Electrode device and manufacturing method therefor

Abstract

The present invention is an electrode device comprising a support that joins to and holds a graphite electrode used for arc discharge for manufacturing a quartz crucible, the electrode device being characterized by having an antifouling thin film on, from among the surfaces of the support, the outermost surface layer of the portion adjacent to the graphite electrode when the support is joined to the graphite electrode. As a result of this configuration, the present invention provides an electrode device with which it is possible to suppress contamination from a support, and to shorten the graphite electrode used and thereby reduce manufacturing costs.

Description

Electrode device and manufacturing method thereof

[0001] The present invention relates to an electrode device and a manufacturing method thereof, and more particularly to an electrode device used in manufacturing a quartz crucible and a manufacturing method thereof.

[0002] Most silicon single crystals used as substrates for single-crystal semiconductor materials are produced by the so-called Czochralski method, in which polycrystalline silicon is melted in a quartz crucible, brought into contact with a seed crystal, and then crystal growth is performed. There are several types of quartz crucibles used in this silicon single crystal production method, depending on the production method. In practice, quartz crucibles are produced by filling silicon dioxide powder (raw quartz powder) along the inner circumferential surface of a rotatable hollow mold, and then heating and melting the silicon dioxide powder by arc discharge using graphite electrodes while rotating the mold. Many embodiments of graphite electrodes used in arc discharge to produce quartz crucibles have been disclosed (e.g., Patent Documents 1 to 3). The graphite electrodes are used connected to an electrode device (e.g., one having a copper support) for passing current (e.g., Patent Document 4).

[0003] Conventionally, the arc rotary melting method for producing quartz crucibles has had the problem of contamination occurring when the metal support is close to a heat source. For example, Patent Document 4, cited above, describes a method for producing a quartz glass crucible using the arc rotary melting method, in which a carbon electrode (graphite electrode) inserted into a mold is composed of a carbon rod-shaped portion and its support. It also describes extending at least a portion of the carbon rod-shaped portion above the high-temperature atmosphere in the mold, and isolating the support attached to its tip from the high-temperature atmosphere. In this way, it is disclosed that the graphite electrode is elongated to isolate the attached support from the high-temperature atmosphere. Patent Document 4 also discloses that the length of the carbon rod-shaped portion should be 20 cm to 2.5 m to isolate the support.

[0004] JP 2016-011238 A JP 2017-065962 A JP 2009-161362 A JP 8-34628 A

[0005] As described above, Patent Document 4 discloses that the graphite electrode is elongated to isolate the support from a high-temperature atmosphere. However, the longer the graphite electrode, the higher the manufacturing cost of the graphite.

[0006] The present invention has been made in view of the above circumstances, and has an object to provide an electrode device that can reduce manufacturing costs by suppressing contamination from the support and shortening the length of the graphite electrode used, as well as a manufacturing method for such an electrode device.

[0007] The present invention has been made to solve the above-mentioned problems, and provides an electrode device having a support for joining and holding a graphite electrode used in arc discharge for manufacturing a quartz crucible, characterized in that an antifouling thin film is provided on the outermost surface layer of the surface of the support, in a portion adjacent to the graphite electrode when the support is joined to the graphite electrode.

[0008] The electrode device of the present invention has an antifouling thin film on the outermost surface of the support body at a portion adjacent to the graphite electrode, thereby making it possible to suppress contamination from the support body even during arc melting.

[0009] In this case, the antifouling thin film is preferably a thermally sprayed film, and the thermally sprayed film is preferably a ceramic thermally sprayed film or an alloy thermally sprayed film.

[0010] Such ceramic or alloy sprayed films can be easily formed into thin films that are antifouling, heat-resistant, impact-resistant, and insulating, and therefore electrode devices having such thin films can more effectively suppress contamination from the support during arc melting.

[0011] Furthermore, it is preferable that the antifouling thin film covers at least the portion of the surface of the support that is inserted into a mold used in manufacturing the quartz crucible.

[0012] By forming an antifouling thin film at least in such a region, contamination from the support during arc melting can be more effectively suppressed.

[0013] The material of the antifouling thin film is preferably at least one of alumina, zirconia, mullite, chromia, yttria, titania, ceria, alloys containing these, and alloys containing nickel.

