SiC single crystal growth apparatus and SiC crystal growth method

Abstract

Provided are a SiC monocrystal growth device and SiC crystal growth method that enable reduction in variation in temperature distribution in a seed crystal, and deformation of or damage to the seed crystal, and thereby growing a SiC monocrystal having few defects or cracks. A SiC monocrystal growth device (1) comprises: a heating container (10) having, at one portion (e.g., a bottom section (13)) of upper and lower portions of an inner space S delimited by a cylindrical lateral circumferential portion (14), a raw material housing part (12) in which a solid raw material (M(s)) including SiC is housed and having, at the other portion (e.g., a lid section (16)) located opposite the one portion, a base part (17) to which a seed crystal (2) of SiC is attached; and a heating means for heating the solid raw material M((s)). The seed crystal (2) is attached to the base part (17) through a first anisotropic sheet (41) having anisotropic thermal conductivity. The first anisotropic sheet (41) has a great thermal conductivity in an in-plane direction x of the sheet, and a small thermal conductivity in the thickness direction y of the sheet.

Description

[Technical field]

[0001] The present invention relates to a SiC single crystal growth apparatus and a SiC crystal growth method. [Background technology]

[0002] Silicon carbide (SiC) has excellent electrical properties, such as a dielectric breakdown field strength that is about one order of magnitude larger than that of silicon (Si) and a band gap that is about three times larger. In addition, SiC has excellent thermal properties, such as a thermal conductivity that is about three times higher than that of Si. Because of these excellent properties, SiC is expected to be applied to various devices such as power devices, high-frequency devices, and high-temperature operating devices.

[0003] These devices are manufactured by forming an epitaxial layer, which will be the active region of the device, on a SiC single crystal substrate obtained by processing a SiC single crystal ingot, using a method such as chemical vapor deposition (CVD). Among these, the sublimation method is known as a method for manufacturing a SiC single crystal ingot.

[0004] The sublimation method involves placing a seed crystal made of single crystal SiC in a graphite crucible, heating the crucible and the raw material powder (raw material) in the crucible, and supplying the sublimation gas sublimated from the raw material powder (raw material) in the crucible to the seed crystal, thereby growing the seed crystal into a larger single crystal SiC ingot.

[0005] As a crucible for producing a SiC single crystal by such a sublimation method, Patent Document 1 describes a crucible in which a seed crystal is attached to the crucible by adsorbing it to the lid of the crucible. More specifically, Patent Document 1 discloses a crucible in which a through hole is provided in the lid of the crucible, penetrating between the inside and outside of the crucible, and the seed crystal is adsorbed and blocked during crystal growth, and a seed crystal support means is provided below the seed crystal contact surface of the lid, which supports the seed crystal while maintaining a gap from the seed crystal contact surface that allows the seed crystal to be adsorbed to the crucible lid by controlling the pressure between the inside and outside of the crucible.

[0006] Furthermore, as a method for producing a SiC single crystal by a sublimation method, Patent Document 2 describes a method for reducing crystal defects in a SiC single crystal by preventing stress from being applied to the seed crystal. More specifically, Patent Document 2 discloses that a gas flow is directed from below the seed crystal through the periphery of the seed crystal to the center of the space between the ceiling of a heating vessel and the back surface of the seed crystal, thereby promoting gas-phase transport of a gaseous raw material to the seed crystal while preventing the back surface of the seed crystal from contacting the ceiling of the heating vessel. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 5146418 [Patent Document 2] Patent No. 6444890 Summary of the Invention [Problem to be solved by the invention]

[0008] When growing a SiC single crystal, at the contact portion between the seed crystal and the adjacent pedestal, thermal stress and distortion occur in the seed crystal due to the difference in thermal expansion between the seed crystal and the pedestal, resulting in defects and cracks in the growing SiC single crystal. In addition, thermal stress is also generated in the seed crystal due to the variation in temperature distribution of the seed crystal caused by the variation in temperature of the pedestal adjacent to the seed crystal, resulting in defects in the growing SiC single crystal. In this regard, the crucible in Patent Document 1 is said to suppress the occurrence of thermal stress and distortion caused by the difference in thermal expansion between the crucible lid and the seed crystal by adsorbing the seed crystal to the crucible lid and attaching it to the crucible, but at least does not pay attention to the variation in temperature distribution in the seed crystal.

[0009] In addition, in the method of Patent Document 2, a gas flow is passed through the space between the ceiling of the heating container and the back surface of the seed crystal, and the back surface of the seed crystal is raised above the ceiling of the heating container, thereby reducing crystal defects in the SiC single crystal. However, in the method of Patent Document 2, since the seed crystal is not attached to a pedestal or the like, the heat conduction in the surface of the seed crystal (the center and the periphery) is not uniform, and it is difficult to make the crystal growth rate uniform in the center and the periphery. In addition, in the method of Patent Document 2, since the seed crystal is sandwiched and held by the spacer, there is a risk that the seed crystal may be damaged by the clamping force of the spacer. In addition, the center of the seed crystal is bent downward due to gravity, causing defects and cracks in the obtained SiC single crystal.

[0010] An object of the present invention is to provide a SiC single crystal growth apparatus and a SiC crystal growth method that are capable of reducing variation in temperature distribution in a seed crystal and deformation and damage to the seed crystal, thereby growing a SiC single crystal with fewer defects and cracks. [Means for solving the problem]

[0011] The inventors discovered that by attaching a SiC seed crystal to a pedestal via a first anisotropic sheet having thermal conductivity anisotropy such that the thermal conductivity is high in the in-plane direction and low in the thickness direction, heat generated by the growth of the SiC single crystal can be dissipated from the seed crystal to the pedestal via the first anisotropic sheet, and the variation in temperature distribution on the sheet surface of the first anisotropic sheet can be reduced, thereby reducing the variation in temperature distribution inside the seed crystal, and thus completed the present invention.

