Method for producing silicon carbide

Abstract

This invention provides a method for producing silicon carbide that can reduce electricity consumption, minimize environmental impact, and produce high-purity silicon carbide. [Solution] The invention is characterized by comprising an SiO gas generation step S01 in which a Si raw material and an SiO2 raw material are reacted to generate SiO gas, and a silicon carbide synthesis step S02 in which the generated SiO gas is brought into contact with a carbon source to synthesize silicon carbide. Preferably, the amount of impurities contained in the Si raw material is 2 mass% or less, and the amount of impurities contained in the SiO2 raw material is 3 mass% or less.

Description

[Technical Field]

[0001] This invention relates to a method for producing silicon carbide. [Background technology]

[0002] Silicon carbide (SiC) has been widely used as an industrial material in applications such as abrasives, ceramic sintered bodies, and conductive materials. Recently, against a backdrop of growing energy conservation trends and expectations for the use of natural renewable energy following the phasing out of nuclear power, it has attracted attention as a raw material for single-crystal wafers used in power semiconductors and as a component of semiconductor manufacturing equipment.

[0003] Here, known technologies for the industrial mass production of silicon carbide include the Acheson process, which uses siliceous raw materials containing silicon (e.g., silica sand) and carbonaceous raw materials containing carbon (e.g., petroleum coke) as raw materials and heats these raw materials to over 1600°C by directly applying electricity in an electric furnace to produce silicon carbide, and the direct reduction method of silica, which produces silicon carbide by heating a mixture of silica powder and carbon powder to 1600-2000°C and sintering it.

[0004] For example, Patent Documents 1 and 2 disclose a method for producing silicon carbide by mixing silica (SiO2) raw material and carbon material and then heat-treating them. Furthermore, Patent Documents 3 and 4 disclose a method for producing silicon carbide by directly reacting silicon (Si) and carbon. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2021-143098 [Patent Document 2] Special Publication No. 10-500933 [Patent Document 3] Japanese Patent Publication No. 2001-247381 [Patent Document 4] Japanese Patent Publication No. 2001-199767 [Overview of the project] [Problems that the invention aims to solve]

[0006] Incidentally, the silicon carbide production methods described in Patent Documents 1-4 involve reacting silicon (Si) or silica (SiO2) raw materials with a carbon source, which results in high power consumption and a very large environmental impact (due to the large amount of dust, CO / CO2, and SO2 emissions). Furthermore, since the purity of the silicon carbide produced is affected by the purity of the raw materials, such as silicon (Si) and silica (SiO2), it was necessary to use high-purity silicon (Si) and silica (SiO2) raw materials. This resulted in the problem of requiring significant raw material costs to produce high-quality silicon carbide.

[0007] This invention has been made in view of the circumstances described above, and aims to provide a method for producing silicon carbide that can reduce electricity consumption, minimize environmental impact, and produce high-purity silicon carbide. [Means for solving the problem]

[0008] To solve the above problems, the inventors conducted diligent research and found that by reacting Si and SiO2 to generate SiO2 gas, and then reacting this SiO2 gas with a carbon source, the reaction becomes a gas-solid reaction, significantly reducing power consumption and environmental impact. Furthermore, they found that by reacting Si and SiO2 to generate SiO2 gas, impurities contained in the Si and SiO2 raw materials do not migrate to the silicon carbide, making it possible to produce high-purity silicon carbide.

[0009] The present invention is based on the above-mentioned findings, and the method for producing silicon carbide according to embodiment 1 of the present invention is characterized by comprising: an SiO gas generation step of reacting a Si raw material and an SiO2 raw material to generate SiO gas; and a silicon carbide synthesis step of contacting the generated SiO gas with a carbon source to synthesize silicon carbide.

[0010] In the silicon carbide production method of Embodiment 1 of the present invention, since SiO gas is generated by reacting Si raw material and SiO2 raw material in the SiO gas generation step, impurities contained in the Si raw material and SiO2 raw material are removed when SiO gas is generated. Then, in the silicon carbide synthesis step, silicon carbide is synthesized by contacting the generated SiO gas with a carbon source, making it possible to produce high-purity silicon carbide. Furthermore, in the silicon carbide synthesis process, silicon carbide is synthesized by contacting the generated SiO gas with a carbon source, resulting in a reaction between a gas and a solid, which significantly reduces power consumption and environmental impact.

