Polishing pad

Abstract

To provide a polishing pad that can improve a fault of profiling an edge part such as sagging and rebounding of an end part, without changing a physical property / bubble structure of a polishing layer.SOLUTION: A polishing pad 3 comprises a polishing layer 4 having a polishing surface for polishing an object to be polished and a cushion layer 6 arranged at the opposite side of the polishing surface of the polishing layer 4. The polishing layer has Shore D-hardness of 40 degrees-70 degrees and has hollow microscopic spheres 4A dispersed thereon. The cushion layer 6 has compressive elasticity modulus of 90% or more.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a polishing pad. Specifically, the present invention relates to a polishing pad that can be suitably used for polishing optical materials, semiconductor wafers, semiconductor devices, substrates for hard disks, and the like.

Background Art

[0002] As a polishing method for planarizing the surfaces of optical materials, semiconductor wafers, semiconductor devices, and substrates for hard disks, a chemical mechanical polishing (CMP) method is generally used.

[0003] The CMP method will be described with reference to FIG. 1. As shown in FIG. 1, a polishing apparatus 1 for performing the CMP method includes a polishing pad 3. The polishing pad 3 abuts against a workpiece 8 held on a holding platen 16 and includes a polishing layer 4 that is a layer for performing polishing and a cushion layer 6 that supports the polishing layer 4. The polishing pad 3 is rotationally driven in a state where the workpiece 8 is pressed, and polishes the workpiece 8. At that time, a slurry 9 is supplied between the polishing pad 3 and the workpiece 8. The slurry 9 is a mixture (dispersion liquid) of water and various chemical components and hard fine abrasive grains. While the chemical components and abrasive grains in the slurry 9 flow, the relative movement with the workpiece 8 increases the polishing effect. The slurry 9 is supplied to and discharged from the polishing surface through grooves or holes.

[0004] Incidentally, conventional polishing pads 3 have used foamed polyurethane for the polishing layer 4, but abnormalities in the profile of the workpiece 8, particularly at the edges of the workpiece 8, can occur. As abnormalities in the edge profile, for example, an over-polishing phenomenon called "edge rounding" (8a in Figure 2), in which the outermost part of the workpiece 8 is polished more than the central part, and a polishing failure phenomenon called "rebound" (8b in Figure 2), in which the polishing rate becomes unstable and irregularities occur at the periphery slightly inside the outermost part, as shown in Figure 2. In Figure 4, which shows the polishing rate (RR) on the vertical axis and the distance on the horizontal axis of a straight line passing through the center of the workpiece 8 (0 on the horizontal axis is the center of the workpiece) for a workpiece polished with a conventional polishing pad, it can be seen that abnormalities in the edge profile occur, namely edge rounding, in which the polishing rate at both outermost parts is greater than in other parts, and rebound, in which irregularities occur at the periphery slightly inside the outermost parts. This edge rounding can be a problem in semiconductor polishing (especially in the oxide film polishing process) when the polishing rate of the outermost edge (circumferential portion) of the workpiece is 1.5 times or more than that of other parts of the workpiece.

[0005] To address this over-polishing phenomenon known as edge rounding, Patent Document 1 discloses a polishing pad that prevents edge rounding while suppressing the occurrence of polishing scratches by specifying the structure of air bubbles in the foam, thereby keeping the hardness of the polishing layer within a certain range.

[0006] Patent Document 2 discloses a polishing pad that eliminates the problem of edge sagging by setting the hardness and tear strength of the polishing layer within a predetermined range. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2012-714 [Patent Document 2] Japanese Patent Publication No. 2016-190313 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, the polishing pads described in Patent Documents 1 and 2 above require specific physical properties and bubble structure of the polishing layer, and even if edge sagging is improved, other polishing performance may be inferior.

[0009] This invention has been made in view of the above-mentioned problems, and aims to provide a polishing pad that can improve profile abnormalities in the edge portion, such as edge sagging and rebound, without changing the physical properties or bubble structure of the polishing layer. [Means for solving the problem]

[0010] As a result of diligent research, the inventors have discovered a polishing pad that, by using a material with low rebound in the cushion layer, can improve profile abnormalities in the edge portion, such as edge sagging and rebound. In other words, the present invention encompasses the following: [1] A polishing pad comprising a polishing layer having a polishing surface for polishing an object to be polished, and a cushion layer disposed on the opposite side of the polishing surface of the polishing layer, The aforementioned polishing layer has a Shore D hardness of 40 to 70 degrees and contains dispersed hollow microspheres. The aforementioned cushion layer has a compressive modulus of 90% or more, and is used as an abrasive pad. [2] The polishing pad according to [1], wherein the density of the cushion layer is 0.30 to 0.60. [3] The polishing pad according to [1] or [2], wherein the cushion layer has teardrop-shaped bubbles. [4] The polishing pad according to [1] or [2], wherein the cushion layer has fine bubbles. [5] The polishing pad according to any one of [1] to [4], wherein the polishing layer comprises either a slurry-holding groove or a slurry-discharge groove on the polishing surface. [Effects of the Invention]

[0011] According to the polishing pad of the present invention, by using a material with less repulsion in the cushion layer without changing the physical properties and bubble structure of the polishing layer, profile abnormalities at the edge portions such as end sag and rebound can be suppressed, and stable polishing can be performed.

