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 comprises a polishing layer having a polishing surface for polishing an object to be polished and a cushion layer arranged at the opposite side of the polishing surface of the polishing layer. The cushion layer has a Poisson ratio of 0-0.15 and has Shore A-hardness of 10-80.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Chemical mechanical polishing (CMP) is commonly used as a polishing method for planarizing the surfaces of optical materials, semiconductor wafers, semiconductor devices, and hard disk substrates.

[0003] The CMP method will be described with reference to FIG. 1. As shown in FIG. 1, a polishing apparatus 1 for carrying out the CMP method is provided with a polishing pad 3, which contacts the object 8 to be polished held by a holding platen 16 and a retainer ring (not shown in FIG. 1) for holding the object 8 to be polished so as not to shift, and includes a polishing layer 4, which is a layer for polishing, and a cushion layer 6 for supporting the polishing layer 4. The polishing pad 3 is rotated while the object 8 to be polished is pressed against it, and polishes the object 8 to be polished. At that time, a slurry 9 is supplied between the polishing pad 3 and the object 8 to be polished. The slurry 9 is a mixture (dispersion liquid) of water, various chemical components, and hard fine abrasive grains, and the chemical components and abrasive grains in the slurry are flowed and move relative to the object 8 to increase the polishing effect. The slurry 9 is supplied to the polishing surface through grooves or holes and discharged.

[0004] Incidentally, the polishing pad 3 has conventionally been used with a polishing layer 4 made of polyurethane foam, but profile abnormalities of the polished object 8, particularly at the edge portion, which is the periphery of the polished object 8, may occur. Edge profile abnormalities include over-polishing, as shown in FIG. 2, in which the very end of the polished object 8 is polished more than the center, called "end sagging" (8a in FIG. 2), and polishing defects, as shown in FIG. 2, in which the polishing rate becomes unstable and unevenness occurs at the periphery slightly inside the very end, called "rebound" (8b in FIG. 2). In FIG. 3, which shows the polishing rate (RR) on the vertical axis and the distance on the line passing through the center of the polished object 8 ("0" on the horizontal axis is the center of the polished object) for the polished object polished by the polishing pad of the prior art, it can be seen that edge profile abnormalities occur, such as end sagging, in which the polishing rate at the very end of both ends is larger than other parts, and rebound, in which unevenness occurs at the periphery slightly inside the very end of both ends. This edge sagging can be a problem in semiconductor polishing (especially in the process of polishing oxide films), especially when the polishing rate at the outermost edge (periphery) of the workpiece is 1.5 times or more higher than that of other parts of the workpiece.

[0005] In response to this over-polishing phenomenon known as edge sagging, Patent Document 1 discloses a polishing pad that prevents edge sagging while suppressing the occurrence of polishing scratches by controlling the hardness of the polishing layer within a certain range through the use of a specific bubble structure in the foam.

[0006] Patent Document 2 discloses a polishing pad that does not have the problem of edge sagging by setting the hardness and tear strength of the polishing layer within a specific range. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2012-714 A [Patent Document 2] JP 2016-190313 A Summary of the Invention [Problem to be solved by the invention]

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

[0009] The present invention has been made in consideration of the above problems, and aims to provide a polishing pad that makes it possible to improve profile abnormalities in the edge portions, such as end sagging and rebound, without significantly changing the physical properties and bubble structure of the polishing layer. [Means for solving the problem]

[0010] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by using a cushion layer having a specific Poisson's ratio and a specific Shore A hardness. 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 cushioning layer disposed on the opposite side of the polishing surface of the polishing layer; The cushion layer has a Poisson's ratio of 0 to 0.15 and a Shore A hardness of 10 to 80. [2] The polishing pad according to [1], wherein the Poisson's ratio of the cushion layer is 0.01 to 0.1. [3] The polishing pad according to [1] or [2], wherein the difference between the Poisson's ratio of the cushion layer and the Poisson's ratio of the polishing layer (Poisson's ratio of the polishing layer - Poisson's ratio of the cushion layer) is 0.3 or more. [4] The polishing pad according to any one of [1] to [3], wherein the cushion layer has teardrop-shaped bubbles. [5] The polishing pad according to any one of [1] to [3], wherein the cushion layer has fine bubbles. Effect of the Invention

[0011] According to the polishing pad of the present invention, by using a cushion layer having a specific Poisson's ratio and a specific Shore A hardness, it is possible to suppress profile abnormalities in the edge portion such as end sagging and rebound without changing the physical properties and cell structure of the polishing layer. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view of a polishing apparatus 1. As shown in FIG. [Diagram 2] FIG. 2 is a side view of an object 8 to be polished, which has an abnormal profile at its edge portion. [Diagram 3] FIG. 3 shows a profile of the polishing rate of the entire object 8 polished by the conventional technique (polishing pad of Comparative Example 1) along a straight line passing through the center of the object 8. [Figure 4] FIG. 4 shows a profile of the polishing rate of the edge portion of an object 8 polished by the conventional technique (the polishing pad of Comparative Example 1). [Diagram 5] FIG. 5(a) is a perspective view and (b) is a cross-sectional view of a polishing pad 3 of the present invention. [Figure 6] FIG. 6 is a cross-sectional view showing the state of stress in the polishing pad during polishing. [Figure 7] FIG. 7 shows a profile of the polishing rate of the entire object 8 polished using the polishing pad of Example 1 along a straight line passing through the center of the object 8. As shown in FIG. [Figure 8] FIG. 8 shows a profile of the polishing rate of the edge portion of the object 8 polished using the polishing pad of Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, a mode for carrying out the invention will be described, however, the present invention is not limited to the mode for carrying out the invention.

