Manufacturing method of silicon carbide single crystal, and manufacturing apparatus of silicon carbide single crystal

Abstract

To suppress local erosion of graphite in a crucible while suppressing incorporating of carbon particles caused by graphite in a crucible into a silicon carbide single crystal in manufacturing a silicon carbide single crystal.SOLUTION: In a growth space 11 of a crucible 1, which is a region from a position of a surface 40a of an attached seed crystal 40 to a position of a surface 50a of a raw material 50 of SiC, a part of a side face 12 exposed to sublimation gas from the raw material 50 is covered by a coating member 30. The coating member 30 is constituted of metal carbide having a higher melting point than the growth temperature of SiC, and covers a partial predetermined region from the position of the surface 40a of the seed crystal 40 toward the raw material 50 side of the side face 12.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a silicon carbide (hereinafter referred to as "SiC") single crystal manufacturing method and SiC single crystal manufacturing apparatus used in manufacturing SiC single crystal. [Background technology]

[0002] Conventionally, as a method for producing a SiC single crystal, in which a heating means arranged on the outer periphery of a graphite crucible is used to grow the SiC single crystal in the crucible, a sublimation recrystallization method is known. In the sublimation recrystallization method, a seed crystal is arranged on the top of the graphite crucible, and a SiC powder raw material arranged on the bottom of the crucible is heated to, for example, 2300°C to sublimate the SiC powder raw material, and the sublimated gas is recrystallized on the seed crystal set at a temperature lower than the raw material temperature. As a method and apparatus for producing a SiC single crystal of this type, the one described in Patent Document 1 has been proposed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4957672 Summary of the Invention [Problem to be solved by the invention]

[0004] The SiC single crystal manufacturing apparatus described in Patent Document 1 has a skirt portion in the shape of a truncated cone that expands in a tapered shape around a seed crystal, and the entire surface of the skirt portion is covered with a TaC member made of tantalum carbide (TaC). This TaC member is formed into a cup shape that conforms to the inner wall surface of the skirt portion by deep drawing a plate-shaped TaC, and has a seamless shape, preventing the graphite on the inner wall surface of the skirt portion from being exposed. As a result, the SiC single crystal manufacturing apparatus described above can suppress the deterioration of the crystal quality of the SiC single crystal caused by carbon originating from the graphite in the skirt portion being taken into the SiC single crystal grown on the seed crystal, and the occurrence of defects caused by seams and cuts in the TaC member.

[0005] On the other hand, in this type of SiC single crystal manufacturing apparatus, it has been newly discovered that if the entire area of ​​the inner wall surface of the crucible in which the SiC powder raw material is placed is covered with a coating material with a higher melting point than SiC, such as TaC, the carbon atoms become insufficient and silicon becomes excessive, which in turn reduces the crystal quality of the SiC single crystal. Therefore, the inventors of the present invention considered locally exposing a part of the inner wall surface of the crucible that is far from the seed crystal, and it became further clear that repeated production of SiC single crystals causes the part of the area to be worn out and a hole to be formed in the crucible. In this case, problems occur such as dust generated by the opening of a hole in the crucible being taken into the SiC single crystal, or gas obtained by sublimating the SiC powder raw material escaping from the hole to the outside of the crucible.

[0006] The present disclosure aims to provide a method and apparatus for producing a SiC single crystal that is capable of suppressing the incorporation of carbon derived from the graphite in the crucible and the deterioration of the crystal quality of the SiC single crystal that is caused by localized wear of the crucible. [Means for solving the problem]

[0007] According to one aspect of the present disclosure, a method for producing a silicon carbide single crystal comprises preparing a hollow cylindrical crucible (1) having a bottomed cylindrical container body (10), a lid (20) for closing an opening of the container body, and a covering member (30) made of metal carbide having a melting point higher than the growth temperature of silicon carbide and disposed inside the container body; arranging a seed crystal (40) made of a silicon carbide substrate in the lid; arranging a silicon carbide raw material (50) in the container body; and then supplying a sublimation gas of the silicon carbide raw material. and growing a silicon carbide single crystal (60) on the seed crystal. In preparing a crucible, the space in the crucible from a height position (1A) of the surface (40a) of the seed crystal to a height position (1B) of the surface (50a) of the silicon carbide raw material, in which a sublimation gas is filled, is defined as a growth space (11), the wall surfaces (10a, 70a) of the growth space are defined as side surfaces (12), the covering member is tubular along the side surfaces, and a predetermined region of the side surfaces from the height position of the surface of the seed crystal is covered with the covering member.

[0008] According to this, the method for producing a SiC single crystal includes preparing a crucible having a container body, a lid body, and a covering member, placing a seed crystal on the lid body, placing a SiC raw material on the container body, and then sublimating the SiC raw material to grow a SiC single crystal on the seed crystal. Then, a cylindrical covering member made of a metal carbide having a melting point higher than the growth temperature of SiC is prepared, and a part of the side of the growth space, which is a space in the crucible from the surface position of the seed crystal to the surface position of the SiC raw material and is filled with a sublimation gas of the SiC raw material, is covered with the covering member. In addition, the region covered with the covering member is a predetermined part of the side from the surface position of the seed crystal toward the SiC raw material. This method for producing a SiC single crystal covers the graphite near the seed crystal surface on the side of the crucible with the covering member, so that carbon derived from the graphite can be suppressed from being taken into the SiC single crystal. Furthermore, in this method for producing SiC single crystals, a sufficient area of ​​graphite is exposed in the region of the side surface away from the seed crystal surface, thereby making it possible to suppress localized wear and the occurrence of holes in the crucible.

