Brush polishing apparatus and method of manufacturing wafer holding apparatus

Abstract

The invention provides a technology for removing metal elements remaining on the surface of a wafer holding device. The brush polishing apparatus includes: a stage that supports a wafer holding device having a plurality of protrusions on a surface thereof; and a brush which includes bristles made of a non-metallic material and a bristle holder made of a non-metallic material, and which grinds the wafer holding device supported by the stage.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a brush grinding device and a wafer holding device. Background Art

[0002] Patent Document 1 discloses a method for manufacturing an electrostatic chuck as a wafer holding device. The method includes a step of performing embossing, which forms protrusions on the surface of the electrostatic chuck by a sandblasting method.

[0003] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2010-165805

[0004] In the sandblasting method described in Patent Document 1, abrasive grains formed of ceramics such as silicon carbide or alumina are generally used. Therefore, there is a possibility that metal elements remain on the wafer holding device. The metal elements remaining on the surface of the wafer holding device may cause defects when a film is formed on the wafer. The present disclosure provides a technique for removing metal elements remaining on the surface of the wafer holding device. Summary of the Invention

[0005] A brush grinding device according to one aspect of the present disclosure includes: a workbench that supports a wafer holding device having a plurality of convex portions on its surface; and a brush that includes bristles formed of a non-metallic material and a bristle holder formed of a non-metallic material, and the brush grinds the wafer holding device supported by the workbench.

[0006] A method for manufacturing a wafer holding device according to another aspect of the present disclosure includes a step of grinding a wafer holding device having a plurality of convex portions on its surface with a brush that includes bristles formed of a non-metallic material and a bristle holder formed of a non-metallic material.

[0007] According to the present disclosure, it is possible to remove metal elements remaining on the surface of the wafer holding device. Brief Description of the Drawings

[0008] Figure 1 is a diagram for explaining an outline of a brush grinding device according to an embodiment.

[0009] Figure 2 is a cross-sectional view showing an example of a wafer holding device to be processed.

[0010] Figure 3 is for Figure 1 explaining details of the workbench and the brush.

[0011] Figure 4 is for Figure 1 explaining details of the workbench and the brush.

[0012] Figure 5 This is a flowchart showing a manufacturing method of a wafer holding device. Detailed implementation manners

[0013] Embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same reference numerals are assigned to the same elements, and repeated descriptions are omitted. The dimensional ratios of the drawings do not have to be consistent with the description. The terms "upper", "lower", "left", and "right" are based on the illustrated state and are used for convenience.

[0014] [Brush grinding device]

[0015] Figure 1 This is a diagram showing an overview of a brush grinding device according to an embodiment. Figure 1 The illustrated brush grinding device 1 is a device for grinding the surface of a wafer holding device 2. The wafer holding device 2 is a device for holding a wafer (substrate) for semiconductor manufacturing or the like, and as an example, it is an electrostatic chuck.

[0016] Figure 2 This is a cross-sectional view showing an example of a wafer holding device to be processed. Figure 2 The illustrated wafer holding device 2 is, as an example, a disk-shaped device. The material of the wafer holding device 2 is a hard and brittle material, and examples include alumina, silicon carbide, aluminum nitride, etc. As Figure 2 shown, the surface of the wafer holding device 2 has a plurality of convex portions. The plurality of convex portions can be formed by embossing, or can be formed by a process in which a region surrounded by a plurality of grooves (for example, a lattice shape) becomes a convex portion. In one embodiment, embossing is performed on the surface of the wafer holding device 2 to form a plurality of protrusions (embossing) 2a. Embossing is achieved by, as an example, a sandblasting method. In the case where the sandblasting method is adopted, abrasive grains usually formed of ceramics such as silicon carbide, alumina, and zirconium silicate often remain on the surface. In addition, the wafer holding device 2 supports the wafer by the flat and smooth upper end surfaces of the plurality of protrusions 2a. During semiconductor manufacturing, a wafer cooling gas such as He gas is supplied between the plurality of protrusions 2a supporting the wafer. The surface roughness of the bottom 2b between the plurality of protrusions 2a affects the fluidity of the wafer cooling gas. In order to remove at least one of the metal elements remaining on the surface of the wafer holding device 2 and improve the fluidity of the wafer cooling gas, the brush grinding device 1 grinds the wafer holding device 2.

[0017] As Figure 1As shown, the brush grinding device 1 includes a housing 3 that houses the wafer holding device 2. Inside the housing 3, a table 10 that supports the wafer holding device 2 is arranged. The table 10 is a disk-shaped member, and is arranged such that its main surface is horizontal. The table 10 is connected to a rotation drive unit 10a. The rotation drive unit 10a has a drive source such as a motor and a rotation rod extending in the vertical direction. The rotation rod is connected to the center of the disk of the table 10. The table 10 is configured to be rotatable about the rotation axis.

