Polishing Pad

Abstract

To prevent deterioration in endpoint detection accuracy by an endpoint detection window while suppressing an influence on polishing performance.SOLUTION: A polishing pad 3 includes an endpoint detection window 12 into which inspection light L1 can permeate, and a polishing surface 3A of the polishing pad 3 is formed with a plurality of concentric circular annular grooves 11. The surface of the endpoint detection window 12 is formed at the same height as the polishing surface 3A. Among the annular grooves 11, the plurality of annular grooves 11A formed in the same radial positions as a position where the endpoint detection window 12 is formed include end parts 11a in the vicinity of the endpoint detection window 12 without forming grooves on the surface of the endpoint detection window 12. The end parts 11a and the end parts 11a of the plurality of annular grooves 11A formed in the same radial positions as the endpoint detection window 12 are connected by connection grooves 13.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a polishing pad, and more particularly to a polishing pad having a transparent end point detection window for detecting the end point of a polishing process. [Background technology]

[0002] 2. Description of the Related Art Polishing pads that are provided with a transparent end point detection window for detecting the end point of polishing and have concentric annular grooves formed on the polishing surface are known (see, for example, Patent Document 1). In the polishing pad of Patent Document 1, the surface of the end point detection window is formed at the same height as the polishing surface, and the annular groove is formed so as to intersect with the end point detection window (particularly the configuration in Figure 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-182667 A Summary of the Invention [Problem to be solved by the invention]

[0004] Here, the annular groove formed in the polishing pad has a function of holding the slurry in the annular groove, but polishing debris and the like generated during polishing also get into this annular groove. Therefore, in the case of the polishing pad of Patent Document 1, if polishing debris or the like gets into the annular groove formed in the end point detection window, the polishing debris or the like will get between the end point detection window and the workpiece being polished, and the inspection light passing through the end point detection window will be blocked by the polishing debris or the like, which may reduce the accuracy of end point detection. In the case of the polishing pad of Patent Document 1, a groove is formed in the end point detection window, so there is a risk that the amount of inspection light transmitted through the annular groove will differ from that through the areas other than the annular groove. Conversely, in order to prevent the inspection light from passing through the groove formed in the end point detection window, the end point detection window needs to be made larger, so there is a possibility that the end point detection window will affect the polishing performance. In view of these problems, the present invention provides a polishing pad that can prevent a decrease in the accuracy of endpoint detection by the endpoint detection window while minimizing the effect on polishing performance. [Means for solving the problem]

[0005] In view of the above circumstances, the present invention teeth, A polishing pad comprising: a polishing layer having a polishing surface for polishing an object to be polished; a transparent end point detection window provided in the polishing layer for transmitting inspection light from a detection mechanism to detect an end point of a polishing process; and a plurality of concentric annular grooves provided on the polishing surface of the polishing layer, forming a surface of the end point detection window at the same height as the polishing surface; Among the annular grooves, a plurality of annular grooves formed at the same radial position as the position where the end point detection window is formed have an end portion near the end point detection window without a groove being formed on the surface of the end point detection window, The ends of a plurality of annular grooves formed at the same radial positions as the end point detection windows are connected by connecting grooves. There is Among the annular grooves formed at the same radial position as the end point detection window, at least one of the annular grooves located on the outermost or innermost side in the radial direction has an arc-shaped connection between the end of the annular groove and the connecting groove. It is characterized by: Effect of the Invention

[0006] According to the above invention, with regard to the annular groove formed at the same radial position as the position where the end point detection window is formed, the ends are connected by the connecting groove, so that polishing debris that has moved to the end of the annular groove can be moved radially outward by the connecting groove, thereby minimizing the polishing debris from entering between the end point detection window and the workpiece to be polished. Furthermore, since no grooves are formed in the end point detection window, the effect of polishing debris can be reduced and the amount of inspection light transmitted through the end point detection window can be made equal at all positions of the end point detection window, so that the area in which the end point detection window is formed can be made as small as possible, thereby minimizing the effect of the end point detection window on polishing. [Brief description of the drawings]

