Production method of high-purity silicon carbide powder

Abstract

To provide a method for producing high-purity silicon carbide powder with a simple process.SOLUTION: A method for producing high-purity silicon carbide powder includes performing: a step of providing raw material silicon carbide powder having a silicon carbide purity of 90.0 wt.% or more and less than 99.0 wt.%; a first heating step of heating the raw material silicon carbide powder in an inert atmosphere at 1800 to 2200°C while bringing the raw material silicon carbide powder into contact with a carbon sheet to obtain an intermediate silicon carbide powder; and a second heating step of heating the intermediate silicon carbide powder in an oxidizing atmosphere at 500 to 700°C to obtain the high-purity silicon carbide powder having the silicon carbide purity of 99.0 wt.% or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for producing high-purity silicon carbide powder.

Background Art

[0002] Due to its high hardness, silicon carbide may be used for cutting, polishing, etc. of silicon semiconductors in the semiconductor manufacturing process. However, in the semiconductor manufacturing process, it is required to avoid contamination by impurities. Therefore, high-purity silicon carbide may be required.

[0003] Regarding the production of silicon carbide, a production method by the Acheson method is known. The Acheson method is a method in which a carbon material and silica sand or quartz sand are heated at 1700-2500°C in an electric resistance furnace to produce silicon carbide by a carbon reduction method. However, in the case of the Acheson method, there is a problem that the impurity content in the raw materials is high and it is difficult to control the amount of impurities contained in the produced silicon carbide.

[0004] Patent Document 1 discloses a method for producing high-purity silicon carbide powder by hydrofluoric acid treatment.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the method described in Patent Document 1, a step of immersing silicon carbide powder in hydrofluoric acid is performed. However, since hydrofluoric acid is harmful to the human body and difficult to handle, a method for producing high-purity silicon carbide powder in a simple process while avoiding the use of hydrofluoric acid has been desired.

[0007] The present invention has been made in view of the above problems, and an object thereof is to provide a method for producing high-purity silicon carbide powder by a simple process.

Means for Solving the Problems

[0008] The method for producing high-purity silicon carbide powder of the present invention includes a step of preparing raw silicon carbide powder having a silicon carbide purity of 90.0% by weight or more and less than 99.0% by weight, a first heating step of bringing the raw silicon carbide powder into contact with a carbon sheet and heating it in an inert atmosphere at 1800 to 2200°C to obtain intermediate silicon carbide powder, and a second heating step of heating the intermediate silicon carbide powder in an oxidizing atmosphere at 500 to 700°C to obtain high-purity silicon carbide powder having a silicon carbide purity of 99.0% by weight or more.

[0009] In the method for producing high-purity silicon carbide powder of the present invention, in the first heating step, impurities such as metals and metal oxides contained in the raw silicon carbide powder are adsorbed on the carbon sheet, and intermediate silicon carbide powder from which these impurities have been removed is obtained. Since carbon derived from the carbon sheet adheres to the intermediate silicon carbide powder, carbon is burned in the second heating step performed in an oxidizing atmosphere, and high-purity silicon carbide powder having a silicon carbide purity of 99.0% by weight or more from which both the impurities contained in the raw silicon carbide powder and the carbon attached in the first heating step have been removed is obtained. In this step, in the present invention, at least the raw silicon carbide powder and the carbon sheet may be used as raw materials, and it is not necessary to use a material that is difficult to handle such as hydrofluoric acid. Further, since the high purity of the silicon carbide powder can be achieved only by performing a heating step in which the heating atmosphere and the heating temperature are changed, the process is simple.

[0010] In the method for producing high-purity silicon carbide powder of the present invention, the weight ratio of the raw silicon carbide powder to the carbon sheet (raw silicon carbide powder / carbon sheet) is preferably 1.0 to 5.0.

[0011] When the above weight ratio exceeds 5.0, the proportion of the carbon sheet to the raw material silicon carbide powder is insufficient, and there may be a case where the carbon sheet cannot adsorb all the impurities contained in the raw material silicon carbide powder. Further, even if the above weight ratio is less than 1.0, the increase in the proportion of the carbon sheet does not contribute to the purification of the silicon carbide powder, so the above weight ratio is preferably 1.0 or more.

[0012] In the method for producing high-purity silicon carbide powder of the present invention, a first carbon sheet and a second carbon sheet are prepared as the carbon sheet, and they are laminated in the order of the first carbon sheet, the raw material silicon carbide powder, and the second carbon sheet, and it is preferable to perform a first heating step with the raw material silicon carbide powder sandwiched between the carbon sheets.

