Wafer suction pad and method for manufacturing the same

Abstract

The present invention provides a wafer suction pad that can prevent damage to the wafer and accurately position the wafer on a holding base. [Solution] The silicon wafer 20 has multiple napped portions 15 that are further tilted by the silicon wafer 20 when the silicon wafer 20 is adsorbed onto the mounting surface 12 by the negative pressure of the air passage 13, so that the center of the silicon wafer 20 (third central axis CA3) does not shift relative to the center of the mounting surface 12 (second central axis CA2). This prevents scratches on the silicon wafer 20 and allows for accurate positioning of the silicon wafer 20 relative to the holder.

Description

Technical Field

[0001] The present invention relates to a wafer adsorption pad and a method for manufacturing the same.

Background Art

[0002] For example, Patent Document 1 describes a polishing apparatus that polishes the outer edge of a semiconductor wafer as a workpiece. The polishing apparatus described in Patent Document 1 includes a workpiece holding table that holds the workpiece by negative pressure, and a rotating head that rotates relative to the workpiece holding table and has a polishing tool.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the technique described in Patent Document 1, the workpiece is directly placed on the workpiece holding table. Therefore, there is a risk of damaging the workpiece. In order to prevent the workpiece from being damaged, simply placing a buffer material between the workpiece and the workpiece holding table causes the center of the workpiece to shift with respect to the center of the workpiece holding table as the buffer material deforms during adsorption of the workpiece. Thus, the positional accuracy of the workpiece with respect to the workpiece holding table decreases.

[0005] An object of the present invention is to provide a wafer adsorption pad that can prevent the wafer from being damaged and can accurately position the wafer with respect to the holding table.

Means for Solving the Problems

[0006] One embodiment of a wafer suction pad is provided between a wafer and a holding stand of a polishing apparatus for polishing the outer edge of the wafer, and is made of an elastic material, comprising: a mounting surface attached to the holding stand; a placement surface on which the wafer is placed; an air passage connecting the mounting surface and the placement surface; a plurality of voids, one of which is closed on the mounting surface side and the other on the placement surface side; and a plurality of protrusions, each pre-inclined in a predetermined direction so as not to shift the center of the wafer relative to the center of the placement surface, and which are further inclined by the wafer when the wafer is adsorbed to the placement surface by the negative pressure of the air passage.

[0007] In one embodiment of a method for manufacturing a wafer suction pad, the wafer suction pad is provided between a wafer and a holding stand of a polishing apparatus for polishing the outer edge of the wafer, and is made of an elastic material, comprising: a cutting step of cutting out a circular pad material from a sheet material having a plurality of voids; a polishing step of polishing the side of the pad material on which the wafer is placed to open up the plurality of voids; and an air passage forming step of forming an air passage that penetrates the pad material in the thickness direction, wherein in the polishing step, the pad material is rotated about its center, and a polishing tool is pressed against the side of the pad material on which the wafer is placed, thereby tilting the plurality of protrusions formed on the side of the pad material on which the wafer is placed so that their tips face one side in the circumferential direction of the pad material, with the center of the pad material at the center of the pad material. [Effects of the Invention]

[0008] According to the present invention, a wafer suction pad can be realized that prevents damage to the wafer and allows for precise positioning of the wafer relative to the holding base. [Brief explanation of the drawing]

[0009] [Figure 1] This figure shows an example of the application of a wafer suction pad to a polishing apparatus. [Figure 2] This diagram shows the details of the wafer suction pad. [Figure 3]This diagram illustrates the positioning accuracy of the wafer suction pad. [Figure 4] This is a flowchart showing the manufacturing procedure for wafer suction pads. [Figure 5] This is a diagram illustrating the [cutting process]. [Figure 6] This is a diagram illustrating the [polishing process]. [Figure 7] This is a magnified image showing a cross-section of the pad material before polishing. [Figure 8] This is a magnified image showing the cross-section of the pad material after polishing. [Figure 9] This is a diagram illustrating the [air passage formation process]. [Figure 10] This diagram illustrates the positioning accuracy of the wafer suction pad in the comparative example. [Figure 11] This diagram illustrates the polishing process of a modified wafer suction pad. [Modes for carrying out the invention]

[0010] Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

[0011] Figure 1 shows an example of applying a wafer suction pad to a polishing apparatus. Figure 2 shows details of the wafer suction pad.

