Method for producing silicon carbide single crystal and device for producing silicon carbide single crystal

Abstract

This method for producing a silicon carbide single crystal comprises: preparing a hollow cylindrical crucible (1) comprising a closed-end cylindrical vessel main body (10), a lid (20) for closing an opening of the vessel main body, and a covering member (30) made of a metal carbide having a melting point higher than a silicon carbide growth temperature and provided inside the vessel main body; setting, on the lid, a seed crystal (40) comprising a silicon carbide substrate and placing a silicon carbide raw material (50) in the vessel main body; and thereafter growing a silicon carbide single crystal (60) on the seed crystal by supplying a sublimation gas of the silicon carbide raw material. The crucible is prepared so that, when a space in the crucible which extends from the height position (1A) of the surface (40a) of the seed crystal to the height position (1B) of the surface (50a) of the silicon carbide raw material and which is to be filled with the sublimation gas is referred to as a growth space (11) and when the wall surface (10a, 70a) of the growth space is referred to as a side surface (12), then the covering member has a tubular shape conforming to the side surface and a part of the side surface which is a given region extending from the height position of the surface of the seed crystal is covered with the covering member.

Description

Silicon carbide single crystal manufacturing method and silicon carbide single crystal manufacturing apparatus CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Patent Application No. 2023-159117, filed on September 22, 2023, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a method for producing a silicon carbide (hereinafter referred to as "SiC") single crystal and an apparatus for producing a SiC single crystal.

[0003] A known method for producing a SiC single crystal involves growing a SiC single crystal in a graphite crucible using a heating unit disposed around the crucible's periphery. In this method, a seed crystal is placed in the top of the graphite crucible, and a SiC powder raw material placed in the bottom of the crucible is heated to, for example, 2300°C, thereby sublimating the SiC powder raw material. The sublimated gas is then recrystallized on the seed crystal, which is set at a temperature lower than the raw material temperature. Patent Document 1 proposes a method and apparatus for producing a SiC single crystal of this type.

[0004] Patent No. 4957672

[0005] The SiC single crystal manufacturing apparatus described in Patent Document 1 has a truncated cone-shaped skirt portion 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 member, resulting in a seamless shape and preventing the graphite on the inner wall surface of the skirt portion from being exposed. This prevents carbon from being incorporated into the SiC single crystal grown on the seed crystal due to the graphite in the skirt portion, thereby reducing the crystalline quality of the SiC single crystal and preventing defects from occurring due to seams or gaps in the TaC member. Meanwhile, it has been newly discovered that covering the entire inner wall surface of the crucible containing the SiC powder raw material with a coating material such as TaC, which has a higher melting point than SiC, results in a shortage of carbon atoms and an excess of silicon, which in turn reduces the crystalline quality of the SiC single crystal. Therefore, the inventors investigated locally exposing a portion of the inner wall surface of the crucible that was located far from the seed crystal, and found that repeated production of SiC single crystals would wear out that portion, causing holes to form in the crucible. In this case, problems would arise, such as dust generated by the holes in the crucible being taken in by the SiC single crystal, and gas obtained by sublimation of the SiC powder raw material escaping from the holes to the outside of the crucible.

[0006] The present disclosure relates to a method and apparatus for producing a SiC single crystal that can suppress degradation of the crystal quality of the SiC single crystal due to the incorporation of carbon derived from graphite in the crucible and localized wear of the crucible.