[0007] [Figure 1] FIG. [Diagram 2] FIG. 2 is a cross-sectional view of a main part of FIG. [Diagram 3] FIG. 2 is an enlarged plan view of the polishing pad according to the first embodiment. [Figure 4] 4A to 4C are diagrams showing the manufacturing process of the polishing pad of FIG. 3. [Diagram 5] FIG. 11 is an enlarged plan view of a polishing pad according to a second embodiment. [Figure 6] FIG. 11 is an enlarged plan view of a polishing pad according to a third embodiment. [Figure 7] FIG. 13 is an enlarged plan view of a polishing pad according to a fourth embodiment. [Figure 8] FIG. 13 is an enlarged plan view of a polishing pad according to a fifth embodiment. [Figure 9] FIG. 13 is an enlarged plan view of a polishing pad according to a sixth embodiment. [Figure 10] FIG. 13 is an enlarged plan view of a polishing pad according to a seventh embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] 1 and 2, reference numeral 1 denotes a polishing apparatus that polishes a thin plate-like object to be polished 2 (e.g., a semiconductor wafer) with a polishing pad 3. When polishing the object to be polished 2, the polishing apparatus 1 irradiates an inspection light L1 toward a surface 2A of the object to be polished 2, thereby making it possible to detect the progress of the polishing and the end point of the polishing. The polishing apparatus 1 is equipped with a polishing platen 4 located on the lower side and having a polishing pad 3 fixed on its upper surface, a holding platen 5 located on the upper side and holding the workpiece 2 to be polished on its lower surface, a slurry supply mechanism 6 that supplies slurry S (polishing liquid) between the workpiece 2 to be polished and the polishing pad 3, and a detection mechanism 7 that uses an inspection light L1 to detect the progress of polishing of the workpiece 2 and the end point of the processing. The object 2 to be polished by the polishing apparatus 1 is an optical material, a silicon wafer, a glass substrate for liquid crystal, a semiconductor substrate, and a plate-like object such as glass, metal, ceramic, etc. As the slurry S to be supplied by the slurry supply mechanism 6, a suitable conventionally known material can be used depending on the object 2 to be polished and the required processing accuracy. The polishing platen 4 and the holding platen 5 are each substantially disk-shaped and are adapted to rotate in the direction of the arrow by a drive mechanism (not shown), and the holding platen 5 is provided so as to be movable up and down. When polishing the object 2, the holding platen 5 presses the polished surface 2A (lower surface) of the object 2 against the polishing surface 3A of the polishing pad 3 at a set pressure while they are rotated relative to each other, and a slurry S is supplied from a slurry supply mechanism 6 between the polished surface 2A of the object 2 and the polishing surface 3A of the polishing pad 3. A plurality of annular grooves 11 are formed at equal pitches in the radial direction concentrically around the center (center of rotation) of the polishing pad 3 on the polishing surface 3A of the polishing pad 3. These plurality of annular grooves 11 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 11 and is supplied to the entire area of ​​the polishing surface 3A.

[0009] Incidentally, when polishing the workpiece 2, it is necessary to detect the progress of the polishing of the workpiece 2 and the end point of the polishing. Therefore, the polishing device 1 is provided with a detection mechanism 7 that irradiates an inspection light L1 from below toward above and detects the progress of the polishing and the end point of the polishing based on the reflected light L2 from the polished surface 2A of the workpiece 2. At a predetermined position on the polishing pad 3, a transparent window 12 for detecting an end point is provided, which transmits the inspection light L1 and also transmits reflected light L2 from the surface 2A of the workpiece 2 to be polished. The polishing pad 3 has a disk shape and comprises a polishing layer 3C located on the upper side and a support layer 3D (cushion layer) adhered to the underside of the polishing layer 3C with an adhesive. The polishing layer 3C has an end point detection window 12 provided at a predetermined position, and the support layer 3D has a through hole 3Da drilled therein to allow the inspection light L1 and the reflected light L2 from the workpiece 2 to pass therethrough in accordance with the position of the end point detection window 12. The lower surface of the polishing layer 3C is bonded to the upper surface of the support layer 3D with an adhesive or double-sided tape, and the polishing pad 3 consisting of the polishing layer 3C and the support layer 3D integrated together has its lower surface (the lower surface of the support layer 3D) fixed to the upper surface of the polishing table 4 with an adhesive or double-sided tape. The end point detection window 12 is made of a transparent material that transmits the inspection light L1 and the reflected light L2, and is fitted tightly into a through hole formed at a predetermined position in the polishing layer 3C. The diameter of the end point detection window 12 in this embodiment is set to 12 mm. In this embodiment, the shape of the end point detection window 12 in a plan view is circular, but it may be various other shapes, such as a rectangle, a square, a polygon, or an ellipse. The upper surface of the end point detection window 12 is flush with the polishing surface 3A, which is the upper surface of the polishing layer 3C, while the lower surface of the end point detection window 12 is also flush with the lower surface of the polishing layer 3C.

