JP2015100894A - Polishing pad and method of manufacturing the polishing pad - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing pad which exhibits high planarization efficiency and also an excellent low scratching property, and can be used for a long period of time without wear and clog.SOLUTION: A polishing pad includes a sheet, as a polishing layer, having a void ratio of 5-35% which is formed by adhering a plurality of wet-heat adhesive fibers containing wet-heat adhesive resin which exhibits adhesiveness by wet-heat treatment. Thereby, as the entire polishing pad, high hardness is maintained to maintain high planarization efficiency, and a low scratching property can be secured by decreasing an elastic modulus of the only polishing surface.

Description

  The present invention relates to a polishing pad preferably used for polishing a substrate such as a semiconductor wafer or a semiconductor device, and a method for manufacturing the polishing pad.

  Conventionally, a polishing pad is used in a polishing process for mirror-finishing a semiconductor wafer or a glass wafer, or for flattening unevenness due to an insulating film or a metal film in a semiconductor device manufacturing process. In particular, in the manufacture of semiconductor devices, the performance of flattening the surface of a material to be polished (hereinafter also referred to as the surface to be polished) with a small amount of polishing and a short polishing time with the progress of high integration and multilayer wiring in recent years. Thus, there is a demand for improvement in flattening efficiency and low scratch property, which is a performance that hardly damages the surface to be polished during polishing.

  As a polishing pad, a non-woven type polishing pad in which a non-woven fabric is impregnated with a polyurethane resin, or a foamed polyurethane type polishing pad manufactured by grinding or slicing appropriately after casting and foaming using a two-component curable polyurethane. It has been known. In general, a non-woven fabric type polishing pad has low elasticity and is soft, and a foamed polyurethane type polishing pad has high elasticity and high rigidity.

  A conventional non-woven fabric type polishing pad is superior to a foamed polyurethane type polishing pad in that the surface in contact with the surface to be polished (hereinafter also referred to as the polishing surface) is flexible and therefore has low scratch properties on the surface to be polished. However, the flattening efficiency was low due to the low elasticity.

  On the other hand, polyurethane foam type polishing pads have high leveling efficiency due to their high rigidity, but on the other hand, they are less scratching because they tend to apply local loads to the projections of the surface to be polished during polishing. It was inferior. In addition, foamed polyurethane has non-uniform reaction and foaming during manufacturing, and therefore the foamed structure tends to vary, and the variation in foamed structure causes variations in polishing characteristics such as polishing speed and planarization efficiency. There was also. Furthermore, due to the technical limit of improving the hardness of the polyurethane foam itself, it has been difficult to further improve the planarization efficiency.

  There is a need for a polishing pad that has both excellent planarization efficiency and low scratch resistance, which solves the respective problems of the nonwoven fabric type polishing pad and the foamed polyurethane type polishing pad. However, it has been difficult to satisfy this requirement with a foamed polyurethane type polishing pad or a conventional nonwoven fabric type polishing pad. In order to further improve the planarization efficiency of the foamed polyurethane type polishing pad, higher hardness is required. However, when the hardness of the polishing pad is increased, the low scratch property generally decreases. Therefore, in the foamed polyurethane type polishing pad, since there is a trade-off relationship between high planarization efficiency and excellent low scratch property, a polishing pad that has both excellent planarization efficiency and low scratch property is sufficient. It was difficult to get.

  As a technique for solving such a problem, the following Patent Document 1 and the following Patent Document 2 disclose a polishing pad in which a water-soluble substance is dispersed in a water-insoluble thermoplastic polymer. A polishing pad is disclosed in which water-soluble particles are dispersed in a water-insoluble matrix material containing a crosslinked polymer. However, these polishing pads have not been sufficient for achieving both high planarization efficiency and excellent low scratch properties. In addition, these polishing pads contain water-soluble substances, and these may elute during polishing and may adversely affect the polishing characteristics. Furthermore, since the water-soluble substance is easily dispersed in the matrix, the polishing characteristics are likely to vary.

  In recent semiconductor device manufacturing, in addition to the above-described high performance, it is also required to extend the life of the polishing pad to lower the polishing cost. A foamed polyurethane type polishing pad has a closed cell structure, so that it is difficult for polishing slurry and polishing debris to penetrate deeply, and cleaning and removal thereof are relatively easy, and thus have a long life. On the other hand, since the nonwoven fabric type polishing pad has a communication hole structure, the polishing slurry or the like penetrates deeply into the nonwoven fabric through the communication holes and easily clogs the voids existing on the polishing surface. There is also a problem that the life is short because it is difficult to remove the clogged polishing slurry. In addition, clogged polishing slurries and the like may damage the polished surface, which is a cause of lowering low scratch properties.

By the way, although it is not the technique regarding a polishing pad, the following patent document 4 is a molded object which contains a wet heat adhesive fiber, and has a nonwoven fiber structure, Comprising: The fiber which comprises a nonwoven fiber is the said wet heat adhesive fiber. Disclosed is a lightweight, highly breathable molded article that has been bonded to a fiber adhesion rate of 85% or less by fusion and has an apparent density of 0.05 to 0.7 g / cm ³ .

JP 2000-34416 A JP 2001-47355 A JP 2001-334455 A WO2007 / 116676 pamphlet

  The present invention has high planarization efficiency and excellent low scratch property, especially when polishing an insulating film or a metal film formed on a semiconductor substrate, glass, or the like, and wear of a pad. Another object of the present invention is to provide a polishing pad that can be used for a long time with little clogging.

  As described above, a polishing pad having high planarization efficiency is required to have high hardness as a whole polishing pad. However, in this case, since it becomes easy to apply a load locally to the convex portion of the surface to be polished, the low scratch property is lowered. As a result of repeated investigations to achieve the above object, the inventors of the present invention do not need to lower the hardness of the polishing pad as a whole in order to achieve excellent low scratch properties, and the elastic modulus near the surface of the polishing surface. I thought that it would be good to lower locally. That is, it was considered that the entire polishing pad could maintain high hardness and maintain high planarization efficiency, while ensuring low scratch properties by reducing the elastic modulus of only the polishing surface. Furthermore, the inventors have thought that stable polishing characteristics can be obtained by forming a uniform pore structure, and as a result of intensive studies, the present invention has been conceived.

  That is, one aspect of the present invention is polishing that includes, as a polishing layer, a sheet having a porosity of 5 to 35%, which is formed by fixing a plurality of wet and heat adhesive fibers including a wet and heat adhesive resin that exhibits adhesion by wet heat treatment. It is a pad. Such a polishing pad includes, as a polishing layer, a sheet having a low porosity formed by adhering a plurality of wet heat adhesive fibers containing a wet heat adhesive resin that exhibits adhesiveness by wet heat treatment. Such a sheet has a much lower porosity than a conventional non-woven fabric type polishing pad, so that the entire polishing layer has very high rigidity. Further, since a wet heat adhesive resin that absorbs water by wet heat treatment and exhibits adhesiveness is also present on the polished surface, only the very surface of the polishing layer is softened by water absorption during polishing. As a result, both high planarization efficiency and excellent low scratch properties can be achieved. Furthermore, since the porosity of the sheet is low, the communication holes are very few or almost absent, and the gaps on the polishing surface are not easily clogged with polishing slurry or the like.

  In addition, the sheet preferably has a D hardness of 60 to 80 on the polished surface from the viewpoint of obtaining a high polishing rate and being excellent in low scratch properties.

Further, in the image obtained by photographing the cross section with a scanning electron microscope, the ratio of the number of cross-sectional contours of fibers bonded to other fibers to the total number of cross-sectional contours of the fibers is 90% or more. Is preferred. Moreover, it is preferable that the sheet has an air permeability of 1 cm ³ / cm ² / sec or less according to the fragile method. In these cases, the wet and heat adhesive fibers adhere widely to the surface of the fibers and there are almost no communication holes, so that the polishing slurry or the like hardly penetrates into the deep part of the polishing layer. For this reason, the gaps in the polishing surface are less likely to be clogged, and the polishing slurry is easily supplied to the surface to be polished.

  Further, the wet heat adhesive resin is a saponified ethylene-vinyl ester copolymer having an ethylene copolymerization rate of 10 to 60 mol%, and exhibits good wet heat adhesiveness and high strength even when water is absorbed during polishing. And from the point of maintaining wear resistance.

  The wet heat adhesive fiber is a fiber containing a non-wet heat adhesive resin and a wet heat adhesive resin that do not exhibit adhesiveness by wet heat treatment, and the wet heat adhesive resin is a surface of a fiber made of the non-humid heat adhesive resin. And a sheath-core type in which the wet-heat adhesive fiber has a core portion made of a non-wet heat adhesive resin and a sheath portion made of a wet heat adhesive resin. A composite fiber is preferable from the viewpoint of high adhesion between fibers and less pad wear.

