POLISHING PAD, POLISHING METHOD, AND METHOD OF MANUFACTURING POLISHING PAD

Description

BACKGROUND

Field of the Technology

The present technology relates to a polishing pad, a polishing method, and a method of manufacturing a polishing pad.

Description of the Related Art

Hitherto, polishing with free abrasive grains has been performed as a method for precisely polishing the surface of an object to be polished, such as: a glass substrate used in, for example, a lens or a display mask blank; a semiconductor wafer including a compound semiconductor wafer, such as silicon, silicon carbide, gallium nitride, gallium oxide, or diamond; a semiconductor device including a silicon oxide insulating film and a metal, such as copper, tungsten, or any other barrier metal; or a hard disk, to perform pattern transfer or planarization. In the polishing with the free abrasive grains, the following mode is generally adopted: a slurry containing the free abrasive grains is supplied between the object to be polished and a polishing pad, and during the supply, the object to be polished and the polishing pad are oscillated and brought into abutment with each other while being individually rotated.

As one kind of performance required for the polishing pad, to improve the flatness of the object to be polished, it is necessary to impart a cushioning property to the polishing pad to improve its adhesiveness with the object to be polished. However, the improvement in cushioning property may cause the shear drop of an end portion in the object to be polished. Accordingly, in, for example, Japanese Patent Laid-Open No. 2007-180550, there is a proposal of a polishing pad in which a polishing layer having relatively high rigidity is laminated below a polishing layer, and a cushion layer is further laminated therebelow.

In recent years, along with an increase in demand for energy savings, an object to be polished, such as a power semiconductor, has started to be improved in hardness. In view of the foregoing, an improvement in performance of a polishing pad has started to be demanded because a related-art polishing pad has a low polishing rate. In addition, along with increasing needs for the shortening of a cycle time in the production of the polishing pad and a rise in difficulty with which a compound semiconductor or the like is processed, there has been required a polishing pad that can withstand an increase in number of revolutions of the polishing pad or the object to be polished, and an increase in polishing pressure therebetween.

However, when an object to be polished is polished with the polishing pad according to Japanese Patent Laid-Open No. 2007-180550 under conditions higher than conventional conditions in terms of the number of revolutions of the polishing pad or the object to be polished, and a polishing pressure between the polishing pad and the object to be polished so that the polishing rate of the polishing pad may be improved, the polishing pad may strongly receive a shear stress to cause fracture at a laminated interface therebetween. Accordingly, the polishing rate and the like have been limited, and hence there has been desired a polishing pad that does not cause fracture at the laminated interface.

SUMMARY

In view of the foregoing, the present disclosure is directed to provide a polishing pad that does not cause fracture due to polishing while achieving relatively high flatness and a relatively high polishing rate. The present disclosure is also directed to provide a polishing method in which fracture does not occur in a polishing pad while relatively high flatness and a relatively high polishing rate are achieved. The present disclosure is also directed to provide a method of manufacturing a polishing pad that does not cause fracture due to polishing while achieving relatively high flatness and a relatively high polishing rate.

The present disclosure is directed to a polishing pad for polishing an object to be polished with free abrasive grains, the polishing pad including a resin sheet having a plurality of bubbles, wherein the resin sheet is an integrally molded article, wherein when a plurality of cross sections, which are parallel to a surface on a side for polishing the object to be polished, are determined every 4 μm in a depth direction toward a surface opposite to the surface on the side for polishing the object to be polished from a measurement result of X-ray CT of the resin sheet, and a total value of areas of openings of recesses derived from the plurality of bubbles per unit area in each of the plurality of cross sections is defined as a bubble area ratio, the resin sheet has, out of the plurality of cross sections, a surface where the bubble area ratio is maximum, wherein when, in a bubble area ratio distribution curve created by setting an axis of abscissa as a depth serving as a distance of each of the plurality of cross sections starting from the surface where the bubble area ratio is maximum, and setting an axis of ordinate as the bubble area ratio of each of the plurality of cross sections, a depth of the surface where the bubble area ratio is maximum is defined as 0%, and a depth of a cross section most distant from the surface where the bubble area ratio is maximum out of the plurality of cross sections is defined as 100%, a minimum value of the bubble area ratio distribution curve is present in a depth range of 10% or more and 80% or less, wherein when a diameter corresponding to a cumulative frequency of 50% of area-equivalent circle diameters of the plurality of bubbles in the surface where the bubble area ratio is maximum is defined as D50 [μm], the D50 in the surface where the bubble area ratio is maximum satisfies the following formula (1): 20 [μm]≤D50≤200 [μm] . . . (1), and wherein the resin sheet has an Asker A hardness of 60 or more, which is measured with an indenter having a diameter of 0.79 mm at a tip thereof at 25° C.

The present disclosure is also directed to a polishing method using a polishing pad for polishing an object to be polished with free abrasive grains, the polishing pad being the above-mentioned polishing pad, the polishing method including exposing one of the surface where the bubble area ratio is maximum or a surface in a vicinity thereof to a surface of the resin sheet when one of the surface where the bubble area ratio is maximum or the surface in the vicinity thereof is unexposed to the surface of the resin sheet.

The present disclosure is also directed to a method of manufacturing a polishing pad, including introducing an uncured resin into a coaxial centrifugal molding apparatus, forming an uncured resin layer on an inner peripheral surface of the coaxial centrifugal molding apparatus with a centrifugal force, and heating and curing the uncured resin layer to produce a resin sheet, wherein the resin sheet is an integrally molded article, wherein the resin sheet has a plurality of bubbles, wherein when a plurality of cross sections, which are parallel to a surface on a side for polishing an object to be polished, are determined every 4 μm in a depth direction toward a surface opposite to the surface on the side for polishing the object to be polished from a measurement result of X-ray CT of the resin sheet, and a total value of areas of openings of recesses derived from the plurality of bubbles per unit area in each of the plurality of cross sections is defined as a bubble area ratio, the resin sheet has, out of the plurality of cross sections, a surface where the bubble area ratio is maximum, wherein when, in a bubble area ratio distribution curve created by setting an axis of abscissa as a depth serving as a distance of each of the plurality of cross sections starting from the surface where the bubble area ratio is maximum, and setting an axis of ordinate as the bubble area ratio of each of the plurality of cross sections, a depth of the surface where the bubble area ratio is maximum is defined as 0%, and a depth of a cross section most distant from the surface where the bubble area ratio is maximum out of the plurality of cross sections is defined as 100%, a minimum value of the bubble area ratio distribution curve is present in a depth range of 10% or more and 80% or less, wherein when a diameter corresponding to a cumulative frequency of 50% of area-equivalent circle diameters of the plurality of bubbles in the surface where the bubble area ratio is maximum is defined as D50 [μm], the D50 satisfies the following formula (1): 20 [μm]≤D50≤200 [μm] . . . (1), and wherein the resin sheet has an Asker A hardness of 60 or more, which is measured with an indenter having a diameter of 0.79 mm at a tip thereof at 25° C.

