Polishing pad

Abstract

The present invention provides a polishing pad with a long polishing life while suppressing over-polishing on the outer periphery of the workpiece. [Solution] A polishing pad comprising a circular polishing layer, wherein the polishing layer has a stepped portion having a gear-like shape centered on the center point of the polishing layer, and the side wall of the stepped portion is at an angle of 60 degrees or more and 90 degrees or less with respect to a surface extending the bottom surface of the stepped portion in the direction of the side wall.

Description

Technical Field

[0001] The present invention relates to a polishing pad. The polishing pad of the present invention is used for polishing optical materials, semiconductor devices, glass substrates for hard disks, etc., and is particularly preferably used for polishing devices in which an oxide layer, a metal layer, etc. are formed on a semiconductor wafer.

Background Art

[0002] In the process of forming an insulating film or metal wiring in semiconductor manufacturing, polishing of a semiconductor wafer or the like is performed by a so-called chemical mechanical polishing (CMP) method in which a polishing liquid (hereinafter referred to as slurry) containing abrasive grains is supplied between a polishing pad and the wafer, and they are relatively slid while being pressurized to flatten the wafer surface by a combined action of chemical action and mechanical polishing.

[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 contacts a workpiece 8 held by a retainer ring (not shown in FIG. 1) that holds the holding surface plate 16 and the workpiece 8 so as not to shift, and includes a polishing layer 4 that is a layer for polishing and a base material layer 6 that supports the polishing layer 4. The polishing pad 3 is rotationally driven while the workpiece 8 is pressed, and polishes the workpiece 8. At that time, slurry 9 is supplied between the polishing pad 3 and the workpiece 8. The slurry 9 is a mixture (dispersion liquid) of water, various chemical components, and hard fine abrasive grains. While the chemical components and abrasive grains in it 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] In recent years, with the further miniaturization of semiconductor wiring, greater planarization is required in the CMP process. In the CMP method described above, in addition to polishing the entire surface of the workpiece (wafer), polishing defects unique to the outer periphery can occur, where the outer edge of the workpiece is polished more than the central part. The outer periphery of the workpiece refers to the part along the outer edge, specifically the part inside the outer edge, for example, the part up to a length of 0.1 when the radius is set to 1 from the outer edge. This is thought to be because the pressure between the workpiece and the polishing pad tends to be uneven in the outer periphery of the workpiece during polishing, and the pressure in the outer periphery of the workpiece is relatively greater compared to other parts, resulting in the outer periphery of the workpiece being polished more strongly.

[0005] As a method to suppress overpolishing of the outer periphery of the workpiece, Patent Document 1 discloses a polishing pad that suppresses overpolishing of the outer periphery of the workpiece by making the thickness of the polishing layer on the polishing surface side thinner in the radial direction. However, in polishing layers where the thickness changes continuously in the radial direction, the difference in thickness is expected to decrease each time the polishing layer is dressed, making it difficult to achieve stable polishing performance (polishing life).

[0006] Therefore, there is a need for polishing pads that improve polishing defects (over-polishing) on ​​the outer periphery of the workpiece and have a longer polishing life. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2008-279553 [Overview of the project] [Problems that the invention aims to solve]

[0008] This invention has been made in view of the above problems, and aims to provide a polishing pad with a long polishing life while suppressing over-polishing on the outer circumference of the workpiece. [Means for solving the problem]

[0009] As a result of their research, the inventors have found a polishing pad that reduces contact between the polishing layer and the workpiece by forming a stepped portion in the region near the center of the polishing layer, thereby suppressing over-polishing on the outer periphery of the workpiece. The present invention encompasses the following: [1] A polishing pad comprising a circular polishing layer, The polishing layer comprises a stepped portion having a gear-like shape centered on the central point of the polishing layer, A polishing pad in which the side wall of the stepped portion is at an angle of 60 degrees or more and 90 degrees or less with respect to the extension plane of the bottom surface of the stepped portion in the direction of the side wall. [2] The stepped portion is formed within a stepped portion forming region, which is a circular region centered on the center point of the polishing layer and having a radius of 0.2 or less relative to the radius of the polishing layer. The stepped portion forming region is composed of a circular region centered on the center point of the polishing layer and having a radius of 0 or more and less than 0.2 relative to the radius of the polishing layer, and an annular region centered on the center point of the polishing layer and having a radius of 0.1 or more and 0.2 or less relative to the radius of the polishing layer, with the circular region removed from the circle. The polishing pad according to [1], wherein a circular step portion is arranged in the circular region, and a gear-shaped step portion is arranged in the annular region. [3] The polishing pad according to [2], wherein the total area of ​​the stepped portion of the tooth shape in the annular region is 0.2 or more and less than 1.0 of the total area of ​​the annular region. [4] The polishing pad according to any one of [1] to [3], wherein the polishing layer is a polyurethane resin sheet having closed cells. [5] The polishing pad according to any one of [1] to [4], wherein the outer circumference of the workpiece being polished passes through the annular region when the workpiece is closest to the center point during polishing. [6] The polishing pad according to any one of [1] to [5], wherein the polishing layer has a plurality of outer peripheral stepped portions formed along the outer circumference of the polishing surface. [7] The polishing pad according to any one of [1] to [6], wherein the step height of the stepped portion is smaller than the thickness of the polishing layer. A method for manufacturing an abrasive pad as described in any one of [8] [1] to [7], A manufacturing method wherein the aforementioned multiple stepped portions are formed by counterboring. [9] A polishing pad including an abrasive layer, The polishing layer has a circular through-hole centered on the center point of the polishing layer, A stepped portion formed so as to be in contact with the central hole, A polishing pad equipped with the following features.

