Brush polishing device, and method for producing wafer-holding device

Abstract

To provide a technique for removing metal elements remaining on the surface of a wafer-holding device.SOLUTION: A brush polishing device includes: a table for supporting a wafer-holding device that has a plurality of protrusions on its surface; and a brush including bristle materials composed of a non-metallic material and a bristle holder composed of a non-metallic material, the brush configured to polish the wafer-holding device supported on the table.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses a method for manufacturing an electrostatic chuck which is a wafer holding device. This method includes a step of performing embossing to form protrusions on the surface of the electrostatic chuck by a sandblasting method.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the sandblasting method as described in Patent Document 1, abrasive grains generally formed from ceramics such as silicon carbide or aluminum oxide are used. For this reason, there is a possibility that metal elements remain on the wafer holding device. Metal elements remaining on the surface of the wafer holding device can cause defects when forming a film on the wafer. The present disclosure provides a technique for removing metal elements remaining on the surface of the wafer holding device.

Means for Solving the Problems

[0005] A brush polishing device according to one aspect of the present disclosure includes a table that supports a wafer holding device having a plurality of convex portions on its surface, a brush material formed of a non-metallic material, and a brush material holder formed of a non-metallic material, and a brush that polishes the wafer holding device supported by the table.

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

Advantages of the Invention

[0007] According to the present disclosure, metal elements remaining on the surface of the wafer holding device can be removed.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0009] Embodiments of the present disclosure will be described in detail with reference to the drawings. In the description of the drawings, the same reference numerals are given to the same elements, and redundant descriptions are omitted. The dimensional ratios in the drawings do not necessarily match those in the description. The terms “upper”, “lower”, “left”, and “right” are based on the illustrated states and are for convenience.

[0010] [Brush Polishing Device] FIG. 1 is a diagram for explaining an outline of a brush polishing device according to an embodiment. The brush polishing device 1 shown in FIG. 1 is a device for polishing the surface of a wafer holding device 2. The wafer holding device 2 is a device for holding a wafer (substrate) used in semiconductor manufacturing or the like, and is, for example, an electrostatic chuck.

[0011] FIG. 2 is a cross-sectional view showing an example of a wafer holding device to be processed. The wafer holding device 2 shown in FIG. 2 is a disk-shaped device as an example. The material of the wafer holding device 2 is a hard and brittle material, and examples thereof include aluminum oxide, silicon carbide, and aluminum nitride. As shown in FIG. 2, the surface of the wafer holding device 2 has a plurality of convex portions. The plurality of convex portions may be formed by embossing, or may 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, the surface of the wafer holding device 2 is embossed, and a plurality of protrusions (embosses) 2a are formed. The embossing is realized by, for example, a sandblasting method. When the sandblasting method is adopted, generally, abrasive grains formed of ceramics such as silicon carbide, aluminum oxide, and zirconium silicate may remain on the surface. Further, the wafer holding device 2 supports the wafer on 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 that support the wafer. The surface roughness of the bottom 2b between the plurality of protrusions 2a affects the fluidity of the wafer cooling gas. The brush polishing device 1 polishes the wafer holding device 2 in order to remove at least one of the metal elements remaining on the surface of the wafer holding device 2 and to improve the fluidity of the wafer cooling gas.

[0012] As shown in FIG. 1, the brush polishing device 1 includes a case 3 that houses the wafer holding device 2. Inside the case 3, a table 10 that supports the wafer holding device 2 is arranged. The table 10 is a disk-shaped member and is arranged so that the 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.

[0013] Above the table 10, a plurality of brushes 11A for polishing the wafer holding device 2 on the table 10 are arranged. The configurations of the plurality of brushes 11A are the same. Hereinafter, when showing one brush included in the plurality of brushes 11A, it is referred to as brush 11. The brush 11 includes a bristle holder 11a and bristles 11b. The bristle holder 11a is a member for fixing the end of the bristles 11b and is formed of a non-metallic material. The bristle holder 11a is formed of, for example, resin. The resin is polyvinyl chloride as an example. The bristles 11b are formed of a non-metallic material. The bristles 11b are, for example, chemical fibers. Examples of the chemical fibers include polyamide-based fibers (such as nylon), polyester-based fibers (such as PET, PBT, PEN, PP), aromatic polyamide-based fibers (such as aramid), and fluororesin fibers (such as PTFE, PFA).