[0011] The silicon carbide production method of aspect 2 of the present invention is characterized in that, in the silicon carbide production method of aspect 1 of the present invention, the amount of impurities contained in the Si raw material is 2 mass% or less, and the amount of impurities contained in the SiO2 raw material is 3 mass% or less. According to the silicon carbide production method of embodiment 2 of the present invention, the amount of impurities contained in the Si raw material is 2 mass% or less, and the amount of impurities contained in the SiO2 raw material is 3 mass% or less, so raw material costs can be reduced. Furthermore, even if the Si raw material and the SiO2 raw material contain a relatively large amount of impurities, it is possible to produce high-purity silicon carbide.

[0012] The silicon carbide production method of embodiment 3 of the present invention is characterized in that, in the silicon carbide production method of embodiment 1 or embodiment 2 of the present invention, the Si raw material is Si waste generated in the Si semiconductor manufacturing process. According to the method for producing silicon carbide of Embodiment 3 of the present invention, since the Si raw material is Si waste generated in the Si semiconductor manufacturing process, it is possible to further reduce the raw material cost.

[0013] The method for producing silicon carbide of Embodiment 4 of the present invention is characterized in that, in the method for producing silicon carbide according to any one of Embodiments 1 to 3 of the present invention, the SiO2 raw material is SiO2 waste generated in the Si semiconductor manufacturing process. According to the method for producing silicon carbide of Embodiment 4 of the present invention, since the SiO2 raw material is SiO2 waste generated in the Si semiconductor manufacturing process, it is possible to further reduce the raw material cost.

[0014] The method for producing silicon carbide of Embodiment 5 of the present invention is characterized in that, in the method for producing silicon carbide according to any one of Embodiments 1 to 4 of the present invention, the carbon concentration of the carbon source is 99 mass% or more. According to the method for producing silicon carbide of Embodiment 5 of the present invention, since the carbon concentration of the carbon source is 99 mass% or more, it is possible to reliably produce high-purity silicon carbide.

Effect of the Invention

[0015] According to the present invention, it is possible to provide a method for producing silicon carbide that can reduce the amount of power used, suppress the environmental load, and produce high-purity silicon carbide.

Brief Description of the Drawings

[0016] [Figure 1] It is a flowchart of the method for producing silicon carbide which is an embodiment of the present invention. [Figure 2] It is an explanatory drawing showing an example of a silicon carbide manufacturing apparatus for carrying out the method for producing silicon carbide which is an embodiment of the present invention.

Mode for Carrying Out the Invention

[0017] The following describes an embodiment of the present invention, a method for producing silicon carbide, with reference to the attached drawings. The embodiments described below are provided specifically to better illustrate the spirit of the invention and do not limit the present invention unless otherwise specified.

[0018] An embodiment of the present invention is a method for producing silicon carbide, which is used, for example, as an abrasive, a ceramic sintered body, a conductive material, a component of semiconductor manufacturing equipment, and a raw material for SiC wafers. In this embodiment, silicon carbide is produced for use as a raw material for SiC semiconductor manufacturing equipment components. For SiC semiconductor manufacturing equipment components, silicon carbide with a purity of 99.9 mass% or higher is required.

[0019] In this embodiment of the silicon carbide production method, as shown in the flow chart of Figure 1, the method comprises an SiO gas generation step S01 in which a Si raw material and an SiO2 raw material are reacted to generate SiO gas, and a silicon carbide synthesis step S02 in which the generated SiO gas is brought into contact with a carbon source to synthesize silicon carbide.

[0020] (SiO gas generation process S01) First, the Si raw material and the SiO2 raw material are reacted to generate SiO gas as shown in equation (1) below. (1) Formula: Si(s)+SiO2(s)→2SiO(g)

[0021] In the SiO gas generation process S01, as described above, SiO gas is generated by reacting the Si raw material and the SiO2 raw material. Therefore, impurities contained in the Si raw material and the SiO2 raw material are removed without being transferred to the SiO gas. Therefore, it is not necessary to use high-purity materials as Si and SiO2 raw materials, which can reduce raw material costs.

[0022] In this case, it is preferable that the amount of impurities contained in the Si raw material is within the range of 2 mass% or less. Furthermore, it is even more preferable that the upper limit of the amount of impurities contained in the Si raw material is 1 mass% or less. There is no particular lower limit for the amount of impurities contained in the Si raw material, but it is preferable that it be 0 mass%.