[10] The polishing pad according to [9], further comprising an outer peripheral step portion in contact with the outer circumference of the polishing surface in the polishing layer. [Effects of the Invention]

[0010] By forming a stepped portion in the region near the center of the polishing layer, the contact area with the outer periphery of the workpiece is reduced, thereby suppressing over-polishing of the outer periphery of the workpiece. Furthermore, since the structure of this stepped portion does not change (the degree of contact with the workpiece does not change) even as polishing progresses, over-polishing can be stably suppressed. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a schematic diagram of the polishing process. [Figure 2] Figure 2 is a schematic diagram of a cross-section perpendicular to the polishing surface, showing the deformation of the polishing layer near the outer circumference of the workpiece during polishing and the relative pressure between the workpiece and the polishing pad in a conventional polishing pad (arrow a indicates the direction of excessive pressure. Arrow b indicates the direction of polishing pressure and the direction of the repulsive force against polishing pressure). [Figure 3] Figure 3 is a schematic diagram of a cross-section perpendicular to the polishing surface, showing the state of the slurry near the outer circumference of the workpiece during polishing in a conventional polishing pad (arrow c indicates the direction of centrifugal force). [Figure 4] Figure 4 shows the trajectory that point d on the outer circumference of the workpiece to be polished passes through on the polishing surface during polishing. [Figure 5]FIG. 5 is a schematic diagram showing the locus through which the outer peripheral portion of the workpiece passes on the polishing surface during polishing. [Figure 6] [[ID=像3]]FIG. 6 is a diagram showing a step formation region (diameter D) for forming a step based on the locus. [Figure 7] FIG. 7 is a view of the polishing pad having a step portion according to an embodiment of the invention as viewed from a direction perpendicular to the polishing surface. [Figure 8] FIG. 8 is a cross-sectional view of the polishing pad and the workpiece during polishing. [Figure 9] FIG. 9 is a schematic diagram of an embodiment of the step formation region. [Figure 10] FIG. 10 is a schematic diagram of an embodiment of the step formation region. [Figure 11] FIG. 11 is a schematic diagram of the polishing layer 4C obtained in the example. [Figure 12] FIG. 12 is a schematic cross-sectional view taken along the line X-X of the polishing layer 4C. [Figure 13] FIG. 13 is a schematic diagram of the polishing layer 4D obtained in the example.

MODE FOR CARRYING OUT THE INVENTION

[0012] Hereinafter, the embodiments for carrying out the invention will be described, but the present invention is not limited to the embodiments for carrying out the invention.

[0013] <<Polishing Pad>> The structure of the polishing pad 3 will be described. The polishing pad 3 is circular and includes a polishing layer 4 and a base material layer 6. The size (diameter) of the polishing pad 3 can be appropriately determined according to the size of the polishing apparatus 1 provided with the polishing pad 3, etc., and for example, it can be about 10 cm to 2 m in diameter. In addition, in the polishing pad 3 of the present invention, preferably, the polishing layer 4 is adhered to the base material layer 6 via an adhesive layer. The polishing pad 3 is attached to the polishing surface plate 10 of the polishing apparatus 1 by a double-sided tape or the like disposed on the base material layer 6. As shown in FIG. 1, the polishing pad 3 is rotationally driven while pressing the workpiece 8 by the polishing apparatus 1 to polish the workpiece 8.

