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 is provided with: a step for preparing a hollow cylindrical crucible (1) having a bottomed cylindrical container main body (10), a lid body (20) for closing the opening of the container main body, and a coating member (30) that is arranged inside the container main body and that is composed of a metal carbide having a melting point higher than the growth temperature of silicon carbide; a silicon carbide single crystal (60) is grown on a seed crystal by disposing a seed crystal (40) comprising a silicon carbide substrate on the lid, disposing a silicon carbide raw material (50) in the container main body, and then supplying a sublimation gas for the silicon carbide raw material. In the preparation of the crucible, a space 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 the crucible and a space filled with sublimation gas are set as a growth space (11), wall surfaces (10a, 70a) of the growth space are set as side surfaces (12), and the coating member is made into a cylindrical shape along the side surfaces. A portion of the side surface, which is defined from the height position of the surface of the seed crystal, is covered with a coating member.

Description

[0001] Cross-reference with related applications 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. Technical Field

[0002] This disclosure relates to a method for manufacturing SiC single crystals and an apparatus for manufacturing SiC single crystals. Background Technology

[0003] Conventionally, a known method for manufacturing SiC single crystals is the sublimation recrystallization method, which involves growing SiC single crystals within a graphite crucible using a heating unit disposed around the periphery of the crucible. In this method, a seed crystal is placed in the upper part of the graphite crucible, and SiC powder material disposed at the bottom of the crucible is heated to, for example, 2300°C, causing the SiC powder material to sublimate. The sublimated gas is then recrystallized on the seed crystal at a temperature set lower than that of the raw material. Patent Document 1 describes a method and apparatus for manufacturing such SiC single crystals.

[0004] Existing technical documents Patent documents Patent Document 1: Japanese Patent No. 4957672 Summary of the Invention

[0005] The SiC single crystal manufacturing apparatus described in Patent Document 1 features a conical trapezoidal skirt extending in a cone shape around the seed crystal, and the entire surface of the skirt is covered by a TaC member made of tantalum carbide (TaC). This TaC member is formed into a cup shape along the inner wall of the skirt by deep drawing a plate-like TaC, resulting in a seamless shape and preventing the graphite on the inner wall of the skirt from becoming exposed. Therefore, the aforementioned SiC single crystal manufacturing apparatus can suppress the reduction in crystal quality of the SiC single crystal caused by carbon from the graphite in the skirt being absorbed into the SiC single crystal grown on the seed crystal, as well as the generation of defects such as seams or cracks caused by the TaC member.

[0006] On the other hand, it has been newly determined that in this SiC single crystal manufacturing apparatus, if the entire inner wall of the crucible containing the SiC powder is covered with a coating material such as TaC, which has a higher melting point than SiC, carbon atoms become insufficient while silicon becomes excessive, resulting in a decrease in the crystal quality of the SiC single crystal. Therefore, the inventors investigated partially exposing a portion of the inner wall of the crucible located away from the seed crystal. The results further clarified that if SiC single crystal manufacturing is repeated, this portion is consumed, creating a hole in the crucible. In this case, undesirable situations arise where dust generated by the hole in the crucible is drawn into the SiC single crystal, or gas obtained from the sublimation of the SiC powder escapes from the hole outside the crucible.

[0007] This disclosure relates to a method and apparatus for manufacturing SiC single crystals that can suppress the reduction in crystal quality of SiC single crystals caused by carbon from graphite sources fed into the crucible and local consumption of the crucible.

[0008] According to one aspect of this disclosure, a method for manufacturing silicon carbide single crystals includes the following steps: preparing a hollow cylindrical crucible having a bottomed cylindrical container body, a lid that closes the opening of the container body, and a covering member, the covering member being made of a metal carbide with a melting point higher than the growth temperature of silicon carbide and disposed inside the container body; and growing silicon carbide single crystals on the seed crystal by placing a seed crystal made of a silicon carbide substrate on the lid, placing silicon carbide raw material in the container body, and supplying sublimation gas of the silicon carbide raw material. In the crucible preparation step, the space in the crucible from the height of the seed crystal surface to the height of the silicon carbide raw material surface, and the space filled with sublimation gas, is defined as a growth space, the wall of the growth space is defined as a side surface, the covering member is made into a cylindrical shape along the side surface, and a predetermined area in the side surface from the height of the seed crystal surface is covered by the covering member.

[0009] Therefore, in the method for manufacturing SiC single crystals, a crucible having a container body, a lid, and a coating member is prepared. A seed crystal is placed on the lid, and SiC raw material is placed in the container body. The SiC raw material is then sublimated to grow a SiC single crystal on the seed crystal. Next, a cylindrical coating member made of a metal carbide with a melting point higher than the growth temperature of SiC is prepared. This coating member covers a portion of the side of the crucible containing the growth space from the surface of the seed crystal to the surface of the SiC raw material, and which is filled with the sublimation gas of the SiC raw material. Furthermore, the area covered by the coating member becomes a defined region on the side facing the SiC raw material from the surface of the seed crystal. Because this method for manufacturing SiC single crystals covers the graphite near the seed crystal surface on the side of the crucible with the coating member, it can suppress the absorption of graphite-derived carbon into the SiC single crystal. Furthermore, because this method exposes a sufficient area of ​​graphite in the side region away from the seed crystal surface, it can suppress localized consumption of the crucible and the formation of openings.

