Polishing pad

Abstract

To prevent a decrease in precision of detection of an endpoint of polishing through a transparent endpoint detection window by preventing slurry or polishing waste from remaining on the endpoint detection window.SOLUTION: A polishing pad 3 comprises a polishing layer 3C having an endpoint detection window 3B through which inspection light L1 can pass, and its polishing face 3A is formed with a plurality of concentrically circular annular grooves 3Aa. A top face 3Ba of the endpoint detection window 3B is lower than the polishing face 3A, which is a recess 3Ca. A radial discharge groove 3E is formed from the top face 3Ba and the recess 3Ca of the endpoint detection window 3B to a not-illustrated outer peripheral edge of the polishing face 3A. Even when slurry or processed waste flows into the top face 3Ba or the recess 3Ca of the endpoint detection window 3B during polishing, it is discharged outside of the polishing face 3A via the discharge groove 3E. Therefore, slurry or polishing waste can be prevented from remaining on the top face 3Ba of the endpoint detection window 3B.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a polishing pad, and more particularly to a polishing pad provided with a transparent end point detection window for detecting the end point of a polishing process and having a discharge groove formed on the polishing surface to prevent a decrease in the detection accuracy of the end point detection window.

Background Art

[0002] Conventionally, a polishing pad provided with a transparent end point detection window for detecting the end point of a polishing process and having a discharge groove for discharging slurry and polishing debris provided on a polishing surface or the like is known (for example, Patent Documents 1 to 2). In the polishing pad of Patent Document 1, one surface (upper surface) of the end point detection window is located at a position lower than the bottom of the discharge groove formed on the polishing surface. On the other hand, in the polishing pad of Patent Document 2, a concave surface is formed on the upper surface of the end point detection window, and a discharge groove is formed in the concave surface.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the polishing pad of Patent Document 1, since one surface (upper surface) of the end point detection window is located at a position lower than the polishing surface, slurry and polishing debris may stay on the end point detection window during the polishing process, and the end point detection accuracy by the end point detection window may decrease. On the other hand, in the polishing pad of Patent Document 2, a concave surface is formed on the upper surface of the end point detection window, and a discharge groove is formed in the concave surface. Therefore, since the amount of transmitted inspection light is different between the discharge groove and other portions, there is a problem that the end point detection accuracy by the end point detection window decreases. In addition, when passing inspection light through a portion other than the discharge groove, it is necessary to enlarge the end point detection window, and the end point detection window may affect the polishing performance.

Means for Solving the Problems

[0005] In view of the above circumstances, the present invention provides a polishing pad including a polishing layer having a polishing surface for polishing an object to be polished, and a transparent end point detection window provided in the polishing layer for detecting an end point during polishing. One surface on the polishing surface side of the end point detection window is formed to be lower in height than the polishing surface, and a concave portion is formed between the end point detection window and the polishing surface. Furthermore, at least one discharge groove communicating from the concave portion to the outer peripheral edge of the polishing surface is formed on the polishing surface. During polishing, slurry and polishing debris are discharged outward from the polishing surface through the discharge groove via the concave portion.

Effects of the Invention

[0006] According to such a configuration, it is possible to prevent slurry and polishing debris from staying in the end point detection window, so that the transmission condition when the inspection light passes through the end point detection window does not change. Therefore, it is possible to prevent a decrease in end point detection accuracy. In addition, since one surface on the polishing surface side of the end point detection window is formed to be lower in height than the polishing surface, the influence of the end point detection window on polishing can be minimized as much as possible.