[0012] That is, the gist of the present invention is as follows. (1) A SiC single crystal growth apparatus comprising: a heating vessel having a raw material storage section for storing a solid raw material made of SiC in one of the upper and lower parts of an internal space defined by a cylindrical side peripheral part, and a pedestal part on which a seed crystal of SiC is attached in the other part located opposite the one part; and heating means for heating the solid raw material, wherein the seed crystal is attached to the pedestal via a first anisotropic sheet having anisotropy in thermal conductivity, the first anisotropic sheet having a large thermal conductivity in the in-plane direction of the sheet and a small thermal conductivity in the thickness direction of the sheet. (2) The SiC single crystal growth apparatus described in (1) above, wherein the first anisotropic sheet has an area larger than that of the seed crystal and the pedestal and is configured to protrude between the seed crystal and the pedestal. (3) The SiC single crystal growth apparatus according to (1) or (2) above, wherein the seed crystal mounting surface of the first anisotropic sheet has an arithmetic mean roughness (Ra) of 1 μm or less. (4) The SiC single crystal growth apparatus according to any one of (1) to (3) above, wherein the first anisotropic sheet has a thickness in the range of 0.04 mm or more and 2 mm or less. (5) The SiC single crystal growth apparatus according to any one of (1) to (4) above, further comprising a guide member located in the internal space between the seed crystal and the raw material storage section and on a side peripheral portion of the heating vessel, the guide member guiding the growth direction of the SiC single crystal growing from the surface of the seed crystal from the side of the side peripheral surface of the SiC single crystal, the surface of the guide member facing the growing SiC single crystal being covered with a second anisotropic sheet having anisotropic thermal conductivity, the second anisotropic sheet having a large thermal conductivity in the in-plane direction of the sheet and a small thermal conductivity in the thickness direction of the sheet. (6) The SiC single crystal growth apparatus according to (5) above, wherein the single crystal facing surface of the second anisotropic sheet has an arithmetic mean roughness (Ra) of 1 μm or less. (7) The SiC single crystal growth apparatus according to (5) or (6) above, wherein the second anisotropic sheet has a thickness in the range of 0.04 mm or more and 2 mm or less. (8) A SiC crystal growth method comprising the step of growing a SiC single crystal using the SiC single crystal growth apparatus described in any one of (1) to (7) above. Effect of the Invention

[0013] According to the present invention, it is possible to provide a SiC single crystal growth apparatus and a SiC crystal growth method that can reduce variation in temperature distribution in a seed crystal and deformation and damage to the seed crystal, thereby enabling the growth of a SiC single crystal with fewer defects and cracks. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram showing the structure of the main components of a SiC single crystal growth apparatus according to a first embodiment of the present invention, in which FIG. 1(a) is a perspective view and FIG. 1(b) is a cross-sectional view taken along imaginary plane P1 in FIG. 1(a), showing a crucible and a heating means separated from each other. [Diagram 2] FIG. 2 is a diagram showing a schematic diagram of the flow of gaseous raw material when growing a SiC single crystal using the SiC single crystal growth apparatus of the first embodiment. [Diagram 3] Figure 3 shows the simulation results of heat transfer from an anisotropic sheet to an adjacent component, with Figure 3(a) showing the case where the anisotropic sheet is 0.04 mm thick, Figure 3(b) showing the case where the anisotropic sheet is 0.1 mm thick, Figure 3(c) showing the case where the anisotropic sheet is 1 mm thick, Figure 3(d) showing the case where the anisotropic sheet is 2 mm thick, and Figure 3(e) showing the case where the anisotropic sheet is 4 mm thick. [Figure 4] FIG. 4 is a graph showing the relationship between the arithmetic mean roughness (Ra) in the first anisotropic sheet and the density of basal plane dislocations in the obtained SiC single crystal, with the arithmetic mean roughness (Ra) [μm] on the horizontal axis and the density of basal plane dislocations [cm-2] on the vertical axis. [Diagram 5] FIG. 5 is a cross-sectional view showing a schematic configuration of a main part of a SiC single crystal growth apparatus according to a second embodiment of the present invention. [Figure 6] FIG. 6 is a cross-sectional view showing a schematic configuration of a main part of a SiC single crystal growth apparatus according to a third embodiment of the present invention. [Figure 7]Figure 7 is a cross-sectional view showing the main structure of a comparative SiC single crystal growth apparatus and a schematic diagram of the growing SiC single crystal, where Figure 7(a) shows the state of the SiC single crystal 50 hours after the start of SiC single crystal growth, and Figure 7(b) shows the state of the SiC single crystal 100 hours after the start of SiC single crystal growth. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Next, SiC single crystal growth apparatuses according to some embodiments of the present invention will be described below.

[0016] First Embodiment Fig. 1 is a diagram showing a schematic structure of a main part of a SiC single crystal growth apparatus of a first embodiment according to the present invention, in which Fig. 1(a) is a perspective view showing a state in which an internal space S of a crucible is seen through, and Fig. 1(b) is a cross-sectional view taken along a virtual plane P1 in Fig. 1(a). Fig. 2 is a diagram showing a schematic flow of gaseous raw material when growing a SiC single crystal using the SiC single crystal growth apparatus of the first embodiment.