[0014] Here, we will explain over-polishing of the outer periphery of the workpiece using Figures 2 and 3. In CMP polishing, the workpiece is polished while being pressed against the polishing pad. As shown in Figure 2, the polishing layer near the outer circumference of the workpiece is deformed by the retainer ring 5, so excessive pressure is applied to the outer circumference of the workpiece, making over-polishing likely (arrow a: direction of excessive pressure, arrow b: direction of polishing pressure and direction of the repulsive force against polishing pressure). Furthermore, as shown in Figure 3, due to the influence of centrifugal force, slurry tends to accumulate near the outer circumference of the workpiece, making over-polishing of the outer circumference of the workpiece more likely (arrow c: direction of centrifugal force).

[0015] <Polishing layer> The polishing layer 4 rotates together with the polishing platen 10 of the polishing device 1, and while the slurry 9 is flowed over it, the chemical components and abrasive grains contained in the slurry 9 move relative to the workpiece 8, thereby polishing the workpiece 8.

[0016] <Explanation of the trajectory of the workpiece> When the workpiece 8 being polished is closest to the center point of the circle of the polishing layer 4, the outer circumference of the workpiece 8 passes through the annular region 43 of the stepped portion formation area. Here, the annular region is where the gear-shaped teeth of the stepped portion 42 in Figure 7 are located. A detailed explanation follows below. Figure 4 shows the trajectory of the outer peripheral point d on the polishing surface 41 of the workpiece 8 during polishing. The trajectory of the outer peripheral point d of the workpiece 8 during polishing is concentrated near the center and on the outer peripheral part of the polishing surface 41 of the polishing layer 4. The outer peripheral part of the workpiece 8 where overpolishing occurs is the inner part along the outer circumference of the workpiece 8, for example, the part from the outer circumference of the workpiece 8 inward by a length of 1 / 5 to 1 / 100 of the radius. Figure 5 is a schematic diagram of the trajectory of the outer circumference of the workpiece 8. From Figure 5, the areas where the trajectory of the outer circumference of the workpiece 8 is concentrated are near the center of the polished surface 41 of the polishing layer 4 and on the outer circumference of the polished surface 41. The area near the center of the polished surface 41 is the circular stepped portion forming region 43 (a region where a circular portion and a tooth portion are formed as a stepped portion) drawn at the center of the polishing layer 4 in Figure 6. Figure 7 illustrates the polishing layer 4 with a stepped portion 42 in which a tooth portion 421 is formed in the annular region. Figure 7 shows the outer circumference of the workpiece 8 passing through the annular region. Note that the units of the vertical and horizontal axis values ​​in Figures 4 to 6 are millimeters, and the outer peripheral region of the workpiece 8 is assumed to have a radius of 135 mm or more and 150 mm or less. Furthermore, the stepped region 43 with diameter D in Figure 6 is a circular region centered on the center point of the polished layer 4, with a radius of 0.2 or less relative to the radius of the polished layer 4.

[0017] Furthermore, the stepped portion forming region 43 is composed of a circular region 43A centered at the center point of the polishing layer 4 and having a radius of 0 or more and less than 0.2 relative to the radius of the polishing layer 4, and an annular region 43B centered at the center point of the polishing layer 4 and having a radius of 0.1 or more and 0.2 relative to the radius of the polishing layer 4, excluding the circular region 43A. The annular region 43B is donut-shaped. The circular region 43A has a stepped portion of the circular part 422, and the annular region 43B has a toothed portion 421. For example, Figures 9 and 10 show examples of stepped portions formed in the stepped portion formation region 43.

[0018] (Stepped section) As shown in Figure 7, the polishing layer 4 of the polishing pad 3 has a stepped portion 42 that has a gear-like shape centered on the center point of the polishing layer 4. The stepped portion 42 is composed of a circular portion 422 and a toothed portion 421. The stepped portion 42 refers to a recess formed to reduce the area of ​​the polished surface 41 near the center where there is frequent contact with the outer circumference of the workpiece 8. As explained using Figures 4 to 6, the trajectories of the outer circumference of the workpiece 8 are concentrated near the center and on the outer circumference of the polishing surface 41 of the polishing layer 4. Overpolishing of the outer circumference of the workpiece 8 can be suppressed by reducing the area of ​​the polishing surface 41 that frequently comes into contact with the outer circumference of the workpiece. However, the density of trajectories is very high on the outer circumference of the polishing layer 4, making it impossible to create a stepped section over the entire outer circumference of the polishing layer 4. Furthermore, creating a stepped section on only a part of the outer circumference of the polishing layer 4 is time-consuming. Although the density of trajectories is high near the center of the polishing layer 4, it is lower than that of the outer circumference of the polishing layer 4. Therefore, it is possible to create a stepped section over the entire area near the center of the polishing layer, which shortens processing time compared to creating a stepped section on the outer circumference of the polishing layer and suppresses overpolishing of the outer circumference of the workpiece.