Brief Description of the Drawings

[0012] [Figure 1] FIG. 1 is a perspective view of the polishing apparatus 1. [Figure 2] FIG. 2 is a side view of the workpiece 8 in a state of end sag. [Figure 3] FIG. 3 is a perspective view (a) and a cross-sectional view (b) of the polishing pad 3 of the present invention. [Figure 4] FIG. 4 shows the profile of the polishing rate of the entire workpiece along a straight line passing through the center of the workpiece 8 polished by the prior art (polishing pad of Comparative Example 1). [Figure 5] FIG. 5 shows the profile of the polishing rate of the edge portion of the workpiece 8 polished by the prior art (polishing pad of Comparative Example 1). [Figure 6] FIG. 6 shows the profile of the polishing rate of the entire workpiece along a straight line passing through the center of the workpiece 8 polished using the polishing pad of Example 1. [Figure 7] FIG. 7 shows the profile of the polishing rate of the edge portion of the workpiece 8 polished using the polishing pad of Example 1.

Modes for Carrying Out the Invention

[0013] Hereinafter, modes for carrying out the invention will be described, but the present invention is not limited to the modes for carrying out the invention.

[0014] <<Polishing Pad>> The structure of the polishing pad 3 will be described with reference to FIG. 3. As shown in FIG. 3, the polishing pad 3 includes a polishing layer 4 and a cushion layer 6. The shape of the polishing pad 3 is preferably a disk shape, but is not particularly limited. Also, the size (diameter) can be appropriately determined according to the size of the polishing apparatus 1 including the polishing pad 3. For example, it can be about 10 cm to 2 m in diameter. Note that in the polishing pad 3 of the present invention, preferably as shown in FIG. 3, the polishing layer 4 is adhered to the cushion layer 6 via an adhesive layer 7. The polishing pad 3 is attached to the polishing surface plate 10 of the polishing apparatus 1 by means of a double-sided tape or the like disposed on the cushion layer 6. The polishing pad 3 is rotationally driven while pressing the workpiece 8 by the polishing apparatus 1, and polishes the workpiece 8.

[0015] <Polishing layer> (Configuration) The polishing pad 3 includes a polishing layer 4 which is a layer for polishing the workpiece 8. As the material constituting the polishing layer 4, polyurethane resin, polyurea resin, and polyurethane-polyurea resin can be preferably used, and more preferably polyurethane resin can be used. The size (diameter) of the polishing layer 4 is the same as that of the polishing pad 3 and can be about 直径10cm~2m程度 (10 cm to 2 m in diameter), and the thickness of the polishing layer 4 can usually be about 1 to 5 mm. The polishing layer 4 is rotated together with the polishing surface plate 10 of the polishing apparatus 1, and while flowing the slurry 9 thereon, the chemical components and abrasive grains contained in the slurry 9 are relatively moved together with the workpiece 8 to polish the workpiece 8. In the polishing layer 4, hollow microspheres 4A (foamed) are dispersed. When the polishing layer 4 is worn due to the dispersion of the hollow microspheres 4A, the hollow microspheres 4A are exposed on the polishing surface and minute voids are formed on the polishing surface. The polishing of the workpiece 8 can be further advanced by the retention of the slurry by these minute voids.

[0016] (Grooving) It should be noted that there seems to be a typo in the original text where "直径10cm~2m程度" was not properly translated in the relevant part. I've left it as is in the translation for you to check the original intention. You may need to correct it to "about 10 cm to 2 m in diameter" for a more accurate translation.It is preferable to provide grooves on the surface of the polishing layer 4 on the side facing the workpiece 8 of the present invention. The grooves are not particularly limited and may be either slurry discharge grooves communicating with the periphery of the polishing layer 4 or slurry retention grooves not communicating with the periphery of the polishing layer 4, or both slurry discharge grooves and slurry retention grooves may be present. Examples of slurry discharge grooves include grid grooves and radial grooves, and examples of slurry retention grooves include concentric grooves and perforations (through holes), and these can also be combined. In low-pressure grinding, the grinding platen is rotated at high speed to reduce the pressing force on the workpiece 8 and to ensure a high grinding rate. As a result, there is a possibility of hydroplaning, where slurry 9 exists in layers between the grinding surface and the processed surface, hindering the grinding process. This phenomenon can be suppressed by machining grooves on the grinding surface. It is also possible to promote the discharge of grinding debris and the movement of the grinding fluid. The cross-sectional shape can be U-shaped, V-shaped, or semi-circular. There are no particular restrictions on the pitch, width, or depth of the grooves. Furthermore, to improve the flatness of the grinding pad 3, surface grinding treatments such as buffing may be applied to the grinding surface side or the side opposite the grinding surface of the grinding pad 3.

[0017] In the polishing layer 4 of the present invention, although not essential, it is preferable to have both slurry discharge grooves and slurry holding grooves. The ratio of groove widths (discharge / holding) between the slurry holding groove and the slurry discharge groove is preferably 1.5 to 7.5. Furthermore, the ratio of groove pitches (discharge / holding) is preferably 4.5 to 15. Here, groove width means the width of the groove. Groove pitch means the distance from the end of one groove to the same side end of the adjacent groove, and is the groove width plus the land width. Furthermore, when both slurry discharge grooves and slurry retention grooves are present, the ratio of the volume of the slurry retention groove to the volume of the slurry discharge groove (slurry discharge groove volume / slurry retention groove volume) can be set to 0.5 to 1.0. The groove volume is calculated by multiplying the area of ​​the groove's cross-section by the length of the groove, and the volume of the slurry retention grooves in the polishing layer 3 is the sum of the volumes of the slurry retention grooves provided in the polishing layer 3. The same considerations apply to the slurry discharge groove.