Brief Description of the Drawings

[0007]

Figure 1

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Mode for Carrying Out the Invention

[0008] Hereinafter, the present invention will be described with reference to the illustrated embodiments. In FIGS. 1 to 2, reference numeral 1 denotes a polishing apparatus. This polishing apparatus 1 is adapted to polish a thin plate-shaped workpiece 2 (for example, a semiconductor wafer) with a polishing pad 3. When performing polishing on the workpiece 2, the polishing apparatus 1 irradiates inspection light L1 toward the polished surface 2A of the workpiece 2, so that the progress of the polishing process and the end point of the processing can be detected. The polishing apparatus 1 includes a polishing platen 4 located on the lower side with the polishing pad 3 fixed to the upper surface, a holding platen 5 located on the upper side with the workpiece 2 held on the lower surface, a slurry supply mechanism 6 for supplying slurry S (polishing liquid) between the workpiece 2 and the polishing pad 3, and a detection mechanism 7 for detecting the progress of the polishing process and the end point of the processing of the workpiece 2 using the inspection light L1. The workpiece 2 to be polished by the polishing apparatus 1 is a plate-shaped object such as an optical material, a silicon wafer, a glass substrate for liquid crystal, a semiconductor substrate, as well as glass, metal, ceramic, etc. Further, as the slurry S supplied by the slurry supply mechanism 6, a conventionally known suitable one can be used according to the workpiece 2 to be processed and the required processing accuracy. The polishing platen 4 and the holding platen 5 are each substantially disk-shaped, and are each adapted to rotate in the direction of the arrow by a drive mechanism (not shown). Further, the holding platen 5 is provided so as to be movable up and down. When performing polishing on the workpiece 2, the polished surface 2A (lower surface) of the workpiece 2 is pressed against the polishing surface 3A of the polishing pad 3 with a set pressure by the holding platen 5, and they are relatively rotated while the slurry S is supplied from the slurry supply mechanism 6 between the polished surface 2A of the workpiece 2 and the polishing surface 3A of the polishing pad 3. On the polishing surface 3A of the polishing pad 3, a plurality of annular grooves 3Aa are formed at equal pitches in the radial direction concentrically around the center (rotation center) of the polishing pad 3. These plurality of annular grooves 3Aa serve as slurry holding grooves for holding the slurry S, and the slurry S discharged from the slurry supply mechanism 6 flows into these plurality of annular grooves 3Aa and is supplied to the entire area of the polishing surface 3A (see FIGS. 2 to 4).