Features of the present disclosure will become apparent from the following description of embodiments with reference to the attached drawings. The following description of embodiments is described by way of example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view for schematically illustrating a polishing pad according to the present disclosure.

FIG. 2A is a perspective view for schematically illustrating a recess and an opening derived from a bubble in a surface where a bubble area ratio is maximum or a surface in the vicinity thereof according to the present disclosure.

FIG. 2B is a cross-sectional view for schematically illustrating the recess and the opening derived from the bubble in the surface where the bubble area ratio is maximum or the surface in the vicinity thereof according to the present disclosure.

FIG. 3 is a view for describing the area-equivalent circle diameter of the opening of a recess derived from a bubble according to the present disclosure.

FIG. 4 is a schematic view for illustrating a configuration example of a centrifugal molding machine to be used in centrifugal molding according to the present disclosure.

FIG. 5 is a view for illustrating the outline of a method of defining a measurement surface.

DESCRIPTION OF THE EMBODIMENTS

In the present disclosure, the description “XX or more and YY or less” or “XX to YY” representing a numerical range means a numerical range including a lower limit and an upper limit that are end points unless otherwise stated.

First Embodiment

A first embodiment is directed to a polishing pad.

According to an investigation made by the inventors, one cause for the occurrence of fracture at the laminated interface in the polishing pad according to Japanese Patent Laid-Open No. 2007-180550 was assumed to be due to the fact that the configuration of the polishing pad according to Japanese Patent Laid-Open No. 2007-180550 was a laminated molded article. That is, the polishing pad is a laminated molded article formed of three layers, and the respective layers differ from each other in compressibility. Thus, a strong shear stress is applied to an interface between the layers. Accordingly, when polishing is performed by applying a high number of revolutions and a high polishing pressure through use of such polishing pad, the polishing pad may fracture.

The inventors have recognized that, to polish an object to be polished with free abrasive grains under the application of a high number of revolutions of a polishing pad or the object to be polished and a high polishing pressure therebetween, it is necessary to develop a technology for manufacturing an integrally molded article rather than a laminated molded article, which is considered to be a cause of fracture. In view of the foregoing, as a result of repeated investigations to prevent the occurrence of the fracture, the inventors have found that the following polishing pad can well achieve the object.

A polishing pad of the present disclosure is a polishing pad for polishing an object to be polished with free abrasive grains, the polishing pad including a resin sheet having a plurality of bubbles, wherein the resin sheet is an integrally molded article, wherein when a plurality of cross sections, which are parallel to a surface on a side for polishing the object to be polished, are determined every 4 μm in a depth direction toward a surface opposite to the surface on the side for polishing the object to be polished from a measurement result of X-ray CT of the resin sheet, and a total value of areas of openings of recesses derived from the plurality of bubbles per unit area in each of the plurality of cross sections is defined as a bubble area ratio, the resin sheet has, out of the plurality of cross sections, a surface where the bubble area ratio is maximum, wherein when, in a bubble area ratio distribution curve created by setting an axis of abscissa as a depth serving as a distance of each of the plurality of cross sections starting from the surface where the bubble area ratio is maximum, and setting an axis of ordinate as the bubble area ratio of each of the plurality of cross sections, a depth of the surface where the bubble area ratio is maximum is defined as 0%, and a depth of a cross section most distant from the surface where the bubble area ratio is maximum out of the plurality of cross sections is defined as 100%, a minimum value of the bubble area ratio distribution curve is present in a depth range of 10% or more and 80% or less, wherein when a diameter corresponding to a cumulative frequency of 50% of area-equivalent circle diameters of the plurality of bubbles in the surface where the bubble area ratio is maximum is defined as D50 [μm], the D50 in the surface where the bubble area ratio is maximum satisfies the following formula (1): 20 [μm]≤D50≤200 [μm] . . . (1), and wherein the resin sheet has an Asker A hardness of 60 or more, which is measured with an indenter having a diameter of 0.79 mm at a tip thereof at 25° C.

According to the foregoing, there can be provided a polishing pad, which is so excellent in durability as to be free from causing fracture or the like while exhibiting a polishing rate equal to or higher than a conventional polishing rate. The inventors have assumed the reason for the foregoing to be as described below.

The polishing pad of the present disclosure is a polishing pad for polishing an object to be polished with free abrasive grains, the polishing pad including a resin sheet having a plurality of bubbles, the resin sheet being an integrally molded article. To suppress the fracture of the polishing pad, it is first important that the polishing pad be an integrally molded article instead of a laminated molded article. A cross-sectional view for schematically illustrating the polishing pad 1 of the present disclosure is illustrated in FIG. 1. The resin sheet of the polishing pad 1 includes such bubbles 2 as illustrated in FIG. 1.

That is, the term “integrally molded article” means a continuous component formed of a single material and a single layer. Even when the polishing pad receives a shear stress at the time of polishing, in the case where there is no interface in the polishing pad, the polishing pad hardly receives stress concentration, and hence hardly fractures.

In the present disclosure, a plurality of cross sections in the range of from the surface on the side for polishing the object to be polished to the opposite surface are determined from the measurement result of the X-ray CT of the resin sheet by using a plurality of planes arranged every 4 μm at an angle parallel to a plane when the resin sheet is placed stationary on the plane with the surface opposite to the surface on the side for polishing the object to be polished as a lower side, and the total value of the areas of the openings of the recesses derived from the plurality of bubbles per unit area in each of the plurality of cross sections is defined as the bubble area ratio. At this time, in the present disclosure, the resin sheet has, out of the plurality of cross sections, the surface where the bubble area ratio is maximum.

A bubble in the surface where the bubble area ratio is maximum or a surface in the vicinity thereof is schematically illustrated in each of FIG. 2A and FIG. 2B. Although a recess derived from a single bubble is illustrated in each of the figures, recesses derived from a plurality of bubbles actually exist. As illustrated in each of the figures, the bubble in the surface where the bubble area ratio is maximum or the surface in the vicinity thereof, which is represented by reference numeral 5, includes an opening 4 of the recess derived from the bubble and a recess 3 derived from the bubble.

As described above, the bubble area ratio is defined as the ratio of the total value of the area-equivalent circles of the openings of the recesses derived from the plurality of bubbles per unit area in each of the plurality of cross sections, the cross sections being determined by: fixing the surface opposite to the surface on the side for polishing the object to be polished to a flat platen; and obtaining a plurality of cross sections parallel to the plane of the platen every 4 μm in a depth direction toward the surface opposite to the surface on the side for polishing the object to be polished.

