SiC single crystal growth apparatus and siC crystal growth method

Abstract

The present application provides a SiC single crystal growth device and a SiC crystal growth method, which can reduce the deviation of temperature distribution of the seed crystal, the deformation of the seed crystal, damage, thereby growing a SiC single crystal with less defects and cracks. The SiC single crystal growth device (1) comprises: a heating container (10) having a raw material receiving portion (12) for receiving a solid raw material (M(s)) composed of SiC in any one portion (for example, a bottom portion (13)) of an internal space (S) divided by a cylindrical side peripheral portion (14), and a base portion (17) for mounting a seed crystal (2) of SiC in another portion (for example, a cover portion (16)) located opposite to the one portion; and a heating member (3) for heating the solid raw material (M(s)), the seed crystal (2) is mounted to the base portion (17) through a first anisotropic sheet (41) having anisotropy of thermal conductivity, and for the first anisotropic sheet (41), the thermal conductivity in the in-plane direction (x) of the sheet is larger, and the thermal conductivity in the thickness direction (y) of the sheet is smaller.

Description

Technical Field

[0001] This invention relates to a SiC single crystal growth apparatus and a SiC crystal growth method. Background Technology

[0002] Silicon carbide (SiC) possesses superior electrical properties, including an insulation breakdown electric field strength approximately ten times greater and a band gap about three times larger than that of silicon (Si). Furthermore, SiC exhibits excellent thermal properties, with a thermal conductivity approximately three times higher than that of Si. Due to these superior properties, SiC is expected to be used in various devices, including power devices, high-frequency devices, and high-temperature actuators.

[0003] These devices are fabricated as follows: an epitaxial layer, which becomes the active region of the device, is formed on a SiC single-crystal substrate obtained from a SiC single-crystal ingot using a method such as chemical vapor deposition (CVD). Sublimation is a known method for fabricating SiC single-crystal ingots.

[0004] The sublimation method is as follows: a seed crystal composed of SiC single crystals is placed in a graphite crucible, and sublimation gas, which is generated by heating the crucible and the raw material powder (raw material) inside the crucible and causing it to sublimate, is supplied to the seed crystal, thereby causing the seed crystal to grow into a larger SiC single crystal block.

[0005] As a crucible for manufacturing SiC single crystals using such a sublimation method, Patent Document 1 describes a crucible that is mounted on the crucible by adsorbing a seed crystal onto the lid. More specifically, Patent Document 1 discloses a crucible in which a through-hole is provided in the lid, penetrating between the interior and exterior of the crucible, and a seed support member is provided below the seed contact surface of the lid. This seed support member supports the seed crystal by maintaining a gap between itself and the seed contact surface, and this gap is such that the seed crystal can be adsorbed onto the lid by pressure control between the interior and exterior of the crucible.

[0006] Furthermore, as a method for manufacturing SiC single crystals using the sublimation method, Patent Document 2 describes a method to reduce crystallization defects in SiC single crystals by not applying stress to the seed crystal. More specifically, Patent Document 2 discloses a method in which gas flow is directed from below the seed crystal, past the periphery of the seed crystal, toward the center of the space between the top plate of the heating container and the back surface of the seed crystal, thereby preventing the back surface of the seed crystal from contacting the top plate of the heating container while promoting the gaseous transport of the gaseous feedstock to the seed crystal.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent No. 5146418

[0010] Patent Document 2: Japanese Patent No. 6444890 Summary of the Invention

[0011] The problem the invention aims to solve

[0012] During the growth of SiC single crystals, thermal stress and strain are generated in the seed crystal at the contact point between the seed crystal and the adjacent base due to the difference in thermal expansion between the seed crystal and the base. This results in defects and cracks in the grown SiC single crystal. Furthermore, even if the temperature distribution of the seed crystal deviates due to temperature deviations in the base adjacent to the seed crystal, thermal stress will still be generated in the seed crystal, resulting in defects in the grown SiC single crystal. Regarding this, in the crucible of Patent Document 1, the seed crystal is mounted on the crucible by adsorbing it onto the crucible lid, thereby suppressing the generation of thermal stress and strain caused by the difference in thermal expansion between the crucible lid and the seed crystal, but at least the deviation in the temperature distribution of the seed crystal is not addressed.

[0013] Furthermore, in the method of Patent Document 2, by introducing airflow into the space between the top plate of the heating container and the back side of the seed crystal, the back side of the seed crystal is suspended from the top plate of the heating container, thereby reducing crystallization defects in the SiC single crystal. However, in the method of Patent Document 2, since the seed crystal is not mounted on a base or the like, the in-plane heat conduction (central and peripheral portions) of the seed crystal is uneven, making it difficult to achieve a uniform crystal growth rate in the central and peripheral portions. Furthermore, in the method of Patent Document 2, since the seed crystal is held in place by a spacer, the clamping force of the spacer may cause damage to the seed crystal. Additionally, since the central portion of the seed crystal flexes downwards under gravity, defects and cracks are generated in the resulting SiC single crystal.

[0014] The purpose of this invention is to provide a SiC single crystal growth apparatus and a SiC crystal growth method that can reduce the deviation of the temperature distribution of the seed crystal, the deformation and damage of the seed crystal, thereby enabling the growth of SiC single crystals with fewer defects and cracks.