[0017] As shown in FIG. 1, a SiC single crystal growth apparatus 1 according to a first embodiment of the present invention has a source material storage section 12 in which a solid source material M(s) made of SiC is stored in one of the upper and lower parts (e.g., bottom part 13) of an internal space S defined by a cylindrical side peripheral part 14, and is equipped with a heating vessel 10 having a pedestal part 17 on which a seed crystal 2 of SiC is attached in the other part (e.g., lid part 16) located opposite the one part, and a heating means 3 for heating the solid source material M(s), where the seed crystal 2 is attached to the pedestal part 17 via a first anisotropic sheet 41 having anisotropy in thermal conductivity, and the first anisotropic sheet 41 has a large thermal conductivity in the in-plane direction x of the sheet and a small thermal conductivity in the thickness direction y of the sheet.

[0018] In this way, by attaching the SiC seed crystal 2 to the pedestal portion 17 via the first anisotropic sheet 41 having anisotropy of thermal conductivity such that the thermal conductivity is large along the in-plane direction x and small along the thickness direction y, the heat conduction along the thickness direction y of the first anisotropic sheet 41 is slowed down and the heat conduction along the in-plane direction x is promoted. Therefore, the first anisotropic sheet 41 can reduce the variation in temperature distribution on the surface of the pedestal portion 17. In addition, since the seed crystal 2 is in contact with the sheet surface of the first anisotropic sheet 41, the heat generated by the growth of the SiC single crystal C can be released from the seed crystal 2 to the pedestal portion 17 via the first anisotropic sheet 41, and since the seed crystal 2 is stably supported, the seed crystal 2 can be made less likely to be deformed or damaged. As a result, while the growth of the SiC single crystal C can be efficiently promoted, it is possible to reduce the occurrence of variations in the temperature distribution in the seed crystal 2 and the resulting thermal stress and distortion in the seed crystal, and furthermore, it is possible to reduce the occurrence of deformation and damage to the seed crystal 2, so that the SiC single crystal C with fewer defects and cracks can be grown.

[0019] The SiC single crystal growth apparatus 1 according to this embodiment includes at least a heating vessel 10 and a heating means 3.

[0020] (About the heating container) Of these, the heating vessel 10 is composed of one or more crucibles 11. In the SiC single crystal growth apparatus 1 of Fig. 1, the heating vessel 10 is composed of a single crucible 11, but the heating vessel 10 may be composed of a plurality of crucibles 11 arranged along a heating means 3 described later (not shown).

[0021] The crucibles 11 constituting the heating vessel 10 each have a cylindrical side peripheral portion 14, and a source material accommodation portion 12 in which a solid source material M(s) made of SiC is accommodated is provided in a portion of an internal space S partitioned and formed by the side peripheral portion 14. Here, the source material accommodation portion 12 is composed of, for example, a bottom portion 13 and a cylindrical side peripheral portion 14 connected to the bottom portion 13. In addition to the source material accommodation portion 12, the crucible 11 also has a base portion 17, and preferably further has a guide member 15 and a lid portion 16.

[0022] Here, the solid source material M(s) is preferably accommodated in a source material accommodation section 12 in either the upper or lower part of the internal space S partitioned by the side peripheral part 14 of the crucible 11. For example, in the SiC single crystal growth apparatus 1 of FIG. 1, the solid source material M(s) is accommodated in the source material accommodation section 12 in the bottom part 13, which is the lower part of the internal space S of the crucible 11. On the other hand, the solid source material M(s) may be accommodated in a source material accommodation section provided in the vicinity of the lid part 16 in the upper part of the internal space S of the crucible 11 in a state of being placed in a dish, container, or the like (not shown).

[0023] The heating vessel 10 has a pedestal 17 on which a SiC seed crystal 2 is placed, on the side of the internal space S not containing the solid source material M(s) among the upper and lower parts of the internal space S partitioned by the side peripheral part 14 of the crucible 11. For example, in the SiC single crystal growth apparatus 1 of FIG. 1, the pedestal 17 is provided on the lid part 16 in the upper part of the internal space S of the crucible 11. By placing the solid source material M(s) and the seed crystal 2 in the same space, that is, the internal space S, in this manner, when the solid source material M(s) is heated by the heating means 3 described later, the gas source material M(g) generated by the sublimation of the solid source material M(s) contained in the source material containing part 12 can reach the seed crystal 2, and as a result, the SiC single crystal C can be grown.

[0024] A SiC seed crystal 2 is attached to the pedestal 17 of the heating vessel 10 via a first anisotropic sheet 41 having anisotropy in thermal conductivity. In this specification, the "thermal conductivity" may refer to the thermal conductivity at a temperature close to the temperature conditions during crystal growth, and as an example, the thermal conductivity at 2200°C.

[0025] Here, the first anisotropic sheet 41 is configured to have a large thermal conductivity in the in-plane direction x and a small thermal conductivity in the thickness direction y. That is, the thermal conductivity in the in-plane direction x is larger than the thermal conductivity in the thickness direction y. This makes the heat conduction along the thickness direction y of the first anisotropic sheet 41 gentler and promotes the heat conduction along the in-plane direction x. As a result, it is possible to reduce the variation in temperature distribution on the sheet surface of the first anisotropic sheet 41, and therefore the variation in temperature distribution in the seed crystal 2 adjacent thereto.

[0026] A carbon material containing carbon fiber or a graphite sheet is preferably used as the anisotropic material constituting the first anisotropic sheet 41. An example of a carbon material containing carbon fiber is a C / C composite material (Carbon Fiber Reinforced Carbon Composite). The graphite sheet may be a thin sheet having a planar arrangement of carbon atoms similar to that of graphite, with the arrangement plane aligned with the surface direction. By using such an anisotropic material, it is possible to impart anisotropy to the thermal conductivity of first anisotropic sheet 41, and to improve the mechanical strength of first anisotropic sheet 41, such as tensile strength and bending strength. Such an anisotropic material can be formed, for example, by arranging a thin carbon felt or graphite sheet along a plane that is the in-plane direction x.

