Polishing pad, polishing apparatus, and polishing method

Abstract

To provide a polishing pad that enables enjoyment of both benefits of forming and not forming a groove in a polishing surface, and further provide a polishing device and a polishing method.SOLUTION: A polishing pad of an aspect of the present invention is a polishing pad attached to a machine platen for pressing the machine platen against a workpiece to polish the workpiece by using a membrane-type polishing head. The polishing pad includes a base nap layer and a projection nap layer thicker than the base nap layer. A height difference between the base nap layer and the projection nap layer is within a range from 250 μm to 280 μm.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a polishing pad, a polishing apparatus, and a polishing method. [Background technology]

[0002] Because flatness is required for the surfaces of materials such as optical materials, semiconductor devices, hard disks, and glass substrates, polishing using a loose abrasive method with a polishing pad is used. The loose abrasive method is a method of polishing the workpiece surface by supplying a slurry (polishing liquid) containing abrasive grains between the polishing pad and the workpiece. In particular, when polishing semiconductor wafers and other materials, high levels of defect-free and flat workpiece characteristics are required, so loose abrasive polishing using a polishing pad is used to ensure flatness, and soft polishing pads are increasingly being used, especially in the finish polishing process.

[0003] When polishing semiconductor wafers or the like using a polishing pad, the polishing surface of the polishing pad may be appropriately processed depending on the polishing head structure used. For example, in the case of a water-filled polishing head, it is preferable to use a polishing pad without grooves on the polishing surface, while in the case of a membrane-type polishing head, it is preferable to use a polishing pad with grooves on the polishing surface. In the case of a water-filled polishing head, although it is difficult to recover the workpiece, a polishing pad without grooves on the polishing surface has an advantage in terms of planarization characteristics. On the other hand, in the case of a membrane-type polishing head, although nanotopography, an index of surface flatness derived from the groove pattern of the polishing pad, deteriorates, it is difficult to recover the workpiece unless grooves are formed on the polishing surface.

[0004] Processing of the polishing surface of a polishing pad includes groove processing, embossing, and hole processing (punching). In CMP technology, it is necessary to stabilize the polishing rate from the viewpoint of improving productivity efficiency and yield (see, for example, Patent Document 1). Furthermore, for the polishing pads used in CMP, it is desirable to increase the number of workpieces that can be processed per pad from the viewpoint of productivity and cost. To increase the number of workpieces that can be processed per pad, it is necessary to suppress the wear of the polishing pad and to suppress a decrease in the polishing rate due to clogging of the polishing pad. It is known that, in order to improve the wear and polishing rate of the polishing pad, grooves are formed on the polishing surface of the polishing pad to allow the flow of polishing slurry (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-51726 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-188987 Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, with a polishing pad having grooves on its polishing surface, the supplied slurry is less likely to be effectively applied to the polishing surface during polishing, resulting in uneven contact and non-contact with the workpiece, and a deterioration in nanotopography, which is an indicator of the workpiece's surface flatness. On the other hand, with a polishing pad without grooves on its polishing surface, the polishing pad adheres to the workpiece, and in the case of a membrane-type polishing head, there is a problem in that the workpiece cannot be recovered.

[0007] In other words, whether or not to form grooves on the polishing surface of the polishing pad has advantages and disadvantages, and there has been a problem in that it is difficult to enjoy the advantages of both options.

[0008] In view of the above-mentioned problems, an object of the present invention is to provide a polishing pad, a polishing apparatus, and a polishing method that can enjoy the advantages of both forming and not forming grooves on the polishing surface. [Means for solving the problem]

[0009] In order to solve the above problems, one embodiment of the polishing pad of the present invention is a polishing pad that is attached to a base platen using a membrane-type polishing head to press a workpiece against the base platen for polishing, and is characterized in that it has a base nap layer and a protruding nap layer that is thicker than the base nap layer, and the difference in height between the base nap layer and the protruding nap layer is in the range of 250 μm to 280 μm.