[0012] <Overview of polishing equipment> As shown in Figure 1, the wafer suction pad 10 is applied to a polishing apparatus 30 that polishes the outer edge of a thin, circular silicon wafer (wafer) 20. The polishing apparatus 30 has a holder 31 that holds the silicon wafer 20. The holder 31 is formed in a substantially disc shape and is positioned on a first central axis CA1. The holder 31 is also supported by a support shaft 32 positioned on the first central axis CA1. The holder 31 and the support shaft 32 are rotatable around the first central axis CA1.

[0013] At the centers of the holding table 31 and the support shaft 32, a first vacuum path 33 through which negative-pressure air is supplied is provided along the first central axis CA1. Further, on the side of the holding table 31 where the wafer suction pad 10 is provided (the upper side in the figure), a plurality of second vacuum paths 34 communicating with the first vacuum path 33 are provided. Here, the plurality of second vacuum paths 34 extend radially in a direction orthogonal to the first central axis CA1 and extend in the circumferential direction of the holding table 31 around the first central axis CA1.

[0014] Furthermore, the polishing apparatus 30 includes a rotating head 35 that rotates relative to the holding table 31 around the first central axis CA1. The rotating head 35 has a frame 36, and a plurality of first polishing tools 37 and second polishing tools 38 are movably provided on the frame 36. The first polishing tool 37 moves in a direction orthogonal to the first central axis CA1, and the second polishing tool 38 moves in a direction oblique to the first central axis CA1.

[0015] Here, the first polishing tool 37 and the second polishing tool 38 are respectively attached to a swing arm (not shown) provided with a weight piece. The swing arm is swingably attached to the frame 36. Then, as the frame 36 rotates, the weight piece moves radially outward due to centrifugal force, so that the first polishing tool 37 and the second polishing tool 38, which are lighter than the weight piece, are respectively moved radially inward.

[0016] The wafer suction pad 10 is fixed to the upper side of the holding table 31, that is, the side where the second vacuum path 34 is provided, by an adhesive tape or the like (not shown). Specifically, the second central axis CA2 (see FIG. 2) of the wafer suction pad 10 coincides with the first central axis CA1 of the holding table 31. Also, the linear passage 13a and the arc-shaped passage 13b (see FIG. 2) of the wafer suction pad 10 are respectively aligned with the second vacuum path 34 of the holding table 31.

[0017] <Operation of the polishing apparatus> To polish the outer edge of the silicon wafer 20, first place the silicon wafer 20 on the wafer suction pad 10. At this time, align the third central axis CA3 of the silicon wafer 20 with the second central axis CA2 of the wafer suction pad 10. Then, supply negative-pressure air to the first vacuum path 33 and the second vacuum path 34. Thereby, the air passage 13 (see FIG. 2) of the wafer suction pad 10 also becomes negative pressure, and the silicon wafer 20 is adsorbed to the wafer suction pad 10.

[0018] Next, rotate the rotating head 35 as indicated by the two-dot chain line arrow R1. Then, the plurality of first polishing tools 37 move radially inward of the frame 36 as indicated by the two-dot chain line arrow M1 and come into contact with the outer edge of the silicon wafer 20. Also, the plurality of second polishing tools 38 move radially inward of the frame 36 as indicated by the two-dot chain line arrow M2 and come into contact with the outer edge of the silicon wafer 20. Further, move the holding table 31 up and down as indicated by the solid line arrow M3. Thereby, the outer edge of the silicon wafer 20 is polished and finished so that the cross-sectional shape along the axial direction is substantially arc-shaped.

[0019] Here, the outer edge of the silicon wafer 20 protrudes outside the radial direction of the holding table 31 and the wafer suction pad 10. Therefore, the first polishing tool 37 and the second polishing tool 38 can polish the outer edge of the silicon wafer 20. Incidentally, the holding table 31 may be rotated in the direction opposite to the rotation direction (two-dot chain line arrow R1) of the rotating head 35 (solid line arrow R2). In this case, the relative rotation speed between the outer edge of the silicon wafer 20 and the first polishing tool 37 and the second polishing tool 38 can be increased, and thus the time required for the polishing operation can be shortened.