[0007] According to one aspect of the present disclosure, a method for producing a silicon carbide single crystal includes: preparing a hollow, cylindrical crucible having a bottomed, cylindrical container body, a lid body that closes an opening of the container body, and a covering member that is made of a metal carbide having a melting point higher than the growth temperature of silicon carbide and that is placed inside the container body; placing a seed crystal made of a silicon carbide substrate on the lid body, placing a silicon carbide raw material in the container body, and then supplying a sublimation gas of the silicon carbide raw material to grow a silicon carbide single crystal on the seed crystal; in preparing the crucible, the space in the crucible from the height of the surface of the seed crystal to the height of the surface of the silicon carbide raw material is defined as a growth space, the wall surfaces of the growth space are defined as side surfaces, the covering member is tubular along the side surfaces, and a predetermined region of the side surfaces from the height 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 vessel body, a lid, and a covering member, placing a seed crystal in the lid, placing a SiC source material in the vessel body, and then sublimating the SiC source 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 the covering member covers a portion of the side surface of a growth space in the crucible, which is a space from the surface of the seed crystal to the surface of the SiC source material and is filled with a sublimation gas of the SiC source material. The region covered by the covering member is a predetermined region of the side surface extending from the surface of the seed crystal toward the SiC source material. This method for producing a SiC single crystal includes covering the graphite in the side surface of the crucible near the surface of the seed crystal with the covering member, thereby suppressing the incorporation of carbon derived from the graphite into the SiC single crystal. Furthermore, in this method for producing a SiC single crystal, a sufficient area of ​​graphite is exposed in the region of the side surface away from the seed crystal surface, which makes it possible to suppress localized wear and the occurrence of holes in the crucible.

[0009] According to another aspect of the present disclosure, an apparatus for manufacturing silicon carbide single crystals includes a crucible having a cylindrical container body with a bottom, a lid body that is a member to which a seed crystal made of a silicon carbide substrate is attached and that closes the opening of the container body, and a covering member that is made of a metal carbide having a melting point higher than the growth temperature of silicon carbide, wherein a portion of the crucible that is located on the surface of the silicon carbide raw material to be placed is defined as the raw material height position, a portion of the crucible that is located on the surface of the seed crystal to be placed is defined as the seed crystal height position, a space from the raw material height position to the seed crystal height position that is filled with sublimation gas of the silicon carbide raw material is defined as the growth space, and the wall surface of the crucible in the growth space is defined as the side surface, 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 a growth space from the surface of the seed crystal to the surface of the SiC raw material, a predetermined region of the side surface of the crucible exposed to the sublimation gas from the seed crystal surface is covered with a coating member made of a metal carbide having a higher melting point than SiC. In the SiC single crystal manufacturing apparatus, the side surface of the crucible near the seed crystal surface is covered with graphite, thereby preventing carbon derived from the graphite from being incorporated into the SiC single crystal. Furthermore, in the SiC single crystal manufacturing apparatus, the graphite is exposed in a region of the side surface away from the surface of the seed crystal, thereby preventing the sublimation gas of the raw material from becoming excessively silicon, and suppressing localized wear and the occurrence of holes in the crucible.

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

[0012] FIG. 1 is a diagram showing a cross-sectional configuration of a SiC single crystal manufacturing apparatus of a first embodiment; FIG. 2 is a diagram showing the relationship between the coverage rate of a side surface in a growth space by a coating member and the carbon inclusion density in a SiC single crystal; FIG. 3 is a diagram showing a cross-sectional configuration of a SiC single crystal manufacturing apparatus of a second embodiment; FIG. 4 is a perspective view of a skirt portion; FIG. 5 is an explanatory diagram of a carbonization treatment of a coating member that covers the skirt portion; FIG. 6 is a diagram showing a cross-sectional configuration of a SiC single crystal manufacturing apparatus of a third embodiment; and FIG. 7 is a diagram showing a modified example of the SiC single crystal manufacturing apparatus of the third embodiment.

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

[0014] First Embodiment A SiC single crystal manufacturing apparatus according to a first embodiment will be described with reference to the drawings. Fig. 1 shows a seed crystal 40 and a source material 50 placed in a crucible 1, which will be described later, as well as a SiC single crystal 60 grown on the seed crystal 40, although these are not part of the SiC single crystal manufacturing apparatus, in order to make the manufacturing method easier to understand. This also applies to Figs. 3, 6, and 7, which will be described later.