[0013] With the above method, the impurities contained in the raw material silicon carbide powder are preferably adsorbed by the carbon sheets arranged on the upper and lower surfaces of the raw material silicon carbide powder. Further, since it is possible to transport the silicon carbide powder while sandwiching it with the carbon sheet, the handling of the silicon carbide powder in each step becomes easy.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present invention will be specifically described. However, the present invention is not limited to the following embodiments, and can be appropriately modified and applied without changing the gist of the present invention.

[0016] The method for producing high-purity silicon carbide powder of the present invention includes a step of preparing raw silicon carbide powder with a silicon carbide purity of 90.0% by weight or more and less than 99.0% by weight, a first heating step of bringing the raw silicon carbide powder into contact with a carbon sheet and heating it in an inert atmosphere at 1800 to 2200 °C to obtain intermediate silicon carbide powder, and a second heating step of heating the intermediate silicon carbide powder in an oxidizing atmosphere at 500 to 700 °C to obtain high-purity silicon carbide powder with a silicon carbide purity of 99.0% by weight or more.

[0017] (Method for measuring the concentration of each element and compound and method for measuring the purity of silicon carbide) The concentration of each element and compound in the silicon carbide powder can be measured by the following method.

[0018] The concentration of free carbon in the silicon carbide powder can be measured by the combustion volumetric method. In the combustion volumetric method, a combustion aid is added to the sample and burned in an oxygen stream to completely oxidize the carbon content to carbon dioxide, which is collected together with oxygen in a burette to measure the volume of the total gas. Next, after absorbing and removing carbon dioxide, the volume of the residual gas is measured, and the total carbon is quantified from the decrease in volume. The measurement can be carried out in accordance with JIS R6124 (1998) "Chemical analysis methods for silicon carbide abrasive materials".

[0019] The concentration of free silicon oxide in the silicon carbide powder can be measured by the neutralization titration method. In the neutralization titration method, hydrofluoric acid (containing potassium fluoride) and hydrochloric acid are added to the sample and heated to precipitate free silicic acid as potassium fluorosilicate, which is dissolved in hot water and titrated with a 0.1 mol / l sodium hydroxide solution to quantify the surface silicic acid. The measurement can be carried out in accordance with JIS R6124 (1998) "Chemical analysis methods for silicon carbide abrasive materials".

[0020] The concentration of oxides other than silicon oxide (metal oxides, sulfur oxides, phosphorus oxides) in the silicon carbide powder can be carried out by XRF-SQX (X-ray fluorescence - Scan Quant X analysis). The SQX (Scan Quant X) analysis is an analytical program that uses the FP (Fundamental Parameter) method to calculate semi-quantitative values for components detected by qualitative analysis without using a standard sample.

[0021] (Purity of silicon carbide powder) For silicon carbide powder, the purity of the silicon carbide powder can be determined by measuring the contents of free carbon, free silicon oxide, and oxides other than free silicon oxide, which are components other than silicon carbide, by the above measurement.

[0022] In the method for producing high-purity silicon carbide powder of the present invention, as the raw material silicon carbide powder, those with a silicon carbide purity of 90.0% by weight or more and less than 99.0% by weight are used. The raw material silicon carbide powder may contain carbon, metals, silicon oxides, oxides other than silicon oxides (metal oxides, sulfur oxides, phosphorus oxides), etc. By subjecting the above raw material silicon carbide powder to the treatment according to the method for producing high-purity silicon carbide powder of the present invention, high-purity silicon carbide powder with a silicon carbide purity of 99.0% by weight or more can be obtained.

[0023] In the method for producing high-purity silicon carbide powder of the present invention, first, a step of preparing a raw material silicon carbide powder with a silicon carbide purity of 90.0% by weight or more and less than 99.0% by weight is performed. The average particle size of the raw material silicon carbide powder is not particularly limited, but it is preferably a powder with an average particle size of 0.5 to 50 μm.

[0024] Subsequently, a first heating step is performed. In the first heating step, the raw material silicon carbide powder is brought into contact with a carbon sheet and heated in an inert atmosphere at 1800 to 2200 °C to obtain intermediate silicon carbide powder.

[0025] In the first heating step, it is preferable to prepare a first carbon sheet and a second carbon sheet as the carbon sheets, stack them in the order of the first carbon sheet, the raw material silicon carbide powder, and the second carbon sheet, and sandwich the raw material silicon carbide powder with the carbon sheets to perform the first heating step.

