JP2018070408A - Silicon carbide powder and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silicon carbide powder capable of preventing the purity of a product consisting of a silicon carbide single crystal from deteriorating, and a method for manufacturing the same.SOLUTION: The silicon carbide powder includes (1) the silicon carbide powder containing 0.1-10 ppm of chlorine in a weight ratio. The method for manufacturing the silicon carbide powder comprises (2) the step S1 of immersing the silicon carbide powder in a solution including chloride ions; the step S3 of measuring the conductivity of the solution having the immersed silicon carbide powder to determine whether or not the conductivity is equal to or less than a predetermined conductivity; the step S4 of separating the immersed silicon carbide powder from the solution to immerse the silicon carbide powder in water, when it is determined that the conductivity of the solution is not equal to or less than the predetermined conductivity in the determining step S3; and the dry step S5 of separating the immersed silicon carbide powder from the solution to dry the silicon carbide powder, when the determining step S3 again is performed and it is determined that the conductivity of the solution is equal to or less than the predetermined conductivity.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a silicon carbide powder and a method for producing the same, and more particularly to a silicon carbide powder used for producing a silicon carbide single crystal and a method for producing the same.

  Silicon carbide powder is used as a material for molding wheels, ceramic parts and the like because of its high hardness, high thermal conductivity, and high temperature heat resistance. As disclosed in Patent Document 1 and Patent Document 2, a silicon carbide ceramic product is made by adding a binder to a powder to form granules, which are then molded into a predetermined shape, placed in a graphite crucible, and at least 2000 ° C. It can be obtained by baking and processing. Silicon carbide ceramic products can be obtained by filling a graphite crucible with silicon carbide powder and firing (hot press firing) while pressing.

  Silicon carbide is attracting attention as a material for a power semiconductor substrate that replaces silicon because it has a physical property of about three times the band gap and about ten times the dielectric breakdown electric field strength compared to silicon. This silicon carbide substrate. Manufactured by cutting from a silicon carbide single crystal ingot.

  As a method for producing a silicon carbide single crystal, a sublimation recrystallization method in which silicon carbide powder as a raw material is sublimated under a high temperature condition of 2000 ° C. or higher to grow a single crystal of silicon carbide is well known and widely used industrially. Has been.

JP-A-9-278524 JP-A-57-166365

  A silicon carbide single crystal ingot used as a material for a power semiconductor substrate is desired to have a low content of metal elements such as aluminum and titanium as dopants.

  However, when a silicon carbide single crystal is grown using silicon carbide powder to produce an ingot, when the silicon carbide powder is heated to a high temperature of, for example, 2000 ° C. or higher, the transition metal as an impurity in the silicon carbide powder is sublimated. To do. The sublimated transition metal stays in the furnace and adheres to and mixes with the growing silicon carbide single crystal, resulting in a problem that the purity of the manufactured silicon carbide single crystal ingot is lowered.

  Further, since the sublimated transition metal adheres to the growth apparatus and the growth apparatus is contaminated, the transition metal is subsequently mixed into the silicon carbide single crystal that is put into the growth apparatus and processed and produced, and the purity is high. There was a problem of going down.

  The present invention has been made in view of the above points, and in the production of a product composed of a silicon carbide single crystal by growing a silicon carbide single crystal, contamination of the growth apparatus due to impurities is prevented, and It is an object of the present invention to provide a silicon carbide powder capable of preventing a decrease in purity of a product made of the generated silicon carbide single crystal due to mixing, and a method for generating the same.

  The silicon carbide powder of the present invention is characterized by containing chlorine in a weight ratio of 0.1 ppm to 10 ppm.

  The method for producing silicon carbide powder of the present invention includes a solution dipping step of dipping silicon carbide powder in a solution containing chloride ions, and measuring the conductivity of the solution in which the silicon carbide powder is dipped. A determination step for determining whether or not the conductivity is equal to or lower than a predetermined conductivity, and when the determination step determines that the conductivity of the solution is not equal to or lower than the predetermined conductivity, the immersed carbonized carbon The silicon powder and the solution are separated, a water immersion step of immersing the silicon carbide powder in water is performed, and then the determination step is performed again. In the determination step, the conductivity of the solution is equal to or lower than a predetermined conductivity. If it is determined, the drying step of separating the soaked silicon carbide powder and the solution and drying the silicon carbide powder is performed.