[0009] According to another aspect of the present disclosure, a silicon carbide single crystal manufacturing apparatus includes a crucible (1) having a bottomed cylindrical container body (10), a member to which a seed crystal (40) made of a silicon carbide substrate is attached, the crucible having a lid (20) that closes an opening of the container body, and a covering member (30) made of a metal carbide having a melting point higher than a growth temperature of silicon carbide, and a portion of the crucible located on a surface (50a) of a silicon carbide raw material (50) placed therein is set to a raw material height position (1 The seed crystal height position (1A) is a portion located on the surface (40a) of the seed crystal to be placed, the space from the raw material height position to the seed crystal height position and filled with sublimation gas of the silicon carbide raw material is a growth space (11), the wall surface (10a, 70a) of the crucible in the growth space is a side surface (12), and the covering member is cylindrical along the side surface and covers a predetermined region of the side surface from the seed crystal height position toward the raw material height position.

[0010] According to this, the SiC single crystal manufacturing apparatus is configured such that, in the growth space from the surface of the seed crystal to the surface of the SiC raw material in the crucible, a certain region from the seed crystal surface of the side surface exposed to the sublimation gas is covered with a covering member made of a metal carbide having a higher melting point than SiC. Since the side surface of the crucible in the vicinity of the seed crystal surface is covered with graphite in the SiC single crystal manufacturing apparatus, it is possible to suppress the incorporation of carbon derived from graphite into the SiC single crystal. Furthermore, since the graphite is exposed in the region of the side surface away from the surface of the seed crystal in the SiC single crystal manufacturing apparatus, it is possible to suppress the localized wear and hole formation of the crucible while preventing the sublimation gas of the raw material from becoming excessively silicon.

[0011] The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and specific components described in the embodiments described below. [Brief description of the drawings]

[0012] [Figure 1] 1 is a diagram showing a cross-sectional configuration of a SiC single crystal manufacturing apparatus according to a first embodiment. [Diagram 2]FIG. 1 is a graph showing the relationship between the coverage of the side surface by the covering member in the growth space and the density of carbon inclusions in the SiC single crystal. [Diagram 3] FIG. 4 is a diagram showing a cross-sectional configuration of a SiC single crystal manufacturing apparatus according to a second embodiment. [Figure 4] FIG. [Diagram 5] 10A to 10C are explanatory views of the carbonization treatment of the covering member that covers the skirt portion. [Figure 6] FIG. 11 is a diagram showing a cross-sectional configuration of a SiC single crystal manufacturing apparatus according to a third embodiment. [Figure 7] FIG. 13 is a diagram showing a modified example of the SiC single crystal manufacturing apparatus of the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other will be denoted by the same reference numerals.

[0014] (First embodiment) The SiC single crystal manufacturing apparatus of the first embodiment will be described with reference to the drawings. In Fig. 1, although they are not part of the SiC single crystal manufacturing apparatus, in order to make the manufacturing method easier to understand, a seed crystal 40 and a raw material 50 arranged in a crucible 1 described later, and a SiC single crystal 60 growing on the seed crystal 40 are shown. This also applies to Figs. 3, 6, and 7 described later.

[0015] [Basic configuration] 1, the SiC single crystal manufacturing apparatus includes a crucible 1 including a bottomed cylindrical container body 10, a circular lid body 20, and a covering member 30. The crucible 1 has a hollow cylindrical shape, with the container body 10 and the lid body 20 made of graphite, for example.

[0016] The container body 10 has, for example, a SiC raw material 50, which is a supply source of sublimation gas, disposed at the bottom of the inner cylinder. The raw material 50 is, for example, powdered SiC crystal. The container body 10 has the opening on the lid body 20 side facing up, and the wall surface on the side where the raw material 50 is disposed is the inner wall surface 10a, and a predetermined region of the inner wall surface 10a is covered by the covering member 30 from the upper side. In the present embodiment, the container body 10 has a predetermined region of the inner wall surface 10a, which is covered by the covering member 30 from the height position of the surface 40a of the seed crystal 40, and the inner wall surface 10a is exposed in other regions. When the powdered SiC crystal raw material 50 is sublimated, Si-excessive sublimation gas such as Si and Si2C is generated, so if the entire side surface 12 described later is covered by the covering member 30, carbon in the SiC single crystal may be insufficient, and the crystal quality may be reduced. In addition, it is difficult to adjust the Si / C ratio in the powdered SiC crystal and suppress the generation of Si-excessive sublimation gas. For this reason, by leaving a part of the inner wall surface 10a of the container body 10 uncovered with the covering member 30, carbon atoms from the part of the graphite are used for recrystallization of SiC, and serve to suppress deterioration of crystal quality caused by Si-excessive sublimation gas. For example, the entire lower region of the inner wall surface 10a on the source material 50 side from a position a predetermined distance away from the surface 40a of the seed crystal 40 is left as a region not covered with the covering member 30 and has a large area, suppressing localized wear during the growth process of the SiC single crystal.

[0017] Hereinafter, for convenience of explanation, as shown in FIG. 1, the position of the surface 40a of the seed crystal 40 in the crucible 1 is referred to as the "height position 1A", and the position of the surface 50a of the raw material 50 is referred to as the "height position 1B". The height position here means a position in the height direction, for example, a direction connecting the bottom surface 10b and the opening closed by the lid body 20 along a normal direction to the bottom surface 10b inside the crucible 1. Hereinafter, in the above-mentioned height direction, the lid body 20 side may be referred to as the upper side, and the bottom surface 10b side of the inside of the container body 10 may be referred to as the lower side. In addition, the space from the height position 1A to the height position 1B in the crucible 1, which is filled with the sublimation gas of the raw material 50, is referred to as the "growth space 11", and the wall surface of the growth space 11 is referred to as the "side surface 12".