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

[0016] The container body 10 has, for example, a SiC raw material 50, which serves as a supply source of sublimation gas, placed at the inner cylindrical bottom. The raw material 50 is, for example, powdered SiC crystal. The container body 10 has the opening on the lid 20 side facing upward, and the wall surface on which the raw material 50 is placed is the inner wall surface 10a, and a predetermined region from the upper side of the inner wall surface 10a is covered with a covering member 30. In this embodiment, a predetermined region of the inner wall surface 10a of the container body 10 is covered with 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 the other region. When the powdered SiC crystal raw material 50 is sublimated, Si and Si ２Because Si-rich sublimation gases such as C are generated, if the entire side surface 12 described below is covered with the covering member 30, the SiC single crystal may become carbon deficient, resulting in reduced crystal quality. Furthermore, it is difficult to adjust the Si / C ratio in the powdered SiC crystal to prevent the generation of Si-rich sublimation gases. Therefore, by leaving a portion of the inner wall surface 10a of the container body 10 uncovered with the covering member 30, carbon atoms from this portion of the graphite are used for recrystallization of SiC, thereby preventing the deterioration of crystal quality due to Si-rich sublimation gases. For example, the entire region of the inner wall surface 10a below a position a predetermined distance from the surface 40a of the seed crystal 40 toward the source material 50 is left uncovered with the covering member 30, providing a large area, thereby preventing localized wear during the growth process of the SiC single crystal.

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

[0018] The position of the surface 50a of the raw material 50 is taken to be 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 charged into the container body 10. Furthermore, when the raw material 50 is not arranged flat, the position of the surface 50a of the raw material 50 is taken to be the average position in the height direction of the irregularities on the outermost surface of the raw material 50 facing the seed crystal 40, or the average position in the height direction of the portion of the outermost surface that contacts the inner wall surface 10a. Since the seed crystal 40 has a thin and negligible thickness, the region of the lid 20 below the height position of the surface to which the seed crystal 40 is attached may be considered to be the growth space 11. Furthermore, for example, if the region of the container body 10 where the raw material 50 is arranged is considered to be the raw material arrangement region, and a 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 considered to be the growth space 11.

[0019] In this embodiment, side surface 12 is a part of inner wall surface 10a of vessel body 10, and is configured as a portion exposed to the sublimation gas of source 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 source material 50, i.e., the amount. The height dimension of side surface 12 is the dimension of growth space 11, and can be changed appropriately 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 40 a faces away from the lid body 20.

[0021] 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 inner wall surface 10a of vessel body 10 from height position 1A of seed crystal 40. Covering member 30 is provided to prevent graphite from being exposed in the region of inner wall surface 10a of vessel body 10 near seed crystal 40, thereby preventing carbon particles from being taken in by SiC single crystal 60 grown on seed crystal 40 and causing deterioration in the quality of the crystal.

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

[0023] The covering member 30 is made of, for example, any one carbide of tantalum, niobium, tungsten, or titanium. The covering member 30 is attached, for example, to a partial region of the side surface 12 extending from the height position 1A toward the height position 1B, and is tubular along the side surface 12. For example, the covering member 30 defines a covering portion as a portion 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 entire area of ​​the side surface 12 is defined as a covering rate, which is set within a predetermined range described below.

[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 was less than 10%, and reached 100 cm at a coverage 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 reached 100 cm at a coverage of 80%. －３ When the coverage rate exceeds 80%, the density increases dramatically to 1000 cm －３ This result indicates that the crystal quality of SiC single crystal 60 can be ensured favorably by setting the coverage within the range of 5% or more and 80% or less, more preferably 10% or more and 60% or less.

[0025] The carbon inclusion density shown on the vertical axis in Figure 2 was measured by growing SiC single crystal 60 up to the lowest height position on the source material 50 side of the portion of side surface 12 covered with coating member 30, and then removing a 1 mm thick substrate crystal from surface 60a of SiC single crystal 60. The carbon inclusion density in Figure 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 studies by the present inventors, the carbon inclusion density of SiC single crystal 60 was found to be independent of the inner diameter or height of 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 subjected to a heat treatment at 1500°C to 2500°C in an inert atmosphere, for example, an argon atmosphere, for carbonization. For example, the above process can obtain a covering member 30 made of metal carbide. As a result, compared to when a metal carbide coating layer is formed by a film-forming 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 larger, and SiC single crystal 60 can be produced reliably.

[0027] For example, when the covering member 30 is made of tantalum carbide, the C / Ta ratio, which is the ratio of carbon to tantalum, is set to a 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 checking the deformation and damage of the covering member 30 associated with crystal growth. Good crystal growth was possible when the C / Ta ratio was in the range of 0.2 to 1. On the other hand, when the C / Ta ratio was less than 0.2, excessive dimensional change occurred during growth of the SiC single crystal 60, and partial silicidation resulted in a low melting point, which could result in damage to the covering member 30. This result was independent of the coverage rate of the covering member 30.