[0018] (Shore D hardness) The Shore D hardness of the polishing layer 4 of the present invention is 40 to 70. While a Shore D hardness of 40 to 70 for the polishing layer 4 is a conventional material, combining a Shore D hardness of 40 to 70 with setting the compressive modulus of the cushion layer 6 (described later) to a specific value can improve profile abnormalities in the edge portion of the workpiece 8, such as edge rounding and rebound. If the Shore D hardness is less than 40 degrees, it becomes difficult to flatten fine irregularities with low-pressure polishing. If it exceeds 60 degrees, polishing particles may be strongly rubbed against the workpiece 8, potentially causing scratches on the processed surface of the workpiece 8. The lower limit of the Shore D hardness of the polishing layer 4 is preferably 40 or higher, 42 or higher, and 45 or higher, in that order, while the upper limit is preferably 70 or lower, 65 or lower, and 60 or lower, in that order.

[0019] The polishing layer 4 is formed by pouring a mixture of an isocyanate group-containing compound mixed with hollow microspheres 4A (described later) and a hardening agent (chain extender), curing the resulting foam, and then slicing the foam. In other words, the polishing layer 4 is dry-molded.

[0020] In the polishing pad of the present invention, hollow microspheres 4A are used to encapsulate air bubbles within the polyurethane resin molded body. Hollow microspheres refer to microspheres having air gaps. The shape of the hollow microspheres 4A can be spherical, elliptical, or close to these shapes. Examples include pre-expanded types and unexpanded heat-expandable microspheres that have been heated and expanded.

[0021] The physical properties of the polished layer 4, such as its Shore D hardness, can be adjusted to a desired range by controlling the composition of the polished layer 4, the number and size of the hollow microspheres 4A, etc.

[0022] <Cushioning layer> (composition) The polishing pad 3 of the present invention has a cushion layer 6. It is desirable that the cushion layer 6 makes the contact of the polishing layer 4 with the workpiece 8 more uniform. The material of the cushion layer 6 may be any of the following: an impregnated nonwoven fabric impregnated with resin, a flexible material such as synthetic resin or rubber, or a foam having a cellular structure. Examples include resins such as polyurethane, polyethylene, polybutadiene, and silicone, and rubbers such as natural rubber, nitrile rubber, and polyurethane rubber. From the viewpoint of adjusting density and compressive modulus, a flexible synthetic resin is preferred, and it is preferable to use polyurethane as the material.

[0023] Furthermore, more preferably, a cushion layer 6 made of polyurethane resin is used, which is formed into a sheet (wet film formation) by desolvation with an aqueous coagulation solution (a coagulation solution mainly composed of water). The cushion layer 6 has a foamed structure in which teardrop-shaped bubbles 6A are formed inside. A cushion layer 6 made of polyurethane resin having sponge-like fine bubbles is also preferably used.

[0024] (Compression modulus) The cushion layer 6 in the polishing pad 3 of the present invention has a compressive modulus of 90% or more. The compressive modulus of the cushion layer 6 is 90% or more, and the Shore D hardness of the polishing layer 4 is 40-70, which suppresses profile abnormalities in the edge portion, such as edge rounding and rebound. Furthermore, if the compressive modulus is 90% or more, a slight increase in RR, i.e., rebound, which is observed not at the outermost edge of the workpiece 8 but slightly inward, is also suppressed. Note that rebound refers to the slight increase in RR observed in the area just before the very edge (143-145mm) in Figure 5 compared to both sides; this is called rebound.

[0025] (density) The cushion layer 6 in the polishing pad 3 of the present invention preferably has a density of 0.30 to 0.60. With a density in this range, cushioning can be ensured, and the conventional polishing rate (polishing speed, RR) can be achieved. The lower limit of density is preferably 0.30 or higher, 0.32 or higher, and 0.33 or higher, in that order, and the upper limit of density is preferably 0.60 or lower, 0.58 or lower, and 0.55 or lower, in that order. Note that the density here is not the density of the material itself, but the density of the cushion layer 6 including air bubbles and the base material.

[0026] The compressive modulus and density of the cushion layer 6 can be adjusted by the type of resin material, the number and size of air bubbles, thickness, etc.

[0027] (bubbles) The cushion layer 6 of the present invention preferably has interconnected bubbles, such as teardrop-shaped bubbles or microbubbles. Figure 3 shows a cushion layer 6 having teardrop-shaped bubbles 6A. The teardrop-shaped bubbles 6A may be located inside the cushion layer 6, as shown in Figure 6, or they may be extended to the upper and / or lower surfaces of the cushion layer 6 by cutting or other means, resulting in a state where there are holes on the upper and lower surfaces, or holes that penetrate the upper and lower surfaces. Having teardrop-shaped bubbles 6A prevents the cushion layer 6 from becoming too hard. The cushion layer 6 can be manufactured by a wet film formation method to obtain a cushion layer 6 having teardrop-shaped bubbles 6A.

[0028] <Adhesive layer> The adhesive layer 7 is a layer for bonding the cushion layer 6 and the polishing layer 4, and is usually composed of double-sided tape or adhesive. The double-sided tape or adhesive can be one known in the art (e.g., adhesive sheets). The polishing pad 3 and the cushion layer 6 are bonded together by an adhesive layer 7. The adhesive layer 7 can be formed from at least one adhesive selected from, for example, acrylic, epoxy, or urethane. For example, an acrylic adhesive can be used, and its thickness can be set to 0.1 mm.

[0029] <<Manufacturing method for polishing pads>> The method for manufacturing the polishing pad 3 of the present invention will be described below.

[0030] <Materials for the polished layer> The material for the polishing layer is not particularly limited, but preferably, a material that can be easily adjusted to a Shore D hardness of 40 to 70 is selected. The main component is preferably polyurethane resin, polyurea resin, or polyurethane-polyurea resin, with polyurethane resin being more preferred. Specific examples of the main component material include materials obtained by reacting a urethane-bonded polyisocyanate compound with a curing agent.

