Crucible

Abstract

To provide a crucible capable of suppressing a crack of a SiC single crystal.SOLUTION: A crucible 10 used for manufacturing a SiC single crystal by a sublimation method includes: a container 12 made of graphite; a lid 16 that is arranged over the container 12, has a bottom surface 160 for attaching a SiC seed crystal 22, and is made of graphite; and a self-sacrifice plate 18 that is arranged between the lid 16 and the SiC seed crystal 22 and is breakable easier than a SiC single crystal 26.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a crucible, and more specifically, to a crucible used in producing a SiC (Silicon Carbide) single crystal by a sublimation method. [Background technology]

[0002] Japanese Patent Application Publication No. 2007-290880 (Patent Document 1), Japanese Patent Application Publication No. 2011-195360 (Patent Document 2), and Japanese Patent Application Publication No. 2015-36348 (Patent Document 3) disclose crucibles used when producing SiC single crystals by sublimation.

[0003] JP 2015-131748 A (Patent Document 4) discloses a method for producing a silicon carbide single crystal. This production method includes a step of fixing a seed substrate and a pedestal via a stress buffer layer, a step of growing a silicon carbide single crystal on the seed substrate, a step of separating the silicon carbide single crystal from the pedestal at the stress buffer layer, and a step of removing a residue of the stress buffer layer adhering to the silicon carbide single crystal after the separation step. The stress buffer layer has a lower hardness than silicon carbide constituting the seed substrate and is easy to process. Therefore, it is said that in the separation step, by separating the silicon carbide single crystal from the pedestal at the stress buffer layer, the silicon carbide single crystal can be easily separated from the pedestal. The stress buffer layer is made of a material that is lower in hardness and has high flexibility and elasticity compared to the seed substrate and the silicon carbide single crystal. The material constituting the stress buffer layer is, for example, a graphite sheet.

[0004] Japanese Patent Laid-Open Publication No. 2014-159347 (Patent Document 5) discloses a manufacturing apparatus for silicon carbide single crystal substrates. This manufacturing apparatus includes a raw material storage section and a seed substrate holding section. The seed substrate holding section includes a plate section having a first main surface and a second main surface facing each other, a main body section in contact with the first main surface of the plate section, and a connection section for fixing the plate section to the main body section. The thickness of the plate section is smaller than the thickness of the main body section. According to this manufacturing apparatus, it is said that the stress generated in the seed substrate and the silicon carbide single crystal growing on the seed substrate due to the difference in the amount of thermal expansion between the material constituting the seed substrate and the material constituting the plate section during the growth of the silicon carbide single crystal can be efficiently reduced by the plate section deforming in response to the deformation of the seed substrate.

[0005] WO2016 / 006442A1 (Patent Document 6) discloses a method for producing silicon carbide single crystal. This production method includes a step of preparing a support member having an adhesive part and a step part at least on a part of the periphery of the adhesive part, and a step of arranging a buffer material at the step part, where the adhesive part and the buffer material form a support surface, and further includes a step of arranging a seed crystal on the support surface and adhering the adhesive part and the seed crystal, and a step of growing a single crystal on the seed crystal. In this production method, a step part is provided at least on a part of the periphery of the adhesive part (for example, a part of the support member corresponding to the periphery of the SiC single crystal), and a buffer material (for example, a graphite sheet) is arranged at the step part. It is said that this can efficiently relieve thermal stress occurring near the periphery of the seed crystal.