  Moreover, it is preferable that the average fineness of wet heat adhesive fiber is 0.1-10 dtex from the point which is excellent in a grinding | polishing speed and grinding | polishing uniformity.

  Moreover, it is preferable from the point which can improve polishing uniformity that the cushion layer is laminated | stacked on the opposite side to the grinding | polishing surface of a grinding | polishing layer.

  In addition, when polishing a constituent material of a semiconductor device, it is determined that the arithmetic average roughness (Ra) on the polishing surface side of the polishing layer is 1 to 6 μm and the maximum height (Rz) is 10 to 60 μm. It is preferable from the viewpoint of excellent speed, flatness, and level difference elimination.

  Another aspect of the present invention is a process for producing a fiber web containing a wet heat adhesive fiber containing a wet heat adhesive resin that exhibits adhesion by wet heat treatment, and forming the fiber web by wet heat treatment of the fiber web. Forming a non-woven fiber base material by bonding the fibers to be formed, and forming a sheet by heating and pressurizing the non-woven fiber base material so as to have a porosity of 5 to 35%. It is a manufacturing method of a polishing pad. According to such a manufacturing method, a polishing pad provided with the above-described sheet as a polishing layer can be obtained.

  According to the present invention, it is possible to obtain a polishing pad that has both high planarization efficiency and excellent low scratch properties and can be used for a long time with less pad wear and clogging. In particular, it is suitable for chemical mechanical polishing of a semiconductor substrate, glass, or an insulating film or a metal film formed thereon.

FIG. 1 is an SEM photograph of a cross section of the sheet 2 obtained in Production Example 2. FIG. 2 is an SEM photograph of a cross section of the sheet 3 obtained in Production Example 3. FIG. 3 is an SEM photograph of the cross section of the sheet 5 obtained in Production Example 5. FIG. 4 is an SEM photograph of a cross section of the polishing layer of the sheet 10 obtained in Comparative Production Example 3.

  An embodiment of a polishing pad according to the present invention will be described in detail.

  The polishing pad of this embodiment includes a sheet having a porosity of 5 to 35%, which is formed by fixing a plurality of wet heat adhesive fibers including a wet heat adhesive resin that exhibits adhesiveness by wet heat treatment, to each other as a polishing layer.

  The wet heat adhesive fiber is a fiber containing a wet heat adhesive resin that exhibits adhesiveness by wet heat treatment, for example, it is adhesive by wet heat treatment such as contacting with high temperature steam or hot water, or wet heat adhesive fibers, or It is a fiber that bonds wet heat adhesive fibers and non-wet heat adhesive fibers that do not exhibit adhesive properties by wet heat treatment. Since the wet heat adhesive resin is softened and flows or deforms by the wet heat treatment, the fibers can be firmly bonded to each other. The presence of the wet heat adhesive resin on the polishing surface of the resulting polishing layer absorbs the moisture of the polishing slurry and softens only the vicinity of the polishing surface, thereby suppressing the occurrence of scratches.

  Wet and heat-adhesive fibers are not composed of wet heat-adhesive resin alone or composite fibers composed of different kinds of wet and heat-adhesive resins. It may be a composite fiber formed by combining a non-wet heat adhesive resin and a wet heat adhesive resin. In addition, although the conditions of wet heat processing are not specifically limited, For example, 70-150 degreeC, Furthermore, 90-130 degreeC, Especially the conditions which are made to contact high temperature steam and hot water of about 100-120 degreeC are mentioned.

  Specific examples of the wet heat adhesive resin include, for example, 20 to 100 mol% of a vinyl ester group-containing monomer that forms a vinyl alcohol skeleton by hydrolysis and 80 to 0 mol of another monomer having an unsaturated double bond. % Of a polymer obtained by hydrolysis (saponification) of a polymer; 20 to 100% by mass of a monomer having at least one functional group selected from a carboxy group, a hydroxyl group, an ether group and an amide group; Resin obtained by polymerizing 80 to 0% by mass of other monomer having a saturated double bond; cellulose or derivative thereof; polyalkylene oxide such as polyethylene oxide and polypropylene oxide and resin having them in the skeleton; etc. Is mentioned.

  Specific examples of the vinyl ester group-containing monomer that forms a vinyl alcohol skeleton by hydrolysis include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, and the like. Specific examples of the other monomer having an unsaturated double bond include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (meth) acrylamide, N, N-dimethyl (meth) acrylamide, styrene, methyl vinyl ether, vinyl pyrrolidone, ethylene, propylene, butadiene and the like can be mentioned. Specific examples of the monomer having at least one functional group selected from a carboxy group, a hydroxyl group, an ether group, and an amide group include (meth) acrylic acid, (anhydrous) maleic acid, itaconic acid, (meta ) 2-hydroxyethyl acrylate, 4-hydroxystyrene, methyl vinyl ether, ethyl vinyl ether, (meth) acrylamide, N, N-dimethyl (meth) acrylamide, vinylpyrrolidone and the like. Specific examples of cellulose derivatives include alkyl cellulose ethers such as methyl cellulose, hydroxyalkyl cellulose ethers such as hydroxymethyl cellulose, carboxyalkyl cellulose ethers such as carboxymethyl cellulose, and salts thereof. Moreover, specific examples of polyalkylene oxides such as polyethylene oxide and polypropylene oxide and resins having these in the skeleton include polyester or polyurethane copolymerized with polyethylene glycol, polypropylene glycol, and the like. For example, a notation such as (meth) acrylic acid means methacrylic acid or acrylic acid. Therefore, the notation of (meth) acrylamide means methacrylamide or acrylamide.

  The wet heat adhesive resins as described above may be used alone or in combination of two or more. Among these, a polymer of 20 to 100 mol% of a vinyl ester group-containing monomer that forms a vinyl alcohol skeleton by hydrolysis and 80 to 0 mol% of another monomer having an unsaturated double bond is hydrolyzed. A polymer obtained by decomposition (saponification) is preferable in that it has excellent wet heat adhesion and maintains high strength and wear resistance even when water is absorbed during polishing. In addition, in the polymer of a vinyl ester group-containing monomer and another monomer, the vinyl ester unit in the main chain skeleton is converted into a vinyl alcohol unit by saponification.

  The copolymerization rate of other monomer units in the polymer containing a vinyl ester group-containing monomer unit that forms a vinyl alcohol skeleton by hydrolysis and other monomer units is 10 to 60 mol%. Furthermore, it is preferably 20 to 55 mol%, particularly 30 to 50 mol%.

  In addition, a polymer of 20 to 100 mol% of a vinyl ester group-containing monomer that forms a vinyl alcohol skeleton by hydrolysis and 80 to 0 mol% of another monomer having an unsaturated double bond is hydrolyzed (ken The polymer obtained by saponification is a saponified product of ethylene-vinyl ester copolymer (ethylene-vinyl alcohol copolymer (EVOH)) which is a saponified product of vinyl acetate and ethylene. Is particularly preferred.

  The copolymerization rate of EVOH ethylene units is preferably 10 to 60 mol%, more preferably 20 to 55 mol%, and particularly preferably 30 to 50 mol%. When the copolymerization rate of the ethylene unit is within such a range, a unique property that the hot water solubility is low despite the high wet heat adhesion is obtained. When the copolymerization rate of ethylene units is too low, EVOH that easily swells or gels in low-temperature water or aqueous slurry is obtained, and the polishing rate of the resulting polishing pad tends to decrease. Moreover, when the copolymerization rate of an ethylene unit is too high, wet heat adhesiveness falls by a hygroscopic fall, and there exists a tendency for the intensity | strength and abrasion resistance of the obtained polishing layer to fall. In addition, when the copolymerization rate of an ethylene unit is 30-50 mol%, it is preferable from the point which is especially excellent in durability of a polishing layer and polishing rate.

  Moreover, as a saponification degree (ratio which hydrolyzed) the vinyl ester unit in EVOH, it is 90-99.99 mol%, Furthermore, 93-99.9 mol%, Especially about 95-99.5 mol%. Preferably there is. When the degree of saponification is too low, thermal stability tends to decrease, so that thermal decomposition or gelation tends to occur during spinning. Further, when the degree of saponification is too high, productivity tends to decrease, for example, it takes a long time for saponification.

  Moreover, it is preferable that the wet heat adhesive fiber is a composite fiber of a wet heat adhesive resin and a non-wet heat adhesive resin from the viewpoint of easily adjusting the strength and hardness of the obtained sheet. Specific examples of the non-wet heat adhesive resin include, for example, polyester resins such as polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyolefin resins such as polypropylene resin; polyamide 6, polyamide 66, polyamide 610, polyamide 10, polyamide 12, polyamide 6-12, polyamide 9T, and other polyamide resins; (meth) acrylic resins; vinyl chloride resins; styrene resins; polycarbonate resins; polyurethane resins; Non water-soluble resin is mentioned. These may be used alone or in combination of two or more. Among these, polyester resins and polyamide resins, particularly polyethylene terephthalate, are particularly preferable because they have a higher melting point than wet heat adhesive resins such as EVOH and are excellent in balance between heat resistance and fiber-forming properties.