[0015] Solution for solving the problem

[0016] The inventors of this application discovered that by mounting a SiC seed crystal on a base portion with a first anisotropic sheet having a higher thermal conductivity in the in-plane direction and a lower thermal conductivity in the thickness direction, the heat generated by the growth of the SiC single crystal is discharged from the seed crystal to the base portion via the first anisotropic sheet. Furthermore, by reducing the temperature distribution deviation on the surface of the first anisotropic sheet, the temperature distribution deviation inside the seed crystal can also be reduced, thus completing the present invention.

[0017] That is, the main structure of the present invention is as follows.

[0018] (1) A SiC single crystal growth apparatus, comprising: a heating container having a material receiving portion for receiving a solid material made of SiC in one of the upper and lower portions of an internal space divided by a cylindrical side periphery, and a base portion for mounting a SiC seed crystal in another portion located opposite to the first portion; and a heating member for heating the solid material, wherein the seed crystal is mounted on the base portion with respect to a first anisotropic sheet having a thermal conductivity, wherein the first anisotropic sheet has a larger thermal conductivity in the in-plane direction and a smaller thermal conductivity in the thickness direction.

[0019] (2) The SiC single crystal growth apparatus according to (1) above, wherein the first anisotropic sheet is configured to have a larger area than the seed crystal and the base portion, and extends from between the seed crystal and the base portion.

[0020] (3) The SiC single crystal growth apparatus according to (1) or (2) above, wherein the arithmetic mean roughness (Ra) of the seed mounting surface of the first anisotropic sheet is less than 1 μm.

[0021] (4) The SiC single crystal growth apparatus according to any one of (1) to (3) above, wherein the thickness of the first anisotropic sheet is in the range of 0.04 mm or more and 2 mm or less.

[0022] (5) The SiC single crystal growth apparatus according to any one of (1) to (4) above, wherein the SiC single crystal growth apparatus further comprises a guiding member located in the space between the seed crystal and the raw material receiving portion in the internal space and located in the side peripheral portion of the heating container, guiding the growth direction of the SiC single crystal grown from the surface of the seed crystal from the side peripheral surface of the SiC single crystal, wherein the surface of the guiding member opposite to the grown SiC single crystal is covered by a second anisotropic sheet having anisotropic thermal conductivity, wherein the thermal conductivity of the second anisotropic sheet is larger in the in-plane direction and smaller in the thickness direction of the sheet.

[0023] (6) The SiC single crystal growth apparatus according to (5) above, wherein the arithmetic mean roughness (Ra) of the single crystal opposite surfaces of the second anisotropic sheet is less than 1 μm.

[0024] (7) The SiC single crystal growth apparatus according to (5) or (6) above, wherein the thickness of the second anisotropic sheet is in the range of 0.04 mm or more and 2 mm or less.

[0025] (8) A method for growing SiC crystals, comprising the step of growing SiC single crystals using the SiC single crystal growth apparatus described in any one of (1) to (7) above.

[0026] The effects of the invention

[0027] According to the present invention, a SiC single crystal growth apparatus and a SiC crystal growth method are provided that can reduce the deviation of the temperature distribution of the seed crystal, the deformation and damage of the seed crystal, thereby enabling the growth of SiC single crystals with fewer defects and cracks. Attached Figure Description

[0028] Figure 1 This is a schematic diagram showing the main structural components of the SiC single crystal growth apparatus according to the first embodiment of the present invention. Figure 1 (a) is a 3D diagram; in addition, Figure 1 (b) is Figure 1 A cross-sectional view at the imaginary plane P1 in (a), showing the state in which the crucible and heating element are separated.

[0029] Figure 2 This diagram schematically illustrates the flow of gaseous raw materials during SiC single crystal growth using the SiC single crystal growth apparatus of the first embodiment.

[0030] Figure 3 This is a graph showing the simulation results of heat conduction from the anisotropic sheet to adjacent components. Figure 3 (a) represents the case where the thickness of the anisotropic sheet is 0.04 mm. Figure 3 (b) represents the case where the thickness of the anisotropic sheet is 0.1 mm. Figure 3 (c) represents the case where the thickness of the anisotropic sheet is 1 mm. Figure 3 (d) indicates the case where the thickness of the anisotropic sheet is 2 mm. Figure 3 (e) indicates the case where the thickness of the anisotropic sheet is 4 mm.

[0031] Figure 4This is a graph showing the relationship between the arithmetic mean roughness (Ra) of the first anisotropic sheet and the density of dislocations on the substrate surface of the obtained SiC single crystal. The arithmetic mean roughness (Ra) [μm] is set as the horizontal axis, and the density of dislocations on the substrate surface [cm] is set as the horizontal axis. -2 Set as the vertical axis.

[0032] Figure 5 This is a cross-sectional view schematically showing the main structure of the SiC single crystal growth apparatus according to the second embodiment of the present invention.

[0033] Figure 6 This is a cross-sectional view schematically showing the main structure of the SiC single crystal growth apparatus according to the third embodiment of the present invention.

[0034] Figure 7 This is a schematic cross-sectional view showing the main structure of the SiC single crystal growth apparatus used for comparison and the grown SiC single crystal. Figure 7 (a) represents the state of the SiC single crystal 50 hours after the start of SiC single crystal growth. Figure 7 (b) represents the state of the SiC single crystal 100 hours after the start of SiC single crystal growth. Detailed Implementation

[0035] Next, the SiC single crystal growth apparatus of several embodiments of the present invention will be described.