[0026] FIG. 1 is a cross-sectional view schematically showing an example of a form in which a first heating step is performed in a firing furnace. In the form shown in FIG. 1, the first heating step is performed by arranging the carbon sheet 20 and the raw material silicon carbide powder 10 in the carbon container 100 disposed in the firing furnace 200. In the firing furnace 200, heaters 130 are installed above and below the carbon container 100, and a heat insulating material 150 surrounding the carbon container 100 and the heaters 130 is provided. Place the carbon sheet 20 on the bottom surface 110 of the carbon container, and arrange the raw material silicon carbide powder 10 on the carbon sheet 20. Further, place the carbon sheet 20 on the raw material silicon carbide powder 10. In FIG. 1, the carbon sheet disposed under the raw material silicon carbide powder 10 is the first carbon sheet 21, and the carbon sheet disposed above the raw material silicon carbide powder 10 is the second carbon sheet 22. That is, in the form shown in FIG. 1, the raw material silicon carbide powder 10 is sandwiched between the first carbon sheet 21 and the second carbon sheet 22.

[0027] In the first heating step, the raw material silicon carbide powder 10 and the carbon sheet 20 are placed in contact with each other in the carbon container 100, the carbon container 100 is placed in the firing furnace 200, and the atmosphere in the internal space 120 of the carbon container 100 is heated as an inert atmosphere at 1800 to 2200°C.

[0028] By the first heating step, impurities such as metals and metal oxides contained in the raw material silicon carbide powder can be adsorbed on the carbon sheet, and intermediate silicon carbide powder from which these impurities have been removed can be obtained.

[0029] The carbon sheet preferably has a shape that does not collapse so that it can be separated from the intermediate silicon carbide powder after the first heating step. In particular, it is preferably one that does not collapse due to heating in the first heating step. As the carbon sheet, a felt of carbon fiber, a non-woven fabric, a porous body made of carbon, etc. can be used. The carbon sheet preferably has a larger specific surface area than a dense body (bulk) of carbon so that impurities are easily adsorbed. In the case of a felt of carbon fiber, a non-woven fabric, or a porous body made of carbon, the specific surface area becomes larger than that of the dense body (bulk) of carbon.

[0030] A plurality of carbon sheets may be stacked. The number of carbon sheets stacked is not particularly limited, but for example, it can be 2 to 5 sheets. When a plurality of carbon sheets are stacked and raw material silicon carbide powder is sandwiched between the carbon sheets, the plurality of carbon sheets on the same side with respect to the raw material silicon carbide powder are collectively referred to as the first carbon sheet and the second carbon sheet.

[0031] The thickness of the carbon sheet is not particularly limited, but the thickness of one carbon sheet is preferably 1 to 10 mm. Further, when a plurality of carbon sheets are stacked, the total thickness of the plurality of sheets is preferably 1 to 10 mm.

[0032] The weight ratio of the raw material silicon carbide powder to the carbon sheet (raw material silicon carbide powder / carbon sheet) is preferably 1.0 to 5.0. The weight ratio of the raw material silicon carbide powder to the carbon sheet is obtained from the total weight of all the carbon sheets present in the carbon container and the total weight of all the raw material silicon carbide powder.

[0033] When the above weight ratio exceeds 5.0, the proportion of the carbon sheet with respect to the raw material silicon carbide powder is insufficient, and there may be a case where the carbon sheet cannot adsorb all the impurities contained in the raw material silicon carbide powder. Further, even if the above weight ratio is less than 1.0, the increase in the proportion of the carbon sheet does not contribute to the purification of the silicon carbide powder, so the above weight ratio is preferably 1.0 or more.

[0034] In the first heating step, heating is carried out in an inert atmosphere at 1800 to 2200 °C. The heating time can be, for example, 1 to 5 hours as the holding time at the maximum temperature. As the inert atmosphere, an atmosphere such as nitrogen or argon can be used. It is preferable that the oxygen concentration is less than 20 ppm so that combustion of the carbon sheet and oxidation of silicon carbide do not occur.

[0035] In the first heating step, impurities contained in the raw silicon carbide powder are adsorbed onto the carbon sheet. Specific examples of the impurities include silicon oxides (SiOx, particularly SiO2), metal oxides (Fe2O3, Al2O3, CaO, TiO2, Cr2O3, MnO, NiO, V2O5, ZrO2, etc.), sulfur oxides (SO3), phosphorus oxides (P2O5), and the like. Substances with lower boiling points and higher vaporization tendencies can be more efficiently adsorbed onto the carbon sheet.