[0014] <<Polishing pad>> The structure of the polishing pad 3 will be described with reference to Fig. 5. As shown in Fig. 5, the polishing pad 3 includes a polishing layer 4 and a cushion layer 6. The shape of the polishing pad 3 is preferably disc-shaped, but is not particularly limited, and the size (diameter) can be appropriately determined depending on the size of the polishing apparatus 1 equipped with the polishing pad 3, and can be, for example, about 10 cm to 2 m in diameter. In the polishing pad 3 of the present invention, the polishing layer 4 is preferably bonded to the cushion layer 6 via an adhesive layer 7 as shown in FIG. The polishing pad 3 is attached to a polishing platen 10 of the polishing device 1 by double-sided tape or the like arranged on the cushion layer 6. The polishing pad 3 is rotated by the polishing device 1 while being pressed against an object 8 to be polished, and polishes the object 8 to be polished.

[0015] <Polishing layer> (composition) The polishing pad 3 includes a polishing layer 4 that is a layer for polishing an object to be polished 8. The material constituting the polishing layer 4 can be suitably selected from polyurethane resin, polyurea resin, and polyurethane-polyurea resin, and more preferably polyurethane resin. The size (diameter) of the polishing layer 4 is the same as that of the polishing pad 3 and can be about 10 cm to 2 mm 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 platen 10 of the polishing device 1, and while a slurry 9 is poured onto it, the chemical components and abrasive grains contained in the slurry 9 are moved relative to the object 8 to be polished, thereby polishing the object 8 to be polished. Hollow microspheres 4A (foamed) are dispersed in the polishing layer 4. Due to the dispersion of the hollow microspheres 4A, when the polishing layer is worn, the hollow microspheres 4A are exposed on the polishing surface, and minute voids are generated on the polishing surface. These minute voids hold the slurry, and the polishing of the object 8 to be polished can be progressed further.

[0016] (grooving) The surface of the polishing layer 4 of the present invention facing the polished object 8 may be provided with grooves as necessary. The grooves are not particularly limited, and may be either slurry discharge grooves communicating with the periphery of the polishing layer 4 or slurry holding grooves not communicating with the periphery of the polishing layer 4, or may have both slurry discharge grooves and slurry holding grooves. Examples of the slurry discharge grooves include lattice grooves and radial grooves, and examples of the slurry holding grooves include concentric grooves and perforations (through holes), and these may also be combined. In low-pressure polishing, the platen is rotated at high speed in order to reduce the pressing force against the workpiece 8 and to ensure the polishing rate. This may cause the so-called hydroplaning phenomenon, in which the slurry 9 exists in a layer between the polishing surface and the processing surface and interferes with the polishing process. This phenomenon can be suppressed by forming grooves on the polishing surface. It is also possible to promote the discharge of polishing waste and the movement of the polishing liquid. The cross-sectional shape of the groove may be U-shaped, V-shaped, or semicircular. There is no particular restriction on the pitch, width, and depth of the groove. In addition, in order to improve the flatness of the polishing pad 3, a surface grinding process such as buffing may be performed on the polishing surface side or the surface opposite to the polishing surface of the polishing pad 3.

[0017] (Shore D hardness) The Shore D hardness of the polishing layer 4 of the present invention is not particularly limited, but is preferably 40 to 70. The Shore D hardness of the polishing layer 4 is 40 to 70, which is a conventionally used material, but by combining a Shore D hardness of 40 to 70 with a specific compression modulus of the cushion layer 6 described later, the end sagging of the polished object 8 can be improved. If the Shore D hardness is less than 40 degrees, it becomes difficult to flatten fine irregularities by low-pressure polishing. If it exceeds 70 degrees, abrasive particles and the like may be strongly rubbed against the polished object 8, causing scratches on the processed surface of the polished object 8. The lower limit of the Shore D hardness of the polishing layer 4 is preferably 40 or more, 42 or more, and 45 or more, and the upper limit is preferably 70 or less, 65 or less, and 60 or less, in that order.

[0018] (Poisson's ratio) The Poisson's ratio of the polishing layer 4 is not particularly limited. The Poisson's ratio of the polishing layer 4 is, for example, 0.20 to 0.50, and preferably 0.30 to 0.40. If the Poisson's ratio of the polishing layer 4 is smaller than 0.20, it may not show sufficient elasticity and the polishing rate may decrease. In addition, the upper limit of the Poisson's ratio is 0.5, and a material with a Poisson's ratio close to 0.5 is a special material such as a rubber material, which has strong water repellency and cannot hold polishing slurry, etc.

[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 curing agent (chain extender) into a mold, hardening the mixture, and slicing the hardened foam. That is, the polishing layer 4 is dry molded.