[0036] <First Embodiment>

[0037] Figure 1 This is a schematic diagram showing the main structural components of the SiC single crystal growth apparatus according to the first embodiment of the present invention. Figure 1 (a) is a three-dimensional view, representing the state of the internal space S of the crucible through perspective. Furthermore, Figure 1 (b) is Figure 1 A cross-sectional view at the imaginary plane P1 in (a). Furthermore, Figure 2 This diagram schematically illustrates the flow of gaseous raw materials during SiC single crystal growth using the SiC single crystal growth apparatus of the first embodiment.

[0038] like Figure 1As shown, the SiC single crystal growth apparatus 1 of the first embodiment of the present invention includes: a heating container 10, which has a raw material receiving portion 12 for receiving a solid raw material M(s) made of SiC in one of the upper and lower portions (e.g., bottom 13) of the internal space S formed by the cylindrical side peripheral portion 14, and a base portion 17 for mounting a seed crystal 2 of SiC in another portion (e.g., cover portion 16) located opposite to the first portion; and a heating member 3 for heating the solid raw material M(s), wherein the seed crystal 2 is mounted on the base portion 17 with the first anisotropic sheet 41 having anisotropic thermal conductivity, wherein the first anisotropic sheet 41 has a larger thermal conductivity in the in-plane direction x and a smaller thermal conductivity in the thickness direction y.

[0039] By mounting the SiC seed crystal 2 onto the base portion 17 via a first anisotropic sheet 41, which has a higher thermal conductivity along the in-plane direction x and a lower thermal conductivity along the thickness direction y, heat conduction along the thickness direction y of the first anisotropic sheet 41 is slowed down, while heat conduction along the in-plane direction x is promoted. Therefore, the first anisotropic sheet 41 can mitigate the temperature distribution deviation on the surface of the base portion 17. Simultaneously, by having the seed crystal 2 in contact with the sheet surface of the first anisotropic sheet 41, heat generated by the growth of the SiC single crystal C can be dissipated from the seed crystal 2 through the first anisotropic sheet 41 to the base portion 17, and by stably supporting the seed crystal 2, deformation and damage to the seed crystal 2 are less likely to occur. The result is that while efficiently promoting the growth of SiC single crystal C, it is not easy to cause deviations in the temperature distribution of the seed crystal 2, resulting in thermal stress and strain on the seed crystal, and thus it is not easy to cause deformation and damage to the seed crystal 2. Therefore, it is possible to grow SiC single crystal C with fewer defects and cracks.

[0040] The SiC single crystal growth apparatus 1 of this embodiment includes at least a heating container 10 and a heating component 3.

[0041] (Regarding heated containers)

[0042] The heating container 10 is composed of one or more crucibles 11. Figure 1 In the SiC single crystal growth apparatus 1, a single crucible 11 constitutes the heating container 10, but multiple crucibles 11 can also be arranged along the heating component 3 described later to constitute the heating container 10 (not shown).

[0043] The crucible 11 constituting the heating container 10 has a raw material receiving section 12, which has cylindrical side peripheral portions 14. A portion of the internal space S formed by the side peripheral portions 14 is used to receive solid raw material M(s) made of SiC. Here, the raw material receiving section 12 includes, for example, a bottom 13 and cylindrical side peripheral portions 14 connected to the bottom 13. Furthermore, it is preferable that the crucible 11, in addition to the raw material receiving section 12, also includes a base portion 17, a guide member 15, and a cover portion 16.

[0044] Preferably, the solid raw material M(s) is housed in the raw material housing section 12, which is located in either the upper or lower portion of the internal space S formed by the side peripheral portion 14 of the crucible 11. For example, in Figure 1 In the SiC single crystal growth apparatus 1, the solid raw material M(s) is stored in the raw material storage section 12 located at the bottom 13 of the lower part of the internal space S of the crucible 11. Alternatively, the solid raw material M(s) may also be stored in the raw material storage section in the form of a plate or container, which is located near the cover 16 (not shown) of the upper part of the internal space S of the crucible 11.

[0045] The heating container 10 has a base portion 17 for arranging SiC seed crystals 2 on one side of the internal space S that does not contain solid raw material M(s) within the upper and lower portions of the internal space S formed by the side peripheral portion 14 of the crucible 11. For example, in Figure 1 In the SiC single crystal growth apparatus 1, the base portion 17 is provided on the cover portion 16 located on the upper side of the internal space S of the crucible 11. By arranging the solid raw material M(s) and the seed crystal 2 in the same internal space S, when the solid raw material M(s) is heated by the heating element 3 (described later), the gaseous raw material M(g) generated by the sublimation of the solid raw material M(s) housed in the raw material housing portion 12 can reach the seed crystal 2, thereby enabling SiC single crystal growth.

[0046] The SiC seed crystal 2 is mounted on the base portion 17 of the heating container 10 via a first anisotropic sheet 41 having a thermal conductivity. The "thermal conductivity" in this specification can be set to the thermal conductivity at a temperature close to the temperature conditions during crystal growth, and as an example, it can be set to a thermal conductivity of 2200°C.

[0047] Here, the first anisotropic sheet 41 is configured such that its thermal conductivity is higher in the in-plane direction x and lower in the thickness direction y. That is, the thermal conductivity in the in-plane direction x is greater than that in the thickness direction y. As a result, heat conduction along the thickness direction y of the first anisotropic sheet 41 becomes slower, while heat conduction along the in-plane direction x is promoted. As a result, the deviation in temperature distribution in the sheet surface of the first anisotropic sheet 41 can be reduced, and therefore the deviation in temperature distribution of the adjacent seed crystal 2 can also be reduced.