It is a flowchart of an example of a silicon carbide powder production | generation process. It is sectional drawing of the experimental apparatus used for a silicon carbide single crystal growth experiment.

  Hereinafter, a method for producing a silicon carbide powder according to an embodiment of the present invention and a growth of a silicon carbide (SiC) single crystal using the produced silicon carbide (SiC) powder will be described. In the following description, the unit ppm is described as a weight ratio, that is, ppmw.

  The silicon carbide powder is prepared, for example, by mixing an inorganic siliceous raw material containing silicon and a carbonaceous raw material containing carbon to prepare a raw material for producing silicon carbide, and this raw material for producing silicon carbide is an Atchison furnace at a temperature of 2500 ° C. or more. It is obtained by pulverizing a lump made of silicon carbide obtained by firing using the above.

  Examples of the inorganic siliceous material include crystalline silica such as silica or amorphous silica such as silica fume and silica gel. The average particle size of the inorganic siliceous material is appropriately determined depending on the environment during firing, the state of the material (whether crystalline or amorphous), and the reactivity with the carbonaceous material.

  Examples of the carbonaceous raw material include crystalline carbon such as natural graphite and artificial graphite, or amorphous carbon such as carbon black, coke and activated carbon. These may be used alone or in combination of two or more. The average particle diameter of the carbon raw material is appropriately determined depending on the environment during firing, the state of the raw material (whether crystalline or amorphous), and the reactivity with the inorganic siliceous raw material.

  As a method of mixing the inorganic siliceous raw material and the carbonaceous raw material, any mixing method of wet mixing and dry mixing can be employed. The mixing ratio of the inorganic siliceous raw material and the carbonaceous raw material at the time of mixing is optimum in consideration of the environment when firing the silicon carbide production raw material, the particle size and reactivity of the silicon carbide production raw material. Choose one. The term “optimum” as used herein means maximizing the yield of silicon carbide obtained by calcination and minimizing the remaining amount of unreacted inorganic siliceous material or carbonaceous material.

  The silicon carbide powder is not limited to those manufactured by the above-described manufacturing method, and may be manufactured using, for example, a liquid phase reaction instead of a solid phase reaction. The average particle size of the silicon carbide powder obtained by pulverizing the lump of silicon carbide is preferably 10 μm or more and 2000 μm or less, and more preferably 45 μm or more and 1000 μm or less.

  The ground silicon carbide powder includes transition metals such as titanium (Ti), vanadium (V), chromium (Cr), nickel (Ni), manganese (Mn), iron (Fe), zinc (Zn) as impurities. It is included.

The silicon carbide powder of the present invention is produced by adding chlorine (Cl) to the silicon carbide powder before production. Specifically, after classifying the silicon carbide powder before production into a desired particle size, the silicon carbide powder before production is made to contain Cl by being immersed in a solution containing Cl ions. As a solution containing Cl ions to be used, HCl is preferable. In addition, when the content of the alkali metal or the Group 2 element in the finished product is unquestioned, other solutions containing chloride ions such as NaCl solution or CaCl ₂ solution may be used.

FIG. 1 shows a flow chart of an example of a SiC powder generation process in which chlorine (Cl) is contained in silicon carbide (SiC) powder and the amount of chlorine (Cl) in the silicon carbide powder is adjusted. First, a container containing a solution containing Cl ⁻ ions such as an HCl solution is prepared, and SiC powder is immersed in the solution (step S1).

When HCl is used as the solution, the HCl solution preferably has a Cl ⁻ concentration of 1 N or more in the solution. When a solution of 1N or more is used, it is possible to improve the purity of the SiC powder by dissolving metal impurities mixed in the SiC powder during pulverization and classification.

  Next, the solution is stirred (step S2). This stirring may be performed using a stirring blade. Moreover, you may carry out by circulating a solution with a pump.