[0027] Here, in the anisotropic material constituting the first anisotropic sheet 41, the ratio of the thermal conductivity in the in-plane direction x to the thermal conductivity in the thickness direction y is preferably 2 or more, and more preferably 10 or more. On the other hand, the upper limit of the ratio of the thermal conductivity in the in-plane direction x to the thermal conductivity in the thickness direction y is not particularly limited, but from the viewpoint of dissipating heat generated by the growth of the SiC single crystal C from the seed crystal 2 to the pedestal portion 17 via the first anisotropic sheet 41, the upper limit may be 1000 times.

[0028] From the viewpoint of reducing the variation in temperature distribution in the seed crystal 2, the area of ​​the first anisotropic sheet 41 is preferably larger than the areas of both the seed crystal 2 and the pedestal portion 17. In particular, the first anisotropic sheet 41 is preferably configured to protrude from between both the seed crystal 2 and the pedestal portion 17. In the SiC single crystal growth apparatus 1 of this embodiment, when the solid source material M(s) is sublimated by heating using the heating means 3 described later to generate the gas source material M(g) and the gas source material M(g) is supplied to the seed crystal 2 to grow the SiC single crystal C, as shown in FIG. 2, the gas source material M(g) also flows into the side of the seed crystal 2, generates the SiC polycrystal C' at the lid portion 16, turns back, and forms a gas flow toward the side of the solid source material M(s). Here, since the first anisotropic sheet 41 protrudes from between the seed crystal 2 and the pedestal portion 17, the protruding portion acts as a baffle plate for trapping excess vapor containing Si species contained in the gaseous raw material M(g). Furthermore, as shown in FIG. 7, damage D3 to the seed crystal 2 caused by the end of the seed crystal 2 sublimating and adhering to the SiC polycrystal C' can be prevented from occurring. Furthermore, since the protruding portion acts as a baffle plate, it is possible to promote the generation of SiC polycrystal C' on the lid portion 16 and stabilize the vapor pressure of the vapor containing Si species in the internal space S, and therefore it is possible to prevent the generation of polycrystal D2 in the SiC single crystal C due to the generation of defects due to silicon droplets in the growing SiC single crystal C, and damage to the heating vessel 10 and the like due to the vapor containing Si species.

[0029] On the other hand, in a comparative SiC single crystal growth apparatus 90 shown in Figures 7(a) and (b), for example, when growing a SiC single crystal C, steam containing excess Si species contained in the gas source M(g) that flows into the side of the seed crystal 2 is not effectively trapped by the first anisotropic sheet 41 that protrudes from the pedestal portion 17, which makes the vapor pressure of the steam containing Si species in the internal space S unstable, resulting in the formation of silicon droplets in the SiC single crystal C and making it easier to generate polycrystals D2.

[0030] The vapor containing Si species includes Si, SiC2 , Si 2 Examples of the vapor include, but are not limited to, vapor of C.

[0031] The thickness of the first anisotropic sheet 41 is preferably 2 mm or less from the viewpoint of releasing the heat generated by the growth of the SiC single crystal C to the pedestal portion 17 and promoting the growth of the SiC single crystal C. FIG. 3 shows the results of a simulation of heat transfer from the anisotropic sheet to an adjacent member, in which FIG. 3(a) shows the case where the thickness of the anisotropic sheet is 0.04 mm, FIG. 3(b) shows the case where the thickness of the anisotropic sheet is 0.1 mm, FIG. 3(c) shows the case where the thickness of the anisotropic sheet is 1 mm, FIG. 3(d) shows the case where the thickness of the anisotropic sheet is 2 mm, and FIG. 3(e) shows the case where the thickness of the anisotropic sheet is 4 mm. The simulation of FIG. 3 predicts the presence or absence of an effect on the temperature of the adjacent member when a part of the surface of the anisotropic sheet is locally cooled, and thus it is possible to predict the presence or absence of heat transfer to the adjacent member. As shown in Figures 3(a) to (d), when the thickness of the anisotropic sheet is 2 mm or less, the temperature of the parts of the adjacent members indicated by the double arrows decreases, and it is thought that heat is easily dissipated from the anisotropic sheets, namely the first anisotropic sheet 41 and the second anisotropic sheet 42, to the adjacent members, namely the base portion 17 and the guide member 15. On the other hand, as shown in Figure 3(e), when the thickness of the anisotropic sheet exceeds 2 mm, no temperature drop is observed in the adjacent components, and it is therefore considered that heat is difficult to dissipate from the anisotropic sheet to the base portion 17 or the guide member 15.

[0032] On the other hand, the lower limit of the thickness of the first anisotropic sheet 41 is preferably 0.04 mm or more from the viewpoint of easy handling as a free-standing film. Note that the first anisotropic sheet 41 is used in a state of being laminated on the base portion 17, and is not limited to the form of a free-standing film, so the thickness may be less than 0.04 mm.

[0033] The first anisotropic sheet 41 may be formed of one anisotropic sheet, or may be formed by stacking a plurality of anisotropic sheets.

