Polishing pad

Abstract

The purpose of the present invention is to provide a polishing pad having a long polishing life while suppressing over-polishing on the outer periphery of a workpiece. The present invention relates to a polishing pad in which a plurality of outer peripheral step portions are formed on the outer periphery of a polishing layer, thereby reducing the contact area with the outer periphery of a workpiece and suppressing over-polishing on the outer periphery of the workpiece.

Description

Polishing Pad

[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 suitable for polishing devices in which an oxide layer, a metal layer, etc. are formed on a semiconductor wafer.

[0002] Usually, 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 the wafer is slid relatively in a pressurized state to flatten the wafer surface by a composite 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 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 having 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 on the outer periphery of an object to be polished by reducing the thickness of the polishing layer on 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 at the outer periphery (it has a gentle slope). Before polishing progresses, the outer periphery of the object to be polished 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 periphery of the object to be polished 8 comes into contact with the polishing surface 41c in those areas as well, and it becomes impossible to suppress over-polishing on the outer periphery of the object to be polished 8 (short polishing life).

[0006] Japanese Patent Publication No. 2008-279553

[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.

[0008] As a result of their research, the inventors have found a polishing pad in which the contact area with the outer periphery of the workpiece is reduced and over-polishing of the outer periphery of the workpiece is suppressed by forming a plurality of outer periphery stepped portions on the outer periphery of the polishing layer and / or an inner stepped portion in a region near the center of the polishing layer. The present invention encompasses the following: [1] A polishing pad comprising a polishing layer having a polishing surface for polishing a workpiece, wherein a plurality of outer periphery stepped portions are formed in the polishing layer along the outer periphery of the polishing surface. [2] The polishing pad according to [1], wherein, in the outer periphery stepped portion, the side wall connecting the polishing surface and the bottom surface of the outer periphery 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 connecting the plurality of outer periphery stepped portions. [4] The polishing pad according to any one of [1] to [3], wherein the step height of the outer periphery stepped 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 of the outer peripheral step 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 outer peripheral step when viewed from a direction perpendicular to the polishing surface is such that the width of the outer peripheral step 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 outer peripheral step 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 an inner step is formed in the polishing layer, centered on the center point of the polishing layer. [9] A polishing pad comprising a circular polishing layer, wherein the polishing layer has an inner stepped portion having a gear-like shape centered on the center point of the polishing layer, and the side wall of the inner stepped portion is at an angle of 60 degrees or more and 90 degrees or less with respect to the extension surface of the bottom surface of the inner stepped portion in the direction of the side wall.

[10] The polishing pad according to [9], wherein the inner step portion is formed in an inner step 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, and the inner step 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 obtained by removing the circular region from a circle centered on the center point of the polishing layer and having a radius of 0.1 or more and less than 0.2 relative to the radius of the polishing layer, and a circular inner step portion is arranged in the circular region, and a gear-shaped inner step portion is arranged in the annular region.

[11] The polishing pad according to

[10] , wherein the total area of ​​the gear-shaped inner step portions in the annular region is 0.2 or more and less than 1.0 of the total area of ​​the annular region.

[12] The polishing pad according to any one of [9] to

[11] , wherein a plurality of outer peripheral step portions are formed along the outer circumference of the polishing surface in the polishing layer.

[13] The polishing pad according to any one of [9] to

[12] , wherein the height of the step of the inner step portion is smaller than the thickness of the polishing layer.

[14] A polishing pad comprising a polishing layer, wherein the polishing layer comprises a circular through-hole centered on the center point of the polishing layer, and an inner step portion formed to be in contact with the central hole.

[15] The polishing pad according to

[14] , further comprising an outer peripheral step portion in the polishing layer that is in contact with the outer circumference of the polishing surface.

[0009] By forming multiple outer-peripheral stepped portions on the outer periphery of the polishing layer and / or inner stepped portions 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 these stepped portions does not change (the degree of contact with the workpiece does not change) even as polishing progresses, over-polishing can be stably suppressed.