[0048] As the anisotropic material constituting the first anisotropic sheet 41, carbon materials containing carbon fibers and graphite sheets are preferably used. As carbon materials containing carbon fibers, C / C composites (Carbon Fiber Reinforced Carbon Composites) can be listed.

[0049] Furthermore, as a graphite sheet, a thin sheet with a planar arrangement of carbon atoms identical to those in graphite, and whose arrangement plane is aligned with the surface direction, can be used. By using such an anisotropic material, the thermal conductivity of the first anisotropic sheet 41 can be made anisotropic, and the mechanical strengths such as tensile strength and flexural strength of the first anisotropic sheet 41 can be improved. Such anisotropic material can be constructed, for example, by arranging thin carbon felt or graphite sheets along a plane that forms the in-plane direction x.

[0050] Here, the ratio of the thermal conductivity of the anisotropic material constituting the first anisotropic sheet 41 in the in-plane direction x to the thermal conductivity in the thickness direction y is preferably 2 times or more, more preferably 10 times or more. On the other hand, there is no particular upper limit to the ratio of the thermal conductivity in the in-plane direction x to the thermal conductivity in the thickness direction y, but from the viewpoint of dissipating the heat generated by the growth of SiC single crystal C from the seed crystal 2 to the base portion 17 via the first anisotropic sheet 41, a maximum of 1000 times can be set.

[0051] From the viewpoint of reducing the temperature distribution deviation of 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 base portion 17. Particularly preferred is that the first anisotropic sheet 41 extends between the seed crystal 2 and the base portion 17. In the SiC single crystal growth apparatus 1 of this embodiment, solid raw material M(s) is sublimated by heating using the heating element 3 described later, generating gaseous raw material M(g). When SiC single crystal C is grown by supplying this gaseous raw material M(g) to the seed crystal 2, as... Figure 2As shown, the gaseous feedstock M(g) also flows into the side of the seed crystal 2, forms SiC polycrystalline C′ in the cap portion 16, and then flows back, forming a gas flow towards the side of the solid feedstock M(s). Here, the first anisotropic sheet 41 extends from between the seed crystal 2 and the base portion 17, and this extended portion acts as a baffle to capture the vapor containing excess Si seeds contained in the gaseous feedstock M(g). Furthermore, it is possible to prevent the formation of gaseous ... Figure 7 The damage D3 shown is caused to the seed crystal 2 by the sublimation of the end of the seed crystal 2 and its attachment to the SiC polycrystalline C′. Furthermore, by acting as a baffle, this protruding portion promotes the formation of SiC polycrystalline C′ in the cover portion 16, thereby stabilizing the vapor pressure of the Si-seed-containing vapor in the internal space S. Therefore, it is less likely to cause damage to the heating container 10, etc., caused by defects resulting from the condensation of silicon droplets into the grown SiC single crystal C, leading to the formation of polycrystalline D2 in the SiC single crystal C, or by the Si-seed-containing vapor.

[0052] On the other hand, for example in Figure 7 (a) and Figure 7 In the comparative SiC single crystal growth apparatus 90 shown in (b), when growing SiC single crystal C, the excess Si seed vapor contained in the gaseous raw material M(g) flowing into the side of the seed crystal 2 is not effectively captured by the first anisotropic sheet 41 extending from the base portion 17. As a result, the vapor pressure of the Si seed vapor in the internal space S becomes unstable, thus generating silicon droplets in SiC single crystal C, making it easier to generate polycrystalline D2.

[0053] In addition, vapors containing Si can be exemplified by Si, SiC2, and Si2C, but are not limited to these.

[0054] From the viewpoint that the heat generated by the growth of SiC single crystal C is dissipated to the base portion 17 to promote the growth of SiC single crystal C, the thickness of the first anisotropic sheet 41 is preferably 2 mm or less. Figure 3 This is a graph showing the simulation results regarding heat conduction from the anisotropic sheet to adjacent components. Figure 3 (a) represents the case where the thickness of the anisotropic sheet is 0.04 mm. Figure 3 (b) represents the case where the thickness of the anisotropic sheet is 0.1 mm. Figure 3 (c) represents the case where the thickness of the anisotropic sheet is 1 mm. Figure 3 (d) indicates the case where the thickness of the anisotropic sheet is 2 mm. Figure 3 (e) indicates the case where the thickness of the anisotropic sheet is 4 mm. Figure 3The simulation predicts whether the localized cooling of a portion of the anisotropic sheet's surface affects the temperature of adjacent components, thereby predicting whether heat conduction to adjacent components occurs. For example... Figure 3 (a)~ Figure 3 As shown in (d), when the thickness of the anisotropic sheet is less than 2 mm, the temperature of the part indicated by the double arrow in the adjacent member decreases, so it is believed that heat can be easily dissipated from the first anisotropic sheet 41 and the second anisotropic sheet 42, which are anisotropic sheets, to the base portion 17 and the guide member 15, which are adjacent members.

[0055] On the other hand, such as Figure 3 As shown in (e), when the thickness of the anisotropic sheet is greater than 2 mm, since no temperature drop is observed in the adjacent components, it is considered that heat dissipation from the anisotropic sheet to the base 17 and the guide member 15 is not easy.

[0056] On the other hand, from the viewpoint of being easy to handle as a self-supporting film, the lower limit of the thickness of the first anisotropic sheet 41 is preferably 0.04 mm or more. In addition, since the first anisotropic sheet 41 is used in a state of being stacked on the base portion 17, it is not limited to the form of a self-supporting film, so the thickness can also be less than 0.04 mm.

