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 that reduces the contact area with the outer periphery of the workpiece by forming multiple stepped sections on the outer periphery of the polishing layer, thereby suppressing over-polishing of the outer periphery of the workpiece.

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] Generally, 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, slurry) containing abrasive grains is supplied between a polishing pad and the wafer, and they are relatively slid while being pressed, and the surface of the wafer is flattened 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 is provided with a polishing pad 3. The polishing pad 3 abuts on 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 performing polishing and a base material layer 6 that supports the polishing layer 4. The polishing pad 3 is rotationally driven in a state where the workpiece 8 is pressed, and polishes the workpiece 8. At that time, 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 the CMP method as described above, it is known that polishing unevenness occurs if the relative pressing between the workpiece and the polishing pad is not uniform. In particular, the pressing at the outer peripheral portion of the workpiece tends to be non-uniform, and there is a problem that only the outer peripheral portion of the workpiece is over-polished. The outer peripheral portion of the workpiece refers to the portion between a circle with a radius of, for example, 0.9 and the outer periphery when the center point of the workpiece is the center and the radius of the workpiece is 1.

[0005] Patent Document 1 discloses a polishing pad that suppresses over-polishing of the outer periphery of the workpiece by reducing the thickness of the polishing layer at the outer periphery. However, as shown in Figure 10, the polishing pad described in Patent Document 1 has a polishing layer 4c thickness j that gradually decreases towards the outer edge (it has a gentle slope). Before polishing progresses, the outer edge of the workpiece 8 does not come into contact with the polishing surface 41c in areas where the thickness is less than j. However, as polishing progresses and the thickness j of the polishing layer 4c decreases overall to a thickness j', the areas that were smaller than j and larger than j' become flat. As a result, the outer edge of the workpiece 8 comes into contact with the polishing surface 41c in those areas as well, making it impossible to suppress over-polishing of the outer edge of the workpiece 8 (resulting in a short polishing life). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2008-279553 [Overview of the project] [Problems that the invention aims to solve]

[0007] 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]

[0008] As a result of their research, the inventors have found a polishing pad in which multiple stepped portions are formed on the outer periphery of the polishing layer, thereby reducing the contact area with the outer periphery of the workpiece and suppressing over-polishing of the outer periphery of the workpiece. The present invention encompasses the following: [1] A polishing pad having a polishing layer having a polishing surface for polishing an object to be polished, A polishing pad in which a plurality of stepped portions are formed in the polishing layer along the outer circumference of the polishing surface. [2] The polishing pad according to [1], wherein the side wall connecting the polishing surface and the bottom surface 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 in the direction of the side wall. [3] The polishing pad according to [1] or [2], wherein the polishing surface is provided with connecting grooves that connect the multiple stepped portions. [4] The polishing pad according to any one of [1] to [3], wherein the height of the step portion is greater than the depth of the connecting groove. [5] The polishing pad according to any one of [1] to [3], wherein the height of the step portion is the same as the depth of the connecting groove. [6] The polishing pad according to any one of [1] to [5], wherein the shape of the stepped portion when viewed from a direction perpendicular to the polishing surface is such that the width of the stepped portion in contact with the outer circumference of the polishing surface narrows towards the center of the polishing surface. [7] The polishing pad according to any one of [1] to [6], wherein the stepped portion is fan-shaped or half-oval when viewed from a direction perpendicular to the polishing surface. [8] The polishing pad according to any one of [1] to [7], wherein the polishing layer has an inner step portion formed on the center point of the polishing layer. [9] The polishing pad according to any one of [1] to [8], wherein the polishing layer has a circular through-hole centered on the central point of the polishing layer, and an inner stepped portion is formed so as to be in contact with the central hole. A method for manufacturing an abrasive pad as described in any one of [1] to [9], A manufacturing method wherein the aforementioned multiple stepped portions are formed by counterboring. [Effects of the Invention]

[0009] By forming multiple stepped sections on the outer periphery 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 these stepped sections 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]