[0009] Incidentally, when polishing the workpiece 2, it is necessary to detect the progress of the polishing process of the workpiece 2 and the end point at which the processing is completed. Therefore, this polishing apparatus 1 includes a detection mechanism 7 that irradiates inspection light L1 from below upward and detects the progress of the polishing process and the end point based on the reflected light L2 from the polished surface 2A of the workpiece 2. At a predetermined position of the polishing pad 3, a transparent end point detection window 3B is provided that transmits the inspection light L1 and also transmits the reflected light L2 from the polished surface 2A of the workpiece 2. The polishing pad 3 includes a disk-shaped polishing layer 3C located on the upper side and a disk-shaped support layer 3D (cushion layer) adhered to the lower surface of the polishing layer 3C with an adhesive or double-sided tape. A transparent end point detection window 3B is provided at a predetermined position of the polishing layer 3C, and a through hole 3Da for passing the inspection light L1 and the reflected light from the workpiece 2 is formed at the position of the support layer 3D on the lower side thereof. The flat upper surface 3Ba of the end point detection window 3B is slightly lower than the polishing surface 3A which is the upper surface of the polishing layer 3C. Specifically, the upper surface 3Ba is at a position lower than the bottom of the annular groove 3Aa and is about 0.9 mm lower than the polishing surface 3A, whereby a circular recess 3Ca is formed at the upper position of the upper surface 3Ba. As described above, a plurality of annular grooves 3Aa are formed concentrically on the polishing surface 3A, and several of these annular grooves 3Aa intersect with the recess 3Ca at the adjacent upper position of the end point detection window 3B. That is, as shown in FIGS. 3 to 4, a plurality of annular grooves 3Aa open on the inner peripheral surface of the recess 3Ca, and the annular grooves 3Aa and the recess 3Ca are in a communicating state. On the other hand, the lower surface 3Bb of the end point detection window 3B and the lower surface of the polishing layer 3C are on the same plane, and the upper surface of the support layer 3D is adhered to the lower surface of the polishing layer 3C by an adhesive or a double-sided tape. Then, the polishing pad 3 composed of the polishing layer 3C and the support layer 3D integrated vertically is fixed to the upper surface 4A of the polishing platen 4 by an adhesive or a double-sided tape on its lower surface (the lower surface of the support layer 3D). On the polishing platen 4, a light emitting portion 7A that irradiates inspection light L1 upward and a light receiving portion 7B that receives reflected light from the workpiece 2 are provided at positions below the end point detection window 3B of the polishing pad 3 and the through hole 3Da of the support layer 3D. The detection mechanism 7 includes these light emitting portion 7A and light receiving portion 7B, and a control portion 7C that controls their operations and detects the progress of the processing and the end point of the completion of the polishing process during the polishing process. During the polishing process of the workpiece 2, since the inspection light L1 is irradiated upward from the light emitting portion 7A of the detection mechanism 7, the inspection light L1 passes through the transparent end point detection window 3B and irradiates the polished surface 2A of the workpiece 2. Then, the inspection light L1 is reflected downward by the polished surface 2A of the workpiece 2, and the reflected light L2 passes through the transparent end point detection window 3B and is detected by the light receiving portion 7B. The reflected light L2 detected by the light receiving portion 7B is transmitted to the control portion 7C. As the polishing process of the workpiece 2 progresses and the polished surface 2A of the workpiece 2 is gradually polished, the intensity etc. of the reflected light L2 detected by the light receiving portion 7B change. When the intensity etc. of the reflected light L2 detected by the light receiving portion 7B become the pre-registered intensity etc., the control portion 7C determines that the polished surface 2A has reached the processing end point and stops the polishing process. Then, since the drive mechanism is stopped, the rotation of the polishing platen 4 and the holding platen 5 stops, and the supply of the slurry S from the slurry supply mechanism 6 also stops. In this way, when the polishing process of the workpiece 2 is performed using the inspection light L1 of the detection mechanism 7, the end point of the polishing process can be detected. Note that the configuration of the detection mechanism 7 using such inspection light L1 is already known.

[0010] Thus, as shown in FIGS. 3 to 4, the polishing pad 3 of the present embodiment is characterized in that a discharge groove 3E in the radial direction reaching from the upper surface 3Ba of the end point detection window 3B and the position of the concave portion 3Ca to the outer peripheral edge of the polishing surface 3A is formed on the polishing surface 3A of the polishing layer 3C. The end point detection window 3B is formed in a disc shape by a transparent material that transmits the inspection light L1 and the reflected light L2, and this end point detection window 3B is fitted into a through hole formed at a predetermined position of the polishing layer 3C without a gap. The diameter of the end point detection window 3B is set to 9 mm, and the axial dimension (vertical dimension) is shorter than the thickness of the polishing layer 3C. In addition, as the material of the end point detection window 3B, an elastic resin such as polyurethane can be used. The end point detection window 3B needs to have a structure that avoids foaming that would interfere with the inspection light L1 and the reflected light L2. More specifically, an elastic resin body such as polyurethane in which no voids are formed inside is preferable. In the present embodiment, the end point detection window 3B is circular, but it can also have various other shapes such as rectangular, square, polygonal, elliptical, etc. Also, at least one end point detection window 3B may be provided. The height difference between the polishing surface 3A and the upper surface 3Ba of the end point detection window 3B (the depth of the concave portion 3Ca) is set to about 0.9 mm. Further, the width of each annular groove 3Aa is set to 0.4 mm, and the pitch between adjacent annular grooves 3Aa is set to 2.8 mm. Also, the depth of each annular groove 3Aa is set to 0.6 mm. Thereby, slurry or the like flows from the annular groove 3Aa into the concave portion 3Ca. The discharge groove 3E is linearly formed in the radial direction of the polishing layer 3C. The outer end of the discharge groove 3E opens to the outer peripheral edge (outer peripheral surface) of the polishing layer 3C (not shown), and the inner end of the discharge groove 3E opens to the inner peripheral surface of the recess 3Ca. The discharge groove 3E intersects with a plurality of annular grooves 3Aa formed on the polishing surface 3A and is in communication with them. The depth of the discharge groove 3E is set to 0.8 mm. The bottom of the discharge groove 3E is higher than the upper surface 3Ba of the end point detection window 3B and is located at the same or lower position than the bottom of the annular groove 3Aa. Thereby, a certain amount of slurry or the like is maintained in a state of accumulating on the upper surface 3Ba of the end point detection window 3B until it is discharged from the discharge groove 3E, and it is possible to prevent the intensities of the inspection light L1 and the reflected light L2 from decreasing along with the flow of the slurry or the like. As a result, it is possible to prevent the end point detection accuracy by the detection mechanism 7 from decreasing. A plurality of annular grooves 3Aa also intersect with the discharge groove 3E adjacent to the upper surface 3Ba of the end point detection window 3B, and the plurality of annular grooves 3Aa and the discharge groove 3E are in a communicating state (see FIGS. 2 to 4).