In the present disclosure, when, in the bubble area ratio distribution curve created by setting the axis of abscissa as a depth serving as the distance of each of the plurality of cross sections starting from the surface where the bubble area ratio is maximum, and setting the axis of ordinate as the bubble area ratio of each of the plurality of cross sections, the depth of the surface where the bubble area ratio is maximum is defined as 0%, and the depth of the cross section most distant from the surface where the bubble area ratio is maximum out of the plurality of cross sections is defined as 100%, the minimum value of the bubble area ratio distribution curve is present in the depth range of 10% or more and 80% or less. The minimum value is preferably present in the depth range of 30% or more and 80% or less, and is more preferably present in the depth range of 30.3% or more and 79.4% or less.

When the minimum value of the bubble area ratio distribution curve is present in the depth range of 10% or more and 80% or less, while the polishing pad is an integrally molded article, when the polishing pad is compared to a laminated molded article, a region around the minimum value serves as a pseudo-rigid layer, and a pseudo-polishing layer and a pseudo-sponge layer can be formed above and below the pseudo-rigid layer. As a result, the polishing pad can be suppressed from fracturing while achieving high flatness and a high polishing rate.

In addition, in the present disclosure, when the diameter corresponding to a cumulative frequency of 50% of the area-equivalent circle diameters of the plurality of bubbles in the surface where the bubble area ratio is maximum is defined as D50 [μm], the D50 in the surface where the bubble area ratio is maximum satisfies the following formula (1).

20 [ μm ] ≤ D ⁢ 5 ⁢ 0 ≤ 200 [ μm ] ( 1 )

In the present disclosure, the D50 is preferably 60 μm or more and 160 μm or less, more preferably 101 μm or more and 151 μm or less.

When the D50 falls within the above-mentioned ranges, the polishing rate of the polishing pad is maintained over a long period of time. When the D50 is less than 20 μm, the polishing pad cannot sufficiently hold the abrasive grains, and hence the polishing rate reduces.

Meanwhile, when the D50 is more than 200 μm, the rigidity of the polishing pad cannot be maintained, and hence the flatness thereof reduces.

Herein, a view for describing the area-equivalent circle diameter of the opening of a recess derived from a bubble in the present disclosure is illustrated in FIG. 3. An area-equivalent circle diameter 8 of the opening of the recess derived from the bubble may be determined by fitting an area-equivalent circle 7 of an opening 6 of the recess derived from the bubble to the opening of the recess derived from the bubble as in a known method.

In addition, in the polishing pad of the present disclosure, the resin sheet has an Asker A hardness of 60 or more, which is measured with an indenter having a diameter of 0.79 mm at a tip thereof at 25° C., and the Asker A hardness is preferably 90 or more. Thus, the polishing pad can be suppressed from fracturing while exhibiting a high polishing rate. Meanwhile, when the Asker A hardness is less than 60, fracture may occur under the conditions of a high number of revolutions of the polishing pad or the object to be polished and a high polishing pressure therebetween.

In addition, in the present disclosure, the average value of the bubble area ratios (average bubble area ratio) in a depth region of 0% or more and 20% or less in the bubble area ratio distribution curve is preferably 30% or more and 95% or less, more preferably 30% or more and 50% or less, still more preferably 32.0% or more and 45.4% or less. With such setting, the polishing pad can be suppressed from fracturing while exhibiting a high polishing rate.

Subsequently, in the present disclosure, the average value of the bubble area ratios (average bubble area ratio) in the depth region of 20% or more and 50% or less in the bubble area ratio distribution curve is preferably 0% or more and 10% or less, more preferably 3% or more and 10% or less, still more preferably 3.4% or more and 9.5% or less. With such setting, the polishing pad exhibits high rigidity, and hence can effectively suppress the shear drop of an end portion.

In the present disclosure, the average value of the bubble area ratios (average bubble area ratio) in a depth region of 50% or more and 100% or less in the bubble area ratio distribution curve is preferably 15% or more and 50% or less, more preferably 15% or more and 35% or less, still more preferably 16.3% or more and 33.3% or less.

With such setting, the cushioning property of the entirety of the polishing pad can be maintained high, and hence the flatness thereof can be improved.

A case in which the average bubble area ratio of the polishing pad is set within the above-mentioned ranges is preferred because both the flatness and polishing rate thereof can be achieved at higher levels without occurrence of the fracture of the sheet.

Second Embodiment

A second embodiment is directed to a method of manufacturing a polishing pad.

A method of manufacturing a polishing pad of the present disclosure is a method of manufacturing a polishing pad, the method including introducing an uncured resin into a coaxial centrifugal molding apparatus, forming an uncured resin layer on an inner peripheral surface of the coaxial centrifugal molding apparatus with a centrifugal force, and heating and curing the uncured resin layer to produce a resin sheet, wherein the resin sheet is an integrally molded article, wherein the resin sheet has a plurality of bubbles, wherein when a plurality of cross sections, which are parallel to a surface on a side for polishing an object to be polished, are determined every 4 μm in a depth direction toward a surface opposite to the surface on the side for polishing the object to be polished from a measurement result of X-ray CT of the resin sheet, and a total value of areas of openings of recesses derived from the plurality of bubbles per unit area in each of the plurality of cross sections is defined as a bubble area ratio, the resin sheet has, out of the plurality of cross sections, a surface where the bubble area ratio is maximum, wherein when, in a bubble area ratio distribution curve created by setting an axis of abscissa as a depth serving as a distance of each of the plurality of cross sections starting from the surface where the bubble area ratio is maximum, and setting an axis of ordinate as the bubble area ratio of each of the plurality of cross sections, a depth of the surface where the bubble area ratio is maximum is defined as 0%, and a depth of a cross section most distant from the surface where the bubble area ratio is maximum out of the plurality of cross sections is defined as 100%, a minimum value of the bubble area ratio distribution curve is present in a depth range of 10% or more and 80% or less, wherein when a diameter corresponding to a cumulative frequency of 50% of area-equivalent circle diameters of the plurality of bubbles in the surface where the bubble area ratio is maximum is defined as D50 [μm], the D50 satisfies the following formula (1): 20 [μm]≤D50≤200 [μm] . . . (1), and wherein the resin sheet has an Asker A hardness of 60 or more, which is measured with an indenter having a diameter of 0.79 mm at a tip thereof at 25° C.

Description of the items described in the first embodiment may be omitted because the description is redundant.

The method of manufacturing a polishing pad of the present disclosure includes introducing the uncured resin into the coaxial centrifugal molding apparatus, forming the uncured resin layer on the inner peripheral surface of the coaxial centrifugal molding apparatus with a centrifugal force, and heating and curing the uncured resin layer to produce the resin sheet. Such setting enables the minimum value of the bubble area ratio distribution curve to be present in the depth range of 10% or more and 80% or less.