[0014] The plurality of brushes 11A are connected to a multi-axis unit 12 that rotates and revolves the brushes 11. The multi-axis unit 12 has a mechanism for rotating each of the plurality of brushes 11A and a mechanism for revolving the plurality of brushes 11A by rotating the rotation mechanism. The multi-axis unit 12 is connected to one or more drive sources (not shown). The plurality of brushes 11A perform a planetary motion by the multi-axis unit 12, and the surface of the wafer holding device 2 is polished uniformly.

[0015] The multi-axis unit 12 is connected to a first elevating part 13 and a second elevating part 14 and is configured to be movable up and down. The first elevating part 13 and the second elevating part 14 are, for example, electric cylinders. The second elevating part 14 can set the height adjustment more finely than the first elevating part 13. The position of the multi-axis unit 12 is finely adjusted by the second elevating part 14 after being adjusted by the first elevating part 13. Thereby, the tips of the bristles of the plurality of brushes 11 can be accurately applied to the surface of the wafer holding device 2.

[0016] Inside the case 3 of the brush polishing device 1, a liquid supply unit 15 for supplying liquid to the wafer holding device 2 on the table 10 is arranged. The liquid supply unit 15 has a nozzle arranged facing the surface of the wafer holding device 2. The liquid supply unit 15 supplies liquid from the nozzle to the surface of the wafer holding device 2 when the surface of the wafer holding device 2 is being polished by a plurality of brushes 11, realizing wet polishing. 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 enhanced. The liquid used for polishing is discharged from the discharge port 3a of the case 3 and is discharged by the discharge pump 16.

[0017] [Details of the Table and Brushes] Figures 3 and 4 are diagrams for explaining the details of the table and brushes in Figure 1. As shown in Figures 3 and 4, the table 10 has a base 10c and a contact member 10b. The contact member 10b is arranged 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 MC nylon and urethane rubber are exemplified. By making the contact portion with the wafer holding device 2 a non-metal such as resin, the adhesion of metal elements to the wafer holding device 2 is suppressed. Also, the table 10 rotates about the rotation axis Z1 by a rotation drive unit 10a. The rotation axis Z1 is a line passing through the center of the table 10 and extending in the vertical direction. On the upper surface of the table 10, locking members 10d for positioning and fixing the wafer holding device 2 are provided at predetermined intervals in the circumferential direction of the table 10. By providing the locking members 10d, the wafer holding device 2 is prevented from falling off the table 10 during polishing.

[0018] During grinding, the table 10 rotates, and each of the plurality of brushes 11A rotates and revolves. In the multi-axis unit 12, the brush 11 is supported by a rotating rod. The rotating rod is rotatably connected to the substantially disk-shaped main body of the multi-axis unit 12. Thereby, the brush 11 can rotate about a rotation axis (for example, rotation axes Z2, Z3, etc.) passing through the rotation axis. 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. Thereby, the brush 11 can revolve about the rotation axis Z4.