[0010] As the inspection mechanism 7, the polishing table 4 is provided with a light-emitting unit 7A that irradiates inspection light L1 upward and a light-receiving unit 7B that receives reflected light L2 from the workpiece 2, at a position below the end point detection window 12 of the polishing pad 3 and the through hole 3Da of the support layer 3D, and is equipped with a control unit 7C that controls the operation of these units and detects the progress of the polishing process and the end point at which the process ends. During the polishing process of the workpiece 2, inspection light L1 is emitted upward from the light emitting unit 7A of the inspection mechanism 7, and the inspection light L1 passes through the transparent end point detection window 12 and is irradiated onto 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 12 and is detected by the light receiving unit 7B. The reflected light L2 detected by the light receiving unit 7B is transmitted to the control unit 7C. As the polishing of the workpiece 2 progresses and the polishing surface 2A of the workpiece 2 is gradually polished, the intensity of the reflected light L2 detected by the light receiving unit 7B changes. When the intensity of the reflected light L2 detected by the light receiving unit 7B reaches a preregistered intensity, the control unit 7C determines that the polishing surface 2A has reached the end point of polishing, and stops the polishing. Then, the drive mechanism is stopped, so that 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 is also stopped. In this way, the end point of polishing can be detected by using the inspection light L1 of the inspection mechanism 7 when polishing the workpiece 2. The configuration of the detection mechanism 7 using the inspection light L1 is already known.

[0011] As described above, a plurality of annular grooves 11 are concentrically formed on the polishing surface 3A. In this embodiment, the width of each annular groove 11 is set to 0.4 mm, the pitch between adjacent annular grooves 11 is set to 2.8 mm, and the depth of each annular groove 11 is set to 0.6 mm. When the concentric annular grooves 11 are formed in this manner, since the polishing pad 3 of this embodiment has the end point detection window 12 formed therein, multiple of the annular grooves 11 are formed at the same radial position as the end point detection window 12, i.e., at a position where the distance from the center of the annular groove 11 is equal to that of the end point detection window 12. FIG. 3 shows an enlarged plan view of the vicinity of the end point detection window 12. In FIG. 3, an annular groove 11A formed at the same radial position as the end point detection window 12 is not formed on the surface of the end point detection window 12 and has an end portion 11a in the vicinity of the end point detection window 12. In contrast, the annular grooves 11 at a different radial position from the end point detection window 12, i.e., the annular grooves 11 located on the larger and smaller radial sides of the end point detection window 12, are formed endlessly without the above-mentioned end portion 11a. The polishing pad 3 of this embodiment is characterized in that the ends 11a of multiple annular grooves 11A formed at the same radial position as the end point detection window 12 are connected by a connecting groove 13 formed in an approximately radial direction. In particular, in this embodiment, the annular groove 11A at the same radial position as the end point detection window 12 has its ends 11a aligned radially, so that the connecting groove 13 is formed in a straight line extending radially. Here, the width of the connecting groove 13 may be the same as the width of the annular groove 11A, but as will be described later, the width of the connecting groove 13 can also be narrowed or widened depending on the purpose of discharging the polishing debris in the slurry S. The cross-sectional shape of the connecting groove 13 may be rectangular like the annular groove 11A, but it may also be tapered, such as V-shaped or trapezoidal, widening toward the workpiece, or may have chamfered corners on the polishing surface 3A side of the vertically formed inner wall of the connecting groove 13. In particular, when the connecting groove 13 has a tapered shape such as V-shaped or trapezoidal, burrs are less likely to occur on the inner wall of the connecting groove 13, and slurry and polishing chips are less likely to remain in the connecting groove 13.

