JP2016106070A - Manufacturing method of silicon carbide substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a silicon carbide substrate capable of obtaining a silicon carbide crystal having little dislocation by suppressing increase of dislocation on a seed substrate main surface.SOLUTION: A manufacturing method of a silicon carbide substrate has following steps. A part of a silicon carbide raw material 8 is sublimed. After the part of the silicon carbide raw material 8 is sublimed, a seed substrate 1 having a main surface 1A is arranged in a growth vessel 10. A silicon carbide crystal 11 is grown on the main surface 1A of the seed substrate 1 by subliming the residue of the silicon carbide raw material 8 in the growth vessel 10.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing a silicon carbide substrate, and more particularly to a method for manufacturing a silicon carbide substrate with few dislocations.

  In recent years, silicon carbide substrates have begun to be used for manufacturing semiconductor devices. Silicon carbide has a larger band gap than silicon. Therefore, a semiconductor device using a silicon carbide substrate has advantages such as high breakdown voltage, low on-resistance, and small deterioration in characteristics under a high temperature environment.

A silicon carbide single crystal can be produced by, for example, a sublimation recrystallization method. For example JP-A-2007-284306 (Patent Document 1), describes a process for the specific surface area of the raw material silicon carbide powder is below 0.001 m ² / g or more 0.05 m ² / g to produce a silicon carbide single crystal Has been. Japanese Patent Application Laid-Open No. 2009-234802 (Patent Document 2) discloses that a crucible is pretreated in a reduced pressure atmosphere at a temperature at which the silicon carbide raw material is not sublimated for a predetermined time and then carbonized in an inert gas atmosphere. A method for producing a silicon carbide single crystal by sublimating a silicon raw material is described.

JP 2007-284306 A JP 2009-234802 A

  However, in the case of producing a silicon carbide crystal by any of the above methods, an increase in dislocations on the seed substrate main surface cannot be sufficiently suppressed, and it has been difficult to obtain a silicon carbide substrate with few dislocations.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a method for manufacturing a silicon carbide substrate with less dislocations by suppressing an increase in dislocations on the seed substrate main surface. It is.

  As a result of intensive studies on the cause of an increase in dislocations on the main surface of the seed substrate when a silicon carbide single crystal is produced by the sublimation method, the present inventor obtained the following knowledge and arrived at the present invention. In order to grow a good silicon carbide single crystal by the sublimation method, control of the sublimation gas is important. The sublimation gas is generated by heating and sublimating silicon carbide powder as a raw material. The composition and vapor pressure of the sublimation gas do not ideally depend on the particle size of the silicon carbide raw material powder, but actually depend on the particle size. Therefore, it is important to optimize the particle size and specific surface area of the silicon carbide raw material powder. However, even if the particle size and specific surface area of the silicon carbide raw material powder are controlled, when the silicon carbide raw material powder is handled, a part of the silicon carbide raw material powder is crushed to generate a fine powder, or the silicon carbide raw material powder has a damaged layer. May occur. The presence of this fine powder and the presence of the damaged layer cause an increase in dislocations in the silicon carbide crystal at the initial stage of crystal growth.

  As a result of examining the method for removing the fine powder contained in the silicon carbide raw material powder, it is effective to sublimate and remove the fine powder or damaged layer before growing the silicon carbide crystal on the main surface of the seed substrate. I came up with something. A fine powder having a small particle size has a small curvature radius. For this reason, the surface energy is increased, so that it is easy to sublimate. Even if the powder has a large particle size, the damaged layer on the surface tends to sublime. Therefore, by sublimating a part of the silicon carbide raw material before placing the seed substrate in the growth vessel, the fine powder and the damaged layer that cause an increase in dislocation can be preferentially removed.

  Therefore, a method for manufacturing a silicon carbide substrate according to the present invention includes the following steps. Part of the silicon carbide raw material is sublimated. After a part of the silicon carbide raw material is sublimated, a seed substrate having a main surface is placed in the growth vessel. By sublimating the remainder of the silicon carbide raw material in the growth vessel, silicon carbide crystals grow on the main surface of the seed substrate.