[0020] <Detailed Structure of Wafer Suction Pad> As shown in Figure 2, the wafer suction pad 10 is made of a lightweight elastic material, such as foamed urethane, and is formed in a thin, circular shape. Specifically, in this embodiment, the diameter of the wafer suction pad 10 is approximately 280 mm, and the thickness of the wafer suction pad 10 is approximately 0.7 mm. The diameter of the silicon wafer 20 is approximately 300 mm, so when the silicon wafer 20 is placed on the wafer suction pad 10 with its center aligned, the outer edge of the silicon wafer 20 extends radially outward from the holder 31 and the wafer suction pad 10.

[0021] The wafer suction pad 10 has a mounting surface 11 that faces the second vacuum path 34 of the holding base 31. The mounting surface 11 is provided with adhesive tape or the like (not shown) for fixing the wafer suction pad 10 to the holding base 31. The wafer suction pad 10 also has a mounting surface 12 on which a silicon wafer 20 is placed. Here, the mounting surface 11 and the mounting surface 12 are arranged facing each other in the axial direction of the second central axis CA2 of the wafer suction pad 10.

[0022] Furthermore, the wafer suction pad 10 is provided with an air passage 13 that connects the mounting surface 11 and the placement surface 12. Specifically, the air passage 13 penetrates in the axial direction of the second central axis CA2 and is arranged over substantially the entire surface of the wafer suction pad 10. As a result, the silicon wafer 20 is held in place with substantially uniform suction force over substantially the entire surface of the placement surface 12 by the negative pressure of the air passage 13. Therefore, even if the wafer suction pad 10 elastically deforms when the silicon wafer 20 is held in place, the parallelism between the silicon wafer 20 and the holding base 31 can be maintained with high accuracy.

[0023] Here, the air passage 13 has a plurality of linear passages 13a extending radially in a direction perpendicular to the second central axis CA2, and a plurality of arc-shaped passages 13b that communicate with these linear passages 13a and extend in the circumferential direction of the wafer suction pad 10 around the second central axis CA2. As a result, the insides of the first vacuum passage 33, the second vacuum passage 34, and the air passage 13 are all maintained at the same pressure.

[0024] Furthermore, the wafer adsorption pad 10 is made of foamed urethane, and multiple roughly teardrop-shaped voids 14 are formed inside it. In Figure 2, the voids 14 are shown in a simplified shape and arranged in a horizontal row for easier viewing. In reality, the voids 14 vary in size and are arranged irregularly, as shown in the images in Figures 7 and 8.

[0025] Furthermore, each of the multiple voids 14 is closed on the mounting surface 11 side and open on the mounting surface 12 side. As a result, each of the multiple voids 14 functions like a suction cup when the silicon wafer 20 is adsorbed. Therefore, the fixing strength (adsorption force) of the silicon wafer 20 to the mounting surface 12 is increased, and the silicon wafer 20 is stably held on the wafer adsorption pad 10.

[0026] Furthermore, the wafer suction pad 10 has multiple fine, hair-like napped portions (protrusions) 15 on the mounting surface 12 side. These napped portions 15 are formed when the surface of the pad material W1 (the surface that will later become the mounting surface 12) is polished to open the side of the void portion 14 where the mounting surface 12 is provided, as shown in Figure 6, and are therefore unnecessary. When the silicon wafer 20 is adsorbed onto the mounting surface 12 by the negative pressure of the air passage 13, the multiple napped portions 15 are pressed down by the silicon wafer 20 and bent over.

[0027] Here, the multiple napped portions 15 are pre-inclined with respect to the mounting surface 12 in the direction indicated by the symbol ">" as shown in Figure 2. As a result, when the silicon wafer 20 is adsorbed, the multiple napped portions 15 are further inclined in the respective specified directions. Note that, as shown in the lower left [View by arrow A] of Figure 2, the symbol ">" indicates that the inclination direction HD of the napped portion 15 is to the right in the figure. Also, as shown in the lower right [View by arrow B] of Figure 2, the symbol "<" indicates that the inclination direction HD of the napped portion 15 is to the left in the figure.

[0028] Furthermore, in the wafer suction pad 10 of this embodiment, as shown in Figure 2, the multiple napped portions 15 are pre-inclined so that their respective tips face one side of the circumferential direction of the mounting surface 12 (clockwise direction in Figure 2), with respect to the center of the mounting surface 12 (second central axis CA2). In other words, the base end of each napped portion 15 is creased so that it further inclines in a predetermined direction (inclination direction HD) when the silicon wafer 20 is pressed against it.