[0019] Figure 8 is a cross-sectional view of the polishing pad and the workpiece during polishing. As shown in Figure 8, in the stepped portion 42, the angle α between the side wall 42s connecting the polishing surface 41 and the bottom surface 42b of the stepped portion 42, and the extension surface 42c of the bottom surface 42b of the stepped portion 42 in the direction of the side wall, is preferably 60 degrees or more and 90 degrees or less. More preferably 75 degrees or more and 90 degrees or less. If the angle α is less than 60 degrees, the polishing surface 41 that comes into contact with the outer circumference of the workpiece 8 increases as polishing progresses, so the polishing performance changes. If it exceeds 90 degrees, the width of the stepped portion formed on the polishing surface 41 becomes smaller than the width of the bottom surface 42b, and the difference becomes larger, making processing difficult. The angle α between the side wall 42s and the extension surface 42c of the bottom surface 42b of the stepped portion 42 in the direction of the side wall is preferably 60 degrees or more and 90 degrees or less, forming a steeply inclined step. Even as polishing progresses and the thickness of the polished layer decreases, the increase in the polished surface is small compared to the decrease in thickness, and the step is maintained. Therefore, the area of ​​the polished surface 41 of the polished layer 4 reduced by the stepped portion 42 does not change much, and thus the polishing performance does not change. Furthermore, the depth of the stepped portion 42 is smaller than the thickness of the polished layer 4 in the portion other than the stepped portion.

[0020] Because a stepped portion 42 is formed in the region near the center of the polishing layer 4, the stepped portion 42 acts as a slurry reservoir, and by providing a groove connected to the stepped portion 42, the slurry 9 can be supplied evenly to the entire polishing layer 4 by centrifugal force.

[0021] The shape of the tooth portion 421, as viewed from the direction perpendicular to the polished surface, is not particularly limited, but examples include semicircular, half-oval, fan-shaped, and trapezoidal shapes. Half-oval refers to a semi-ellipse.

[0022] When viewed from a direction perpendicular to the polished surface, the total area of ​​the teeth 421 is preferably in an area ratio of 0.2 or more and less than 1.0 to the area of ​​the annular region 43B, and more preferably 0.4 or more and 0.9 or less. The polishing pad 3 of the present invention can adjust the degree of suppression of over-polishing by changing the shape of the stepped portion 42 formed in the polishing layer 4 according to the proportion of over-polishing of the outer circumference of the workpiece 8 when polished with a conventional polishing pad, and by adjusting the total area of ​​the openings of the stepped portion 42 in the annular region 43. Variations in shape include those shown in Figures 9 and 10, and the proportion of the stepped portion area in the annular region increases from Figure 9 to Figure 10.

[0023] The stepped portion 42 is not particularly limited, but is preferably formed by counterboring. Counterboring is a cutting process that creates a recess (counterbore) of a specific shape on the surface of a part. A circular end mill can be used for counterboring.

[0024] The polishing layer 4 may have a circular through-hole centered on the center point of the polishing layer and a stepped portion formed in contact with the central hole. Having a central hole in the polishing layer 4 makes it applicable to double-sided polishing devices. A double-sided polishing device polishes both sides of a workpiece simultaneously and comprises a pair of polishing plates that rotate around a rotation axis, a polishing pad fixed to the polishing surface side of the polishing plates, and a carrier for holding the workpiece, with the workpiece placed in a hole provided in the carrier. The double-sided polishing device supplies polishing slurry to the polishing surface of the polishing pad from a polishing slurry supply device, while rotating the upper and lower polishing plates in opposite directions by gears inside the polishing device via a shaft passing through the center, thereby flattening the workpiece held by the carrier that is in contact with the polishing surface of the polishing pad.

[0025] The polishing layer 4 may preferably form a plurality of outer peripheral steps along the outer circumference of the polishing surface 41. Forming a stepped section along the outer perimeter means that, similar to how trees are planted along a road, a stepped section is formed along the outer perimeter. As described above, the areas where the trajectories of the outer circumference of the workpiece 8 are concentrated are near the center and outer circumference of the polished surface 41 of the polishing layer 4. Therefore, if multiple outer-circumferential steps are formed along the outer circumference of the polished surface 41, over-polishing of the workpiece 8 can be further suppressed. When an outer-circumferential step is formed, the step having a gear-like shape centered on the center point of the polishing layer 4, or the step formed to be in contact with a circular through-hole centered on the center point of the polishing layer 4, is also referred to as the inner step.