[0034] The arithmetic mean roughness (Ra) of the seed crystal mounting surface 41a of the first anisotropic sheet 41, on which the seed crystal 2 is mounted, is preferably 1 μm or less. In this case, the surface of the seed crystal 2 that comes into contact with the first anisotropic sheet 41 is preferably mirror-finished. FIG. 4 is a graph showing the relationship between the arithmetic mean roughness (Ra) of the first anisotropic sheet and the density of basal plane dislocations in the obtained SiC single crystal, with the horizontal axis representing the arithmetic mean roughness (Ra) [μm] and the vertical axis representing the density of basal plane dislocations [cm -2 ] on the vertical axis. The experiment was performed under the same conditions except for the arithmetic mean roughness (Ra) of the anisotropic sheet. As a result, as shown in FIG. 4, when the arithmetic mean roughness (Ra) of the anisotropic sheet is 1 μm or less, the density of basal plane dislocations tends to be smaller than when it exceeds 1 μm. Therefore, by making the arithmetic mean roughness (Ra) of the first anisotropic sheet 41 1 μm or less, the basal plane dislocation density in the obtained SiC single crystal C can be reduced. In addition, by flattening the surfaces of one or both of the first anisotropic sheet 41 and the seed crystal 2, the surface of the seed crystal 2 becomes easily slippery against the seed crystal mounting surface 41a of the first anisotropic sheet 41, and therefore, the thermal stress acting on the seed crystal 2 can be easily alleviated.

[0035] Here, the anisotropic material constituting the first anisotropic sheet 41 may be configured so as to have a large elastic modulus along the in-plane direction x and a small elastic modulus along the thickness direction y. This allows thermal stress caused by a difference in thermal expansion between the seed crystal 2 and the pedestal 17 to be absorbed by deformation along the thickness direction y.

[0036] In addition, in the case of anisotropic materials such as carbon felt and graphite sheets, the higher the elastic modulus of the material, the higher the thermal conductivity of the material.

[0037] The means for attaching the SiC seed crystal 2 to the pedestal portion 17 on which the first anisotropic sheet 41 is provided is not particularly limited, and the attachment can be performed by any known mechanical means.

[0038] On the other hand, the SiC seed crystal 2 attached to the pedestal 17 may be supported at its outer periphery by a plurality of protrusions (not shown) provided from the guide member 15 described later toward the surface of the seed crystal 2. As a result, the seed crystal 2 is sandwiched between the pedestal 17 and the protrusions of the guide member 15, thereby enhancing the contact between the pedestal 17 and the seed crystal 2, and therefore it is possible to promote the dissipation of heat generated by the growth of the SiC single crystal C to the pedestal 17 via the first anisotropic sheet 41 described later. In addition, since one surface of the seed crystal 2 faces the solid source material M(s), it is also possible to reduce the variation in the growth rate of the SiC single crystal C in the in-plane direction x.

[0039] Here, there is no particular limitation on the size of the SiC seed crystal 2. In the SiC single crystal growth apparatus 1 of the present embodiment, even if the area of ​​the growth surface of the seed crystal 2 is large, the first anisotropic sheet 41 can reduce the variation in temperature distribution of the pedestal portion 17, thereby making it difficult for thermal stress or distortion to occur in the seed crystal 2, and therefore it is possible to grow a large-area SiC single crystal C with few defects or cracks.

[0040] The material of the crucible 11 becomes hot when the solid source material M(s) is sublimated to grow the SiC single crystal C, so it is desirable that the crucible 11 is made of a material that can withstand high temperatures. Materials capable of withstanding such high temperatures include graphite, tantalum-coated graphite, and tantalum carbide.

[0041] (About heating method) The heating means 3 heats the solid source material M(s). More specifically, the heating means 3 heats the solid source material M(s) contained in the heating vessel 10, thereby sublimating the solid source material M(s). The gas source material M(g) generated by the sublimation passes through the internal space S defined by the cylindrical side peripheral portion 14 of the crucible 11, reaches the seed crystal 2, and is cooled by the seed crystal 2, thereby allowing the growth of a SiC single crystal C.

[0042] The heating means 3 is configured to heat the solid raw material M(s) accommodated in the raw material accommodation section 12 of the heating container 10. Here, the heating means 3 may be disposed in a positional relationship so as to cover the outer surface of the bottom part 13 of the heating container 10, as shown in Fig. 1. The heating means 3 may also be disposed in a positional relationship so as to cover the outer surface of the side peripheral part 14 of the heating container 10 (not shown).

[0043] Furthermore, the type of heat source constituting the heating means 3 is not particularly limited, and known means such as resistance heating and induction heating can be used.

[0044] (SiC crystal growth method) The SiC crystal growth method of this embodiment includes a step of growing SiC single crystal C using the above-mentioned SiC single crystal growth apparatus. More specifically, in the SiC single crystal growth apparatus 1, a solid source material M(s) is sublimated by heating using a heating means 3 described later to generate a gas source material M(g), and this gas source material M(g) is supplied to a seed crystal 2, thereby growing the SiC single crystal C. Here, the growth conditions of the SiC single crystal C other than the SiC single crystal growth apparatus 1 are not particularly limited, and known SiC crystal growth conditions can be used.

[0045] <Second embodiment> 5 is a cross-sectional view showing a schematic structure of a main part of a SiC single crystal growth apparatus according to a second embodiment of the present invention. In the following description, the same components as those in the first embodiment are given the same reference numerals, and the description thereof is omitted or simplified, and differences are mainly described.

[0046] 1(a) and 1(b), the first anisotropic sheet 41 having anisotropy in thermal conductivity is provided between the pedestal 17 and the seed crystal 2, but the present invention is not limited thereto. In addition to the first anisotropic sheet 41, a sheet made of an anisotropic material may be provided.

[0047] For example, the SiC single crystal growth apparatus 1A shown in FIG. 5 is located in the internal space S between the seed crystal 2 and the raw material storage section 12, and is provided with a guide member 15 on the side peripheral portion of the heating vessel 10, which guides the growth direction of the SiC single crystal C growing from the surface of the seed crystal 2 from the side peripheral surface of the SiC single crystal C.