[0010] [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 is a schematic diagram of a cross-section perpendicular to the polishing surface, showing the state of the area near the outer circumference of the workpiece at the stepped portion during polishing in the polishing pad of the present invention. [Figure 5] Figure 5 is a schematic diagram of a polishing pad according to one embodiment of the present invention, in which the stepped portion is fan-shaped when viewed from a direction perpendicular to the polishing surface. [Figure 6] Figure 6 is a schematic cross-sectional view perpendicular to the polishing surface near the outer periphery of the polishing layer, showing the relationship between the depth d of the groove formed on the polishing surface of the polishing pad of the present invention and the step height e of the stepped portion. [Figure 7] Figure 7 is a schematic diagram of a polishing pad according to one embodiment of the present invention, in which the stepped portion is half-oval when viewed from a direction perpendicular to the polishing surface (double arrow l: width of the stepped portion). The connecting groove 11b and radial groove 11r formed on the polishing surface are also shown. [Figure 8] Figure 8 shows the mechanism for discharging polishing debris through grooves connecting stepped sections (arrow k: direction of rotation of the polishing pad, arrow h: direction of slurry discharge, dashed arrow i: discharge of polishing debris). [Figure 9] Figure 9 is a schematic cross-sectional view of the area near the outer periphery of the polishing layer in the polishing pad of the present invention before and after polishing. [Figure 10] Figure 10 is a schematic cross-sectional view of the area near the outer edge of the polishing layer before and after polishing, in a polishing pad described in Patent Document 1, in which the thickness of the outer edge of the polishing layer gradually decreases. [Figure 11] FIG. 11 is a schematic view of the polishing layer 4C obtained in the embodiment. [Figure 12] FIG. 12 is a schematic cross-sectional view taken along the line X-X of the polishing layer 4C.

MODE FOR CARRYING OUT THE INVENTION

[0011] Hereinafter, embodiments for carrying out the invention will be described, but the present invention is not limited to the embodiments for carrying out the invention.

[0012] <<Polishing Pad>> The structure of the polishing pad 3 will be described. The polishing pad 3 includes a polishing layer 4 and a base material layer 6. The shape of the polishing pad 3 is preferably a disk shape, but is not particularly limited, and the size (diameter) can also be appropriately determined according to the size of the polishing apparatus 1 provided with the polishing pad 3. 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.

[0013] Here, over-polishing of the outer peripheral portion of the workpiece will be described with reference to FIGS. 2 and 3. In CMP polishing, polishing is performed while pressing the workpiece against the polishing pad. At this time, as shown in FIG. 2, since the polishing layer near the outer periphery of the workpiece 8 is deformed by the retainer ring 5, excessive pressure acts on the outer peripheral portion of the workpiece 8, and over-polishing is likely to occur (arrow a: direction of excessive pressure, arrow b: direction of polishing pressure and direction of repulsive force against the polishing pressure). In addition, as shown in FIG. 3, due to the influence of centrifugal force, the slurry 9 is likely to gather near the outer periphery of the workpiece 8, so over-polishing of the outer peripheral portion of the workpiece 8 is likely to occur (arrow c: direction of centrifugal force). Furthermore, the polishing trajectory of the outer periphery of the workpiece 8 is concentrated near the center and on the outer periphery of the polished surface of the polishing layer 4. Therefore, by reducing the area of ​​the outer periphery of the polished surface, over-polishing of the outer periphery of the workpiece can be suppressed.

[0014] <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.

[0015] (Stepped section) As shown in Figure 5, the polishing layer 4 of the polishing pad 3 has multiple stepped portions 42 formed along the outer circumference of the polishing surface 41. To be formed along the perimeter means that, similar to how trees are planted along a road, the formation continues in a parallel manner along the perimeter. The stepped portion 42 refers to a recess formed in the polishing layer 4, as shown in Figure 4, in order to reduce the area of ​​the polished surface 41. Since multiple stepped portions 42 are formed along the outer circumference of the polished surface 41, the area of ​​the outer circumference of the polished surface 41 is reduced, and the discharge of slurry 9 is also promoted, thereby suppressing over-polishing of the outer circumference of the workpiece.

[0016] The polishing pad 3 of the present invention can optimize the suppression of over-polishing by changing the number of stepped portions 42 formed in the polishing layer 4 according to the degree of over-polishing of the outer periphery relative to the central portion. For example, if the outer periphery is 20% over-polished relative to the central portion, over-polishing can be suppressed by reducing the area of ​​the outer periphery of the polishing surface 41 by approximately 20%. This 20% area reduction is achieved by changing the number of stepped portions 42 so as to reduce the area of ​​the outer periphery of the polishing surface 41 by 20% without changing the area of ​​a single stepped portion 42. In Figure 5, 11b is a connecting groove, and 11r is a radial groove.