[0029] In this way, by pre-tilting the multiple napped portions 15 so that they face one side in the circumferential direction of the mounting surface 12, with respect to the second central axis CA2 of the mounting surface 12, the silicon wafer 20 rotates by a small angle around the second central axis CA2 during adsorption, following the tilt of each napped portion 15 in the tilt direction HD.

[0030] In other words, the multiple napped portions 15 are each pre-inclined in a predetermined direction so that when the silicon wafer 20 is adsorbed, the center of the silicon wafer 20 (third central axis CA3) does not shift relative to the center of the mounting surface 12 (second central axis CA2). To put it another way, in the wafer adsorption pad 10 of this embodiment, the "positional displacement" of the silicon wafer 20 due to further inclination of the multiple napped portions 15 is controlled to be in a rotational direction around the second central axis CA2 of the mounting surface 12.

[0031] <Verification of the positioning accuracy of wafer suction pads> Figure 3 illustrates the positioning accuracy of the wafer suction pad.

[0032] As shown in Figure 3 [Before Adsorption], when the third central axis CA3 of the silicon wafer 20 and the second central axis CA2 of the wafer adsorption pad 10 are aligned and no negative pressure is supplied to the air passage 13, the multiple napped portions 15 are slightly tilted in the tilt direction HD such that the distance between the silicon wafer 20 and the wafer adsorption pad 10 is t1 (=δt).

[0033] Then, as shown in Figure 3 [After Adsorption], when negative pressure is supplied to the air passage 13 to adsorb the silicon wafer 20 onto the wafer adsorption pad 10, the multiple napped portions 15 are pressed against the silicon wafer 20 and tilted further. The distance between the silicon wafer 20 and the wafer adsorption pad 10 becomes t2 (≒0). The wafer adsorption pad 10 is also elastically deformed so as to be slightly compressed, and the multiple void portions 14 each act like suction cups.

[0034] At this time, following the inclination of each napped portion 15 in the inclination direction HD (clockwise), the silicon wafer 20 is rotated by a small angle around the second central axis CA2 of the wafer suction pad 10. In other words, the third central axis CA3 of the silicon wafer 20 hardly shifts relative to the second central axis CA2 of the wafer suction pad 10. Specifically, the amount of "shift" was only about 1.0 μm in the lateral direction (X-axis direction) and 1.5 μm in the vertical direction (Y-axis direction), as shown in [After adsorption] in Figure 3. This degree of central displacement does not adversely affect the polishing accuracy of the outer edge of the silicon wafer 20.

[0035] Thus, in the wafer suction pad 10 of this embodiment, the positional displacement of the silicon wafer 20 due to the inclination of the multiple napped portions 15 is controlled in the rotational direction around the second central axis CA2 of the wafer suction pad 10. Therefore, a large misalignment between the third central axis CA3 of the silicon wafer 20 and the second central axis CA2 of the wafer suction pad 10 is suppressed. Consequently, while preventing damage to the silicon wafer 20 due to the elastic deformation (cushioning) of the wafer suction pad 10, sufficient positional accuracy of the silicon wafer 20 relative to the wafer suction pad 10 is ensured.

[0036] <Method for manufacturing wafer suction pads> Next, the manufacturing method of the wafer suction pad 10 formed as described above will be explained in detail with reference to the drawings.

[0037] Figure 4 is a flowchart showing the manufacturing procedure for wafer suction pads. Figure 5 is a diagram explaining the [cutting process]. Figure 6 is a diagram explaining the [polishing process]. Figure 7 is a magnified image showing the cross-section of the pad material before polishing. Figure 8 is a magnified image showing the cross-section of the pad material after polishing. Figure 9 is a diagram explaining the [air passage formation process].

[0038] As shown in Figure 4, the wafer adsorption pad 10 is manufactured through the cutting process in step S1, the polishing process in step S2, and the air passage formation process in step S3.

[0039] <Step S1> As shown in Figure 5, in the cutting process of step S1, first, a roll of raw material 51 is prepared by rolling up a sheet-like material 50. Here, the sheet-like material 50 is made of foamed urethane and has multiple voids 14 (see Figure 2). Then, as shown by the solid arrow M4, the sheet-like material 50 is pulled out and cut at the cutting position CL using a cutter or scissors. This forms a square sheet (sheet material) 52. In this embodiment, the length and width dimensions of the square sheet 52 are both L (approximately 1 m).