[0028] For example, when the covering member 30 is made of tantalum carbide and the C / Ta ratio is within a range of 0.2 to 1, the change in size and weight due to the carbonization treatment is 1% to 10% based on the size and weight before the carbonization treatment. Specifically, when the C / Ta ratio is less than 0.2, the change in size and weight of the covering member 30 during the SiC crystal growth process is large, exceeding 10%, resulting in deformation and breakage. On the other hand, when the C / Ta ratio is within a range of 0.2 to 1, the change in size and weight of the covering member 30 occurs in advance during the carbonization process, preventing significant deformation and breakage of the covering member 30 during the SiC crystal growth process. It is preferable that the dimensions of the covering member 30 before the carbonization treatment be determined, taking into account the change in size and weight due to the carbonization treatment, so that the dimensions after the carbonization treatment are approximately the same as the inner diameter of the inner wall surface 10a.

[0029] The C / Ta ratio in 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. Various peaks obtained by this X-ray diffraction measurement are classified into TaC with a NaCl structure, Ta with a trigonal structure, and Ta with a NaCl structure. ３ C ２ , Ta ４ C ３ , hexagonal Ta ２The peak heights of the crystal phases of NaCl, Ta, and body-centered cubic Ta are confirmed, and the proportion of each crystal phase is identified. The carbon ratio in each of the above structures is 1 for TaC of the NaCl structure, 1 for trigonal Ta, and ３ C ２ , Ta ４ C ３ is 0.67 to 0.75, hexagonal Ta ２ C is 0.5, and body-centered cubic Ta is 0. Then, the C / Ta ratio in each growth phase can be identified from the lattice constant of each crystal phase, and the C / Ta ratio in tantalum carbide can be calculated from the overall ratio. For this reason, it is considered sufficient for the average C / Ta ratio throughout the entire region of the coating member 30 to be within the range of 0.2 to 1.

[0030] Furthermore, the SiC single crystal manufacturing apparatus has a heating unit (not shown) arranged 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 for Manufacturing SiC Single Crystal] Next, an example of a method for manufacturing SiC single crystal 60 using the above-described SiC single crystal manufacturing apparatus will be described.

[0033] 1, a crucible 1 having a vessel 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 vessel body 10. The seed crystal 40 is prepared, for example, in the shape 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 an arbitrary heating unit such as a heater whose position is fixed, and the crucible 1 is heated by the radiant heat thereof to a predetermined temperature inside the crucible 1. At this time, for example, the growth space 11 inside the crucible 1 is made into an Ar atmosphere with a pressure of about 100 Pa to 10,000 Pa, the temperature of the raw material 50 is set to about 2,100° C. to 2,400° C., and the temperature of the seed crystal 40 is set to about 2,000° C. to 2,300° C., which is lower than that of the raw material 50.

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

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

[0037] The crucible 1 has a side surface 12 of the growth space 11 covered with a 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 a height position 1A of the seed crystal 40 is covered with the covering member 30 at a coverage rate of 5% to 80%, with graphite exposed in the remainder of the side surface 12. This prevents the graphite on the side surface 12 from being exposed near the seed crystal 40, thereby preventing carbon resulting from the graphite from being mixed into the SiC single crystal 60. Furthermore, because the graphite is exposed from the covering member 30 in a region of the side surface 12 far from the seed crystal 40, it is possible to prevent excess Si in the sublimation gas of the source material 50 and to suppress partial consumption of the graphite on the side surface 12 during the growth process of the SiC single crystal 60.

[0038] According to this embodiment, a SiC single crystal manufacturing apparatus and manufacturing method are provided that can suppress 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 with 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, thereby ensuring good crystal quality. Here, for example, in the enclosed space enclosed by the lid 20 in the crucible 1 before the source material 50 is placed therein, the ratio of the height dimensions of the source material placement region to 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 positioned so that the coverage of the wall surface of the region of the enclosed space extending downward from the end on the lid 20 side to a ratio of β / (α + β) is 5% to 80%, more preferably 10% to 60%.