[0010] Figure 1 is a schematic diagram of polishing. Figure 2 is a schematic cross-sectional diagram 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 is a schematic cross-sectional diagram perpendicular to the polishing surface, showing the state of the slurry 9 near the outer circumference of the workpiece during polishing in a conventional polishing pad (arrow c indicates the direction of centrifugal force). Figure 4 is a schematic cross-sectional diagram perpendicular to the polishing surface, showing the state near the outer circumference of the workpiece at the outer peripheral step portion during polishing in the polishing pad of the present invention. Figure 5 is a schematic diagram of a polishing pad of one embodiment of the present invention, in which the outer peripheral step portion is fan-shaped when viewed from a direction perpendicular to the polishing surface. Figure 6 is a schematic cross-sectional diagram perpendicular to the polishing surface near the outer circumference 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 outer peripheral step portion. Figure 7 is a schematic diagram of a polishing pad according to one embodiment of the present invention, in which the outer peripheral step portion is half-oval in shape when viewed from a direction perpendicular to the polishing surface (double arrow l: width of the outer peripheral step portion). The connecting groove 11b and radial groove 11r formed on the polishing surface are also shown. Figure 8 is a diagram showing the mechanism for discharging polishing debris by grooves connecting the outer peripheral step portions (arrow k: rotation direction of the polishing pad, arrow h: slurry discharge direction, dashed arrow i: discharge of polishing debris). Figure 9 is a schematic cross-sectional diagram of the area near the outer peripheral portion of the polishing layer before and after polishing in the polishing pad of the present invention. Figure 10 is a schematic cross-sectional diagram of the area near the outer peripheral portion of the polishing layer before and after polishing in a polishing pad in which the thickness of the outer peripheral portion of the polishing layer gradually decreases as described in Patent Document 1. Figure 11 is a schematic diagram of the polishing layer 4C obtained in the embodiment. Figure 12 is a schematic cross-sectional diagram of the X-X section of the polishing layer 4C. Figure 13 is a diagram showing the trajectory that the outer peripheral point d of the workpiece passes through on the polishing surface during polishing. Figure 14 is a schematic diagram showing the trajectory of the outer circumference of the workpiece being polished on the polishing surface during polishing. Figure 15 is a diagram showing the inner step formation region (diameter D) that forms the inner step based on the trajectory. Figure 16 is a view of a polishing pad having an inner step according to one embodiment of the invention, viewed from a direction perpendicular to the polishing surface. Figure 17 is a cross-sectional view of the polishing pad and the workpiece being polished during polishing. Figure 18 is a schematic diagram of one embodiment of the inner step formation region.Figure 19 is a schematic diagram of one embodiment of the inner step-forming region. Figure 20 is a schematic diagram of the polished layer 4F obtained in the example.

[0011] The following describes embodiments for carrying out the invention, but the present invention is not limited to these embodiments.

[0012] <<Polishing Pad>> The structure of the polishing pad 3 will now be described. The polishing pad 3 includes a polishing layer 4 and a base layer 6. The shape of the polishing pad 3 is preferably disc-shaped, but is not particularly limited, and the size (diameter) can be appropriately determined according to the size of the polishing device 1 equipped with the polishing pad 3, for example, it can be about 10 cm to 2 m in diameter. In the present invention, the polishing pad 3 preferably has the polishing layer 4 bonded to the base layer 6 via an adhesive layer. The polishing pad 3 is attached to the polishing platen 10 of the polishing device 1 by double-sided tape or the like disposed on the base layer 6. As shown in Figure 1, the polishing pad 3 is rotated by the polishing device 1 while pressing against the workpiece 8 to be polished, and polishes the workpiece 8.

[0013] Here, we will explain overpolishing 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. At that time, as shown in Figure 2, the polishing layer near the outer periphery of the workpiece 8 is deformed by the retainer ring 5, so excessive pressure is applied to the outer periphery of the workpiece 8, making overpolishing likely (arrow a: direction of excessive pressure, arrow b: direction of polishing pressure and direction of repulsive force against polishing pressure). Also, as shown in Figure 3, due to the effect of centrifugal force, the slurry 9 tends to accumulate near the outer periphery of the workpiece 8, making overpolishing of the outer periphery of the workpiece 8 likely (arrow c: direction of centrifugal force). Furthermore, as will be described later, the trajectory of the outer periphery of the workpiece 8 during polishing is concentrated near the center and on the outer periphery of the polishing surface of the polishing layer 4. Therefore, overpolishing of the outer periphery of the workpiece can be suppressed by reducing the area of ​​the polishing surface on the outer periphery.

[0014] <Polishing layer> The polishing layer 4 rotates together with the polishing platen 10 of the polishing device 1, and while 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] (Outer Steps) As shown in Figure 5, the polishing layer 4 of the polishing pad 3 has multiple outer-peripheral step portions 42A formed along the outer circumference of the polishing surface 41. Formed along the outer circumference means that they are formed in a continuous manner parallel to the outer circumference, similar to how trees are planted along a road. Hereinafter, the step portions formed along the outer circumference will be referred to as outer-peripheral step portions, and the step portions formed in the region near the center of the polishing layer 4, with the center point of the polishing layer 4 as the center, will be referred to as inner step portions. The outer-peripheral step portions 42A refer to recesses formed in the polishing layer 4 as shown in Figure 4 in order to reduce the area of ​​the polishing surface 41. By forming multiple outer-peripheral step portions 42A along the outer circumference of the polishing surface 41, the area of ​​the outer circumference of the polishing 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 outer peripheral stepped portions 42A formed in the polishing layer 4 according to the degree of over-polishing of the outer peripheral portion relative to the central portion. For example, if the outer peripheral portion is 20% over-polished relative to the central portion, over-polishing can be suppressed by reducing the area of ​​the outer peripheral portion of the polishing surface 41 by approximately 20%. This 20% area reduction is achieved by changing the number of outer peripheral stepped portions 42A so as to reduce the area of ​​the outer peripheral portion of the polishing surface 41 by 20% without changing the area of ​​a single outer peripheral stepped portion 42A. In Figure 5, 11b is a connecting groove and 11r is a radial groove.