[0017] Referring to Figure 4, in the stepped portion 42, the angle α between the side wall 42s connecting the polished surface 41 and the bottom surface 42b of the stepped portion 42, and the surface 42c extending the bottom surface 42b of the stepped portion 42 in the direction of the side wall 42s, is not particularly limited, but is preferably 60 degrees or more and 90 degrees or less (see Figure 4). More preferably, it is 75 degrees or more and 90 degrees or less. If the angle α is less than 60 degrees, the polished surface 41 that comes into contact with the outer circumference of the workpiece 8 increases as polishing progresses, and the polishing performance changes. The angle α between the side wall 42s and the surface 42c extending the bottom surface 42b of the stepped portion 42 in the direction of the side wall 42s is preferably 60 degrees or more and 90 degrees or less, forming a step with a large incline. 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. As a result, the area of ​​the polished surface 41 on the outer periphery of the polished layer, which is reduced by the stepped portion 42, does not change much, and therefore the polishing performance does not change. To explain using Figure 9, since the angle α between the side wall 42s and the surface 42c extending the bottom surface 42b of the stepped portion 42 in the direction of the side wall 42s is preferably 60 degrees or more and 90 degrees or less, even as polishing progresses and the thickness j of the polished layer 4 decreases overall to a thickness j', the distance between the outer periphery of the polished layer 4 and the side wall 42s of the stepped portion 42 does not change much, and therefore the area of ​​the stepped portion 42 also does not change much.

[0018] The shape of the stepped portion 42 when viewed from a direction perpendicular to the polished surface 41 is not particularly limited, but is preferably a fan shape as shown in Figure 5 or a half-oval shape as shown in Figure 7. Half-oval refers to a semi-ellipse. It is preferable that the shape of the stepped portion 42, such as a fan shape or a half-oval shape, is such that the width of the stepped portion in contact with the outer circumference of the polished surface narrows towards the center of the polished surface. As shown in Figure 5, the sector-shaped stepped portion 42 has a central angle β. By changing the angle of the central angle β, the area of ​​the sector-shaped stepped portion 42 can be changed, and the contact area with the outer circumference of the workpiece 8 can be changed. As shown in Figure 6, the length g of the stepped portion 42 is the distance from the outer circumference of the polished layer 4 to the point closest to the center point cut off by the formation of the stepped portion 42. As shown in Figure 6, it is preferable that the length g of the stepped portion 42 is 2.5 times or more the length f of the portion that does not come into contact with the polishing surface when the workpiece 8 is located closest to the outer circumference (the distance between a circle centered at the center point of the workpiece 8 and having a radius 0.9 times the radius of the workpiece 8, and the outer circumference of the workpiece 8, where (1-0.9) × (radius of the workpiece 8)).

[0019] The multiple stepped portions 42 are formed by counterboring, although not particularly limited. Counterboring is a cutting process that creates recesses (counterbores) of a specific shape on the surface of a part. While not particularly limited, an end mill can be used for counterboring.

[0020] (Grooving, Embossing) Preferably, the polishing surface 41 is provided with connecting grooves 11b that connect multiple stepped portions 42. As shown in Figure 8, the provision of connecting grooves 11b allows polishing debris accumulated in the grooves formed on the polishing surface 41 to be discharged from the connecting grooves 11b to the stepped portions 42 when the polishing surface 41 rotates in the direction of arrow k (arrow k: direction of rotation of the polishing pad, dashed arrow i: discharge of polishing debris), and also makes it easier for the debris to be discharged from the stepped portions 42 (arrow h: direction of slurry discharge), thereby suppressing the occurrence of scratches on the outer circumference of the workpiece 8. The cross-sectional shape of the connecting grooves 11b may be U-shaped, V-shaped, or semicircular. The pitch and width of the grooves are also not particularly limited. The depth (step height) e of the stepped portion 42 formed in the polishing layer 4 is preferably greater than the depth d of the connecting groove 11b. If the step height e is less than the depth d of the connecting groove 11b, there is a risk that polishing debris accumulating in the groove formed in the polishing surface 41 will not be easily discharged from the connecting groove 11b to the stepped portion 42. Figure 6 shows a schematic cross-sectional view perpendicular to the polished surface. The concentric groove 11c is shown in Figure 6, but the depth d of the connecting groove 11b and the depth d of the concentric groove 11c are the same, as can be understood from the method of manufacturing the polished layer in the embodiment described later.