[0040] Next, as shown by the solid arrow M5, the cylindrical cutter 53 is pressed against the square sheet 52 to cut out the circular pad material W1. Since the diameter of the pad material W1 is approximately 280 mm, a total of 9 pad materials W1 can be cut out from one square sheet 52.

[0041] This completes the cutting process in step S1.

[0042] <Step S2> As shown in Figure 6, in the polishing process of step S2, first, the pad material W1 cut out in step S1 is placed on the polishing turntable 54. At this time, the second central axis CA2 of the pad material W1 is aligned with the first rotation center C1 of the polishing turntable 54. Then, the polishing turntable 54 is rotated counterclockwise around the first rotation center C1, as shown by the solid arrow R3. In other words, the pad material W1 is rotated around its center (second central axis CA2).

[0043] Next, the rotary polishing tool (polishing tool) 55, positioned above the polishing turntable 54, that is, on the side of the polishing turntable 54 where the pad material W1 is provided, is rotated clockwise around the second rotation center C2, as indicated by the solid arrow R4. Then, while both the polishing turntable 54, including the pad material W1, and the rotary polishing tool 55 are rotated at a predetermined rotational speed, the rotary polishing tool 55 is lowered toward the polishing turntable 54, as indicated by the solid arrow M6. This presses the rotary polishing tool 55 against the surface of the pad material W1 to be polished, that is, the side on which the silicon wafer 20 is placed.

[0044] Here, the rotary polishing tool 55 is rotated faster than the polishing turntable 54. Furthermore, the rotary polishing tool 55 is moved little by little in the axial direction of the second rotation center C2, as indicated by the solid arrow M7. This ensures that the entire surface of the pad material W1 on which the silicon wafer 20 is placed is polished uniformly. For example, a cylindrical sandpaper can be used as the rotary polishing tool 55.

[0045] Therefore, the side of the pad material W1 on which the silicon wafer 20 is placed is polished, and the mounting surface 12 is finished. In other words, the mounting surface 12 side of the multiple voids 14 (see Figure 2) is opened, and multiple napped portions 15 (see Figure 2) are formed on the mounting surface 12, which are tilted by the silicon wafer 20 when the silicon wafer 20 is adsorbed. At this time, because the rotary polishing tool 55 rotates faster than the polishing turntable 54, the tips of the multiple napped portions 15 are tilted so that they face one side (tilt direction HD) in the circumferential direction of the pad material W1, with respect to the center of the pad material W1 (second central axis CA2).

[0046] More specifically, as shown in Figure 7, before polishing the pad material W1, a polishing layer LA with a thickness of dimension T exists on its surface (upper side in the figure). This polishing layer LA closes multiple voids 14, and each void 14 is closed. Subsequently, by polishing the surface of the pad material W1 and removing the polishing layer LA with a thickness of dimension T, the multiple voids 14 are opened, as shown in Figure 8, and the mounting surface 12 is finished. Note that the napped area 15 generated during the polishing of the pad material W1 is extremely small compared to the voids 14. Therefore, it cannot be seen in the images of Figures 7 and 8.

[0047] This completes the polishing process in step S2.

[0048] <Step S3> As shown in Figure 9, in step S3, the [air passage formation process], the pad material W1 obtained in step S2, the [polishing process], is prepared, and a passage formation cutter 56 equipped with a blade capable of cutting out the air passage 13 is prepared. The passage formation cutter 56 is then positioned coaxially with respect to the pad material W1, and the passage formation cutter 56 is lowered as shown by the solid arrow M8. The passage formation cutter 56 is then pressed against the pad material W1 to perform the cutting.

[0049] This creates an air passage 13 that penetrates the pad material W1 in the thickness direction, completing the wafer adsorption pad 10. Note that the outer diameter dimension D1 of the passage-forming cutter 56 is smaller than the outer diameter dimension D2 of the pad material W1 (D1 <D2)。

[0050] Furthermore, the die-cutting of the pad material W1 is performed one piece at a time to ensure sufficient molding accuracy for the air passage 13.

[0051] This completes the [air passage formation process] in step S3.

[0052] <Comparative Example (Example with Large Positional Misalignment)> Next, using Figure 10, we will explain in detail the case (comparative example) in which the center of the silicon wafer 20 (see Figure 2) is significantly misaligned with the center of the wafer adsorption pad 100 (second central axis CA2) during the adsorption of the silicon wafer 20.