[0031] The manufacturing method for the polishing layer 4 will be explained below using an example that utilizes a urethane bond-containing isocyanate compound, a polyol compound, and a curing agent.

[0032] A method for producing the polished layer 4 using a urethane bond-containing polyisocyanate compound and a curing agent includes, for example, a material preparation step of preparing at least a urethane bond-containing polyisocyanate compound, an additive, and a curing agent; a mixing step of mixing at least the urethane bond-containing polyisocyanate compound, the additive, and the curing agent to obtain a mixed liquid for molding a molded body; and a curing step of forming the polished layer from the mixed liquid for molding a molded body.

[0033] The following will explain the process in three parts: material preparation, mixing, and molding.

[0034] <Material preparation process> For the production of the polishing layer 4 of the present invention, a urethane bond-containing polyisocyanate compound and a curing agent are prepared as raw materials for a polyurethane resin molded body (cured resin). Here, the urethane bond-containing polyisocyanate is a urethane prepolymer for forming the polyurethane resin molded body. When the polishing layer 4 is to be made into a polyurea resin molded body or a polyurethane polyurea resin molded body, the appropriate prepolymer is used.

[0035] The following explains each component.

[0036] (Polyisocyanate compound containing urethane bonds) The urethane bond-containing polyisocyanate compound (urethane prepolymer) is a compound obtained by reacting the following polyisocyanate compound and polyol compound under commonly used conditions, and contains a urethane bond and an isocyanate group within its molecule. Furthermore, other components may be included in the urethane bond-containing polyisocyanate compound, as long as they do not impair the effects of the present invention.

[0037] As the urethane bond-containing polyisocyanate compound, commercially available compounds may be used, or compounds synthesized by reacting a polyisocyanate compound with a polyol compound may be used. There are no particular restrictions on the reaction, and the addition polymerization reaction may be carried out using methods and conditions known in the production of polyurethane resins. For example, it can be produced by adding a polyisocyanate compound heated to 50°C to a polyol compound heated to 40°C while stirring in a nitrogen atmosphere, raising the temperature to 80°C after 30 minutes, and then reacting at 80°C for 60 minutes.

[0038] (Polyisocyanate compounds) In this specification, a polyisocyanate compound means a compound having two or more isocyanate groups in its molecule. Polyisocyanate compounds are not particularly limited as long as they have two or more isocyanate groups in their molecule. For example, diisocyanate compounds having two isocyanate groups in their molecule include m-phenylenediisocyanate, p-phenylenediisocyanate, 2,6-tolylenediisocyanate (2,6-TDI), 2,4-tolylenediisocyanate (2,4-TDI), naphthalene-1,4-diisocyanate, diphenylmethane-4,4'-diisocyanate (MDI), 4,4'-methylene-bis(cyclohexyl isocyanate) (hydrogenated MDI), 3,3'-dimethoxy-4,4'-biphenyldiisocyanate, and 3,3'-dimeth Examples of polyisocyanate compounds include diphenylmethane-4,4'-diisocyanate, xylylene-1,4-diisocyanate, 4,4'-diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, cyclohexylene-1,2-diisocyanate, cyclohexylene-1,4-diisocyanate, p-phenylene diisothiocyanate, xylylene-1,4-diisothiocyanate, and ethyridine diisothiocyanate. These polyisocyanate compounds may be used individually or in combination of multiple polyisocyanate compounds.

[0039] The polyisocyanate compound preferably contains 2,4-TDI and / or 2,6-TDI, more preferably contains 2,4-TDI and 2,6-TDI, and even more preferably consists only of 2,4-TDI and 2,6-TDI. The mass ratio of 2,4-TDI to 2,6-TDI is preferably 100:0 to 50:50, more preferably 90:10 to 60:40, even more preferably 90:10 to 70:30, and even more preferably 80:20.

[0040] (Polyol compounds as raw materials for prepolymers) In this specification, a polyol compound means a compound having two or more hydroxyl groups (OH) in its molecule. Examples of polyol compounds used in the synthesis of urethane bond-containing polyisocyanate compounds as prepolymers include diol compounds such as ethylene glycol, diethylene glycol (DEG), and butylene glycol, triol compounds, and polyether polyol compounds such as poly(oxytetramethylene) glycol (or polytetramethylene ether glycol) (PTMG). Among these, PTMG is preferred. The number-average molecular weight (Mn) of PTMG is preferably 500 to 2000, more preferably 600 to 1300, and even more preferably 650 to 1000. The number-average molecular weight can be measured by gel permeation chromatography (GPC). When measuring the number-average molecular weight of a polyol compound from a polyurethane resin, it is also possible to estimate it by GPC after decomposing each component by conventional methods such as amine decomposition. The above polyol compounds may be used individually or in combination of multiple polyol compounds.

[0041] (Additives) As described above, additives such as oxidizing agents can be added to the material of the polishing layer 4 as needed.

