Method for manufacturing silicon carbide raw material and method for manufacturing silicon carbide single crystal

Abstract

To provide a method for manufacturing a silicon carbide raw material capable of preventing a different polytype from mixing when growing a silicon carbide single crystal, and a method for manufacturing the silicon carbide single crystal.SOLUTION: A method for manufacturing a silicon carbide raw material comprises: a preparation step of preparing a carbon raw material having a liquidity index of 30 or more and 90 or less; a charging step of charging the carbon raw material and a silicon raw material into a crucible; and a synthetic step of synthesizing a silicon carbide raw material by heating and reacting the carbon raw material and the silicon raw material. A method for manufacturing a silicon carbide single crystal uses a sublimation method of re-depositing a sublimated silicon carbide raw material on a seed crystal; and the silicon carbide raw material manufactured by the method for manufacturing the silicon carbide raw material is used as the silicon carbide raw material.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing a silicon carbide raw material and a method for producing a silicon carbide single crystal. [Background technology]

[0002] Sublimation is a known method for obtaining a silicon carbide single crystal substrate (see, for example, JP 2002-520251 A). In a method for producing a silicon carbide single crystal by sublimation, a sublimated silicon carbide raw material is reprecipitated on a seed crystal to grow a silicon carbide single crystal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2002-520251 Summary of the Invention [Problem to be solved by the invention]

[0004] It is known that silicon carbide has many different polytypes in its crystal structure. A polytype is a type of polymorphism in which a substance with the same chemical composition exhibits different atomic arrangements, and refers to structures that have the same constitutional units but differ only in the arrangement order. Silicon carbide has many structures with different stacking orders, such as 3C-SiC, 4H-SiC, 6H-SiC, and 15R-SiC. Among these, 4H-SiC has high conductivity in the vertical direction (C-axis direction) and is attracting attention for use in power devices.

[0005] For example, when growing a silicon carbide single crystal on a 4H-SiC seed crystal to obtain a 4H-SiC single crystal substrate, different polytypes may be mixed in. When different polytypes are mixed in, stacking faults occur at the interface. These interface defects may cause threading screw dislocations (TSDs) in the crystal growth direction, degrading the crystal quality.

[0006] The present invention has been made in light of the above circumstances, and has an object to provide a method for producing silicon carbide raw material and a method for producing silicon carbide single crystals that can suppress the inclusion of different polytypes during the growth of silicon carbide single crystals. [Means for solving the problem]

[0007] As a result of extensive investigations into the mixing of different polytypes when growing silicon carbide single crystals, the inventors have found that it is important that the silicon carbide raw material used has a uniform in-plane composition, i.e., that the carbon raw material and the silicon raw material are mixed uniformly.

[0008] Therefore, the inventors of the present invention further studied the uniformity of silicon carbide raw materials and arrived at the following findings. First, silicon carbide raw materials are heated during production, and silicon in the raw materials melts at or above its melting point, so it is considered that the powder characteristics are unlikely to affect the uniformity of the silicon carbide raw materials. On the other hand, carbon does not melt, so its powder characteristics affect the uniformity of the silicon carbide raw materials. In particular, if partial deviation occurs when the powder of carbon raw material is poured into the crucible and filled, the carbon raw material and the silicon raw material do not mix uniformly even when reacted with the silicon raw material melted by subsequent heating, and some of the carbon raw material remains as carbon powder. For this reason, it is considered that there are parts with locally high carbon density in the silicon carbide raw material, and the Si / C ratio is different in this locally high carbon density part, so that the sublimation gas becomes non-uniform and different polytypes are generated.

[0009] Furthermore, the inventors have discovered that by controlling the fluidity of the carbon raw material when pouring it into the crucible, it is possible to prevent the carbon raw material from becoming partially biased within the crucible, and have completed the present invention.

[0010] That is, a method for producing a silicon carbide raw material according to one embodiment of the present invention includes a preparation step of preparing a carbon raw material having a fluidity index of 30 or more and 90 or less, a filling step of filling a crucible with the carbon raw material and the silicon raw material, and a synthesis step of synthesizing a silicon carbide raw material by a heating reaction of the carbon raw material and the silicon raw material.

[0011] In the method for producing a silicon carbide raw material, the carbon raw material whose fluidity index is controlled within a predetermined range is filled into the crucible, so that the occurrence of partial bias of the carbon raw material in the crucible can be suppressed. Therefore, the uniformity of the in-plane composition of the produced silicon carbide raw material is improved. Therefore, by using the silicon carbide raw material produced by the method for producing a silicon carbide raw material, the incorporation of different polytypes in the growth of a silicon carbide single crystal can be suppressed.