[0018] The position of the surface 50a of the raw material 50 is the position of the flat surface when the surface 50a is arranged flat, for example, by tapping the crucible 1 after the raw material 50 is put into the container body 10. In addition, the position of the surface 50a of the raw material 50 is the average position in the height direction of the unevenness of the outermost surface of the raw material 50 on the seed crystal 40 side, or the average position in the height direction of the part of the outermost surface that contacts the inner wall surface 10a, when the raw material 50 is not arranged flat. In addition, since the seed crystal 40 has a thin thickness that can be ignored, the region below the height position of the surface of the lid 20 to which the seed crystal 40 is attached may be regarded as the growth space 11. In addition, for example, when the region of the container body 10 where the raw material 50 is arranged is regarded as the raw material arrangement region, and some mark indicating the upper end of the raw material arrangement region is attached to the inner wall surface 10a, the region above the mark may be regarded as the growth space 11.

[0019] In this embodiment, side surface 12 is a part of inner wall surface 10a of container body 10, and is configured as a portion exposed to sublimation gas of raw material 50. Side surface 12 has a height dimension of, for example, about 30 mm to 500 mm, depending on the height from bottom surface 10b of raw material 50, i.e., the amount. The height dimension of side surface 12 is the dimension of growth space 11, and can be changed as appropriate depending on the size and thickness of SiC single crystal 60 to be obtained.

[0020] The lid body 20 is, for example, disk-shaped, and a SiC seed crystal 40 is attached to the surface that closes the opening of the container body 10. The seed crystal 40 is, for example, a SiC substrate, and is attached so that a surface 40a faces away from the lid body 20.

[0021] The covering member 30 is made of a carbide having a melting point higher than the growth temperature of SiC, which will be described later, and covers a predetermined region of the inner wall surface 10a of the container body 10 from the height position 1A of the seed crystal 40. The covering member 30 is provided to prevent graphite from being exposed in the region of the inner wall surface 10a of the container body 10 near the seed crystal 40, and thus to prevent carbon particles from the graphite from being taken into the SiC single crystal 60 grown on the seed crystal 40, causing deterioration in the quality of the crystal.

[0022] For ease of explanation, the end of the covering member 30 on the seed crystal 40 side may be referred to as the "upper end" and the end of the covering member 30 on the raw material 50 side may be referred to as the "lower end". The covering member 30 covers the entire region of the side surface 12 located from the upper end to the lower end of the covering member 30. The upper end of the covering member 30 coincides with the height position 1A, that is, the position of the surface 40a of the seed crystal 40, for example.

[0023] The covering member 30 is made of any one of carbides of tantalum, niobium, tungsten, and titanium, for example. The covering member 30 is attached to a part of the side surface 12 from the height position 1A toward the height position 1B, for example, and is cylindrical along the side surface 12. For example, the covering member 30 has a covering portion in the part of the side surface 12 that is covered by the covering member 30, and the ratio of the area of ​​the covering portion to the area of ​​the entire side surface 12 is the covering rate, which is set within a predetermined range described later.

[0024] Specifically, as shown in FIG. 2, when the coverage is in the range of 10% to 60%, the carbon inclusion density, which is the density of carbon particles mixed in the SiC single crystal 60, is 1 cm -3 The carbon inclusion density began to increase when the coverage rate was less than 10%, and reached 100 cm at a coverage rate of 5%. -3 When the coverage rate becomes less than 5%, the value increases dramatically to 1000 cm -3 The carbon inclusion density also began to increase when the coverage exceeded 60%, and exceeded 100 cm at a coverage of 80%. -3 When the coverage rate exceeds 80%, the value increases dramatically to 1000 cm -3This result shows that by setting the coverage within the range of 5% to 80%, more preferably 10% to 60%, the crystal quality of SiC single crystal 60 can be ensured satisfactorily.

[0025] The carbon inclusion density on the vertical axis of Fig. 2 was measured by growing the SiC single crystal 60 to the lowest height position on the raw material 50 side of the portion of the side surface 12 covered with the coating member 30, and then extracting a 1 mm thick substrate crystal from the surface 60a of the SiC single crystal 60. The carbon inclusion density in Fig. 2 was obtained by observing the 1 mm thick substrate crystal with an optical microscope and counting the number of carbon inclusions with a diameter of 1 µm or more observed in a predetermined area of ​​the substrate crystal. Furthermore, according to the study by the present inventors, the carbon inclusion density of the SiC single crystal 60 was found to be independent of the inner diameter or height dimension of the side surface 12.

[0026] The covering member 30 can be obtained, for example, by preparing a plate material having a thickness of 0.1 mm to 3 mm and made of the above-mentioned metal material, processing the plate material into a shape that conforms to the inner wall surface 10a of the container body 10, and then carbonizing the plate material. For example, a graphite member having a shape that conforms to the inner wall surface 10a of the container body 10 is prepared, and the processed plate material is placed adjacent to the graphite member and then carbonized by performing a heat treatment at 1500°C to 2500°C in an inert atmosphere, for example, an argon atmosphere. For example, the above process can obtain the covering member 30 made of a metal carbide. As a result, compared to a case where a metal carbide is used as a covering layer by a film formation method such as CVD, a covering member 30 without pinholes or cracks can be formed even when the diameter of the side surface 12 is, for example, 6 inches or more, and the SiC single crystal 60 can be stably manufactured.