[0010] According to another aspect of this disclosure, an apparatus for manufacturing silicon carbide single crystals includes a crucible having a bottomed cylindrical container body, a lid that closes the opening of the container body, and a coating member made of a metal carbide with a melting point higher than the growth temperature of silicon carbide. The lid is a member for mounting a seed crystal made of a silicon carbide substrate. A portion of the crucible located on the surface of the silicon carbide raw material is defined as the raw material height position, and a portion located on the surface of the seed crystal is defined as the seed crystal height position. The space from the raw material height position to the seed crystal height position, and the space filled with the sublimation gas of the silicon carbide raw material, is defined as the growth space. The wall of the growth space in the crucible is defined as the side surface, and the coating member is cylindrical along the side surface, covering a defined area of ​​the side surface from the seed crystal height position toward the raw material height position.

[0011] Therefore, the SiC single crystal manufacturing apparatus is configured such that, in the growth space within the crucible from the surface of the seed crystal to the surface of the SiC raw material, a predetermined region on the side exposed to the sublimation gas, starting from the seed crystal surface, is covered by a coating member made of a metal carbide with a melting point higher than SiC. Because the graphite near the seed crystal surface on the side of the crucible is covered, the SiC single crystal manufacturing apparatus can suppress the absorption of graphite-derived carbon into the SiC single crystal. Furthermore, because the graphite is exposed in the region on the side away from the seed crystal surface, the SiC single crystal manufacturing apparatus can prevent the sublimation gas of the raw material from becoming excess silicon and suppress localized consumption of the crucible and the formation of openings.

[0012] It should be noted that the parenthetical reference symbols used to annotate each constituent element, etc., represent an example of the correspondence between the constituent element, etc., and the specific constituent elements, etc., described in the embodiments described later. Attached Figure Description

[0013] Figure 1 This is a diagram showing the cross-sectional configuration of the SiC single crystal manufacturing apparatus according to the first embodiment.

[0014] Figure 2 This is a graph showing the relationship between the coverage rate of the lateral components in the growth space and the density of carbon inclusions in the SiC single crystal.

[0015] Figure 3 This is a diagram showing the cross-sectional configuration of the SiC single crystal manufacturing apparatus according to the second embodiment.

[0016] Figure 4 It's a 3D model of the skirt.

[0017] Figure 5 This is an explanatory diagram regarding the carbonization treatment of the covering components that cover the skirt.

[0018] Figure 6 This is a diagram showing the cross-sectional configuration of the SiC single crystal manufacturing apparatus according to the third embodiment.

[0019] Figure 7 This is a diagram showing a modified example of the SiC single crystal manufacturing apparatus according to the third embodiment. Detailed Implementation

[0020] The embodiments of this disclosure will now be described based on the figures. It should be noted that in the various embodiments described below, parts that are the same or equivalent are labeled with the same symbol.

[0021] (First Embodiment) The SiC single crystal manufacturing apparatus of the first embodiment will be described with reference to the accompanying drawings. Figure 1 Although not part of the SiC single crystal manufacturing apparatus, this diagram illustrates, to facilitate understanding of the manufacturing method, a seed crystal 40 and a raw material 50 arranged in the crucible 1 described later, and a SiC single crystal 60 grown on the seed crystal 40. This is relevant to the following description... Figure 3 , Figure 6 , Figure 7 The same applies.

[0022] [Basic Components] SiC single crystal manufacturing equipment, such as Figure 1 As shown, a crucible 1 is constructed having a bottomed cylindrical container body 10, a circular lid 20, and a covering member 30. The crucible 1, for example, has the container body 10 and lid 20 made of graphite and is a hollow cylindrical shape.

[0023] The container body 10 has, for example, SiC raw material 50, disposed at the bottom of the inner cylinder as a supply source for sublimation gas. The raw material 50 is, for example, SiC crystal in powder form. Regarding the container body 10, the opening on the side of the cover 20 is designated as the upper part, and the wall surface on the side where the raw material 50 is disposed is designated as the inner wall surface 10a. A predetermined area of ​​the inner wall surface 10a from the upper side is covered by a covering member 30. In this embodiment of the container body 10, a predetermined area of ​​the inner wall surface 10a from the height of the surface 40a of the seed crystal 40 is covered by the covering member 30, while the remaining areas are exposed. It should be noted that if the powdered SiC crystal raw material 50 is sublimated, excess Si sublimation gas, such as Si or Si2C, will be generated. Therefore, if the entire side surface 12 described later is covered by the covering member 30, the carbon in the SiC single crystal may be insufficient, and the crystal quality may be reduced. Furthermore, it is difficult to adjust the Si / C ratio in powdered SiC crystals to suppress the generation of excess Si sublimation gas. Therefore, by setting a portion of the inner wall surface 10a of the container body 10 to be uncovered by the coating member 30, carbon atoms from that portion of graphite are used for SiC recrystallization, thus suppressing the reduction in crystal quality caused by excess Si sublimation gas. For example, since the entire area below the raw material 50 side of the inner wall surface 10a, located only at a predetermined distance from the surface 40a of the seed crystal 40, is set to be uncovered by the coating member 30, and thus has a wide area, localized consumption during the SiC single crystal growth process can be suppressed.