  According to the method for manufacturing a silicon carbide substrate according to the present invention, after part of the silicon carbide raw material is sublimated, the remainder of the silicon carbide raw material is sublimated to grow a silicon carbide crystal on the main surface of the seed substrate. As a result, the silicon carbide crystal can be grown on the main surface of the seed substrate after the fine powder or the damaged layer causing the increase of dislocation is sublimated and removed preferentially in the initial stage of crystal growth. Further, since the seed substrate is disposed in the growth vessel after a part of the silicon carbide raw material has been sublimated, it is possible to prevent the seed substrate from being contaminated by the sublimated fine powder or the damaged layer. As a result, a silicon carbide substrate with few dislocations can be obtained.

  Preferably, in the above method for manufacturing a silicon carbide substrate, after the step of sublimating a part of the silicon carbide raw material, a step of growing a silicon carbide crystal without performing machining on the remainder of the silicon carbide raw material is performed. The Thereby, it can prevent that a fine powder and a damage layer generate | occur | produce in the remainder of a silicon carbide raw material.

In the above method for manufacturing a silicon carbide substrate, a value obtained by subtracting the second dislocation density immediately below the main surface from the first dislocation density immediately above the main surface of the seed substrate is 1 × 10 ³ cm ⁻² or less. Thereby, a silicon carbide substrate with few dislocations can be obtained effectively.

  Preferably, the method for manufacturing a silicon carbide substrate further includes a step of reducing silicon carbide fine powder contained in the silicon carbide raw material before sublimating a part of the silicon carbide raw material. Thereby, a silicon carbide substrate with few dislocations can be obtained more effectively.

  Preferably, in the method for manufacturing the silicon carbide substrate, the step of reducing the silicon carbide fine powder is performed by immersing the silicon carbide raw material in the liquid and removing the silicon carbide fine powder floating on the surface of the liquid. Thereby, the silicon carbide fine powder can be removed from the silicon carbide raw material by a simple method.

  ADVANTAGE OF THE INVENTION According to this invention, the increase in the dislocation in a seed substrate main surface can be suppressed, and a silicon carbide crystal with few dislocations can be obtained.

It is a flowchart which shows schematically the manufacturing method of the silicon carbide substrate which concerns on one embodiment of this invention. It is a cross-sectional schematic diagram which shows schematically the 1st process of the manufacturing method of the silicon carbide substrate which concerns on one embodiment of this invention. It is a cross-sectional schematic diagram which shows schematically the 2nd process of the manufacturing method of the silicon carbide substrate which concerns on one embodiment of this invention. It is a cross-sectional schematic diagram which shows schematically the 3rd process of the manufacturing method of the silicon carbide substrate which concerns on one embodiment of this invention. It is a cross-sectional schematic diagram which shows schematically one process of the manufacturing method of the silicon carbide substrate which concerns on one embodiment of this invention. It is a figure for demonstrating the method to measure the increase amount of the dislocation in the main surface of a seed substrate. It is a figure for demonstrating the method to measure the increase amount of the dislocation in the main surface of a seed substrate. It is a figure for demonstrating the method to measure the increase amount of the dislocation in the main surface of a seed substrate.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated. In the crystallographic description in this specification, the individual orientation is indicated by [], the collective orientation is indicated by <>, the individual plane is indicated by (), and the collective plane is indicated by {}. As for the negative index, “−” (bar) is attached on the number in crystallography, but in this specification, a negative sign is attached before the number. The angle is described using a system in which the omnidirectional angle is 360 degrees.

  With reference to FIG. 3, the structure of the apparatus for manufacturing the silicon carbide substrate which concerns on this Embodiment is demonstrated.

  Referring to FIG. 3, the silicon carbide substrate manufacturing apparatus according to the present embodiment mainly includes growth vessel 10 and heat insulating material 4. The growth vessel 10 is a crucible made of, for example, purified graphite, and has a seed substrate holding unit 3 and a raw material storage unit 7. Seed substrate holding unit 3 is for holding seed substrate 1 made of, for example, single crystal silicon carbide. Raw material container 7 is for placing silicon carbide raw material 8 made of, for example, polycrystalline silicon carbide.