[0027] For example, when the covering member 30 is made of tantalum carbide, the ratio of carbon to tantalum is defined as the C / Ta ratio, which is in the range of 0.2 to 1. This is based on the results of performing crystal growth on tantalum carbide covering members with C / Ta ratios of 0, 0.2, 0.4, 0.6, 0.8, and 1.0, and confirming the deformation and damage of the covering member 30 due to the crystal growth. When the C / Ta ratio is in the range of 0.2 to 1, good crystal growth was possible. On the other hand, when the C / Ta ratio is less than 0.2, the covering member 30 may be damaged due to excessive dimensional change during growth of the SiC single crystal 60 and partial silicidation resulting in a low melting point. This result was independent of the coverage rate of the covering member 30.

[0028] In addition, when the covering member 30 is made of, for example, tantalum carbide and the C / Ta ratio is within a range of 0.2 to 1, the change rate of the dimensions and weight due to the carbonization is 1% to 10% based on the dimensions and weight before the carbonization. Specifically, when the C / Ta ratio is less than 0.2, the change rate of the dimensions and weight of the covering member 30 during the SiC crystal growth process is large, exceeding 10%, and deformation and damage occurred. On the other hand, when the C / Ta ratio is within a range of 0.2 to 1, the dimensions and weight of the covering member 30 change in advance during the carbonization process, so that large deformation and damage of the covering member 30 during the SiC crystal growth process can be prevented. It is preferable that the dimensions of the covering member 30 before the carbonization process are determined in consideration of the change rate of the dimensions and weight due to the carbonization process so that the dimensions after the carbonization process are approximately the same as the inner diameter of the inner wall surface 10a.

[0029] The C / Ta ratio in the tantalum carbide can be calculated, for example, by the following method. First, the tantalum member after carbonization is powdered, and the obtained powder is subjected to X-ray diffraction measurement. For various peaks obtained by this X-ray diffraction measurement, the peak heights derived from each crystal phase of TaC with NaCl structure, Ta3C2 and Ta4C3 with trigonal crystals, Ta2C with hexagonal crystals, and Ta with body-centered cubic crystals are confirmed, and the ratio of each crystal phase is identified. The carbon ratio in each of the above structures is 1 for TaC with NaCl structure, 0.67 to 0.75 for Ta3C2 and Ta4C3 with trigonal crystals, 0.5 for Ta2C with hexagonal crystals, and 0 for Ta with body-centered cubic crystals. Then, the C / Ta ratio in each growth phase is identified from the lattice constant of each crystal phase, and the C / Ta ratio in the tantalum carbide can be calculated from the overall ratio. For this reason, it is considered that the average C / Ta ratio in the entire region of the coating member 30 should be within the range of 0.2 to 1.

[0030] Furthermore, the SiC single crystal manufacturing apparatus has a heating means (not shown) arranged so as to surround the outer periphery of the crucible 1 .

[0031] The above is the configuration of the SiC single crystal manufacturing apparatus according to this embodiment.

[0032] [Method of manufacturing SiC single crystal] Next, an example of a method for producing SiC single crystal 60 using the above-mentioned SiC single crystal production apparatus will be described.

[0033] 1, a crucible 1 having a container body 10, a lid 20, and a covering member 30 is prepared, a seed crystal 40 is attached to the inner surface of the lid 20, and a raw material 50 is placed on the bottom surface 10b of the container body 10. The seed crystal 40 is prepared, for example, in the form of a substantially circular plate with a diameter in the range of 150 mm to 220 mm.

[0034] Next, for example, the crucible 1 is placed in a heating chamber (not shown) and heated by any heating means such as a heater whose position is fixed, and the crucible 1 is heated by the radiant heat to a predetermined temperature inside the crucible 1. At this time, for example, the growth space 11 in the crucible 1 is made into an Ar atmosphere with a pressure of about 100 Pa to 10000 Pa, the temperature of the raw material 50 is made about 2100° C. to 2400° C., and the temperature of the seed crystal 40 is made about 2000° C. to 2300° C., which is lower than that of the raw material 50.

[0035] The atmosphere in the chamber is obtained by, for example, flowing in an inert gas such as Ar gas through an air supply pipe (not shown) while discharging air through an exhaust pipe (not shown). In addition, until the temperature of the growth surface (surface 40a) of the seed crystal 40 and the temperature of the raw material 50 are raised to the target temperature, for example, the pressure in the heating chamber is kept close to atmospheric pressure to suppress sublimation from the raw material 50, and when the target temperature is reached, the above-mentioned reduced pressure atmosphere is obtained.

[0036] As described above, by heating the raw material 50 in a reduced pressure atmosphere, the raw material 50 sublimes and a sublimation gas is generated from the raw material 50. This sublimation gas is supplied to the surface 40a of the seed crystal 40. As a result, the sublimation gas crystallizes on the surface 40a of the seed crystal 40, and a SiC single crystal 60 grows. In order to control the resistivity of the crystal, nitrogen gas is introduced as necessary.

[0037] In the crucible 1, the side surface 12 of the growth space 11 is covered with the covering member 30 made of a metal carbide having a melting point higher than the growth temperature of SiC. A predetermined region of the side surface 12 from the height position 1A of the seed crystal 40 is covered with the covering member 30 at a coverage rate of 5% to 80%, and graphite is exposed in the remaining part of the side surface 12. As a result, the graphite of the side surface 12 is not exposed in the vicinity of the seed crystal 40, and it is possible to suppress the carbon resulting from the graphite from being mixed into the SiC single crystal 60. In addition, since the graphite is exposed from the covering member 30 in the region of the side surface 12 far from the seed crystal 40, it is possible to suppress the partial consumption of the graphite of the side surface 12 in the growth process of the SiC single crystal 60 while preventing the Si in the sublimation gas of the raw material 50 from becoming excessive.