[0017] Referring to Figure 4, in the outer peripheral stepped portion 42A, the angle α between the side wall 42s connecting the polished surface 41 and the bottom surface 42b of the outer peripheral stepped portion 42A, and the surface 42c extending the bottom surface 42b of the outer peripheral stepped portion 42A 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 polishing performance changes because the polished surface 41 that comes into contact with the outer peripheral portion of the workpiece 8 increases as polishing progresses. The angle α between the side wall 42s and the surface 42c extending the bottom surface 42b of the outer peripheral step portion 42A 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, reduced by the outer peripheral step portion 42A, 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 outer peripheral step portion 42A 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 outer peripheral step portion 42A does not change much, and therefore the area of ​​the outer peripheral step portion 42A also does not change much.

[0018] The shape of the outer peripheral step portion 42A, when viewed from a direction perpendicular to the polishing 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. Preferably, the shape of the outer peripheral step portion 42A, such as a fan shape or a half-oval shape, is such that the width of the step portion in contact with the outer circumference of the polishing surface narrows towards the center of the polishing surface. As shown in Figure 5, the fan-shaped outer peripheral step portion 42A has a central angle β. By changing the angle of the central angle β of the fan-shaped outer peripheral step portion 42A, the area of ​​the outer peripheral step portion 42A 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 outer peripheral step portion 42A is the distance from the outer circumference of the polishing layer 4 to the point closest to the center point cut out by the formation of the outer peripheral step portion 42A. As shown in Figure 6, it is preferable that the length g of the outer peripheral step portion 42A 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 outer peripheral stepped portions 42A are formed by counterboring, although not particularly limited. Counterboring is a cutting process that creates a recess (counterbore) of a specific shape on the surface of a part. While not particularly limited, an end mill can be used for counterboring.

[0020] (Grooving and Embossing) Preferably, the polishing surface 41 is provided with connecting grooves 11b that connect a plurality of outer peripheral stepped portions 42A. 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 outer peripheral stepped portions 42A when the polishing surface 41 is rotated in the direction of arrow k (arrow k: direction of rotation of the polishing pad, dashed arrow i: discharge of polishing debris), and to be easily discharged from the outer peripheral stepped portions 42A (arrow h: direction of slurry discharge), thereby suppressing the occurrence of scratches on the outer periphery 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 not particularly limited. Preferably, the depth (step height) e of the outer peripheral stepped portion 42A formed in the polishing layer 4 is greater than the depth d of the connecting grooves 11b. If the step height e is smaller than the depth d of the connecting groove 11b, polishing debris that accumulates in the groove formed in the polishing surface 41 may not be easily discharged from the connecting groove 11b to the outer peripheral step portion 42A. Figure 6 shows a schematic cross-sectional view perpendicular to the polishing surface, and although Figure 6 shows a concentric groove 11c, 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 polishing 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 outer peripheral step portion 42A, 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 semi-circular. The pitch, width, and depth of the grooves are also not particularly limited. In addition to the connecting grooves 11b and radial grooves 11r, it is preferable to provide groove processing or embossing on the polished surface 41 of the polishing layer 4. The grooves are not particularly limited and may be 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 be combined. As shown in Figures 11 and 12, a grid-like groove 11d may be provided on the polishing surface 41 of the polishing layer 4, and the depth (step height) e of the outer peripheral step portion 42A and the inner step portion 42B formed on the polishing layer 4 may be the same as the depth d of the groove 11d. In low-pressure polishing, the platen is rotated at high speed to reduce the pressing force on the workpiece 8 and to ensure a high polishing rate. As a result, a phenomenon known as hydroplaning may occur, where slurry 9 exists in layers between the polishing surface 41 and the processed surface, hindering the polishing process. This phenomenon can be suppressed by grooving or embossing the polishing surface 41. It is also possible to promote the discharge of polishing debris and the movement of the polishing fluid. Furthermore, in order to improve the flatness of the polishing layer 4, surface grinding treatments such as buffing may be applied to the polishing surface 41 side or the side opposite to the polishing surface of the polishing layer 4.

[0022] 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 trajectory of the outer circumference of the workpiece 8 is relatively high near the center of the polishing layer 4, forming an 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 uniformly supplied to the entire polishing pad. Alternatively, the polishing layer 4 may have a circular through-hole centered on the center point of the polishing layer, and the inner step may be 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 from a polishing slurry supply device to the polishing surface of the polishing pad, while a shaft passing through the center rotates the upper and lower polishing plates in opposite directions using gears inside the polishing device, thereby flattening the surface of the workpiece held by the carrier that is in contact with the polishing surface of the polishing pad.