[0057] The first anisotropic sheet 41 can be composed of a single anisotropic sheet or by overlapping multiple anisotropic sheets.

[0058] The arithmetic mean roughness (Ra) of the seed mounting surface 41a of the seed 2 in the first anisotropic sheet 41 is preferably 1 μm or less. In this case, it is preferable to perform mirror finishing on the contact surface of the seed 2 with the first anisotropic sheet 41. Figure 4 This is a graph showing the relationship between the arithmetic mean roughness (Ra) of the first anisotropic sheet and the density of dislocations on the substrate surface of the obtained SiC single crystal. The arithmetic mean roughness (Ra) [μm] is set as the horizontal axis, and the density of dislocations on the substrate surface [cm] is set as the horizontal axis. -2 [ is set as the vertical axis.] The experiment was conducted under identical conditions except for the arithmetic mean roughness (Ra) of the anisotropic sheet. The results are as follows: Figure 4As shown, when the arithmetic mean roughness (Ra) of the anisotropic sheet is less than 1 μm, a tendency for a lower density of basal surface dislocations is observed compared to cases where the arithmetic mean roughness (Ra) is greater than 1 μm. Therefore, by setting the arithmetic mean roughness (Ra) of the first anisotropic sheet 41 to less than 1 μm, the basal surface dislocation density of the obtained SiC single crystal C can be reduced. Furthermore, by making the surfaces of one or both of the first anisotropic sheet 41 and the seed crystal 2 flat, the surface of the seed crystal 2 can easily slide relative to the seed mounting surface 41a of the first anisotropic sheet 41, thus making it easier to mitigate the thermal stress acting on the seed crystal 2.

[0059] Here, the anisotropic material constituting the first anisotropic sheet 41 can also be configured such that the elastic modulus is larger along the in-plane direction x and smaller along the thickness direction y. As a result, thermal stress caused by the difference in thermal expansion between the seed crystal 2 and the base portion 17 can be absorbed by deformation along the thickness direction y.

[0060] In addition, among anisotropic materials such as carbon felt and graphite sheets, in most cases, the higher the elastic modulus, the higher the thermal conductivity.

[0061] There are no particular limitations on the means of mounting the SiC seed crystal 2 on the base portion 17 provided with the first anisotropic sheet 41, and it can be mounted using known mechanical means.

[0062] On the other hand, the SiC seed crystal 2 mounted on the base portion 17 can also be supported on its outer periphery by providing a plurality of protrusions (not shown) on the surface of the seed crystal 2 facing the guide member 15 (described later). Thus, by clamping the seed crystal 2 between the base portion 17 and the seed crystal 2 by the protrusions of the guide member 15, the contact between the base portion 17 and the seed crystal 2 is improved, thereby promoting the dissipation of heat generated by the growth of the SiC single crystal C to the base portion 17 via the first anisotropic sheet 41 (described later). Furthermore, since one face of the seed crystal 2 faces the solid material M(s), the deviation in the growth rate of the SiC single crystal C in the in-plane direction x can also be reduced.

[0063] Here, the size of the SiC seed crystal 2 is not particularly limited. Even when the growth surface area of ​​the seed crystal 2 is large, the SiC single crystal growth apparatus 1 of this embodiment can mitigate the temperature distribution deviation of the base portion 17 by utilizing the first anisotropic sheet 41, thereby making it less likely to cause thermal stress and strain in the seed crystal 2. Therefore, it is possible to grow a large area of ​​SiC single crystal C with fewer defects and cracks.

[0064] Since the material of crucible 11 is at a high temperature when the solid raw material M(s) is sublimated to grow SiC single crystal C, the material of crucible 11 is expected to be formed from raw materials that can withstand high temperatures.

[0065] Examples of raw materials that can withstand high temperatures include graphite, materials made by coating tantalum on graphite, and tantalum carbide.

[0066] (Regarding the heating element)

[0067] Heating element 3 heats the solid raw material M(s). More specifically, heating element 3 heats the solid raw material M(s) contained in heating container 10, thereby causing the solid raw material M(s) to sublimate. The gaseous raw material M(g) generated by sublimation passes through the internal space S formed by the cylindrical side peripheral portion 14 of crucible 11 to reach seed crystal 2, where it is cooled, thereby enabling the growth of SiC single crystal C.

[0068] The heating element 3 is configured to heat the solid raw material M(s) housed in the raw material storage section 12 within the heating container 10. Here, as... Figure 1 As shown, the heating element 3 can be positioned to cover the outer surface of the bottom 13 of the heating container 10. Alternatively, the heating element 3 can be positioned to cover the outer surface of the side peripheral portion 14 of the heating container 10 (not shown).

[0069] Furthermore, there are no particular limitations on the type of heat source constituting the heating element 3; for example, known methods such as resistance heating and induction heating can be used.

[0070] (Regarding SiC crystal growth methods)

[0071] The SiC crystal growth method of this embodiment includes a step of growing SiC single crystal C using the SiC single crystal growth apparatus described above. More specifically, in the SiC single crystal growth apparatus 1, solid raw material M(s) is sublimated by heating using the heating element 3 described later, generating gaseous raw material M(g), which is then supplied to the seed crystal 2, thereby enabling the growth of SiC single crystal C. Here, there are no particular limitations on the growth conditions of SiC single crystal C other than the SiC single crystal growth apparatus 1, and known SiC crystal growth conditions can be used.