[0038] According to the present embodiment, an apparatus and method for producing a SiC single crystal are provided that are capable of suppressing the incorporation of carbon derived from the graphite in the crucible 1 and the deterioration of the crystal quality of the SiC single crystal 60 that is caused by localized wear of the crucible 1.

[0039] (1) By setting the coverage of the side surface 12 by the covering member 30 to 5% or more and 80% or less, more preferably 10% or more and 60% or less, the carbon inclusion density in the SiC single crystal 60 becomes a predetermined value or less, and good crystal quality can be ensured. Here, for example, in the closed space closed by the lid body 20 in the crucible 1 in a state before the raw material 50 is placed, the ratio of the dimensions in the height direction between the raw material placement region and the remaining region (corresponding to the growth space 11) is set to α:β (α and β are any positive numbers). In this case, the covering member 30 may be placed so that the coverage of the wall surface of the region from the end on the lid body 20 side downward to a ratio of β / (α+β) in the above-mentioned closed space is 5% to 80%, more preferably 10% to 60%.

[0040] (2) By growing SiC single crystal 60 within the range covered by covering member 30, carbon originating from exposed graphite on side surface 12 is prevented from being incorporated into SiC single crystal 60, making it possible to ensure good crystal quality. In other words, the height from surface 40a of seed crystal 40 to surface 60a of SiC single crystal 60 along the normal direction to surface 40a of seed crystal 40 is defined as the crystal height, and the crystal height of SiC single crystal 60 may be set within the range of the region covered by covering member 30.

[0041] (3) By forming the covering member 30 from any one of tantalum, niobium, tungsten, and titanium carbides, the melting point of the covering member 30 exceeds 2500° C. This allows the covering member 30 to maintain a stable shape at the growth temperature of the SiC single crystal 60, and the growth process of the SiC single crystal 60 can be performed stably.

[0042] (4) By forming the covering member 30 from tantalum carbide and setting the C / Ta ratio within the range of 0.2 to 1, it is possible to suppress the rate of change in size and weight before and after the carbonization process in obtaining the covering member 30 within the range of 1% to 10%. This allows the covering member 30 to maintain a stable shape and size during the SiC crystal growth process.

[0043] Second embodiment The SiC single crystal manufacturing apparatus of the second embodiment will be described with reference to the drawings.

[0044] The SiC single crystal manufacturing apparatus of this embodiment differs from the above-described first embodiment in that the crucible 1 further has a skirt portion 70, as shown in Fig. 3, for example. In this embodiment, this difference will be mainly described.

[0045] In the present embodiment, the crucible 1 has, for example, a cylindrical protrusion 21 on the lid body 20, a skirt portion 70 surrounding the seed crystal 40 in the vicinity of the seed crystal 40 on the container body 10, and the seed crystal 40 is attached to the tip of the protrusion 21. As shown in FIG. 3 and FIG. 4, the skirt portion 70 has a truncated cone shape with upper and lower openings, and the inner peripheral surface 70a is covered by the covering member 30. The skirt portion 70 has an upper and lower openings with a smaller diameter, which is disposed in the vicinity of the seed crystal 40. Hereinafter, for convenience of explanation, the opening with a smaller diameter located on the upper bottom surface of the truncated cone shape among the upper and lower openings of the skirt portion 70 may be referred to as a "small opening" and the opening with a larger diameter located on the lower bottom surface may be referred to as a "large opening". The skirt portion 70 plays a role in expanding the diameter of the grown crystal when the SiC single crystal 60 is grown on the seed crystal 40, and may also be referred to as, for example, a growth guide. The angle between the inner peripheral surface 70a and a virtual line passing through the central axes of the upper and lower openings of the skirt portion 70 is set as an inclination angle of the inner peripheral surface 70a, and is, for example, 45° or less.

[0046] The skirt portion 70 is made of, for example, graphite, and the covering member 30 is fixed to the inner peripheral surface 70a. The covering member 30 attached to the skirt portion 70 is manufactured, for example, by the following process. For example, as shown in FIG. 5, a plate material 31 made of a metal material such as Ta and having a thickness of 0.1 mm to 3 mm is prepared, and the plate material 31 is deep-drilled to have a shape corresponding to the inner peripheral surface 70a of the skirt portion 70. Next, for example, a part of the plate material 31 is folded by seaming to fix it to the small opening of the skirt portion 70, so that the plate material 31 covers the inner peripheral surface 70a of the skirt portion 70. Thereafter, a graphite member 100 having a shape conforming to the inner peripheral surface 70a of the skirt portion 70 is prepared, and the plate material 31 attached to the skirt portion 70 is disposed adjacent to the graphite member 100. Then, for example, the plate material 31 is carbonized by heat treatment at 1500° C. to 2500° C. in an argon atmosphere to form a metal carbide having a melting point higher than the growth temperature of SiC. As a result, the skirt portion 70 has a configuration in which a part or all of the inner circumferential surface 70a and the vicinity of the small opening are covered with the covering member 30 made of metal carbide.