[0023] <Explanation of the Trajectory of the Workpiece> When the workpiece 8 is closest to the center point of the circle of the polishing layer 4 during polishing, the outer circumference of the workpiece 8 passes through the annular region 43 of the inner step-forming region. Here, the annular region is where the gear-shaped teeth 421 of the inner step-forming region 42B in Figure 16 are located. The following is a detailed explanation. Figure 13 shows the trajectory of the outer circumference point d, which is a point on the outer circumference of the workpiece 8 during polishing, on the polishing surface 41. The trajectory of the outer circumference point d of the workpiece 8 during polishing is concentrated near the center and on the outer circumference of the polishing surface 41 of the polishing layer 4. The outer circumference of the workpiece 8 where over-polishing occurs is the inner part of the outer circumference along the outer circumference of the workpiece 8, for example, the part from the outer circumference of the workpiece 8 to a length of 1 / 5 to 1 / 100 of the radius inward. Figure 14 is a schematic diagram of the trajectory of the outer circumference of the workpiece 8. Figure 14 shows that the trajectories of the outer circumference of the workpiece 8 are concentrated near the center of the polishing surface 41 of the polishing layer 4 and on the outer circumference of the polishing surface 41. The area near the center of the polishing surface 41 is shown in Figure 15 as the circular inner step portion forming region 43 (the region where the circular portion 422 and the tooth portion 421 are formed as the inner step portion 42B) drawn at the center of the polishing layer 4. Figure 16 shows the polishing layer 4 with an inner step portion 42B in which the tooth portion 421 is formed. Figure 16 also 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 13 to 15 are millimeters, and the outer circumference region of the workpiece 8 is assumed to have a radius of 135 mm or more and 150 mm or less. Furthermore, the inner step-forming region 43 having a diameter D in Figure 15 is a circular region centered on the central point of the polishing layer 4, with a radius of 0.2 or less relative to the radius of the polishing layer 4.

[0024] Furthermore, the inner step-forming region 43 is composed of a circular region 43A centered on 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 on 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 step portion of the circular part 422, and the annular region 43B has a tooth portion 421. For example, Figures 18 and 19 show an example of an inner step-forming region 42B formed in the inner step-forming region 43.

[0025] (Inner Step) As shown in Figure 16, the polishing layer 4 of the polishing pad 3 has an inner step 42B which has a gear-like shape centered on the center point of the polishing layer 4. The inner step 42B is composed of a circular part 422 and a toothed part 421. The inner step 42B refers to a recess formed to reduce the area of ​​the polishing surface 41 near the center where there is frequent contact with the outer circumference of the workpiece 8. As explained using Figures 13 to 15, 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. By reducing the area of ​​the polishing surface 41 which has frequent contact with the outer circumference of the workpiece, over-polishing of the outer circumference of the workpiece 8 can be suppressed. However, the density of trajectories is very high on the outer circumference of the polishing layer 4, and it is not possible to make the entire outer circumference of the polishing layer 4 a step. Forming a step on a part of the outer circumference of the polishing layer 4 is time-consuming to process. Although the density of the trajectories is high near the center of the polishing layer 4, it is lower than that of the outer periphery of the polishing layer 4. Therefore, it is possible to make the entire area near the center of the polishing layer a stepped section, which shortens the processing time compared to creating a stepped section on the outer periphery of the polishing layer and suppresses over-polishing of the outer periphery of the workpiece.

[0026] Figure 17 is a cross-sectional view of the polishing pad and the workpiece during polishing. As shown in Figure 17, in the inner stepped portion 42B, the angle α between the side wall 42s connecting the polishing surface 41 and the bottom surface 42b of the inner stepped portion 42B, and the extension surface 42c of the bottom surface 42b of the inner stepped portion 42B in the direction of the side wall, is preferably 60 degrees or more and 90 degrees or less. More preferably, it is 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 is 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 inner stepped portion 42B in the direction of the side wall is preferably 60 degrees or more and 90 degrees or less, forming a step with a large incline. Even if 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 inner stepped portion 42B does not change much, and thus the polishing performance does not change. The depth of the inner stepped portion 42B is smaller than the thickness of the part of the polished layer 4 other than the stepped portion.

[0027] Because an inner stepped portion 42B is formed in the region near the center of the polishing layer 4, the inner stepped portion 42B acts as a slurry reservoir, and by providing a groove connected to the inner stepped portion 42B, the slurry 9 can be supplied evenly to the entire polishing layer 4 by centrifugal force.

[0028] 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.