[0024] For ease of explanation, the following is as follows: Figure 1 As shown, the position of the surface 40a of the seed crystal 40 in the crucible 1 is referred to as "height position 1A", and the position of the surface 50a of the raw material 50 is referred to as "height position 1B". The height position referred to here, for example, is the position along the direction connecting the bottom surface 10b and the opening closed by the cover body 20, which is defined as the height direction relative to the normal direction of the bottom surface 10b inside the crucible 1. Hereinafter, the side of the cover body 20 in the above-mentioned height direction is sometimes referred to as the upper side, and the side of the bottom surface 10b inside the container body 10 is referred to as the lower side. In addition, the space in the crucible 1 from height position 1A to height position 1B, and the space filled with the sublimation gas of the raw material 50, is referred to as the "growth space 11", and the wall facing the growth space 11 is referred to as the "side 12".

[0025] It should be noted that the position of the surface 50a of the raw material 50 is defined as the position of the flat surface, for example, when the surface 50a is flattened by tapping the crucible 1 after the raw material 50 is placed into the container body 10. Furthermore, if the surface 50a of the raw material 50 is not flattened, the position is defined as the average position of the height of the outermost surface of the seed crystal 40 side of the raw material 50, or the average position of the portion of the outermost surface that contacts the inner wall surface 10a in the height direction. Furthermore, since the seed crystal 40 is thin and negligible, the area below the height of the surface of the seed crystal 40 attached to the cover 20 can be considered as the growth space 11. Additionally, for example, if the area in the container body 10 where the raw material 50 is placed is defined as the raw material placement area, and a mark indicating the upper end of the raw material placement area is affixed to the inner wall surface 10a, the area above that mark can also be considered as the growth space 11.

[0026] In this embodiment, the side surface 12 is a part of the inner wall surface 10a of the container body 10, and is composed of the portion exposed to the sublimation gas of the raw material 50. The side surface 12 varies depending on the height, i.e., the weight, of the raw material 50 from the bottom surface 10b, but for example, the dimension in the height direction is set to about 30 mm to 500 mm. The dimension in the height direction of the side surface 12 is the dimension of the growth space 11, which can be appropriately changed according to the desired size and thickness of the SiC single crystal 60.

[0027] The cover 20 is, for example, made into a circular plate shape, 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, set as a SiC substrate and mounted with its surface 40a facing in the opposite direction to the cover 20.

[0028] The coating member 30 is made of a carbide with a melting point higher than the growth temperature of SiC (described later) and covers a predetermined area in the inner wall surface 10a of the container body 10, starting from the height position 1A of the seed crystal 40. The coating member 30 is provided to prevent graphite in the vicinity of the seed crystal 40 in the inner wall surface 10a of the container body 10 from becoming exposed, and thus preventing carbon particles from the graphite from being absorbed into the SiC single crystal 60 grown on the seed crystal 40, resulting in crystal quality deterioration.

[0029] For ease of explanation, the end of the coated member 30 on the seed crystal 40 side will be referred to as the "upper end" and the end on the raw material 50 side as the "lower end". The coated member 30 covers the entire area of ​​the side surface 12 located from the upper end to the lower end of the coated member 30. The upper end of the coated member 30 is, for example, aligned with the height position 1A, i.e., the position of the surface 40a of the seed crystal 40.

[0030] The coated member 30 is made of, for example, a carbide of tantalum, niobium, tungsten, or titanium. The coated member 30 is, for example, mounted in a portion of the side surface 12 from height position 1A toward height position 1B, and is formed into a cylindrical shape along the side surface 12. Regarding the coated member 30, for example, the portion of the side surface 12 covered by the coated member 30 is defined as the covered portion, and the ratio of the area of ​​the covered portion to the area of ​​the entire side surface 12 is defined as the coverage ratio, which is set within a range specified later.

[0031] Specifically, such as Figure 2 As shown, within the coverage range of 10% to 60%, the carbon particle content density, i.e., the carbon inclusion density, mixed into SiC single crystal 60 is 1 cm⁻¹. -3 The crystal quality is good. Furthermore, if the coverage rate falls below 10%, the carbon inclusion density begins to increase, reaching 100 cm⁻¹ at a coverage rate of 5%. -3 If the coverage rate falls below 5%, it will increase dramatically to over 1000 cm. -3 Furthermore, if the coverage exceeds 60%, the density of carbon inclusions begins to increase, reaching 100 cm³ at a coverage of 80%. -3 If the coverage rate exceeds 80%, it will increase dramatically to over 1000 cm. -3 The results indicate that by setting the coverage ratio to a range of 5% or more and 80% or less, more preferably 10% or more and 60% or less, the crystal quality of SiC single crystal 60 can be well ensured.

[0032] It should be noted that, Figure 2 The carbon inclusion density along the longitudinal axis is measured by taking a 1 mm thick substrate crystal from the surface 60a of the SiC single crystal 60 up to the lower limit of the raw material 50 side of the portion of the SiC single crystal 60 covered by the coating member 30. Figure 2 The carbon inclusion density 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 confirmed in a specified area of ​​the substrate crystal. Furthermore, according to the researchers' findings, the carbon inclusion density of the SiC single crystal 60 was obtained independently of the inner diameter and height dimensions of the side 12.

[0033] The coated component 30 is obtained, for example, by preparing a sheet material with a thickness of 0.1 mm to 3 mm made of the aforementioned metal material, processing the sheet material into a shape along the inner wall surface 10a of the container body 10, and then performing a carbonization treatment. For example, a graphite component with a shape along the inner wall surface 10a of the container body 10 is prepared, and carbonized by heating it in an inert atmosphere, such as an argon atmosphere, at a temperature of 1500°C or higher and 2500°C, with the processed sheet material adjacent to the graphite component. For example, through the above-described process, a coated component 30 made of metal carbide is obtained. Thus, compared to the case where a coating layer of metal carbide is formed by film deposition methods such as CVD, even when the diameter of the side surface 12 is, for example, 6 inches or more, a coated component 30 without pinholes or cracks can be formed, and SiC single crystal 60 can be stably manufactured.