[0014] These materials can be suitably used as the material for the antifouling thin film in the electrode device of the present invention.

[0015] The material of the support preferably contains at least one of gold, silver, copper, and aluminum.

[0016] These metals are highly malleable, making it easy to fix the graphite electrodes, and also have high cooling performance and good electrical conductivity, making them preferable as materials for the support.

[0017] The antifouling thin film is preferably formed on the surface of the support via one or more underlying thin films.

[0018] In this way, by providing the undercoat thin film, it is possible to reduce the influence of the difference in thermal expansion coefficient between the material of the support and the antifouling thin film.

[0019] The present invention also provides an electrode comprising any one of the electrode devices described above joined to the graphite electrode.

[0020] Such an electrode has an antifouling thin film on the outermost surface layer of the surface of the support of the electrode device, in the area adjacent to the graphite electrode, and therefore can suppress contamination from the support even during arc melting.

[0021] In this case, it is preferable that the length of the rod-shaped portion of the graphite electrode is 50 mm or more and 500 mm or less.

[0022] If an electrode using a graphite electrode having a rod-shaped portion of such a length is used, it is possible to perform a sufficient arc discharge while being low cost.

[0023] The present invention also provides a method for manufacturing an electrode device having a support for joining and holding a graphite electrode used in arc discharge for manufacturing a quartz crucible, the method comprising the steps of: preparing the electrode device; and forming an antifouling thin film on the outermost surface layer of a portion of the surface of the support of the prepared electrode device that is adjacent to the graphite electrode when the support is joined to the graphite electrode.

[0024] By this method of manufacturing an electrode device, it is possible to manufacture an electrode device having an antifouling thin film on the outermost surface layer of the portion of the surface of the support adjacent to the graphite electrode, and the electrode device can be made to be capable of suppressing contamination from the support even during arc melting.

[0025] In this case, the step of forming the antifouling thin film is preferably carried out by thermal spraying, and the thermal spraying is preferably ceramic thermal spraying or alloy thermal spraying.

[0026] The ceramic or alloy spraying of the present invention allows for easy coating formation. This allows for the formation of a thin film with antifouling, heat resistance, impact resistance, and insulating properties by a simple method. Therefore, an electrode device having such a thin film can more effectively suppress contamination from the support during arc melting.

[0027] The antifouling thin film is preferably made of at least one of alumina, zirconia, mullite, chromia, yttria, titania, ceria, alloys containing these, and alloys containing nickel.

[0028] These materials can be suitably used as the material for the antifouling thin film in the method for producing an electrode device of the present invention.

[0029] Furthermore, it is preferable that the method further comprises a step of forming one or more layers of base thin films on the surface of the support before the step of forming the antifouling thin film, and that the antifouling thin film is formed on the base thin film.

[0030] By forming the undercoat thin film in this manner, it is possible to reduce the influence of the difference in thermal expansion coefficient between the material of the support and the antifouling thin film.

[0031] The electrode device of the present invention has an antifouling thin film on the outermost surface layer of the support, in the portion adjacent to the graphite electrode. This reduces the amount of graphite consumed in the graphite electrode that is connected to form the electrode during arc melting, thereby suppressing contamination of the quartz crucible manufactured from the support. Furthermore, the graphite electrode can be shortened, thereby reducing the cost of the graphite electrode required for manufacturing the quartz crucible. Furthermore, the amount of graphite consumed during arc melting can be reduced, thereby reducing contamination of the quartz crucible. Furthermore, because the graphite electrode can be shortened, carbon waste can be reduced, contributing to the SDGs. Furthermore, the electrode device manufacturing method of the present invention can manufacture such an electrode device.

[0032] FIG. 1 is a schematic diagram showing an example of using the electrode device of the present invention and an electrode in which the electrode device is connected to a graphite electrode for arc discharge to manufacture a quartz crucible. FIG. 2 is a schematic diagram showing another example of using the electrode device of the present invention and an electrode in which the electrode device is connected to a graphite electrode for arc discharge to manufacture a quartz crucible. FIG. 3 is a schematic diagram showing yet another example of using the electrode device of the present invention and an electrode in which the electrode device is connected to a graphite electrode for arc discharge to manufacture a quartz crucible. FIG. 4 is a schematic diagram showing an example of using a conventional electrode device and an electrode in which the electrode device is connected to a graphite electrode for arc discharge to manufacture a quartz crucible. FIG. 5 is a schematic diagram showing the electrode device of Comparative Example 2 and an electrode in which the electrode device is connected to a graphite electrode for arc discharge to manufacture a quartz crucible.