[0036] Carbon derived from the carbon sheet adheres to the intermediate silicon carbide powder obtained in the first heating step. The purity of the intermediate silicon carbide powder is affected by the decrease in impurities removed from the silicon carbide powder and adhered to the carbon sheet and the increase in carbon adhered from the carbon sheet, so it may be higher or lower than that of the raw silicon carbide powder. The purity of the intermediate silicon carbide powder is, for example, about 94.0 to 98.0% by weight. Also, the carbon concentration in the intermediate silicon carbide powder is, for example, about 1.0 to 5.0% by weight.

[0037] Subsequently, a second heating step is carried out. In the second heating step, the intermediate silicon carbide powder is heated in an oxidizing atmosphere at 500 to 700 °C to obtain a high-purity silicon carbide powder with a silicon carbide purity of 99.0% by weight or more.

[0038] In the second heating step, the carbon sheet and the intermediate silicon carbide powder are separated, and the intermediate silicon carbide powder is heated in an oxidizing atmosphere at 500 to 700 °C.

[0039] FIG. 2 is a cross-sectional view schematically showing an example of a form in which a second heating step is performed in a firing furnace. In the form shown in FIG. 2, the silicon carbide intermediate powder 30 is placed in the carbon container 100, the carbon container 100 is placed in the firing furnace 200, and the second heating step is performed with the atmosphere in the internal space 120 of the carbon container 100 being an oxidizing atmosphere of 500 to 700°C.

[0040] In the second heating step, the carbon adhering to the silicon carbide intermediate powder is burned and removed by heating in an oxidizing atmosphere of 500 to 700°C. The heating time can be, for example, 1 to 10 hours as the holding time at the maximum temperature. As the oxidizing atmosphere, an atmosphere such as air, a mixed gas containing oxygen, or oxygen can be used. Among these, an air atmosphere is preferable. In order to facilitate the oxidative combustion of carbon, the oxygen concentration is preferably 18 vol% or more.

[0041] In the first heating step, impurities such as silicon oxide and metal oxide contained in the raw material silicon carbide powder are removed. Therefore, by performing both the first heating step and the second heating step, the purity of the raw material silicon carbide powder can be increased, and a high-purity silicon carbide powder can be obtained.

[0042] The firing furnace and the carbon container used for performing the second heating step may be the same as or different from the firing furnace and the carbon container used for performing the first heating step.

[0043] Through the first heating step and the second heating step, in the method for producing a high-purity silicon carbide powder of the present invention, a high-purity silicon carbide powder having a silicon carbide purity of 99.0% by weight or more is obtained. Also, a higher-purity silicon carbide powder having a silicon carbide purity of 99.5% by weight or more may be obtained, or an even higher-purity silicon carbide powder having a silicon carbide purity of 99.9% by weight or more may be obtained.

[0044] (Other Embodiments) In the first heating step, the raw material silicon carbide powder may be brought into contact with the carbon sheet. In the form shown in FIG. 1, the upper and lower portions of the raw material silicon carbide powder are sandwiched by the carbon sheet, but the form of contact between the raw material silicon carbide powder and the carbon sheet is not limited to this form. A carbon sheet may be laid under the raw material silicon carbide powder and it is not necessary to place a carbon sheet on top of the raw material silicon carbide powder. Also, a carbon sheet may be placed on top of the raw material silicon carbide powder without laying a carbon sheet under the raw material silicon carbide powder.

[0045] Also, the carbon sheet and the raw material silicon carbide powder may be alternately laminated, and the first heating step may be performed with the raw material silicon carbide powder sandwiched by the carbon sheet.

[0046] FIG. 3 is a cross-sectional view schematically showing another example of a form in which the first heating step is performed in a firing furnace. In the form shown in FIG. 3, the first heating step is performed by alternately arranging the carbon sheet 20 and the raw material silicon carbide powder 10 in the carbon container 100 arranged in the firing furnace 200. The first carbon sheet 21a is placed on the bottom surface 110 of the carbon container 100, and the raw material silicon carbide powder 10a is arranged on the first carbon sheet 21a. Further, the second carbon sheet 22a is placed on the raw material silicon carbide powder 10a.

[0047] On the second carbon sheet 22a, a raw material silicon carbide powder 10b different from the raw material silicon carbide powder 10a is arranged. Since the second carbon sheet 22a exists below with respect to the raw material silicon carbide powder 10b, it can also be regarded as the first carbon sheet 21b. Further, the second carbon sheet 22b is placed on the raw material silicon carbide powder 10b.

