a polyurethane elastic body (1.05 g / cm ³ ), and a PVA resin (1.25 g / cm ³ ). .

(8) Polishing performance evaluation of polishing pad After sticking an adhesive tape on the back surface of a circular polishing pad, it was mounted on a CMP polishing apparatus ("PP0-60S" manufactured by Nomura Seisakusho Co., Ltd.). Then, using a diamond dresser with count # 200 (MEC200L manufactured by Mitsubishi Materials Corporation), a polishing pad for 18 minutes while flowing distilled water at a rate of 120 mL / min under conditions of a pressure of 177 kPa and a dresser rotation speed of 110 rpm Conditioning (seasoning) was performed by grinding the surface.

  Next, a diameter having an oxide film surface is supplied while supplying Cabot abrasive slurry SS12 at a rate of 120 ml / min under the conditions of a platen rotation speed of 50 rotations / minute, a head rotation speed of 49 rotations / minute, and a polishing pressure of 35 kPa. A 6 inch silicon wafer was polished for 100 seconds. And the thickness of arbitrary 49 points in the silicon wafer surface which has the oxide film surface after grinding | polishing was measured, and the polishing rate (nm / min) was calculated | required by remove | dividing the polished thickness in each point by grinding | polishing time. . The average value of the 49 polishing rates was defined as the polishing rate (R), and its standard deviation (σ) was determined.

  And flatness was evaluated by the following formula. In addition, it shows that it is excellent in planarization performance, so that the value of flatness is small.

      Flatness (%) = (σ / R) × 100

  Next, the polished polishing pad was left in a wet state at 25 ° C. for 24 hours. Then, after performing seasoning, the polishing rate (R) and flatness after polishing again were determined.

  Further, seasoning and polishing were alternately repeated 300 times, and the polishing rate (R) and flatness at the 300th polishing were determined.

  Further, by measuring the number of scratches having a size of 0.16 μm or more present on the surface of the silicon wafer having the oxide film after polishing, using a wafer surface inspection apparatus Surfscan SP1 (manufactured by KLA-Tencor) The scratch property was evaluated.

(9) Polishing Performance Evaluation of Polishing Pad in Bare Silicon Wafer Polishing After attaching an adhesive tape to the back surface of the circular polishing pad, it was attached to a CMP polishing apparatus (“PP0-60S” manufactured by Nomura Seisakusho Co., Ltd.). Then, using a diamond dresser with count # 200 (MEC200L manufactured by Mitsubishi Materials Corporation), a polishing pad for 18 minutes while flowing distilled water at a rate of 120 mL / min under conditions of a pressure of 177 kPa and a dresser rotation speed of 110 rpm Conditioning (seasoning) was performed by grinding the surface.

  Next, a silicon wafer with a diameter of 6 inches was supplied while supplying Granzox 1103 manufactured by Fujimi Incorporated at a rate of 120 ml / min under the conditions of a platen rotation speed of 50 rotations / minute, a head rotation speed of 49 rotations / minute, and a polishing pressure of 35 kPa. Was polished for 100 seconds. And the thickness of 49 points | pieces in the silicon | silicone wafer surface after grinding | polishing was measured, and the grinding | polishing rate (nm / min) was calculated | required by remove | dividing the polished thickness in each point by grinding | polishing time. The average value of the 49 polishing rates was defined as the polishing rate (R), and its standard deviation (σ) was determined.

  And flatness was evaluated by the following formula. In addition, it shows that it is excellent in planarization performance, so that the value of flatness is small.

      Flatness (%) = (σ / R) × 100

  Next, the polished polishing pad was left in a wet state at 25 ° C. for 24 hours. Then, after performing seasoning, the polishing rate (R) and flatness after polishing again were determined.

  Further, seasoning and polishing were alternately repeated 300 times, and the polishing rate (R) and flatness at the 300th polishing were determined.

  The results for Examples 1-5 and 7 are in Table 1, the results for Example 6 are in Table 3, the results for Example 8 are in Table 4, and the results for Comparative Examples 1-4 are in Table 2. , Respectively.