Next, the conductivity of the solution is measured, and it is determined whether or not the measured conductivity is equal to or less than a predetermined value (step S3). The conductivity of the solution correlates with the amount of ions in the solution, here the amount of Cl ⁻ . The predetermined conductivity is calculated backward from the amount of Cl to be retained by the SiC powder after the solution is separated and dried. In other words, based on the amount of Cl to be retained in the dried SiC powder, the amount of Cl ⁻ ions in the solution is obtained, and the conductivity of the solution in the amount of ions is derived as the predetermined conductivity.

  This predetermined conductivity is determined by measuring the amount of Cl in the SiC powder dried after being immersed in a solution having several conductivity values in advance and separated from the solution by a predetermined method. For example, a calibration curve may be created based on the measured value, and the conductivity of the solution when the amount of Cl in the dried SiC powder becomes a predetermined value may be obtained. The amount of Cl in the dried SiC powder may be obtained, for example, by measuring the SiC powder by glow discharge mass spectrometry (GD-MS).

  Therefore, by determining whether the conductivity is equal to or lower than a predetermined value, it is determined whether the inside of the solution has a predetermined Cl concentration, and the amount of Cl retained by the SiC powder after separating and drying the solution is a predetermined amount. It can be determined whether or not. For this conductivity measurement, for example, a conductivity meter (electric conductivity meter) manufactured by HORIBA, Ltd .: D-70 / ES-70 series, H1 series, or the like can be used.

  In step S3, when the electrical conductivity is not lower than the predetermined value, the SiC powder and the solution are separated, and the SiC powder is immersed in water (step S4). Since this step is performed to dilute the solution retained by the SiC powder, the water in which the SiC powder is immersed is preferably water having low electrical conductivity, that is, high purity water with less impurities. Therefore, the water used in step S3 is preferably ion-exchanged water or distilled water with high purity.

  In step S3, when the electrical conductivity is equal to or lower than a predetermined value, the SiC powder is separated from the solution and dried (step S5). The fact that the conductivity has become equal to or lower than a predetermined value in step S3 means that the amount of Cl contained in the SiC powder becomes a predetermined value when dried. After drying in step S5, the SiC powder of the present invention is completed.

  In steps S4 and S5, the SiC powder and the solution are separated so that the solution remains in the SiC powder after the separation. For example, the SiC powder and the solution may be separated by decantation, filter press, filtration, or the like. In step S5, Cl is left on the surface of the SiC powder by drying with the solution remaining in the SiC powder. That is, Cl is held in the SiC powder particles by physical adsorption.

  In the drying in step S5, only the water content of the solution adhering to the SiC powder is blown away, and the Cl contained in the solution is left in the SiC powder. It is preferable to use it.

  In addition, the method of moving and drying SiC powder, such as shaking SiC powder, is not preferable. Since SiC has a very high hardness, moving the SiC powder scrapes the device in contact with the SiC powder or the container in the container during the drying process, and impurities derived from the member are mixed into the SiC powder. Because it will end up.

  The predetermined value varies depending on the water retention amount of the SiC powder when the SiC powder and the solution are separated. For example, the water retention amount varies depending on the particle size of the SiC powder. Specifically, when the particle size of the SiC powder is coarse, the water retention amount is small, and when it is fine, the water retention amount is large. In addition, the water retention amount varies depending on the method of separating the SiC powder and the solution. Specifically, the amount of retained water of the SiC powder increases when separating by decantation, and the amount of retained water decreases when separated by a filter press.

  As described above, by producing SiC powder, it is possible to produce SiC powder containing a desired amount of Cl and having few impurities such as transition metals by a simple method.

  Hereinafter, a method of growing a SiC single crystal using the SiC powder formed as described above will be described. First, after generating SiC powder containing chlorine (Cl) as described above, the SiC powder is placed in a container in which a seed crystal for SiC single crystal growth is attached, and is heated in a heating atmosphere of a heating device. It is arranged and heated. As this heating device, for example, a heating furnace such as an electric furnace may be used. The heating furnace includes a discharge mechanism for discharging the gas in the heating atmosphere of the heating furnace out of the system. The discharge mechanism is, for example, a discharge pump. Moreover, as a container, a graphite crucible is used, for example.