  When the wet heat adhesive fiber is a composite fiber, the wet heat adhesive resin is preferably attached to the surface of the fiber made of the non-wet heat adhesive resin so as to be continuous in the longitudinal direction. Moreover, as a phase structure of the cross section of a composite fiber, a core-sheath type, a sea-island type, a side-by-side type or a multilayer bonding type, a radial bonding type, a random composite type, etc. are mentioned, for example. Among these, the wet-heat adhesive resin forms the sheath, the non-wet heat-adhesive resin or other wet heat-adhesive resin fibers form the core, and the wet-heat adhesive resin covers the fiber surface. It is preferable from a point with high wet heat adhesiveness. Further, the wet heat adhesive fiber may be a fiber formed by coating a wet heat adhesive resin on the surface of the non-wet heat adhesive fiber.

  When the wet heat adhesive fiber is a composite fiber of a wet heat adhesive resin and a non-wet heat adhesive resin, the composite ratio of the wet heat adhesive resin and the non-wet heat adhesive resin is not particularly limited as long as the wet heat adhesive property is maintained, It adjusts suitably according to the cross-sectional structure etc. of a composite fiber. Specifically, for example, the wet heat adhesive resin / non-wet heat adhesive resin is 10/90 to 90/10, further 15/85 to 85/15, particularly 20/80 to 80/20. It is preferable that it is about 30 / 70-70 / 30. In addition, when the ratio of the wet heat adhesive resin is too small, it becomes difficult to cover the surface continuously and uniformly in the longitudinal direction of the fiber, and the amount of wet heat adhesive resin showing adhesiveness is reduced. There exists a tendency for wet heat adhesiveness to fall. Moreover, when there is too much ratio of wet heat adhesive resin, there exists a tendency for the intensity | strength and durability improvement effect by compounding with non-wet heat adhesive resin to fully be acquired.

  The number of crimps of the wet heat adhesive fiber is, for example, preferably about 1 to 100 pieces / 25 mm, more preferably 5 to 50 pieces / 25 mm, and particularly preferably about 10 to 30 pieces / 25 mm.

  As the fiber component for forming the sheet, non-wet heat adhesive fibers that do not exhibit adhesiveness by wet heat treatment may be used in combination with wet heat adhesive fibers as long as the effects of the present invention are not impaired. Specific examples of the resin forming the non-wet heat adhesive fiber include, for example, polyester resins such as polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyamide 6, polyamide 66, polyamide 11, polyamide 12, Aliphatic polyamide resins such as polyamide 610 and polyamide 612, semi-aromatic polyamide resins such as polyamide 6T and polyamide 9T, and aromatic polyamide resins such as polyphenylene isophthalamide, polyhexamethylene terephthalamide and poly p-phenylene terephthalamide Polyamide resins such as polyethylene, polypropylene, polybutene, etc .; Acrylonitrile units such as acrylonitrile-vinyl chloride copolymer Acrylic resins such as nitrile resins; polyvinyl resins such as polyvinyl acetal resins; polyvinyl chloride resins such as polyvinyl chloride, vinyl chloride-vinyl acetate copolymers, vinyl chloride-acrylonitrile copolymers; vinylidene chloride Polyvinylidene chloride resins such as vinyl chloride copolymers and vinylidene chloride-vinyl acetate copolymers; polyparaphenylene benzobisoxazole; polyphenylene sulfide; and cellulose resins such as rayon and acetate. These may be used alone or in combination of two or more.

  When wet heat adhesive fibers and non-humid heat bond fibers are used in combination, the mass ratio is not particularly limited, but the hardness and rigidity of the obtained sheet, surface smoothness, good polishing speed and step-removability, abrasion resistance The content ratio of non-wet heat adhesive fiber to the total amount of wet heat adhesive fiber and non-wet heat adhesive fiber is 40% by mass or less, more preferably 30% by mass or less, and particularly 20% by mass or less. Is preferably 10% by mass or less.

  The average fineness of the fiber forming the fiber web is not particularly limited, but is 0.1 to 10 dtex, more preferably 0.5 to 7 dtex, and particularly 1 to 5 dtex, and the productivity of the sheet and the polishing rate of the polishing pad This is preferable from the viewpoint of excellent polishing uniformity.

  Moreover, although the average fiber length of the fiber which forms a fiber web is not specifically limited, Specifically, it is preferable that it is about 10-100 mm, for example, 20-80 mm, especially about 25-75 mm. If it is this range, the fiber opening state by the card machine will become more favorable, and the fiber web in which each fiber was disperse | distributed uniformly can be obtained. For this reason, the fiber entanglement can be formed uniformly, and since the distance between the fibers is close and many parts that are likely to become adhesion points between the fibers by the wet heat treatment are formed uniformly, the adhesiveness of the wet heat adhesive fibers is improved. The mechanical strength of the sheet is sufficiently maintained.

  The shape of the cross section of the fiber forming the fiber web is not particularly limited. Specific examples include, for example, a round cross section, which is a general solid cross section, a flat shape, an oval shape, a polygonal shape, a 3-14 leaf shape, a T shape, an H shape, a V shape, a dog bone ( I-shaped), atypical cross sections such as hollow cross sections, and the like.

  The porosity of the sheet to be the polishing layer of the present embodiment is 5 to 35%, 7 to 32%, further 10 to 30%, particularly 12 to 27%, especially 15 to 25%. preferable. When the porosity is less than 5%, the number of voids exposed on the polishing surface decreases, so that the retention of the polishing slurry decreases and the polishing rate decreases. If the porosity exceeds 35%, too many holes are exposed on the polished surface, and communication holes are formed. In this case, the polishing slurry is absorbed by the communication holes from the holes and is difficult to be supplied to the surface to be polished, thereby reducing the polishing rate. Further, the scraps and the like clog the voids and accumulate, thereby making it easy to generate scratches on the surface to be polished. In addition, the porosity shows the ratio of the area of the space | gap except the area which the cross section which a fiber and resin form in the cross section of a sheet | seat. Therefore, the porosity is almost the same as the value obtained by dividing the apparent density by the true specific gravity of the fiber or resin.

  The size of the voids in the sheet is 10 to 150 μm, more preferably 15 to 120 μm, particularly 20 to 100 μm, and more particularly 25 to 80 μm, when the cross section is observed. preferable.

Further, the apparent density of the sheet, 0.8~1.2g / cm ^3, more 0.82~1.18g / cm ^3, in particular, 0.84~1.16g / cm ^3, is that the 0 It is preferably about .86 to 1.14 g / cm ³ . When the apparent density is too low, the polishing slurry tends to be absorbed in the gaps in the polishing surface and is difficult to be supplied to the surface to be polished, so that the polishing rate tends to decrease. In addition, the scraps and the like are clogged and accumulated in the voids exposed on the polished surface, and thus there is a tendency that scratches are likely to occur on the polished surface. On the other hand, when the apparent density is too high, the voids exposed on the polishing surface are reduced, whereby the retention of the polishing slurry tends to decrease and the polishing rate tends to decrease.

  Further, the D hardness of the sheet in the dry state is preferably 60 to 80, more preferably 62 to 79, particularly 64 to 78, and particularly preferably 66 to 77. When the D hardness is too low, the polishing speed, flatness, and level difference elimination tend to decrease due to the hardness of the polished surface being too low during water absorption. Further, when the D hardness is too high, the hardness of the polished surface at the time of water absorption tends to be too high, so that scratches tend to occur on the polished surface. The D hardness of the sheet strongly correlates with the apparent density. Generally, the higher the apparent density, the higher the D hardness, and the lower the apparent density, the lower the D hardness. Further, when the glass transition temperature of the resin is higher than room temperature, such as EVOH or PET, the influence of the difference in the resin is relatively small. Therefore, the desired D hardness can be adjusted by appropriately adjusting the apparent density according to the resin constituting the fiber.

  Further, in the image obtained by photographing the cross section with a scanning electron microscope (SEM), the ratio of the number of contours of the cross section of the fiber bonded to other fibers is 90% or more with respect to the total number of contours of the cross section of the fiber. Further, it is preferably 92% or more, particularly 94% or more, and particularly preferably 96% or more. When the number of independent fibers that are not bonded to other fibers is too large, the communication holes are easily formed in the sheet, and the polishing slurry is absorbed from the gaps in the polishing surface and supplied to the surface to be polished. Is insufficient and the polishing rate tends to decrease. Further, polishing scraps and the like are easily clogged in the voids exposed on the polishing surface.