[0029] When viewed from a direction perpendicular to the polishing surface, the total area of ​​the teeth 421 is preferably 0.2 or more and less than 1.0, and more preferably 0.4 or more and 0.9 or less, relative to the area of ​​the annular region 43B. The polishing pad 3 of the present invention can adjust the degree of suppression of overpolishing by changing the shape of the inner stepped portion 42B formed in the polishing layer 4 according to the percentage of overpolishing of the outer circumference of the workpiece 8 when polishing is performed with a conventional polishing pad, and by adjusting the total area of ​​the openings of the inner stepped portion 42B in the annular region 43. As for variations in shape, the shapes shown in Figures 18 and 19 can be cited, and the area ratio of the stepped portion in the annular region increases from Figure 18 to Figure 19.

[0030] The inner stepped portion 42B 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.

[0031] The polishing layer 4 may include a circular through-hole 423 centered on the center point of the polishing layer, and an inner stepped portion 42B formed in contact with the central hole 423. The presence of the central hole 423 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.

[0032] The polishing layer 4 may preferably have multiple outer peripheral stepped portions 42A formed along the outer circumference of the polishing surface 41. Forming outer peripheral stepped portions along the outer circumference means that stepped portions are formed along the outer circumference, similar to how trees are planted along a road. As described above, the areas where the trajectories of the outer circumference of the workpiece 8 are concentrated are near the center and the outer circumference of the polishing surface 41 of the polishing layer 4. Therefore, if multiple outer peripheral stepped portions 42A are formed along the outer circumference of the polishing surface 41, over-polishing of the workpiece 8 can be further suppressed.

[0033] (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. As for specific main component materials, for example, a material obtained by reacting an isocyanate-terminated prepolymer with a curing agent can be mentioned. The polishing layer 4 is formed by pouring a mixture of isocyanate-terminated prepolymer and a curing agent (chain extender) into a mold and slicing the molded body that has been cured. In other words, the polishing layer 4 is dry-molded. The polishing layer 4 may have hollow microspheres (foam) dispersed in it, or it may not have hollow microspheres, but it is preferable that it has hollow microspheres dispersed in it.

[0034] The polishing layer 4 is preferably made of a polyurethane resin sheet having closed cells.

[0035] The hollow microspheres dispersed within the polishing layer 4 are not particularly limited, but are preferably spherical, elliptical, or have similar 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.

[0036] 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 m in diameter, and the thickness of the polishing layer 4 can be approximately 1 to 5 mm.

[0037] <<Method for Manufacturing Polishing Pads>> The method for manufacturing the polishing pad 3 of the present invention will be described below.

[0038] <Method for manufacturing the polishing layer> (Materials for the polishing layer) The materials for the polishing layer 4 are not particularly limited, but for example, polyurethane resin, polyurea resin, and polyurethane-polyurea resin are preferred as the main components, and polyurethane resin is more preferred.

[0039] The manufacturing method for the material of the polishing layer 4 will be explained below using an example that utilizes an isocyanate-terminated prepolymer and a curing agent.

[0040] 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 an outer peripheral step portion 42A and / or an inner step portion 42B.

[0041] The following will explain each of the following processes: material preparation, mixing, molding, grooving, and counterboring.

[0042] (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 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 in its molecule. Other components may also be included in the isocyanate-terminated prepolymer. As the isocyanate-terminated prepolymer, a commercially available one may be used, or one synthesized by reacting a polyisocyanate compound and a polyol compound may be used. There are no particular restrictions on the above 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. The polyisocyanate compound is not particularly limited as long as it has two or more isocyanate groups in its molecule.For example, diisocyanate compounds having two isocyanate groups in the 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 [2,2-amino-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 Glycol, propylene glycol, diethylene glycol, trimethylene glycol, tetraethylene glycol, triethylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,2-butanediol, 3-methyl-1,2-butanediol, 1,2-pentanediol, 1,4-pentanediol, 2,4-pentanediol, 2,3-dimethyltrimethylene glycol, tetramethylene glycol, 3-methyl-4,3-pentanediol, 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.Further, the polyvalent amine compound may have a hydroxyl group. Examples of such amine compounds include 2-hydroxyethyl ethylenediamine, 2-hydroxyethyl propylenediamine, di-2-hydroxyethyl ethylenediamine, di-2-hydroxyethyl propylenediamine, 2-hydroxypropyl ethylenediamine, di-2-hydroxypropyl ethylenediamine, and the like. As the polyvalent amine compound, a diamine compound is preferable, and more preferably, for example, 3,3'-dichloro-4,4'-diaminodiphenylmethane (methylene bis-o-chloroaniline) (hereinafter abbreviated as MOCA) is used. In addition to the above components, additives such as oxidants may be added as needed to the material of the polishing layer 4.