[0010] As described above, a polishing pad having a height difference between the base nap layer and the front protrusion nap layer in the range of 250 μm to 280 μm functions as if no grooves were formed on the polishing surface during polishing, and functions as if grooves were formed on the polishing surface when the workpiece is retrieved.

[0011] Specifically, when the pressure with which the polishing head presses the workpiece is 10 MPa or more, the difference in height between the base nap layer and the protruding nap layer is in the range of 20 μm to 40 μm; in other words, when the pressure with which the polishing head presses the workpiece is 10 MPa or more, the base nap layer and the protruding nap layer come into contact with the workpiece.

[0012] The base nap layer and the protruding nap layers are preferably made of polyurethane resin, and the thickness of the protruding nap layers is preferably 350 μm or more.

[0013] Furthermore, one embodiment of the polishing apparatus of the present invention comprises a membrane-type polishing head for pressing a workpiece against a base plate to polish it, and a polishing pad attached to the base plate, wherein the polishing pad has a base nap layer and a protruding nap layer that is thicker than the base nap layer, and the height difference between the base nap layer and the protruding nap layer is in the range of 250 μm to 280 μm.

[0014] Similarly, in one embodiment of the polishing apparatus of the present invention, the polishing pad has a height difference between the base nap layer and the front protrusion nap layer in the range of 250 μm to 280 μm, so that during polishing, it functions as if no grooves are formed on the polishing surface, and when the workpiece is recovered, it functions as if grooves are formed on the polishing surface.

[0015] The polishing head is preferably capable of independently controlling a central control pressure for pressing the central portion and a peripheral control pressure for pressing the peripheral portion, in order to adjust the polishing amount and improve flatness.

[0016] The polishing head preferably has a retainer ring on its outer periphery for holding the outer periphery of the workpiece, so that the workpiece does not come off the polishing head when it is slid.

[0017] Furthermore, one embodiment of the polishing method of the present invention is characterized in that a polishing pad having a base nap layer and a protruding nap layer that is thicker than the base nap layer, with the difference in height between the base nap layer and the protruding nap layer being in the range of 250 μm to 280 μm, is attached to a surface plate, and a membrane-type polishing head is used to press a workpiece against the polishing pad to polish it.

[0018] Similarly, in one embodiment of the polishing method of the present invention, the polishing pad has a height difference between the base nap layer and the front protrusion nap layer in the range of 250 μm to 280 μm, so that during polishing, it functions as if no grooves are formed on the polishing surface, and when the workpiece is recovered, it functions as if grooves are formed on the polishing surface.

[0019] Specifically, it is preferable that the workpiece is pressed against the polishing pad so that the difference in height between the base nap layer and the protruding nap layer is in the range of 20 μm to 40 μm during polishing. In other words, it is preferable that the workpiece is pressed against the polishing pad so that the base nap layer and the protruding nap layer contact the workpiece during polishing. For example, this condition can be achieved by the polishing head pressing the workpiece against the polishing pad with a pressure of 10 MPa or more during polishing. [Effects of the Invention]

[0020] According to each aspect of the present invention, it is possible to provide a polishing pad, a polishing apparatus, and a polishing method that can enjoy the advantages of both forming and not forming grooves on the polishing surface. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic view of a polishing apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view showing the configuration of the polishing head. [Figure 3] FIG. 3 is a schematic cross-sectional view of a polishing pad according to an embodiment of the present invention. [Figure 4] FIG. 4 is a schematic cross-sectional view showing the state of the polishing pad during polishing. [Figure 5] FIG. 5 is a schematic cross-sectional view showing the state of the polishing pad when the workpiece is collected. [Figure 6] FIG. 6 is a graph showing the flatness after polishing. [Figure 7] FIG. 7 is a graph showing a comparison of the number of LPDs after single-side polishing. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiments described below. In addition, the same or corresponding elements in each drawing are appropriately designated by the same reference numerals. Furthermore, it should be noted that the drawings are schematic, and the dimensional relationships and ratios of each element may differ from those in reality. There may also be parts in which the dimensional relationships and ratios differ between the drawings.