In addition, in the method of manufacturing a polishing pad of the present disclosure, the centrifugal force applied by the coaxial centrifugal molding apparatus is preferably 200 m/s² or more and 4,000 m/s² or less, and the viscosity of the uncured resin to be introduced into the coaxial centrifugal molding apparatus is preferably 1,000 mPa·s or more and 20,000 mPa·s or less. Such setting enables the formation of a bubble distribution for forming recesses derived from bubbles in the surface of the resin sheet where the bubble area ratio is maximum or a surface in the vicinity thereof. In the present disclosure, the term “surface in the vicinity thereof” means a surface in the range of ±200 μm in a depth direction from the surface where the bubble area ratio is maximum. The bubble distribution is continuous. Accordingly, it is conceivable that the surface in the vicinity thereof has bubble-derived recesses, which are substantially the same as those of the surface where the bubble area ratio is maximum, and hence exhibits substantially the same operations and effects.

Such bubble distribution control as described above is achieved by comprehensively controlling foaming by heating from the cylindrical mold surface of the coaxial centrifugal molding apparatus and the movement of the bubbles by the centrifugal force based on: prescriptive factors, such as the viscosity, foaming amount, and foaming timing of the resin, and the ratio control of a competitive reaction between the curing and foaming thereof, and operating conditions, such as a centrifugal force strength level and the time period for which the centrifugal force is applied.

A material for the resin sheet described in the present disclosure is specifically described below.

The material for the resin sheet is not particularly limited as long as the material is a thermosetting resin, and one or two or more kinds of, for example, a polyurethane resin composition, a polyacrylic resin composition, a polycarbonate resin composition, a polyamide resin composition, a polyester resin composition, and a polyepoxy resin composition may be used.

The polyurethane resin composition includes a structure in which an active hydrogen group-containing compound and an isocyanate group-containing compound are alternately repeated as constituent units.

The active hydrogen group-containing compound is an organic compound having an active hydrogen group that can react with an isocyanate group. Specific examples of the active hydrogen group include functional groups, such as a hydroxy group, a primary amino group, a secondary amino group, and a thiol group. The active hydrogen groups may be present in plural kinds and in a plural number in the active hydrogen group-containing compound.

Examples of the active hydrogen group-containing compound include a polyol compound and a polyamine compound.

Examples of the polyol compound include a linear aliphatic glycol, a branched aliphatic glycol, an alicyclic diol, a polyfunctional polyol, a polyester polyol, a polyester polycarbonate polyol, a polyether polyol, a polycarbonate polyol, and a polyfunctional polyol polymer.

Examples of the linear aliphatic glycol include 1,4-benzenedimethanol, 1,4-bis(2-hydroxyethoxy)benzene, ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, and 1,9-nonanediol.

Examples of the branched aliphatic glycol include neopentyl glycol, 3-methyl-1,5-pentanediol, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, and 2-methyl-1,8-octanediol.

Examples of the alicyclic diol include 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, and hydrogenated bisphenol A.

Examples of the polyfunctional polyol include glycerin, trimethylolpropane, tributylolpropane, pentaerythritol, and sorbitol.

Examples of the polyester polyol include polyethylene adipate glycol, polybutylene adipate glycol, polycaprolactone polyol, and polyhexamethylene adipate glycol.

The polyester polycarbonate polyol is, for example, a reaction product of a polyester glycol, such as polycaprolactone polyol, and an alkylene carbonate. The polyester polycarbonate polyol may also be, for example, a reaction product obtained by further causing a reaction mixture, which is obtained by causing ethylene carbonate to react with a polyhydric alcohol, to react with an organic dicarboxylic acid.

Examples of the polyether polyol include polytetramethylene ether glycol, polypropylene glycol, polyethylene glycol, and ethylene oxide-added polypropylene polyol.

The polycarbonate polyol is, for example, a reaction product of a diol, such as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, polyethylene glycol, polypropylene glycol, or polytetramethylene ether glycol, and phosgene, a diaryl carbonate (e.g., diphenyl carbonate), or a cyclic carbonate (e.g., propylene carbonate).

Examples of the polyamine compound include 4,4′-methylenebis(2-chloroaniline) (MOCA), 4,4′-methylenedianiline, trimethylene bis(4-aminobenzoate), 2-methyl-4,6-bis(methylthio)benzene-1,3-diamine, 2-methyl-4,6-bis(methylthio)-1,5-benzenediamine, 2,6-dichloro-p-phenylenediamine, 4,4′-methylenebis(2,3-dichloroaniline), 3,5-bis(methylthio)-2,4-toluenediamine, 3,5-bis(methylthio)-2,6-toluenediamine, 3,5-diethyltoluene-2,4-diamine, 3,5-diethyltoluene-2,6-diamine, trimethylene glycol-di-p-aminobenzoate, 1,2-bis(2-aminophenylthio) ethane, and 4,4′-diamino-3,3′-diethyl-5,5′-dimethyldiphenylmethane.

Examples of the isocyanate group-containing compound include an aromatic diisocyanate, an aliphatic diisocyanate, an alicyclic diisocyanate, and a urethane prepolymer.

Examples of the aromatic diisocyanate include tolylene diisocyanate (TDI), 1,5-naphthalene diisocyanate, xylylene diisocyanate, 1,3-phenylene diisocyanate, and 1,4-phenylene diisocyanate. The examples of the aromatic diisocyanate also include diphenylmethane diisocyanate (MDI) and a modified product of diphenylmethane diisocyanate (MDI).

Examples of the modified product of diphenylmethane diisocyanate (MDI) include a carbodiimide-modified product, a urethane-modified product, an allophanate-modified product, a urea-modified product, a biuret-modified product, an isocyanurate-modified product, and an oxazolidone-modified product. Such modified product is specifically, for example, carbodiimide-modified diphenylmethane diisocyanate (carbodiimide-modified MDI).

Examples of the aliphatic diisocyanate include ethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and hexamethylene diisocyanate (HDI).

Examples of the alicyclic diisocyanate include 1,4-cyclohexane diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, isophorone diisocyanate, norbornane diisocyanate, and methylenebis(4,1-cyclohexylene) diisocyanate.

A urethane prepolymer is a polymer formed by bonding a polyol and a polyisocyanate, and has an isocyanate group as a terminal group.

The resin sheet may contain a filler.

Specific examples of the filler include: inorganic powder, such as aluminum oxide, cerium oxide, titanium oxide, germanium oxide, silicon carbide, calcium carbonate, silica, carbon black, diamond, talc, or clay; inorganic fibers, such as a glass fiber and a carbon fiber; metal powder, such as iron, copper, aluminum, or nickel; metal fibers, such as an iron fiber, a copper fiber, and an aluminum fiber; organic fibers, such as a polyimide fiber, a TEFLON (trademark) fiber, and a polyester fiber; organic pigments such as an azo-based pigment; and other materials generally used in polymer chemistry, such as a gas, a fluid, and resin powder. A plurality of kinds of those fillers may be simultaneously incorporated into the resin sheet.

The amount of the filler is preferably 0.1 parts by mass or more and 40.0 parts by mass or less with respect to 100 parts by mass of the resin.