[0011] As described above, the polishing pad 3 of the present embodiment is formed with a radial discharge groove 3E that reaches from the position of the upper surface 3Ba (recess 3Ca) of the end point detection window 3B to the outer peripheral edge of the polishing surface 3A on the polishing surface 3A. Therefore, even if the slurry S or polishing debris flows into the upper surface 3Ba (recess 3Ca) during the polishing process of the workpiece 2 by the polishing pad 3, it is discharged from the recess 3Ca to the outside of the polishing surface 3A through the radial discharge groove 3E (see the imaginary arrow in FIG. 4). Thereby, it is possible to prevent the slurry S and the polishing debris from staying on the upper surface 3Ba and the recess 3Ca of the end point detection window 3B. Therefore, it is possible to prevent the intensities of the inspection light L1 and the reflected light L2 transmitted through the end point detection window 3B from decreasing, and as a result, it is possible to prevent the end point detection accuracy by the detection mechanism 7 from decreasing. Also, the upper surface 3Ba of the end point detection window 3 is provided lower than the bottom of the discharge groove 3E, and the depth difference from the polishing surface 3A to the upper surface 3Ba and the bottom of the discharge groove 3E is preferably 0.05 to 0.20 mm. Thereby, the slurry or the like is maintained in a state of being appropriately accumulated on the upper surface 3Ba of the end point detection window 3 until it is discharged from the discharge groove 3E, and it is possible to prevent the intensities of the inspection light L1 and the reflected light L2 from decreasing along with the flow of the slurry or the like. As a result, it is possible to prevent the end point detection accuracy by the detection mechanism 7 from decreasing.