[0023] FIG. 1 is a schematic diagram of a polishing apparatus according to an embodiment of the present invention. As shown in FIG. 1, the polishing apparatus 100 includes a platen 11 to which a polishing pad 10 is attached and a membrane-type polishing head 20 for pressing a workpiece against the platen 11 to polish it. The workpiece, for example, is a semiconductor wafer, and as will be described later with reference to FIG. 2, the workpiece is held by the polishing head 20 and slid over the polishing pad 10. The sliding between the platen 11 to which the polishing pad 10 is attached and the polishing head 20 can be achieved, for example, by rotating the platen 11 to which the polishing pad 10 is attached while rotating the polishing head 20 about an axis of rotation that is offset parallel to the axis of rotation of the platen 11. Furthermore, polishing may be performed while moving the axis of rotation of the polishing head 20 horizontally.

[0024] FIG. 2 is a schematic cross-sectional view showing the configuration of a polishing head. As shown in FIG. 2, the polishing head 20 is a membrane-type polishing head that uses a membrane 21 to press the workpiece W against a surface plate 11 to which a polishing pad 10 is attached. The outer periphery of the membrane 21 is fixed to a support 23 of the polishing head 20 via an outer ring 22, and an air chamber 24 is formed inside the polishing head 20. The membrane 21 adjusts the pressure with which the workpiece W is pressed against the surface plate 11 to which the polishing pad 10 is attached by adjusting the air pressure in the air chamber 24. It is preferable to divide the air chamber 24 of the polishing head 20 so that the central control pressure that presses the central portion and the peripheral control pressure that presses the peripheral portion can be controlled independently.

[0025] The polishing head 20 also has a retainer ring 25 on its outer periphery for holding the outer periphery of the workpiece W. As described above, the polishing head 20 rotates, for example, on an axis of rotation that is offset parallel to the axis of rotation of the platen 11 while rotating the platen 11 to which the polishing pad 10 is affixed, thereby sliding the workpiece W on the polishing pad 10 affixed to the platen 11. At this time, the retainer ring 25 attached to the outer periphery of the polishing head 20 holds the outer periphery of the workpiece W so that the workpiece W does not come off the polishing pad 10.

[0026] Figure 3 is a schematic cross-sectional view of a polishing pad according to an embodiment of the present invention. As shown in Figure 3, polishing pad 10 is constructed by forming nap layer 13 on substrate 12. Substrate 12 is, for example, a nonwoven fabric, and nap layer 13 is formed of, for example, polyurethane resin. As shown in Figure 3, nap layer 13 is further divided into base nap layer 14 and thicker protruding nap layer 15. Base nap layer 14 can be formed by carving grooves in polyurethane resin nap layer 13. In other words, protruding nap layer 15 is the area of ​​nap layer 13 where no grooves have been carved.

[0027] The thickness of the nap layer 13 formed on the substrate 12, i.e., the thickness W of the protruding nap layer 15, is, for example, 350 μm or more. The height difference D between the base nap layer 14 and the protruding nap layer 15 is in the range of 250 μm to 280 μm. If the height difference D between the base nap layer 14 and the protruding nap layer 15 is greater than 280 μm, the height difference D between the base nap layer 14 and the protruding nap layer 15 will not be sufficiently small during polishing, resulting in uneven polishing. On the other hand, if the height difference D between the base nap layer 14 and the protruding nap layer 15 is less than 280 μm, the workpiece will stick to the polishing pad 10 during recovery after polishing, making recovery of the workpiece difficult.

[0028] FIG. 4 is a schematic cross-sectional view showing the state of the polishing pad during polishing, and FIG. 5 is a schematic cross-sectional view showing the state of the polishing pad when the workpiece is collected.