  As described above, one aspect of the present invention is a polishing pad comprising an ultrafine fiber entangled body formed from ultrafine fibers having an average fineness of 0.01 to 0.8 dtex, and a polymer elastic body, The polymer elastic body has a glass transition temperature of −10 ° C. or lower, a storage elastic modulus at 23 ° C. and 50 ° C. of 90 to 900 MPa, and a water absorption of 0.2 to 0.2 when saturated with water absorption at 50 ° C. The polishing pad is 5% by mass.

  According to the said structure, the polishing pad which can perform the grinding | polishing which obtains high flatness stably for a long time, suppressing generation | occurrence | production of a scratch is obtained.

  The ultrafine fiber entangled body is preferably composed of an ultrafine fiber bundle in which 5 to 70 ultrafine fibers are converged, and the polymer elastic body is preferably present in the ultrafine fiber bundle.

  According to the above configuration, the ultrafine fibers are focused by the polymer elastic body, and the bundle of ultrafine fibers is constrained, so that the rigidity of the polishing pad is increased, and the planarization performance, polishing uniformity and stability over time are improved. Can do.

  The ultrafine fibers are preferably formed from polyester fibers from the viewpoint of forming a dense and high density fiber entangled body.

  Moreover, it is preferable that the said ultrafine fiber is formed from the thermoplastic resin whose water absorption is 0.2-2 mass% when water-absorbing and saturated at 50 degreeC.

  According to the above-described configuration, it is possible to obtain a polishing pad that suppresses a decrease in planarization performance with time and hardly changes the polishing rate and polishing uniformity.

  The polymer elastic body is a polyurethane-based resin obtained using a polyol, a polyamine, and a polyisocyanate, and 60 to 100% by mass of the polyol is preferably an amorphous polycarbonate-based diol.

  According to the said structure, since the tolerance with respect to the slurry used by grinding | polishing is high, the temporal stability during grinding | polishing can be maintained favorable.

  The polymer elastic body is preferably a polyurethane-based resin obtained by using an amorphous polycarbonate diol as a polyol together with a carboxyl group-containing diol and using an alicyclic diisocyanate as the polyisocyanate.

  According to the said structure, when the glass transition temperature of a polymeric elastic body is -10 degrees C or less, the storage elastic modulus in 23 degreeC and 50 degreeC is 90-900 Mpa, and water absorption is 50.degree. It can be easily adjusted to 2 to 5% by mass.

  The polymer elastic body preferably has a ratio of storage elastic modulus at 23 ° C. to storage elastic modulus at 50 ° C. (storage elastic modulus at 23 ° C./storage elastic modulus at 50 ° C.) of 4 or less.

  According to the above configuration, since the storage elastic modulus hardly changes even when the temperature changes during polishing, stability over time during polishing can be improved.

  Further, the polymer elastic body is preferably an aqueous polyurethane having an average particle diameter of 0.01 to 0.2 μm from the viewpoint of obtaining good water resistance and improving the binding force of the fiber bundle.

  When the ratio of the ultrafine fiber entangled body to the polymer elastic body (ultrafine fiber entangled body / polymer elastic body) is 55/45 to 95/5 by mass ratio, the polishing efficiency is improved. And it is preferable from the point that pad wear during polishing becomes small.

  Furthermore, it is preferable that the volume ratio of the space | gap part in a polishing pad is 50% or more.

  According to the said structure, since a polishing pad has slurry retention property, moderate rigidity, and cushioning properties, it can be preferably used for bare silicon wafer polishing.

  Another aspect of the present invention is that the glass transition temperature is not higher than −10 ° C. and stored at 23 ° C. and 50 ° C. inside the ultrafine fiber bundle in which ultrafine fibers having an average fineness of 0.01 to 0.8 dtex are converged. A method for producing a polishing pad comprising filling a polymer elastic body having an elastic modulus of 90 to 900 MPa and a water absorption of 0.2 to 5% by mass when saturated with water at 50 ° C.

  According to such a manufacturing method, it is possible to obtain a polishing pad having high rigidity, high abrasive slurry retention, and hardly causing scratches on the substrate to be polished.