[0047] In this embodiment, the growth space 11 is surrounded by the inner wall surface 10a of the vessel body 10 and the inner peripheral surface 70a of the skirt portion 70. That is, in this embodiment, the side surface 12 is composed of the region of the inner wall surface 10a of the vessel body 10 from the large opening of the skirt portion 70 to the surface 50a of the raw material 50 and the inner peripheral surface 70a of the skirt portion 70. The covering member 30 covers a predetermined region of the side surface 12 from the height position 1A of the seed crystal 40 on the inner peripheral surface 70a toward the height position 1B such that the coverage rate of the side surface 12 is 5% or more and 80% or less. The covering member 30 may be disposed so as to cover a part of the inner peripheral surface 70a, or may be disposed so as to cover the entire area of ​​the inner peripheral surface 70a or a part of the inner wall surface 10a in addition to the entire area of ​​the inner peripheral surface 70a. The coverage range of the side surface 12 by the covering member 30 can be appropriately changed depending on the crystal height of the SiC single crystal 60 to be obtained. In this embodiment as well, SiC single crystal 60 is obtained by growing within the area of ​​side surface 12 covered by covering member 30, with the lower end of covering member 30 being the upper limit of the crystal height.

[0048] According to this embodiment, the SiC single crystal manufacturing apparatus and manufacturing method can obtain the same effect as the first embodiment. In addition, the crucible 1 has a skirt portion 70 in a truncated cone shape, and the small opening is arranged to match the height position 1A of the seed crystal 40, so that the SiC single crystal 60 can be grown to a diameter size larger than that of the seed crystal 40. Note that FIG. 3 shows an example in which the upper end position of the covering member 30 covering the skirt portion 70 and the height position 1A of the surface 40a of the seed crystal 40 coincide with each other, but this is not limited to this example, and these positions may be approximately coincident. The term "approximately coincident" includes a case in which the upper end position of the covering member 30 coincides with the height position 1A of the seed crystal 40, as well as a case in which the upper end position of the covering member 30 is above or below the height position 1A due to, for example, an error in the dimensions of the skirt portion 70 or the attachment to the container body 10. Furthermore, "substantially coincident" also includes a case where the covering member 30 is intentionally disposed so that the upper end position is higher or lower than the height position 1A, within a range that does not interfere with the growth of the SiC single crystal 60 on the surface 40a of the seed crystal 40. For this reason, the skirt portion 70 may be disposed so that the upper end of the portion covered by the covering member 30 coincides with the surface 40a of the seed crystal 40 in the height direction, may be disposed so as to have a gap between the upper end and the surface 40a, or may be disposed so as to overlap the seed crystal 40.

[0049] Third embodiment The SiC single crystal manufacturing apparatus of the third embodiment will be described with reference to the drawings.

[0050] 6, the SiC single crystal manufacturing apparatus of this embodiment differs from the above-described first embodiment in that the crucible 1 further has, in addition to the skirt portion 70, a support portion 80 and a baffle plate 81 extending from the bottom surface 10b of the container body 10. Since the skirt portion 70 is the same as in the above-described second embodiment, in this embodiment, the support portion 80 and the baffle plate 81 will be mainly described.

[0051] The support part 80 is, for example, cylindrical and extends from the center of the bottom surface 10b of the container body 10 toward the opening side along the central axis of the crucible 1. Like the container body 10, the support part 80 is made of a material having a higher melting point than the raw material 50, such as graphite.

[0052] The baffle plate 81 is, for example, disk-shaped and attached to the tip of the support portion 80. The baffle plate 81 is, for example, made of a material having a higher melting point than the growth temperature of SiC, such as graphite, similarly to the support portion 80, and the upper surface 81a opposite to the lower surface 81b is covered with a coating material 82. The support portion 80 is connected to the center of the lower surface 81b on the bottom surface 10b side of the baffle plate 81, and plays a role in suppressing the inclusion of foreign matter from the raw material 50 when the SiC single crystal 60 is grown until it becomes long, that is, until the crystal height becomes large. Specifically, when the crystal height of the SiC single crystal 60 becomes long, the surface 60a of the SiC single crystal 60 approaches the surface 50a of the raw material 50, and there is a risk that carbon inclusions from the raw material 50 will be mixed into the SiC single crystal 60. In this embodiment, the baffle plate 81 is provided in the growth space 11 to block such foreign matter originating from the raw material 50 and suppress its inclusion into the SiC single crystal 60.

[0053] The baffle plate 81 is disposed, for example, in the vicinity of the lower end of the covering member 30. For example, as shown in Fig. 6, when the covering member 30 covers only a part of the inner circumferential surface 70a of the skirt portion 70, the baffle plate 81 is disposed at a position closer to the seed crystal 40 than the large opening of the skirt portion 70. Note that the height position of the baffle plate 81 may be set independently of the range covered by the covering member 30, and not only the upper surface 81a but also the entire area may be covered by the covering material 82.

[0054] The coating material 82 is made of, for example, a metal carbide having a melting point higher than the growth temperature of SiC, similar to the coating member 30. The coating material 82 is made of, for example, a carbide of any one of tantalum, niobium, tungsten, and titanium. The coating material 82 is manufactured, for example, by a method similar to that of the coating member 30, but the same material as that of the coating member 30 may be used, or a different material may be used.

[0055] In addition, when the support portion 80 and the baffle plate 81 are made of graphite, it is optional whether or not to cover the graphite portions of these components other than the upper surface 81a with the covering material 82, and this is unrelated to the coverage rate of the side surface 12 by the covering material 30.

[0056] According to this embodiment, the SiC single crystal manufacturing apparatus includes crucible 1 that can provide the same effects as those of the second embodiment. Moreover, by further including baffle plate 81 whose upper surface 81a is covered with coating material 82, foreign matter originating from raw material 50 is prevented from being mixed into SiC single crystal 60, and the SiC single crystal manufacturing apparatus can manufacture a longer SiC single crystal 60.