[0021] As shown in Figures 5 and 7, the polished surface 41 of the polishing layer 4 is preferably provided with a plurality of radial grooves 11r. If the radial grooves 11r are connected to the stepped portion 42, there is a risk of excessive slurry discharge, but this is not particularly limited. The cross-sectional shape of the radial grooves 11r may be U-shaped, V-shaped, or semicircular. The pitch, width, and depth of the grooves are also not particularly limited. It is preferable to provide grooves or embossing on the polished surface 41 of the polishing layer 4 in addition to the connecting grooves 11b and radial grooves 11r. 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. As shown in Figures 11 and 12, the polished surface 41 of the polishing layer 4 may be provided with a grid-like groove 11d, and the depth (step height) e of the stepped portion 42 formed in the polishing layer 4 may be the same as the depth d of the groove 11d. 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.

[0022] (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 slicing a molded body that has been cured by pouring a mixture of isocyanate-terminated prepolymer and a curing agent (chain extender) into a mold. 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.

[0023] The hollow microspheres dispersed within 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. When the polishing layer 4 contains hollow microspheres, 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.

[0024] 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.

[0025] Preferably, the polishing layer 4 has an inner step formed in the region near the center of the polishing layer 4. The region near the center of the polishing layer 4 refers to the inside of the circle centered on the center point of the polishing layer 4. Since the density of the trajectories on the outer circumference of the workpiece 8 is relatively high near the center of the polishing layer 4, the formation of the inner step suppresses over-polishing of the outer circumference of the workpiece 8, and the inner step also acts as a slurry reservoir, allowing the slurry to be supplied uniformly to the entire polishing pad. Furthermore, the polishing layer 4 may have a circular through-hole centered at the center point of the polishing layer, and an inner step portion may be formed so as to be in contact with the central hole. The presence of 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 being 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. When an inner step is formed, the step formed along the outer circumference is also referred to as the outer circumference step.

[0026] <<Manufacturing method for polishing pads>> The method for manufacturing the polishing pad 3 of the present invention will be described below.

[0027] <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.

[0028] 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.

[0029] A method for manufacturing 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 molding step of molding the polishing layer 4 from the mixed liquid for molding a molded body; a grooving step of providing connecting grooves 11b and radial grooves 11r; and a counterboring step of forming stepped portions 42.

[0030] The following will explain each of the following processes: material preparation, mixing, molding, grooving, and counterboring.

[0031] (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 (hereinafter sometimes simply referred to as 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.

[0032] 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-mentioned components, conventionally used foaming agents may be used in combination with hollow microspheres, and non-reactive gases may be blown into each of the above components during the mixing process described below.

[0033] (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.

[0034] (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.

[0035] In the molding process, the mixed liquid is poured as needed and reacted within the mold to form a molded body. At this time, the prepolymer cross-links and hardens due to the reaction between the prepolymer and the curing agent.

[0036] 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 molded body formed with a mold height of 50 mm, for example, approximately 10 mm of the upper and lower parts of the molded body are not used due to scratches, etc., and 10 to 25 polishing layers 4 are formed from approximately 30 mm of the central part.

[0037] (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.

[0038] (Counterboring process) The resulting polished layer 4 is counterbored to form multiple stepped portions 42. While not particularly limited, an end mill can be used for the counterbore process.

[0039] 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.

[0040] <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.

[0041] <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, and its thickness can be set to about 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 or adhesive to bond the polishing layer 4 and base layer 6 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]

[0042] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0043] In each example and comparative example, unless otherwise specified, "parts" means "parts by mass."

[0044] 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)]".

[0045] (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 body, it was secondary cured in an oven at 110°C for 4 hours to obtain a polyurethane resin molded body. After the obtained polyurethane resin molded body was allowed to cool to 25°C, it was heated again in an oven at 120°C for 5 hours, then sliced ​​to a thickness of 1.6 mm to obtain polished layer 4.

[0046] The density of the polishing layer 4 is 1.0 g / cm³. 3 The Shore D hardness was 60. The methods for measuring density and Shore D hardness are as follows.

[0047] (density) Density of polishing layer 4 (g / cm³) 3 The measurements were taken in accordance with the Japanese Industrial Standard (JIS K 6505).

[0048] (Shore D hardness) The Shore D hardness of polished layer 4 was measured using a Shore D hardness tester in accordance with the Japanese Industrial Standard (JIS K 6253). Here, the sample to be measured was obtained by stacking multiple polished layers as needed, so that the total thickness was at least 4.5 mm.