[0042] (Hardening agent) In the method for producing the polished layer 4 of the present invention, a curing agent (also called a chain extender) is mixed with a urethane bond-containing polyisocyanate compound or the like in the mixing step. By adding the curing agent, in the subsequent molded product molding step, the main chain ends of the urethane bond-containing polyisocyanate compound bond with the curing agent to form polymer chains and harden. Examples of curing agents include ethylenediamine, propylenediamine, hexamethylenediamine, isophoronediamine, dicyclohexylmethane-4,4'-diamine, 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA), 4-methyl-2,6-bis(methylthio)-1,3-benzenediamine, 2-methyl-4,6-bis(methylthio)-1,3-benzenediamine, 2,2-bis(3-amino-4-hydroxyphenyl)propane, and 2,2-bis[3-(isopropylamino)-4- Polyhydric amine compounds such as hydroxyphenyl]propane, 2,2-bis[3-(1-methylpropylamino)-4-hydroxyphenyl]propane, 2,2-bis[3-(1-methylpentylamino)-4-hydroxyphenyl]propane, 2,2-bis(3,5-diamino-4-hydroxyphenyl)propane, 2,6-diamino-4-methylphenol, trimethylethylenebis-4-aminobenzoate, and polytetramethylene oxide-di-p-aminobenzoate; ethylene glycol, pro Pyrene glycol, diethylene glycol, trimethylene glycol, tetraethylene glycol, triethylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,2-butanediol, 3-methyl-1,2-butanediol, 1,2-pentanediol, 1,4-pentanediol, 2,4-pentanediol, 2,3-dimethyltrimethylene glycol, tetramethylene glycol, 3-methyl-4,3-pentanediol, 3- Examples of polyhydric alcohol compounds include methyl-4,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,6-hexanediol, 1,5-hexanediol, 1,4-hexanediol, 2,5-hexanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, glycerin, trimethylolpropane, trimethylolethane, trimethylolmethane, poly(oxytetramethylene) glycol, polyethylene glycol, and polypropylene glycol.Furthermore, the polyhydric amine compound may have a hydroxyl group, and examples of such amine compounds include 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, and di-2-hydroxypropylethylenediamine. Diamine compounds are preferred as the polyhydric amine compound, and it is even more preferable to use, for example, 3,3'-dichloro-4,4'-diaminodiphenylmethane (methylenebis-o-chloroaniline) (hereinafter abbreviated as MOCA).

[0043] The polishing layer 4 can be formed into hollow microspheres 4A having an outer shell and a hollow interior by using a material. The material for the hollow microspheres 4A may be a commercially available product or one obtained by synthesis using a conventional method. The material for the outer shell of the hollow microspheres 4A is not particularly limited, but examples include polyvinyl alcohol, polyvinylpyrrolidone, poly(meth)acrylic acid, polyacrylamide, polyethylene glycol, polyhydroxyether acrylate, maleic acid copolymer, polyethylene oxide, polyurethane, poly(meth)acrylonitrile, polyvinylidene chloride, polyvinyl chloride, and organosilicon resins, as well as copolymers obtained by combining two or more monomers that constitute these resins. In addition, commercially available hollow microspheres include, but are not limited to, the Expancel series (product name of AkzoNobel) and Matsumoto Microspheres (product name of Matsumoto Oil & Fat Co., Ltd.).

[0044] The shape of the hollow microspheres 4A is not particularly limited and may be spherical or substantially spherical, for example. The average particle size of the hollow microspheres 4A is not particularly limited, but is preferably 5 to 200 μm, more preferably 5 to 80 μm, even more preferably 5 to 50 μm, and particularly preferably 5 to 35 μm. The average particle size can be measured using a laser diffraction particle size distribution analyzer (for example, MasterSizer-2000 manufactured by Spectris Co., Ltd.).

[0045] The material for the hollow microspheres 4A is added to 100 parts by mass of urethane prepolymer, preferably 0.1 to 10 parts by mass, more preferably 1 to 5 parts by mass, and even more preferably 1 to 3 parts by mass.

[0046] In addition to the components mentioned above, conventionally used foaming agents may be used in combination with the hollow microspheres 4A, to the extent that they do not impair the effects of the present invention, and a gas that is unreactive to each of the above components may be blown in during the mixing step described below. Examples of foaming agents include water and foaming agents mainly composed of hydrocarbons having 5 or 6 carbon atoms. Examples of such hydrocarbons include chain hydrocarbons such as n-pentane and n-hexane, and alicyclic hydrocarbons such as cyclopentane and cyclohexane.

[0047] <Mixing process> In the mixing step, the urethane bond-containing polyisocyanate compound (urethane prepolymer), additives, and curing agent obtained in the preparation step are supplied to a mixer and stirred and mixed. The mixing step is carried out under conditions where the mixture is heated to a temperature that ensures the fluidity of each component.

[0048] <Forming process> In the molded body molding process, the molded body molding mixture prepared in the mixing step is poured into a rod-shaped mold preheated to 30-100°C and allowed to cure for the first time. Then, it is heated at approximately 100-150°C for 10 minutes to 5 hours to cure for the second time, thereby molding a cured polyurethane resin (polyurethane resin molded body). At this time, the urethane prepolymer and curing agent react to form the polyurethane resin, causing the mixture to harden. If the viscosity of the urethane prepolymer is too high, its fluidity deteriorates, making it difficult to mix it uniformly during mixing. Lowering the viscosity by increasing the temperature shortens the pot life, which can lead to uneven mixing and variations in the size of the hollow microspheres 4A formed in the resulting foam. Conversely, if the viscosity is too low, air bubbles will migrate in the mixture, making it difficult to form hollow microspheres 4A that are dispersed almost uniformly in the resulting foam. For this reason, it is preferable to set the viscosity of the prepolymer in the range of 500 to 4000 mPa·s at a temperature of 50 to 80°C. This viscosity can be set, for example, by changing the molecular weight (degree of polymerization) of the prepolymer. The prepolymer is heated to about 50 to 80°C to make it fluid.

[0049] In the molding process, the mixed liquid is poured as needed and reacted within the mold to form a foam. At this time, the prepolymer cross-links and hardens due to the reaction between the prepolymer and the curing agent.