[0018] Above the table 10, a plurality of brushes 11A are arranged, and the plurality of brushes 11A grind the wafer holding device 2 on the table 10. The structures of the plurality of brushes 11A are the same. Hereinafter, when referring to one brush included in the plurality of brushes 11A, it is called a brush 11. The brush 11 includes a brush holder 11a and bristles 11b. The brush holder 11a is a member that fixes the ends of the bristles 11b and is formed of a non-metallic material. The brush holder 11a is formed of resin, for example. As an example, the resin is polyvinyl chloride. The bristles 11b are formed of a non-metallic material. The bristles 11b are chemical fibers, for example. Examples of chemical fibers include polyamide-based fibers (such as nylon), polyester-based fibers (PET, PBT, PEN, PP, etc.), aromatic polyamide-based fibers (aramid, etc.), and fluororesin fibers (PTFE, PFA, etc.).

[0019] The plurality of brushes 11A are connected to a multi-axis unit 12 that performs the rotation and revolution of the brush 11. The multi-axis unit 12 has a mechanism that rotates each of the plurality of brushes 11A independently and a mechanism that revolves the plurality of brushes 11A by rotating the independent rotation mechanism. The multi-axis unit 12 is connected to one or more drive sources (not shown). The plurality of brushes 11A perform planetary motion through the multi-axis unit 12 to uniformly grind the surface of the wafer holding device 2.

[0020] The multi-axis unit 12 is connected to a first lifting unit 13 and a second lifting unit 14, and is configured to be movable up and down. The first lifting unit 13 and the second lifting unit 14 are electric cylinders, for example. The second lifting unit 14 can set the height adjustment more precisely than the first lifting unit 13. After the position of the multi-axis unit 12 is adjusted by the first lifting unit 13, it is finely adjusted by the second lifting unit 14. Thereby, the tips of the plurality of brushes 11 can accurately contact the surface of the wafer holding device 2.

[0021] In the housing 3 of the brush grinding device 1, a liquid supply unit 15 is disposed, and the liquid supply unit 15 supplies liquid to the wafer holding device 2 on the worktable 10. The liquid supply unit 15 has a nozzle disposed toward the surface of the wafer holding device 2. When grinding the surface of the wafer holding device 2 with a plurality of brushes 11, the liquid supply unit 15 supplies liquid from the nozzle to the surface of the wafer holding device 2 to achieve wet grinding. An example of the liquid is pure water. By using pure water, the cleaning effect of the surface of the wafer holding device 2 can be improved. The liquid used for grinding is discharged from the discharge port 3a of the housing 3 and is discharged by the discharge pump 16.

[0022] [Details of the worktable and the brush]

[0023] Figure 3 and Figure 4 is a diagram for Figure 1 explaining the details of the worktable and the brush. As Figure 3 and Figure 4 shown, the worktable 10 has a base 10c and a contact member 10b. The contact member 10b is disposed on the base 10c and has a support surface for supporting the wafer holding device 2. The contact member 10b is formed of a non-metal. The contact member 10b is formed of, for example, resin, and examples include MC nylon and polyurethane rubber. By making the contact portion in contact with the wafer holding device 2 a non-metal such as resin, attachment of metal elements to the wafer holding device 2 can be suppressed. In addition, the worktable 10 rotates about the rotation axis Z1 by the rotation drive unit 10a. The rotation axis Z1 is a line passing through the center of the worktable 10 and extending in the vertical direction. On the upper surface of the worktable 10, locking members 10d are provided at predetermined intervals in the circumferential direction of the worktable 10, and the locking members 10d are used to position and fix the wafer holding device 2. By providing the locking members 10d, it is possible to prevent the wafer holding device 2 from falling off the worktable 10 during grinding.

[0024] During grinding, the worktable 10 rotates and the plurality of brushes 11A also rotate and revolve respectively. In the multi-axis unit 12, the brush 11 is supported by a rotation rod. The rotation rod is rotatably connected to the substantially disk-shaped main body of the multi-axis unit 12. Thus, the brush 11 can rotate about the rotation axis (such as rotation axes Z2, Z3, etc.) passing through the rotation axis of the rotation rod. The main body of the multi-axis unit 12 rotates about the rotation axis Z4. The rotation axis Z4 is a line passing through the center of the main body of the multi-axis unit 12 and extending in the vertical direction. Thus, the brush 11 can revolve about the rotation axis Z4.