[0072] <Second Implementation>

[0073] Figure 5 This is a schematic cross-sectional view showing the main structure of the SiC single crystal growth apparatus according to the second embodiment of the present invention. Furthermore, in the following description, the same reference numerals are used for the same constituent elements as in the first embodiment described above, and their descriptions are omitted or simplified; the main focus is on the differences.

[0074] In the first embodiment described above, such as Figure 1 (a) and Figure 1As shown in (b), a structure is illustrated in which a first anisotropic sheet 41 with anisotropic thermal conductivity is provided between the base portion 17 and the seed crystal 2, but it is not limited to this. In addition to the first anisotropic sheet 41 described above, a sheet made of anisotropic material may also be provided.

[0075] For example, Figure 5 The SiC single crystal growth apparatus 1A shown includes a guide member 15, which is located in the space between the seed crystal 2 and the raw material receiving part 12 in the internal space S, and is located on the side periphery of the heating container 10, guiding the growth direction of the SiC single crystal C growing from the surface of the seed crystal 2 from the side periphery of the SiC single crystal C.

[0076] The SiC single crystal growth apparatus 1A has a guide member 15 on the peripheral side of the SiC single crystal C. The surface of the guide member 15 is heated by the heat generated during the growth of the SiC single crystal C, thus preventing the growth of SiC single crystal C near the surface of the guide member 15, the precipitation of SiC on the surface of the guide member 15, and contact between the guide member 15 and the SiC single crystal C. Therefore, the growth direction of the SiC single crystal C can be guided along the direction of the guide member 15, and it is less likely to cause a reduction in the effective diameter of the SiC single crystal C due to precipitated SiC entering the SiC single crystal C, or defects and cracks caused by contact between the SiC single crystal C and the guide member 15.

[0077] In particular, Figure 5 In the SiC single crystal growth apparatus 1A, preferably, the surface of the guide member 15 facing the grown SiC single crystal C is covered by a second anisotropic sheet 42 having an anisotropic thermal conductivity. Thus, by protecting the guide member 15 with the second anisotropic sheet 42, damage to the guide member 15 caused by Si-containing vapors and the resulting contamination (doping) D1 of the SiC single crystal C is less likely to occur.

[0078] Here, the second anisotropic sheet 42 is configured similarly to the first anisotropic sheet 41, with a higher thermal conductivity in the in-plane direction and a lower thermal conductivity in the thickness direction. That is, the thermal conductivity in the in-plane direction is greater than the thermal conductivity in the thickness direction. As a result, the deviation in temperature distribution in the sheet surface of the second anisotropic sheet 42 can be reduced. Therefore, especially in the early stage of crystal growth, even when only a narrow portion near the seed crystal 2 in the guide member 15 is heated, the temperature over a wider range of the guide member 15 is increased, thereby making it less likely for SiC to precipitate on the surface of the guide member 15. Furthermore, since the heating of the guide member 15 causes sublimation of the portion of the SiC single crystal C that is narrowly spaced from the guide member 15, it is less likely for defects and cracks caused by contact between the SiC single crystal C and the guide member 15 to occur.

[0079] As the anisotropic material constituting the second anisotropic sheet 42, similar to the first anisotropic sheet 41, a carbon material containing carbon fibers is preferably used. Such anisotropic materials can be formed, for example, by arranging thin carbon felts or graphite sheets along surfaces that are in-plane. Particularly in the SiC single crystal growth apparatus 1A, by constituting the second anisotropic sheet 42 from thin carbon felts or graphite sheets, the second anisotropic sheet 42 can be bent, and thus the second anisotropic sheet 42 can be stacked along the guide member 15.

[0080] Here, the ratio of the thermal conductivity of the anisotropic material constituting the second anisotropic sheet 42 in the in-plane direction to the thermal conductivity in the thickness direction is preferably 2 times or more, more preferably 10 times 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 can also be set to 1000 times. From the viewpoint of reducing the deviation of temperature distribution on the surface of the guide member 15, the area of ​​the second anisotropic sheet 42 is preferably larger than the surface area of ​​the guide member 15, and it is particularly preferred that it covers the entire surface of the guide member 15.

[0081] The arithmetic mean roughness (Ra) of the single-crystal facing surface 42a of the second anisotropic sheet 42, which faces the grown SiC single crystal C, is preferably 1 μm or less. Therefore, in the above-mentioned... Figure 4 Similar to the description of the first anisotropic sheet 41, the dislocation density on the basal surface of the obtained SiC single crystal C can be reduced. Furthermore, since the formation of crystal nuclei on the single-crystal facing face 42a of the second anisotropic sheet 42 is suppressed, SiC precipitation on the surface of the second anisotropic sheet 42 is less likely to occur. Furthermore, since the formation of crystal nuclei in the obtained SiC single crystal C is suppressed, the nucleation of polycrystalline D2 in the SiC single crystal C is less likely to occur. Moreover, even when the grown SiC single crystal C and the single-crystal facing face 42a are in contact, the surface of the SiC single crystal C easily slides relative to the single-crystal facing face 42a of the second anisotropic sheet 42, thus mitigating the thermal stress acting on the SiC single crystal C and reducing the likelihood of defects and cracks in the SiC single crystal C.

[0082] As mentioned above Figure 3 (a)~ Figure 3As shown in (d), from the viewpoint of promoting heat dissipation to the guide member 15 via the second anisotropic sheet 42, the thickness of the second anisotropic sheet 42 is preferably 2 mm or less. On the other hand, from the viewpoint of improving the mechanical strength of the second anisotropic sheet 42 and improving the temperature uniformity of the second anisotropic sheet 42 along the in-plane direction, the lower limit of the thickness of the second anisotropic sheet 42 is preferably 0.04 mm or more. In addition, since the second anisotropic sheet 42 is not limited to the form of a self-supporting film when used in a state of being stacked on the guide member 15, the thickness of the second anisotropic sheet 42 can also be less than 0.04 mm.