[0020] In the polishing pad 3 of the present invention, hollow microspheres 4A are used to encapsulate air bubbles inside the polyurethane resin molded body. The hollow microspheres 4A refer to microspheres having voids. The shapes of the hollow microspheres 4A include spherical, elliptical, and shapes similar thereto. Examples include those of a pre-expanded type and those of a type in which unexpanded heat-expandable microspheres are added at the raw material mixing stage and then heat-expanded. The physical properties of the abrasive layer 4, such as the Shore D hardness, can be adjusted to a desired range by adjusting the composition of the abrasive layer 4, the number and size of the hollow microspheres 4A, and the like.

[0021] <Cushion 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 polished object 8 more uniform. Examples of materials for the cushion layer 6 include resins; impregnated materials in which the resin is impregnated into a base material; flexible materials such as synthetic resins and rubbers; and sponge materials using the resins. Examples of the resins include resins such as polyurethane, polyethylene, polybutadiene, and silicone, and rubbers such as natural rubber, nitrile rubber, and polyurethane rubber.

[0022] More preferably, the cushion layer 6 is made of polyurethane resin that has been desolvated with a water-based coagulation liquid (coagulation liquid mainly composed of water) and formed into a sheet (wet film formation). The cushion layer 6 has a foam structure with teardrop-shaped bubbles 6A formed therein. The cushion layer 6 is also preferably made of polyurethane resin having sponge-like fine bubbles.

[0023] (Poisson's ratio) One of the characteristics of the cushion layer 6 of the polishing pad 3 of the present invention is that it has a Poisson's ratio of 0 to 0.15. Here, the Poisson's ratio is the ratio of the strain that occurs perpendicular to the stress to the strain that occurs along the stress direction when stress is applied to an object within the elastic limit, and is affected by the material and composition of the cushion layer 6. Therefore, the material used for the cushion layer 6 is a material with a relatively low Poisson's ratio (Poisson's ratio of 0 to 0.15), and such a material is a material that is less likely to change shape due to pressure, so that lateral strain is suppressed.

[0024] A cushion layer 6 with a Poisson's ratio of 0 to 0.15 is effective in suppressing profile abnormalities at the edge portion, such as end sagging and rebound. When the cushion layer is made of a material with a high Poisson's ratio, as can be seen from FIG. 6, the area directly below the retainer ring 16A is pressed downward, causing large lateral strain. As a result, the area directly below the retainer ring 16A is slightly recessed, and the surrounding area rises. Accordingly, the edge of the workpiece 8 is over-polished. However, by setting the Poisson's ratio of the cushion layer 6 to 0 to 0.15, the rise around the area directly below the retainer ring 16A can be reduced, and partial over-polishing can be suppressed.

[0025] Methods for adjusting the Poisson's ratio include changing the material of the cushion layer 6 to a sponge material with fine bubbles formed therein or a suede material with teardrop-shaped bubbles formed therein, or changing the size or number of the bubbles. In addition, for example, when the material of the cushion layer 6 is a nonwoven fabric impregnated with resin, another method is to change the amount of resin.

[0026] Furthermore, the ratio of the Poisson's ratio of the cushion layer 6 to the Poisson's ratio of the polishing layer 4 (Poisson's ratio of the cushion layer / Poisson's ratio of the polishing layer) is preferably 0.05 to 0.30. Furthermore, the difference between the Poisson's ratio of the polishing layer 4 and the Poisson's ratio of the cushion layer 6 (Poisson's ratio of the polishing layer - Poisson's ratio of the cushion layer) is preferably 0.25 to 0.40. When the ratio of the Poisson's ratio of the cushion layer 6 to the Poisson's ratio of the polishing layer 4, or the difference between the Poisson's ratio of the polishing layer 4 and the Poisson's ratio of the cushion layer 6, is within the above-mentioned preferred range, profile abnormalities in the edge portions, such as end sagging and rebound, can be further suppressed.

[0027] (Shore A hardness) Furthermore, the cushion layer 6 has a Shore A hardness of 10 to 80. If the Shore A hardness is less than 10, sufficient strength cannot be exhibited, making it difficult to perform polishing. On the other hand, if the Shore A hardness exceeds 80, the layer is too hard, making it difficult for the polished object 8 and the polishing layer 4 to come into uniform contact with each other. A more preferable Shore A hardness is 20 to 70.

[0028] (density) The density of the cushion layer 6 in the polishing pad 3 of the present invention is not particularly limited, but may be, for example, 0.30 to 0.60. If the density is within this range, the cushioning properties can be ensured and the conventional polishing rate (polishing speed, RR) can be exhibited. The lower limit of the density is preferably 0.30, 0.32, and 0.33 in this order, and the upper limit of the density is preferably 0.60 or less, 0.58 or less, and 0.55 or less in this order. Note that the density here is not the density of the material itself, but the density of the cushion layer 6 in a state including air bubbles and a base material.

[0029] (Compressive elastic modulus) The compressive elastic modulus of the cushion layer 6 is not particularly limited, but is, for example, 80 to 100%, and preferably 85 to 100%.