[0050] After obtaining the molded body, it is sliced ​​into sheets to form multiple polishing layers 4. A general-purpose slicing machine can be used for slicing. During slicing, the lower part of the polishing layer 4 is held, and it is sliced ​​sequentially from the top to a predetermined thickness. The slicing thickness is set, for example, in the range of 1.3 to 2.5 mm. In the case of a foam molded with a thickness of 50 mm, for example, about 10 mm of the upper and lower parts of the foam are not used due to scratches, etc., and 10 to 25 polishing layers 4 are formed from the central part, about 30 mm. In the hardening molding step, a foam is obtained in which hollow microspheres 4A are formed almost uniformly inside.

[0051] Grooves are formed on the polished surface of the obtained polished layer 4 as needed. By cutting or other machining processes using the required cutter on the polished surface, grooves with any pitch, width, and depth can be formed. Examples of slurry-holding grooves include circular grooves formed concentrically, and examples of slurry-discharge grooves include straight grooves formed in a grid pattern or straight grooves formed radially from the center of the polished layer.

[0052] The polished layer 4 obtained in this manner is then subjected to double-sided tape being attached to the side of the polished layer 4 opposite to the polished surface. There are no particular restrictions on the double-sided tape, and any double-sided tape known in the art can be arbitrarily selected and used.

[0053] <Method for manufacturing the cushion layer 6> In the process of forming the cushion layer 6, the cushion layer 6 is formed by wet deposition. Specifically, it is formed through the following steps: a preparation step in which a resin solution is prepared in which polyurethane resin is dissolved substantially uniformly in an organic solvent; a solidification and regeneration step in which the resin solution prepared in the preparation step is spread into a sheet and the polyurethane body is solidified and regenerated by desolvating the organic solvent from the resin solution in an aqueous solidification solution; and a washing and drying step in which the polyurethane body solidified and regenerated in the solidification and regeneration step is washed and dried to form the cushion layer 6. The steps will be explained below in order.

[0054] (preparation process) In the preparation step, a resin solution is prepared by dissolving the polyurethane resin and additives in an organic solvent. The resin solution is prepared by dissolving the polyurethane resin and additives almost uniformly in a water-miscible organic solvent capable of dissolving the polyurethane resin, removing aggregates and other impurities by filtration, and then degassing under vacuum. As the organic solvent, N,N-dimethylformamide (hereinafter abbreviated as DMF), dimethylacetamide (hereinafter abbreviated as DMAc), etc. can be used. For example, DMF is used as the organic solvent. The polyurethane resin can be selected from polyester-based, polyether-based, polycarbonate-based resins, etc.

[0055] As additives, pigments such as carbon black, hydrophilic surfactants to promote foaming, and hydrophobic surfactants to stabilize the solidification and regeneration of the polyurethane resin can be used. By changing the type and amount of additives, the size and quantity (number) of teardrop-shaped bubbles 6A formed inside the cushion layer 6 can be controlled. The compressive modulus and density of the cushion layer 6 can be adjusted by selecting the polyurethane resin and organic solvent, the mixing ratio of the resin and organic solvent, the size and quantity of teardrop-shaped bubbles 6A, and the thickness of the cushion layer 6. For example, for 100 parts of resin solution, the polyurethane resin can be set to 45-62 parts and the DMF to 8-30 parts.

[0056] (Coagulation regeneration process) In the solidification and regeneration process, the resin solution prepared in the preparation process is continuously applied to the film-forming substrate (spread into a sheet), and the polyurethane resin is solidified and regenerated into a sheet by immersion in an aqueous solidification solution. The resin solution prepared in the preparation process is applied almost uniformly to the strip-shaped film-forming substrate at room temperature using a coating machine such as a knife coater. At this time, the coating thickness (amount applied) of the resin solution is adjusted by adjusting the gap (clearance) between the coating machine and the film-forming substrate. In this example, the amount applied is adjusted so that the thickness of the cushion layer 6 is in the range of 0.5 to 2.0 mm. Flexible films, nonwoven fabrics, woven fabrics, etc. can be used as the film-forming substrate. When using nonwoven fabrics or woven fabrics, pretreatment (sealing) is performed by immersion in water or a DMF aqueous solution (a mixture of DMF and water) to suppress penetration into the film-forming substrate when the resin solution is applied. When using a flexible film such as PET as the film-forming substrate, pretreatment is unnecessary because it does not allow liquid to penetrate.

[0057] The film-forming substrate coated with the resin solution is immersed in an aqueous solidification solution mainly composed of water, which is a poor solvent for polyurethane resin. In the aqueous solidification solution, first, micropores constituting a skin layer are formed on the surface of the coated resin solution over a thickness of several μm. Subsequently, as the substitution of DMF in the resin solution with the aqueous solidification solution progresses, the polyurethane body is solidified and regenerated in a sheet-like form on one side of the film-forming substrate. As DMF is desolvated from the resin solution and substituted for DMF with the aqueous solidification solution, numerous teardrop-shaped bubbles 6A are formed in the polyurethane body, forming a three-dimensional network of teardrop-shaped bubbles 6A. At this time, because the PET film of the film-forming substrate does not allow water to penetrate, desolvation occurs on the surface side (skin layer side) of the resin solution, and teardrop-shaped bubbles 6A with a larger pore size are formed on the film-forming substrate side than on the surface side. In other words, numerous foams 6A with a rounded, approximately triangular cross-section are formed almost uniformly dispersed inside the polyurethane body along the thickness direction of the polyurethane body.