[0048] Since the SiC single crystal growth apparatus 1A is provided with the guide member 15 on the side peripheral surface side of the SiC single crystal C, the surface of the guide member 15 is heated by heat generated by the growth of the SiC single crystal C, and this makes it difficult for the SiC single crystal C to grow near the surface of the guide member 15, for SiC to precipitate on the surface of the guide member 15, and for the guide member 15 to come into contact with the SiC single crystal C. This makes it possible to guide the growth direction of the SiC single crystal C in a direction along the guide member 15, and makes it possible to prevent a decrease in the effective diameter of the SiC single crystal C due to the precipitated SiC penetrating into the SiC single crystal C, and to prevent defects and cracks due to the SiC single crystal C coming into contact with the guide member 15.

[0049] 5, it is preferable that the surface of guide member 15 facing the growing SiC single crystal C is covered with second anisotropic sheet 42 having anisotropy in thermal conductivity. Since guide member 15 is protected by second anisotropic sheet 42, damage to guide member 15 due to steam containing Si species and contamination (inclusions) D1 of SiC single crystal C caused by such damage are less likely to occur.

[0050] Here, the second anisotropic sheet 42 is configured to have a large thermal conductivity in the in-plane direction and a small thermal conductivity in the thickness direction, similar to the first anisotropic sheet 41. That is, the thermal conductivity in the in-plane direction is larger than the thermal conductivity in the thickness direction. This can reduce the variation in temperature distribution on the sheet surface of the second anisotropic sheet 42, so that even when only a narrow portion of the guide member 15 near the seed crystal 2 is heated, particularly in the early stage of crystal growth, the temperature in a wider range of the guide member 15 can be increased, thereby making it even more difficult for SiC to precipitate on the surface of the guide member 15. In addition, by heating the guide member 15, a portion of the SiC single crystal C that is narrowly spaced from the guide member 15 is sublimated, making it even more difficult for defects and cracks to occur in the SiC single crystal C due to contact with the guide member 15.

[0051] As the anisotropic material constituting the second anisotropic sheet 42, it is preferable to use a carbon material containing carbon fiber, similar to the first anisotropic sheet 41. Such an anisotropic material can be formed, for example, by arranging a thin carbon felt or graphite sheet along a surface that is an in-plane direction. In particular, in the SiC single crystal growth apparatus 1A, by forming the second anisotropic sheet 42 from a thin carbon felt or graphite sheet, it becomes possible to fold the second anisotropic sheet 42, and therefore the second anisotropic sheet 42 can be laminated along the guide member 15.

[0052] Here, in the anisotropic material constituting the second anisotropic sheet 42, the ratio of the thermal conductivity in the in-plane direction to the thermal conductivity in the thickness direction is preferably 2 or more, and more preferably 10 or more. On the other hand, the upper limit of the ratio of the thermal conductivity in the in-plane direction to the thermal conductivity in the thickness direction may be set to 1000. From the viewpoint of reducing the variation in temperature distribution on the surface of the guide member 15, the area of ​​the second anisotropic sheet 42 is larger than the surface area of ​​the guide member 15, and in particular, it is preferable that the second anisotropic sheet 42 covers the entire surface of the guide member 15.

[0053] The arithmetic mean roughness (Ra) of the single crystal facing surface 42a of the second anisotropic sheet 42 facing the grown SiC single crystal C is preferably 1 μm or less. This allows the basal plane dislocation density in the obtained SiC single crystal C to be reduced, similarly to the first anisotropic sheet 41 shown in FIG. 4 above. In addition, since the generation of crystal nuclei on the single crystal facing surface 42a of the second anisotropic sheet 42 is suppressed, the precipitation of SiC on the surface of the second anisotropic sheet 42 is less likely to occur. In addition, since the generation of crystal nuclei in the obtained SiC single crystal C is suppressed, the nuclei growth of polycrystal D2 in the SiC single crystal C is less likely to occur. In addition, even if the grown SiC single crystal C comes into contact with the single crystal facing surface 42a, the surface of the SiC single crystal C becomes more likely to slide against the single crystal facing surface 42a of the second anisotropic sheet 42, and the thermal stress acting on the SiC single crystal C is alleviated, making it less likely that defects or cracks will occur in the SiC single crystal C.

[0054] 3(a) to (d), the thickness of the second anisotropic sheet 42 is preferably 2 mm or less from the viewpoint of promoting heat dissipation to the guide member 15 via the second anisotropic sheet 42. On the other hand, the lower limit of the thickness of the second anisotropic sheet 42 is preferably 0.04 mm or more from the viewpoint of increasing the mechanical strength of the second anisotropic sheet 42 and increasing the temperature uniformity along the in-plane direction of the second anisotropic sheet 42. When the second anisotropic sheet 42 is used in a state where it is laminated on the guide member 15, it is not limited to the form of a free-standing film, and therefore the thickness may be less than 0.04 mm.

[0055] The second anisotropic sheet 42 may be formed of one anisotropic sheet, or may be formed by stacking a plurality of anisotropic sheets.

[0056] <Third embodiment> 6 is a cross-sectional view showing a schematic structure of a main part of a SiC single crystal growth apparatus according to a third embodiment of the present invention. In the following description, the same components as those in the first or second embodiment are given the same reference numerals, and the description thereof is omitted or simplified, and differences are mainly described.

[0057] In the above-mentioned second embodiment, as shown in Fig. 5, the SiC single crystal growth apparatus 1A includes a guide member 15 and a second anisotropic sheet 42 is provided on the surface of the guide member 15. However, the present invention is not limited to this. For example, as in the case of a SiC single crystal growth apparatus 1B shown in Fig. 6, the apparatus may include only the second anisotropic sheet 42 without including the guide member 15. In this case, it is preferable that at least a part of the second anisotropic sheet 42 is supported by a support member 5.