The particle diameter of the filler is preferably 10 nm or more and 500 nm or less.

The resin sheet may contain a foam stabilizer.

The foam stabilizer is, for example, a silicone-based surfactant, and one or two or more kinds of such surfactants may be used. Examples thereof include “Toray Silicone SH-193,” “Toray Silicone SH-192,” and “Toray Silicone SH-190” manufactured by Dow Corning Toray Co., Ltd.

In addition to the above-mentioned materials, a stabilizer such as an antioxidant, a lubricant, a pigment, a filler, an antistatic agent, and other additives may each be added to the resin sheet as required.

Examples of a method of forming the recesses derived from the plurality of bubbles in the surface of the resin sheet of the polishing pad where the bubble area ratio is maximum or the surface in the vicinity thereof include: mechanical foaming in which an inert gas is mixed into the uncured resin; and chemical foaming in which a foaming agent typified by water is added thereto. A hollow microcapsule or the like, which itself becomes a bubble, may also be added thereto.

Examples of the inert gas to be used in the mechanical foaming include nitrogen, oxygen, a carbon dioxide gas, a noble gas, such as helium or argon, and a mixed gas thereof such as air.

As a stirring apparatus for dispersing the inert gas in the form of fine bubbles in the mechanical foaming, a known stirring apparatus may be used without any particular limitation, and specific examples thereof include a homogenizer, a dissolver, a biaxial planetary mixer (planetary mixer), and a mechanical froth foaming machine. The shape of the stirring blade of the stirring apparatus is also not particularly limited, and the stirring blade is, for example, a whipper-type stirring blade.

Examples of the foaming agent in the chemical foaming include, in addition to water, a foaming agent containing, as a main component, a hydrocarbon having 5 or 6 carbon atoms, an organic chemical foaming agent, and a halogenated hydrocarbon.

Examples of the hydrocarbon include: chain hydrocarbons, such as butane, n-pentane, and n-hexane; and alicyclic hydrocarbons, such as cyclopentane and cyclohexane.

Examples of the organic chemical foaming agent include an azo-based compound, a nitroso compound, and a sulfonyl hydrazide compound.

Examples of the azo-based compound include azodicarbonamide, azobisisobutyronitrile, diazoaminobenzene, and barium azodicarboxylate.

Examples of the nitroso compound include N,N′-dinitrosopentamethylenetetramine and N,N′-dinitroso-N,N′-dimethylterephthalamide.

Examples of the sulfonyl hydrazide compound include p,p′-oxybis(benzenesulfonyl hydrazide) and p-toluenesulfonyl hydrazide.

Examples of the halogenated hydrocarbon include methylene chloride and hydrofluorocarbons (HFCs).

The hollow microcapsules include pre-expanded hollow microcapsules and unexpanded hollow microcapsules. The unexpanded hollow microcapsules are heat-expandable microcapsules, and can be heated and expanded.

Examples of commercially available hollow microcapsules include, but not limited to, an Expancel series (product name, manufactured by Akzo Nobel N.V.) and Matsumoto Microsphere (product name, manufactured by Matsumoto Yushi-Seiyaku Co., Ltd.).

A hollow microcapsule obtained through synthesis by an ordinary method may also be used. A material for the outer shell of a hollow microcapsule 4A is not particularly limited, and examples thereof include polyvinyl alcohol, polyvinylpyrrolidone, poly(meth)acrylic acid, polyacrylamide, polyethylene glycol, polyhydroxyether acrylate, a maleic acid copolymer, polyethylene oxide, polyurethane, poly(meth)acrylonitrile, polyvinylidene chloride, polyvinyl chloride, and an organic silicone-based resin, and a copolymer obtained by combining two or more kinds of monomers for forming these resins.

A method of manufacturing the resin sheet of the polishing pad is, for example, a centrifugal molding method.

The centrifugal molding method is a method of molding a thin-walled cylindrical sheet by: introducing a raw material for the uncured resin sheet into a cylindrical mold; rotating the mold at a high speed to form a resin raw material layer on its inner peripheral surface with a centrifugal force; and heating and curing the layer. The cylindrical sheet thus obtained is removed as a molded article from the cylindrical mold, subjected to secondary crosslinking as required, and cut into desired dimensions and a desired shape as required. Examples of a method for the cutting include known cutting methods, such as a clicker blade, a laser, and a cutter.

A configuration example of a centrifugal molding machine to be used in centrifugal molding is illustrated in FIG. 4. That is, as the centrifugal molding machine, there may be used a machine formed so as to include: a driving shaft 10 rotated by a motor or the like; a cylindrical mold 11 in the form of a cylindrical cup attached to, and rotatably supported by, the tip of the driving shaft; a heat source 12 such as a heater fixedly arranged on the outer periphery of the cylindrical mold 11; and a hatch 9 opened in a case covering the cylindrical mold 11 and the heat source 12.

The temperature of the cylindrical mold should be appropriately changed in accordance with the viscosity and foaming characteristics of the material to be used. For example, when the curing speed of the resin sheet is wished to be increased, the temperature should be raised. However, the temperature needs to be changed in accordance with purposes because a balance between the foaming and curing of the resin sheet shows different characteristics from material to material.

In addition, the number of revolutions of the cylindrical mold controls the effect of a centrifugal force caused by rotation, but the number should also be appropriately changed in accordance with the viscosity and foaming characteristics of the material to be used. For example, when it is desired to increase the foaming rate of the resin sheet on the inner surface side of the cylindrical mold, the number of revolutions may be increased to increase the centrifugal force, to thereby promote the accumulation of bubbles. In addition, when it is desired to reduce the foaming diameter of the resin sheet, the number of revolutions may be increased to increase the centrifugal force, to thereby promote the rupture of large-diameter bubbles. The number of revolutions may also be changed in a stepwise manner in accordance with the state of the curing or foaming of the resin.

The rotation time of the cylindrical mold should be appropriately controlled in accordance with the degree to which the effect of the above-mentioned centrifugal force is exhibited.

The method of manufacturing a polishing pad of the present disclosure preferably includes exposing the surface where the bubble area ratio is maximum or a surface in the vicinity thereof to the surface of the resin sheet when the surface where the bubble area ratio is maximum or the surface in the vicinity thereof is unexposed to the surface of the resin sheet. At least, the surface where the bubble area ratio is maximum or the surface in the vicinity thereof needs to be exposed to the surface of the resin sheet before its use as a polishing pad. Any method may be used as a method for the exposure as long as the cross section can be exposed. Herein, the term “surface in the vicinity thereof” means a surface in the range of ±200 μm in the depth direction from the surface where the bubble area ratio is maximum. The bubble distribution is continuous. Accordingly, it is conceivable that the surface in the vicinity thereof has bubble-derived recesses, which are substantially the same as those of the surface where the bubble area ratio is maximum, and hence exhibits substantially the same operations and effects.