[0058] (Washing and drying process) In the washing and drying process, the strip-shaped (long) polyurethane material that has been solidified and regenerated in the solidification and regeneration process is washed and then dried to form the cushion layer 6. That is, it is washed in a washing solution such as water and any remaining DMF in the polyurethane material is removed. After washing, the polyurethane material is dried in a cylinder dryer. The cylinder dryer is equipped with a cylinder that has a heat source inside. The polyurethane material dries as it passes along the circumferential surface of the cylinder, and the cushion layer 6 is formed.

[0059] <Joining process> In the joining process, the formed polishing layer 4 and cushion layer 6 are bonded together with an adhesive layer 7. For example, an acrylic adhesive is used for the adhesive layer 7, and the adhesive layer 7 is formed to a thickness of 0.1 mm. That is, the acrylic adhesive is applied to the surface of the polishing layer 4 opposite to the polishing surface to a roughly uniform thickness. The surface of the polishing layer 4 opposite to the polishing surface P and the surface of the cushion layer 6 (the surface on which the skin layer is formed) are pressed together via the applied adhesive, and the polishing layer 4 and cushion layer 6 are bonded together with the adhesive layer 7. After cutting into a desired shape such as a circle, an inspection is performed to confirm that there is no adhesion of dirt or foreign matter, and the polishing pad 3 is completed. [Examples]

[0060] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0061] In each example and comparative example, unless otherwise specified, "parts" means "parts by mass."

[0062] Furthermore, the NCO equivalent is a numerical value that indicates the molecular weight of the prepolymer (PP) per NCO group, calculated using the formula: "(Mass (parts) of the polyisocyanate compound + Mass (parts) of the polyol compound) / [(Number of functional groups per molecule of polyisocyanate compound × Mass (parts) of the polyisocyanate compound / Molecular weight of the polyisocyanate compound) - (Number of functional groups per molecule of polyol compound × Mass (parts) of the polyol compound / Molecular weight of the polyol compound)]".

[0063] (Regarding polished layer A) 100 parts of an isocyanate-terminated urethane prepolymer with an NCO equivalent of 460, obtained by reacting 2,4-tolylene diisocyanate (TDI), poly(oxytetramethylene) glycol (PTMG), and diethylene glycol (DEG), were mixed with 2.6 parts of an unexpanded hollow body whose shell is made of acrylonitrile-vinylidene chloride copolymer and which contains isobutane gas inside the shell, to obtain a mixture. The obtained mixture was placed in the first liquid tank and kept warm. Next, separately from the first liquid, 25.5 parts of MOCA and 8.5 parts of polypropylene glycol (PPG) were added as curing agents and mixed, and kept warm in the second liquid tank. The liquids from the first and second liquid tanks were injected into a mixer equipped with two inlets, so that the R value, which represents the equivalent ratio of amino groups and hydroxyl groups present in the curing agent to the terminal isocyanate groups in the prepolymer, was 0.90. The two injected liquids were mixed and stirred while being poured into a preheated mold of a molding machine. After the mold was clamped, it was heated for 30 minutes to allow primary curing. After demolding the primary cured molded product, it was secondary cured in an oven at 110°C for 4 hours to obtain a urethane molded product. The obtained urethane molded product was allowed to cool to 25°C, then heated again in an oven at 120°C for 5 hours, and then sliced ​​to a thickness of 1.3 mm to obtain polished layer A.

[0064] (Regarding cushion layers (I) through (VII)) Polyester MDI (diphenylmethane diisocyanate) polyurethane resin was used as the polyurethane resin for the preparation of the cushion layer. A polyurethane resin solution was prepared by adding 25 parts of DMF (a solvent), 40 parts of a DMF dispersion containing 20% ​​carbon black as a pigment, and 2 parts of a hydrophobic surfactant (a film-forming stabilizer) to 100 parts of a 30% polyurethane resin solution and mixing. The obtained resin solution was applied to a PET substrate (0.188 mm thick) to a thickness of 0.7 mm, and the organic solvent was removed from the resin solution in an aqueous coagulation solution to prepare a cushion layer (I) including the PET substrate. Cushion layer (II) was fabricated in the same manner as cushion layer (I), except that the 100% modulus of the polyurethane resin was adjusted to achieve high density. A commercially available polyurethane sheet with microbubbles (PORON H-32 manufactured by Inoac Co., Ltd.) was used as the cushion layer (III). A commercially available polyurethane sheet with microbubbles (PORON HH-48C, manufactured by Inoac Co., Ltd.) was used as the cushion layer (IV). Nonwoven fabric made of polyester fibers (density: 0.216 g / cm³) 3 The nonwoven fabric was immersed in a urethane resin solution (DIC Corporation, product name "C1367"). After immersion, the resin solution was squeezed off using a mangle roller that could apply pressure between a pair of rollers, thereby impregnating the nonwoven fabric with the resin solution almost uniformly. Next, the impregnated resin was solidified and regenerated by immersion in a solidification solution consisting of water at room temperature to obtain a resin-impregnated nonwoven fabric. After that, the resin-impregnated nonwoven fabric was removed from the solidification solution and further immersed in a washing solution consisting of water to remove N,N-dimethylformamide (DMF) from the resin, and then dried. After drying, the surface skin layer was removed by buffing to create a cushion layer (V). The resin adhesion rate of the cushion layer (V) was 55%, and its thickness was 0.976 mm. Cushion layer (VI) was prepared using the same method as cushion layer (V), except that the thickness of the cushion layer was set to 1.301 mm. A commercially available non-foaming rubber sheet (Kuraray's "Kureha Elastomer NB560B") was used as the cushioning layer (VII).