[0030] (Air bubbles) The cushion layer 6 of the present invention preferably has interconnected bubbles, for example, teardrop-shaped bubbles or fine bubbles. FIG. 5 shows a cushion layer 6 having teardrop-shaped bubbles 6A. The teardrop-shaped bubbles 6A may be present inside the cushion layer 6 as shown in FIG. 5, or may be extended to the upper and / or lower surfaces of the cushion layer 6 by cutting the upper or lower surface of the cushion layer 6, so that there are holes on the upper and lower surfaces, or there are holes penetrating the upper and lower surfaces. The presence of teardrop-shaped bubbles 6A prevents the cushion layer 6 from becoming too hard. The cushion layer 6 can be produced by a wet film-forming method to have teardrop-shaped bubbles 6A.

[0031] <Adhesive layer> The adhesive layer 7 is a layer for adhering the cushion layer 6 and the polishing layer 4, and is usually made of a double-sided tape or adhesive. The double-sided tape or adhesive may be any known double-sided tape or adhesive in the art (e.g., an adhesive sheet). The polishing pad 3 and the cushion layer 6 are bonded together by an adhesive layer 7. The adhesive layer 7 can be formed of at least one adhesive selected from, for example, acrylic, epoxy, and urethane adhesives. For example, an acrylic adhesive is used, and the thickness can be set to 0.1 mm.

[0032] <<Polishing pad manufacturing method>> A method for producing the polishing pad 3 of the present invention will now be described.

[0033] <Abrasive layer material> The material of the polishing layer 4 is not particularly limited, but for example, the main component is preferably a polyurethane resin, a polyurea resin, or a polyurethane polyurea resin, and more preferably a polyurethane resin. Specific examples of the main component material include a material obtained by reacting a urethane bond-containing polyisocyanate compound with a curing agent.

[0034] Hereinafter, a method for producing the material of the polishing layer 4 will be described using an example in which a urethane bond-containing isocyanate compound, a polyol compound, and a curing agent are used.

[0035] Examples of a method for producing the polishing layer 4 using a urethane bond-containing polyisocyanate compound and a curing agent include a production method including: 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 molding the mixed liquid for molding a molded body into the polishing layer 4.

[0036] The material preparation process, the mixing process, and the molding process will be explained below.

[0037] <Material preparation process> To manufacture 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 a polyurethane resin molded body. When the polishing layer 4 is to be a polyurea resin molded body or a polyurethane-polyurea resin molded body, a prepolymer appropriate for the purpose is used.

[0038] Each component will be described below.

[0039] (Polyisocyanate compound containing urethane bonds) The urethane bond-containing polyisocyanate compound (urethane prepolymer) is a compound obtained by reacting the following polyisocyanate compound with a polyol compound under commonly used conditions, and contains a urethane bond and an isocyanate group in the molecule. In addition, other components may be contained in the urethane bond-containing polyisocyanate compound within the range that does not impair the effects of the present invention.

[0040] The urethane bond-containing polyisocyanate compound may be a commercially available product, or may be a product synthesized by reacting a polyisocyanate compound with a polyol compound. The reaction is not particularly limited, and addition polymerization may be performed using a method and conditions known in the production of polyurethane resins. For example, the polyisocyanate compound may be added to a polyol compound heated to 40°C while stirring in a nitrogen atmosphere, and the temperature may be raised to 80°C after 30 minutes, and the reaction may be continued at 80°C for 60 minutes. The urethane bond-containing polyisocyanate preferably has an NCO equivalent of about 300 to 600. Therefore, when the urethane bond-containing polyisocyanate is a commercially available product, it is preferable that the NCO equivalent falls within the above range, and when it is produced by synthesis, it is preferable to adjust the NCO equivalent to the above range by using the following raw materials in an appropriate ratio.

[0041] (Polyisocyanate compounds) In this specification, the polyisocyanate compound means a compound having two or more isocyanate groups in the molecule. The polyisocyanate compound is not particularly limited as long as it has two or more isocyanate groups in the molecule. For example, diisocyanate compounds having two isocyanate groups in the molecule include m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-tolylene diisocyanate (2,6-TDI), 2,4-tolylene diisocyanate (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'-biphenyl diisocyanate, 3,3'-dimethyl- Examples of the polyisocyanate 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, ethylidine diisothiocyanate, etc. These polyisocyanate compounds may be used alone or in combination of a plurality of polyisocyanate compounds.

[0042] The polyisocyanate compound preferably contains 2,4-TDI and / or 2,6-TDI.

[0043] (Polyol compounds as raw materials for prepolymers) In this specification, the polyol compound means a compound having two or more hydroxyl groups (OH) in the molecule. Examples of polyol compounds used in the synthesis of the urethane bond-containing polyisocyanate compound as a prepolymer include diol compounds, triol compounds, etc., such as ethylene glycol, diethylene glycol (DEG), butylene glycol, etc., and polyether polyol compounds, such as poly(oxytetramethylene) glycol (or polytetramethylene ether glycol) (PTMG). Among these, DEG and PTMG are preferred. Here, the PTMG that can be used is not particularly limited, but preferably has a number average molecular weight (Mn) of, for example, 500 to 2000. 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, each component can be decomposed by a conventional method such as amine decomposition, and then the number average molecular weight can be estimated by GPC. The above polyol compounds may be used alone or in combination of two or more.