[0012] Next, an embodiment of the manufacturing method of the polishing pad 3 configured as described above will be described with reference to FIG. 5. That is, first, a mixture obtained by mixing a polyisocyanate and a curing agent, which are materials for the end point detection window 3, and centrifugally defoaming is prepared, poured into a cylindrical mold, and cured to form the column portion 102. Subsequently, the column portion 102 is arranged at a predetermined position in a rectangular box-shaped mold 101 so that the axis is in the vertical direction. Next, a mixture 103 is prepared by mixing a polyisocyanate, a curing agent, and hollow fine particles for forming a foamed structure, which are materials for the polishing layer 3C, and the mixture 103 is poured into the mold 101 and solidified (see FIG. 5(a)). Thus, a block-shaped polyurethane-polyurea resin molded body 104 following the internal space of the mold 101 is formed (see FIG. 5(b)). This polyurethane-polyurea resin molded body 104 becomes the portion of the polishing layer 3C described above. After that, after removing the polyurethane-polyurea resin molded body 104 from the mold 101, the portion where the column portion 102 is embedded in the polyurethane-polyurea resin molded body 104 is thinly cut along a horizontal plane so as to have a required thickness, and cut out as a sheet-like member 107 (see FIG. 5(c)). Subsequently, the sheet-like member 107 is ground (buffing) from the perspective of thickness correction and formation of fine unevenness (texturing) on the surface that will become the polishing surface 3A as needed. Then, a double-sided tape or the like is attached to the lower surface of the polishing layer 3C on the side opposite to the polishing surface 3A of the sheet-like member 107 (polishing layer 3C). Thereafter, the plurality of annular grooves 3Aa are formed by cutting at positions concentric with the polishing surface 3A of the polishing layer 3C (sheet-like member 107). After that, a counterbore process is performed on the upper surface portion of the cylindrical portion 102 so that it has the same dimension as the diameter of the cylindrical portion 102 and a predetermined depth. And a linear discharge groove 3E that reaches the outer peripheral edge (outer peripheral portion) of the polishing layer 3C from the end point detection window 3B toward the radially outer side is formed by cutting. Then, a support layer 3D (cushion layer) in which a through hole 3Da has been previously formed is adhered to the lower surface of the polishing layer 3C with an adhesive or a double-sided tape. Finally, the laminate of the sheet-like member 107 (polishing layer 3C) and the support layer 3D is cut into a disc shape. Thereby, the polishing pad 3 of the present embodiment is completed (see Fig. 5(d)). The polishing pad 3 manufactured in this way is such that its lower surface (the lower surface of the support layer 3D) is fixed to the upper surface 4A of the polishing surface plate 4 by a double-sided tape, an adhesive, or the like. In addition, in the present embodiment, although it is a manufacturing method in which the cylindrical portion 102 that will later become the end point detection window 3B is manufactured in advance, it is not limited to this. As another example, a desired polishing layer can also be manufactured by pouring and solidifying the material constituting the end point detection window 3B into a polyurethane-polyurea resin molded body 104 with a hole. Specifically, a cylindrical extraction member is arranged at a predetermined position of the mold 101 so that its axis is in the vertical direction, and a mixture 103 prepared by mixing a polyisocyanate and a curing agent, which are materials for the polishing layer 3C, is poured into the mold 101 and solidified to form a polyurethane-polyurea resin molded body 104. Subsequently, the cylindrical extraction member is extracted upward from the formed polyurethane-polyurea resin molded body 104 to form a cylindrical bottomed hole, and a mixture obtained by mixing a polyisocyanate and a curing agent, which are materials for the end point detection window 3B, is poured into the bottomed hole and cured. A transparent cylindrical portion 102 that will later become the end point detection window 3B is formed by the cured mixture. As a result, a polyurethane-polyurea resin molded body 104 in which the cylindrical portion 102 is embedded in the bottomed hole without any gaps is completed. After the step of cutting out the sheet-like member from the polyurethane-polyurea resin molded body 104, it can be produced by the same method as described above. As another example, the cylindrical portion 102 is cut to a predetermined thickness, and the cut cylindrical portion is fitted into a through hole formed by drilling in the polishing layer 3C to the same size as the cylindrical portion 102, whereby a desired polishing layer can be produced. Specifically, the cylindrical portion 102 and the polyurethane-polyurea resin molded body 104 are produced in advance. A sheet-like member 107 is cut out from the polyurethane-polyurea resin molded body 104. The surface of the cut-out sheet-like member 107 is ground, a double-sided tape is attached to the back surface, and an annular groove 3Aa is formed. Then, a through hole having the same size as the cylindrical portion 102 is formed in the sheet-like member 107. On the other hand, the cylindrical portion 102 is cut to a predetermined thickness, and the cylindrical portion 102 is fitted into the through hole of the sheet-like member 107. As a result, a polishing layer 3C having an end point detection window 3B can be produced. After the step of bonding the support layer 3D to the polishing layer 3C, it can be produced by the same method as described above. In this example, a desired polishing layer can be produced without performing counterboring. Furthermore, as another example, the materials of the polishing layer 3C and the end point detection window 3B of this third embodiment are basically the same as those of the first embodiment shown in FIG. 5 above, but the polishing pad 3 composed of the polishing layer 3C and the support layer 3D is manufactured as follows. That is, after manufacturing the polishing pad so that the polishing layer 3C and the support layer 3D are in a stacked state, a through hole is drilled from the surface side (upper surface side) of the polishing pad, and the through hole is counterbored from the back surface side (lower surface side) of the polishing pad to expand the diameter up to the support layer 3D to form a hole, and the hole and the through hole are made to communicate with each other. Then, an annular groove 3Aa and a discharge groove 3E are formed on the surface of the polishing pad. Separately, the manufactured stepped cylindrical end point detection window 3B is fitted into the hole and the through hole without any gaps from the back surface side (lower surface side). Then, the whole is thermally pressed to bond the whole, and then the upper surface of the end point detection window 3B is counterbored by a predetermined dimension to form a recess 3Ca. In addition, the end point detection window 3B in this embodiment is made using a polyisocyanate and a curing agent. However, as the polyisocyanate, a urethane prepolymer previously prepared with a polyol or the like can also be used. Further, as the curing agent, known diols, polyols, diamines, and polyamines can be used. In order to form a foamed structure, hollow fine particles are used, but chemical foaming agents such as water or inert gases can also be used. Furthermore, in this embodiment, after forming the annular groove 3Aa, a counterboring process is performed to form the recess 3Ca, and then the discharge groove 3E is formed. However, the order of the process of forming the recess 3Ca and the process of forming the discharge groove 3E may be reversed.