[0023] Furthermore, it is preferable that the amount of impurities contained in the SiO2 raw material is within the range of 3 mass% or less. Furthermore, it is even more preferable that the upper limit of the amount of impurities contained in the SiO2 raw material is 1 mass% or less. There is no particular lower limit for the amount of impurities contained in the SiO2 raw material, but it is preferable that it be 0 mass%.

[0024] In this embodiment of the silicon carbide manufacturing method, Si waste generated in the Si semiconductor manufacturing process may be used as the Si raw material. Si waste generated in the Si semiconductor manufacturing process includes, for example, cutting scraps from silicon ingots, polishing scraps from silicon wafers, and processing scraps. In this Si waste, the amount of impurities contained is within the range of 0 mass% to 2 mass%.

[0025] Furthermore, in the silicon carbide manufacturing method of this embodiment, SiO2 waste generated in the Si semiconductor manufacturing process may be used as the SiO2 raw material. Examples of SiO2 waste generated in the Si semiconductor manufacturing process include crushed debris from used silica crucibles, fillers, and glass fragments. These SiO2 waste materials contain impurities ranging from 0 mass% to 3 mass%.

[0026] In order to efficiently generate SiO gas, the mass ratio of Si raw material to SiO2 raw material [Si] / [SiO2] is preferably 0.47 or higher, and more preferably 1 or higher. Furthermore, [Si] / [SiO2] is preferably 100 or lower, and more preferably 50 or lower.

[0027] Also, the average particle size D of the Si raw material SiThe lower limit is preferably 10 μm or more, more preferably 100 μm or more. On the other hand, the average particle size D of the Si raw material Si The upper limit is preferably 100 mm or less, more preferably 50 mm or less.

[0028] Furthermore, the average particle size D of the SiO2 raw material SiO2 The lower limit is preferably 0.1 μm or more, more preferably 1 μm or more. On the other hand, the average particle size D of the SiO2 raw material [[ID=**9**]] SiO2 The upper limit is preferably 10 mm or less, more preferably 1 mm or less.

[0029] Also, the ratio D Si of the average particle size D of the Si raw material to the average particle size D SiO2 of the SiO2 raw material, D Si / D SiO2 is more preferably 1 or more. Also, D Si / D SiO2 is preferably 500 or less, more preferably 100 or less.

[0030] (Silicon carbide synthesis step S02) Next, the generated SiO gas and the carbon source are brought into contact to synthesize silicon carbide as shown in the following formula (2). (Formula (2): SiO(g) + C(s) → SiC(s) + CO(g))

[0031] As described above, in the silicon carbide synthesis step S02, since it is a reaction between a gas (SiO gas) and a solid (carbon source), the reaction proceeds easily and silicon carbide can be efficiently produced. Here, as the carbon source, the carbon concentration is preferably 99 mass% or more. Note that as the above-mentioned carbon source, for example, it is preferable to use a used product of a carbon member used in the Si semiconductor manufacturing process. The silicon carbide produced in this way preferably has a purity of 99.9% or more.

[0032] Next, an example of the procedure for specifically carrying out the silicon carbide production method according to this embodiment will be explained using the silicon carbide production apparatus 10 shown in Figure 2.

[0033] The silicon carbide production apparatus 10 shown in Figure 2 comprises a furnace body 11, a crucible 12 disposed inside the furnace body 11, a carbon source arrangement section 13 disposed in the upper space inside the crucible 12, and a heating means 14 for heating the crucible 12.

[0034] First, a mixed raw material 21 of Si raw material and SiO2 raw material is loaded into the lower part of the crucible 12. Next, a carbon material 22 (carbon felt in this embodiment), which will serve as the carbon source, is placed in the carbon source placement section 13 located in the upper space inside the crucible 12. Then, the crucible 12 is heated and maintained by the heating means 14, and the Si raw material and SiO2 raw material in the mixed raw materials 21 are reacted to generate SiO gas, and the generated SiO gas is reacted with the carbon material 22, which serves as a carbon source, to synthesize SiC.

[0035] In other words, in this embodiment, the SiO gas generation step S01 and the silicon carbide synthesis step S02 are carried out simultaneously. Here, it is preferable that the heating temperature in the SiO gas generation step S01 and the silicon carbide synthesis step S02 be within the range of 1450°C to 2000°C.

[0036] In this embodiment of the silicon carbide manufacturing method, which has the above configuration, SiO gas is generated by reacting Si raw material and SiO2 raw material in the SiO gas generation step S01. Therefore, impurities contained in the Si raw material and SiO2 raw material are removed when SiO gas is generated. In the silicon carbide synthesis step S02, silicon carbide is synthesized by contacting the SiO gas from which impurities have been removed with a carbon source. This makes it possible to manufacture high-purity silicon carbide. Furthermore, in the silicon carbide synthesis process S02, silicon carbide is synthesized by contacting the generated SiO gas with a carbon source. This is a gas-solid reaction, which proceeds easily and significantly reduces power consumption and environmental impact.