[0006] JP 2015-193494 A (Patent Document 7) discloses a method for producing a silicon carbide ingot. This production method includes a step of preparing a silicon carbide seed crystal and a step of fixing the silicon carbide seed crystal on a pedestal. The step of fixing the silicon carbide seed crystal includes a first fixing step in which a first adhesive is placed on the pedestal and a buffer member is placed between the pedestal and the first adhesive, and a second fixing step in which a second adhesive is placed on the buffer member and the silicon carbide seed crystal is placed between the buffer member and the second adhesive. This production method further includes a step of growing a silicon carbide layer on a crystal growth surface of the silicon carbide seed crystal opposite to the pedestal. It is said that by placing a buffer member between the silicon carbide seed crystal and the pedestal, it is possible to buffer distortion caused by a difference in thermal expansion coefficient between the silicon carbide seed crystal and the pedestal. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2007-290880 A [Patent Document 2] JP 2011-195360 A [Patent Document 3] JP 2015-36348 A [Patent Document 4] JP 2015-131748 A [Patent Document 5] JP 2014-159347 A [Patent Document 6] WO2016 / 006442A1 [Patent Document 7] JP 2015-193494 A Summary of the Invention [Problem to be solved by the invention]

[0008] The above Patent Documents 4 to 7 all disclose means for buffering, reducing or mitigating the stress applied to a SiC single crystal (hereinafter sometimes referred to as a "grown crystal"), but the following discloses an alternative means.

[0009] An object of the present disclosure is to provide a crucible that can suppress cracking of SiC single crystal. [Means for solving the problem]

[0010] The crucible according to the present disclosure is a crucible used in producing SiC single crystals by sublimation method, and comprises a container made of graphite, a lid provided on the container and having a lower surface for attaching a SiC seed crystal, and a self-sacrificial plate provided between the lid and the SiC seed crystal, the self-sacrificial plate being more easily broken than the SiC single crystal. [Brief description of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view showing the structure of a crucible according to a first embodiment. [Diagram 2] 10 is a cross-sectional view showing the structure of a lid and a self-sacrificial plate in a crucible according to embodiment 2. FIG. [Diagram 3] 11 is a cross-sectional view showing the structure of a lid and a self-sacrificial plate in a crucible according to embodiment 3. FIG. [Figure 4] 1 is a graph showing the stresses on a 150 mm diameter self-sacrificial plate and a growing crystal. [Diagram 5] 1 is a graph showing the stresses on a 200 mm diameter self-sacrificial plate and a growing crystal. [Figure 6] 1 is a graph showing the stresses on a 250 mm diameter self-sacrificial plate and a growing crystal. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] <Overview of the embodiment> The crucible according to this embodiment is a crucible used for producing SiC single crystals by sublimation, and includes a container made of graphite, a lid provided on the container and having a lower surface for attaching a SiC seed crystal, and a self-sacrificial plate provided between the lid and the SiC seed crystal, which is more easily broken than the SiC single crystal.

[0013] Since the crucible according to the present embodiment is provided with a self-sacrificial plate, the self-sacrificial plate breaks before the SiC single crystal breaks, which makes it possible to suppress cracking of the SiC single crystal.

[0014] The self-sacrificial plate may have a hardness that is less than the hardness of the SiC seed crystal.

[0015] The self-sacrificial plate may have a fracture strength less than that of the SiC seed crystal, in which case the self-sacrificial plate will fracture before the SiC single crystal because it is easier to fracture than the SiC single crystal.

[0016] The self-sacrificial plate may have a thickness of 1.5 mm or less. In this case, the self-sacrificial plate is so thin that it cracks before the SiC single crystal cracks.

[0017] The self-sacrificial plate may be made of graphite.

[0018] The self-sacrificial plate may be made of a CIP (Cold Isostatic Press) material.

[0019] The self-sacrificial plate has an upper surface facing the lower surface of the lid, and the upper surface may have one or more scribes. In this case, the self-sacrificial plate is likely to crack starting from the scribes.

[0020] The crucible may further include a support disposed between the container and the lid for supporting the SiC seed crystal.

[0021] The lid may include a circular base having an underside of the lid.