[0048] On the second carbon sheet 22b, a raw silicon carbide powder 10c different from the raw silicon carbide powders 10a and 10b is arranged. Since the second carbon sheet 22b is present below the raw silicon carbide powder 10c, it can also be regarded as the first carbon sheet 21c. Further, a second carbon sheet 22c is placed on the raw silicon carbide powder 10c.

[0049] In the form shown in FIG. 3, the raw silicon carbide powders 10a, 10b, and 10c are all sandwiched between the first carbon sheet and the second carbon sheet. In this form, a large amount of raw silicon carbide powder can be processed at once, and since the carbon sheet is in sufficient contact with any of the raw silicon carbide powders, impurities can be sufficiently adsorbed onto the carbon sheet, which is preferable.

[0050] The following inventions are described in this specification.

[0051] The present disclosure (1) includes a step of preparing a raw silicon carbide powder having a silicon carbide purity of 90.0% by weight or more and less than 99.0% by weight, a first heating step of bringing the raw silicon carbide powder into contact with a carbon sheet and heating it in an inert atmosphere at 1800 to 2200 °C to obtain an intermediate silicon carbide powder, a second heating step of heating the intermediate silicon carbide powder in an oxidizing atmosphere at 500 to 700 °C to obtain a high-purity silicon carbide powder having a silicon carbide purity of 99.0% by weight or more, which is a method for producing a high-purity silicon carbide powder.

[0052] The present disclosure (2) is a method for producing a high-purity silicon carbide powder according to the present disclosure (1), wherein the weight ratio of the raw silicon carbide powder to the carbon sheet (raw silicon carbide powder / carbon sheet) is 1.0 to 5.0.

[0053] The present disclosure (3) includes preparing a first carbon sheet and a second carbon sheet as the carbon sheets, Stack the first carbon sheet, the raw material silicon carbide powder, and the second carbon sheet in this order, sandwich the raw material silicon carbide powder with the carbon sheets, and perform the first heating step. This is the method for producing high-purity silicon carbide powder described in the present disclosure (1) or (2).

[0054] [Examples] Hereinafter, examples that more specifically disclose the present invention are shown. Note that the present invention is not limited only to these examples.

[0055] (Example 1) Raw material silicon carbide powder was prepared. The composition of the raw material silicon carbide powder was as shown in Table 1. One carbon sheet (thickness 7 mm, weight 200 g) was placed in a carbon container. 400 g of raw material silicon carbide powder was placed on the carbon sheet, and one more carbon sheet of the same kind was placed on the raw material silicon carbide powder to sandwich the raw material silicon carbide powder with the carbon sheets. Since the total weight of the carbon sheets was 400 g and the weight of the raw material silicon carbide was 400 g, the weight ratio of the raw material silicon carbide powder to the carbon sheets (raw material silicon carbide powder / carbon sheets) was 1.0. Under these conditions, the carbon container was placed in a firing furnace, the inside of the firing furnace was purged with argon, and firing was performed at 2140 °C for 2.5 hours in an inert atmosphere to perform the first heating step and obtain intermediate silicon carbide powder.

[0056] The intermediate silicon carbide powder was separated from the carbon sheets, and the composition of the intermediate silicon carbide powder was measured. The composition of the intermediate silicon carbide powder was as shown in Table 1. Compared with the raw material silicon carbide powder, the proportion of free carbon in the intermediate silicon carbide powder was higher, but the proportions of other impurities such as free silicon oxide and Fe2O3 were lower.

[0057] The intermediate silicon carbide powder was placed in a carbon container, the carbon container was placed in a firing furnace, and firing was performed at 600 °C for 5 hours in an air atmosphere (oxidizing atmosphere) to perform the second heating step and obtain high-purity silicon carbide powder. The composition of the high-purity silicon carbide powder was measured. The composition of the high-purity silicon carbide powder was as shown in Table 1. Compared with the intermediate silicon carbide powder, the proportion of free carbon in the high-purity silicon carbide powder was lower, and the proportion of the silicon carbide powder became 99.4% by weight. The purity (99.4% by weight) of the high-purity silicon carbide powder was higher than the purity (98.2% by weight) of the raw material silicon carbide powder, and high-purity silicon carbide powder with a purity of 99.0% by weight or more could be obtained by a simple process.