[0012] The carbon raw material may have an average particle size smaller than that of the silicon raw material. By making the average particle size of the carbon raw material smaller than that of the silicon raw material in this manner, it is possible to more reliably prevent the carbon raw material from being locally biased in the crucible.

[0013] The average particle size of the carbon raw material is preferably 20 μm or more and 1000 μm or less. By setting the average particle size of the carbon raw material within the above range, the flowability of the carbon raw material can be easily ensured.

[0014] The average particle size of the silicon raw material is preferably 1 mm or more and 10 mm or less. By setting the average particle size of the silicon raw material to 1 mm or more and 10 mm or less in this manner, the carbon raw material can easily enter between the silicon raw materials, and the carbon raw material and the silicon raw material can easily be mixed uniformly.

[0015] Another aspect of the present invention relates to a method for producing a silicon carbide single crystal by a sublimation method in which a sublimated silicon carbide raw material is reprecipitated on a seed crystal, and as the silicon carbide raw material, a silicon carbide raw material produced by the method for producing a silicon carbide raw material of the present invention is used.

[0016] The method for producing a silicon carbide single crystal uses silicon carbide raw material produced by the method for producing a silicon carbide raw material of the present invention, and therefore can easily prevent the incorporation of different polytypes during the growth of the silicon carbide single crystal.

[0017] The diameter of the seed crystal is preferably 150 mm or more. The method for producing a silicon carbide single crystal can be suitably used for producing a large-diameter silicon carbide single crystal since it can prevent the inclusion of different polytypes. Effect of the Invention

[0018] The method for producing a silicon carbide raw material of the present invention can produce a silicon carbide raw material that can suppress the inclusion of different polytypes in the growth of a silicon carbide single crystal. Also, the method for producing a silicon carbide single crystal of the present invention can suppress the inclusion of different polytypes in the growth of a silicon carbide single crystal. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a flow diagram showing a flow of a method for producing a silicon carbide raw material according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing a heat treatment apparatus used in the method for producing silicon carbide raw material of FIG. [Diagram 3] FIG. 3 is a flow diagram showing a flow of a method for producing a silicon carbide single crystal according to another embodiment of the present invention. [Figure 4] FIG. 4 is a schematic cross-sectional view showing a heat treatment apparatus used in the method for producing a silicon carbide single crystal shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, a method for producing a silicon carbide raw material and a method for producing a silicon carbide single crystal according to one embodiment of the present invention will be described.

[0021] [Method of manufacturing silicon carbide raw material] A method for producing a silicon carbide raw material according to one embodiment of the present invention includes a preparation step S1, a filling step S2, and a synthesis step S3, as shown in Fig. 1. The method for producing a silicon carbide raw material is a method for producing a silicon carbide raw material 5 (see Fig. 4) from a carbon raw material 3 and a silicon raw material 4 using a heat treatment device including a crucible 1 and heating means 2 shown in Fig. 2, for example.

[0022] <Preparation process> In the preparation step S1, a carbon raw material 3 having a fluidity index of 30 or more and 90 or less is prepared.

[0023] The carbon raw material 3 is a powder composed of carbon particles. The carbon particles are preferably graphite or amorphous carbon.

[0024] The carbon raw material 3 may inevitably contain impurities. Although not all raw materials will be described individually below, impurities may inevitably be contained. Examples of the inevitable impurities include Ca, Fe, and Ti. It is preferable that these impurities are not contained, and specifically, the content of each is preferably 1 ppm or less by mass.

[0025] "Fluidity index" refers to Carr's fluidity index proposed by RL Carr. The fluidity index is an index that indicates the ease with which a powder flows, and can take values ​​from 0 to 100. The better the fluidity of a powder, the higher the fluidity index. Four powder physical properties are used to calculate the fluidity index: (a) compressibility, (b) angle of repose, (c) spatula angle, and (d) degree of aggregation (or uniformity). The fluidity index can be calculated by measuring each of the four powder physical properties, assigning the measurement results to an index of 0 to 25 based on Table 1, and then adding them up.

[0026] [Table 1]

[0027] In Table 1, "<*" (where * is a numerical value) indicates that it is smaller than *, and ">*" indicates that it is larger than *. Additionally, (a) compressibility, (b) angle of repose, (c) spatula angle, and (d) degree of aggregation (or degree of uniformity) are calculated as follows.