  The heat insulating material 4 is made of felt, for example, and is for insulating the growth vessel 10 from the outside. The heat insulating material 4 is formed so as to surround the outer wall surface of the growth vessel 10, for example. A plurality of through holes 2 a and 2 b are formed in the heat insulating material 4. A part of the upper surface of the seed substrate holding part 3 is exposed in the through hole 2 a formed in the heat insulating material 4. Further, a part of the bottom surface of the raw material container 7 is exposed in the through-hole 2 b formed in the heat insulating material 4.

  A method for manufacturing a silicon carbide substrate according to the present embodiment will be described with reference to FIGS.

First, seed substrate 1 made of, for example, a silicon carbide single crystal is prepared. The polytype of the seed substrate 1 is 4H, for example. The diameter of the seed substrate 1 is, for example, 6 inches, and preferably 4 inches (100 mm) or more. The main surface 1A of the seed substrate 1 is, for example, a (0001) C surface that is off by about 4 °. The threading dislocation density in the main surface 1A of the seed substrate 1 is, for example, about 1000 cm ⁻² . Both surfaces of the seed substrate 1 are subjected to CMP (Chemical Mechanical Polishing) polishing. The warp of the seed substrate 1 is smaller than 10 μm, for example.

  In the present embodiment, main surface 1A of seed substrate 1 is etched in a silicon gas atmosphere. Specifically, an etching crucible made of graphite is installed in a heating furnace. After evacuating the heating furnace, the heating furnace is filled with, for example, about 70 kPa of argon (Ar). A seed substrate 1 is disposed in the upper part of the etching crucible. Silicon is arranged in the crucible, and silicon carbide raw material powder is not arranged. Note that the silicon disposed in the crucible is, for example, high-purity silicon (9N). The upper part of the etching crucible is maintained at about 1700 ° C., and the lower part is maintained at about 1600 ° C., and held for about 1 hour. Thereby, main surface 1A of seed substrate 1 made of single crystal silicon carbide is etched in a silicon gas atmosphere. The thickness of the etching is, for example, about 0.2 μm or more and 0.5 μm or less. By this etching, the damage layer (layer including defects and dislocations) on the main surface 1A of the seed substrate 1 is removed.

  Next, silicon carbide raw material 8 is prepared. Silicon carbide raw material 8 is made of, for example, polycrystalline silicon carbide powder. As silicon carbide raw material 8, for example, high-purity α-silicon carbide powder can be used. The silicon carbide powder has, for example, an average particle size of about 100 μm and a maximum particle size of about 200 μm. Moreover, the silicon carbide powder contains silicon carbide fine powder of about 2 to 3 μm, for example. The fine powder in the present embodiment is, for example, a silicon carbide powder having a particle size of 30 μm or less, and preferably a silicon carbide powder having a particle size of 10 μm or less.

  Next, a step of removing fine powder contained in the silicon carbide raw material is performed. Specifically, referring to FIG. 5, silicon carbide raw material 8 is washed with liquid 13. As the liquid 13, for example, hydrochloric acid having a concentration of 35% can be used. Since silicon carbide has a higher specific gravity than hydrochloric acid, it basically sinks into hydrochloric acid. However, the fine powder 8a of silicon carbide floats on the liquid surface due to the surface tension of hydrochloric acid (liquid). The fine powder 8a is separated and removed from the silicon carbide raw material 8 by scooping only the fine powder 8a floating on the liquid surface. As described above, silicon carbide fine powder 8a contained in silicon carbide raw material 8 is reduced. In addition, it is preferable that the process of reducing the fine powder 8a contained in the silicon carbide raw material 8 is performed before the silicon carbide raw material partial sublimation process mentioned later.