[0058] (Example 2) One carbon sheet (thickness 3.5 mm, weight 100 g) with a different thickness from that in Example 1 was placed in a carbon container. 900 g of raw material silicon carbide powder was placed on the carbon sheet, one more carbon sheet of the same kind was placed on the raw material silicon carbide powder, and 900 g of raw material silicon carbide powder was further placed on that carbon sheet. Another carbon sheet of the same kind was placed on top of it. That is, it had a laminated structure of (carbon sheet / raw material silicon carbide powder / carbon sheet / raw material silicon carbide powder / carbon sheet). Since the total weight of the carbon sheets was 300 g and the total weight of the raw material silicon carbide was 1800 g, the weight ratio of the raw material silicon carbide powder to the carbon sheet (raw material silicon carbide powder / carbon sheet) was 6.0.

[0059] The first heating process and the second heating process were carried out in the same manner as in Example 1, except that the arrangement of the carbon sheet and the raw material silicon carbide powder in the first heating process was different from that in Example 1, and high-purity silicon carbide powder was obtained. The composition of the high-purity silicon carbide powder was measured. The composition of the high-purity silicon carbide powder was as shown in Table 2. The purity (99.2% by weight) of the high-purity silicon carbide powder was higher than the purity (98.2% by weight) of the raw material silicon carbide powder, and high-purity silicon carbide powder with a purity of 99.0% by weight or more could be obtained by a simple process. However, since the ratio of the raw material silicon carbide powder / carbon sheet was 6.0 and the proportion of the carbon sheet with respect to the raw material silicon carbide powder was insufficient, the purity of the high-purity silicon carbide powder was lower than that in Example 1.

[0060] (Comparative Example 1) The first heating step and the second heating step were carried out in the same manner as in Example 1 except that the heating temperature in the first heating step was changed to 1700 °C, and silicon carbide powder that had undergone the second heating step was obtained. The composition of the silicon carbide powder that had undergone the second heating step was measured. The composition of the silicon carbide powder that had undergone the second heating step was as shown in Table 2. Since the temperature in the first heating step was low, the proportion of impurities such as silicon oxide and metal oxide was high, and the purity of the silicon carbide powder could not be sufficiently increased.

[0061] (Comparative Example 2) The first heating step and the second heating step were carried out in the same manner as in Example 1 except that the heating temperature in the second heating step was changed to 400 °C, and silicon carbide powder that had undergone the second heating step was obtained. The composition of the silicon carbide powder that had undergone the second heating step was measured. The composition of the silicon carbide powder that had undergone the second heating step was as shown in Table 2. Since the temperature in the second heating step was low, the combustion of carbon was not sufficiently carried out, and due to the high proportion of carbon after the second heating step, the purity of the silicon carbide powder could not be sufficiently increased.

[0062] The total content of the elements and compounds contained in the silicon carbide powder shown in each table is not 100.00% by weight, but this is due to the rounding effect of the digits not shown in the table.

[0063] [Table 1]

[0064] [Table 2] [Explanation of Symbols]

[0065] 10, 10a, 10b, 10c raw silicon carbide powder 20 Carbon sheet 21, 21a, 21b, 21c First carbon sheet 22, 22a, 22b, 22c Second carbon sheet 30 Intermediate silicon carbide powder 100 Carbon container 110 Bottom surface of the carbon container 120 Internal space of the carbon container 130 Heater 150 Heat insulating material 200 Firing furnace

Claims

1. A step of preparing raw silicon carbide powder having a silicon carbide purity of 90.0% by weight or more and less than 99.0% by weight; A first heating step of bringing the raw silicon carbide powder into contact with a carbon sheet and heating it in an inert atmosphere at 1800 to 2200°C to obtain intermediate silicon carbide powder; A second heating step of heating the intermediate silicon carbide powder in an oxidizing atmosphere at 500 to 700°C to obtain high-purity silicon carbide powder having a silicon carbide purity of 99.0% by weight or more. A method for producing high-purity silicon carbide powder comprising performing the steps.

2. The method for producing high-purity silicon carbide powder according to claim 1, wherein the weight ratio of the raw silicon carbide powder to the carbon sheet (raw silicon carbide powder / carbon sheet) is 1.0 to 5.

0.

3. Prepare a first carbon sheet and a second carbon sheet as the carbon sheets, The method for producing high-purity silicon carbide powder according to claim 1 or 2, wherein the first carbon sheet, the raw silicon carbide powder, and the second carbon sheet are laminated in this order, and the raw silicon carbide powder is sandwiched between the carbon sheets to perform the first heating step.

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