  Furthermore, the ratio of the number of cross-sectional contours of fibers bonded to other fibers to the total number of cross-sectional contours of the fibers is substantially uniform from the front surface to the back surface along the thickness direction. It is preferable that When there is variation in the thickness direction, the characteristics of the sheet are not uniform in the thickness direction, so that the polishing characteristics tend to change as the polishing layer wears.

Moreover, it is preferable that the sheet | seat used as a grinding | polishing layer has very low air permeability, or hardly exists. Specifically, the air permeability according to the Frazier method is 1 cm ³ / cm ² / sec or less, further 0.8 cm ³ / cm ² / sec or less, particularly 0.6 cm ³ / cm ² / sec or less. It is preferably 0.4 cm ³ / cm ² / second or less. When the air permeability is too high, the polishing slurry is easily absorbed in the gaps in the polishing surface and is difficult to be supplied to the surface to be polished, so that the polishing rate is likely to decrease. In addition, the scraps and the like are clogged and accumulated in the voids exposed on the polished surface, and thus there is a tendency that scratches are likely to occur on the polished surface.

  In addition, the above-described fiber component includes, for example, a stabilizer such as a heat stabilizer, an ultraviolet absorber, a light stabilizer, and an antioxidant, fine particles, a colorant, an antistatic agent, a plasticizer, as long as the effects of the present invention are not impaired. You may contain additives, such as an agent, a lubricant, and a crystallization rate retarder, as needed. Moreover, unless the effect of this invention is inhibited, a thermoplastic resin, a thermosetting resin, inorganic particles, etc. may be included outside the fiber component forming the sheet.

  The surface roughness of the polishing surface of the polishing layer is adjusted (sharpened) using a dresser such as a diamond dresser, so that the arithmetic average roughness (Ra) is 1 to 9 μm and the maximum height ( Rz) is preferably adjusted to 10 to 90 μm. When Ra is less than 1 μm, or when Rz is less than 10 μm, the slurry retainability of the polishing surface tends to be low, and the polishing rate tends to decrease. On the other hand, when Ra is more than 9 μm or Rz is more than 90 μm, the flatness and the level difference elimination tend to be lowered. In particular, when polishing a constituent material of a semiconductor device, very high flatness and level difference elimination are required, so that Ra is 1 to 6 μm, Rz is 10 to 60 μm, and Ra is 1.2 to 5. 5 μm, Rz is 12 to 55 μm, particularly Ra is 1.5 to 5 μm, and Rz is 15 to 50 μm. In particular, Ra is 1.8 to 4.5 μm and Rz is preferably 18 to 45 μm. .

  Next, an example of the manufacturing method of the polishing pad of this embodiment is demonstrated.

  First, a web of fibers containing wet heat adhesive fibers as described above is produced. Specific examples of the web production method include, for example, a method of forming a web by directly laminating melt-spun fibers by using a direct method such as a spunbond method or a meltblowing method, or a method in which staple fibers are carded. There are no particular restrictions on the web method such as the card method or the dry method such as the air array method. Among these, the card method using staple fibers is particularly preferably used. Examples of the web obtained using staple fibers include a random web, a semi-random web, a parallel web, and a cross-wrap web.

  Next, the obtained fiber web is wet-heat treated to bond the fibers together to form a non-woven fiber substrate. Specifically, for example, while the obtained fiber web is conveyed by a mesh conveyor, the fibers are bonded to each other by bringing them into contact with high-temperature steam (high-pressure steam) ejected from a nozzle of a steam spraying device. A material can be obtained.

  Since the high-temperature steam jetted from the steam jetting apparatus is an air stream, unlike the hydroentanglement process or the needle punch process, the high-temperature steam enters the fiber web without moving the fibers in the fiber web largely. Then, when the steam flow enters the fiber web, the wet heat adhesive resin in the wet heat adhesive fiber forming the fiber web becomes adhesive, and the fibers are bonded to each other. According to such a method, the wet heat treatment is performed in a short time under a high-speed stream of steam, so that sufficient heat is applied to the fiber surface, while excessive heat is applied to the inside of the fiber. The wet heat treatment is finished before it is transmitted. Therefore, the fiber form is not completely lost by the pressure or heat of the steam. As a result, a non-woven fibrous base material uniformly bonded in the thickness direction can be obtained without causing large deformation or the like due to melting or softening of the fiber web.

  In addition, since the nonwoven fiber base material obtained by wet-heat-treating the fiber web as described above does not depend on mechanical entanglement such as a needle punch, the fiber array state is parallel to the fiber web surface. Can be maintained. That is, fewer fibers are oriented in the thickness direction perpendicular to the fiber web surface. When there are many fibers oriented along the thickness direction, the fiber arrangement is disturbed in the periphery, so the size and distribution of voids in the resulting polishing layer are likely to vary, and the surface roughness of the polishing surface is There is a tendency that the step-resolving property tends to be deteriorated with increasing size. Specifically, for example, in an image obtained by observing an arbitrary cross section in the thickness direction of the polishing layer with an electron microscope, the ratio of the number of fibers continuously extending to a length of 30% or more with respect to the thickness is 10% or less. It is preferable that

  The pressure of the high-temperature steam is not particularly limited as long as the fibers can be bonded to each other by wet-heat treating the fiber web. Specifically, for example, 0.05 to 4 MPa, further 0.1 to 3 MPa, particularly 0.2 to 2 MPa, and more preferably about 0.3 to 1.5 MPa are preferable. When the pressure of the steam or the speed of the airflow is too high, the fibers in the fiber web tend to be disturbed in the formation or have a portion where the fiber shape is not maintained. In addition, when the steam pressure or the airflow speed is too low, a sufficient amount of heat is not applied to bond the fibers forming the fiber web, or the steam does not sufficiently pass through the fiber web. Adhesion spots may occur in the vertical direction. Furthermore, it may be difficult to control the uniform ejection of vapor from the nozzle. The temperature of the high-temperature steam is preferably 70 to 150 ° C, more preferably 80 to 140 ° C, particularly 90 to 130 ° C, and more preferably about 100 to 120 ° C.

The apparent density of the nonwoven fiber substrate obtained by such wet heat treatment is 0.1 to 0.7 g / cm ³ , further 0.12 to 0.6 g / cm ³ , and particularly 0.15 to 0. 0.5 g / cm ³ , and preferably about 0.2 to 0.4 g / cm ³ . When the apparent density of the non-woven fiber substrate is too low, the surface roughness of the polished surface tends to increase and the level difference elimination tends to decrease. On the other hand, when the apparent density of the nonwoven fibrous base material is too high, it becomes difficult for vapor to pass through the fiber web, so that adhesion spots tend to occur in the thickness direction.

  The configuration of the apparatus for performing the wet heat treatment as described above is not particularly limited as long as the configuration is such that the fiber web is brought into contact with steam or hot water while the fiber web is conveyed using a conveyor or a roller. A typical configuration will be described below.

  A pair of conveyor devices including an upper mesh conveyor and a lower mesh conveyor capable of arbitrarily adjusting the distance between each other are prepared. And a vapor | steam injection apparatus is arrange | positioned so that a vapor | steam may be injected to the back surface of the mesh conveyor of the one side of a conveyor apparatus toward the mesh conveyor of the other side substantially perpendicularly. In the wet heat treatment apparatus having such an apparatus configuration, the distance between the upper mesh conveyor and the lower mesh conveyor is adjusted so that the nonwoven fabric base material has the desired thickness, A fiber web is inserted between the mesh conveyor on the side, and the fiber web is conveyed in the inserted state. And when the fiber web conveyed contacts the vapor | steam injected from a vapor | steam injection apparatus, the fibers which form a fiber web are adhere | attached and a nonwoven fiber base material is formed.

  In addition, you may arrange | position the suction box for attracting | sucking vapor | steam discharge | emission as needed on the back surface of the mesh conveyor of the other side facing the mesh conveyor by which the steam injection apparatus was distribute | arranged on the back surface. By arranging the suction box, steam can be effectively passed through the fibrous web. Moreover, even if there is only one set of the steam injection device and the suction box, a configuration may be adopted in which a plurality of sets are provided, for example, one set is arranged on the upstream side and the downstream side of the conveyor device. In addition, when arrange | positioning 1 set at a time at the upstream and downstream of a conveyor apparatus, it is preferable to arrange | position an upstream and downstream steam injection apparatus, and a suction box so that it may mutually oppose. By arrange | positioning in this way, in order to pass a vapor | steam from both surfaces of the surface of a fiber web, and a back surface, the adhesion spot of the thickness direction can be suppressed. In addition, when only one set of the steam injection device and the suction box is disposed, the fiber web once wet-heat treated with the steam spray device is reversely turned over and then wet-heat treated with the steam spray device again to adhere in the thickness direction. Spots can be suppressed. In addition, when a suction box is not installed, a stainless steel plate or the like is installed instead so that the steam does not escape. This suppresses adhesion spots.