[0026] (Grooving, Embossing) It is preferable to provide grooves or embossing on the polished surface 41 of the polishing layer 4. 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 both slurry discharge grooves and slurry holding grooves may be present. Examples of slurry discharge grooves include grid grooves and radial grooves, and examples of slurry holding grooves include concentric grooves and perforations (through holes), and these can also be combined. In low-pressure grinding, the grinding plate 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 forms in layers between the grinding surface 41 and the processed surface, hindering the grinding process. This phenomenon can be suppressed by grooving or embossing the grinding surface 41. This also facilitates the discharge of grinding debris and the movement of the grinding fluid. Furthermore, in order to improve the flatness of the polished layer 4, surface grinding treatments such as buffing may be applied to the polished surface 41 side or the side opposite to the polished surface of the polished layer 4.

[0027] (composition) The materials constituting the polishing layer 4 are not particularly limited, and conventionally used materials can be used. For example, polyurethane resin, polyurea resin, and polyurethane-polyurea resin can be used, and polyurethane resin is preferred. Specific main component materials include, for example, materials obtained by reacting an isocyanate-terminated prepolymer with a curing agent. The polishing layer 4 is formed by pouring a mixture of isocyanate-terminated prepolymer and a curing agent (chain extender) into a mold, curing the resulting foam, and then slicing the foam. In other words, the polishing layer 4 is dry-molded. The polishing layer 4 may contain dispersed hollow microspheres (foam), or it may not contain hollow microspheres, but it is preferable that it contains dispersed hollow microspheres.

[0028] The polishing layer 4 is preferably made of a polyurethane resin sheet having closed cells.

[0029] The hollow microspheres formed inside the polishing layer 4 are not particularly limited, but are preferably spherical, elliptical, or close to these shapes. Examples include pre-expanded types and unexpanded heat-expandable microspheres that have been heated and expanded. Since the polishing layer 4 is formed from slices of foam, some or all of the hollow microspheres may be open on the polishing surface 41. The average diameter of the openings formed on the polishing surface 41 is adjusted to be in the range of 5 to 100 μm.

[0030] The size (diameter) of the polishing layer 4 is the same as that of the polishing pad 3, and can be approximately 10 cm to 2 mm in diameter, and the thickness of the polishing layer 4 can be approximately 1 to 5 mm.

[0031] <<Manufacturing method for polishing pads>> The method for manufacturing the polishing pad 3 of the present invention will be described below.

[0032] <Method for manufacturing the polished layer> (Material of the polishing layer) The material for the polishing layer 4 is not particularly limited, but for example, polyurethane resin, polyurea resin, and polyurethane-polyurea resin are preferred as the main component, with polyurethane resin being more preferred.

[0033] The manufacturing method for the abrasive layer 4 will be explained below using an example that utilizes an isocyanate-terminated prepolymer and a curing agent.

[0034] A method for producing the polishing layer 4 using an isocyanate-terminated prepolymer and a curing agent includes, for example, a material preparation step of preparing at least an isocyanate-terminated prepolymer and a curing agent; a mixing step of mixing at least the isocyanate-terminated prepolymer and curing agent to obtain a mixed liquid for molding a molded body; a curing step of molding the polishing layer 4 from the mixed liquid for molding a molded body, a groove machining step, and a counterboring step of forming a stepped portion 42.

[0035] The following will explain each of the following processes: material preparation, mixing, molding, grooving, and counterboring.

[0036] (Material preparation process) For the production of the polishing layer 4 of the present invention, an isocyanate-terminated prepolymer and a curing agent are prepared as raw materials for a polyurethane resin molded article (cured resin). Here, the isocyanate-terminated prepolymer is a urethane prepolymer (sometimes simply called a prepolymer) for forming a polyurethane resin molded article. When the polishing layer 4 is to be made into a polyurea resin molded article or a polyurethane polyurea resin molded article, the appropriate prepolymer is used. The isocyanate-terminated 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. Other components may also be included in the isocyanate-terminated prepolymer. As the isocyanate-terminated prepolymer, commercially available products may be used, or those 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 under a nitrogen atmosphere, raising the temperature to 80°C after 30 minutes, and then reacting at 80°C for another 60 minutes. 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. In this specification, a polyol compound means a compound having two or more hydroxyl groups (OH) in its molecule. Polyol compounds used as raw materials for prepolymers are not particularly limited, but examples include diol compounds such as ethylene glycol, diethylene glycol (DEG), and butylene glycol; triol compounds; polyether polyol compounds such as poly(oxytetramethylene) glycol (or polytetramethylene ether glycol) (PTMG), polypropylene glycol (PPG), and polyether polycarbonate diol (PEPCD); and polyester polyols. The curing agent is not particularly limited, but examples 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-(isopropyl Polyhydric amine compounds such as [diamino)-4-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 glyco 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, Examples of polyhydric alcohol compounds include 3-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). In addition to the components listed above, additives such as oxidizing agents may be added to the abrasive layer 4 as needed.