[0029] As shown in Figure 4, the protruding nap layer 15 of the polishing pad 10 is compressed by pressing the workpiece W against the polishing pad 10 during polishing. As a result, the height difference between the base nap layer 14 and the protruding nap layer 15 in the polishing pad 10 during polishing is in the range of 20 μm to 40 μm. This brings the base nap layer 14 and the protruding nap layer 15 into contact with the workpiece W, allowing for polishing to be performed with a flat surface comparable to that of a polishing pad without grooves on the polishing surface. Specifically, when the polishing head 20 presses the workpiece W against the polishing pad 10 with a pressure of 10 MPa or more during polishing, the height difference between the base nap layer 14 and the protruding nap layer 15 is in the range of 20 μm to 40 μm.

[0030] On the other hand, as shown in Figure 5, when the pressure applied to the workpiece W is released during recovery of the workpiece W, the compression of the protruding nap layer 15 of the nap layer 13 of the polishing pad 10 is also released. As a result, the difference in height between the base nap layer 14 and the protruding nap layer 15 becomes at least 40 μm. This makes it easier to recover the workpiece W, just like a polishing pad with grooves formed in the polishing surface. During recovery, the pressure with which the polishing head 20 presses the workpiece W against the polishing pad 10 is set to a pressure lower than 10 MPa, so that the difference in height between the base nap layer 14 and the protruding nap layer 15 becomes greater than 40 μm.

[0031] Figure 6 is a graph showing the flatness after polishing. The graph in Figure 6 shows the flatness of a wafer polished according to the present invention and the flatness of a wafer polished using a polishing pad with conventional grooves as a comparative example. As can be seen from the graph in Figure 6, in polishing according to the present invention, even though the polishing pad has grooves, the base nap layer and the protruding nap layer come into contact with the wafer during polishing, and polishing can be performed to a flatness equivalent to that of a polishing pad without grooves on the polishing surface. On the other hand, as can be seen from the graph in Figure 6, when polishing is performed using a polishing pad with grooves, non-uniformity in flatness occurs due to the grooves.

[0032] Figure 7 is a graph showing a comparison of the number of LPDs after single-sided polishing. The graph shown in Figure 7 shows the number of LPDs (Light Point Defects) on wafers that were subjected to single-sided polishing according to the present invention, and the number of LPDs on wafers that were polished using a polishing pad with normal grooves formed therein as a comparative example. As can be seen from the graph shown in Figure 7, the number of LPDs was reduced by 27% in the polishing according to the present invention compared to the comparative example.

[0033] As described above, the polishing pad, polishing apparatus, and polishing method according to the embodiments of the present invention function as if no grooves were formed on the polishing surface during polishing, and function as if grooves were formed on the polishing surface when the workpiece is recovered, thereby providing the benefits of both forming and not forming grooves on the polishing surface. [Explanation of symbols]

[0034] 100 Polishing equipment 10 Polishing Pads 11 Surface Plate 12 Base material 13. Nappe layer 14 Underlying nap layer 15 Protruding nap layer 20 Polishing Head 21 Membrane 22 Outer Ring 23 Support 24 air chambers 25 Retainer ring double work

Claims

1. A polishing pad that is attached to a surface plate to polish a workpiece by pressing it against the surface plate using a membrane-type polishing head, a nap layer including a plurality of base nap layers and a plurality of protruding nap layers that are thicker than the base nap layers and protrude from the surface when the base nap layer is attached to the surface plate; the plurality of base nap layers are alternately adjacent to the plurality of protruding nap layers and together with the plurality of protruding nap layers form a surface of the nap layer; A polishing pad characterized in that the difference in height between the base nap layer and the protruding nap layer is in the range of 250 μm to 280 μm, and when the pressure with which the polishing head presses the workpiece against the polishing pad is 10 MPa or more, the difference in height between the base nap layer and the protruding nap layer is in the range of 20 μm to 40 μm.