[0065] (Evaluation of physical properties) The physical properties of the polished layer and each cushion layer were measured. Shore D hardness was determined according to Japanese Industrial Standards (JIS K 6253) by measuring the indentation depth of an indenter pressed against the surface of the test specimen via a spring. Compressive modulus was determined according to Japanese Industrial Standards (JIS L 1021) using a Shopper-type thickness gauge (pressure surface: 1 cm diameter circle). Specifically, the thickness t0 was measured after applying an initial load for 30 seconds, and then the thickness t1 was measured after leaving it for 5 minutes under the final pressure. After removing all loads and leaving it for 5 minutes, the thickness t0' was measured again after applying the initial load for 30 seconds. The compressive modulus was calculated using the formula: Compressive modulus (%) = (t0'-t1) / (t0-t1) × 100. In this case, the initial load was 100 g / cm².2 The final pressure was 1120 g / cm². 2 That was the case.

[0066] The physical properties of the polishing layer A and cushion layers (I) to (VII) used are described in Tables 1 and 2.

[0067] [Table 1]

[0068] [Table 2]

[0069] (Examples and Comparative Examples) Polishing layer A and cushion layers (I) to (VII) were joined together with 0.1 mm thick double-sided tape (a PET substrate with adhesive layers made of acrylic resin on both sides), and the double-sided tape was attached to the opposite side of the cushion layer and adhesive layer to manufacture the polishing pads of the examples and comparative examples. Examples 1 to 5 were polishing pads using cushion layers (I) to (V) as the cushion layer, respectively, while comparative examples 1 and 2 were polishing pads using cushion layers (VI) and (VII) as the cushion layer, respectively.

[0070] (Polishing performance evaluation) Polishing was performed on the polishing pads of the examples and comparative examples under the following polishing conditions. During polishing, the polishing rate (RR) was measured at 121 points in diameter. The polishing rate profile of the entire workpiece for Comparative Example 1 is shown in Figure 4, the polishing rate profile of the edge portion of the workpiece for Comparative Example 1 is shown in Figure 5, the polishing rate profile of the entire workpiece for Example 1 is shown in Figure 6, and the polishing rate profile of the edge portion of the workpiece for Example 1 is shown in Figure 7. Measurements were taken at 2.5 mm intervals inside a radius of 140 mm, and at 1 mm intervals outside the radius.

[0071] (polishing conditions) Polishing machine used: F-REX300 (manufactured by Ebara Corporation) Abrasive temperature: 20℃ Polishing plate rotation speed: 70 rpm Polishing head rotation speed: 71 rpm Polishing pressure: 3.5 psi Polishing slurry: Manufactured by Cabot Microelectronics Corporation, product name: SS25 Polishing slurry flow rate: 200 ml / min Polishing time: 60 seconds Workpiece to be polished: Silicon wafer with TEOS (Tetra Ethyl Ortho Silicate) coating

[0072] Table 3 shows the polishing results for each polishing pad in the examples and comparative examples. The "final edge rate" in the polishing results was calculated by dividing the polishing rate at the outermost edge of the workpiece (149 mm from the center) by the average polishing rate in the area from 100 to 140 mm from the center. The presence or absence of rebound was checked by examining whether there were any irregularities in the polishing rate just before the outermost edge (the area outside 140 mm from the center).

[0073] [Table 3]

[0074] As shown in Figures 4-5 and Table 3, in the polishing pad of Comparative Example 1, which had low density and compressive modulus, the rate at the outermost edge was large at 1.68, indicating edge rounding, and a rebound phenomenon was observed around 144 mm from the center of the workpiece. Furthermore, the density was 1.236 g / cm³. 3 In comparative example 2, the overall polishing rate of the workpiece was insufficient. On the other hand, as shown in Figures 6-7 and Table 3, the density is 0.474 g / cm³. 3In Example 1, the polishing pad using a cushion layer (I) with teardrop-shaped bubbles having a compressive modulus of 94.8% kept the polishing rate at the very edge below 1.5 (1.39), and no rebound was observed just before the very edge. Similar results were obtained in Example 2, the polishing pad with a different density of the cushion layer. Furthermore, in Examples 3 to 5, which had different bubble structures, by keeping the density and compressive modulus within a predetermined range, it was possible to suppress the increase in polishing rate at the very edge (edge ​​burring) and rebound just before the very edge, resulting in a good edge profile. [Industrial applicability]

[0075] This invention provides a polishing pad that enables improvement of profile abnormalities in edge portions, such as edge rounding and rebound, and therefore contributes to the manufacture and sale of polishing pads, thus having industrial applicability.

[0076] 1 Polishing equipment 3. Polishing pads 4 Polishing layer 4A Hollow microspheres 6. Cushioning layer 6A Teardrop-shaped air bubble 7 Adhesive layer 8 Object to be polished 8a End sagging 8b Rebound 9. Slurry 10. Polishing plate 11 Foundation 16. Holding plate

Claims

1. A polishing pad comprising a polishing layer having a polishing surface for polishing an object to be polished, and a cushion layer positioned on the opposite side of the polishing surface of the polishing layer and bonded to the polishing layer via an adhesive layer, The aforementioned polishing layer has a Shore D hardness of 40 to 70 degrees and contains dispersed hollow microspheres. The aforementioned cushion layer has a compressive modulus of 90% or more, and is used as an abrasive pad.

2. The polishing pad according to claim 1, wherein the density of the cushion layer is 0.30 to 0.60 g / cm³.

3. The polishing pad according to claim 1 or 2, wherein the cushion layer has teardrop-shaped bubbles.

4. The polishing pad according to claim 1 or 2, wherein the cushion layer has fine bubbles.

5. The polishing pad according to any one of claims 1 to 4, wherein the polishing layer is provided with either a slurry-holding groove or a slurry-discharge groove on the polishing surface.

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