[0019] The blank 11b may contain an abrasive. The diameter of the abrasive is 50 μm to 80 μm, and the abrasive is contained in the blank in the range of 7 wt% to 30 wt%. Also, the density of the blank, which indicates the ratio of the occupied area of the blank to the unit area, is 40% to 95%. When the diameter of the abrasive is smaller than 50 μm, the polishing force becomes weak, and it becomes difficult to make the surface roughness of the bottom 2b between the plurality of protrusions 2a in the wafer holding device 2 an arithmetic mean roughness (Ra) of 0.5 or less as defined in JIS (Japanese Industrial Standards) B 0601; 2013. When the diameter of the abrasive is larger than 50 μm, the surface cannot be polished smoothly, and it becomes difficult to make the surface roughness of the bottom 2b an arithmetic mean roughness (Ra) of 0.5 or less. By setting the diameter of the abrasive to 50 μm to 80 μm, the surface roughness of the bottom 2b can be made an arithmetic mean roughness (Ra) of 0.5 or less, and the fluidity of the gas for wafer cooling is improved. In addition, when rounding is performed so that the outer edge portion of the upper end surface of the protrusion 2a becomes a curved surface, even if microcracks occur in the outer edge portion of the upper end surface in the process of forming the protrusion 2a, the microcracks can be removed in the process of performing the rounding. The wafer holding device 2 is exposed to an environment such as reduced pressure (vacuum), heat, or plasma during the processing of the wafer. If there are microcracks in the wafer holding device 2, destruction progresses starting from the microcracks due to environmental changes, and chipping occurs. Fragments generated by chipping adhere to the wafer and cause contamination. By performing polishing with the brush 11, it is possible to achieve both an improvement in the fluidity of the gas for wafer cooling and prevention of contamination of the wafer.

[0020] [Operation of Brush Polishing Apparatus] FIG. 5 is a flowchart showing a method of manufacturing a wafer holding device. As shown in FIG. 5, the method of manufacturing a wafer holding device includes an embossing step (S10) and a polishing step (S12). In the embossing step (S10), an emboss is formed on the surface of the wafer holding device 2. For example, a net-like 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 blasting method, for example, by line-scanning a nozzle, embossing is performed on the entire surface of the wafer holding device 2.

[0021] Subsequently, in the polishing step (S12), the wafer holding device 2 is housed in the case 3 of the brush polishing device 1. The wafer holding device 2 is disposed at a position positioned by the locking member 10d on the table 10. Then, the tips of the plurality of brushes 11A are positioned on the surface of the wafer holding device 2 by the first elevating part 13 and the second elevating part 14. Then, the rotation driving part 10a rotates the table 10, and the multi-axis unit 12 causes the plurality of brushes 11A to perform a planetary motion (rotation and revolution). When the table 10 rotates, the brush acts 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 locus, and the surface of the wafer holding device 2 can be polished uniformly. When the polishing step (S12) is completed, the flowchart shown in FIG. 5 ends.

[0022] [Summary of Embodiment] In the brush polishing apparatus 1, the wafer holding apparatus 2 is polished by a brush including a bristle material 11b formed of a non-metallic material and a bristle holder 11a formed of a non-metallic material. Since the bristle material 11b comes into strong contact with the wafer holding apparatus, there is a risk that the components of the bristle material 11b adhere to the wafer. Further, although the bristle holder 11a is generally selected to be metal in consideration of strength or productivity, there is a risk that the bristle holder 11a wears during the operation of the brush polishing apparatus 1 and a part of it falls and adheres to the wafer holding apparatus 2. As in one embodiment, since the bristle material 11b and the bristle holder 11a are formed of non-metal, the brush polishing apparatus 1 can remove the metal elements remaining on the surface of the wafer holding apparatus 2 while avoiding the mixing of metal elements, as compared with the case of using a brush including a bristle and a holder made of a metal material. Further, as in one embodiment, since the contact member 10b on the table 10 is formed of non-metal, the metal elements remaining on the surface of the wafer holding apparatus 2 can be removed while further avoiding the mixing of metal elements.

[0023] 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 may be made.

[0024] The brush polishing apparatus 1 only needs to include a table 10 and a plurality of brushes 11A, and may not include a rotational drive unit 10a, a multi-axis unit 12, a first elevating unit 13, a second elevating unit 14, and a liquid supply unit 15. The brush polishing apparatus 1 does not need to include a plurality of brushes 11A, and may include a single brush 11.