  In this heating step, the mixture in the container is heated to 2100 ° C. This heating is continued for several hours to several tens of hours. In this heating process, it is preferable that the atmospheric gas is always discharged. The atmosphere gas may be discharged by the discharge mechanism from the time when the gas starts to be generated in the atmosphere due to the reaction of the mixture in the heating process, for example, from the time when the temperature of the mixture in the container exceeds 500 ° C.

  This discharge reduces the atmosphere in the heating furnace. In consideration of the discharge of gas generated in the atmosphere due to the reaction of the mixture in the heating process, the discharge mechanism may be controlled so that the pressure of the atmospheric gas is within a predetermined range, but such control is not performed. May be.

  Furthermore, you may supply nitrogen gas, argon gas, air, etc. from the system outside in the atmosphere of a heating apparatus. However, the supply gas is limited to those that do not adversely affect the quality of SiC products such as SiC single crystal ingots to be manufactured.

  Most of the transition metal, which is an impurity contained in the SiC powder before single crystal growth, evaporates when the SiC powder is heated to 2000 ° C. or higher in the heating process. Most of the evaporated transition metal rides on the atmospheric gas discharge flow and is discharged out of the heating furnace. However, part of the evaporated transition metal remains in the furnace and is mixed into the growing SiC single crystal. Moreover, the transition metal remaining in the furnace adheres to the graphite part when it reaches the graphite part including a surrounding container such as a graphite crucible.

  As described above, the SiC powder of the present invention contains chlorine. This chlorine scatters in the furnace at a temperature of 2000 ° C. or lower in the heating process. The scattered chlorine reacts with the transition metal remaining in the furnace and the transition metal adhering to the above-described graphite component to form chloride.

  Due to the high temperature inside the furnace, the chloride vaporizes and rides on the discharge flow of the atmospheric gas and is discharged out of the heating furnace. This makes it possible to remove the transition metal evaporated from the SiC powder and remaining in the furnace and the transition metal adhering to the graphite component.

For example, titanium (Ti) will be described as an example. As described above, when titanium is heated to 2000 ° C. or higher, it is evaporated and released into the furnace atmosphere, and a part of the titanium adheres to the graphite part. Titanium remaining in the furnace and titanium adhering to the graphite parts and Cl scattered from the SiC powder into the furnace are obtained by the reaction shown in the following formula (1) and titanium chloride (IV) (TiCl ₄ ) Become.
Ti + 2Cl ₂ → TiCl ₄ (1)

  Titanium chloride (IV) is vaporized (gasified) at a very low temperature (136.4 ° C.), and thus is immediately gasified in a furnace at 2000 ° C. or higher. The titanium chloride gas, which is the gasified titanium chloride, is discharged out of the heating furnace on the discharge flow of the atmospheric gas. Similarly, transition metals remaining in the furnace and other transition metals adhering to the graphite parts are also gasified by being combined with chlorine, and are discharged out of the heating furnace along with the discharge flow of the atmospheric gas.

  As described above, the transition metal remaining in the furnace is gasified by combining with the chlorine scattered from the SiC powder, and is grown by being discharged out of the heating furnace on the discharge flow of the atmospheric gas. Impurities are prevented from being mixed into the SiC single crystal.

  In addition, the transition metal attached to the graphite part during the heat treatment is combined with chlorine scattered from the SiC powder and gasified, and is discharged out of the heating furnace on the discharge flow of the atmospheric gas. The graphite component is prevented from being contaminated by the transition metal. Thereby, it is possible to prevent impurities from being mixed into the SiC single crystal generated by the heat treatment of the next lot after the heat treatment of the first lot is completed.