  Next, the silicon carbide raw material 8 is washed with aqua regia (a liquid obtained by mixing hydrochloric acid having a concentration of 35% and sulfuric acid having a concentration of 60% in a volume ratio of 3: 1). Thereafter, silicon carbide raw material 8 is washed with pure water. Preferably, cleaning of silicon carbide raw material 8 with hydrochloric acid, aqua regia and pure water is performed a plurality of times. Preferably, the washing is repeated until there is no visible fine powder 8a. As described above, the silicon carbide raw material 8 is immersed in an acidic liquid such as hydrochloric acid or aqua regia, and the fine powder 8a made of silicon carbide floating on the surface of the liquid is removed. Thereafter, silicon carbide raw material 8 is taken out from beaker 12 and dried.

  Next, a silicon carbide raw material arrangement step (S10: FIG. 1) is performed. Referring to FIG. 2, in the silicon carbide raw material arranging step, silicon carbide raw material 8 is accommodated in raw material accommodating portion 7 of growth vessel 10. Preferably, a silicon carbide raw material from which fine powder made of silicon carbide has been removed by the cleaning step is used.

  Next, a silicon carbide raw material partial sublimation step (S20: FIG. 1) is performed. Specifically, referring to FIG. 2, growth vessel 10 in which silicon carbide raw material 8 is arranged is installed in a high-frequency heating furnace. After evacuating the high-frequency heating furnace, the pressure is maintained at, for example, 800 kPa while introducing an inert gas such as argon gas. While maintaining the pressure at, for example, 800 kPa, the temperature of the lower portion of the growth vessel 10 (that is, the bottom of the raw material container 7) is set to, for example, 2400 ° C., and the temperature of the upper portion of the growth vessel 10 (that is, the seed substrate holding portion 3). Is 2200 ° C., for example. Thereafter, the pressure of the high-frequency heating furnace is reduced to, for example, 4 kPa, and this state is maintained for about 24 hours. Thereby, the fine powder contained in silicon carbide raw material 8 and the damaged layer of silicon carbide raw material 8 preferentially sublimate. Thereafter, after the pressure of the high-frequency heating furnace is returned to, for example, 800 kPa, the growth vessel 10 is cooled to room temperature. In the silicon carbide raw material partial sublimation process, the seed substrate 1 is not disposed in the seed substrate holding part 3 of the growth vessel 10.

  When the seed substrate holding part 3 is observed after the partial sublimation process of the silicon carbide raw material, a large number of silicon carbide crystal nuclei having a diameter of several millimeters are scattered in the seed substrate holding part 3. That is, when the silicon carbide raw material is partially sublimated while holding the seed substrate 1 on the seed substrate holding part 3, crystal nuclei adhere to the seed substrate 1. Therefore, it is preferable not to arrange a seed substrate in the silicon carbide raw material partial sublimation step.

  The silicon carbide raw material 8 remaining in the raw material container 7 after the silicon carbide raw material partial sublimation step is integrated into a pumice shape (porous sintered body). When the sintered silicon carbide raw material 8 is subjected to machining such as pulverization, fine powder is generated again. Therefore, after sublimating a part of silicon carbide raw material 8, it is preferable to perform the growth of a silicon carbide crystal, which will be described later, without machining the rest of silicon carbide raw material 8.

  Moreover, the silicon carbide raw material partial sublimation step may be performed in a vacuum or may contain impurities that do not adversely affect the growth of the silicon carbide single crystal. For example, the disappearance of the fine powder 8a may be promoted by adding hydrogen or halogen to the atmosphere gas. Since hydrogen and halogen function as an etching gas, the disappearance of the fine powder 8a is promoted by chemical etching in addition to the sublimation of the silicon carbide raw material.

  Next, a seed substrate arrangement step (S30: FIG. 1) is performed. Specifically, referring to FIG. 3, seed substrate holding part 3 of growth vessel 10 used in the silicon carbide raw material partial sublimation process is replaced with another seed substrate holding part 3 on which seed substrate 1 is arranged. The As described above, after sublimating a part of silicon carbide raw material 8, seed substrate 1 having main surface 1 </ b> A is placed in growth vessel 10.