[0058] The thickness of the second anisotropic sheet 42 in the SiC single crystal growth apparatus 1B is preferably 0.1 mm or more from the viewpoint of using the second anisotropic sheet 42 in a self-supporting state. On the other hand, the thickness of the second anisotropic sheet 42 is preferably 2 mm or less from the viewpoint of promoting heat dissipation to the guide member 15 via the second anisotropic sheet 42.

[0059] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and includes all aspects encompassed by the concept of the present invention and the scope of the claims, and can be modified in various ways within the scope of the present invention. EXAMPLES

[0060] Next, in order to clarify the effects of the present invention, examples of the present invention will be described, but the present invention is not limited to these examples.

[0061] [Example 1] In the crucible 11 having a raw material storage section 12 with a cylindrical internal space S of 180 mm in inner diameter and 160 mm in height, the internal space S being formed by a cylindrical side peripheral portion 14, as arranged as shown in FIG. 1, a SiC powder as a solid raw material M(s) was stored at a height of 60 mm from the bottom of the internal space S. Furthermore, in the internal space S above the raw material storage section 12, a tubular guide member 15 having a truncated cone shape with a diameter of 180 mm on the lower side (the raw material storage section 12 side), a diameter of 149 mm on the upper side (the seed crystal 2 side), and a height of 30 mm was provided on the side peripheral portion of the crucible 11. Adjacent to the upper side of this guide member 15, a seed crystal 2 having a diameter of 150 mm and a thickness of 2 mm and fixed to a pedestal portion 17 having a diameter of 150 mm and a thickness of 20 mm with a first anisotropic sheet 41 sandwiched therebetween was placed on the lid portion 16 of the crucible 11. At this time, the internal space S was configured so that the growth surface of the seed crystal 2 was located at a height of 128 mm from the bottom.

[0062] Here, the first anisotropic sheet 41 was made of a graphite sheet, which is an anisotropic material, and had a diameter of 155 mm and a thickness of 0.04 mm, and was configured to protrude concentrically from both the pedestal portion 17 and the seed crystal 2. In this anisotropic material, the thermal conductivity in the in-plane direction x was set to 400 W / mK (2200°C), and the thermal conductivity in the thickness direction y was set to 1.5 W / mK (2200°C). Therefore, the ratio of the thermal conductivity in the thickness direction y to the thermal conductivity in the in-plane direction x was 266 times. On the other hand, the pedestal portion 17 was made of isotropic graphite, and the thermal conductivity was set to 40 W / mK (2200°C).

[0063] The heating vessel 10 consisting of the crucible 11 was placed on a flat heating means 3 having a diameter of 250 mm and equipped with a heat source consisting of a resistance heating means. The solid source material M(s) was heated so that the temperature of the heating vessel 10 was in the range of 2300°C±10°C, and a SiC single crystal C was grown for 50 hours.

[0064] As a result, the density of basal plane dislocations in the obtained SiC single crystal was 1000 cm -2 It was found to be.

[0065] [Example 2] In the arrangement shown in FIG. 5, a second anisotropic sheet 42 was provided on the entire surface of the guide member 15 that faces the growing SiC single crystal C.

[0066] Here, the second anisotropic sheet 42 is made of a stack of graphite sheets, which are anisotropic materials, and has a thickness of 0.1 mm. The thermal conductivity of this anisotropic material in the in-plane direction x is 300 W / mK (2200°C), and the thermal conductivity in the thickness direction y is 1 W / mK (2200°C).

[0067] Other conditions were the same as in Example 1 of the present invention, and SiC single crystal C was grown for 100 hours.

[0068] As a result, the density of basal plane dislocations in the obtained SiC single crystal was 1500 cm -2 It was found to be.

[0069] [Example 3] In the arrangement shown in FIG. 6, without providing a guide member 15, a free-standing second anisotropic sheet 42 having a thickness of 1 mm was provided and fixed to the heating vessel 10 using a support member 5.

[0070] Other conditions were the same as in Example 2 of the present invention, and SiC single crystal C was grown for 100 hours.

[0071] As a result, the density of basal plane dislocations in the obtained SiC single crystal was 1000 cm -2 It was found to be.

[0072] [Comparative Example 1] A comparative SiC single crystal growth apparatus 90 was constructed with the arrangement shown in FIGS. 7(a) and 7(b), but without either the first anisotropic sheet 41 or the second anisotropic sheet 42. The conditions other than the first anisotropic sheet 41 and the second anisotropic sheet 42 were the same as those in the second example of the present invention, and the SiC single crystal C was grown for 100 hours.

[0073] As a result, the density of basal plane dislocations in the obtained SiC single crystal after crystal growth for 50 hours was 10000 cm -2 In addition, the density of basal plane dislocations in the obtained SiC single crystal after crystal growth for 100 hours was found to be 20,000 cm -2 It was found to be.

[0074] From the above, in the SiC single crystal growth apparatuses of Examples 1 to 3 of the present invention, all of them have first anisotropic sheet 41 having anisotropy in thermal conductivity, and the density of basal plane dislocations after crystal growth for 50 to 100 hours is 2000 cm -2 It was found that the following was true.

[0075] Therefore, the SiC single crystal growth apparatuses of Examples 1 to 3 of the present invention were capable of reducing variation in temperature distribution in the seed crystal 2 and deformation and damage to the seed crystal 2, thereby growing a SiC single crystal with fewer defects and cracks.