[0037] The polishing layer 4 can be formed by using hollow microspheres, which have an outer shell and a hollow interior, as a material, if necessary. Commercially available materials may be used for the hollow microspheres, or materials may be obtained by synthesis using conventional methods. The material of the outer shell of the hollow microspheres 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 organosilicone resins, as well as copolymers obtained by combining two or more monomers that constitute these resins (e.g., acrylonitrile-vinylidene chloride copolymer). 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.). The gas contained in the hollow microspheres is not particularly limited, but examples include hydrocarbons, specifically isobutane. In addition to the above components, conventionally used blowing agents may be used in combination with the hollow microspheres, and gases that are unreactive to each of the above components may be blown in during the mixing process described below.

[0038] (Mixing process) In the mixing step, the isocyanate-terminated prepolymer and curing agent obtained in the material preparation step are supplied to the 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.

[0039] (molding process) In the molding process, the mixed liquid for molding the molded body prepared in the mixing process is poured into a 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 isocyanate-terminated prepolymer and curing agent react to form the polyurethane resin, causing the mixed liquid to harden.

[0040] 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.

[0041] 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 height of 50 mm, for example, approximately 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 approximately 30 mm of the central part. In the hardening molding step, a foam is obtained in which hollow microspheres are formed almost uniformly inside.

[0042] (Groove machining process) Grooves are formed on the polished surface 41 of the obtained polished layer 4. By performing cutting or other machining on the polished surface 41 using the required cutting tool, grooves with any pitch, width, and depth can be formed.

[0043] (Counterboring process) The resulting polished layer 4 is counterbored to form a stepped portion 42. While there are no particular limitations on the counterbore process, a circular end mill can be used.

[0044] 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.

[0045] <Method for manufacturing the base layer> The material of the base layer 6 is not particularly limited, but examples include impregnated materials obtained by impregnating a base material such as a nonwoven or woven fabric made of polyethylene, polyester, or other fibers with a resin solution such as urethane; suede materials using resin materials such as urethane; and sponge materials using materials such as urethane. In the present invention, known materials can be used for the base layer 6, and known manufacturing methods can also be used. The base layer 6 may be subjected to surface treatments such as buffing or grooving on the surface facing the polishing layer 4 and / or the surface opposite to the polishing layer 4.

[0046] <Joining process> In the bonding process, the formed polishing layer 4 and base layer 6 are bonded together with an adhesive layer. The adhesive layer is usually composed of double-sided tape or adhesive. For example, the double-sided tape or adhesive can be one known in the art (e.g., adhesive sheet). The polishing layer 4 and base layer 6 are bonded together with the adhesive layer. The adhesive layer can be formed with 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. The surface of the polishing layer 4 opposite to the polishing surface 41 and the surface of the base layer 6 are pressed together via double-sided tape, and the polishing layer 4 and base layer 6 are bonded together with the adhesive layer. 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]

[0047] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0048] In each example and comparative example, unless otherwise specified, "parts" means "parts by mass."

[0049] 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)]".

[0050] (Regarding the polished layer) 70 parts of an isocyanate-terminated urethane prepolymer with an NCO equivalent of 420, obtained by reacting 2,4-tolylene diisocyanate (TDI), poly(oxytetramethylene) glycol (PTMG) with a number average molecular weight of 650, poly(oxytetramethylene) glycol (PTMG) with a number average molecular weight of 850, and diethylene glycol (DEG), and 30 parts of an isocyanate-terminated urethane prepolymer with an NCO equivalent of 600, obtained by reacting 2,4-tolylene diisocyanate (TDI), a polyester polyol (number average molecular weight of 2000) obtained by synthesizing adipic acid and 1,4-butanediol, and diethylene glycol (DEG), were mixed with 1.2 parts of unexpanded hollow microspheres, the shell of which is made of acrylonitrile-vinylidene chloride copolymer and containing isobutane gas within the shell, to obtain a mixture. The obtained mixture was placed in the first liquid tank and kept warm. Next, 25.8 parts of MOCA were added as a curing agent separately from the first liquid, and the mixture was 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. After injecting the two injected liquids into a preheated mold of a molding machine while mixing and stirring, the mold was clamped and 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 polyurethane resin molded product. After the obtained polyurethane resin molded product was allowed to cool to 25°C, it was heated again in an oven at 120°C for 5 hours and then sliced ​​to a thickness of 1.6 mm to obtain polished layer 4. The radius of the manufactured polished layer 4 was 370 mm. The density of the polishing layer 4 is 1.0 g / cm³. 3 The Shore D hardness was 60. The density of polishing layer 4 was measured in accordance with Japanese Industrial Standards (JIS K 6505), and the Shore D hardness of polishing layer 4 was determined in accordance with Japanese Industrial Standards (JIS K 7215) from the depth of indentation of an indenter pressed against the surface of the test piece via a spring. Here, the measurement sample was obtained by stacking multiple polishing layers as needed, so that the total thickness was at least 4.5 mm.