[0028] (a) Compression degree The degree of compression (%) is expressed as the loose bulk density in A (g / cm 3 ), and the compacted bulk density is B (g / cm 3) is calculated using the following formula 1. (B A) / B × 100 1 Here, the "loose bulk density" is the bulk density of the powder when it is allowed to fall naturally, and is the density calculated from the result of filling a powder sample into a cup of a specified capacity and weighing it. On the other hand, the packed bulk density is the bulk density of the powder when it is densely packed after the loose bulk density is measured and the air contained between the particles is removed by tapping the cup.

[0029] (b) Angle of repose The angle of repose (°) is the angle (elevation angle) between the horizontal plane and the slope of the cone (powder mountain) formed when powder is allowed to fall naturally. A powder mountain can be formed, for example, by the pouring method. In the pouring method, a powder sample is dropped through a funnel to form a powder mountain.

[0030] (c) Spatula angle The spatula angle (°) indicates the angle between the inclined plane formed when the accumulated powder is scooped up with a horizontal plate (spatula) and the horizontal plane. Specifically, the powder is first piled on a plate, and then the plate is gently raised vertically upwards, and the angle between the inclined plane of the cone remaining on the plate and the horizontal plane is measured. Next, a specified impact is applied, and the angle between the inclined plane of the cone and the horizontal plane is measured again. The average value of the angles before and after the impact is used as the spatula angle.

[0031] (d) Cohesion (or uniformity) The degree of agglomeration (%) is calculated using three sieves with different mesh sizes, based on the amount of powder remaining on each sieve and weighting each sieve accordingly. The degree of agglomeration increases with the mesh size of the upper, middle and lower sieves. The mesh size and vibration time of the sieve used to measure the degree of agglomeration are set based on the loose bulk density and packed bulk density, and the mesh size (smallest mesh size) of the lower sieve is set so that all particles can pass through.

[0032] If there is no cohesion, many particles pass through all sieves, and the degree of cohesion cannot be calculated accurately. In this case, uniformity is used. Uniformity is defined as the ratio of the sieve openings through which 10% of the powder passes to the sieve openings through which 60% of the powder passes.

[0033] The fluidity index can be measured, for example, by a "Powder Tester" manufactured by Hosokawa Micron Corporation. The "Powder Tester" can measure all four powder properties with a single device and calculate the fluidity index.

[0034] The lower limit of the fluidity index of the carbon raw material 3 is 30, more preferably 40, and even more preferably 50, as described above. On the other hand, the upper limit of the fluidity index of the carbon raw material 3 is 90, more preferably 80, and even more preferably 70. If the fluidity index of the carbon raw material 3 is less than the lower limit, the carbon raw material 3 is unlikely to enter between the silicon raw materials 4 in the filling step S2 described below, and there is a risk of partial bias of the carbon raw material 3 occurring in the crucible 1. On the other hand, if the fluidity index of the carbon raw material 3 exceeds the upper limit, there is a risk that the carbon raw material 3 slips through between the silicon raw materials 4 in the filling step S2 and segregates to the lower part of the crucible 1, and there is a risk of partial bias of the carbon raw material 3 occurring in the crucible 1. In contrast, by setting the fluidity index of the carbon raw material 3 within the above range, it is possible to prevent partial bias of the carbon raw material 3 occurring in the crucible 1 in the filling step S2.

[0035] The method for preparing the carbon raw material 3 having a fluidity index within the above range is not particularly limited. A carbon raw material 3 having a fluidity index within the above range may be selected, or the fluidity index can be adjusted by the crushing conditions when powdering the carbon raw material 3. Whether the prepared carbon raw material 3 has a desired fluidity index can be confirmed by using a fluidity index measuring device such as the above-mentioned "powder tester."

[0036] The average particle size of the carbon raw material 3 is preferably smaller than that of the silicon raw material 4 described below. By making the average particle size of the carbon raw material 3 smaller than that of the silicon raw material 4 in this way, it is possible to more reliably prevent the carbon raw material 3 from being partially biased in the crucible 1. Here, the "average particle size" refers to the 50% value (50% particle size, D50) of a cumulative volumetric particle size distribution curve measured by a laser diffraction / scattering method or the like. The cumulative particle size distribution curve can be measured, for example, using the MT3000II series manufactured by Microtrac.