[0025] The brush polishing apparatus 1 only needs to include a removing mechanism capable of removing the metal elements remaining on the surface of the wafer holding apparatus 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 be a mechanism including a single brush that rotates, or may include a plurality of brushes 11 as shown in FIG. 3, and the plurality of brushes 11 may be a mechanism that rotates only or revolves only.

[0026] The wafer holding device 2 is not limited to an electrostatic chuck and may be a vacuum chuck.

[0027] [Summary of Embodiments of the Present Disclosure] The present disclosure includes the following aspects.

[0028] (Clause 1) A brush polishing device according to one aspect of the present disclosure includes a table that supports a wafer holding device having a plurality of convex portions on its surface, a brush material formed of a non-metallic material, and a brush material holder formed of a non-metallic material, and a brush that polishes the wafer holding device supported by the table.

[0029] In this brush polishing device, the wafer holding device is polished by a brush including a brush material formed of a non-metallic material and a brush material holder formed of a non-metallic material. Since the brush material and the brush material holder are formed of non-metals, this brush polishing device can remove metal elements remaining on the surface of the wafer holding device while avoiding the mixing of metal elements, as compared with the case of using a brush including a brush material and a holder of a metal material.

[0030] (Clause 2) In the brush polishing device according to Clause 1, the brush material may be formed of chemical fiber, and the brush material holder may be formed of resin. By using chemical fiber and resin, a non-metallic brush is configured.

[0031] (Clause 3) In the brush polishing device according to Clause 1 or 2, the brush material may include an abrasive, the diameter of the abrasive may be 50 μm to 80 μm, and the density of the brush material may be 40% to 95%. In this case, the surface roughness of the bottom surface between the protrusions formed by embossing can be made 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 wafer temperature. When 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 removing heat from the wafer temperature is made uniform in the plane. Thereby, the quality of the chips formed on the wafer is improved.

[0032] (Clause 4) In the brush polishing apparatus according to any one of Clauses 1 to 3, the table has a support surface for supporting the wafer holding device, and the support surface may be formed of a non-metal. By forming the support surface of a non-metal, the brush polishing apparatus can further avoid mixing of metal elements.

[0033] (Clause 5) The brush polishing apparatus according to any one of Clauses 1 to 4 may further include a multi-axis unit that rotates and revolves the brush. By causing the brush to perform a planetary motion by the multi-axis unit, the brush polishing apparatus can remove the directivity imparted by blasting or the like.

[0034] (Clause 6) A method for manufacturing a wafer holding device according to another aspect of the present disclosure includes a step of polishing a wafer holding device having a plurality of convex portions on its surface with a brush having a blank formed of a non-metal material and a blank holder formed of a non-metal material. The method for manufacturing a wafer holding device has the same effect as the above-described brush polishing apparatus.

Description of Reference Numerals

[0035] 1... Brush polishing apparatus, 2... Wafer holding device, 10... Table, 11... Brush, 11a... Blank holder, 11b... Blank, 12... Multi-axis unit.

Claims

1. A table for supporting a wafer holding device having a plurality of convex portions on its surface, A brush including a brush material formed of a non-metallic material and a brush material holder formed of a non-metallic material, for polishing the wafer holding device supported on the table, A brush polishing apparatus comprising the above.

2. The brush polishing apparatus according to Claim 1, wherein the brush material is formed of chemical fiber and the brush material holder is formed of resin.

3. The brush polishing apparatus according to Claim 1 or 2, wherein the brush material contains an abrasive, the diameter of the abrasive is 50 μm to 80 μm, and the density of the brush material is 40% to 95%.

4. The brush polishing apparatus according to Claim 1 or 2, wherein the table has a support surface for supporting the wafer holding device, and the support surface is formed of a non-metallic material.

5. The brush polishing apparatus according to Claim 1 or 2, further comprising a multi-axis unit for rotating and revolving the brush.

6. A method for manufacturing a wafer holding device, including a step of polishing a wafer holding device having a plurality of convex portions on its surface with a brush having a brush material formed of a non-metallic material and a brush material holder formed of a non-metallic material.

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