  Moreover, in order to adjust the apparent density of the nonwoven fiber base material, use a fiber web with an adjusted basis weight, adjust the gap between the upper mesh conveyor and the lower mesh conveyor, or the roller gap, etc. It is preferable to inject the steam in a state compressed to a predetermined thickness. In particular, in order to obtain a high-density molded body, it is preferable to perform a wet heat treatment in a state where the fiber web is sufficiently compressed. In the case of a mesh conveyor, it is difficult to rapidly compress the fiber web, so the tension of the mesh conveyor is set high, and the upper mesh conveyor and lower mesh are gradually increased from the upstream side toward the downstream side. It is preferable to narrow the clearance with the conveyor. The material of the conveyor belt or roller surface is not particularly limited as long as it can withstand steam treatment, but heat-resistant resin such as heat-treated polyester, polycarbonate, polyphenylene sulfide, polyarylate or wholly aromatic polyester. It is preferable that

  Next, in order to adjust to a desired porosity, the non-woven fiber base material obtained by wet heat treatment is densified using a hot press, a heating roll, or the like. In this case, by performing the heating temperature at a temperature slightly lower than the melting point of the resin on the fiber surface, a skin layer is formed on the surface and the occurrence of fiber adhesion spots and sheet density spots in the thickness direction is suppressed. it can. For example, as the conditions of the hot press, the temperature is 5 to 30 ° C., 7 to 25 ° C., particularly 10 to 20 ° C. lower than the melting point of the wet heat adhesive resin contained in the wet heat adhesive fiber, and 1 to 100 MPa. In addition, there may be mentioned conditions such that the pressure is 3 to 50 MPa, particularly 5 to 30 MPa. At this time, prior to the above-described hot pressing, a preliminary hot pressing is preferably performed at a temperature lower by 30 to 100 ° C., more preferably 35 to 90 ° C., particularly 40 to 80 ° C. than the melting point of the wet heat adhesive resin. Also good. By increasing the density in two stages as described above, it is possible to increase the density to some extent while preventing the fibers from being bonded in the first stage, and to increase the density while bonding the fibers in the second stage. As a result, the effect of preventing the formation of the skin layer is further enhanced, and the density can be increased more uniformly in the thickness direction. Note that steam treatment can be used in combination with such a densification treatment, but in that case as well, it is preferable to set the temperature so that the wet heat adhesive resin does not melt completely.

  As described above, a sheet used as a polishing layer of a polishing pad is manufactured. The obtained sheet is used as a polishing layer after being processed into a shape suitable for a polishing pad by cutting, cutting, slicing, punching or the like, if necessary. The sheet thus obtained is uniform because the fibers are bonded evenly as a whole, compared to a sheet that is mechanically entangled with a fiber web or heat bonded by hot press. In addition, since it is finished with a low porosity, that is, a high density by the bonded fibers, high hardness, durability, and surface smoothness can be obtained.

  The polishing pad using the sheet thus obtained as a polishing layer provides cushioning properties to the surface opposite to the polishing surface of the polishing layer, even as a single-layer polishing pad consisting only of the polishing layer. Further, it may be used as a polishing pad having a multilayer structure in which a known cushion layer made of an elastomer sheet having a foam structure or a non-foam structure, a nonwoven fabric impregnated with an elastomer, or the like is laminated. A cushion layer is laminated | stacked on a sheet | seat using an adhesive or an adhesive agent. The Asker C hardness of the cushion layer is preferably 30 to 80 from the viewpoint of excellent flatness and polishing uniformity.

  The thickness of the polishing layer is not particularly limited, but is 0.6 to 4.0 mm, further 0.8 to 3.5 mm, particularly 1.0 to 3.0 mm, and more particularly 1.2 to 2.5 mm. It is preferable from the viewpoint of polishing performance and pad life. If the polishing layer is too thin, the life of the polishing pad will be shortened, and the polishing performance will become unstable as the polishing layer wears because it becomes susceptible to the surface plate of the polishing apparatus and the laminated cushion layer. Tend. Further, when the polishing layer is too thick, the rigidity becomes high, and even when the cushion layer is laminated, the polishing uniformity may be lowered.

  Moreover, it is preferable to form a groove or a hole for holding the polishing slurry on the surface of the polishing layer by grinding, laser processing, embossing or the like, if necessary. When the cushion layer is laminated, the depth of such grooves and holes is 30 to 90%, more preferably 35 to 85%, and particularly 40 to 80% with respect to the thickness of the polishing layer. Is particularly preferable from the viewpoint of excellent balance between polishing uniformity and planarization performance.

  The polishing pad provided with the polishing layer thus obtained includes, for example, a semiconductor substrate such as a silicon wafer or a glass substrate, an insulating film or a metal film on the substrate, such as a semiconductor device or a liquid crystal display device. It is preferably used for polishing a substrate on which is formed. As a polishing method, a chemical mechanical polishing apparatus (CMP apparatus) and a chemical mechanical polishing method (CMP) using a polishing slurry are preferably used. As the CMP, for example, a polishing pad having a polishing layer is attached to a polishing surface plate of a CMP apparatus, a polishing slurry is supplied to the surface of the polishing layer, and a pressure is applied while pressing an object to be polished against the polishing pad. And a method for polishing the surface of the object to be polished by rotating the object to be polished together. In addition, before polishing or during polishing, it is preferable to condition and prepare the polished surface using a dresser such as a diamond dresser, if necessary.

  Next, the polishing pad and the manufacturing method thereof according to the present invention will be specifically described with reference to examples. The scope of the present invention is not limited by these examples. In the examples, “parts” and “%” are based on mass unless otherwise specified.

[Production Example 1]
As wet heat adhesive fiber, the core component is polyethylene terephthalate (PET), the sheath component is ethylene-vinyl alcohol copolymer (EVOH, ethylene copolymerization rate 44 mol%, saponification degree 98.4 mol%, melting point 165 ° C.) A certain core-sheath type composite staple fiber (3.0 dtex, 51 mm length, core-sheath mass ratio = 50/50, number of crimps 21/25 mm) was prepared. Using 100% by mass of the core-sheath type composite staple fiber, a card web having a basis weight of about 2500 g / m ² was produced by a card method. This card web was transferred to a wet heat treatment apparatus provided with a conveyor device and a water vapor spraying device for spraying water vapor to the path.

  The conveyor device includes an upper mesh conveyor and a lower mesh conveyor made of polycarbonate endless nets of 50 mesh and width 500 mm, each of which travels in the same direction at the same speed, and the spacing between them is arbitrary. A pair of adjustable mesh conveyors. Further, on the upstream side of the conveyor device, a water vapor spraying device for spraying high-temperature water vapor through a net toward the card web to be conveyed is arranged on the back side of the lower mesh conveyor, while the back side of the upper mesh conveyor Is equipped with a suction device. On the contrary, on the downstream side of the conveyor, a similar suction device is disposed on the back side of the lower mesh conveyor, and a similar steam spraying device is disposed on the back side in the upper mesh conveyor. Each water vapor spraying device has a plurality of nozzles with a hole diameter of 0.3 mm arranged in a line at a pitch of 1 mm along the width direction of the conveyor. Further, the nozzle is disposed so as to substantially contact the back side of the mesh conveyor net. According to such a configuration, high-temperature steam is sprayed on both the front and back sides of the card web.

  Steam card | curd was given to the card | curd conveyed by making 0.6 MPa high temperature water vapor | steam ejected from each water vapor | steam injection apparatus substantially perpendicularly. In addition, the conveyance speed of the conveyor was 3 m / min, and the space | interval of an upper mesh conveyor and a lower mesh conveyor was adjusted so that the nonwoven fiber base material of thickness about 6mm could be obtained. In this way, a non-woven fiber base material having a thickness of about 6 mm formed by wet-heat adhesive fibers being wet-heat bonded was obtained.

  And after performing the hot press for 5 minutes on the conditions of 120 degreeC and 15 MPa using the spacer of 2.5 mm in thickness, the obtained nonwoven fiber base material, using the spacer of thickness 2.4 mm, The sheet was densified by further performing hot pressing for 5 minutes at 150 ° C. and 15 MPa. And the sheet | seat 1 was obtained by cutting from both surfaces uniformly so that the thickness of a sheet | seat may be set to 2.0 mm.

[Production Example 2]
A sheet 2 was produced in the same manner as in Production Example 1 except that the conditions of hot pressing and cutting of the nonwoven fiber substrate were changed as follows. Specifically, the non-woven fiber substrate was hot-pressed for 5 minutes under conditions of 130 ° C. and 15 MPa using a spacer having a thickness of 2.3 mm, and then 152 ° C. using a spacer having a thickness of 2.2 mm. The sheet was densified by further performing hot pressing for 5 minutes under the condition of 15 MPa. Next, the sheet 2 was obtained by uniformly cutting from both sides so that the thickness of the sheet was 1.8 mm. A scanning microscope (SEM) photograph of the cross section of the sheet 2 is shown in FIG.