  Next, a silicon carbide crystal growth step (S40: FIG. 1) is performed. Specifically, referring to FIG. 3, growth vessel 10 in which seed substrate 1 and silicon carbide raw material 8 are arranged is again installed in the high-frequency heating furnace. Thereafter, the high-frequency heating furnace is evacuated, and the pressure is maintained at, for example, 800 kPa while introducing a mixed gas of argon gas and nitrogen gas (1%). While maintaining the pressure maintained at, for example, 800 kPa, the temperature of the lower portion of the growth vessel 10 (that is, the bottom portion of the raw material storage unit 7) is set to, for example, 2400 ° C. Is 2200 ° C., for example. Thereafter, the pressure is reduced over 1 hour until the pressure of the high-frequency heating furnace reaches, for example, 2 kPa. Referring to FIG. 4, silicon carbide raw material 8 is sublimated and recrystallized on main surface 1 </ b> A of seed substrate 1, so that silicon carbide single crystal 11 grows on main surface 1 </ b> A of seed substrate 1. After silicon carbide single crystal 11 is grown for 100 hours, for example, the pressure of the high-frequency heating furnace is again set to 800 kPa, for example. Thereafter, the temperature of the growth vessel 10 is returned to room temperature. As described above, silicon carbide single crystal 11 is grown on main surface 1A of seed substrate 1 by sublimating the remainder of silicon carbide raw material 8.

  Preferably, after silicon carbide raw material is partially sublimated, silicon carbide single crystal 11 is grown without machining the remainder of the silicon carbide raw material. For example, when machining such as grinding is performed on a silicon carbide raw material, fine powder is generated in the silicon carbide raw material. Preferably, after silicon carbide raw material 8 is partially sublimated and before silicon carbide single crystal 11 is grown, impact is not applied to silicon carbide raw material 8.

  Next, the silicon carbide single crystal 11 is taken out from the growth vessel 10. Thereafter, silicon carbide single crystal 11 is sliced with, for example, a wire saw to obtain a silicon carbide substrate.

  In the present embodiment, the method of partially sublimating silicon carbide raw material 8 in growth vessel 10 has been described, but the present invention is not limited to this method. For example, after silicon carbide raw material 8 is partially sublimated in a container different from growth vessel 10, the remaining silicon carbide raw material 8 is not subjected to machining, and the remaining silicon carbide raw material 8 is transferred to growth vessel 10. Instead, the silicon carbide single crystal 11 may be grown on the main surface 1A of the seed substrate 1 by sublimating the remaining silicon carbide raw material 8 thereafter.

Next, the effect of the method for manufacturing the silicon carbide substrate according to the present embodiment will be described.
According to the method for manufacturing a silicon carbide substrate according to the present embodiment, after a portion of silicon carbide raw material 8 is sublimated, the remainder of silicon carbide raw material 8 is sublimated, so that main surface 1A of seed substrate 1 is carbonized. A silicon single crystal 11 grows. Thereby, the silicon carbide single crystal 11 can be grown on the main surface 1A of the seed substrate 1 after the fine powder or the damaged layer causing the increase of dislocation is sublimated and removed preferentially in the initial stage of crystal growth. . Moreover, since the seed substrate 1 is disposed in the growth vessel 10 after a part of the silicon carbide raw material 8 is sublimated, it is possible to prevent the seed substrate 1 from being contaminated by the sublimated fine powder and the damaged layer. As a result, a silicon carbide substrate with few dislocations can be obtained.

  In addition, according to the method for manufacturing a silicon carbide substrate in accordance with the present embodiment, after the step of sublimating part of silicon carbide raw material 8, the remaining silicon carbide raw material 8 is not machined and the silicon carbide single body is processed. A step of growing the crystal 11 is performed. Thereby, it can prevent that a fine powder and a damage layer generate | occur | produce in the remainder of the silicon carbide raw material 8. FIG.