[0037] In this embodiment of the silicon carbide production method, if the amount of impurities in the Si raw material is within the range of 0 mass% to 2 mass% and the amount of impurities in the SiO2 raw material is within the range of 0 mass% to 3 mass%, then it is not necessary to use high-purity Si and SiO2 raw materials, and raw material costs can be reduced. Furthermore, as described above, since the method includes an SiO gas generation step S01, it is possible to produce high-purity silicon carbide even if the Si and SiO2 raw materials contain a relatively large amount of impurities.

[0038] In the silicon carbide manufacturing method of this embodiment, if the Si raw material is Si waste generated in the Si semiconductor manufacturing process, it becomes possible to further reduce raw material costs.

[0039] In the silicon carbide manufacturing method of this embodiment, if the SiO2 raw material is SiO2 waste generated in the Si semiconductor manufacturing process, it becomes possible to further reduce raw material costs.

[0040] In the silicon carbide production method of this embodiment, if the carbon concentration of the carbon source is 99 mass% or higher, it is possible to reliably produce high-purity silicon carbide.

[0041] Although one embodiment of the present invention has been described above, the present invention is not limited thereto and can be modified as appropriate without departing from the technical spirit of the invention. For example, although this embodiment has been described using the silicon carbide production apparatus shown in Figure 2, it is not limited to this, and silicon carbide may be produced using an apparatus with other configurations as long as it has an SiO gas generation step S01 and a silicon carbide synthesis step S02.

[0042] Furthermore, although this embodiment describes the SiO gas generation step S01 and the silicon carbide synthesis step S02 as being carried out simultaneously, they do not need to be transferred to each other and may be carried out as separate, independent steps. Furthermore, although this embodiment describes the use of waste generated in the Si semiconductor manufacturing process as a raw material, it is not limited to this, and other Si raw materials, SiO2 raw materials, or carbon sources may also be used. [Examples]

[0043] The verification experiments conducted to confirm the effectiveness of the present invention will be described.

[0044] Silicon carbide was produced using the silicon carbide production apparatus shown in Figure 2. The Si and SiO2 raw materials shown in Table 1 were loaded into the crucible. In addition, the carbon source (carbon felt) shown in Table 1 was placed in the carbon source section. Then, silicon carbide was produced by heat treatment under the conditions shown in Table 1, and the SiO gas generation process and the silicon carbide synthesis process were carried out simultaneously.

[0045] XRD measurements were performed on the carbon felt after heat treatment to evaluate the presence or absence of silicon carbide formation. The evaluation results are shown in Table 1. Furthermore, the silicon carbide obtained as described above was analyzed for impurity elements. The analysis results are shown in Table 1.

[0046] [Table 1]

[0047] In this example, XRD measurements confirmed the synthesis of silicon carbide. Silicon carbide could be efficiently produced even under relatively low temperature conditions. The synthesized silicon carbide was β-SiC. Furthermore, it has been confirmed that high-purity silicon carbide can be produced regardless of the purity of the Si and SiO2 raw materials.

[0048] As described above, it has been confirmed that the present invention provides a method for producing silicon carbide that can reduce electricity consumption, minimize environmental impact, and produce high-purity silicon carbide.

Claims

1. Si raw material and SiO ２ A process of generating SiO gas by reacting raw materials, A silicon carbide synthesis process involves contacting the generated SiO gas with a carbon source to synthesize silicon carbide, A method for producing silicon carbide, characterized by comprising the following features.

2. The amount of impurities contained in the Si raw material is 2 mass% or less, and the SiO ２ A method for producing silicon carbide according to claim 1, characterized in that the amount of impurities contained in the raw materials is 3 mass% or less.

3. The method for producing silicon carbide according to claim 1 or 2, characterized in that the Si raw material is Si waste generated in the Si semiconductor manufacturing process.

4. The SiO ２ The raw material is SiO2, which is generated in the Si semiconductor manufacturing process. ２ A method for producing silicon carbide according to claim 1 or 2, characterized in that it is waste.

5. A method for producing silicon carbide according to claim 1 or 2, characterized in that the carbon concentration of the carbon source is 99 mass% or more.

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