[0043] If necessary, the polishing layer 4 can be formed by using hollow microspheres having an outer shell and a hollow interior as a material. As the material of the hollow microspheres, commercially available ones may be used, or those obtained by synthesis by a conventional method may be used. The material of the outer shell of the hollow microspheres is not particularly limited. For example, polyvinyl alcohol, polyvinylpyrrolidone, poly(meth)acrylic acid, polyacrylamide, polyethylene glycol, polyhydroxyether acrylate, maleic acid copolymer, polyethylene oxide, polyurethane, poly(meth)acrylonitrile, polyvinylidene chloride, polyvinyl chloride, and organosilicon resins, and copolymers (for example, acrylonitrile-vinylidene chloride copolymer, etc.) obtained by combining two or more monomers constituting these resins can be mentioned. In addition, commercially available hollow microspheres include, but are not limited to, for example, Expancel series (trade name of Akzo Nobel), Matsumoto Microsphere (trade name of Matsumoto Yushi Co., Ltd.), and the like. The gas contained in the hollow microspheres is not particularly limited. For example, hydrocarbons can be mentioned, and specifically, isobutane and the like can be mentioned. In addition to the above components, conventionally used foaming agents may be used in combination with the hollow microspheres, or a gas that is non-reactive with the above components may be blown into the above components during the following mixing step.

[0044] (Mixing Process) In the mixing process, the isocyanate-terminated prepolymer and the curing agent obtained in the material preparation process are fed into a mixer and stirred and mixed. The mixing process is carried out in a heated state at a temperature that can ensure the fluidity of each of the above components.

[0045] (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 to 100 °C and cured primarily, and then heated at about 100 to 150 °C for about 10 minutes to 5 hours to cure secondarily, thereby molding a cured polyurethane resin (a polyurethane resin molded body). At this time, the isocyanate-terminated prepolymer and the curing agent react to form a polyurethane resin, whereby the mixed liquid cures.

[0046] In the molding process, if necessary, the poured mixed liquid is reacted in the mold to form a molded body. At this time, the prepolymer crosslinks and cures due to the reaction between the prepolymer and the curing agent.

[0047] After obtaining the molded body, it is sliced into sheets to form a plurality of polishing layers 4. For slicing, a general slicing machine can be used. During slicing, the lower layer portion of the polishing layer 4 is held, and it is sliced into a predetermined thickness in order from the upper layer portion. The slicing thickness is set, for example, in the range of 1.3 to 2.5 mm. In the case of a molded body molded in a mold with a height of 50 mm, for example, about 10 mm of the upper layer portion and the lower layer portion of the molded body are not used due to scratches or the like, and 10 to 25 polishing layers 4 are formed from about 30 mm of the central portion.

[0048] (Grooving Process) Grooving is performed on the polishing surface 41 of the obtained polishing layer 4. By performing cutting or the like on the polishing surface 41 using a required cutting tool, grooves having an arbitrary pitch, width, and depth can be formed.

[0049] (Counterboring Process) Counterboring is performed on the obtained polishing layer 4 to form a plurality of outer peripheral side step portions 42A and / or inner side step portions 42B. The counterboring is not particularly limited, but an end mill can be used.

[0050] 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.

[0051] <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.

[0052] <Bonding Process> In the bonding process, the formed polishing layer 4 and base material 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 material 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 material layer 6 are pressed together via double-sided tape or adhesive to bond the polishing layer 4 and base material 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.

[0053] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0054] In each example and comparative example, unless otherwise specified, "parts" means "parts by mass."

[0055] 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)]".

[0056] (Regarding the polishing 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 obtained by synthesizing adipic acid and 1,4-butanediol (number average molecular weight of 2000), and diethylene glycol (DEG), were mixed with 1.2 parts of unexpanded hollow microspheres, the shell portion of which is made of acrylonitrile-vinylidene chloride copolymer and contains isobutane gas inside the shell, to obtain a mixed solution. The obtained mixed solution 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. The two injected liquids were mixed and stirred while being poured into a mold of a preheated molding machine, then 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. The obtained polyurethane resin molded body was allowed to cool to 25°C, then heated again in an oven at 120°C for 5 hours, and then sliced ​​to a thickness of 1.6 mm to obtain a polished layer 4.

[0057] 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.

[0058] (Density) Density of polished layer 4 (g / cm³) ３ The measurements were taken in accordance with the Japanese Industrial Standard (JIS K 6505).

[0059] (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 measurement sample was obtained by stacking multiple polished layers as needed, so that the total thickness was at least 4.5 mm.

[0060] (Regarding groove processing) 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 with a width of 1.5 mm and a depth of 0.8 mm were made.