[Production Example 3]
A sheet 3 was produced in the same manner as in Production Example 1 except that the conditions for hot pressing and cutting of the nonwoven fiber substrate were changed as follows. Specifically, the non-woven fiber substrate was hot-pressed for 5 minutes at 90 ° C. and 15 MPa using a spacer having a thickness of 2.7 mm, and then 152 ° C. using a spacer having a thickness of 2.6 mm. The sheet was densified by further performing hot pressing for 5 minutes under the condition of 15 MPa. And the sheet | seat 3 was obtained by cutting uniformly from both surfaces so that the thickness of a sheet | seat might be 2.2 mm. A scanning microscope (SEM) photograph of the cross section of the sheet 3 is shown in FIG.

[Production Example 4]
A sheet 4 was produced in the same manner as in Production Example 1 except that the conditions of hot pressing and cutting of the nonwoven fiber substrate were changed as follows. Specifically, the non-woven fiber base material was subjected to hot pressing for 5 minutes only at one stage under conditions of 153 ° C. and 15 MPa using a spacer having a thickness of 2.8 mm to obtain a densified sheet. . And the sheet | seat 4 was obtained by cutting uniformly from both surfaces so that the thickness of a sheet | seat might be 2.3 mm.

[Production Example 5]
A sheet 5 having a thickness of 2.0 mm was prepared in the same manner as in Production Example 1 except that a core-sheath type composite staple fiber in which only the fineness was changed to 1.7 dtex was used instead of the 3.0 dtex core-sheath type composite staple fiber. Manufactured. A photograph of a scanning microscope (SEM) of the cross section of the sheet 5 is shown in FIG.

[Production Example 6]
Core-sheath type composite staple fiber (3.0 dtex, 51 mm length, core-sheath mass) whose core component is PET and sheath component is EVOH (ethylene copolymerization rate 44 mol%, saponification degree 98.4 mol%, melting point 165 ° C.) Ratio = 50/50, number of crimps 21/25 mm), core component is PET, sheath component is EVOH (ethylene copolymerization rate 48 mol%, saponification degree 98.9 mol%, melting point 160 ° C.) A non-woven fiber base material is obtained in the same manner as in Production Example 1 except that a core-sheath type composite staple fiber (5.0 dtex, 51 mm length, core-sheath mass ratio = 30/70, number of crimps 22/25 mm) is formed. It was. Further, a sheet 6 was produced in the same manner as in Production Example 1 except that the conditions for hot pressing and cutting of the nonwoven fiber base material were changed as follows. Specifically, the nonwoven fiber base material was hot-pressed for 5 minutes at 90 ° C. and 15 MPa using a spacer having a thickness of 2.7 mm, and then 146 ° C. using a spacer having a thickness of 2.6 mm. The sheet was densified by further performing hot pressing for 5 minutes under the condition of 15 MPa. And the sheet | seat 6 was obtained by cutting uniformly from both surfaces so that the thickness of a sheet | seat might be 2.2 mm.

[Production Example 7]
Instead of the core-sheath type composite staple fiber in which the core component is PET and the sheath component is EVOH, the core component is polyamide 6 (PA6), the sheath component is EVOH (ethylene copolymerization rate: 44 mol%, saponification degree: 98.4 mol%) , Melting point 165 ° C.) core-sheath type composite staple fiber (5.0 dtex, 51 mm length, core-sheath mass ratio = 70/30, number of crimps 20/25 mm) A nonwoven fiber substrate was obtained. Further, a sheet 7 was produced in the same manner as in Production Example 1 except that the conditions for hot pressing and cutting of the nonwoven fiber base material were changed to the same conditions as in Production Example 4. That is, the non-woven fiber base material was hot-pressed for 5 minutes in only one stage under conditions of 153 ° C. and 15 MPa using a spacer having a thickness of 2.8 mm, thereby obtaining a densified sheet. And the sheet | seat 7 was obtained by cutting uniformly from both surfaces so that the thickness of a sheet | seat might be 2.3 mm.

[Comparative Production Example 1]
A sheet 8 was produced in the same manner as in Production Example 1 except that the hot pressing and cutting conditions of the nonwoven fiber substrate were changed as follows. Specifically, the non-woven fiber base material was hot-pressed for 5 minutes under conditions of 120 ° C. and 15 MPa using a spacer having a thickness of 2.1 mm, and then 158 ° C. using a spacer having a thickness of 2.0 mm. The sheet was densified by further performing hot pressing for 5 minutes under the condition of 15 MPa. And the sheet | seat 8 was obtained by cutting uniformly from both surfaces so that the thickness of a sheet | seat might be 1.7 mm.

[Comparative Production Example 2]
A sheet 9 was produced in the same manner as in Production Example 1 except that the conditions for hot pressing and cutting of the nonwoven fiber substrate were changed as follows. Specifically, the non-woven fiber base material was hot-pressed for 5 minutes at 120 ° C. and 15 MPa using a spacer having a thickness of 3.4 mm, and then 155 ° C. using a spacer having a thickness of 3.3 mm. Further, the sheet was densified by further performing hot pressing for 5 minutes under the condition of 15 MPa. And the sheet | seat 9 was obtained by cutting uniformly from both surfaces so that the thickness of a sheet | seat might be set to 2.5 mm.

[Comparative Production Example 3]
A sheet 10 was produced in the same manner as in Production Example 1 except that the conditions for hot pressing and cutting of the nonwoven fiber substrate were changed as follows. Specifically, the non-woven fiber substrate was hot-pressed for 5 minutes at 120 ° C. and 15 MPa using a spacer having a thickness of 4.1 mm, and then 155 ° C. using a spacer having a thickness of 4.0 mm. Further, the sheet was densified by further performing hot pressing for 5 minutes under the condition of 15 MPa. And the sheet | seat 10 was obtained by cutting uniformly from both surfaces so that the thickness of a sheet | seat might be set to 2.5 mm. A scanning microscope (SEM) photograph of the cross section of the sheet 10 is shown in FIG.

[Comparative Production Example 4]
Instead of the core-sheath type composite staple fiber in which the core component is PET and the sheath component is EVOH, which is a wet heat adhesive fiber, the core component is PET and the sheath component is a heat-fusible fiber of non-wet heat adhesive fiber. A core-sheath type composite staple fiber (3.0 dtex, 51 mm length, core-sheath mass ratio = 50/50, number of crimps 21/25 mm), which is modified PET (isophthalic acid modification amount 32 mol%, melting point 140 ° C.), is formed. A non-woven fiber substrate was obtained in the same manner as in Production Example 1 except that. Further, a sheet 11 was produced in the same manner as in Production Example 1 except that the conditions for hot pressing and cutting of the nonwoven fiber base material were changed as follows. Specifically, the non-woven fiber substrate was hot pressed for 5 minutes at 130 ° C. and 15 MPa using a 2.3 mm thick spacer, and then 140 ° C. using a 2.2 mm thick spacer. The sheet was densified by further performing hot pressing for 5 minutes under the condition of 15 MPa. Subsequently, the sheet | seat 11 was obtained by cutting uniformly from both surfaces so that the thickness of a sheet | seat might be set to 1.8 mm.

[Comparative Production Example 5]
As a non-wet heat-adhesive heat-fusible fiber, a core-sheath composite staple fiber (3.0 dtex, 51 mm length) in which the core component is PET and the sheath component is modified PET (isophthalic acid modification amount 32 mol%, melting point 140 ° C.) Core-sheath mass ratio = 50/50, number of crimps 21/25 mm). Using 100% by mass of the core-sheath type composite staple fiber, a card web having a basis weight of about 2500 g / m ² was produced by a card method. The card web was needle punched to obtain a non-woven fiber substrate having a basis weight of about 2000 g / m ² and a thickness of about 7 mm. The nonwoven fiber base material thus obtained was hot-pressed for 5 minutes at 136 ° C. and 15 MPa using a spacer having a thickness of 2.2 mm to obtain a densified sheet. And the sheet | seat 12 was obtained by cutting uniformly from both surfaces so that the thickness of a sheet | seat might be 1.8 mm.

[Comparative Production Example 6]
EVOH (ethylene copolymerization rate: 44 mol%, saponification degree: 98.4 mol%, melting point: 165 ° C) was charged into a single screw extruder and extruded from a T-die to form a 2.5 mm thick sheet. did. And the sheet | seat 13 was obtained by cutting uniformly from both surfaces so that the thickness of a sheet | seat might be 1.8 mm. The sheet 13 was a non-foamed sheet having no pores.