[0044] (Additives) As described above, additives such as an oxidizing agent can be added to the material of the polishing layer 4, if necessary.

[0045] (hardening agent) In the method for producing the polishing layer 4 of the present invention, a curing agent (also called a chain extender) is mixed with a urethane bond-containing polyisocyanate compound, etc. in a mixing step. By adding the curing agent, in the subsequent molding step, the main chain terminal of the urethane bond-containing polyisocyanate compound bonds with the curing agent to form a polymer chain, which then hardens. Examples of the curing agent 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, 2,2-bis[3-(isopropylamino)-4- polyamine compounds such as 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, trimethylethylene bis-4-aminobenzoate, and polytetramethylene oxide-di-p-aminobenzoate; ethylene glycol, 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.The polyamine 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, di-2-hydroxypropylethylenediamine, etc. As the polyamine compound, a diamine compound is preferable, and it is more preferable to use, for example, 3,3'-dichloro-4,4'-diaminodiphenylmethane (methylenebis-o-chloroaniline) (hereinafter abbreviated as MOCA).

[0046] The polishing layer 4 can be formed by using a material to form hollow microspheres 4A, which have an outer shell and are hollow inside. The material of the hollow microspheres 4A may be a commercially available one, or may be one obtained by synthesis using a conventional method. The material of the outer shell of the hollow microspheres 4A is not particularly limited, and examples thereof 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 organic silicone resins, and copolymers of two or more types of monomers constituting these resins (for example, acrylonitrile-vinylidene chloride copolymers, etc.). In addition, examples of commercially available hollow microspheres include, but are not limited to, Expancel series (trade name manufactured by Akzo Nobel), Matsumoto Microsphere (trade name manufactured by Matsumoto Yushi Co., Ltd.), etc. The gas contained in the hollow microspheres 4A is not particularly limited, but may be, for example, a hydrocarbon, specifically, isobutane.

[0047] The shape of the hollow microspheres 4A is not particularly limited and may be, for example, spherical or nearly spherical. 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, further preferably 5 to 50 μm, and particularly preferably 5 to 35 μm. The average particle size can be measured by a laser diffraction particle size distribution analyzer (for example, Mastersizer 2000, manufactured by Spectris Co., Ltd.).

[0048] The material for the hollow microspheres 4A is added in an amount of preferably 0.1 to 10 parts by mass, more preferably 1 to 5 parts by mass, and even more preferably 1 to 4 parts by mass, based on 100 parts by mass of the urethane prepolymer.

[0049] In addition to the above components, conventionally used blowing agents may be used together with the hollow microspheres 4A within the range that does not impair the effects of the present invention, and a gas that is non-reactive with each of the above components may be blown in during the mixing step described below. Examples of the blowing agent include water and blowing agents mainly composed of hydrocarbons having 5 or 6 carbon atoms. Examples of the hydrocarbon include linear hydrocarbons such as n-pentane and n-hexane, and alicyclic hydrocarbons such as cyclopentane and cyclohexane.

[0050] <Mixing process> In the mixing step, the urethane bond-containing polyisocyanate compound (urethane prepolymer) obtained in the preparation step, additives, and curing agent are fed into a mixer and stirred and mixed. The mixing step is carried out in a state where the components are heated to a temperature at which the fluidity of each component can be ensured.

[0051] <Forming process> In the molding process, the mixture for molding prepared in the mixing process is poured into a rod-shaped mold preheated to 30 to 100°C for primary curing, and then heated at about 100 to 150°C for about 10 minutes to 5 hours for secondary curing to form a cured polyurethane resin (polyurethane resin molded body). At this time, the urethane prepolymer and the curing agent react to form a polyurethane resin, and the mixture hardens. If the viscosity of the urethane prepolymer is too high, the fluidity is poor and it becomes difficult to mix uniformly during mixing. If the temperature is increased to decrease the viscosity, the pot life is shortened, and mixing spots occur, resulting in variation in the size of the hollow microspheres 4A formed in the resulting foam. On the other hand, if the viscosity is too low, the bubbles move in the mixed liquid, making it difficult to form the hollow microspheres 4A dispersed 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 can be achieved, for example, by changing the molecular weight (degree of polymerization) of the prepolymer. The prepolymer is heated to about 50 to 80°C to be in a flowable state.

[0052] In the molding process, the mixture is reacted in a mold as necessary to form a foam. At this time, the prepolymer is crosslinked and hardened by the reaction between the prepolymer and the hardener.

[0053] After obtaining the molded body, it is sliced ​​into sheets to form a plurality of polishing layers 4. A general slicing machine can be used for slicing. During slicing, the lower part of the polishing layer 4 is held, and the polishing layer 4 is sliced ​​to a predetermined thickness starting from the upper part. The slice thickness is set to, for example, a range of 1.3 to 2.5 mm. In the case of a foam molded in a 50 mm thick mold, 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 about 30 mm of the center. In the hardening and molding step, a foam is obtained in which hollow microspheres 4A are formed approximately uniformly inside.