[0037] The lower limit of the average particle size of the carbon raw material 3 is preferably 20 μm, more preferably 30 μm. On the other hand, the upper limit of the average particle size of the carbon raw material 3 is preferably 1000 μm, more preferably 200 μm. If the average particle size of the carbon raw material 3 is less than the above lower limit, the carbon raw material 3 may slip between the silicon raw materials 4 in the filling step S2 and segregate to the lower part of the crucible 1, which may cause a partial bias of the carbon raw material 3 in the crucible 1. On the other hand, if the average particle size of the carbon raw material 3 exceeds the above upper limit, the carbon raw material 3 may not easily enter between the silicon raw materials 4 in the filling step S2, which may cause a partial bias of the carbon raw material 3 in the crucible 1. On the other hand, by setting the average particle size of the carbon raw material 3 within the above range, it is possible to easily ensure an appropriate fluidity of the carbon raw material 3.

[0038] <Filling process> In the filling step S2, the carbon raw material 3 and the silicon raw material 4 are filled into the crucible 1.

[0039] The crucible 1 is a heating vessel and includes a raw material storage section 1a, a lid section 1b, and a seed crystal attachment section 1c. The shape of the raw material storage section 1a is not particularly limited as long as it can accommodate the carbon raw material 3 and the silicon raw material 4, and may be, for example, a cylindrical shape with a bottom. The lid section 1b seals the space inside the raw material storage section 1a and allows pressure or pressure to be applied. The seed crystal attachment section 1c is disposed on the upper part of the raw material storage section 1a, and a seed crystal 6 (see FIG. 4) can be attached thereto.

[0040] The silicon raw material 4 is a powder composed of silicon particles. The silicon particles may be an organic silicon compound containing carbon in part in addition to pure silicon, or a mixture thereof.

[0041] The lower limit of the average particle size of the silicon raw material 4 is preferably 1 mm, more preferably 3 mm. On the other hand, the upper limit of the average particle size of the silicon raw material 4 is preferably 10 mm, more preferably 7 mm. If the average particle size of the silicon raw material 4 is less than the above lower limit, the carbon raw material 3 is unlikely to enter between the silicon raw materials 4, and there is a risk of partial bias of the carbon raw material 3 occurring in the crucible 1. On the other hand, if the average particle size of the silicon raw material 4 exceeds the above upper limit, the silicon raw material 4 melted in the synthesis step S3 described later is likely to become droplets, and there is a risk of not reacting sufficiently with the carbon raw material 3. On the other hand, by setting the average particle size of the silicon raw material 4 within the above range, the carbon raw material 3 is likely to enter between the silicon raw materials 4, and the carbon raw material 3 and the silicon raw material 4 are likely to be mixed uniformly.

[0042] The carbon raw material 3 and the silicon raw material 4 may be placed in the crucible 1 after the silicon raw material 4 is placed in the crucible 1. Alternatively, a cylindrical resin container may be prepared separately, and the silicon raw material 4 may be placed in the container, followed by the carbon raw material 3, and the container may be rotated to mix uniformly before filling the raw material storage section 1a. In this manner, the carbon raw material 3 and the silicon raw material 4 can be mixed uniformly.

[0043] The carbon raw material 3 and the silicon raw material 4 are preferably mixed so that the mixture ratio of the number of carbon atoms to the number of silicon atoms is 1:1 or more and 1:1.2 or less. Since silicon atoms have a higher vapor pressure, some of the silicon may evaporate and be lost from the raw material storage section 1a. Taking this amount of loss into account, it is preferable to have a slightly higher amount of silicon atoms.

[0044] <Synthesis process> In the synthesis step S3, a silicon carbide raw material 5 is synthesized by a thermal reaction between a carbon raw material 3 and a silicon raw material 4. Here, the silicon carbide raw material 5 is a powder mainly composed of silicon carbide particles. Although it may contain some carbon particles and silicon particles, 90 mass % or more of the silicon carbide raw material 5 is silicon carbide particles. Note that the carbon particles and the silicon particles preferably have the same number of atoms, and more preferably remain uniformly within the silicon carbide raw material 5.

[0045] Heating can be performed by heating the crucible 1 with heating means 2. The heating means 2 is not particularly limited as long as it can heat the crucible 1, and can be, for example, a resistance heater, a high-frequency heater, etc. The heating temperature is measured and controlled, for example, by a radiation thermometer.