Third Embodiment

A third embodiment is directed to a polishing method.

A polishing method of the present disclosure is a polishing method using a polishing pad for polishing an object to be polished with free abrasive grains, the polishing pad being the polishing pad of the present disclosure, the polishing method including exposing the surface where the bubble area ratio is maximum or a surface in the vicinity thereof to the surface of the resin sheet when the surface where the bubble area ratio is maximum or the surface in the vicinity thereof is unexposed to the surface of the resin sheet.

Description of the items described in the first embodiment and the second embodiment may be omitted because the description is redundant.

The polishing method of the present disclosure is a polishing method using a polishing pad for polishing an object to be polished with free abrasive grains, the polishing pad being the polishing pad of the present disclosure. A specific example thereof is described.

First, the polishing method of the present disclosure includes exposing the surface where the bubble area ratio is maximum or the surface in the vicinity thereof to the surface of the resin sheet when the surface where the bubble area ratio is maximum or the surface in the vicinity thereof is unexposed to the surface of the resin sheet. At the time of polishing, the surface where the bubble area ratio is maximum or the surface in the vicinity thereof needs to be exposed to the surface of the resin sheet. Any method may be used as a method for the exposure as long as the cross section can be exposed. Herein, the term “surface in the vicinity thereof” means a surface in the range of ±200 μm in the depth direction from the surface where the bubble area ratio is maximum.

Next, the object to be polished is held on the holding platen of a polishing machine. Next, the polishing pad is mounted on a polishing platen arranged to face the holding platen. When the polishing pad has a double-sided tape and release paper, at the time of the mounting of the polishing pad on the polishing platen, the release paper is peeled from the double-sided tape to expose the pressure-sensitive adhesive layer of the double-sided tape, and then the exposed pressure-sensitive adhesive layer is brought into contact with, and pressed against, the polishing platen.

Then, the object to be polished is polished with the free abrasive grains by: supplying a polishing slurry containing the abrasive grains as required between the object to be polished and the polishing pad; and rotating the polishing platen or the holding platen while pressing the object to be polished against the polishing pad at a predetermined polishing pressure.

The polishing slurry is not particularly limited, and may be a slurry to be used in conventional chemical mechanical polishing, and general abrasive grains may be used as the abrasive grains in accordance with the object to be polished. Examples thereof include ceria, silica, alumina, manganese oxide, diamond, and organic-inorganic composite abrasive grains. The abrasive grains are used alone or in combination thereof.

[Measurement Methods and Calculation Methods for Respective Physical Properties]

Measurement methods and calculation methods for various physical properties of the polishing pad and the material are described below.

<Measurement Method for Diameter Corresponding to Cumulative Frequency of 50% of Area-Equivalent Circle Diameters of Openings of Recesses Derived from Bubbles, Measurement Method for Bubble Area Ratio, and Method of Drawing Bubble Area Ratio Distribution Curve>

The resin sheet (a segment 13 of a resin sheet for X-ray CT imaging) cut into a strip having a width of 2 cm and a length of 5 cm was set in an X-ray CT apparatus (TXS-32300 FDHS manufactured by Toshiba IT Control Systems Corporation), and X-ray CT measurement was performed. Measurement conditions are described below.

• • X-ray tube voltage [KV]: 75.000
  • X-ray tube voltage [mA]: 0.053
  • Data mode: CONE
  • FC function: Laks
  • Scan mode: FULL
  • Number of views: 2,000
  • Slice interval: 0.004
  • Integration: 1

Shape data obtained for an X-ray CT imaging region 14 in the above-mentioned measurement was analyzed with image processing software VG Studio Max 2.1 manufactured by Nihon Visual Science Volume Graphics Co., Ltd., and a region measuring 4.0 mm by 4.0 mm on the maximum-area surface of the resin sheet was sliced every 4.0 μm in its thickness direction. Thus, a measurement surface 15, which was the sliced X-ray CT imaging region, was obtained. An outline of a method of defining the measurement surface up to this point is illustrated in FIG. 5.

A bubble-derived recess and a resin portion were classified through binarization processing by contrast adjustment on each obtained cut surface, and an area-equivalent circle diameter was calculated for a recess derived from a bubble having a diameter of 2 μm or more (an opening 16 of the bubble-derived recess on the measurement surface), followed by the calculation of a diameter corresponding to a cumulative frequency of 50%.

In addition, the bubble-derived recess and the resin portion were classified through binarization processing by contrast adjustment on each obtained cut surface, and the total value of the areas of the openings of the recesses was calculated, and was divided by the area of the entire region. Thus, a bubble area ratio, which was the area ratio of the openings of the bubble-derived recesses, was calculated. The surface where the bubble area ratio was maximum was adopted as the measurement surface, and the measurement surface was determined from the data.

In addition, a bubble area ratio distribution curve was drawn by plotting the respective depths of the plurality of cross sections starting from the surface where the bubble area ratio was maximum against an axis of abscissa, and plotting the respective bubble area ratios of the cross sections against an axis of ordinate.

<Asker A Hardness of Resin Sheet at 25° C.>

To eliminate the influence of a sheet-placing stand on a measured value, the resin sheet laminated to a thickness of 6 mm or more was allowed to stand still for 16 hours under an environment at 25° C. and a humidity of 50%±5%. After that, the hardness of the resin sheet was measured five times with a type A durometer conforming to JIS K 6253 (Asker A type manufactured by Kobunshi Keiki Co., Ltd.), and the average value of the measured values was adopted as the Asker A hardness of the resin sheet.

<Evaluation of Fracture Easiness of Polishing Pad, and Evaluation Methods for Local Flatness, Shear Drop, and Polishing Rate of Object to be Polished>

First, when the surface where the bubble area ratio was maximum or a surface in the vicinity thereof was unexposed to the surface of the resin sheet of the produced polishing pad 1, the surface where the bubble area ratio was maximum or the surface in the vicinity thereof was exposed. Then, so-called X-Y groove processing (lattice groove processing) having a width of 2.0 mm, a pitch of 15 mm, and a depth of 0.5 mm was performed on the surface of the produced polishing pad 1, and the processed pad was mounted on each of the upper and lower platens of a double-sided polishing apparatus (manufactured by Fujikoshi Machinery Corp.).

Next, the initial dressing of the pad was performed for 1 minute by attaching a #100 diamond plate to a polishing head under the following conditions: the number of revolutions of each of the head and a platen was 30 rpm, and a polishing pressure was 70 g/cm². No dressing was performed thereafter throughout the evaluation.

Next, 20 batches of polishing were performed in the polishing process of the (100) surfaces of five silicon single crystal wafers each having a diameter of 300 mmφ under the following conditions while a polishing time per batch was set to 30 minutes: the number of revolutions of each of the polishing head and the platen was 30 rpm, and the polishing pressure was 210 g/cm². The flatness (local flatness and shear drop) of the 20th batch was measured, an average value was calculated for the five wafers, and a polishing rate was also measured at the same time. A colloidal silica-containing alkaline solution having a pH of 10.5 (manufactured by Fujimi Incorporated) was supplied as a slurry at 5 L/min.