Furthermore, according to the method for manufacturing a silicon carbide substrate according to the present embodiment, a value obtained by subtracting the second dislocation density immediately below main surface 1A from the first dislocation density immediately above main surface 1A of seed substrate 1 is 1 × 10. ³ cm ^-2 or less. Thereby, a silicon carbide substrate with few dislocations can be obtained effectively.

  Furthermore, the method for manufacturing a silicon carbide substrate according to the present embodiment further includes the step of reducing silicon carbide fine powder 8 a contained in silicon carbide raw material 8 before sublimating a part of silicon carbide raw material 8. Thereby, a silicon carbide substrate with few dislocations can be obtained more effectively.

  Furthermore, according to the method for manufacturing the silicon carbide substrate according to the present embodiment, the step of reducing silicon carbide fine powder 8a is performed by immersing silicon carbide raw material 8 in hydrochloric acid and aqua regia and floating on the surface of hydrochloric acid and aqua regia. This is done by removing the silicon carbide fine powder 8a. Thereby, silicon carbide fine powder 8a can be removed from silicon carbide raw material 8 by a simple method.

  In this example, a silicon carbide single crystal was grown by the three types of methods described below, and the increase rate of the dislocation density in the main surface 1A of the seed substrate 1 was investigated. Except for the differences described below, the silicon carbide crystals of the present invention example, comparative example 1 and comparative example 2 were produced by the same method as described in the embodiment. The method for producing silicon carbide single crystal 11 of Comparative Example 2 uses commercially available silicon carbide raw material 8 as it is, and does not have a partial sublimation process of silicon carbide raw material, and a process of removing fine powder by acid cleaning before sublimation. Is different from the manufacturing method of the example of the present invention in that it does not have, and is the same as the manufacturing method of the example of the present invention in other points. The manufacturing method of the silicon carbide single crystal 11 of Comparative Example 1 is different from the manufacturing method of the present invention in that it does not have a partial sublimation process of the silicon carbide raw material. It is the same.

  Next, a method for obtaining the increase rate of the dislocation density in the main surface 1A of the seed substrate 1 will be described. First, referring to FIG. 6, silicon carbide single crystal 11 grown on main surface 1 </ b> A of seed substrate 1 is taken out, and silicon carbide single crystal 11 is sliced along a plane parallel to main surface 1 </ b> A of seed substrate 1. A substrate having seed substrate 1 and silicon carbide single crystal 11 is prepared. Next, referring to FIG. 7, polishing of the substrate is started from the silicon surface 1B side, and the seed substrate 1 is polished so that the thickness of the seed substrate 1 from the main surface 1A (that is, the growth interface) becomes the thickness T1. The The thickness T1 of the remaining seed substrate 1 was set to about 100 μm. The threading dislocation density on the surface 1C of the seed substrate 1 was evaluated using KOH (potassium hydroxide) etching.

  Thereafter, referring to FIG. 8, the substrate was further polished, and after seed substrate 1 was all polished, silicon carbide single crystal 11 was polished by thickness T2. The thickness T2 of the polished silicon carbide single crystal 11 was set to about 100 μm. Thereby, silicon carbide single crystal 11 with surface 11A exposed was obtained. The threading dislocation density on the surface 11A of the silicon carbide single crystal 11 was evaluated using KOH etching.

  The threading dislocation density was measured at 177 locations (10 mm pitch) on the surface 1C and the surface 11A. The area of each measurement location was 2 mm × 2 mm. From the threading dislocation density (first dislocation density) on the surface 11A of the silicon carbide single crystal 11 (that is, immediately above the main surface 1A), the threading dislocation density (second dislocation density) on the surface 1C of the seed substrate 1 (that is, immediately below the main surface 1A). ) Was taken as the rate of increase of threading dislocation density. In addition, in order to measure at the same position in the direction perpendicular to the main surface 1A immediately above and below the main surface, positioning marking was performed by laser processing.