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

[0041] (3) By forming the covering member 30 from a carbide of any one of tantalum, niobium, tungsten, and titanium, 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 carried out 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 limit the rate of change in size and weight before and after the carbonization process when obtaining the covering member 30 to 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 A SiC single crystal manufacturing apparatus according to a second embodiment will be described with reference to the drawings.

[0044] 3, the SiC single crystal manufacturing apparatus of this embodiment differs from the first embodiment in that the crucible 1 further has a skirt portion 70. This difference will be mainly described in this embodiment.

[0045] In this embodiment, the crucible 1 has, for example, a lid 20 having a cylindrical protrusion 21, a vessel body 10 having a skirt 70 surrounding the seed crystal 40 near the seed crystal 40, and the seed crystal 40 attached to the tip of the protrusion 21. As shown in FIGS. 3 and 4 , the skirt 70 has a truncated cone shape with upper and lower openings, and an inner peripheral surface 70 a is covered by a covering member 30. The skirt 70 has two openings, one with a smaller diameter, located near 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 of the skirt 70 may be referred to as the “small opening,” and the opening with a larger diameter located on the lower bottom surface may be referred to as the “large opening.” The skirt 70 serves to enlarge the diameter of the grown crystal when growing a SiC single crystal 60 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 of the skirt portion 70 and an imaginary line passing through the central axes of the upper and lower openings is set as the inclination angle of the inner peripheral surface 70a, and the inclination angle is, for example, 45° or less.

[0046] The skirt portion 70 is made of, for example, graphite, and has a covering member 30 fixed to its 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 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 31 is deep-drilled to form a shape corresponding to the inner peripheral surface 70a of the skirt portion 70. Next, for example, a portion of the plate 31 is folded by seaming to fix it to a small opening in the skirt portion 70, thereby covering the inner peripheral surface 70a of the skirt portion 70. Next, a graphite member 100 having a shape conforming to the inner peripheral surface 70a of the skirt portion 70 is prepared, and the plate 31 attached to the skirt portion 70 is positioned 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 part or all of the inner circumferential surface 70 a 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 circumferential 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 source material 50, and the inner circumferential surface 70a of the skirt portion 70. The covering member 30 covers a predetermined region of the side surface 12 from height position 1A of the seed crystal 40 to height position 1B on the inner circumferential surface 70a so that the coverage of the side surface 12 is 5% to 80%. The covering member 30 may be disposed so as to cover a portion of the inner circumferential surface 70a, or may be disposed so as to cover the entire inner circumferential surface 70a or a portion of the inner wall surface 10a in addition to the entire inner circumferential surface 70a. The coverage area 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, the SiC single crystal 60 is obtained by growing within the area covered by the covering member 30 , with the lower end of the covering member 30 on the side surface 12 being the upper limit of the crystal height.

[0048] According to this embodiment, the SiC single crystal manufacturing apparatus and manufacturing method can achieve the same effects as those of the first embodiment. Furthermore, the crucible 1 has a skirt portion 70 having a truncated cone shape, and the small opening is aligned with the height position 1A of the seed crystal 40, thereby enabling the SiC single crystal 60 to be grown to a diameter larger than that of the seed crystal 40. While FIG. 3 illustrates an example in which the upper end position of the covering member 30 covering the skirt portion 70 coincides with the height position 1A of the surface 40a of the seed crystal 40, this example is not limiting, and these positions may be approximately aligned. The phrase "approximately aligned" includes not only cases in which the upper end position of the covering member 30 coincides with the height position 1A of the seed crystal 40, but also cases in which the upper end position of the covering member 30 is above or below the height position 1A due to, for example, errors in the dimensions of the skirt portion 70 or in the attachment to the vessel body 10. Furthermore, "substantially coincident" also includes cases where the upper end of covering member 30 is intentionally positioned above or below height position 1A, within a range that does not interfere with the growth of SiC single crystal 60 on surface 40a of seed crystal 40. Therefore, skirt portion 70 may be positioned such that the upper end of the portion covered by covering member 30 coincides with surface 40a of seed crystal 40 in the height direction, may be positioned so as to have a gap between it and surface 40a, or may be positioned so as to overlap with seed crystal 40.