[0061] (Regarding the counterboring of the outer peripheral stepped portion) On the grooved polished layer 4, seven fan-shaped outer peripheral stepped portions 42A 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 tapering at a 60-degree angle, so as not to connect to the radial grooves 11r, to form the polished layer 4A. The angle α between the side wall 42s of the outer peripheral stepped portion 42A and the surface 42c extending from the bottom surface of the outer peripheral stepped portion 42A in the direction of the side wall 42s is 60 degrees. On the grooved polished layer 4, 32 half-oval-shaped outer peripheral stepped portions 42A 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, to form the polished layer 4B. The angle α between the side wall 42s of the outer peripheral stepped portion 42A and the surface 42c that extends the bottom surface of the outer peripheral stepped portion 42A 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 due to the formation of the outer peripheral stepped portion 42A.

[0062] (Examples and Comparative Examples) The polishing layers 4A and 4B obtained by counterboring as described above were joined to a base layer made of commercially available foamed urethane foam (Sekisui Sponge 2504KMS, manufactured by Sekisui Chemical Co., Ltd., 1.2 mm thick) with a 0.1 mm thick double-sided tape (a PET base material with adhesive layers made of acrylic resin on both sides), and the double-sided tape was attached to the opposite side of the base layer and the adhesive layer to produce polishing pads A and B (Examples 1 and 2). Polishing pad C (Comparative Example 1) was produced in the same manner using an polishing layer that had not been counterbored.

[0063] (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 polishing. The results are summarized in Table 1. From Table 1, it was found that when polishing was performed using polishing pads A and B of Examples 1 and 2, over-polishing of the outer circumference 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 is equivalent to the polishing rate from the center to 135 mm, and over-polishing of the outer circumference 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 to 135 mm, and over-polishing of the outer circumference of the workpiece 8 is not suppressed.

[0064]

[0065] (Polishing conditions) Polishing machine: F-REX300X (Ebara Corporation) Disk: A188 (3M) Retainer ring: Retainer ring GXKD (Ebara Corporation) Rotation speed: (Surface plate) 90 rpm, (Polishing head) 81 rpm Polishing pressure: 1.7 psi Polishing agent temperature: 20℃ Polishing agent discharge rate: 200 ml / min Polishing agent: (CES-5003-2.5 concentrate: pure water = weight ratio 1:3 mixture used) (AGC Inc.) Workpiece: TEOS film substrate (300 mm diameter disc) Polishing time: 60 seconds Pad break: 32N 30 minutes Conditioning: Ex-situ 32N, 4 scans

[0066] From the polishing layer 4 obtained in the above embodiment, a counterbore polishing layer 4C, as shown in Figures 11 and 12 (cross-sectional view 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 423 with a diameter of 440 mm was provided centered at the center point of the polishing layer 4. From the central hole 423 of the grooved polishing layer 4 toward the outer edge, eight inner counterbores were made at a 45° pitch with respect to the center point of the polishing layer 4 using a circular end mill with a diameter of 25 mm, creating an inner stepped portion 42B with a depth of 0.35 mm and a radius of 71 mm, in contact with the central hole 423. Furthermore, 24 outer counterbores were created at 15° intervals from the outer edge toward the center point, with the center point of the polished layer 4 as the reference point. These counterbores were formed in a semi-circular shape with a depth of 0.35 mm and a radius of 71 mm, and were in contact with the outer edge, creating an outer-side stepped portion 42A. The resulting polished layer is referred to as polished layer 4C. The depth of the inner stepped portion 42B and the outer-side stepped portion 42A from the polished surface 41 is the same as the depth of the groove 11d. The angle α between the side walls of the inner stepped portion 42B and the outer-side stepped portion 42A and the bottom surfaces of the stepped portions 42A and 42B extended in the direction of the side walls was 90 degrees. Note that in Figure 12, the number of grooves 11d is reduced in the drawing for ease of understanding.

[0067] (Regarding the counterboring of the inner stepped portion) Using a circular end mill with a diameter of 30 mm, a circular stepped portion 422 with a diameter of 115 mm was formed on the grooved polishing layer 4 such that the center of the polishing pad coincided with the center of the stepped portion. The circular end mill was moved radially from the center of the circular stepped portion, and eight stepped portions were formed at equal intervals on the outer circumference of the circular stepped portion, protruding from the outer circumference of the circular stepped portion by the radius distance of the circular end mill, thereby forming a gear-shaped inner stepped portion 42B (polished layer 4D). The angle α between the side wall 42s of the inner stepped portion 42B and the extension surface 42c of the bottom surface 42b of the inner stepped portion 42B in the direction of the side wall was 90°, and the depth of the inner stepped portion 42B was 1.0 mm. The ratio of the area of ​​the inner stepped portion 42B 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 422 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 inner stepped portion 42B (polished layer 4E). The angle α between the side wall 42s of the inner stepped portion 42B and the extension surface 42c of the bottom surface 42b of the inner stepped portion 42B in the direction of the side wall was 90°, and the depth of the inner stepped portion 42B was 1.0 mm. The ratio of the area of ​​the inner stepped portion 42B to the area of ​​the annular region of the formed stepped portion was 0.9.