  In addition, the chlorine contained in the SiC powder as a raw material is contained in the graphite component when the content of transition metals (Ti, V, Cr, Ni, Mn, Fe, Zn) as impurities of the SiC powder is 100 ppm or less. From the viewpoint of sufficiently removing the attached transition metal, it is preferably 0.1 ppm or more. Further, it is preferably 10 ppm or less, and more preferably 2 ppm or less, from the viewpoint of preventing corrosion of exhaust systems such as piping and pumps of exhaust systems due to chlorine having high reactivity and high temperature.

  Hereinafter, the production | generation of the SiC powder of the Example of this invention and the experiment which grows a SiC single crystal using this are demonstrated. In the following examples, seven types of SiC powders were produced in which the Cl content in the SiC powder was 0.05 ppm, 0.1 ppm, 0.2 ppm, 1 ppm, 2 ppm, 10 ppm, and 20 ppm.

[Production of SiC powder]
First, SiC powder was produced by the Atchison method. Specifically, first, amorphous synthetic silica powder and carbon black were mixed at a theoretical reaction amount ratio. In the case of the present Example, it mixed so that it might become amorphous synthetic silica: carbon black = 2: 1.

  A reagent manufactured by Taiheiyo Cement Co., Ltd. was used as the amorphous synthetic silica powder. This amorphous synthetic silica powder has 1.0 ppm of boron (B), 1.0 ppm of phosphorus (P), 0.5 ppm of aluminum (Al), 1.0 ppm of iron (Fe), and titanium (Ti). Each contained 1.0 ppm. Moreover, the average particle diameter of this amorphous silica powder is 2 mm or less.

  As the carbon black, “Seast 600” manufactured by Tokai Carbon Co., Ltd. was used. This carbon powder contains 1.0 ppm of boron (B), 1.0 ppm of phosphorus (P), 43 ppm of aluminum (Al), 34 ppm of iron (Fe), and 2.3 ppm of titanium (Ti). It was. Moreover, the average granule diameter of this carbon black is 2 mm or less.

  Next, this mixture of amorphous synthetic silica powder and carbon black was filled in an Atchison furnace and baked at 2500 ° C. or higher for 24 hours. The obtained SiC ingot was pulverized with a jaw crusher and a ball mill pulverizer. By classifying the SiC powder obtained by pulverization, a SiC powder having a particle size of 45 to 2000 μm was produced.

  SiC powder for adjusting the amount of chlorine (Cl) in the SiC powder by adding chlorine (Cl) to the SiC powder described with reference to FIG. 1 so that the SiC powder produced by the above-mentioned Atchison method contains chlorine. A production process was performed.

  Specifically, first, in step S1, SiC powder was immersed in 2N hydrochloric acid for 3 hours. Thereafter, in step S2, the solution was stirred with a stirring blade. Thereafter, in step S3, the electrical conductivity of the solution was measured to determine whether the solution had a predetermined electrical conductivity or less. In this example, the predetermined conductivity was set so that the Cl content of the SiC powder after drying was the above value.

  In step S3, when the solution has a predetermined conductivity or higher, then in step S4, the SiC powder was separated from the solution and immersed in ion-exchanged water, and step S3 was performed again. In step S3, when the solution became equal to or lower than the predetermined conductivity, thereafter, in step S5, the SiC powder was separated from the solution and dried. This drying was performed by putting SiC powder in a drying vat and drying it.

  In this example, whether or not the amount of Cl contained in each SiC powder after drying was a predetermined amount was confirmed by performing GD-MS measurement. Moreover, the amount of Ti, V, Cr, Ni, Mn, Fe, and Zn contained in each SiC powder after drying was also confirmed by GD-MS measurement. As a result of the measurement, the total content of Ti, V, Cr, Ni, Mn, Fe, and Zn in each SiC was 5 ppm.

  As described above, seven types of SiC powders differing only in the Cl content were generated.

[SiC single crystal growth experiment]
Experiments were conducted to grow SiC single crystals using SiC powders containing different amounts of Cl produced as described above.