[Evaluation of Sheets 1 to 13]
Various characteristics of the sheets 1 to 13 were evaluated as follows.
<Porosity>
A part of the sheet was cut to prepare a scanning electron microscope (SEM) sample. The observation sample was divided into three equal parts in the thickness direction, and samples of the front side portion, the inner side portion, and the back side portion obtained by dividing the sheet into three equal portions were prepared. And using SEM, the picked-up image which expanded each sample 200 times was obtained. Trace paper was superimposed on this photographed image, and the photographed area and the void were traced using transmitted light. The trace diagram was captured from a CCD camera into a computer using an image analyzer. Then, the image was binarized using image processing software “ImageJ”, and the ratio of the area of the void to the total area of the observation region was calculated. At this time, measurement was performed by adding photographs so that the total of the observation surfaces was 10 mm ² or more. And the average value of three site | parts was made into the porosity.
<Hole size>
In the same manner as the measurement of “void ratio”, after obtaining an SEM photograph image in which the cross section of the sheet at three sites was magnified 200 times, the void portion was traced. This trace diagram was taken into a computer, and after binarizing the image at each site, the length in the major axis direction was measured for each of arbitrary 30 holes, and the average value was obtained. And the average value of three site | parts was made into the magnitude | size of a void | hole.
<Thickness, basis weight, apparent density>
The thickness (mm) and the basis weight (g / cm ² ) were measured according to JIS L1913, and the apparent density (g / cm ³ ) was calculated from these values.
<Durometer hardness>
The hardness was measured by a durometer hardness test (type D) according to JIS K6253.
<Fiber adhesion rate>
In the same manner as the measurement of “void ratio”, an SEM photographed image was obtained in which the cross section of the sheet at three sites was magnified 200 times. Then, in each part, count the total number of fiber cross-sectional contours observed in the photographed image and the number of fiber cross-sectional contours in which at least one other fiber cross-section is bonded to the periphery, and the total number of contours The ratio of the number of contours of the fiber cross-section bonded to the other fiber cross-section was calculated based on the following formula.
Fiber adhesion rate (%) = (number of fiber cross-section contours adhered to other fiber cross-sections) / (total number of fiber cross-section contours) × 100
In addition, the counting is performed by counting all the contours of the fiber cross section observed in each photographed image, and when the number of contours is less than 100, another photographed image of the same part is further added so as to be 100 or more. It was.
When the fibers are simply in contact with each other without being bonded, the internal stress of the fibers is released and separated when the sheet is cut. Therefore, all the fibers in contact with each other in the photographed image were regarded as adhered.
<Air permeability>
According to JISL1096, it measured by the fragile type method.
<Crimp number>
Evaluation was performed according to JISL1015 (8.12.1).

  The results are summarized in Table 1.

[Examples 1 to 5 and Comparative Examples 1 to 4: Copper film polishing performance evaluation]
The polishing performance of the sheets 1, 3 to 5, 7, 8, 10 to 12 obtained in the production examples was evaluated as follows.
Each sheet was cut into a circular shape having a diameter of 38 cm. Then, grooves having a width of 0.5 mm and a depth of 0.8 mm were formed concentrically at intervals of 2.5 mm on the surface of the cut circular sheet, and a circular polishing layer having a diameter of 38 cm was produced. And the polishing pad was obtained by bonding together the foamed polyurethane sheet of thickness 1.0mm and Asker C hardness 50 as a cushion layer on the back surface of the obtained polishing layer. And the copper film polishing performance of each obtained polishing pad was evaluated as follows.

  A polishing pad was attached to the polishing surface plate of the polishing apparatus. Then, the polishing pad surface was conditioned for 60 minutes using a diamond dresser while flowing pure water at a rate of 150 mL / min under the conditions of a dresser rotation speed of 140 rpm, a polishing pad rotation speed of 100 rpm, and a dresser load of 5 N. In addition, “BC-15” manufactured by MTT Co., Ltd. was used as a polishing apparatus, and a diamond dresser manufactured by Allied Material Co., Ltd. having a diamond count of # 100 and a base metal diameter of 190 mm was used.

  Then, with respect to 100 parts by mass of polishing slurry containing silicon oxide abrasive grains (“PL7105” manufactured by Fujimi) under the conditions of a polishing pad rotational speed of 100 rpm, a wafer rotational speed of 99 rpm, and a polishing pressure of 24 kPa, While supplying 10 parts by mass of 30% hydrogen peroxide water at a rate of 100 mL / min, a silicon wafer with a diameter of 100 mm having a copper film with an initial film thickness of 1500 nm on the surface is polished for 60 seconds without conditioning. did.

  Then, after conditioning for 30 seconds, the wafer was replaced with a new wafer, and polishing and conditioning were repeated again, and a total of 20 wafers were polished in the same manner.

  And about the silicon wafer which grind | polished the 20th sheet | seat and which has a copper film on the surface, the grinding | polishing speed | rate, grinding | polishing nonuniformity, the presence or absence of a scratch, the surface roughness of a grinding | polishing surface, and the change of the pad groove depth were measured. The change in the pad groove depth is an evaluation of the wear resistance of the pad, that is, the usable time. The polishing rate, polishing non-uniformity, scratch, surface roughness of the polishing surface, and pad groove depth were measured as follows.

<Measurement of polishing rate and non-uniformity of polishing>
The film thickness of the copper film before and after polishing was measured at 49 points on the wafer surface, and the polishing rate at each point was determined. In addition, 49 points are 8 points at 45 ° intervals on a concentric circle 15 mm from the center, 16 points at 22.5 ° intervals on a concentric circle 30 mm from the center, and 15 ° on a concentric circle 45 mm from the center. It consists of 24 points at intervals. The average value of the 49 polishing rates was taken as the polishing rate. Further, the polishing non-uniformity was evaluated by the non-uniformity obtained by the following formula (1). It shows that it is grind | polished uniformly within a to-be-polished surface, and polishing uniformity is excellent, so that the value of nonuniformity is small.
Nonuniformity (%) = (σ / R) × 100 (1)
(However, σ: Standard deviation of polishing rate at 49 points, R: Average value of polishing rate at 49 points.)
The film thickness of the copper film was measured using a film thickness measuring device “RESISTAGE RT-80” manufactured by Napson Corporation.
<Scratch measurement>
The polished surface after polishing was randomly observed at a magnification of 1000 using a Keyence laser microscope “VK-X200” to confirm the presence or absence of scratches.
<Surface roughness of polishing surface of polishing pad>
A surface roughness measuring instrument “Surf Test SJ-210” manufactured by Mitutoyo Corporation was used to measure the surface roughness immediately after polishing in accordance with JIS2001.
<Decrease in pad groove depth>
As an index of usable time, the groove depth at a position 100 mm from the center of the pad was measured with a caliper, and the amount of decrease was determined.

  The results are summarized in Table 2.

  From the results in Table 2, none of the polishing pads obtained in Examples 1 to 5 using the sheets obtained in Production Examples 1, 3, 4, 5, and 7 were scratched, and the polishing rate was also high. Further, the polishing non-uniformity was low. On the other hand, the polishing pad obtained in Comparative Example 1 using the sheet 8 obtained in Comparative Production Example 1 having a low porosity had a low polishing rate, generated scratches, and high polishing nonuniformity. In addition, the polishing pad obtained in Comparative Example 2 using the sheet 10 obtained in Comparative Production Example 3 with a high porosity has a communication hole, so that the slurry is not sufficiently supplied to the surface to be polished. The polishing rate was low. Further, the polishing pad obtained in Comparative Example 3 or Comparative Example 4 using the sheet 11 obtained in Comparative Production Example 4 or the sheet 12 obtained in Comparative Production Example 5 prepared without using wet heat adhesive fibers. Was extremely high in polishing non-uniformity, and scratches were also generated.

[Examples 6 to 10 and Comparative Examples 5 to 8: Evaluation of polishing performance of silicon oxide film]
The polishing performance of the silicon oxide films of the sheets 1 to 3, 5, 6, 8 to 10 and 12 obtained in the production examples was evaluated as follows.

  Each sheet was cut into a circular shape having a diameter of 38 cm. Then, a groove having a width of 1.0 mm and a depth of 1.0 mm was formed concentrically at intervals of 6.0 mm on the surface of the cut circular sheet, thereby creating a polishing layer. Then, a foamed polyurethane sheet having a thickness of 1.0 mm and an Asker C hardness of 50 was bonded to the back surface of the obtained polishing layer as a cushion layer to prepare a polishing pad. And the silicon oxide film | membrane polishing performance of each obtained polishing pad was evaluated as follows.

  A polishing pad was attached to the polishing surface plate of the polishing apparatus. Then, the polishing pad surface was conditioned for 60 minutes using a diamond dresser while flowing pure water at a rate of 150 mL / min under the conditions of a dresser rotation speed of 140 rpm, a polishing pad rotation speed of 100 rpm, and a dresser load of 5 N. Note that “BC-15” manufactured by MTT Co., Ltd. was used as a polishing apparatus, and a diamond dresser manufactured by Allied Material Co., Ltd. having a diamond count # 200 and a base metal diameter of 190 mm was used.