[0033] The present invention will be described in more detail below.

[0034] The electrode device of the present invention is an electrode device having a support for joining and holding a graphite electrode used in arc discharge for manufacturing a quartz crucible, characterized in that an antifouling thin film is provided on the outermost surface layer of the surface of the support, in a portion adjacent to the graphite electrode when the support is joined to the graphite electrode.

[0035] Hereinafter, specific embodiments of the electrode device of the present invention and an electrode in which the electrode device is connected to a graphite electrode will be described with reference to the drawings.

[0036] FIG. 1 shows the graphite electrode, electrode device, and electrode configurations in which these are connected together according to the present invention. The electrode device 10 shown in FIG. 1 includes a support 12 to which a graphite electrode 22 is joined and held. The graphite electrode 22 is used for arc discharge to manufacture a quartz crucible. Also shown in FIG. 1 are a mold 52, raw material powder 62 disposed within the mold 52 to be melted by arc discharge to form a quartz crucible, and a lid 54 used during arc discharge. The electrode device 10 according to the present invention includes an antifouling thin film 14 on the outermost surface of the support 12, in a region adjacent to the graphite electrode 22 when the support 12 is joined to the graphite electrode 22.

[0037] The electrode device 10 of the present invention has an antifouling thin film 14 on the outermost surface layer of the surface of the support 12, in the area adjacent to the graphite electrode 22, and therefore can suppress contamination from the support 12 even during arc melting.

[0038] The support 12 of the electrode device 10 holds the graphite electrode 22 and has, for example, a holding portion that connects to the connection portion of the graphite electrode 22. The support 12 of the electrode device 10 and the graphite electrode 22 can be connected by a known method.

[0039] The antifouling thin film 14 provided on the support 12 of the electrode device 10 of the present invention is preferably a thermal sprayed film. A known method can be used as the thermal spraying method. For example, the method disclosed in JP-A-7-316773 can be used as the ceramic thermal spraying method.

[0040] The thermal spraying of the present invention is preferably ceramic or alloy spraying. A ceramic or alloy sprayed film can be easily formed into a thin film that has antifouling properties, heat resistance, impact resistance, and insulating properties. Therefore, an electrode device having such a thin film can more effectively suppress contamination from the support during arc melting.

[0041] The material of the antifouling thin film 14 in the present invention is preferably at least one of alumina, zirconia, mullite, chromia, yttria, titania, ceria, alloys containing these, and alloys containing nickel. These materials are suitable for use as the material of the antifouling thin film in the electrode device of the present invention. In particular, among alumina and alloys containing nickel, a material called colmonoy is suitable for use.

[0042] On the other hand, the material of the support 12 of the electrode device 10 preferably contains at least one of gold, silver, copper, and aluminum. These metals are highly malleable, making it easy to fix the graphite electrode, and also have high cooling performance and good conductivity, making them preferable as materials for the support.

[0043] The antifouling thin film 14 is preferably formed on the surface of the support 12 of the electrode device 10 via one or more underlying thin films. This is because the inclusion of an underlying thin film can reduce the influence of differences in thermal expansion coefficients between the material of the support 12 and the antifouling thin film 14. The material of the underlying thin film depends on the combination of the support 12 and the antifouling thin film 14, but any known material can be used as appropriate. For example, if the support 12 is made of at least one of gold, silver, copper, and aluminum, the underlying thin film can be thermally sprayed with an alloy containing Ni as the main component and Al and Mo, followed by thermally sprayed with alumina.