[0034] When the coated member 30 is made of tantalum carbide, for example, the carbon-to-tantalum ratio is set as the C / Ta ratio, which is set to a range of 0.2 or more and 1 or less. This is determined by observing the deformation and breakage of the coated member 30 during crystal growth by performing crystal growth on tantalum carbide coated members with C / Ta ratios of 0, 0.2, 0.4, 0.6, 0.8, and 1.0. Good crystal growth can be achieved when the C / Ta ratio is in the range of 0.2 or more and 1 or less. On the other hand, when the C / Ta ratio is less than 0.2, the coated member 30 may break due to excessive dimensional changes during the growth of the SiC single crystal 60 and the partial silicide physicochemical formation resulting in a low melting point. This result is independent of the coverage ratio of the coated member 30.

[0035] It should be noted that when the coated component 30 is, for example, made of tantalum carbide and the C / Ta ratio is 0.2 or more and 1 or less, the rate of change in size and weight caused by the carbonization process is 1% or more and 10% or less, based on the size and weight before carbonization. Specifically, when the C / Ta ratio is less than 0.2, the rate of change in size and weight of the coated component 30 during the SiC crystal growth process exceeds 10%, resulting in deformation and breakage. On the other hand, when the C / Ta ratio is 0.2 or more and 1 or less, since the size and weight change of the coated component 30 is generated in advance during the carbonization process, large deformation and breakage of the coated component 30 during the SiC crystal growth process can be prevented. For example, considering the rate of change in size and weight caused by the carbonization process, the size of the coated component 30 before carbonization is preferably determined in such a way that the size after carbonization is approximately the same as the inner diameter of the inner wall surface 10a.

[0036] Furthermore, the C / Ta ratio in the aforementioned tantalum carbide can be calculated, for example, by the following method. First, the tantalum component after carbonization is powdered, and X-ray diffraction is performed on the resulting powder. For the various peaks obtained by this X-ray diffraction measurement, the peak heights of the respective crystalline phases originating from NaCl-structured TaC, trigonal Ta3C2, Ta4C3, hexagonal Ta2C, and body-centered cubic Ta are confirmed, and the proportion of each crystalline phase is determined. It should be noted that, regarding the carbon ratio in each of the above structures, TaC in the NaCl structure is 1, Ta3C2 and Ta4C3 in the trigonal structure are 0.67 to 0.75, Ta2C in the hexagonal structure is 0.5, and Ta in the body-centered cubic structure is 0. Moreover, the C / Ta ratio in each growth phase can be determined by the lattice constant of each crystalline phase, and the C / Ta ratio in the tantalum carbide can be calculated from the overall proportion. Therefore, it is considered sufficient that the average C / Ta ratio over the entire area of ​​the coated component 30 is set to be within the range of 0.2 or more and 1 or less.

[0037] Furthermore, the SiC single crystal manufacturing apparatus has a heating unit (not shown) arranged to surround the outer periphery of the crucible 1.

[0038] The above describes the configuration of the SiC single crystal manufacturing apparatus described in this embodiment.

[0039] [Methods for manufacturing SiC single crystals] Next, an example of a method for manufacturing SiC single crystal 60 using the SiC single crystal manufacturing apparatus described above will be explained.

[0040] First, for example, Figure 1 As shown, a crucible 1 is prepared having a container body 10, a lid 20, and a covering member 30. A seed crystal 40 is attached to the inner surface of the lid 20, and a raw material 50 is disposed on the bottom surface 10b of the container body 10. The seed crystal 40 is, for example, a seed crystal in the shape of a generally circular plate with a diameter in the range of 150 mm to 220 mm.

[0041] Next, for example, crucible 1 is placed in a heating chamber (not shown), and heated using any heating unit such as a heater with a fixed position. The crucible 1 is heated by its radiant heat, and the temperature inside the crucible 1 is set to a predetermined temperature. At this time, for example, the growth space 11 inside the crucible 1 is set to an Ar atmosphere with a pressure of about 100 Pa to 10000 Pa, the temperature of the raw material 50 is set to about 2100 °C to 2400 °C, and the temperature of the seed crystal 40 is set to about 2000 °C to 2300 °C, which is lower than that of the raw material 50.

[0042] The atmosphere within the chamber is obtained, for example, by allowing inert gases such as Ar to flow in through a gas supply pipe (not shown) and by discharging air through an exhaust pipe (not shown). Furthermore, before raising the temperature of the growth surface (surface 40a) of the seed crystal 40 and the raw material 50 to the target temperature, for example, the atmosphere pressure within the heating chamber is set to near atmospheric pressure to suppress sublimation from the raw material 50; after reaching the target temperature, the atmosphere is set to the aforementioned reduced-pressure atmosphere.

[0043] As described above, the raw material 50 is heated under reduced pressure, causing it to sublimate and generating a sublimation gas. This sublimation gas is supplied to the surface 40a of the seed crystal 40. Thereby, the sublimation gas crystallizes on the surface 40a of the seed crystal 40, and the SiC single crystal 60 grows. Furthermore, nitrogen gas is introduced as needed to control the resistivity of the crystal.