[0083] The second anisotropic sheet 42 can be composed of a single anisotropic sheet or by overlapping multiple anisotropic sheets.

[0084] <Third Implementation>

[0085] Figure 6 This is a cross-sectional view schematically showing the main structure of the SiC single crystal growth apparatus according to the third embodiment of the present invention. Furthermore, in the following description, the same reference numerals are used for the same constituent elements as in the first or second embodiment described above, and their descriptions are omitted or simplified; the main focus is on the differences.

[0086] In the second embodiment described above, such as Figure 5 As shown, the SiC single crystal growth apparatus 1A has a structure including a guide member 15 and a second anisotropic sheet 42 on the surface of the guide member 15, but it is not limited to this. For example, it can also be like... Figure 6 The SiC single crystal growth apparatus 1B shown does not have a guiding member 15 but only a second anisotropic sheet 42. In this case, it is preferable that at least a portion of the second anisotropic sheet 42 is supported by a supporting member 5.

[0087] From the viewpoint of using the second anisotropic sheet 42 in a self-supporting state, the thickness of the second anisotropic sheet 42 of the SiC single crystal growth apparatus 1B is preferably 0.1 mm or more. On the other hand, from the viewpoint of promoting heat dissipation to the guide member 15 via the second anisotropic sheet 42, the thickness of the second anisotropic sheet 42 is preferably 2 mm or less.

[0088] The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments, but includes the concept of the present invention and all the solutions included in the claims, and various changes can be made within the scope of the present invention.

[0089]

Example

[0090] Next, in order to further clarify the effects of the present invention, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

[0091] [Example 1 of the present invention]

[0092] exist Figure 1 In the described configuration, the crucible 11 has a raw material receiving section 12, which has a cylindrical internal space S with an inner diameter of 180 mm and a height of 160 mm. The internal space S is formed by a cylindrical side peripheral portion 14. In the crucible 11, SiC powder as a solid raw material M(s) is stored from the bottom of the internal space S to a height of 60 mm from the bottom. Furthermore, a tubular guide member 15 in the shape of a frustum is provided on the side peripheral portion of the crucible 11 in the internal space S above the raw material receiving section 12. The lower side (one side of the raw material receiving section 12) has a diameter of 180 mm, the upper side (one side of the seed crystal 2) has a diameter of 149 mm, and the height is 30 mm. Adjacent to the upper side of the guide member 15, a seed crystal 2 is disposed on the lid 16 of the crucible 11 and fixed to the base portion 17 with a diameter of 150 mm and a thickness of 2 mm, which is separated by a first anisotropic sheet 41. At this point, the position 128 mm above the bottom of the internal space S becomes the growth surface of the seed crystal 2.

[0093] Here, the first anisotropic sheet 41 is made of graphite sheet as an anisotropic material, and is configured with a diameter of 155 mm and a thickness of 0.04 mm, extending concentrically from both the base portion 17 and the seed crystal 2. The thermal conductivity of this anisotropic material in the in-plane x-direction is set to 400 W / mK (2200 °C), and the thermal conductivity in the thickness y-direction is set to 1.5 W / mK (2200 °C). Therefore, the ratio of the thermal conductivity in the thickness y-direction to the thermal conductivity in the in-plane x-direction is 266 times. On the other hand, the base portion 17 is made of isotropic graphite, and its thermal conductivity is set to 40 W / mK (2200 °C).

[0094] The heating container 10, which is made of the crucible 11, is placed on a flat heating element 3 with a diameter of 250 mm that has a heat source made of resistance heating elements. The solid raw material M(s) is then heated so that the temperature of the heating container 10 is in the range of 2300℃±10℃, and SiC single crystal C is grown for 50 hours.

[0095] The results showed that the density of basal dislocations in the obtained SiC single crystal C was 1000 cm⁻¹. -2 .

[0096] [Example 2 of the present invention]

[0097] by Figure 5The entire surface of the guide member 15 opposite to the grown SiC single crystal C is provided with a second anisotropic sheet 42.

[0098] Here, the second anisotropic sheet 42 is composed of a sheet formed by overlapping graphite sheets, which are anisotropic materials, and the thickness is set to 0.1 mm. The thermal conductivity of this anisotropic material in the in-plane x direction is set to 300 W / mK (2200 °C), and the thermal conductivity in the thickness y direction is set to 1 W / mK (2200 °C).

[0099] The conditions other than those in Example 1 of this invention are the same, allowing SiC single crystal C to grow for 100 hours.

[0100] The results showed that the density of basal dislocations in the obtained SiC single crystal C was 1500 cm⁻¹. -2 .

[0101] [Example 3 of the present invention]

[0102] by Figure 6 The described configuration does not include a guide member 15, but instead includes a self-supporting second anisotropic sheet 42 with a thickness of 1 mm, and the second anisotropic sheet 42 is fixed to the heating container 10 using a support member 5.

[0103] The conditions are the same as in Example 2 of this invention, except that SiC single crystal C is grown for 100 hours.

[0104] The results showed that the density of basal dislocations in the obtained SiC single crystal C was 1000 cm⁻¹. -2 .