The local flatness and the shear drop were evaluated as a site front least squares range (SFQR) and the SFQR of a wafer outer peripheral portion, respectively with a flatness-measuring apparatus (Nanometro 300TT-A manufactured by Kuroda Seiko Co., Ltd.). At this time, a SFQR in the range of 8.0×26.0 mm² near the center of the wafer was adopted as the local flatness. In addition, the shear drop was determined as a SFQR for each section defined as follows: the outermost periphery of the wafer having a width of 1 mm was excluded; and the range of from the peripheral edge portion of the resultant to a portion 35 mm inward therefrom was divided by radiating lines arranged at intervals of 5° from the center of the wafer serving as a starting point.

In addition, additional 80 batches of polishing similar to the foregoing were performed, and a cross section of the pad was observed, followed by the observation of whether or not fracture or a crack occurred therein.

EXAMPLES

The present disclosure is more specifically described below by way of Examples. However, the present disclosure is by no means limited by Examples. In the following formulations, the term “part(s)” means “part(s) by mass” unless otherwise specified.

Example 1

237 Parts by mass of 2,4-tolylene diisocyanate (TDI), 412 parts by mass of polytetramethylene ether glycol (PTMG) having a number-average molecular weight of about 1,000, and 40 parts by mass of diethylene glycol were caused to react with each other, and the reaction product was heated, and was degassed under reduced pressure to provide a prepolymer. The isocyanate content of the prepolymer was 9.1%.

55.0 Parts by mass of the prepolymer, 45.0 parts by mass of diethyl toluene diamine (DETDA), 5.0 parts by mass of water, 0.006 parts by mass of TOYOCAT (trademark) ET (manufactured by Tosoh Corporation), and 2.0 parts by mass of a silicone-based foam stabilizer SH-193 were mixed to provide an uncured resin solution.

340 Grams of the uncured resin solution was heated to 110° C. on a preformed silicone rubber release layer, and was poured into a cylindrical mold having a diameter of 450 mm and a depth of 320 mm in a centrifugal molding machine rotating at 1,200 rpm. While the number of revolutions was maintained at 1,200 rpm for 30 minutes from the time point when the pouring was completed, the solution was cured under heating. After that, the cured product was removed from the mold to provide a resin sheet 1 having a thickness of 1.50 mm.

A double-sided tape having adhesive layers (material: acrylic resin) on both the surfaces of a PET-made substrate, and further having release paper on one surface thereof was bonded to a surface opposite to the surface of the resultant resin sheet 1 where its bubble area ratio was maximum or a surface in the vicinity thereof via the adhesive layer opposite to the release paper, and the laminate was cut into a circular shape having a diameter of 300 mm to provide a polishing pad 1. Table 1-1 shows the formulation and manufacturing conditions of the resultant polishing pad 1. In addition, Table 2-1 shows the physical properties of the resultant polishing pad 1.

	TABLE 1-1
	Polishing	Polishing	Polishing	Polishing	Polishing	Polishing
	pad 1	pad 2	pad 3	pad 4	pad 5	pad 6

Formulation	TDI	237	237	237	237	237	237
	[part(s) by mass]
	PTMG	412	412	412	412	412	412
	[part(s) by mass]
	Diethylene glycol	40	40	40	40	40	40
	[part(s) by mass]
	Prepolymer	55	55	55	55	55	55
	[part(s) by mass]
	DETDA	45	45	45	45	45	45
	[part(s) by mass]
	Water	5	5	5	5	5	5
	[part(s) by mass]
	TOYOCAT ET	0.006	0.006	0.006	0.006	0.006	0.006
	[part(s) by mass]
	Foam stabilizer	2	2	2	2	2	2
	[part(s) by mass]
	Resin viscosity	2,784	2,765	2,456	2,354	2,653	2,648
	[mPa · s]
Centrifugal	Number of	1,200	600	1,200	1,200	1,200	1,200
molding	revolutions
	[rpm]
apparatus	Time	30	30	90	180	20.1	9.9
operating	[min]
conditions	Mold set	120	120	120	120	120	120
	temperature [° C.]

	TABLE 1-2
	Polishing	Polishing	Polishing	Polishing	Polishing
	pad 7	pad 8	pad 9	pad 10	pad 11

Formulation	TDI	237	237	237	237	237
	[part(s) by mass]
	PTMG	412	412	412	412	412
	[part(s) by mass]
	Diethylene glycol	40	40	40	40	40
	[part(s) by mass]
	Prepolymer	55	60	50	65	55
	[part(s) by mass]
	DETDA	45	40	50	35	45
	[part(s) by mass]
	Water	10	5	5	5	5
	[part(s) by mass]
	TOYOCAT ET	0.006	0.002	0.006	0.006	0.006
	[part(s) by mass]
	Foam stabilizer	10	2	2	2	1
	[part(s) by mass]
	Resin viscosity	2,752	1,127	5,837	2,547	2,454
	[mPa · s]
Centrifugal	Number of	1,200	1,200	1,200	1,200	1,200
molding	revolutions [rpm]
apparatus	Time	360	150	15	30	30
operating	[min]
conditions	Mold set	120	120	120	120	120
	temperature [° C.]

	TABLE 2-1
	Polishing	Polishing	Polishing	Polishing	Polishing	Polishing
	pad 1	pad 2	pad 3	pad 4	pad 5	pad 6

Molding method	Integrally	Integrally	Integrally	Integrally	Integrally	Integrally
	molded	molded	molded	molded	molded	molded
D50 [μm]	107	151	104	101	115	107
Asker A hardness of resin sheet	92	92	90	93	92	92
measured with indenter having
diameter of 0.79 mm at tip
thereof at 25° C.
Depth of minimum value of	30.3%	68.0%	38.2%	34.5%	75.0%	36.4%
bubble area ratio distribution
curve [%]
Average bubble area ratio in	38.2%	32.0%	33.2%	32.1%	40.9%	45.4%
depth region of 0% or more and
20% or less in bubble area ratio
distribution curve [%]
Average bubble area ratio in	7.5%	6.3%	5.6%	4.9%	9.5%	13.4%
depth region of 20% or more
and 50% or less [%]
Average bubble area ratio in	25.9%	27.7%	16.3%	13.0%	29.9%	33.3%
depth region of 50% or more
and 100% or less [%]

	TABLE 2-2
	Polishing	Polishing	Polishing	Polishing	Polishing	Polishing
	pad 7	pad 8	pad 9	pad 10	pad 11	pad 12

Molding method	Integrally	Integrally	Integrally	Integrally	Integrally	Multi-
	molded	molded	molded	molded	molded	layer
						extrusion
						molding
D50 [μm]	39	102	185	101	205	107
Asker A hardness of resin sheet	99	74	98	51	92	92
measured with indenter having
diameter of 0.79 mm at tip
thereof at 25° C.
Depth of minimum value of	79.0%	8.9%	81.4%	17.5%	34.3%	35.0%
bubble area ratio distribution
curve [%]
Average bubble area ratio in	22.2%	31.5%	36.7%	35.0%	38.2%	36.4%
depth region of 0% or more and
20% or less in bubble area ratio
distribution curve [%]
Average bubble area ratio in	4.3%	7.8%	6.9%	7.5%	7.9%	6.1%
depth region of 20% or more
and 50% or less [%]
Average bubble area ratio in	11.1%	25.5%	27.5%	25.9%	31.1%	34.5%
depth region of 50% or more
and 100% or less [%]

Table 3-1 and Table 3-2 show the result of evaluation of the fracture easiness of each of the polishing pads, and the results of the evaluations of the local flatness, shear drop, and polishing rate of an object to be polished.