[0054] The polishing surface of the obtained polishing layer 4 is grooved as necessary. By performing cutting or the like on the polishing surface using a required cutter, grooves having any pitch, width, and depth can be formed. Examples of the slurry retaining grooves include circular grooves formed in a concentric circle shape, and examples of the slurry discharging grooves include linear grooves formed in a lattice shape and linear grooves formed radially from the center of the polishing layer.

[0055] Thereafter, a double-sided tape is attached to the surface of the polishing layer 4 opposite to the polishing surface of the polishing layer 4 obtained in this manner. There are no particular limitations on the double-sided tape, and any double-sided tape known in the art can be selected and used.

[0056] <Method of manufacturing the cushion layer 6> As described above, the material of the cushion layer 6 includes an impregnated material in which resin fibers such as polyethylene or polyester (nonwoven fabric, flexible film, etc.) are impregnated with a resin solution such as urethane; a suede material using a resin material such as urethane; and a sponge material using a material such as urethane. Among these, the manufacturing method of an impregnated woven or nonwoven fabric using polyurethane resin and a suede material using a resin material such as urethane will be described. The cushion layer 6 can be manufactured according to the manufacturing method described below, but a commercially available product can also be used.

[0057] <In the case of impregnated materials and suede materials> In the process of forming the cushion layer 6, the cushion layer 6 is formed by a wet film formation. That is, the cushion layer 6 is formed through each of the steps of a preparation step of preparing a resin solution in which a polyurethane resin is dissolved substantially uniformly in an organic solvent, a coagulation regeneration step of spreading the resin solution prepared in the preparation step into a sheet shape and removing the organic solvent from the resin solution in a water-based coagulation liquid to coagulate and regenerate a polyurethane body, and a washing and drying step of washing and drying the polyurethane body coagulated and regenerated in the coagulation regeneration step to form the cushion layer 6, which will be described in the order of steps below.

[0058] (preparation process) In the preparation step, a polyurethane resin and, if necessary, an additive are dissolved in an organic solvent to prepare a resin solution. The resin solution is prepared by dissolving the polyurethane resin and the additives substantially uniformly in a water-miscible organic solvent capable of dissolving the polyurethane resin, removing aggregates 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, and other resins.

[0059] As additives to be added as required, pigments such as carbon black, hydrophilic activators that promote foaming, and hydrophobic activators that stabilize the solidification and regeneration of polyurethane resin can be used. By changing the type and amount of additives, the size and amount (number) of teardrop-shaped bubbles 6A formed inside the cushion layer 6 can be controlled. The Poisson's ratio and Shore A hardness of the cushion layer 6 can be adjusted by selecting the polyurethane resin and organic solvent, the mixing ratio of the resin and the organic solvent, the size and amount of the teardrop-shaped bubbles 6A, and the thickness of the cushion layer 6. For example, the polyurethane resin is set to a range of 45 to 62 parts and the DMF to a range of 8 to 30 parts per 100 parts of the resin solution.

[0060] (Coagulation regeneration process) In the coagulation regeneration process, the resin solution prepared in the preparation process is continuously applied (spread into a sheet) to the film-forming substrate, and the polyurethane resin is coagulated and regenerated into a sheet by immersing in a water-based coagulation liquid. The resin solution prepared in the preparation process is applied substantially uniformly to the strip-shaped film-forming substrate by a coating machine such as a knife coater at room temperature. At this time, the coating thickness (coating amount) of the resin solution is adjusted by adjusting the gap (clearance) between the coater and the film-forming substrate. In this example, the coating amount 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 nonwoven fabrics or woven fabrics are used, in order to suppress the penetration of the resin solution into the film-forming substrate when it is applied, a pretreatment (sealing) is performed by immersing the nonwoven fabrics or woven fabrics in water or a DMF aqueous solution (a mixture of DMF and water) or the like. When a flexible film such as a PET film is used as the film-forming substrate, the pretreatment is not required because it does not have liquid permeability.

[0061] The film-forming substrate coated with the resin solution is immersed in an aqueous coagulating liquid mainly composed of water, which is a poor solvent for polyurethane resin. In the aqueous coagulating liquid, micropores constituting a skin layer are first formed on the surface of the coated resin solution to a thickness of about several μm. Then, as the replacement of DMF in the resin solution with the aqueous coagulating liquid progresses, the polyurethane body is coagulated and regenerated in a sheet shape on one side of the film-forming substrate. As the DMF is desolvated from the resin solution and the DMF is replaced with the aqueous coagulating liquid, a large number of teardrop-shaped bubbles 6A are formed in the polyurethane body, and the teardrop-shaped bubbles 6A are formed in a three-dimensional mesh shape. At this time, since 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. That is, inside the polyurethane body, a large number of bubbles 6A with rounded and approximately triangular cross sections are formed in a substantially uniformly distributed state along the thickness direction of the polyurethane body.

[0062] (Cleaning and drying process) In the washing and drying process, the strip-shaped (long) polyurethane body that has been coagulated and regenerated in the coagulation and regeneration process is washed and then dried to form the cushion layer 6. That is, the polyurethane body is washed in a washing liquid such as water to remove the DMF remaining in the polyurethane body. After washing, the polyurethane body is dried in a cylinder dryer. The cylinder dryer is equipped with a cylinder with a heat source inside. The polyurethane body passes along the circumferential surface of the cylinder to dry, and the cushion layer 6 is formed.