[0044] Furthermore, in crucible 1, the side surface 12 of the growth space 11 is covered by a coating member 30 made of a metal carbide with a melting point higher than the growth temperature of SiC. Additionally, a predetermined region in side surface 12 from the height position 1A of the seed crystal 40 is covered by the coating member 30 with a coverage rate ranging from 5% to 80%, leaving graphite exposed in the remaining portion of side surface 12. Thus, graphite in side surface 12 near the seed crystal 40 is not exposed, suppressing the incorporation of carbon from the graphite into the SiC single crystal 60. Furthermore, since graphite is exposed from the coating member 30 in the region of side surface 12 away from the seed crystal 40, excess Si in the sublimation gas of the raw material 50 is prevented, and partial consumption of graphite in side surface 12 is suppressed during the growth process of the SiC single crystal 60.

[0045] According to this embodiment, an apparatus and method for manufacturing SiC single crystals are provided, capable of suppressing the reduction in crystal quality of SiC single crystal 60 caused by carbon from graphite source introduced into crucible 1 and local consumption of crucible 1.

[0046] (1) By setting the coverage rate of the coating member 30 on the side 12 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 below a specified value, thus ensuring good crystal quality. Here, for example, in the closed space of the crucible 1 before the raw material 50 is placed, the ratio of the dimensions in the height direction of the raw material placement area to the remaining area (corresponding to the growth space 11) in the closed space of the covered body 20 is set to α:β (α and β are arbitrary positive numbers). At this time, the coating member 30 only needs to be arranged such that the wall surface of the area from the end of the covered body 20 side downward to the ratio of β / (α+β) in the closed space has a coverage rate of 5% to 80%, more preferably 10% to 60%.

[0047] (2) By growing the SiC single crystal 60 within the area covered by the coating member 30, the absorption of carbon from the exposed graphite in the side 12 into the SiC single crystal 60 can be suppressed, thus ensuring good crystal quality. In other words, the height from the surface 40a to the surface 60a of the SiC single crystal 60 along the normal direction relative to the surface 40a of the seed crystal 40 is set as the crystal height, and the crystal height of the SiC single crystal 60 can be set within the area covered by the coating member 30.

[0048] (3) The coating component 30 is made of a carbide of any one of tantalum, niobium, tungsten, or titanium, so that the melting point of the coating component 30 exceeds 2500°C. Thus, at the growth temperature of SiC single crystal 60, the coating component 30 can maintain a stable shape and the growth process of SiC single crystal 60 can be carried out stably.

[0049] (4) By using tantalum carbide to form the coated component 30 and setting the C / Ta ratio to a range of 0.2 or more and 1 or less, the rate of change in size and weight before and after the carbide treatment when obtaining the coated component 30 can be suppressed to a range of 1% to 10%. As a result, the coated component 30 can be maintained with a stable shape and size during the SiC crystal growth process.

[0050] (Second Implementation) The SiC single crystal manufacturing apparatus of the second embodiment will be described with reference to the accompanying drawings.

[0051] The SiC single crystal manufacturing apparatus of this embodiment is, for example, as follows: Figure 3 As shown, the crucible 1 further has a skirt 70, which differs from the first embodiment described above. In this embodiment, this difference will be the main focus of the explanation.

[0052] In this embodiment, the crucible 1, for example, has a cylindrical protrusion 21 on the lid 20, and a skirt 70 surrounding the seed crystal 40 near the seed crystal 40 in the container body 10, with the seed crystal 40 attached to the front end of the protrusion 21. The skirt 70 is, for example, as shown in... Figure 3 , Figure 4As shown, the skirt 70 is formed into a conical trapezoidal shape with openings at the top and bottom, and the inner circumferential surface 70a is covered by the covering member 30. The smaller diameter opening in the upper and lower openings of the skirt 70 is positioned near the seed crystal 40. Hereinafter, for ease of explanation, the smaller diameter opening on the upper base of the conical trapezoidal shape in the upper and lower openings of the skirt 70 is sometimes referred to as the "small opening," and the larger diameter opening on the lower base is sometimes referred to as the "large opening." The skirt 70 plays a role in expanding the diameter of the grown crystal 60 when the SiC single crystal 60 is grown on the seed crystal 40, and can be referred to as a growth guide, for example. Regarding the skirt 70, the angle between the imaginary straight line passing through the central axis of the upper and lower openings and the inner circumferential surface 70a is set as the tilt angle of the inner circumferential surface 70a, for example, the tilt angle is 45° or less.

[0053] The skirt 70 is made of graphite, for example, and a covering member 30 is fixed on its inner circumferential surface 70a. The covering member 30, which is mounted on the skirt 70, is manufactured, for example, by a process described below. Figure 5 As shown, a sheet material 31 with a thickness of 0.1 mm to 3 mm, made of a metallic material such as Ta, is prepared. The sheet material 31 is deep-drawn to form a shape corresponding to the inner peripheral surface 70a of the skirt 70. Next, for example, a portion of the sheet material 31 is bent and fixed to a small opening in the skirt 70 by a folding process, thereby making the sheet material 31 cover the inner peripheral surface 70a of the skirt 70. Then, a graphite member 100 having a shape along the inner peripheral surface 70a of the skirt 70 is prepared, and the sheet material 31 mounted on the skirt 70 is positioned adjacent to the graphite member 100. Then, for example, the sheet material 31 is heat-treated in an argon atmosphere at a temperature of 1500°C or higher and 2500°C or lower to carbonize it, producing a metal carbide with a melting point higher than the growth temperature of SiC. Thus, the skirt 70 is configured such that part or all of the inner peripheral surface 70a and the vicinity of the small opening are covered by a coating member 30 of metal carbide.