[0025] The bristles 11b may also contain abrasives. The diameter of the abrasives is 50 μm to 80 μm, and the abrasives are contained in the bristles in a range of 7 wt% to 30 wt%. In addition, the density of the bristles, which represents the ratio of the occupied area of the bristles to the unit area, is 40% to 95%. When the diameter of the abrasives is less than 50 μm, the polishing force becomes weak, and it is difficult to make the surface roughness of the bottom 2b between the plurality of protrusions 2a in the wafer holding device 2 become the arithmetic mean roughness (Ra) of 0.5 or less as specified in JIS (Japanese Industrial Standards) B 0601:2013. When the diameter of the abrasives is greater than 50 μm, the surface cannot be polished in a smooth state, and it is difficult to make the surface roughness of the bottom 2b become the arithmetic mean roughness (Ra) of 0.5 or less. By setting the diameter of the abrasives to 50 μm to 80 μm, the surface roughness of the bottom 2b can be made the arithmetic mean roughness (Ra) of 0.5 or less, thereby improving the fluidity of the gas for wafer cooling. In addition, in the case where rounding is performed such that the outer edge portion of the upper end surface of the protrusion 2a is a curved surface, even if microcracks are generated in the outer edge portion of the upper end surface in the process of forming the protrusion 2a, the microcracks can be removed during the rounding process. The wafer holding device 2 is exposed to environments such as reduced pressure (vacuum), heat, or plasma during the processing of the wafer. When microcracks exist in the wafer holding device 2, due to changes in the environment, damage develops starting from the microcracks, resulting in chipping. The chips generated by the chipping adhere to the wafer, causing contamination. By polishing using the brush 11, it is possible to both improve the fluidity of the gas for wafer cooling and prevent contamination of the wafer.

[0026] [Operation of Brush Polishing Device]

[0027] Figure 5 is a flowchart showing a method for manufacturing a wafer holding device. As Figure 5 shown, the method for manufacturing a wafer holding device includes an embossing step (S10) and a polishing step (S12). In the embossing step (S10), an embossing is formed on the surface of the wafer holding device 2. For example, a mesh-shaped mask is formed on the surface of the wafer holding device 2, and metal abrasive grains are sprayed from above the mask by compressed air or the like. In the sandblasting method, for example, the entire surface of the wafer holding device 2 is embossed by performing a line scan on the nozzle.

[0028] Next, in the polishing step (S12), the wafer holding device 2 is housed in the housing 3 of the brush polishing device 1. The wafer holding device 2 is disposed at a position located by the locking member 10d on the workbench 10. Then, the tips of the plurality of brushes 11A are positioned on the surface of the wafer holding device 2 by the first lifting unit 13 and the second lifting unit 14. Then, the rotation drive unit 10a rotates the workbench 10 about its own axis, and the multi-axis unit 12 causes the plurality of brushes 11A to perform planetary motion (rotation about its own axis and revolution). By rotating the workbench 10 about its own axis, the brushes act on the entire surface of the wafer holding device 2. By combining the rotation and revolution of the brush 11, the brush 11 can draw a random trajectory, so that the surface of the wafer holding device 2 can be polished uniformly. When the polishing step (S12) is completed, Figure 5 the flowchart shown ends.

[0029] [Summary of the Embodiment]

[0030] In the brush polishing device 1, the wafer holding device 2 is polished by a brush including bristles 11b formed of a non-metallic material and a bristle holder 11a formed of a non-metallic material. Since the bristles 11b come into strong contact with the wafer holding device, there is a concern that the components of the bristles 11b adhere to the wafer. In addition, the bristle holder 11a is usually selected as a metal in consideration of strength or productivity, but the bristle holder 11a is worn when the brush polishing device 1 operates, and there is a concern that a part of it falls off and adheres to the wafer holding device 2. As in one embodiment, since the bristles 11b and the bristle holder 11a are formed of a non-metal, the brush polishing device 1 can avoid the mixing of metal elements and remove the metal elements remaining on the surface of the wafer holding device 2 as compared with the case of using a brush with bristles and a holder made of a material including a metal. In addition, as in one embodiment, since the contact member 10b in the workbench 10 is formed of a non-metal, the mixing of metal elements can be further avoided, and the metal elements remaining on the surface of the wafer holding device 2 can be removed.

[0031] As described above, various exemplary embodiments have been described, but the present invention is not limited to the above-described exemplary embodiments, and various omissions, substitutions, and changes can be made.