[0057] In the SiC single crystal manufacturing apparatus of this embodiment, the crucible 1 of the second embodiment has the support portion 80, the baffle plate 81, and the covering material 82, but is not limited thereto. For example, as shown in Fig. 7, the SiC single crystal manufacturing apparatus of this embodiment may have a configuration in which the crucible 1 of the first embodiment has the support portion 80, the baffle plate 81, and the covering material 82.

[0058] (Other embodiments) Although the present disclosure has been described based on the embodiment, it is understood that the present disclosure is not limited to the embodiment or structure. The present disclosure also includes various modifications and modifications within the equivalent range. In addition, various combinations and forms, and other combinations and forms including only one element, more than one, or less than one, are also within the scope and concept of the present disclosure.

[0059] In each of the above embodiments, it goes without saying that the elements constituting the embodiment are not necessarily essential, except when it is specifically stated that they are essential or when it is clearly considered essential in principle. In addition, in each of the above embodiments, when the numbers, values, amounts, ranges, etc. of the components of the embodiment are mentioned, they are not limited to the specific numbers, except when it is specifically stated that they are essential or when it is clearly limited to a specific number in principle. In addition, in each of the above embodiments, when the shapes, positional relationships, etc. of the components are mentioned, they are not limited to the shapes, positional relationships, etc., except when it is specifically stated that they are essential or when it is clearly limited to a specific shape, positional relationship, etc. in principle.

[0060] (In view of the present disclosure) The present disclosure described above can be understood from the following viewpoints, for example. [First viewpoint] A method for producing a silicon carbide single crystal, comprising the steps of: A hollow cylindrical crucible (1) is prepared, the crucible having a cylindrical container body (10) with a bottom, a lid (20) for closing an opening of the container body, and a covering member (30) made of a metal carbide having a higher melting point than silicon carbide and disposed inside the container body; placing a seed crystal (40) made of a silicon carbide substrate on the lid, placing a silicon carbide raw material (50) in the container body, and then supplying a sublimation gas of the silicon carbide raw material to grow a silicon carbide single crystal (60) on the seed crystal, In preparing the crucible, a space in the crucible from a height position (1A) of a surface (40a) of the seed crystal to a height position (1B) of a surface (50a) of the silicon carbide raw material, in which the sublimation gas is filled, is defined as a growth space (11), a wall surface (10a, 70a) of the growth space is defined as a side surface (12), the covering member is tubular along the side surface, and a predetermined region of the side surface from the height position of the surface of the seed crystal is covered with the covering member. [Second viewpoint] The method for producing a silicon carbide single crystal according to a first aspect, wherein preparing the crucible includes covering at least 5% and at most 80% of an area of ​​the side surface with the covering member. [Third Perspective] The method for producing a silicon carbide single crystal according to a second aspect, wherein preparing the crucible includes covering at least 10% and at most 60% of an area of ​​the side surface with the covering member. [Fourth viewpoint] The method for producing a silicon carbide single crystal according to any one of the first to third aspects, wherein, in growing the silicon carbide single crystal, a height from a surface of the seed crystal to an outermost surface (60a) of the silicon carbide single crystal on the silicon carbide raw material side is defined as a crystal height of the silicon carbide single crystal, and the silicon carbide single crystal is grown such that the crystal height falls within a range of a region of the side surface that is covered by the covering member. [Fifth viewpoint] The method for producing a silicon carbide single crystal according to any one of the first to fourth aspects, further comprising, in preparing the crucible, forming the covering member from a carbide of any one of tantalum, niobium, tungsten, and titanium. [Sixth viewpoint] The method for producing a silicon carbide single crystal according to a fifth aspect, wherein the step of preparing the crucible comprises forming the covering member from tantalum carbide, and setting a C / Ta ratio, which is a ratio of tantalum to carbon, within a range of 0.2 or more and 1 or less. [Seventh viewpoint] The method for producing a silicon carbide single crystal according to a sixth aspect, wherein preparing the crucible includes carbonizing a tantalum member (31), forming the covering member from tantalum carbide, and setting a rate of change in the weight and the dimensions of the tantalum member after the carbonization treatment to be equal to or greater than 1% and equal to or less than 10%, based on the weight and dimensions of the tantalum member before the carbonization treatment. [Eighth viewpoint] The method for producing a silicon carbide single crystal according to any one of the first to seventh aspects, wherein preparing the crucible includes preparing a crucible further having a baffle (81) that is placed in the growth space and has an upper surface (81a) facing the seed crystal that is covered with a covering material (82) made of a carbide having a melting point higher than that of silicon carbide. [Ninth viewpoint] An apparatus for producing silicon carbide single crystals, comprising: A cylindrical container body (10) with a bottom; a lid (20) that closes an opening of the container body and that is a member to which a seed crystal (40) made of a silicon carbide substrate is attached; The present invention relates to a crucible (1) having a covering member (30) made of a metal carbide having a melting point higher than a growth temperature of silicon carbide, a direction from a bottom surface (10b) of the crucible on which a silicon carbide raw material (50) is placed toward the lid is defined as a height direction, a position of a surface (50a) of the silicon carbide raw material in the crucible in the height direction is defined as a raw material height position (1B), a position of a surface (40a) of the seed crystal in the crucible in the height direction is defined as a seed crystal height position (1A), a space in the crucible from the raw material height position to the seed crystal height position and filled with a sublimation gas of the silicon carbide raw material is defined as a growth space (11), and a wall surface (10a, 70a) in the growth space of the crucible is defined as a side surface (12), the covering member is tubular along the side surface and covers a predetermined region of the side surface from the seed crystal height position toward the source material height position. [10th viewpoint] The apparatus for producing a silicon carbide single crystal according to a ninth aspect, wherein the covering member covers an area of ​​not less than 5% and not more than 80% of the side surface. [Eleventh viewpoint] The apparatus for producing silicon carbide single crystal according to the ninth or tenth aspect, wherein the covering member is made of tantalum carbide and has a C / Ta ratio, which is a ratio of tantalum to carbon, in the range of 0.2 or more and 1 or less. [Explanation of symbols]