[0013] As described above, in the polishing pad 3 of this embodiment, a discharge groove 3E extending radially outward from the upper surface 3Ba of the end point detection window 3B and the recess 3Ca is formed on the polishing surface 3A. Therefore, during the polishing process, the slurry and polishing debris are discharged from the upper surface 3Ba of the end point detection window 3B and the recess 3Ca to the discharge groove 3E, and it is possible to prevent the slurry and polishing debris from staying on the upper surface 3Ba of the end point detection window 3B and the recess 3Ca, and to suppress a change in the transmission condition when the inspection light L1 and the reflected light L2 irradiated from the detection mechanism 7 pass through the end point detection window 3B. Therefore, it is possible to prevent the accuracy of end point detection by the detection mechanism 7 from being reduced by the slurry or the like.

[0014] Next, FIG. 6 shows a second embodiment of the present invention. In this second embodiment, grid-shaped discharge grooves 13E are formed at equal pitches (35 mm) vertically and horizontally over the entire polishing surface 3A. The vertical and horizontal discharge grooves 13E intersect at the position (recess 3Ca) of the upper surface 3Ba of the end point detection window 3B. Since both ends of each of the linear discharge grooves 13E forming the grid shape open to the outer peripheral edge (outer peripheral portion) of the polishing layer 3C, the upper surface 3Ba of the end point detection window 3B and the recess 3Ca communicate with the outer peripheral edge through the discharge groove 13E. The width of the discharge groove 13E is set to 2.0 mm, and the depth is set to 0.6 mm. Further, the depth from the polishing surface 3A to the upper surface 3Ba of the end point detection window 3B is set to 0.8 mm. Other configurations are the same as those of the polishing pad 3 of the first embodiment described above, and the same reference numerals are assigned to the corresponding parts as those of the first embodiment. In addition, the materials of the polishing layer 3C and the end point detection window 3B of the second embodiment and the manufacturing process of the polishing pad 3 are basically the same as those of the first embodiment described with reference to FIG. 5 above. Also in this second embodiment, since the upper surface 3Ba and the concave portion 3Ca of the end point detection window 3B communicate with the outer peripheral edge of the polishing surface 3A through the discharge groove 13E, slurry and polishing debris during polishing are discharged outward of the polishing surface 3A through the discharge groove 13E. Therefore, the same operations and effects as those of the first embodiment can be obtained by the polishing pad 3 of this second embodiment. In the second embodiment, the discharge groove 13E is formed substantially orthogonal or substantially parallel to the annular groove 3Aa, but is not limited thereto. The discharge groove 13E may be formed at a predetermined angle, such as 30°, 45°, 60°, etc., with respect to the annular groove 3Aa.