[0053] Figure 10 illustrates the positioning accuracy of the wafer suction pad in the comparative example.

[0054] As shown in the [Comparative Example] in Figure 10, the wafer suction pad 100 of the comparative example has a different inclination direction HD of the multiple napped portions 101 compared to the wafer suction pad 10 described above (see Figure 2). Specifically, in the wafer suction pad 100 of the comparative example, the inclination direction HD of all the multiple napped portions 101 is to the right in the figure. In other words, in the wafer suction pad 100, the inclination direction HD of all the multiple napped portions 101 is in the same direction.

[0055] As shown in Figure 10 [Before Adsorption], when the third central axis CA3 of the silicon wafer 20 and the second central axis CA2 of the wafer adsorption pad 100 are aligned and no negative pressure is supplied to the air passage 13, all of the napped portions 101 are facing one side (right side in the figure) and are slightly tilted in the tilt direction HD, such that the distance between the silicon wafer 20 and the wafer adsorption pad 100 is t1 (=δt).

[0056] Subsequently, as shown in Figure 10 [After Adsorption], when negative pressure is supplied to the air passage 13 to adsorb the silicon wafer 20 onto the wafer adsorption pad 100, the multiple napped portions 101 are pressed against the silicon wafer 20 and all of them are tilted further. The distance between the silicon wafer 20 and the wafer adsorption pad 100 then becomes t2 (≒0). The wafer adsorption pad 100 is also elastically deformed to be slightly compressed, and the multiple void portions 14 each act like suction cups.

[0057] In the comparative example, the wafer suction pad 100 showed relatively large displacements of 61.0 μm in the lateral direction (X-axis direction) and 30.2 μm in the vertical direction (Y-axis direction), as shown in Figure 10 under [After Suction]. Such a large displacement of the center leads to a decrease in the polishing accuracy of the outer edge of the silicon wafer 20. In other words, it becomes difficult to uniformly polish the outer edge of the silicon wafer 20 around its entire circumference.

[0058] <Variation> Next, a modified example of the wafer suction pad 200 will be described in detail using Figure 11.

[0059] Figure 11 illustrates the polishing process of a modified wafer suction pad.

[0060] In the modified wafer suction pad 200, the inclination direction HD of the multiple napped portions (protrusions) 201 is different from that of the wafer suction pad 10 in Figure 2. Specifically, as shown in Figure 11, the multiple napped portions 201 provided on the wafer suction pad 200 are pre-inclined so that their inclination direction HD does not face the same direction as in the comparative example described above, but rather faces in various directions. In other words, in the modified wafer suction pad 200, the inclination direction HD of the napped portions 201 is not biased in any particular direction.

[0061] Specifically, in the modified version, during the polishing process, the elongated rod-shaped rotary polishing tool (polishing tool) 250 is rotated clockwise around the third rotation center C3 as indicated by the solid arrow R5, and the polishing position of the rotary polishing tool 250 is changed from M9 to M14, thereby polishing the entire surface of the pad material W2, which will later become the wafer adsorption pad 200. The pad material W2 is fixed in place so as not to move.

[0062] Here, the rotational speed and polishing position of the rotary polishing tool 250 are automatically controlled by a polishing device for pad material polishing (not shown). Specifically, the controller of the polishing device for pad material polishing is pre-programmed with information on the rotational speed and polishing position of the rotary polishing tool 250.

[0063] In this way, the tilt direction HD of the multiple napped portions 201 is pre-tilted so that they face various directions (predetermined directions) without being biased in any particular direction. Therefore, when the silicon wafer 20 (see Figure 1) is adsorbed, the multiple napped portions 201 are each further tilted in various directions.

[0064] Therefore, in the modified wafer suction pad 200, similar to the wafer suction pad 10 in Figure 2, it is possible to suppress a large misalignment between the third central axis CA3 of the silicon wafer 20 and the second central axis CA2 of the wafer suction pad 200.

[0065] As described in detail above, according to this embodiment, the center of the silicon wafer 20 (third central axis CA3) is pre-inclined in a predetermined direction (inclination direction HD) so as not to shift relative to the center of the mounting surface 12 (second central axis CA2), and when the silicon wafer 20 is adsorbed onto the mounting surface 12 by the negative pressure of the air passage 13, there are a plurality of napped portions 15,201 (see Figures 2 and 11) that are further inclined by the silicon wafer 20.