[0105] [Comparative Example 1]

[0106] by Figure 7 (a) and Figure 7 The configuration described in (b) constitutes a SiC single crystal growth apparatus 90 for comparison without either the first anisotropic sheet 41 or the second anisotropic sheet 42.

[0107] SiC single crystal C was grown for 100 hours under the same conditions as in Example 2 of the present invention, except for the first anisotropic sheet 41 and the second anisotropic sheet 42.

[0108] The results showed that the density of dislocations on the basal surface of the obtained SiC single crystal after 50 hours of growth was 10,000 cm⁻¹. -2 It was also learned that the density of dislocations on the basal surface of the obtained SiC single crystal after 100 hours of growth was 20,000 cm⁻¹. -2 .

[0109] Based on the above, in the SiC single crystal growth apparatus of Examples 1 to 3 of the present invention, a first anisotropic sheet 41 with thermal conductivity is provided, and the density of dislocations on the substrate surface after crystal growth for 50 to 100 hours is 2000 cm⁻¹. -2 the following.

[0110] Therefore, the SiC single crystal growth apparatus of Examples 1 to 3 of the present invention can reduce the deviation of temperature distribution of seed crystal 2, deformation and damage of seed crystal 2, thereby enabling the growth of SiC single crystal with fewer defects and cracks.

[0111] In particular, in the SiC single crystal growth apparatus of Example 3 of the present invention, compared with the SiC single crystal growth apparatus of Example 2 of the present invention which is provided with the guiding member 15, the density of dislocations on the basal surface of the obtained SiC single crystal C is smaller. It is believed that this is because, since the second anisotropic sheet 42 is not constrained by the guiding member 15, it is less affected by the thermal stress of the second anisotropic sheet 42.

[0112] On the other hand, since the SiC single crystal growth apparatus 90 used in Comparative Example 1 does not have a first anisotropic sheet 41, the density of basal dislocations in the obtained SiC single crystal C is relatively high. Furthermore, after 100 hours of crystal growth, the SiC single crystal is invaded by polycrystalline D2 formed on the surface of the guiding member 15, resulting in a smaller effective diameter. Additionally, localized erosion occurs in the heating container 10, and contamination (doping) D1 is generated on the SiC single crystal C.

[0113] Specifically, as a reason for the formation of polycrystalline D2 in SiC single crystal C in Comparative Example 1, it can be cited that silicon droplets are generated because the vapor containing excess Si seeds is not captured, thereby forming polycrystalline. In addition, since the first anisotropic sheet 41 is not provided, the temperature distribution deviation of the seed crystal 2 becomes larger, thereby increasing the density of dislocations on the substrate surface.

[0114] On the other hand, the reason for the contamination (doping) D1 of SiC single crystal C in Comparative Example 1 is believed to be that erosion occurred locally in the heating container 10, and the micro powder originating from the heating container 10 generated by the erosion contaminated the SiC single crystal C.

[0115] Explanation of reference numerals in the attached figures

[0116] 1. 1A, 1B, SiC single crystal growth apparatus; 10. Heating container; 11. Crucible; 12. Raw material receiving section; 13. Bottom of the raw material receiving section; 14. Side peripheral portion of the raw material receiving section; 15. Guiding member; 16. Cover; 17. Base portion; 2. (SiC) Seed crystal; 3. Heating component; 41. First anisotropic sheet; 42. Second anisotropic sheet; 42a. Single crystal opposing surface of the second anisotropic sheet; 5. Support member; 90. Comparative SiC single crystal growth apparatus; S. Internal space; x. In-plane direction of the first anisotropic sheet; y. Thickness direction of the first anisotropic sheet; M(s), Solid raw material; M(g), Gas raw material; D1. Contamination (doping) of SiC single crystal; D2. Polycrystal intrusion into the SiC single crystal; D3. Damage to the end of the seed crystal.

Claims

1. A SiC single crystal growth apparatus, wherein, The SiC single crystal growth apparatus includes: A heating container, having a material receiving section for receiving solid raw material made of SiC in either of its upper or lower portions of an internal space divided by a cylindrical side periphery, and a base section for mounting SiC seed crystals in another portion located opposite said portion; and A heating element that heats the solid raw material. The seed crystal is mounted on the base portion via a first anisotropic sheet with thermal conductivity. Regarding the first anisotropic sheet, the thermal conductivity in the in-plane direction is relatively high, while the thermal conductivity in the thickness direction is relatively low. The first anisotropic sheet is configured to have a larger area than the seed crystal and the base portion, and extends from between the seed crystal and the base portion.

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

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

4. The SiC single crystal growth apparatus according to claim 1 or 2, wherein, The SiC single crystal growth apparatus also includes a guiding member located in the space between the seed crystal and the raw material receiving section within the internal space, and situated on the side periphery of the heating container. This guiding member guides the growth direction of the SiC single crystal growing from the surface of the seed crystal from the side periphery of the seed crystal. The surface of the guiding member opposite to the grown SiC single crystal is covered by a second anisotropic sheet with anisotropic thermal conductivity. Regarding the second anisotropic sheet, the thermal conductivity in the in-plane direction of the sheet is relatively large, while the thermal conductivity in the thickness direction of the sheet is relatively small.

5. The SiC single crystal growth apparatus according to claim 4, wherein, The arithmetic mean roughness (Ra) of the single-crystal opposing surfaces of the second anisotropic sheet is less than 1 μm.

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

7. A method for growing SiC crystals, wherein, The SiC crystal growth method includes a step of growing a SiC single crystal using the SiC single crystal growth apparatus according to any one of claims 1 to 6.

Images