[0032] The brush polishing device 1 only needs to include the workbench 10 and the plurality of brushes 11A, and may not include the rotation drive unit 10a, the multi-axis unit 12, the first lifting unit 13, the second lifting unit 14, and the liquid supply unit 15. The brush polishing device 1 does not need to include the plurality of brushes 11A, and may include one brush 11.

[0033] The brush grinding device 1 only needs to have a removing mechanism capable of removing metal elements remaining on the surface of the wafer holding device 2. That is, the removing mechanism is not limited to a mechanism having a multi-axis unit 12 that rotates and revolves. For example, the removing mechanism may also be a mechanism composed of a single rotating brush, or may be a mechanism having a plurality of brushes 11 as shown in Figure 3 wherein the plurality of brushes 11 only rotate or only revolve.

[0034] The wafer holding device 2 is not limited to an electrostatic chuck and may also be a vacuum chuck.

[0035] [Summary of Embodiments of the Present Disclosure]

[0036] The present disclosure includes the following aspects.

[0037] (Item 1) A brush grinding device according to an aspect of the present disclosure includes: a workbench that supports a wafer holding device having a plurality of convex portions on its surface; and a brush that includes bristles formed of a non-metallic material and a bristle holder formed of a non-metallic material, and the brush grinds the wafer holding device supported by the workbench.

[0038] In this brush grinding device, the wafer holding device is ground by a brush including bristles formed of a non-metallic material and a bristle holder formed of a non-metallic material. Since the bristles and the bristle holder are formed of a non-metal, compared with the case of using a brush including bristles and a holder made of a metal material, this brush grinding device can avoid the mixing of metal elements and remove the metal elements remaining on the surface of the wafer holding device.

[0039] (Item 2)

[0040] Based on the brush grinding device described in Item 1, it may be that the bristles are formed of chemical fibers and the bristle holder is formed of resin. A non-metallic brush is formed by using chemical fibers and resin.

[0041] (Item 3)

[0042] Based on the brush grinding device described in Item 1 or 2, it may be that the bristles contain abrasives, the diameter of the abrasives is 50 μm to 80 μm, and the density of the bristles is 40% to 95%. In this case, the surface roughness of the bottom surface between the protrusions formed by embossing can be made to be an arithmetic mean roughness (Ra) of 0.5 or less. The protrusions formed on the wafer holding device support the wafer and constitute a flow path for a gas that adjusts the temperature of the wafer. Since the arithmetic mean roughness (Ra) of the bottom surface between the protrusions is 0.5 or less, the fluidity of the gas flowing between the protrusions is improved, so that the effect of exhausting heat from the temperature of the wafer is homogenized in the plane. As a result, the quality of the chips formed on the wafer is improved.

[0043] (Item 4)

[0044] Based on the brush grinding device described in any one of Items 1 to 3, it is also possible that the workbench has a support surface for supporting the wafer holding device, and the support surface is formed of a non-metal. By forming the support surface of a non-metal, the brush grinding device can further avoid the mixing of metal elements.

[0045] (Item 5)

[0046] The brush grinding device described in any one of Items 1 to 4 may further include a multi-axis unit that rotates and revolves the brush. By using the multi-axis unit to make the brush perform planetary motion, the brush grinding device can remove the orientation imparted by sandblasting or the like.

[0047] (Item 6)

[0048] A method for manufacturing a wafer holding device according to another aspect of the present disclosure includes a step of grinding a wafer holding device having a plurality of convex portions on its surface with a brush having bristles formed of a non-metal material and a brush holder formed of a non-metal material. The method for manufacturing a wafer holding device has the same effect as the above-described brush grinding device.

Claims

1. A brush grinding device, characterized in that: have: a table supporting a wafer holding device having a plurality of protrusions on a surface thereof; and A brush includes bristles formed of a non-metallic material and a bristle holder formed of a non-metallic material, and the brush grinds the wafer holding device supported on the workbench.

2. The brush grinding device according to claim 1, characterized in that: The bristles are formed of chemical fibers, and the bristle holder is formed of resin.

3. The brush grinding device according to claim 1 or 2, characterized in that: The bristles contain abrasives, the diameter of the abrasives is 50 μm to 80 μm, and the density of the bristles is 40% to 95%.

4. The brush grinding device according to claim 1 or 2, characterized in that: The table has a support surface for supporting the wafer holding device, and the support surface is formed of non-metal.

5. The brush grinding device according to claim 1 or 2, characterized in that: The brush further includes a multi-axis unit configured to rotate and revolve around the brush.

6. A method for manufacturing a wafer holding device, characterized in that: include: A step of polishing a wafer holder having a plurality of protrusions on a surface thereof using a brush having bristles formed of a non-metallic material and a bristle holder formed of a non-metallic material.

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