[0012] In this way, the polishing pad 3 of this embodiment prevents the accuracy of endpoint detection from being reduced by polishing debris generated during polishing of the workpiece 2 by connecting the ends 11a of the multiple annular grooves 11A formed at the same radial position as the endpoint detection window 12 via the connecting groove 13. As described above, the polishing pad 3 of this embodiment has multiple annular grooves 11, and the annular grooves 11A hold the slurry S during polishing, thereby supplying an appropriate amount of slurry S between the workpiece 2 and the polishing surface 3A of the polishing pad 3. On the other hand, polishing debris generated when the workpiece 2 is polished also enters the annular groove 11A together with the slurry S. If this polishing debris enters between the workpiece 2 and the end point detection window 12, which is formed flush with the polishing surface 3A, the intensity of the inspection light L1 and the reflected light L2 passing through the end point detection window 12 decreases, which may reduce the accuracy of end point detection. Therefore, in the polishing pad 3 of this embodiment, for the multiple annular grooves 11A formed at the same radial position as the end point detection window 12, no grooves are formed on the surface of the end point detection window 12, and the ends 11a of these annular grooves 11A are connected to each other by the connecting groove 13. According to this configuration, first, a groove is not formed in the end point detection window 12, so that polishing debris does not get into between the end point detection window 12 and the workpiece 2 through the groove, and there is no change in the amount of transmission of the inspection light L1 between the groove and parts other than the groove. Next, by forming the connecting groove 13, the polishing chips that have entered the annular groove 11A are discharged between the polishing surface 3A and the workpiece 2 via the connecting groove 13 when they move to the end portion 11a. At this time, the polishing pad 3 rotates during polishing and centrifugal force acts on the radially outer periphery, so that the polishing chips that have entered the connecting groove 13 can be moved to the radially outer periphery and discharged. In particular, since the connecting groove 13 is located adjacent to the end point detection window 12, by discharging polishing debris from the connecting groove 13, it is possible to reduce the amount of debris getting between the end point detection window 12 and the object to be polished 2, thereby suppressing fluctuations in the intensity of the inspection light L1 and the reflected light L2 that pass through the end point detection window 12, and maintaining the accuracy of end point detection.

[0013] Next, one embodiment of a method for manufacturing the polishing pad 3 configured as above will be described with reference to FIG. That is, first, a mixture of polyisocyanate and a curing agent, which are materials for the end point detection window 12, is prepared by mixing them and degassing them by centrifugation, and the mixture is poured into a cylindrical mold and cured to form the columnar portion 102. Next, the columnar portion 102 is placed at a predetermined position in a rectangular box-shaped mold 101 so that its axis is vertical (see FIG. 4(a)). Next, polyisocyanate, a hardener, and hollow fine particles, which are the materials for the polishing layer 3C, are mixed to prepare a mixture 103, which is then poured into the mold 101 and hardened (see FIG. 4(a)), forming a block-shaped polyurethane polyurea resin molded body 104 conforming to the internal space of the mold 101 (see FIG. 4(b)). This polyurethane polyurea resin molded body 104 becomes the polishing layer 3C described above. Thereafter, the polyurethane polyurethane resin molding 104 is removed from the formwork 101, and the portion of the polyurethane polyurethane resin molding 104 where the cylindrical portion 102 is embedded is thinly cut along a horizontal plane to the required thickness to cut out as a sheet-like member 107 (see FIG. 4(c)). Thereafter, the sheet-like member 107 is ground (buffed) to be smooth, if necessary, from the viewpoint of correcting the thickness and forming fine irregularities (sharpening) (see FIG. 4(c)). Thereafter, the plurality of annular grooves 11 are formed by cutting on the polishing surface 3A of the sheet-like member 107, and in this case, for the annular groove 11A located at the same radial position as the end point detection window 12, the end 11a is formed near the end point detection window 12, and the end 11a and the end 11a are connected by the connecting groove 13. This completes the polishing layer 3C of the polishing pad 3 shown in Figures 2 and 3. Thereafter, double-sided tape or the like is attached to the underside of the polishing layer 3C opposite the polishing surface 3A, and the support layer 3D (cushion layer) in which the through holes 3Da have been drilled in advance is bonded to the underside of the polishing layer 3C with an adhesive (see Figure 4(d)). Finally, the entire piece is cut into a disk shape to complete the polishing pad 3. The polishing pad 3 thus manufactured has its lower surface (the lower surface of the support layer 3D) fixed to the upper surface 4A of the polishing platen 4 by means of double-sided tape, adhesive or the like.