[0049] Third Embodiment A SiC single crystal manufacturing apparatus according to a third embodiment will be described with reference to the drawings.

[0050] 6, the SiC single crystal manufacturing apparatus of this embodiment differs from the first embodiment in that the crucible 1 further includes, in addition to the skirt portion 70, support portions 80 and baffle plates 81 extending from the bottom surface 10b of the vessel body 10. Since the skirt portion 70 is the same as in the second embodiment, the present embodiment will mainly describe the support portions 80 and baffle plates 81.

[0051] The support part 80 has, for example, a cylindrical shape 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, for example, a material having a higher melting point than the raw material 50, such as graphite.

[0052] The baffle 81 has, for example, a disk shape and is attached to the tip of the support column 80. Like the support column 80, the baffle 81 is made of, for example, a material with a melting point higher than the growth temperature of SiC, such as graphite, and its upper surface 81a opposite to its lower surface 81b is covered with a coating material 82. The support column 80 is connected to the center of the lower surface 81b on the bottom surface 10b side of the baffle 81, and the baffle 81 serves to suppress the intrusion of foreign matter from the source material 50 when the SiC single crystal 60 is grown to a long length, i.e., until the crystal height increases. Specifically, when the SiC single crystal 60 increases in length, the surface 60a of the SiC single crystal 60 approaches the surface 50a of the source material 50, which may result in carbon inclusions from the source material 50 being mixed into the SiC single crystal 60. In this embodiment, the baffle 81 is provided in the growth space 11 to block such foreign matter originating from the source material 50 and suppress its intrusion into the SiC single crystal 60.

[0053] The baffle 81 is disposed, for example, near 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 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 81 may be set independently of the range covered by the covering member 30, or the entire area of ​​the baffle 81 may be covered by the covering material 82, not just the upper surface 81a.

[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 by, for example, the same method as the coating member 30, but the same material as the coating member 30 may be used, or a different material may be used.

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

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

[0057] Although the SiC single crystal manufacturing apparatus of this embodiment has been described with reference to an example in which the crucible 1 of the second embodiment has the support members 80, the baffle plates 81, and the covering material 82, the present invention is not limited to this. 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 members 80, the baffle plates 81, and the covering material 82.

[0058] (Other Embodiments) While the present disclosure has been described with reference to examples, it is understood that the present disclosure is not limited to those examples or structures. The present disclosure also encompasses various modifications and modifications within the scope of equivalents. In addition, various combinations and forms, as well as other combinations and forms including only one element, more than one, or less than one, are also within the scope and spirit of the present disclosure.

[0059] It goes without saying that in each of the above embodiments, the elements constituting the embodiments are not necessarily essential unless they are specifically stated as essential or are clearly considered essential in principle. Furthermore, in each of the above embodiments, when numerical values ​​such as the number, values, amounts, and ranges of the components of the embodiments are mentioned, they are not limited to the specific numbers unless they are specifically stated as essential or are clearly limited to a specific number in principle. Furthermore, 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., unless they are specifically stated or are clearly limited to a specific shape, positional relationship, etc. in principle.