[0051] (Regarding groove machining) Concentric grooves with a width of 0.4 mm and a depth of 0.8 mm were made in the polished layer 4 obtained above, with a pitch of 1.7 mm. Sixteen radial grooves, each 1.5 mm wide and 0.8 mm deep, were provided.

[0052] (Regarding counterbore machining) Using a circular end mill with a diameter of 30 mm, a circular stepped portion 42 with a diameter of 115 mm was formed on the grooved polishing layer 4, such that the centers of the polishing pads coincided. The circular end mill was then moved radially from the center of the circular stepped portion, forming eight equally spaced stepped portions that protruded from the outer circumference of the circular stepped portion by the radius distance of the circular end mill, thereby forming a gear-shaped stepped portion 42 (polished layer 4A). The angle α between the side wall 42s of the stepped portion 42 and the extension surface 42c of the bottom surface 42b of the stepped portion 42 in the direction of the side wall was 90°, and the depth of the stepped portion 42 was 1.0 mm. The ratio of the stepped portion area to the area of ​​the annular region of the formed stepped portion was 0.5. Using a circular end mill with a diameter of 30 mm, a circular stepped portion 42 with a diameter of 115 mm was formed on the grooved polishing layer 4, such that the centers of the polishing pads coincided. The circular end mill was then moved radially from the center of the circular stepped portion, forming 16 stepped portions at equal intervals on the outer circumference of the circular stepped portion, each protruding from the outer circumference by the radius distance of the circular end mill, thereby forming a gear-shaped stepped portion 42 (polished layer 4B). The angle α between the side wall 42s of the stepped portion 42 and the extension surface 42c of the bottom surface 42b of the stepped portion 42 in the direction of the side wall was 90°, and the depth of the stepped portion 42 was 1.0 mm. The ratio of the stepped portion area to the area of ​​the annular region of the formed stepped portion was 0.9.

[0053] (Examples and Comparative Examples) Polishing pads A and B (Examples 1 and 2) were manufactured by joining polishing layers 4A and 4B, obtained by the counterbore process described above, with a base layer made of commercially available foamed polyurethane foam (Sekisui Sponge 2504KMS, manufactured by Sekisui Chemical Co., Ltd., 1.2 mm thick) using 0.1 mm thick double-sided tape (a PET base material with adhesive layers made of acrylic resin on both sides). Polishing pads C (Comparative Example 1) were manufactured by attaching the double-sided tape to the opposite side of the base layer and adhesive layer. Polishing pad C (Comparative Example 1) was manufactured in the same manner using an polishing layer that had not been counterbore. The diameter of the manufactured polishing pads was 740 mm.

[0054] (Polishing test) Polishing was performed using the polishing pads of each example and comparative example under the following polishing conditions. The polishing rate was measured at 121 points in diameter during the polishing process. The results are summarized in Table 1. From Table 1, it can be seen that when polishing was performed using polishing pads A and B of Examples 1 and 2, overpolishing at the outer periphery of the workpiece 8 was suppressed compared to polishing pad C of Comparative Example 1. In the table, "○" indicates that the polishing rate from 135 to 150 mm from the center of the 300 mm diameter workpiece 8 is equivalent to the polishing rate from the center of the 8 layers of the workpiece 8 to 135 mm, indicating that overpolishing at the outer periphery of the workpiece 8 is suppressed. "×" indicates that the polishing rate from 135 to 150 mm from the center of the workpiece 8 is greater than the polishing rate from the center of the 8 layers to 135 mm, indicating that overpolishing at the outer periphery of the workpiece 8 is not suppressed.

[0055] [Table 1]

[0056] (polishing conditions) Polishing machine: F-REX300X (manufactured by Ebara Corporation) Disk: A188 (manufactured by 3M) Retainer ring: Retainer ring GXKD (manufactured by Ebara Corporation) Rotation speed: (Surface plate) 90 rpm, (Grinding head) 81 rpm Polishing pressure: 1.7 psi Abrasive temperature: 20℃ Abrasive discharge rate: 200 ml / min Abrasive: (Use a mixture of CES-5003-2.5 concentrate and pure water in a weight ratio of 1:3) (Manufactured by AGC Inc.) Object to be polished: TEOS film substrate (diameter 300mm) Polishing time: 60 seconds Pad Break: 32N 30 minutes Conditioning: Ex-situ 32N, 4 scans