[0044] The antifouling thin film 14 in the present invention preferably covers at least the portion of the surface of the support 12 that is inserted into a mold 52 used to manufacture a quartz crucible. The inside of the mold 52 is the side below the upper end of the mold 52, or, if a lid 54 is used, the side below the lid 54. In the case of the electrode device 10 and electrode 30 shown in FIG. 1, the antifouling thin film 14 covers at least the portion that is inserted into the mold 52. FIGS. 2 and 3 also show the electrode device 10 and electrode 30 of the present invention. In the case of FIG. 2, the antifouling thin film 14 also covers at least the portion that is inserted into the mold 52. In the case of FIG. 3, the entire portion that is inserted into the mold 52 is the portion of the graphite electrode 22.

[0045] On the other hand, Figure 4 shows an example in which an electrode 130, in which a graphite electrode body 122 is connected to a support 112 of an electrode device 110 that does not have an antifouling thin film, is used for arc discharge to manufacture a quartz crucible similar to those shown in Figures 1 to 3. In the case of Figure 4, since the support 112 does not have an antifouling thin film, it is necessary to form a long graphite electrode 122 in order to prevent contamination of the quartz crucible by the support 112, which results in high costs. In the cases of the present invention as shown in Figures 1 to 3, all of the embodiments can reduce costs compared to the embodiment shown in Figure 4.

[0046] In particular, in the electrode 30 of the present invention, it is preferable that the length of the rod-shaped portion of the graphite electrode 22 be 50 mm or more and 500 mm or less. An electrode 30 using a graphite electrode 22 having a rod-shaped portion of such length can perform sufficient arc discharge while being low cost. Note that the rod-shaped portion of the graphite electrode 22 refers to the portion excluding the portion that is housed inside the support 12 when the support 12 of the electrode device 10 is connected.

[0047] The present invention also provides a method for manufacturing an electrode device having a support for joining and holding a graphite electrode used in arc discharge for manufacturing a quartz crucible. This method for manufacturing an electrode device includes the steps of preparing an electrode device and forming an antifouling thin film on the outermost surface layer of a portion of the surface of the support of the prepared electrode device that will be adjacent to the graphite electrode when the support is joined to the graphite electrode. This method for manufacturing an electrode device makes it possible to manufacture an electrode device having an antifouling thin film on the outermost surface layer of a portion of the surface of the support that will be adjacent to the graphite electrode, and the electrode device can be made to be capable of suppressing contamination from the support even during arc melting.

[0048] In addition, the method for manufacturing an electrode device of the present invention may include a step of forming one or more underlayer thin films on the surface of the support before the step of forming the antifouling thin film, and the antifouling thin film may be formed on the underlayer thin film. By forming the underlayer thin film, the influence of the difference in thermal expansion coefficient between the material of the support and the antifouling thin film can be reduced.

[0049] In the manufacturing method of the electrode device of the present invention, the step of forming the antifouling thin film is preferably performed by thermal spraying. The thermal spraying of the present invention is particularly preferably ceramic thermal spraying or alloy thermal spraying. Ceramic thermal spraying or alloy thermal spraying allows for easy film formation. This allows for a thin film with antifouling properties, heat resistance, impact resistance, and insulating properties to be formed by a simple method. Therefore, an electrode device having such a thin film can more effectively suppress contamination from the support during arc melting.

[0050] The material of the antifouling thin film may be at least one of alumina, zirconia, mullite, chromia, yttria, titania, ceria, alloys containing these, and alloys containing nickel. These materials can be suitably used as the material of the antifouling thin film in the manufacturing method of the electrode device of the present invention.

[0051] The present invention will be explained in more detail below by way of examples, but the present invention is not limited to these examples and various modifications are possible without departing from the technical concept of the present invention.

[0052] Example 1 A quartz crucible was manufactured using the electrode device 10 and electrode 30 according to the embodiment of the present invention shown in FIG.

[0053] First, the electrode device 10 was prepared. The material of the support 12 of the electrode device 10 was copper. The surface of the support 12 of this electrode device 10 was spray coated within a range of 450 mm from the connection part where the graphite electrode 22 was connected. For the spray coating, first, a thin film with a thickness of less than 0.1 mm was formed as a first base thin film with a ratio of Ni:Al:Mo of approximately 85:10:5. Next, a thin film of alumina (white alumina, α-Al) was formed as a second antifouling thin film 14. ２ O ３ The thermal spray coating was carried out with a thickness of 0.2 to 0.3 mm.