[0068] (Examples and Comparative Examples) The polishing layers 4D and 4E obtained by counterboring as described above were joined to a base layer made of commercially available foamed urethane foam (Sekisui Sponge 2504KMS, manufactured by Sekisui Chemical Co., Ltd., 1.2 mm thick) with a 0.1 mm thick double-sided tape (a PET base material with adhesive layers made of acrylic resin on both sides), and the double-sided tape was attached to the opposite side of the base layer and the adhesive layer to manufacture polishing pads D and E (Examples 3 and 4). Polishing pad F (Comparative Example 2) was manufactured in the same manner using an polishing layer that had not been counterbored. The diameter of the manufactured polishing pads was 740 mm.

[0069] (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 polishing. The results are summarized in Table 2. From Table 2, it was found that when polishing was performed using polishing pads D and E of Examples 3 and 4, overpolishing at the outer circumference of the workpiece 8 was suppressed compared to polishing pad F of Comparative Example 2. In the table, "○" indicates that the polishing rate from 135 to 150 mm from the center of the workpiece 8 with a diameter of 300 mm is equivalent to the polishing rate from the center of the workpiece 8 layer to 135 mm, indicating that overpolishing at the outer circumference 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 workpiece 8 layer to 135 mm, indicating that overpolishing at the outer circumference of the workpiece 8 is not suppressed.

[0070]

[0071] (Polishing conditions) Polishing machine: F-REX300X (Ebara Corporation) Disk: A188 (3M) Retainer ring: Retainer ring GXKD (Ebara Corporation) Rotation speed: (Surface plate) 90 rpm, (Polishing head) 81 rpm Polishing pressure: 1.7 psi Polishing agent temperature: 20℃ Polishing agent discharge rate: 200 ml / min Polishing agent: (CES-5003-2.5 concentrate: pure water = weight ratio 1:3 mixture used) (AGC Inc.) Workpiece: TEOS film substrate (diameter 300 mm) Polishing time: 60 seconds Pad break: 32N 30 minutes Conditioning: Ex-situ 32N, 4 scans

[0072] Except for the absence of external counterboring, the polished layer 4F was manufactured using the same process as polished layer 4C (see Figure 20). Note that in Figures 11 and 20, the number of grooves 11d is shown in a reduced number for ease of understanding.

[0073] 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.

[0074] 1 Polishing device 3 Polishing pad 4 Polishing layer 41 Polishing surface 42A Outer peripheral step 42B Inner step 42s Side wall of step 42b Bottom surface of step 42c Surface extending from the bottom surface of step towards the side wall 421 Tooth portion (part of step) 422 Circular portion (part of step) 423 Central hole 43 Inner step forming region 43A Circular region 43B Annular region 5 Retainer ring 6 Base layer 8 Workpiece to be polished 9 Slurry 10 Polishing platen 11b Connecting groove 11r Radial groove 11c Concentric groove 11d Grid groove 16 Holding platen

Claims

1. A polishing pad comprising a polishing layer having a polishing surface for polishing an object to be polished, wherein a plurality of outer peripheral 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, in the outer peripheral stepped portion, the side wall connecting the polishing surface and the bottom surface of the outer peripheral stepped portion is at an angle of 60 degrees or more and 90 degrees or less with respect to the 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 outer peripheral stepped portions.

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

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

6. The polishing pad according to claim 1, wherein the shape of the outer peripheral step portion, when viewed from a direction perpendicular to the polishing surface, is such that the width of the outer peripheral step 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 on the outer circumference 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 an inner step portion is formed in the polishing layer, centered on the central point of the polishing layer.

9. A polishing pad comprising a circular polishing layer, wherein the polishing layer has an inner stepped portion having a gear-like shape centered on the central point of the polishing layer, and the side wall of the inner 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 inner stepped portion that extends in the direction of the side wall of the inner stepped portion.

10. The polishing pad according to claim 9, wherein the inner step portion is formed within an inner step 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, and the inner step 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 obtained by removing the circular region from a circle 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, and a circular inner step portion is arranged in the circular region, and a gear-shaped inner step portion is arranged in the annular region.

11. The polishing pad according to claim 10, wherein the total area of ​​the inner 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.

12. The polishing pad according to claim 9, wherein a plurality of outer peripheral stepped portions are formed along the outer circumference of the polishing surface in the polishing layer.

13. The polishing pad according to claim 9, wherein the height of the step in the inner step portion is smaller than the thickness of the polishing layer.

14. A polishing pad comprising a polishing layer, wherein the polishing layer comprises a circular through-hole centered on the center point of the polishing layer, and an inner stepped portion formed in contact with the central hole.

15. The polishing pad according to claim 14, further comprising an outer peripheral step portion in the polishing layer that is in contact with the outer circumference of the polishing surface.

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