[0061] Reference Signs List 1...crucible, 10...vessel body, 11...growth space, 12...side surface, 20...lid, 30...covering member, 40...seed crystal, 40a...surface of seed crystal, 50...raw material, 50a...surface of raw material, 60...silicon carbide single crystal, 60a...surface of SiC single crystal, 81...baffle plate, 81a...upper surface, 82...covering material

Claims

1. A method for producing a silicon carbide single crystal, comprising: A hollow cylindrical crucible (1) is provided, the crucible (1) having a cylindrical container body (10) with a bottom, a lid (20) for closing an opening of the container body, and a covering member (30) made of a metal carbide having a melting point higher than the growth temperature of silicon carbide and disposed inside the container body; a seed crystal (40) made of a silicon carbide substrate is placed on the lid, a silicon carbide raw material (50) is placed in the container body, and then a sublimation gas of the silicon carbide raw material is supplied to grow a silicon carbide single crystal (60) on the seed crystal, In preparing the crucible, the method for producing a silicon carbide single crystal includes the steps of: defining a growth space (11) in the crucible from a height position (1A) of a surface (40a) of the seed crystal to a height position (1B) of a surface (50a) of the silicon carbide raw material, the space being filled with the sublimation gas; defining wall surfaces (10a, 70a) of the growth space as side surfaces (12); defining the covering member as a cylindrical shape along the side surfaces; and covering an area of ​​5% to 80% of the side surfaces in a predetermined region of the side surfaces from a height position of the surface of the seed crystal with the covering member.

2. 2. The method for producing a silicon carbide single crystal according to claim 1, wherein preparing the crucible includes covering an area of ​​10% to 60% of the side surface with the covering member.

3. 2. The method for producing a silicon carbide single crystal according to claim 1, wherein, in growing the silicon carbide single crystal, a height from a surface of the seed crystal to an outermost surface (60 a) of the silicon carbide single crystal on the silicon carbide raw material side is defined as a crystal height of the silicon carbide single crystal, and the silicon carbide single crystal is grown so that the crystal height falls within a range of a region of the side surface that is covered by the covering member.

4. A method for producing a silicon carbide single crystal as described in claim 1, wherein preparing the crucible includes providing a skirt portion (70) attached to the container body, having an opening surrounding the surface of the seed crystal, and having a diameter increasing toward the side opposite the seed crystal, and covering only a portion of the inner surface (70a) of the skirt portion with the covering member.

5. A method for manufacturing a silicon carbide single crystal as described in claim 4, wherein the opening of the skirt portion on the seed crystal side is a small opening, the opening on the opposite side to the small opening is a large opening, and the covering member covers only a portion of the inner surface from the end of the small opening toward the large opening.

6. 2. The method for producing a silicon carbide single crystal according to claim 1, wherein the step of preparing the crucible includes forming the covering member from a carbide of any one of tantalum, niobium, tungsten, and titanium.

7. 7. The method for producing a silicon carbide single crystal according to claim 6, wherein preparing the crucible comprises forming the covering member from tantalum carbide, and setting a C / Ta ratio, which is a ratio of tantalum to carbon, within a range of 0.2 or more and 1 or less.

8. 8. The method for producing a silicon carbide single crystal according to claim 7, wherein preparing the crucible comprises carbonizing a tantalum member (31), forming the covering member from tantalum carbide, and setting a rate of change in the weight and the dimensions of the tantalum member after the carbonization treatment to be 1% or more and 10% or less, based on the weight and dimensions of the tantalum member before the carbonization treatment.

9. 9. The method for producing a silicon carbide single crystal according to claim 1, wherein preparing the crucible further comprises preparing a baffle (81) that is placed in the growth space and has an upper surface (81 a) on the seed crystal side that is covered with a covering material (82) made of a carbide having a melting point higher than that of silicon carbide.

10. An apparatus for producing silicon carbide single crystals, comprising: A cylindrical container body (10) with a bottom, a lid (20) that is a member to which a seed crystal (40) made of a silicon carbide substrate is attached and that closes the opening of the container body; a crucible (1) having a covering member (30) made of a metal carbide having a melting point higher than the growth temperature of silicon carbide; The direction from the bottom surface (10b) of the crucible on which the silicon carbide raw material (50) is placed toward the lid is defined as a height direction, the position of the surface (50a) of the silicon carbide raw material in the height direction is defined as a raw material height position (1B), the position of the surface (40a) of the seed crystal placed in the crucible in the height direction is defined as a seed crystal height position (1A), the space in the crucible from the raw material height position to the seed crystal height position and filled with sublimation gas of the silicon carbide raw material is defined as a growth space (11), and the wall surfaces (10a, 70a) in the growth space of the crucible are defined as side surfaces (12), the covering member is cylindrical and conforms to the side surface, covering a predetermined region of the side surface from the seed crystal height position toward the source material height position, the covering member covering an area of ​​5% to 80% of the side surface.

11. 11. The silicon carbide single crystal manufacturing apparatus according to claim 10, wherein the covering member is made of tantalum carbide, and a C / Ta ratio, which is a ratio of tantalum to carbon, is within a range of 0.2 or more and 1 or less.

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