[0014] In this embodiment, the cylindrical portion 102 that will later become the end point detection window 12 is prepared in advance, but the method is not limited to this. As another example, the desired polishing layer can be prepared by pouring the material that will form the end point detection window 12 into a polyurethane-polyurea resin molded body 104 with a hole and then hardening it. Specifically, a cylindrical extraction member is placed at a predetermined position on the mold 101 with its axis oriented vertically, and a mixture 103 prepared by mixing polyisocyanate, a curing agent, and hollow microparticles, which are the materials for the polishing layer 3C, is poured into the mold 101 and hardened to form a polyurethane polyurethane resin molding 104. Next, the cylindrical extractor is pulled upward from the formed polyurethane polyurea resin molded body 104 to form a cylindrical bottomed hole, and a mixture of polyisocyanate and a hardener, which will be the material for the end point detection window 12, is poured into the bottomed hole and hardened. The hardened mixture forms a transparent cylindrical portion 102 that will later become the end point detection window 12. This completes polyurethane polyurea resin molded body 104 in which cylindrical portion 102 is embedded tightly in the bottomed hole. The steps subsequent to the step of cutting out a sheet-like member from polyurethane polyurea resin molded body 104 can be produced in the same manner as above. In addition, the end point detection window 12 and the polishing layer 3C in this embodiment are made using polyisocyanate and a hardening agent, but a prepolymer made in advance with polyol, etc. can be used instead of polyisocyanate. Furthermore, known diols, polyols, diamines, and polyamines can be used as hardening agents. Furthermore, the polishing layer 3C in this embodiment is formed with a foam structure using hollow fine particles. For the hollow fine particles, hollow fine particles of vinylidene chloride-acrylonitrile copolymer can be used. In addition to the hollow fine particles, chemical foaming agents such as water, inert gases, etc. can be used alone or in combination to form the foam structure.

[0015] Polishing pads 3 according to second to seventh embodiments shown in FIGS. 5 to 10 will be described below. The second embodiment of the polishing pad 3 shown in Figure 5 has an annular groove 11A located at the same radial position as the end point detection window 12, and the connection portion between the annular groove 11A located on the radially outer side of the polishing pad 3 and the connecting groove 13 is made into an arc-shaped portion 13a. In contrast, the polishing pad 3 of the third embodiment shown in Figure 6 has an annular groove 11A located at the same radial position as the end point detection window 12, and the connection portion between the annular groove 11A located on the radially inner side of the polishing pad 3 and the connecting groove 13 is made into an arc-shaped portion 13a. 7, the connecting groove 13 having the straight portion in the second and third embodiments is entirely formed of an arc-shaped portion 13a. Alternatively, the connecting groove 13 may be formed with arc-shaped portions 13a on both the radially inner and outer circumferential sides, with the portion between them being linear. In this manner, by forming the arc-shaped portion 13a at the connection portion between the annular groove 11A and the connecting groove 13, it is possible to prevent slurry and polishing waste from accumulating at the connection portion between the connecting groove 13 and the annular groove 11A.