  Further, in the manufacturing method of the polishing pad, inside the ultrafine fiber entangled body composed of the ultrafine fiber bundle in which the ultrafine fibers are converged so that the volume ratio of the void portion in the polishing pad is 50% or more, It is preferable to fill the polymer elastic body.

  According to the above configuration, by adjusting the amount of the polymer elastic body filled in the ultrafine fiber entangled body, the porosity of the polishing pad is set to 50% or more, so that an appropriate rigidity and abrasive slurry retention property can be obtained. A polishing pad suitable for bare silicon wafer polishing with improved cushioning properties can be obtained.

  The polishing pad according to the present invention includes various products such as flattened and mirror-finished devices and various substrates, such as semiconductor substrates, semiconductor devices, compound semiconductor devices, compound semiconductor substrates, compound semiconductor products, LED substrates, and LEDs. It can be used as a polishing pad for polishing products, silicon wafers, hard disk substrates, glass substrates, glass products, metal substrates, metal products, plastic substrates, plastic products, ceramic substrates, ceramic products and the like.

Claims (12)

An ultrafine fiber entangled body formed from ultrafine fibers having an average fineness of 0.01 to 0.8 dtex, and a polymer elastic body, the polymer elastic body focuses the ultrafine fibers and constrains the ultrafine fiber bundle, The polymer elastic body has a glass transition temperature of −10 ° C. or lower, a storage elastic modulus at 23 ° C. and 50 ° C. of 90 to 900 MPa, and a water absorption rate of 0.2 when water absorption is saturated at 50 ° C. A polishing pad, which is ˜5 mass%.   2. The polishing pad according to claim 1, wherein the ultrafine fiber entangled body is composed of an ultrafine fiber bundle in which 5 to 70 ultrafine fibers are converged, and the polymer elastic body is present in the ultrafine fiber bundle. .   The polishing pad according to claim 1, wherein the ultrafine fiber is formed from a polyester fiber.   The polishing pad according to any one of claims 1 to 3, wherein the ultrafine fiber is formed from a thermoplastic resin having a water absorption rate of 0.2 to 2 mass% when saturated with water absorption at 50 ° C.   The polymer elastic body is a polyurethane resin obtained by using a polyol, a polyamine, and a polyisocyanate, and 60 to 100% by mass of the polyol is an amorphous polycarbonate diol. The polishing pad according to claim 1. 6. The polishing according to claim 5, wherein the polymer elastic body is a polyurethane resin obtained by using an amorphous polycarbonate diol as a polyol together with a carboxyl group-containing diol and using an alicyclic diisocyanate as the polyisocyanate. pad.   7. The polymer elastic body has a ratio of a storage elastic modulus at 23 ° C. to a storage elastic modulus at 50 ° C. (storage elastic modulus at 23 ° C./storage elastic modulus at 50 ° C.) of 4 or less. 2. The polishing pad according to item 1.   The polishing pad according to claim 1, wherein the polymer elastic body is an aqueous polyurethane having an average particle diameter of 0.01 to 0.2 μm.   The ratio between the ultrafine fiber entangled body and the polymer elastic body (ultrafine fiber entangled body / polymer elastic body) is 55/45 to 95/5 in mass ratio. The polishing pad described in 1.   The polishing pad according to any one of claims 1 to 9, wherein a volume ratio of a void portion in the polishing pad is 50% or more. Inside the ultrafine fiber bundle in which ultrafine fibers having an average fineness of 0.01 to 0.8 dtex are focused, the glass transition temperature is −10 ° C. or lower, the storage elastic modulus at 23 ° C. and 50 ° C. is 90 to 900 MPa, and 50 ° C. The method for producing a polishing pad according to claim 1 , wherein a polymer elastic body having a water absorption rate of 0.2 to 5 mass% when saturated with water is saturated.   The polymer elastic body is filled in an ultrafine fiber entangled body composed of an ultrafine fiber bundle in which the ultrafine fibers are converged so that a volume ratio of a void portion in a polishing pad is 50% or more. The manufacturing method of the polishing pad of description.