[0054] In this embodiment, the growth space 11 is surrounded by the inner wall surface 10a of the container body 10 and the inner peripheral surface 70a of the skirt 70. That is, the side surface 12 in this embodiment is formed by the area in the inner wall surface 10a of the container body 10 from the large opening of the skirt 70 to the surface 50a of the raw material 50 and the inner peripheral surface 70a of the skirt 70. The coating member 30 covers a predetermined area in 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 coating member 30 may be configured to cover a portion of the inner peripheral surface 70a, or it may be configured to cover the entire inner peripheral surface 70a or a portion of the inner wall surface 10a in addition to the inner peripheral surface 70a. The coverage range of the side surface 12 using the coating member 30 may be appropriately varied according to the desired crystal height of the SiC single crystal 60. In this embodiment, the SiC single crystal 60 may also have the lower end of the coated member 30 in the side 12 set as the upper limit of the crystal height, which is obtained by growing it within the area covered by the coated member 30.

[0055] According to this embodiment, a SiC single crystal manufacturing apparatus and method are provided that can achieve the same effects as those described in the first embodiment. Furthermore, by having a conical trapezoidal skirt 70 in the crucible 1, with a small opening positioned relative to the height 1A of the seed crystal 40, the SiC single crystal 60 can be grown to a diameter larger than that of the seed crystal 40. It should be noted that in... Figure 3 In this example, an example is shown where the upper end position of the covering member 30 covering the skirt 70 coincides with the height position 1A of the surface 40a of the seed crystal 40. However, this example is not limited to this one, and their positions need only be substantially consistent. "Substantially consistent" includes not only the case where the upper end position of the covering member 30 coincides with the height position 1A of the seed crystal 40, but also, for example, cases where the upper end position of the covering member 30 is above or below the height position 1A due to errors in the size of the skirt 70 or its installation onto the container body 10. Furthermore, "substantially consistent" also includes cases where the covering member 30 is intentionally positioned such that its upper end position is above or below the height position 1A, within a range where there are no obstructions when the SiC single crystal 60 grows on the surface 40a of the seed crystal 40. Therefore, the skirt 70 may also be in any of the following situations: the upper end of the portion covered by the covered member 30 is aligned with the surface 40a of the seed crystal 40 in the height direction; the skirt 70 is arranged with a gap from the surface 40a; or the skirt 70 is arranged to overlap with the seed crystal 40.

[0056] (Third implementation) The SiC single crystal manufacturing apparatus of the third embodiment will be described with reference to the accompanying drawings.

[0057] The SiC single crystal manufacturing apparatus of this embodiment is, for example, as follows: Figure 6 As shown, in addition to the skirt 70, the crucible 1 further has a support portion 80 and a baffle 81 extending from the bottom surface 10b of the container body 10, which differs from the first embodiment described above. Since the skirt 70 is the same as in the second embodiment described above, in this embodiment, the support portion 80 and the baffle 81 will be mainly described.

[0058] The support portion 80 is, for example, made into a cylindrical shape, extending along the central axis of the crucible 1 from the center of the bottom surface 10b of the container body 10 toward the opening. The support portion 80 is, for example, made of a material such as graphite with a higher melting point than the raw material 50, similar to the container body 10.

[0059] The baffle 81 is, for example, made into a circular plate shape and installed at the front end of the support portion 80. The baffle 81, like the support portion 80, is made of a material such as graphite with a melting point higher than the growth temperature of SiC, and its upper surface 81a, opposite to the lower surface 81b, is covered by 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 81. As the SiC single crystal 60 grows to a long strip, i.e., its crystal height increases, it plays a role in suppressing the introduction of foreign matter from the raw material 50. Specifically, when the crystal height of the SiC single crystal 60 becomes long, the surface 60a of the SiC single crystal 60 may become close to the surface 50a of the raw material 50, and carbon inclusions from the raw material 50 may be introduced into the SiC single crystal 60. In this embodiment, a baffle 81 is provided within the growth space 11 to block such foreign matter originating from the raw material 50 and suppress its introduction into the SiC single crystal 60.

[0060] Baffle 81 is, for example, disposed near the lower end of the covered member 30. For example, baffle 81 is as follows: Figure 6 As shown, when the covering member 30 only covers a portion of the inner peripheral surface 70a of the skirt 70, it is positioned closer to the seed crystal 40 than the large opening of the skirt 70. It should be noted that the height position of the baffle 81 can be set independently of the covering range of the covering member 30, or the entire area of ​​it can be covered not only by the upper surface 81a, but also by the covering material 82.

[0061] The coating material 82 is, for example, made of a metal carbide with a melting point higher than the growth temperature of SiC, similar to the coating member 30. The coating material 82 is, for example, made of a carbide of any one of tantalum, niobium, tungsten, or titanium. The coating material 82 can be manufactured, for example, by the same method as the coating member 30, but may use the same material as the coating member 30, or a different material.

[0062] It should be noted that when the support column 80 and the baffle 81 are made of graphite, it is optional whether the graphite portion of these components other than the upper surface 81a is covered with the coating material 82, and it is unrelated to the coverage rate of the coating component 30 on the side 12.

[0063] According to this embodiment, a SiC single crystal manufacturing apparatus is provided with a crucible 1 that achieves the same effect as in the second embodiment described above. Furthermore, by having a baffle 81 whose upper surface 81a is covered by a coating material 82, foreign matter originating from the raw material 50 can be prevented from contaminating the SiC single crystal 60, thus creating a SiC single crystal manufacturing apparatus capable of manufacturing SiC single crystals 60 in longer strips.