[0046] The lower limit of the heating temperature in the synthesis step S3 is preferably 1900°C, more preferably 2200°C. On the other hand, the upper limit of the heating temperature is preferably 2500°C, more preferably 2300°C. If the heating temperature is below the lower limit, the reaction in which the molten silicon raw material 4 impregnates and reacts with the carbon raw material 3 to form the silicon carbide raw material 5 does not proceed sufficiently, and a uniform silicon carbide raw material 5 may not be synthesized. On the other hand, if the heating temperature exceeds the upper limit, the vapor pressure of the silicon raw material 4 becomes too high, and the silicon raw material 4 is lost outside the crucible 1 before impregnating the carbon raw material 3, which may reduce the yield of the silicon carbide raw material 5. In addition, the cost required to ensure the heat resistance of the crucible 1 may be too high compared to the effect of heating.

[0047] Moreover, in order to suppress sublimation of the silicon carbide raw material 5, the synthesis step S3 is performed in a high pressure atmosphere. The lower limit of the pressure is preferably 30 kPa, and more preferably 60 kPa. The upper limit of the pressure can be set to atmospheric pressure or higher, but atmospheric pressure (101.3 kPa) is preferable since a pressurized vessel is not required, and a reduced pressure atmosphere of 80 kPa is more preferable since heat loss due to convection can be reduced. Note that the atmosphere is preferably an inert gas atmosphere such as argon in order to suppress reaction with the raw material.

[0048] <Advantages> In this method for producing a silicon carbide raw material, the crucible 1 is filled with the carbon raw material 3 whose fluidity index is controlled within a predetermined range, so that it is possible to prevent the carbon raw material 3 from being locally biased in the crucible 1. This improves the uniformity of the in-plane composition of the produced silicon carbide raw material 5. Therefore, by using the silicon carbide raw material 5 produced by this method for producing a silicon carbide raw material, it is possible to prevent the incorporation of different polytypes in the growth of a silicon carbide single crystal.

[0049] [Method for producing silicon carbide single crystal] The method for producing a silicon carbide single crystal according to another embodiment of the present invention shown in Fig. 3 is a method for producing a silicon carbide single crystal by a sublimation method in which a sublimated silicon carbide raw material 5 is reprecipitated on a seed crystal 6 as shown in Fig. 4, and includes a setting step S11 and a growing step S12. In the method for producing a silicon carbide single crystal, a silicon carbide raw material 5 produced by the method for producing a silicon carbide raw material of the present invention is used as the silicon carbide raw material.

[0050] <Installation process> In the setting step S11, a seed crystal 6 is set in the crucible 1.

[0051] The setting step S11 may be performed on the crucible 1 in which the silicon carbide raw material 5 has been charged, or may be performed simultaneously with the filling step S2 in the above-mentioned method for producing a silicon carbide raw material. By setting the seed crystal 6 simultaneously with the filling step S2, the growth step S12 can be performed without lowering the temperature after the synthesis of the silicon carbide raw material 5 (synthesis step S3), thereby improving the energy efficiency in producing the silicon carbide single crystal.

[0052] The seed crystal 6 is, for example, a silicon carbide single crystal substrate made of 4H-SiC. In the growth step S12, a single crystal of a selected polytype is grown on the seed crystal 6.

[0053] The lower limit of the diameter of the seed crystal 6 is preferably 100 mm, more preferably 150 mm, and further preferably 200 mm. The larger the diameter of the seed crystal 6, the larger the diameter of the silicon carbide single crystal that can be grown in the growth step S12. On the other hand, the larger the diameter of the seed crystal 6, the more likely it is that different polytypes will be mixed in. However, in the method for producing a silicon carbide single crystal, the silicon carbide raw material 5 produced by the method for producing a silicon carbide raw material of the present invention is used to prevent the mixing of different polytypes. The upper limit of the diameter of the seed crystal 6 is not particularly limited, but is, for example, 300 mm.

[0054] <Growth process> In the growth step S12, a silicon carbide single crystal is grown. Specifically, a silicon carbide raw material 5 is sublimated, and the sublimated silicon carbide raw material 5 is reprecipitated on a seed crystal 6, thereby growing the silicon carbide single crystal.

[0055] This growth step S12 is performed by heating in a reduced pressure atmosphere of 3 kPa or less. The heating temperature of the atmosphere is preferably 2200° C. or more and 2500° C. or less. When the synthesis step S3 and the growth step S12 are performed successively, the manufacturing efficiency can be improved by setting the heating temperature of this atmosphere and the heating temperature in the synthesis step S3 to the same temperature.