[0015] Next, FIG. 7 shows a third embodiment of the present invention. In this third embodiment, on the premise of the first embodiment shown in FIGS. 3 and 4 above, linear discharge grooves 23E are added on both sides in the circumferential direction of the radial discharge groove 3E. These discharge grooves 23E are formed at an angle of 45° with respect to the radial discharge groove 3E. The inner ends of the discharge grooves 23E communicate with the upper surface 3Ba and the concave portion 3Ca of the end point detection window 3B, and the outer ends open to the outer peripheral edge (outer peripheral portion) of the polishing layer 3C. Also, the width and depth of the discharge groove 23E are set to the same dimensions as the width and depth of the radial discharge groove 3E. Other configurations are the same as those of the polishing pad 3 of the first embodiment described above, and the same reference numerals are assigned to the corresponding parts as those of the first embodiment. In the polishing pad 3 of this third embodiment, the upper surface 3Ba of the end point detection window 3B, the concave portion 3Ca, and the outer peripheral edge of the polishing surface 3A communicate with each other through the three discharge grooves 3E and 23E. Therefore, during polishing, the slurry and polishing debris are efficiently discharged outward from the polishing surface 3A through the discharge grooves 3E and 23E. As a result, it is possible to prevent the slurry and polishing debris from staying on the upper surface 3Ba of the end point detection window 3B. Therefore, the polishing pad 3 of this third embodiment can also obtain the same operations and effects as those of the first embodiment.

[0016] In addition, in each of the above embodiments, the description has been made on the premise that the center of the plurality of annular grooves 3Aa provided at the positions on the concentric circles coincides with the center of the polishing surface 3A. However, a configuration in which the center of the annular groove 3Aa is eccentric with respect to the center of the polishing surface 3A may also be used.

Explanation of Reference Numerals

[0017] 1... Polishing apparatus 2... Workpiece to be polished (wafer) 3... Polishing pad 3A... Polishing surface 3B... End point detection window 3C... Polishing layer 3Ba... Upper surface 3E, 13E, 23E... Discharge groove 7... Detection mechanism L1... Inspection light

Claims

1. In a polishing pad having a polishing layer with a polishing surface for polishing an object to be polished and a transparent end point detection window provided in the polishing layer for detecting an end point during polishing, One surface on the polishing surface side in the end point detection window is formed to be lower in height than the polishing surface, and a recess is formed between the surface and the polishing surface. Furthermore, at least one discharge groove communicating from the recess to the outer peripheral edge of the polishing surface is formed on the polishing surface. A polishing pad, characterized in that slurry and polishing debris during polishing are discharged outward from the polishing surface through the discharge groove via the recess.

2. A plurality of annular grooves are formed at positions on concentric circles of the polishing surface. The discharge groove is provided intersecting the annular groove. The polishing pad according to claim 1, characterized in that one surface on the polishing surface side in the end point detection window is lower in height than the bottom of the annular groove.

3. The polishing pad according to claim 2, characterized in that the bottom of the discharge groove is at the same height as or lower than the bottom of the annular groove and higher in height than one surface on the polishing surface side in the end point detection window.

4. The polishing pad according to claim 3, characterized in that the difference between the depth from the polishing surface to one surface on the polishing surface side in the end point detection window and the depth of the discharge groove is 0.05 to 0.20 mm.

5. The polishing pad according to any one of claims 1 to 4, characterized in that the discharge groove on the polishing surface has a first discharge groove formed radially from the recess and a second discharge groove formed at a predetermined angle with respect to the first discharge groove.

6. A lattice-shaped groove formed by intersecting a plurality of linear grooves is formed on the polishing surface. The polishing pad according to any one of claims 1 to 4, characterized in that at least one linear groove constituting the lattice-shaped groove is provided intersecting the recess of the end point detection window, and the one linear groove serves as the discharge groove.

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