	TABLE 3-1
	Example 1	Example 2	Example 3	Example 4	Example 5	Example 6	Example 7

Used pad	Polishing	Polishing	Polishing	Polishing	Polishing	Polishing	Polishing
	pad 1	pad 2	pad 3	pad 4	pad 5	pad 6	pad 7
End portion	1.03	1.15	1.14	1.17	1.18	1.28	1.29
SFQR
SFQR	1.05	1.08	1.19	1.25	1.04	1.08	1.29
Rate	1,621	1,655	1,685	1,678	1,657	1,699	1,653
[nm/min]
Fracture	No fracture	No fracture	No fracture	No fracture	No fracture	No fracture	No fracture
observation
result

	TABLE 3-2
	Comparative	Comparative	Comparative	Comparative	Comparative
	Example 1	Example 2	Example 3	Example 4	Example 5

Used pad	Polishing	Polishing	Polishing	Polishing	Polishing
	pad 8	pad 9	pad 10	pad 11	pad 12
End portion	1.28	1.39	1.38	1.38	1.39
SFQR
SFQR	1.35	1.28	1.09	1.08	1.38
Rate	1,694	1,675	1,684	1,688	1,394
[nm/min]
Fracture	No fracture	No fracture	No fracture	No fracture	Fracture
observation
result

Examples 2 to 7

Polishing pads 2 to 7 were each obtained in exactly the same manner as in Example 1 except that the formulation, and the rotation condition and rotation time of the cylindrical mold were changed as shown in Table 1-1 and Table 1-2. Table 2-1 and Table 2-2 show the physical properties of the resultant polishing pads 2 to 7.

Table 3-1 shows the evaluation results of the resultant polishing pads 2 to 7.

Comparative Examples 1 to 4

Polishing pads 8 to 11 were each obtained in exactly the same manner as in Example 1 except that the formulation, and the rotation condition and rotation time of the cylindrical mold were changed as shown in Table 3-2. Table 2-2 shows the physical properties of the resultant polishing pads 8 to 11.

Table 3-2 shows the evaluation results of the resultant polishing pads 8 to 11.

Comparative Example 5

A T-die having a lip width of 700 mm and a lip gap of 1.5 mm was attached to the tip of a feed block type extruder in which three extruders each having a barrel diameter of 50 mm and a ratio L/D of 32 were connected. A thermoplastic polyurethane (product name: Resamine P-4070 EX) manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd. was dried with hot air at 100° C. for 4 hours, and was introduced into each extruder hopper.

First, the temperature of each of an extruder on a first layer side (hereinafter referred to as “first extruder”), an extruder on a second layer side (hereinafter referred to as “second extruder”), an extruder on a third layer side (hereinafter referred to as “third extruder”), and a die was set to 180° C., and a sheet was extruded at a discharge speed of 27.3 Kg/Hr.

The internal pressure of the first extruder, the internal pressure of the second extruder, and the internal pressure of the third extruder when a steady state was reached were 11.2 MPa, 11.5 MPa, and 11.3 MPa, respectively. Carbon dioxide increased in pressure to 25 MPa with a pump was injected from a substantially central part of each extruder, and at the same time, the temperature of the first extruder was changed to 155° C., the temperature of the second extruder was changed to 160° C., the temperature of the third extruder was changed to 165° C., the die temperature of a first layer portion was changed to 155° C., the die temperature of a second layer portion was changed to 160° C., and the die temperature of a third layer portion was changed to 165° C. In the steady state after the carbon dioxide injection, the internal pressure of the first extruder was 17.8 MPa, the internal pressure of the second extruder was 12.8 MPa, and the internal pressure of the third extruder was 9.7 MPa.

After the temperatures and internal pressures of the extruders and the die had been stabilized, and the discharge state of the sheet had been stabilized, the sheet discharged from the die was passed through a cooling roll controlled to 10° C., and was then taken up by a take-up machine to provide a resin sheet 13.

A double-sided tape having adhesive layers (material: acrylic resin) on both the surfaces of a PET-made substrate, and further having release paper on one surface thereof was bonded to a surface opposite to the surface of the resultant resin sheet 13 where its bubble area ratio was maximum or a surface in the vicinity thereof via the adhesive layer opposite to the release paper, and the laminate was cut into a circular shape having a diameter of 300 mm to provide a polishing pad 12. Table 2-2 shows the physical properties of the resultant polishing pad 12.

Table 3-2 shows the evaluation result of the resultant polishing pad 12.

Each of Examples 1 to 7 and Comparative Examples 1 to 4 was an integrally molded article and satisfied claim 1, and hence the fracture of the pad was suppressed. Comparative Example 5 did not satisfy claim 1 in which the polishing pad was an integrally molded article, and hence the fracture of the pad was observed. In addition, in each of Examples 1 to 7, the bubble diameter, the hardness, and the depth of the minimum value of the bubble area ratio distribution curve satisfied claim 1, and hence the local flatness, shear drop, and polishing rate of the object to be polished were satisfactory. Example 1 was particularly satisfactory. In each of Comparative Examples 1 to 4, the bubble diameter, the hardness, and the depth of the minimum value of the bubble area ratio distribution curve did not satisfy claim 1, and hence the local flatness and shear drop of the object to be polished were not satisfactory.

According to the present disclosure, there can be provided a polishing pad, which is so excellent in durability as to be free from causing fracture or the like even under conditions higher than conventional conditions in terms of the number of revolutions of the polishing pad or an object to be polished, and a polishing pressure between the polishing pad and the object to be polished while achieving flatness and a polishing rate equal to or higher than those of a related-art polishing pad, and a polishing method using the polishing pad.

While the present disclosure has been described with reference to embodiments, it is to be understood that the present disclosure is not limited to the disclosed embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

This application claims the benefit of Japanese Patent Application No. 2024-229430, filed Dec. 25, 2024, which is hereby incorporated by reference herein in its entirety.