The result of the increase rate of threading dislocation density will be described with reference to Table 1. The increase rate of the threading dislocation density in the example of the present invention is +30 cm ⁻² (+3 in the measurement area) at the maximum, −175 cm ⁻² (−7 in the measurement area) at the minimum, and on average It was −30 cm ⁻² (−1.2 in the measurement area). Here, “+” means that the threading dislocation density has increased, and “−” means that the threading dislocation density has decreased. In addition, it is difficult to accurately evaluate the increase / decrease in the dislocation density because there is a possibility of displacement of the position in the direction perpendicular to the main surface 1A immediately above and below the main surface and the movement of the dislocation position. The increase rate of the threading dislocation density in the inventive example is at least 1 × 10 ³ pieces cm ⁻² or less. In the examples of the present invention, the threading dislocation density is slightly reduced. This is presumably because dislocations having opposite Burgers vectors merged and disappeared in the early stage of growth. Further, the increase rate of threading dislocation density in Comparative Example 1 is about 3.7 × 10 ³ cm ⁻² , and the increase rate of threading dislocation density in Comparative Example 2 is about 8.5 × 10 ⁴ cm ⁻² . there were.

  From the above results, it was confirmed that a silicon carbide crystal having a low dislocation density can be obtained by sublimating a part of the silicon carbide raw material before crystal growth of silicon carbide. Further, it was confirmed that a silicon carbide crystal having a lower dislocation density can be obtained by removing silicon carbide fine particles by acid cleaning the silicon carbide raw material before partially sublimating the silicon carbide raw material.

  The embodiments and examples disclosed herein are illustrative in all respects and should not be construed as being restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1 type substrate, 1A main surface, 1B silicon surface, 1C surface, 2a, 2b through-hole, 3 type substrate holding part, 4 heat insulating material, 7 material containing part, 8 silicon carbide material, 8a fine particle, 10 growth vessel, 11 carbonization Silicon single crystal, 11A surface, 12 beakers, 13 liquid.

Claims (4)

Disposing a silicon carbide raw material in a first growth vessel having a raw material containing portion and a first seed substrate holding portion;
Placing the first growth vessel in a heating furnace and sublimating a part of the silicon carbide raw material in a state where no seed substrate is disposed in the first seed substrate holding part;
After the step of sublimating a part of the silicon carbide raw material, a step of disposing a seed substrate having a main surface in a second seed substrate holding unit different from the first seed substrate holding unit;
Growing a silicon carbide crystal on the main surface of the seed substrate by sublimating the remainder of the silicon carbide raw material in a second growth vessel having the raw material container and the second seed substrate holder. With
Sublimating a part of the silicon carbide raw material,
A first step of maintaining the heating furnace at a first pressure and heating the first growth vessel to 2200 ° C. or higher;
After the first step, the carbonization is performed on the first seed substrate holder by maintaining the heating furnace at a second pressure lower than the first pressure while maintaining heating of the first growth vessel. A second step of sublimating a portion of the silicon raw material;
After the second step, cooling the first growth vessel to room temperature,
Before sublimating a part of the silicon carbide raw material, further comprising the step of reducing the silicon carbide fine powder contained in the silicon carbide raw material,
The method of reducing the silicon carbide fine powder is performed by immersing the silicon carbide raw material in an acid and removing the silicon carbide fine powder floating on the surface of the acid.   2. The carbonization according to claim 1, wherein after the step of sublimating a part of the silicon carbide raw material, the step of growing the silicon carbide crystal without performing machining on the remainder of the silicon carbide raw material is performed. A method for manufacturing a silicon substrate. A position 100 μm away from the main surface to the opposite side of the second seed substrate holder from the first dislocation density at a position 100 μm away from the main surface of the seed substrate to the second seed substrate holder. ^{3. The} method for manufacturing a silicon carbide substrate according to claim 1, wherein a value obtained by subtracting the second dislocation density is 1 × 10 ³ cm ⁻² or less. The step of reducing the silicon carbide fine powder is performed by immersing the silicon carbide raw material in hydrochloric acid and aqua regia to remove the silicon carbide fine powder floating on the surface of the hydrochloric acid and the aqua regia. Item 4. A method for manufacturing a silicon carbide substrate according to any one of Items 1 to 3.

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