[0054] A graphite electrode 22 having a rod-shaped portion length of 70 mm was connected to the support 12 of this electrode device 10 to form an electrode 30 .

[0055] Next, raw material powder 62 was placed inside mold 52. Electrode 30 was inserted into mold 52, as shown in Fig. 1, and lid 54 was installed. Support 12 was inserted into mold 52 by 150 mm.

[0056] Next, the electrode 30 was energized to generate an arc discharge, and the raw material powder 62 was melted to produce a quartz crucible.

[0057] (Example 2) A quartz crucible was manufactured using the electrode device 10 and electrode 30 shown in Fig. 2. This example was the same as Example 1, except that the range of the thermal spray coating on the surface of the support 12 was 400 mm, the length of the rod-shaped portion of the graphite electrode 22 was 130 mm, and the insertion length of the support 12 into the mold 52 was 100 mm.

[0058] (Example 3) A quartz crucible was manufactured using the electrode device 10 and electrode 30 shown in Figure 3. This example was the same as Example 1, except that the area of ​​the thermal spray coating on the surface of the support 12 was 300 mm, the length of the rod-shaped portion of the graphite electrode 22 was 300 mm, and the support 12 was not inserted inside the mold 52.

[0059] (Comparative Example 1) A quartz crucible was manufactured using the electrode device 110 and electrode 130 shown in Figure 4. In Comparative Example 1, the support 112 was not spray-coated. The length of the rod-shaped portion of the graphite electrode 122 was set to 600 mm, and the support 112 was not inserted into the mold 52. The rest of the process was the same as in Example 1.

[0060] (Comparative Example 2) A quartz crucible was manufactured using the electrode device 110 and electrode 130 shown in Fig. 5. In Comparative Example 2, the support 112 was not subjected to thermal spray coating. The length of the rod-shaped portion of the graphite electrode 122 was set to 130 mm, and the length of the support 112 inserted into the mold 52 was set to 100 mm. The rest of the process was the same as in Example 1.

[0061] [Comparison of Examples 1 to 3 with Comparative Examples 1 and 2] Bulk analysis was performed on the inner surface layer of 1 mm of each of the quartz crucibles manufactured in Examples 1 to 3 and Comparative Examples 1 and 2, and the impurity concentrations were measured. The conditions and results for each Example and Comparative Example are summarized in Table 1.

[0062]

[0063] The measurement results of the impurity concentration showed that contamination by Cu was observed in Comparative Example 2. Regarding the Fe concentration, there is no problem if it is at the level shown in Table 1 above. Meanwhile, in Comparative Example 1, the manufacturing cost of the graphite electrode 122 was significantly higher than the manufacturing cost of the graphite electrode 22 in Examples 1 to 3. Furthermore, the manufacturing cost of the graphite electrode 22 was the cheapest in Example 1, and increased in the order of Examples 2 and 3, but all were cheaper than Comparative Example 1.

[0064] A comprehensive evaluation was made based on the degree of contamination based on the concentration of metal impurities and the manufacturing cost of the graphite electrode, and the evaluation was made as follows: good: ◯, fair: Δ, unacceptable: ×. The results are shown in Table 1.

[0065] This specification includes the following inventions. [1]: An electrode device having a support for joining and holding a graphite electrode used in arc discharge for manufacturing a quartz crucible, the electrode device being characterized in that an antifouling thin film is provided on the outermost surface layer of a portion of the surface of the support that is adjacent to the graphite electrode when the support is joined to the graphite electrode. [2]: The electrode device of [1] above, in which the antifouling thin film is a thermally sprayed film. [3]: The electrode device of [1] or [2] above, in which the antifouling thin film covers at least a portion of the surface of the support that is inserted into a mold used in manufacturing the quartz crucible. [4]: ​​The electrode device of any of [1] to [3] above, in which the antifouling thin film is a thermally sprayed ceramic film or a thermally sprayed alloy film. [5]: The electrode device of any one of [1] to [4] above, wherein the material of the antifouling thin film is at least one of alumina, zirconia, mullite, chromia, yttria, titania, ceria, alloys containing these, and alloys containing nickel. [6]: The electrode device of any one of [1] to [5] above, wherein the material of the support includes at least one of gold, silver, copper, and aluminum. [7]: The electrode device of any one of [1] to [6] above, wherein the antifouling thin film is formed on the surface of the support via one or more underlayer thin films. [8]: An electrode obtained by joining the electrode device of any one of [1] to [7] above to the graphite electrode. [9]: The electrode of [8] above, wherein the length of the rod-shaped portion of the graphite electrode is 50 mm or more and 500 mm or less.