[0064] It should be noted that, as the SiC single crystal manufacturing apparatus of this embodiment, the example shown is of the crucible 1 in the second embodiment described above, which has a support 80, a baffle 81, and a coating material 82, but it is not limited to this. For example, Figure 7 As shown, the SiC single crystal manufacturing apparatus of this embodiment can also be configured as the crucible 1 of the first embodiment described above, having a support portion 80, a baffle 81, and a covering material 82.

[0065] (Other implementation methods) This disclosure is based on embodiments, but it is to be understood that this disclosure is not limited to those embodiments or structures. This disclosure also includes various modifications and variations within the same range. Furthermore, various combinations, forms, and even including only one of their elements, as well as other combinations and forms above or below, are also included in the scope and spirit of this disclosure.

[0066] It should be noted that, in the above embodiments, the elements constituting the embodiment are not necessarily essential, except where they are explicitly stated to be particularly necessary or where they are clearly considered essential in principle. Furthermore, in the above embodiments, the number, value, quantity, range, etc., of the constituent elements of the embodiment are mentioned, or where they are explicitly stated to be particularly necessary or where they are clearly limited to a specific number in principle, but are not limited to that specific number. Moreover, in the above embodiments, when the shape, positional relationship, etc., of the constituent elements are mentioned, they are not limited to that shape, positional relationship, etc., except where they are specifically stated or where they are limited to a specific shape, positional relationship in principle.

[0067] (This is the viewpoint of the publication) The above disclosure can be understood, for example, as shown in the following viewpoint.

[0068] [First Opinion] A method for manufacturing silicon carbide single crystals, comprising the following steps: The step of preparing a hollow cylindrical crucible (1) includes a bottomed cylindrical container body (10), a lid (20) that closes the opening of the container body, and a covering member (30) made of a metal carbide with a melting point higher than silicon carbide and disposed inside the container body; and The steps involve placing a seed crystal (40) made of a silicon carbide substrate on the cover, placing a silicon carbide raw material (50) in the container body, and then supplying a sublimation gas to the silicon carbide raw material to grow a silicon carbide single crystal (60) on the seed crystal. In the above-mentioned crucible preparation step, the space in the crucible 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 the space filled with the sublimation gas, is set as a growth space (11). The wall surface (10a, 70a) of the growth space is set as a side surface (12). The coating member is made into a cylindrical shape along the side surface, and a portion of a defined area in the side surface from the height position of the seed crystal is covered by the coating member.

[0069] [Second viewpoint] According to the method for manufacturing silicon carbide single crystals as described in the first viewpoint, the step of preparing the crucible includes: covering an area of ​​5% to 80% of the side surface using the covering member.

[0070] [Third Viewpoint] According to the second viewpoint, the method for manufacturing silicon carbide single crystals includes, in the step of preparing the crucible, covering an area of ​​10% to 60% of the side surface using the covering member.

[0071] [Fourth viewpoint] According to any one of the first to third viewpoints, in the step of growing the silicon carbide single crystal, the height from the surface of the seed crystal to the outermost surface (60a) of the silicon carbide raw material side of the silicon carbide single crystal is set as the crystal height of the silicon carbide single crystal, and the silicon carbide single crystal is grown in such a way that the crystal height is within the range of the area covered by the coating member in the side surface.

[0072] [Fifth viewpoint] The method for manufacturing silicon carbide single crystal according to any one of the first to fourth viewpoints, wherein the step of preparing the crucible includes: forming the coating component from a carbide of any one of tantalum, niobium, tungsten, and titanium.

[0073] [Sixth Viewpoint] According to the fifth point of view, the method for manufacturing silicon carbide single crystals includes, in the step of preparing the crucible, the coating component is made of tantalum carbide, and the ratio of tantalum to carbon, i.e., the C / Ta ratio, is set to be in the range of 0.2 or more and 1 or less.

[0074] [Seventh Viewpoint] According to the method for manufacturing silicon carbide single crystals described in the sixth point of view, the step of preparing the crucible includes: performing a carbonization treatment on a tantalum component (31) to form the coated component from tantalum carbide, and setting the rate of change of the weight and size of the tantalum component after the carbonization treatment to be more than 1% and less than 10%, based on the weight and size of the tantalum component before the carbonization treatment.

[0075] [8th Viewpoint] The method for manufacturing silicon carbide single crystal according to any one of the first to seventh viewpoints, wherein the step of preparing the crucible includes: preparing a crucible further having a baffle (81), the baffle (81) being disposed in the growth space, wherein the upper surface (81a) of the seed side of the baffle (81) is covered by a coating material (82) made of a carbide with a melting point higher than that of silicon carbide.

[0076] [Ninth Viewpoint] An apparatus for manufacturing silicon carbide single crystals. It is a silicon carbide single crystal manufacturing apparatus, comprising a crucible (1), wherein the crucible (1) has: A container body with a bottom cylindrical shape (10); The cover (20), which is a component for mounting a seed crystal (40) made of a silicon carbide substrate, closes the opening of the container body; and The coated component (30) is composed of a metal carbide with a melting point higher than that of silicon carbide and a higher growth temperature. The direction from the bottom surface (10b) of the silicon carbide raw material (50) arranged in the crucible toward the cover is set as the height direction. The position of the surface (50a) of the silicon carbide raw material in the crucible in the height direction is set as the raw material height position (1B). The position of the surface (40a) of the seed crystal arranged in the crucible in the height direction is set as the seed crystal height position (1A). The space in the crucible from the raw material height position to the seed crystal height position and the space filled with the sublimation gas of the silicon carbide raw material is set as the growth space (11). The wall surfaces (10a, 70a) in the growth space in the crucible are set as the side surfaces (12). The aforementioned coating member is cylindrical along the aforementioned side surface, covering a portion of the aforementioned side surface defined from the aforementioned seed height position toward the aforementioned raw material height position.