-Experimental equipment-
FIG. 2 shows a cross-sectional view of the experimental apparatus 10. The furnace body 11 is a furnace body of an electric furnace. A heat insulating material 13 is provided on the inner surface of the furnace body 11. The heater 15 is a graphite heater provided on the inner surface of the heat insulating material 13. The graphite crucible 17 is arranged in a space formed by the inner surface of the heat insulating material 13. The graphite crucible 17 has a container portion 17A and a lid portion 17B. The graphite crucible 17 had a total content of Ti, V, Cr, Ni, Mn, Fe, and Zn of less than 3 ppm before the experiment.

  The exhaust pipe 19 is a stainless steel pipe made of SUS304 provided to communicate the space inside the furnace body 11 and the space outside the furnace body 11. The exhaust pump 21 is disposed outside the furnace body 11 and connected to the exhaust pipe 19, and can exhaust the gas in the furnace body 11 through the exhaust pipe 19.

  The test piece 23 is made of SUS304, which is the same material as the exhaust pipe 19, and is a plate material having a length of 50 mm × a width of 50 mm and a thickness of 3 mm. The test piece 23 is disposed in the exhaust pipe 19 during the experiment. The surface of the test piece 23, that is, the surface defined by the length and width is the test surface 23S.

  The test piece 23 was placed in the exhaust pipe 19 for an experiment, and then taken out and measured for the surface roughness of the test surface 23S. From the change in surface roughness due to the corrosion of the test surface 23S, the exhaust pipe 19 It can be determined whether the inner surface of the steel is corroded. The test surface 23S has a surface roughness Ra <0.01 μm before the experiment.

-Experimental procedure-
In the experiment, first, 300 cc of SiC powder was placed in a graphite crucible 17. At this time, the internal volume of the graphite crucible was within 10 times the bulk (volume) of the SiC powder. A SiC single crystal plate (not shown) polished as a seed crystal was placed on the inner surface of the graphite crucible lid portion 17B. The test piece 23 was placed in the exhaust pipe 19. At this time, the test piece 23 was arranged so that a surface parallel to the fluid flow in the exhaust pipe 19 became the test surface 23S.

  Next, the graphite crucible 17 is placed in the furnace body 11, the pressure in the furnace is set to 1 kPa in an argon (Ar) atmosphere, the temperature of the bottom of the graphite crucible container portion 17A is 2,300 ° C., and the top of the graphite crucible. The lid was heated so that the temperature of the lid portion 17B was 2,100 ° C. In this experiment, the heating time was 48 hours. By this heating, the SiC powder in the graphite crucible 17 is sublimated to reach the seed crystal, and an SiC single crystal grows on the surface of the seed crystal. During the heating, the gas in the furnace body 11 was constantly discharged through the exhaust pipe 19 using the pump 21.

  The above-described experiment was performed for each SiC powder having a different Cl content, and the following evaluation was performed. In each experiment, the graphite crucible 17 and the test piece 23 were replaced with new ones.

-Experimental results and evaluation-
After the above-mentioned experiment, the amount of transition metal (Ti, V, Cr, Ni, Mn, Fe, Zn) adhering to the graphite crucible 17 after the experiment for the SiC powder of each Cl amount, and the exhaust pipe 19 after the test. Evaluation was performed by measuring the surface roughness Ra of the test surface 23S of the test piece 23 taken out of the test piece 23 and the amounts of Ti, V, Cr, Ni, Mn, Fe, and Zn contained in the generated SiC single crystal. .

  The amount of transition metal (Ti, V, Cr, Ni, Mn, Fe, Zn) remaining on the graphite crucible after the experiment is determined after the graphite crucible after the experiment is made into a solution by pressure acid decomposition. Measurement was performed by high frequency inductively coupled plasma (ICP) emission spectroscopic analysis.

  Further, the surface roughness of the test surface 23S after the experiment was measured by a surface roughness measuring instrument such as a stylus type surface roughness measuring machine.

  Further, the amounts of Ti, V, Cr, Ni, Mn, Fe, and Zn contained in the SiC single crystal produced after the experiment were measured by GD-MS measurement.

  The experimental results are shown below. In addition, as for a result, sample number No. No. 1-7 are shown.