[10] : A method for manufacturing an electrode device having a support for joining and holding a graphite electrode used in arc discharge for manufacturing a quartz crucible, comprising the steps of: preparing the electrode device; and forming an antifouling thin film on the outermost surface layer of a portion of the surface of the support for the prepared electrode device that is adjacent to the graphite electrode when the support is joined to the graphite electrode.

[11] : A method for manufacturing an electrode device according to

[10] , in which the step of forming the antifouling thin film is carried out by thermal spraying.

[12] : A method for manufacturing an electrode device according to

[10] or

[11] above, wherein the step of forming the antifouling thin film is carried out by ceramic spraying or alloy spraying.

[13] : A method for manufacturing an electrode device according to any of

[10] to

[12] above, wherein the material of the antifouling thin film is at least one of alumina, zirconia, mullite, chromia, yttria, titania, ceria, alloys containing these, and alloys containing nickel.

[14] : A method for manufacturing an electrode device according to any of

[10] to

[13] above, comprising a step of forming one or more underlayer thin films on the surface of the support before the step of forming the antifouling thin film, and the antifouling thin film is formed on the underlayer thin film.

[0066] The present invention is not limited to the above-described embodiments, which are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that provides similar effects is included within the technical scope of the present invention.

Claims

1. An electrode device having a support for joining and holding a graphite electrode used in arc discharge for manufacturing a quartz crucible, characterized in that the support has an antifouling thin film on the outermost surface layer of a portion of the surface of the support that is adjacent to the graphite electrode when the support is joined to the graphite electrode.

2. The electrode device according to claim 1, wherein the antifouling thin film is a thermally sprayed film.

3. An electrode device as described in claim 1, characterized in that the anti-fouling thin film covers at least the portion of the surface of the support that is inserted into a form used in manufacturing the quartz crucible.

4. The electrode device according to claim 1, wherein the antifouling thin film is a ceramic sprayed film or an alloy sprayed film.

5. The electrode device according to claim 1, characterized in that the material of the antifouling thin film is at least one of alumina, zirconia, mullite, chromia, yttria, titania, ceria, alloys containing these, and alloys containing nickel.

6. The electrode device according to claim 1, characterized in that the material of said support contains at least one of gold, silver, copper and aluminum.

7. The electrode device according to claim 1, wherein the antifouling thin film is formed on the surface of the support via one or more underlying thin films.

8. An electrode comprising the electrode device according to any one of claims 1 to 7 joined to the graphite electrode.

9. The electrode according to claim 8, characterized in that the length of the rod-shaped portion of said graphite electrode is 50 mm or more and 500 mm or less.

10. A method for manufacturing an electrode device having a support for joining and holding a graphite electrode used in arc discharge for manufacturing a quartz crucible, comprising the steps of: preparing the electrode device; and forming an anti-fouling thin film on the outermost surface layer of a portion of the surface of the support for the prepared electrode device that is adjacent to the graphite electrode when the support is joined to the graphite electrode.

11. The method for manufacturing an electrode device according to claim 10, wherein the step of forming the antifouling thin film is carried out by thermal spraying.

12. The method for manufacturing an electrode device according to claim 10, wherein the step of forming the antifouling thin film is carried out by ceramic spraying or alloy spraying.

13. A method for manufacturing an electrode device as described in claim 10, characterized in that the material of the antifouling thin film is at least one of alumina, zirconia, mullite, chromia, yttria, titania, ceria, alloys containing these, and alloys containing nickel.

14. A method for manufacturing an electrode device as described in claim 10, characterized in that it includes a step of forming one or more layers of a base thin film on the surface of the support prior to the step of forming the antifouling thin film, and the antifouling thin film is formed on the base thin film.

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