[0077] [10th Viewpoint] According to the silicon carbide single crystal manufacturing apparatus described in the 9th viewpoint, the aforementioned covering member covers an area of ​​5% to 80% of the aforementioned side surface.

[0078] [11th Viewpoint] According to the silicon carbide single crystal manufacturing apparatus described in viewpoint 9 or 10, the aforementioned coated member is composed of tantalum carbide, wherein the ratio of tantalum to carbon, i.e., the C / Ta ratio, is in the range of 0.2 or more and 1 or less.

Claims

1. A method for manufacturing silicon carbide single crystals, comprising the following steps: The step of preparing a hollow cylindrical crucible (1) includes a bottomed cylindrical container body (10), a lid (20) that closes the opening of the container body, and a covering member (30). The covering member (30) is made of a metal carbide with a melting point higher than the growth temperature of silicon carbide and is disposed inside the container body. The steps involve placing a seed crystal (40) made of a silicon carbide substrate on the cover, placing a silicon carbide raw material (50) in the container body, and then supplying a sublimation gas to the silicon carbide raw material, thereby allowing a silicon carbide single crystal (60) to grow on the seed crystal. In the step of preparing the crucible, the space in the crucible 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 the space filled with the sublimation gas, is set as a growth space (11). The walls (10a, 70a) of the growth space are set as side surfaces (12). The coating member is made into a cylindrical shape along the side surface, and a portion of a defined area in the side surface from the height position of the seed crystal is covered by the coating member.

2. The method for manufacturing silicon carbide single crystals according to claim 1, wherein, The step of preparing the crucible includes: covering an area of ​​more than 5% and less than 80% of the side surface using the covering member.

3. The method for manufacturing silicon carbide single crystals according to claim 2, wherein, The step of preparing the crucible includes: covering an area of ​​more than 10% and less than 60% of the side surface using the covering member.

4. The method for manufacturing silicon carbide single crystals according to claim 1, wherein, In the step of growing the silicon carbide single crystal, the height from the surface of the seed crystal to the outermost surface (60a) of the silicon carbide raw material side of the silicon carbide single crystal is set as the crystal height of the silicon carbide single crystal, and the silicon carbide single crystal is grown in such a way that the crystal height is within the range of the area covered by the coating member in the side.

5. The method for manufacturing silicon carbide single crystals according to claim 1, wherein, The step of preparing the crucible includes: forming the coated component from a carbide of any one of tantalum, niobium, tungsten, and titanium.

6. The method for manufacturing silicon carbide single crystals according to claim 5, wherein, The step of preparing the crucible includes: forming the coated component from tantalum carbide, wherein the ratio of tantalum to carbon, i.e., the C / Ta ratio, is set to be in the range of 0.2 or more and 1 or less.

7. The method for manufacturing silicon carbide single crystals according to claim 6, wherein, The step of preparing the crucible includes: carbonizing the tantalum component (31) to form the coated component from tantalum carbide, and setting the rate of change of the weight and size of the tantalum component after the carbonization process to be more than 1% and less than 10%, based on the weight and size of the tantalum component before the carbonization process.

8. The method for manufacturing silicon carbide single crystals according to any one of claims 1 to 7, wherein, The step of preparing the crucible includes: preparing a crucible further having a baffle (81) disposed in the growth space, wherein the upper surface (81a) of the baffle (81) on the seed side is covered by a coating material (82) made of a carbide with a melting point higher than that of silicon carbide.

9. An apparatus for manufacturing silicon carbide single crystals, comprising a crucible (1), said crucible (1) having: A container body with a bottom cylindrical shape (10); A cover (20), which is a component for mounting a seed crystal (40) made of a silicon carbide substrate, closes the opening of the container body; and The coated component (30) is composed of a metal carbide with a melting point higher than that of silicon carbide and a higher growth temperature. The direction from the bottom surface (10b) of the silicon carbide raw material (50) arranged in the crucible toward the cover is set as the height direction. The position of the surface (50a) of the silicon carbide raw material in the crucible in the height direction is set as the raw material height position (1B). The position of the surface (40a) of the seed crystal arranged in the crucible in the height direction is set as the seed crystal height position (1A). The space in the crucible from the raw material height position to the seed crystal height position and the space filled with the sublimation gas of the silicon carbide raw material is set as the growth space (11). The wall surfaces (10a, 70a) in the growth space in the crucible are set as the side surfaces (12). The coating member is cylindrical along the side surface, covering a defined area on the side surface from the seed height position toward the raw material height position.

10. The apparatus for manufacturing silicon carbide single crystals according to claim 9, wherein, The covering component covers an area of ​​more than 5% and less than 80% of the side surface.

11. The apparatus for manufacturing silicon carbide single crystals according to claim 9 or 10, wherein, The coated component is made of tantalum carbide, and the ratio of tantalum to carbon, i.e., the C / Ta ratio, is in the range of 0.2 or more and 1 or less.

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