[0057] From the polished layer 4 obtained in the above embodiment, a counterbore polished layer 4C, as shown in Figures 11 and 12 (cross-sectional view along X-X in Figure 11), was manufactured. First, in a circular polishing layer 4 with a diameter of 1345 mm, a grid-like groove 11d with a width of 2.0 mm, a depth of d0.35 mm, and a groove pitch of 30 mm was provided on the polishing surface 41, and a central hole 421 with a diameter of 440 mm was provided centered at the center point of the polishing layer 4. From the central hole 421 of the grooved polishing layer 4 toward the outer edge, eight inner counterbores were machined at 45° intervals with a circular end mill with a diameter of 25 mm, relative to the center point of the polishing layer 4. These counterbores formed an inner stepped portion 42A with a depth of 0.35 mm and a radius of 71 mm, in contact with the central hole 421. Furthermore, 24 outer counterbores were machined from the outer edge toward the center point, relative to the center point of the polishing layer 4, at 15° intervals. These counterbores formed an outer stepped portion 42B with a depth of 0.35 mm and a radius of 71 mm, in contact with the outer edge. The resulting polishing layer is designated as polishing layer 4C. Furthermore, the depth of the inner stepped portion 42A and the outer stepped portion 42B from the polished surface 41 is the same as the depth of the groove 11d. Furthermore, the angle α between the side walls of the inner stepped portion 42A and the outer stepped portion 42B and the surface extending the bottom surfaces of the stepped portions 42A and 42B in the direction of the side walls was 90 degrees.

[0058] Except for not performing the outer counterboring process, polished layer 4D was manufactured using the same process as polished layer 4C (see Figure 13). Note that in Figures 12 and 13, the number of grooves 11d is shown in a reduced number for easier understanding. [Industrial applicability]

[0059] This invention provides a polishing pad with a long polishing life while suppressing over-polishing on the outer periphery of the workpiece, and therefore contributes to the manufacture and sale of polishing pads, thus having industrial applicability.

[0060] 1 Polishing equipment 3. Polishing pads 4 Polishing layer 41 Polished surface 42 Stepped section 42s Step side wall 42b Bottom of step part 42c Extension surface of the bottom of the stepped section in the direction of the side wall of the stepped section 421 Tooth portion (part of the stepped portion) 422 Circular section (part of the stepped section) 43 Stepped area 43A Circle Region 43B Circular Region 5 Retainer Rings 6 Base material layer 8 Object to be polished 9. Slurry 10. Polishing plate 16. Holding plate

Claims

1. A polishing pad including a circular polishing layer, The polishing layer comprises a stepped portion having a gear-like shape centered on the central point of the polishing layer, A polishing pad in which the side wall of the stepped portion is at an angle of 60 degrees or more and 90 degrees or less with respect to the surface of the bottom of the stepped portion that extends in the direction of the side wall of the stepped portion.

2. The stepped portion is formed within a stepped portion forming region, which is a circular region centered on the central point of the polishing layer and having a radius of 0.2 or less relative to the radius of the polishing layer. The stepped portion forming region is composed of a circular region centered on the center point of the polishing layer and having a radius of 0 or more and less than 0.2 relative to the radius of the polishing layer, and an annular region centered on the center point of the polishing layer and having a radius of 0.1 or more and 0.2 or less relative to the radius of the polishing layer, with the circular region removed from the circle. The polishing pad according to claim 1, wherein a circular stepped portion is arranged in the circular region, and a gear-shaped stepped portion is arranged in the annular region.

3. The polishing pad according to claim 2, wherein the total area of ​​the stepped portion of the tooth shape in the annular region is 0.2 or more and less than 1.0 in area ratio with respect to the entire area of ​​the annular region.

4. The polishing pad according to claim 1, wherein the polishing layer is made of a polyurethane resin sheet having closed cells.

5. The polishing pad according to claim 2, wherein the outer circumference of the workpiece being polished passes through the annular region when the workpiece is closest to the center point during polishing.

6. The polishing pad according to claim 1, wherein a plurality of outer peripheral stepped portions are formed along the outer circumference of the polishing surface in the polishing layer.

7. The polishing pad according to claim 1, wherein the height of the step portion is smaller than the thickness of the polishing layer.

8. A method for manufacturing an abrasive pad according to claim 1, A manufacturing method wherein the aforementioned multiple stepped portions are formed by counterboring.

9. A polishing pad including an abrasive layer, The polishing layer has a circular through-hole centered on the center point of the polishing layer, A stepped portion formed so as to be in contact with the central hole, A polishing pad equipped with the following features.

10. The polishing pad according to claim 9, further comprising an outer peripheral step portion in contact with the outer periphery of the polishing surface in the polishing layer.

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