  Then, 900 parts by mass of pure water is added to 100 parts by mass of polishing slurry containing cerium oxide abrasive grains (“HS-8005” manufactured by Hitachi Chemical Co., Ltd.) under the conditions of a polishing pad rotation number of 100 rpm, a wafer rotation number of 99 rpm, and a polishing pressure of 24 kPa. While supplying the mixed liquid at a rate of 100 mL / min, a silicon wafer with a diameter of 100 mm having a silicon oxide film with an initial film thickness of 1000 nm (a PETEOS silicon oxide film formed by plasma chemical vapor deposition) on the surface is not conditioned. And polished for 60 seconds.

  Then, after conditioning for 30 seconds, the wafer was replaced with a new wafer, and polishing and conditioning were repeated again, and a total of 20 wafers were polished in the same manner.

  And about the silicon wafer which has the silicon oxide film | membrane grind | polished in the 20th sheet | seat, the grinding | polishing speed, grinding | polishing nonuniformity, the presence or absence of a scratch, the surface roughness of a grinding | polishing surface, and the change of pad groove depth were measured. In addition, it carried out similarly to the measuring method in copper film polishing performance evaluation except having measured the film thickness of the silicon oxide film using the nanometrics company made film thickness measuring apparatus "Nanospec Model5100".

  The results are summarized in Table 3.

[Examples 11 to 14 and Comparative Examples 9 to 12: Pattern wafer polishing performance evaluation]
The polishing performance of the patterned wafers of the sheets 1 to 3, 5, 8, 10, 13 and the commercially available foamed polyurethane polishing pad obtained in the production example was evaluated as follows.

  Each sheet obtained in the production example was cut into a circular shape having a diameter of 38 cm. Then, grooves having a width of 1.0 mm and a depth of 1.0 mm were formed concentrically at intervals of 6.0 mm on the surface of the cut circular sheet, and a circular polishing layer having a diameter of 38 cm was produced. And the polishing pad was obtained by bonding together the foamed polyurethane sheet of thickness 1.0mm and C hardness 50 as a cushion layer on the back surface of the obtained polishing layer. In addition, as a commercially available foamed polyurethane polishing pad, a commercially available foamed polyurethane polishing pad having a cushion layer in the lower layer (“IC1400” manufactured by Nitta Haas Co., Ltd.) having the same groove was used. And the pattern wafer polishing performance of each obtained polishing pad was evaluated as follows.

  A polishing pad was attached to the polishing surface plate of the polishing apparatus. Then, the polishing pad surface was conditioned for 60 minutes using a diamond dresser while flowing pure water at a rate of 150 mL / min under the conditions of a dresser rotation speed of 140 rpm, a polishing pad rotation speed of 100 rpm, and a dresser load of 5 N. Note that “BC-15” manufactured by MTT Co., Ltd. was used as a polishing apparatus, and a diamond dresser manufactured by Allied Material Co., Ltd. having a diamond count # 200 and a base metal diameter of 190 mm was used.

  Then, 1900 parts by mass of pure water was added to 100 parts by mass of polishing slurry (“HS-8005” manufactured by Hitachi Chemical Co., Ltd.) containing silicon oxide abrasive grains under the conditions of a polishing pad rotation speed of 100 rpm, a wafer rotation speed of 99 rpm, and a polishing pressure of 24 kPa. Silicon having a diameter of 50 mm having a silicon oxide film (PETEOS silicon oxide film formed by plasma chemical vapor deposition) having an initial film thickness of 1000 nm and no pattern on the surface while supplying the added and mixed liquid at a rate of 100 mL / min. The wafer was polished for 60 seconds without conditioning.

  Then, after conditioning for 30 seconds, the wafer was replaced with a new wafer, and polishing and conditioning were repeated again, and a total of 10 wafers were polished in the same manner.

  Next, one STI polishing evaluation pattern wafer “SKW3-2” made by SKW having a concavo-convex pattern in which linear convex portions and concave portions are alternately and repeatedly arranged was polished under the same conditions as described above. This pattern wafer has various pattern regions, and a pattern having a convex width of 100 μm and a concave width of 100 μm was selected as a measurement target of film thickness and level difference. In this pattern, the initial step between the convex part and the concave part is 550 nm. The convex part is a silicon oxide film having a film thickness of 15 nm on the silicon wafer, a silicon nitride film having a film thickness of 140 nm thereon, and an oxide film having a film thickness of 700 nm thereon. A structure in which a silicon film (HDP silicon oxide film formed by high-density plasma chemical vapor deposition) is laminated, and a pattern recess is formed by etching a silicon wafer to form a groove and then forming a 700 nm thick HDP silicon oxide film It is. In this polishing of the pattern wafer, the time until the silicon oxide film laminated on the silicon nitride film of the pattern convex portion disappeared by the polishing and the step between the convex portion and the concave portion at that time were determined. It can be said that the polishing time and flatness of the pattern wafer are better as the polishing time of the pattern wafer is shorter and the level difference is smaller. The level difference of the pattern wafer was measured using a surface roughness measuring machine (“SJ-400” manufactured by Mitutoyo Corporation), standard stylus, measurement range 80 μm, JIS2001, GAUSS filter, cutoff value λc 2.5 mm, and cutoff. The measurement was performed with the value λs of 8.0 μm, and the value was obtained from the cross-sectional curve.

  The results are summarized in Table 4.

  From the results of Table 4, the polishing pads obtained in Examples 11 to 14 using the sheets obtained in Production Examples 1, 2, 3, and 5 all have a high polishing rate, so the time required for polishing is short. The level difference after polishing was small and excellent in level difference elimination. On the other hand, the polishing rate of the polishing pad obtained in Comparative Example 9 using the sheet 8 obtained in Comparative Production Example 1 having a low porosity was low. Further, the polishing pad obtained in Comparative Example 10 using the sheet 10 obtained in Comparative Production Example 3 having a high porosity is polished because the slurry is not sufficiently supplied to the surface to be polished due to the presence of communication holes. In addition to the reduced speed, the surface roughness of the polished surface was large, so that the level difference after polishing was large and the level difference elimination property was poor. Moreover, since the polishing pad obtained in Comparative Example 11 using the sheet 13 obtained in Comparative Production Example 6 having no voids had low slurry retention, the polishing rate was low.

  The polishing pad and polishing method of the present invention are preferably used for chemical mechanical polishing of a semiconductor substrate, a glass substrate, or an insulating film such as a silicon oxide film formed on the surface of the semiconductor substrate or a glass substrate, or a metal film such as a copper film.

Claims (11)

  A polishing pad comprising, as a polishing layer, a sheet having a porosity of 5 to 35% formed by adhering a plurality of wet heat adhesive fibers containing a wet heat adhesive resin that exhibits adhesiveness by wet heat treatment.   The polishing pad according to claim 1, wherein the D surface has a D hardness of 60 to 80.   The ratio of the number of cross-sectional contours of a fiber bonded to another fiber is 90% or more with respect to the total number of cross-sectional contours of the fiber in the image obtained by photographing the cross-section with a scanning electron microscope. 3. The polishing pad according to 1 or 2. 4. The polishing pad according to claim 1, wherein the sheet has an air permeability of 1 cm ³ / cm ² / sec or less by a fragile method.   The polishing pad according to any one of claims 1 to 4, wherein the wet heat adhesive resin is a saponified product of an ethylene-vinyl ester copolymer having an ethylene copolymerization rate of 10 to 60 mol%. The wet heat adhesive fiber includes a non-wet heat adhesive resin that does not exhibit adhesiveness by wet heat treatment and the wet heat adhesive resin,
The polishing pad according to any one of claims 1 to 5, wherein the wet heat adhesive resin is attached to a surface of a fiber made of the non-wet heat adhesive resin so as to be continuous in a longitudinal direction thereof.   The polishing pad according to claim 6, wherein the wet heat adhesive fiber is a core sheath type composite fiber including a core portion made of the non-wet heat adhesive resin and a sheath portion made of the wet heat adhesive resin.   The polishing pad according to claim 1, wherein the wet heat adhesive fiber has an average fineness of 0.1 to 10 dtex.   The polishing pad according to claim 1, wherein the polishing pad is laminated on a cushion layer on a side opposite to a polishing surface of the polishing layer. The polishing pad according to any one of claims 1 to 9, wherein the polishing pad is used in a polishing step of a semiconductor device and used for polishing.
A polishing pad having an arithmetic mean roughness (Ra) on the polishing surface side of the polishing layer of 1 to 6 μm and a maximum height (Rz) of 10 to 60 μm. Producing a fiber web containing wet heat adhesive fibers containing wet heat adhesive resin that exhibits adhesiveness by wet heat treatment; and
Forming a non-woven fiber base material by adhering the fibers forming the fiber web by wet heat-treating the fiber web;
And a step of forming a sheet by subjecting the non-woven fiber substrate to a heat and pressure treatment so as to have a porosity of 5 to 35%.