[0060] (Aspects of the Present Disclosure) The above-described present disclosure can be understood from the following aspects, for example. [First Aspect] A method for producing a silicon carbide single crystal, comprising: preparing a hollow, cylindrical crucible (1) having a bottomed, cylindrical container body (10), a lid (20) closing an opening of the container body, and a covering member (30) made of a metal carbide having a melting point higher than that of silicon carbide and placed inside the container body; placing a seed crystal (40) made of a silicon carbide substrate in 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; A method for producing a silicon carbide single crystal, wherein, in preparing the crucible, a 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, which is filled with the sublimation gas, is defined as a growth space (11), 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 a height position of the surface of the seed crystal is covered with the covering member. [Second Aspect] The method for producing a silicon carbide single crystal according to the first aspect, wherein, in preparing the crucible, the covering member covers an area of ​​5% to 80% of the side surfaces. [Third Aspect] The method for producing a silicon carbide single crystal according to the second aspect, wherein, in preparing the crucible, the covering member covers an area of ​​10% to 60% of the side surfaces. [Fourth Aspect] 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, the 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 of the silicon carbide single crystal 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 region of the side surface that is covered by the covering member. [Fifth Aspect] The method for producing a silicon carbide single crystal according to any one of the first to fourth aspects, wherein, in providing the crucible, the covering member is made of a carbide of any one of tantalum, niobium, tungsten, and titanium.[Sixth Aspect] The method for producing a silicon carbide single crystal according to the fifth aspect, wherein preparing the crucible includes 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 to 1. [Seventh Aspect] The method for producing a silicon carbide single crystal according to the 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 dimensions of the tantalum member after the carbonization treatment to be 1% to 10%, based on the weight and dimensions of the tantalum member before the carbonization treatment. [Eighth Aspect] The method for producing a silicon carbide single crystal according to any one of the first to seventh aspects, wherein preparing the crucible further comprises preparing a baffle (81) that is placed in the growth space, and whose upper surface (81 a) on the seed crystal side is covered with a covering material (82) made of a carbide having a melting point higher than that of silicon carbide. [Ninth Aspect] An apparatus for producing a silicon carbide single crystal, comprising: a crucible (1) having a bottomed cylindrical vessel body (10), a lid (20) that is a member to which a seed crystal (40) made of a silicon carbide substrate is attached and that closes an opening of the vessel body, and a covering member (30) made of a metal carbide having a melting point higher than the growth temperature of silicon carbide, a height direction of the crucible from a bottom surface (10b) on which a silicon carbide raw material (50) is placed toward the lid, a raw material height position (1B) being the position of a surface (50a) of the silicon carbide raw material in the height direction, a seed crystal height position (1A) being the position of a surface (40a) of the seed crystal placed in the crucible in the height direction, a growth space (11) being the 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, and a side surface (12) being a wall surface (10a, 70a) of the crucible in the growth space, 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.[Tenth Aspect] The silicon carbide single crystal manufacturing apparatus according to the ninth aspect, wherein the covering member covers 5% to 80% of an area of ​​the side surface. [Eleventh Aspect] The silicon carbide single crystal manufacturing apparatus according to the ninth or tenth aspect, wherein the covering member is made of tantalum carbide, and a C / Ta ratio, which is a ratio of tantalum to carbon, is in the range of 0.2 to 1.

Claims

1. A method for producing silicon carbide single crystals, comprising: 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 a metal carbide having a melting point higher than a growth temperature of silicon carbide and disposed inside the container body; disposing a seed crystal (40) made of a silicon carbide substrate in the lid, disposing 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.

2. The method for producing a silicon carbide single crystal according to claim 1, wherein preparing the crucible includes covering 5% to 80% of the area of ​​the side surface with the covering member.

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

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

5. The method for producing silicon carbide single crystals 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.

6. The method for producing silicon carbide single crystals according to claim 5, wherein preparing the crucible includes 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.

7. A method for producing silicon carbide single crystals as set forth in claim 6, wherein preparing the crucible includes carbonizing a tantalum member (31), constructing the covering member from tantalum carbide, and setting a rate of change in the weight and dimensions of the tantalum member after the carbonization treatment to 1% or more and 10% or less based on the weight and dimensions of the tantalum member before the carbonization treatment.

8. A method for producing a silicon carbide single crystal as described in any one of claims 1 to 7, wherein preparing the crucible further includes preparing a baffle (81) that is placed in the growth space and whose upper surface (81a) facing the seed crystal is covered with a covering material (82) made of a carbide having a melting point higher than that of silicon carbide.

9. An apparatus for producing silicon carbide single crystals, comprising: a crucible (1) having a bottomed cylindrical vessel body (10); a lid (20) for closing an opening of the vessel body, the lid being a member to which a seed crystal (40) made of a silicon carbide substrate is attached, and a covering member (30) made of a metal carbide having a melting point higher than the 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 body 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 placed 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 sublimation gas of the silicon carbide raw material is defined as a growth space (11), and a wall surface (10a, 70a) of the crucible in the growth space is defined as 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.

10. The silicon carbide single crystal manufacturing apparatus according to claim 9, wherein the covering member covers an area of ​​5% to 80% of the side surface.

11. The silicon carbide single crystal manufacturing apparatus according to claim 9 or 10, 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.

Images