[0016] The polishing pads 3 of the fifth and sixth embodiments shown in Figures 8 and 9 are different from the polishing pad 3 of the first embodiment in that the connecting groove 13 is extended to an annular groove 11 radially adjacent to the multiple annular grooves 11A formed at the same radial position as the end point detection window 12. Specifically, endless annular grooves 11 without ends 11a are located on the radially outer and inner sides of the end point detection window 12, and the connecting grooves 13 in this embodiment are extended to the annular grooves 11 located on the radially outer and inner sides of the end point detection window 12. In addition, the connecting groove 13 in the fifth embodiment is formed so as to widen radially outward of the polishing pad 3 relative to the end point detection window 12, whereas the connecting groove in the sixth embodiment is formed so as to narrow radially outward of the polishing pad 3 relative to the end point detection window 12. According to the connecting groove 13 of the fifth and sixth embodiments having the above-mentioned configuration, polishing debris that has entered the connecting groove 13 can be moved to the annular groove 11 that is adjacent to the end point detection window 12 in the radial direction. In particular, it becomes possible to move the polishing debris that has entered the connecting groove 13 due to the centrifugal force caused by the rotation of the polishing pad 3 to the endless annular groove 11 on the radially outer periphery, thereby preventing the polishing debris from being discharged onto the polishing surface 3a. In the fifth and sixth embodiments, the connecting groove 13 is formed to extend to the endless annular groove 11 adjacent to the radially outer and inner sides of the end point detection window 12. However, the connecting groove 13 may be formed, for example, by extending to the outer periphery of the polishing pad 3. Furthermore, among the above-mentioned connecting grooves 13, the above-mentioned connecting grooves 13 may not be extended to the annular groove 11 located on the radially inner periphery side of the end-point detection window 12. In other words, since the centrifugal force caused by the rotation of the polishing pad 3 acts radially outward, in order to move the polishing waste radially outward, it is only necessary to extend the connecting grooves 13 radially outward.

[0017] The polishing pad 3 of the seventh embodiment shown in FIG. 10 is different from the polishing pads 3 of the first to sixth embodiments in that the connecting groove 13 is formed in an annular shape along the outer circumferential edge of the end point detection window 12. Specifically, a groove is formed surrounding the end point detection window 12, and this groove serves as the connecting groove 13, connecting the ends 11a of multiple annular grooves 11A formed at the same radial position as the end point detection window 12. Even with the connecting groove 13 having such a configuration, the ends 11a of the multiple annular grooves 11A formed at the same radial position as the end point detection window 12 are connected approximately radially, making it possible for the connecting groove 13 to discharge polishing debris that has entered the annular groove 11A due to centrifugal force.

[0018] In each of the above embodiments, the explanation is based on the assumption that the centers of the multiple annular grooves 11 arranged at concentric positions coincide with the center of the polishing surface 3A, but the center of the annular groove 11 may be eccentric with respect to the center of the polishing surface 3A. [Explanation of symbols]

[0019] 1 Polishing device 2 Object to be polished 3 Polishing pad 3C Polishing layer 7 Detection mechanism 11 Annular groove 11A Annular groove at the same radial position as the end point detection window 11a End 12 End point detection window 13 Connection groove L1 Inspection light

Claims

[Claim 1] A polishing pad comprising: a polishing layer having a polishing surface for polishing an object to be polished; a transparent end point detection window provided in the polishing layer for transmitting inspection light from a detection mechanism to detect an end point of a polishing process; and a plurality of concentric annular grooves provided on the polishing surface of the polishing layer, forming a surface of the end point detection window at the same height as the polishing surface; Among the annular grooves, a plurality of annular grooves formed at the same radial position as the position where the end point detection window is formed have an end portion near the end point detection window without a groove being formed on the surface of the end point detection window, The ends of the plurality of annular grooves formed at the same radial positions as the end point detection windows are connected by connecting grooves, A polishing pad characterized in that, among the annular grooves formed at the same radial position as the end point detection window, the connection portion between the end of at least one of the annular grooves located on the outermost or innermost radial side in the radial direction and the connecting groove is arc-shaped.

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