[0049] (Regarding groove machining) Concentric grooves 11c with a width of 0.4 mm and a depth of d0.8 mm were made in the polished layer 4 obtained above, with a pitch of 1.7 mm. Sixteen radial grooves 11r, each 1.5 mm wide and 0.8 mm deep, were provided.

[0050] (Regarding counterbore machining) On the grooved polished layer 4, seven fan-shaped stepped portions 42, each with a length g of 37.5 mm, a central angle β of 50 degrees, and a depth e of 1.0 mm, were formed using a tapered end mill tapered at a 60-degree angle, so as not to connect to the radial grooves 11r, thereby forming the polished layer 4A. The angle α between the side wall 42s of the stepped portion 42 and the surface 42c extending from the bottom surface of the stepped portion 42 in the direction of the side wall 42s is 60 degrees. On the grooved polished layer 4, 32 half-oval stepped portions 42, each with a length g of 37.5 mm, a width of 25 mm, and a depth e of 1.0 mm, were formed using a circular end mill with a diameter of 25 mm, so as not to connect to the radial grooves 11r, thereby forming the polished layer 4B. The angle α between the side wall 42s of the stepped portion 42 and the surface 42c extending from the bottom surface of the stepped portion 42 in the direction of the side wall 42s is 90 degrees. The concentric grooves 11c provided on the outer periphery of the polishing layer 4 become connecting grooves 11b by the formation of a stepped portion 42.

[0051] (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 processing described above, with a base layer made of commercially available foamed urethane 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 A and B (Examples 1 and 2) were manufactured by attaching the double-sided tape to the opposite side of the base layer and the adhesive layer. Polishing pad C (Comparative Example 1) was manufactured in the same manner using an polishing layer that had not been counterbore.

[0052] (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, over-polishing of 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 workpiece 8 was equivalent to the polishing rate from the center to 135 mm, indicating that over-polishing of the outer periphery of the workpiece 8 was suppressed. × indicates that the polishing rate from 135 to 150 mm from the center of the workpiece 8 was significantly higher than the polishing rate from the center to 135 mm, indicating that over-polishing of the outer periphery of the workpiece 8 was not suppressed.

[0053] [Table 1]

[0054] (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.) Workpiece to be polished: TEOS film substrate (disc shape with a diameter of 300 mm) Polishing time: 60 seconds Pad Break: 32N 30 minutes Conditioning: Ex-situ 32N, 4 scans

[0055] 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. Note that in Figure 12, the number of grooves 11d is reduced in the diagram for easier understanding. [Industrial applicability]

[0056] 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.

[0057] 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 Surface extending the bottom surface of the stepped section toward the side wall. 5 Retainer Rings 6 Base material layer 8 Object to be polished 9. Slurry 10. Polishing plate 11b Connection groove 11r radial groove 11c concentric groove 11d lattice groove 16. Holding plate

Claims

1. A polishing pad comprising a polishing layer having a polishing surface for polishing an object to be polished, A polishing pad in which a plurality of stepped portions are formed in the polishing layer along the outer circumference of the polishing surface.

2. The polishing pad according to claim 1, wherein the side wall connecting the polishing surface and the bottom surface 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 in the direction of the side wall.

3. The polishing pad according to claim 1, wherein the polishing surface is provided with connecting grooves that connect the intervals between the plurality of stepped portions.

4. The polishing pad according to claim 3, wherein the height of the step portion is greater than the depth of the connecting groove.

5. The polishing pad according to claim 3, wherein the height of the step portion is the same as the depth of the connecting groove.

6. The polishing pad according to claim 1, wherein the shape of the stepped portion when viewed from a direction perpendicular to the polishing surface is such that the width of the stepped portion in contact with the outer circumference of the polishing surface narrows towards the center of the polishing surface.

7. The polishing pad according to claim 1, wherein the stepped portion is fan-shaped or half-oval-shaped when viewed from a direction perpendicular to the polishing surface.

8. The polishing pad according to claim 1, wherein the polishing layer has an inner step portion formed in the polishing layer centered on the central point of the polishing layer.

9. The polishing pad according to claim 1, wherein the polishing layer has a circular through-hole centered on the central point of the polishing layer, and an inner stepped portion is formed so as to be in contact with the central hole.

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

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