[0063] <Joining process> In the bonding step, the formed polishing layer 4 and cushion layer 6 are bonded (bonded) 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 the polishing surface P with a substantially uniform thickness. The surface of the polishing layer 4 opposite 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 the cushion layer 6 are bonded with the adhesive layer 7. Then, after cutting into a desired shape such as a circle, an inspection is performed to confirm that there is no dirt or foreign matter attached, and the polishing pad 3 is completed. EXAMPLES

[0064] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0065] In each of the examples and comparative examples, unless otherwise specified, "parts" means "parts by mass".

[0066] In addition, the NCO equivalent is a value indicating the molecular weight of the prepolymer (PP) per NCO group, which is calculated by (mass (parts) of polyisocyanate compound + mass (parts) of polyol compound) / [(number of functional groups per molecule of polyisocyanate compound × mass (parts) of polyisocyanate compound / molecular weight of polyisocyanate compound)-(number of functional groups per molecule of polyol compound × mass (parts) of polyol compound / molecular weight of polyol compound)].

[0067] (Regarding abrasive layer A) 2.6 parts of unexpanded hollow microspheres, the shell of which is made of acrylonitrile-vinylidene chloride copolymer and contains isobutane gas in the shell, were added and mixed with 100 parts of isocyanate-terminated urethane prepolymer with an NCO equivalent of 460, which was made by reacting 2,4-tolylene diisocyanate (TDI), poly(oxytetramethylene) glycol (PTMG) and diethylene glycol (DEG), to obtain a mixed liquid. The resulting mixed liquid was charged into a first liquid tank and kept warm. Next, 25.5 parts of MOCA and 8.5 parts of polypropylene glycol (PPG) were added and mixed as hardeners separately from the first liquid, and kept warm in a second liquid tank. The liquids in the first liquid tank and the second liquid tank were each injected into a mixer equipped with two injection ports so that the R value, which represents the equivalent ratio of the amino group and hydroxyl group present in the hardener to the terminal isocyanate group in the prepolymer, was 0.90. The two injected liquids were mixed and stirred while being injected into a preheated mold of a molding machine, then the mold was clamped and heated for 30 minutes for primary curing. The primarily cured molded product was demolded and then 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, and then heated again in an oven at 120°C for 5 hours, after which it was sliced ​​to a thickness of 1.3 mm to obtain abrasive layer A.

[0068] (Regarding polishing layer B) Polishing layer B was prepared in the same manner as polishing layer A, except that the first liquid mixture used in polishing layer A was a mixture of 100 parts of an isocyanate-terminated urethane prepolymer having an NCO equivalent of 455 and 2.7 parts of unexpanded hollow microspheres, and the second liquid used in polishing layer A was only 25.8 parts of MOCA.

[0069] (Regarding cushion layers (I) to (IV)) Polyester MDI (diphenylmethane diisocyanate) polyurethane resin was used as the polyurethane resin for preparing the cushion layer (I). 25 parts of DMF solvent, 40 parts of DMF dispersion containing 20% ​​carbon black as a pigment, and 2 parts of hydrophobic activator as a film formation stabilizer were added to 100 parts of 30% polyurethane resin solution and mixed to prepare a polyurethane resin solution. The obtained resin solution was applied to a PET substrate (thickness 0.188 mm) to a thickness of 0.7 mm, and the organic solvent was removed from the resin solution in a water-based coagulation liquid to prepare the cushion layer (I) including the PET substrate. A commercially available polyurethane sheet having fine bubbles ("PORON H-32" manufactured by Inoac Corporation) was used as the cushion layer (II). A commercially available polyurethane sheet having fine bubbles ("PORON HH-48C" manufactured by Inoac Corporation) was used as the cushion layer (III). Nonwoven fabric made of polyester fibers (density: 0.216 g / cm 3 ) was immersed in a urethane resin solution (manufactured by DIC Corporation, product name "C1367"). After immersion, the resin solution was squeezed out using a mangle roller capable of applying pressure between a pair of rollers, and the nonwoven fabric was impregnated with the resin solution approximately uniformly. Next, the nonwoven fabric was immersed in a coagulating liquid made of water at room temperature to coagulate and regenerate the impregnated resin, thereby obtaining a resin-impregnated nonwoven fabric. Thereafter, the resin-impregnated nonwoven fabric was taken out of the coagulating liquid, and further immersed in a cleaning liquid made of water to remove N,N-dimethylformamide (DMF) in the resin, and then dried. After drying, the surface skin layer was removed by buffing treatment to prepare a cushion layer (IV). The resin adhesion rate of the cushion layer (IV) was 55%, and the thickness was 1.301 mm.