[0066] This prevents scratches on the silicon wafer 20 and allows for precise positioning of the silicon wafer 20 relative to the holder 31.

[0067] Furthermore, according to this embodiment, the multiple napped portions 15 (see Figure 2) are pre-inclined such that their tips face one side in the circumferential direction of the mounting surface 12 (clockwise direction in Figure 2), with respect to the center of the mounting surface 12 (second central axis CA2).

[0068] This allows the "positional displacement" of the silicon wafer 20 due to the tilting of the multiple napped portions 15 to be controlled to rotate around the second central axis CA2 of the mounting surface 12. Therefore, the displacement of the third central axis CA3 of the silicon wafer 20 relative to the second central axis CA2 of the wafer suction pad 10 is suppressed, and while preventing damage to the silicon wafer 20 due to the elastic deformation (cushioning) of the wafer suction pad 10, it is possible to ensure sufficient positional accuracy of the silicon wafer 20 relative to the wafer suction pad 10.

[0069] The present invention is not limited to the embodiments described above, and it goes without saying that various modifications are possible without departing from the spirit of the invention. For example, in the embodiments described above, as shown in Figure 2, the multiple napped portions 15 are shown in a manner in which the tips of each portion are pre-inclined so that they face in a clockwise direction around the center of the mounting surface 12 (second central axis CA2) of the mounting surface 12. However, the invention is not limited to this, and the portions may be pre-inclined so that they face in a counterclockwise direction around the mounting surface 12.

[0070] Furthermore, in the above-described embodiment, the wafer suction pad 10,200 (see Figures 2 and 11) is shown to be made of foamed urethane, but it is not limited to this. Other foamed materials can be used as long as they have multiple voids formed inside and a napped surface formed when the side on which the voids are placed is opened.

[0071] Furthermore, although the above-described embodiment shows multiple thin, hair-like napped portions 15,201 as the protrusions, the invention is not limited to this, and the protrusions do not have to be hair-like as long as they have a weak rigidity that allows them to be tilted and crushed when the silicon wafer 20 is adsorbed. [Explanation of Symbols]

[0072] 10 wafer suction pads 11 Mounting surface 12 Mounting surface 13 Air passage 14 Cavity 15 Raised part (protrusion) 20. Silicon wafer (wafer) 30 Polishing equipment 31 Holding stand 52 square sheets (sheet material) 55 Rotary polishing tools (polishing tools) 200 wafer suction pads 201 Raised part (protrusion) 250 Rotary Polishing Tool (Polishing Tool) CA2 Second central axis (center of the mounting surface) CA3 Third central axis (center of the wafer) HD tilt direction (default direction) W1, W2 pad material

Claims

1. A wafer suction pad made of an elastic material is provided between the wafer and the holding base of a polishing apparatus for polishing the outer edge of the wafer, The mounting surface to be attached to the aforementioned holding base, The mounting surface on which the wafer is placed, An air passage connecting the mounting surface and the aforementioned placement surface, Multiple voids, the mounting surface side being closed and the placement surface side being open, The central part of the wafer is pre-inclined in a predetermined direction so as not to shift relative to the central part of the mounting surface described above, and when the wafer is attracted to the mounting surface described above by the negative pressure of the air passage, there are a plurality of protrusions that are further inclined by the wafer, Equipped with, Wafer suction pad.

2. In the wafer adsorption pad according to claim 1, The multiple aforementioned protrusions are pre-inclined such that their tips face one side in the circumferential direction of the aforementioned mounting surface, with respect to the center of the aforementioned mounting surface. Wafer suction pad.

3. A method for manufacturing a wafer suction pad made of an elastic material, which is provided between a wafer and a holding base of a polishing apparatus for polishing the outer edge of the wafer, A cutting process in which a circular pad material is cut out from a sheet material having multiple voids, A polishing step in which the side of the pad material on which the wafer is placed is polished to open up a plurality of the void portions, The process includes forming an air passage in the pad material that penetrates in the thickness direction, Equipped with, In the polishing process, the pad material is rotated around its center while a polishing tool is pressed against the side of the pad material on which the wafer is placed, thereby tilting the multiple protrusions formed on the side of the pad material on which the wafer is placed, so that their tips face one side in the circumferential direction of the pad material, with the center of the pad material as the point of contact. A method for manufacturing wafer suction pads.

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