[0076] In particular, the SiC single crystal C obtained in the SiC single crystal growth apparatus of Inventive Example 3 had a lower density of basal plane dislocations than the SiC single crystal growth apparatus of Inventive Example 2, which was provided with guide member 15. This is believed to be because second anisotropic sheet 42 was no longer restrained by guide member 15, and was thus less affected by the thermal stress of second anisotropic sheet 42.

[0077] On the other hand, the SiC single crystal growth apparatus 90 for comparison in Comparative Example 1 did not include the first anisotropic sheet 41, and therefore the density of basal plane dislocations in the obtained SiC single crystal C was high. In addition, the SiC single crystal after crystal growth for 100 hours had intrusion of polycrystals D2 formed on the surface of the guide member 15, reducing the effective diameter. Furthermore, erosion occurred in a part of the heating vessel 10, and contamination (inclusions) D1 occurred in the SiC single crystal C.

[0078] In particular, the reason why polycrystals D2 were generated in SiC single crystal C in Comparative Example 1 is that steam containing excess Si seeds was not trapped, which resulted in the generation of silicon droplets, which in turn formed polycrystals. In addition, the absence of first anisotropic sheet 41 increased the variation in temperature distribution in seed crystal 2, which in turn increased the density of basal plane dislocations.

[0079] On the other hand, the cause of the contamination (inclusion) D1 in the SiC single crystal C in Comparative Example 1 is believed to be that erosion occurred in a part of the heating container 10, and fine powder resulting from the erosion and originating from the heating container 10 contaminated the SiC single crystal C. [Explanation of symbols]

[0080] 1, 1A, 1B SiC single crystal growth equipment 10 Heating container 11 Crucible 12 Raw material storage section 13 Bottom of raw material storage section 14 Side periphery of raw material storage section 15 Guide member 16 Lid 17 Pedestal 2 (SiC) seed crystal 3 Heating means 41 First anisotropic sheet 42 Second anisotropic sheet 42a Single crystal facing surface of second anisotropic sheet 5 Supporting member 90 Comparative SiC single crystal growth equipment S interior space x is the in-plane direction of the first anisotropic sheet y: thickness direction of the first anisotropic sheet M(s) solid raw material M(g) Gas source D1 Contamination (inclusions) in SiC single crystal D2 Polycrystalline SiC D3 Damage to the end of the seed crystal

Claims

1. a heating vessel having an internal space defined by a cylindrical side peripheral portion, the internal space being divided into upper and lower portions, a raw material storage portion for storing a solid raw material made of SiC in one of the upper and lower portions, and the internal space being divided into upper and lower portions, the internal space being divided into upper and lower portions, and the internal space being divided into upper and lower portions, and the internal space being divided into upper and lower portions, and the internal space being divided into upper and lower portions, A heating means for heating the solid raw material, the seed crystal is attached to the pedestal via a first anisotropic sheet having anisotropy in thermal conductivity; The first anisotropic sheet has a large thermal conductivity in an in-plane direction of the sheet and a small thermal conductivity in a thickness direction of the sheet, A SiC single crystal growth apparatus, wherein the first anisotropic sheet has an area larger than that of the seed crystal and the pedestal and is configured to protrude between the seed crystal and the pedestal.

2. 2. The SiC single crystal growth apparatus according to claim 1, wherein the seed crystal mounting surface of the first anisotropic sheet has an arithmetic mean roughness (Ra) of 1 μm or less.

3. The SiC single crystal growth apparatus according to claim 1 or 2, wherein the first anisotropic sheet has a thickness in the range of 0.04 mm or more and 2 mm or less.

4. a guide member located in the internal space between the seed crystal and the raw material housing portion and in a side peripheral portion of the heating vessel for guiding a growth direction of the SiC single crystal growing from the surface of the seed crystal from a side of a side peripheral surface of the SiC single crystal, the guide member has a surface facing the growing SiC single crystal covered with a second anisotropic sheet having anisotropy in thermal conductivity; 4. The SiC single crystal growth apparatus according to claim 1, wherein the second anisotropic sheet has a large thermal conductivity in an in-plane direction of the sheet and a small thermal conductivity in a thickness direction of the sheet.

5. 5. The SiC single crystal growth apparatus according to claim 4, wherein the single crystal facing surface of the second anisotropic sheet has an arithmetic mean roughness (Ra) of 1 μm or less.

6. The SiC single crystal growth apparatus according to claim 4 or 5, wherein the second anisotropic sheet has a thickness in the range of 0.04 mm or more and 2 mm or less.

7. A heating vessel having a raw material storage section in which a solid raw material made of SiC is stored in one of the upper and lower parts of an internal space defined by a cylindrical peripheral portion, and a pedestal section on which a seed crystal of SiC is attached in the other part located opposite the one part, A heating means for heating the solid raw material, the seed crystal is attached to the pedestal via a first anisotropic sheet having anisotropy in thermal conductivity; The first anisotropic sheet has a large thermal conductivity in an in-plane direction of the sheet and a small thermal conductivity in a thickness direction of the sheet, a guide member located in the internal space between the seed crystal and the raw material housing portion and in a side peripheral portion of the heating vessel for guiding a growth direction of the SiC single crystal growing from the surface of the seed crystal from a side of a side peripheral surface of the SiC single crystal, the guide member has a surface facing the growing SiC single crystal covered with a second anisotropic sheet having anisotropy in thermal conductivity; The second anisotropic sheet has a large thermal conductivity in an in-plane direction of the sheet and a small thermal conductivity in a thickness direction of the sheet.

8. 8. A SiC crystal growth method comprising the step of growing a SiC single crystal using the SiC single crystal growth apparatus according to claim 1.

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