[0056] The temperature of the seed crystal 6 may be adjusted to, for example, not less than 2000° C. and not more than 2300° C. By setting the temperature of the seed crystal 6 lower than the heating temperature of the atmosphere in this manner, the silicon carbide raw material 5 can be easily reprecipitated on the seed crystal 6.

[0057] The method for producing a silicon carbide single crystal uses silicon carbide raw material 5 produced by the method for producing a silicon carbide raw material of the present invention, and therefore can easily prevent the incorporation of different polytypes during the growth of the silicon carbide single crystal.

[0058] [Other embodiments] The above-mentioned embodiment does not limit the configuration of the present invention. Therefore, the above-mentioned embodiment may omit, replace or add components of each part of the above-mentioned embodiment based on the description in this specification and common general technical knowledge, and it should be understood that all of these are within the scope of the present invention.

[0059] In the above embodiment, the crucible is described as having a raw material storage section, a lid section, and a seed crystal mounting section, but the crucible is not limited to this configuration. For example, when the production of silicon carbide single crystals is not performed consecutively to the production of silicon carbide raw material, a crucible that does not have a seed crystal mounting section may be used. EXAMPLES

[0060] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0061] [No.1] A carbon raw material with a fluidity index of 51.5 was prepared. The average particle size of this carbon raw material was 100 μm. The carbon raw material and the silicon raw material (average particle size: 2 mm) were filled into a crucible. In addition, a seed crystal of 4H-SiC with a diameter of 150 mm was placed in the crucible.

[0062] Next, the carbon raw material and the silicon raw material were subjected to a thermal reaction to synthesize a silicon carbide raw material under the synthesis conditions of a temperature of 2350° C. and a pressure of 70 kPa.

[0063] Subsequently, while maintaining the above temperature, the pressure was reduced to 0.3 kPa, and silicon carbide single crystal No. 1 was grown by sublimation.

[0064] [No.2] Silicon carbide single crystal No. 2 was grown in the same manner as No. 1, except that a carbon raw material with a fluidity index of 26.0 was prepared.

[0065] [evaluation] Photoluminescence images were observed for the silicon carbide single crystals No. 1 and No. 2 above using ultraviolet light with an excitation light of 365 nm. In these photoluminescence images, the 4H-SiC single crystal appears green, and the 6H-SiC single crystal appears reddish brown. In each image, the area ratio of 6H-SiC was 2.8% for No. 1 and 41.3% for No. 2.

[0066] From the above results, it is apparent that No. 1, which uses a carbon raw material with a fluidity index of 30 or more and 90 or less, is able to suppress the incorporation of different polytypes during the growth of silicon carbide single crystals. [Industrial Applicability]

[0067] As described above, the method for producing a silicon carbide raw material of the present invention can produce a silicon carbide raw material that can suppress the inclusion of different polytypes in the growth of a silicon carbide single crystal. Also, the method for producing a silicon carbide single crystal of the present invention can suppress the inclusion of different polytypes in the growth of a silicon carbide single crystal. [Explanation of symbols]

[0068] 1 crucible 1a Raw material storage section 1b Lid 1c Seed crystal attachment part 2 Heating means 3 Carbon raw materials 4. Silicon raw materials 5 Silicon carbide raw material 6 seed crystals

Claims

1. A preparation step of preparing a carbon raw material having a fluidity index of 30 or more and 90 or less; a step of filling the carbon raw material and the silicon raw material into a crucible; a synthesis step of synthesizing a silicon carbide raw material by a thermal reaction between the carbon raw material and the silicon raw material; The method for producing a silicon carbide raw material comprises:

2. 2. The method for producing silicon carbide raw material according to claim 1, wherein the average particle size of said carbon raw material is smaller than the average particle size of said silicon raw material.

3. 3. The method for producing a silicon carbide raw material according to claim 1, wherein the carbon raw material has an average particle size of 20 μm or more and 1000 μm or less.

4. 4. The method for producing silicon carbide raw material according to claim 3, wherein the silicon raw material has an average particle size of 1 mm or more and 10 mm or less.

5. A method for producing a silicon carbide single crystal by a sublimation method in which a sublimated silicon carbide raw material is reprecipitated on a seed crystal, comprising:

3. A method for producing a silicon carbide single crystal, comprising the step of: producing a silicon carbide raw material by the method for producing a silicon carbide raw material according to claim 1 or 2 as the silicon carbide raw material.

6. 6. The method for producing a silicon carbide single crystal according to claim 5, wherein the seed crystal has a diameter of 150 mm or more.

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