2. A polishing pad that is attached to a surface plate to polish a workpiece by pressing it against the surface plate using a membrane-type polishing head, a nap layer including a plurality of base nap layers and a plurality of protruding nap layers that are thicker than the base nap layers and protrude from the surface when the base nap layer is attached to the surface plate; the plurality of base nap layers are alternately adjacent to the plurality of protruding nap layers and together with the plurality of protruding nap layers form a surface of the nap layer; A polishing pad characterized in that the difference in height between the base nap layer and the protruding nap layer is in the range of 250 μm to 280 μm, and when the pressure with which the polishing head presses the workpiece is 10 MPa or more, the base nap layer and the protruding nap layer come into contact with the workpiece.

3. 3. The polishing pad according to claim 1, wherein the base nap layer and the protruding nap layers are formed of a polyurethane resin.

4. 4. The polishing pad according to claim 1, wherein the protruding nap layer has a thickness of 350 [mu]m or more.

5. a membrane-type polishing head for pressing the workpiece against the surface plate to polish it; a polishing pad attached to the surface plate; the polishing pad has a nap layer composed of a plurality of base nap layers and a plurality of protruding nap layers that are thicker than the plurality of base nap layers and protrude from the surface when the polishing pad is attached to the platen; the plurality of base nap layers are alternately adjacent to the plurality of protruding nap layers and together with the plurality of protruding nap layers form a surface of the nap layer; A polishing apparatus characterized in that the difference in height between the base nap layer and the protruding nap layer is in the range of 250 μm to 280 μm, and when the pressure with which the polishing head presses the workpiece against the polishing pad is 10 MPa or more, the difference in height between the base nap layer and the protruding nap layer is in the range of 20 μm to 40 μm.

6. a membrane-type polishing head for pressing the workpiece against the surface plate to polish it; a polishing pad attached to the surface plate; the polishing pad has a nap layer composed of a plurality of base nap layers and a plurality of protruding nap layers that are thicker than the plurality of base nap layers and protrude from the surface when the polishing pad is attached to the platen; the plurality of base nap layers are alternately adjacent to the plurality of protruding nap layers and together with the plurality of protruding nap layers form a surface of the nap layer; A polishing apparatus characterized in that the difference in height between the base nap layer and the protruding nap layer is in the range of 250 μm to 280 μm, and when the pressure with which the polishing head presses the workpiece against the polishing pad is 10 MPa or more, the base nap layer and the protruding nap layer come into contact with the workpiece.

7. 7. The polishing apparatus according to claim 6, wherein the polishing head is capable of independently controlling a central control pressure for pressing the central portion and a peripheral control pressure for pressing the peripheral portion.

8. a polishing pad having a nap layer composed of a plurality of base nap layers and a plurality of protruding nap layers that are thicker than the base nap layers and protrude onto the surface when the pad is attached to the surface, the base nap layers being alternately adjacent to the protruding nap layers and forming the surface of the nap layer together with the protruding nap layers, and the height difference between the base nap layers and the protruding nap layers being in the range of 250 μm to 280 μm, the polishing pad being attached to the surface; A polishing method characterized by using a membrane-type polishing head to press the workpiece against the polishing pad so that the height difference between the base nap layer and the protruding nap layer is in the range of 20 μm to 40 μm during polishing.

9. a polishing pad having a nap layer composed of a plurality of base nap layers and a plurality of protruding nap layers that are thicker than the base nap layers and protrude onto the surface when the pad is attached to the surface, the base nap layers being alternately adjacent to the protruding nap layers and forming the surface of the nap layer together with the protruding nap layers, and the height difference between the base nap layers and the protruding nap layers being in the range of 250 μm to 280 μm, the polishing pad being attached to the surface; A polishing method comprising pressing the workpiece against the polishing pad using a membrane-type polishing head so that the base nap layer and the protruding nap layer come into contact with the workpiece during polishing.

10. 10. The polishing method according to claim 8, wherein the polishing head presses the workpiece against the polishing pad with a pressure of 10 MPa or more during polishing.

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