[0070] Examples and Comparative Examples The polishing layers A and B and the cushion layers (I) to (IV) were joined 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 cushion layer and the opposite side of the adhesive layer to produce polishing pads of the examples and comparative examples. Examples 1 to 3 were polishing pads using the polishing layer A and the cushion layers (I) to (III), Examples 4 to 6 were polishing pads using the polishing layer B and the cushion layers (I) to (III), and Comparative Examples 1 and 2 were polishing pads using the polishing layer A and the cushion layer (IV) and the polishing layer B and the cushion layer (IV), respectively.

[0071] (Shore A hardness measurement) The Shore A hardness was determined from the indentation depth of a pin pressed against the surface of the test piece via a spring in accordance with the Japanese Industrial Standards (JIS K 7311). The Shore A hardness of each cushion layer is shown in Table 1. (Poisson's ratio measurement) Using a strain gauge and a universal testing machine (UTM), the Poisson's ratio of each abrasive layer and each cushion layer was measured under the conditions of a test speed of 1 mm / min, a grip distance of 115 mm, a load cell of 30 N, a temperature of 23±2°C and a humidity of 45±5%. The measurement results are shown in Table 1.

[0072] [Table 1]

[0073] (Polishing test) Polishing was carried out with the polishing pads of each Example and Comparative Example under the polishing conditions below. During polishing, the polishing rate (RR) was measured at 121 points around the diameter. The polishing rate profile of the entire workpiece of Comparative Example 1 is shown in FIG. 3, the polishing rate profile of the edge portion of the workpiece of Comparative Example 1 is shown in FIG. 4, the polishing rate profile of the entire workpiece of Example 1 is shown in FIG. 7, and the polishing rate profile of the edge portion of the workpiece of Example 1 is shown in FIG. 8. The measurements were made at 2.5 mm pitches inside a radius of 140 mm, and at 1 mm pitches outside.

[0074] (polishing conditions) Polishing machine used: F-REX300 (manufactured by Ebara Corporation) Abrasive temperature: 20℃ Polishing platen rotation speed: 70 rpm Polishing head rotation speed: 71 rpm Grinding pressure: 3.5psi Polishing slurry: Cabot Microelectronics Corporation, product name: SS25 Polishing slurry flow rate: 200ml / min Polishing time: 60 seconds Workpiece: Silicon wafer with TEOS (Tetra Ethyl Ortho Silicate)

[0075] The polishing results of each polishing pad of the examples and comparative examples are shown in Table 2. The "edge rate" of the polishing results was calculated by dividing the polishing rate of the edge of the workpiece (part 149 mm from the center) by the average of the polishing rates of parts 100 to 140 mm from the center. The presence or absence of rebound was confirmed by checking whether there were any irregularities in the polishing rate just before the edge (part outside 140 mm from the center).

[0076] [Table 2]

[0077] As shown in Figures 3 and 4 and Table 2, in the polishing pad of Comparative Example 1, which has a large Poisson's ratio of the cushion layer, the rate at the very edge was large at 1.61, and edge sagging was confirmed, as well as the phenomenon of rebound being confirmed at approximately 144 mm from the center of the workpiece. Similarly, in Comparative Example 2, in which the polishing layer was changed to Polishing Layer B, the phenomenon of edge sagging and rebound was confirmed. On the other hand, as shown in Figures 7 to 8 and Table 2, in the polishing pad of Example 1 using the cushion layer (I) having teardrop-shaped bubbles with a low Poisson's ratio of 0.085, the rate at the most edge portion was suppressed to 1.31, or less than 1.5, and no rebound was observed just before the most edge portion. The polishing pads of Examples 2 and 3 using cushion layers (II) and (III) having different bubble structures and similarly low Poisson's ratios showed similar results. Also, in Examples 4 to 6 in which the polishing layer was changed to polishing layer B, the Poisson's ratio·A hardness was set within a predetermined range, so that the increase in the polishing rate at the most edge portion (end sagging) and the rebound just before the most edge portion could be suppressed, and a good edge profile could be obtained. [Industrial Applicability]

[0078] INDUSTRIAL APPLICABILITY The present invention provides a polishing pad that makes it possible to improve profile abnormalities in edge portions such as end sagging and rebound, and therefore contributes to the manufacture and sale of polishing pads, and thus has industrial applicability.

[0079] 1 Polishing equipment 3 Polishing Pads 4 Polishing layer 4A Hollow microsphere 6 Cushioning Layer 6A Teardrop bubble 7 Adhesive layer 8 Object to be polished 8a End droop 8b Rebound 9. Slurry 10 Polishing plate 11 Foundation 16 Holding Plate

Claims

1. The polishing pad comprises 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 cushion layer has a Poisson's ratio of 0 to 0.15 and a Shore A hardness of 10 to 80; a difference between the Poisson's ratio of the cushion layer and the Poisson's ratio of the polishing layer (Poisson's ratio of the polishing layer - Poisson's ratio of the cushion layer) is 0.3 or more; The polishing layer of the polishing pad comprises a urethane bond-containing polyisocyanate compound which is a reaction product of tolylene diisocyanate (TDI), poly(oxytetramethylene) glycol (PTMG), and diethylene glycol (DEG).

2. 2. The polishing pad according to claim 1, wherein the Poisson's ratio of the cushion layer is 0.01 to 0.

1.

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

4. The polishing pad according to claim 1 , wherein the cushion layer has microbubbles.

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