As shown in the above table, the amount of transition metal remaining in the graphite crucible is No. No. 1 was 6 ppm, and the amount of Cl contained in the SiC powder was 0.1 ppm or more. 2-No. 7 was less than 3 ppm. As described above, the amount of transition metal contained in the graphite crucible before the experiment is 3 ppm or less.

  From this result, it was found that when the amount of Cl contained in the SiC powder is 0.1 ppm or more, there is no transition metal remaining on the graphite crucible after the heat treatment or negligibly small. Therefore, it was found that when the amount of Cl contained in the SiC powder is 0.1 ppm or more, the transition metal remaining in the graphite crucible with respect to the SiC single crystal to be grown can be prevented.

  Further, the surface roughness Ra of the test piece is No. 1 in which the amount of Cl contained in the SiC powder is 2 ppm or less. 1-No. No. 5 is less than 0.01 below the detection limit, and the Cl content is 10 ppm. No. 6 is 0.01 and the Cl content is 20 ppm or more. 7 was 0.03. As described above, the surface roughness Ra of the test surface before the experiment is less than 0.01.

  From this result, it was found that if the amount of Cl contained in the SiC powder is 10 ppm or less, particularly 2 ppm or less, the pipe does not corrode.

  The amount of transition metal in the SiC single crystal is No. 1 in which the amount of Cl in the SiC powder is 0.05. No. 1 was 3 ppm, and the Cl content was 0.1 or more. 2-No. 7 was less than 1 ppm.

  From this result, if the amount of Cl contained in the SiC powder is 0.1 ppm or more, is there any transition metal that is released from the SiC powder into the furnace body in the heat treatment and stays in the furnace body and remains mixed in the SiC single crystal? Or it turned out to be negligible. Therefore, if the amount of Cl contained in the SiC powder is 0.1 ppm or more, it is possible to prevent the transition metal from being mixed into the SiC single crystal during the growth of the SiC single crystal and to increase the purity of the SiC single crystal. I understood that.

  According to the above results, the contamination of the transition metal into the graphite crucible is prevented, the exhaust mechanism such as the exhaust pipe is not damaged, and the transition metal is prevented from being mixed into the produced silicon carbide single crystal, thereby preventing the silicon carbide single crystal from being mixed. It was found that the silicon carbide powder that can increase the purity of the crystal is a silicon carbide powder having a Cl content of 0.1 to 10 ppm, preferably 0.1 to 2 ppm, by weight.

  Further, in the above embodiment, carbonization containing chlorine by immersing a silicon carbide powder produced by mixing and firing an inorganic siliceous material and a carbonaceous material in a solution containing chloride ions. Silicon powder was produced. However, silicon carbide powder containing chlorine may be generated by other methods. For example, a silicon carbide powder containing chlorine may be generated by mixing an inorganic siliceous raw material or a carbonaceous raw material with a chloride such as sodium chloride or hydrochloric acid before baking.

DESCRIPTION OF SYMBOLS 10 Experimental apparatus 11 Furnace body 13 Heat insulating material 15 Heater 17 Graphite crucible 19 Exhaust pipe 21 Exhaust pump 23 Test piece

Claims (3)

  A silicon carbide powder comprising chlorine in a weight ratio of 0.1 ppm to 10 ppm.   The silicon carbide powder according to claim 1, wherein chlorine is contained in an amount of 2 ppm or less by weight. A solution immersion step of immersing the silicon carbide powder in a solution containing chloride ions;
Determining the electrical conductivity of the solution in which the silicon carbide powder is immersed to determine whether the electrical conductivity is equal to or lower than a predetermined electrical conductivity, and
In the determination step, when it is determined that the conductivity of the solution is not equal to or lower than a predetermined conductivity, the immersed silicon carbide powder and the solution are separated and the silicon carbide powder is immersed in water. Step, and then execute the determination step again,
When it is determined in the determination step that the conductivity of the solution is equal to or lower than a predetermined conductivity, the drying step of separating the immersed silicon carbide powder and the solution and drying the silicon carbide powder is executed. The manufacturing method of the silicon carbide powder characterized by the above-mentioned.