[0022] The self-sacrificial plate may be made of a CIP material, and the base may be made of an extruded material. The thermal expansion coefficient of the CIP material is larger than that of the SiC single crystal, and the thermal expansion coefficient of the extruded material is smaller than that of the SiC single crystal. In the cooling process after the growth of the SiC single crystal is completed, if the self-sacrificial plate is made of an extruded material, tensile stress is applied to the SiC single crystal, but if the self-sacrificial plate is made of a CIP material, compressive stress is applied to the SiC single crystal. The SiC single crystal is stronger against compressive stress than tensile stress. Therefore, if the self-sacrificial plate is made of a CIP material, the self-sacrificial plate breaks before the SiC single crystal breaks, and the SiC single crystal is less likely to break. On the other hand, the thermal conductivity of the extruded material is higher than that of the CIP material. In order to cool the SiC seed crystal and increase the crystal growth rate, it is preferable that the base be made of an extruded material rather than a CIP material. Therefore, if the self-sacrificial plate is made of a CIP material and the base is made of an extruded material, the SiC single crystal is less likely to break and the crystal growth rate is increased. In addition, the amount of expensive CIP material used can be reduced.

[0023] The self-sacrificial plate may have a diameter larger than that of the pedestal, in which case the self-sacrificial plate protruding from the pedestal can function as a barrier to prevent the SiC polycrystal grown around the pedestal from reaching the SiC single crystal grown on the SiC seed crystal.

[0024] <Details of the embodiment> Hereinafter, a crucible according to an embodiment will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference characters, and the description thereof will not be repeated.

[0025] <Embodiment 1> <Structure of the crucible> 1, crucible 10 according to embodiment 1 is a crucible used in producing a SiC single crystal by a sublimation method, and includes a container 12, a support 14, a lid 16, and a self-sacrificial plate 18. Container 12, support 14, and lid 16 are all made of graphite.

[0026] The container 12 is for introducing the powdered SiC raw material 20. The container 12 includes a bottom 120 and a side wall 122 extending upward from the periphery of the bottom 120. The lid 16 is provided on the container 12 and has a lower surface 160 for mounting the SiC seed crystal 22. The lid 16 includes a pedestal 162. The pedestal 162 is substantially circular and has the lower surface 160 of the lid 16. The support 14 is for supporting the SiC seed crystal 22. The self-sacrificial plate 18 is provided between the lid 16 and the SiC seed crystal 22 and is more likely to crack than the grown SiC single crystal.

[0027] The upper surface of the support part 14 may support the SiC seed crystal 22 from below and press the SiC seed crystal 22 upward. The cross-sectional shape of the support part 14 is not limited to a specific shape and may be a rectangle, a right-angled triangle, a trapezoid, or the like.

[0028] The self-sacrificial plate 18 has a hardness smaller than that of the SiC seed crystal 22. The self-sacrificial plate 18 has a fracture strength smaller than that of the SiC seed crystal 22. The self-sacrificial plate 18 has a thickness smaller than that of the SiC seed crystal 22. The self-sacrificial plate 18 has a thickness of 1.5 mm or less, preferably 1.4 mm or less, and more preferably 1.3 mm or less. The thickness of the self-sacrificial plate 18 is preferably 0.1 mm or more. The thickness of the self-sacrificial plate 18 is, for example, 1.5 mm, 1.4 mm, 1.3 mm, 1.2 mm, 1.1 mm, 1.0 mm, 0.9 mm, 0.8 mm, 0.7 mm, 0.6 mm, 0.5 mm, 0.4 mm, 0.3 mm, 0.2 mm, or 0.1 mm. The diameter of the self-sacrificial plate 18 is not particularly limited, but is, for example, 150 to 300 mm.

[0029] The self-sacrificial plate 18 is made of graphite. The self-sacrificial plate 18 is made of a CIP material. The self-sacrificial plate 18 is made of a CIP material, but the lid 16 is made of an extruded material.

[0030] An example of a method for attaching the self-sacrificial plate 18 to the lid 16 will now be described.

[0031] First, adhesive is applied to the lid 16. Next, the self-sacrificial plate 18 is placed on the bottom surface 160 of the lid 16 with the adhesive applied. Next, the surface of the self-sacrificial plate 18 is polished. Next, the SiC seed crystal 22 is placed on the self-sacrificial plate 18 (bottom surface). Finally, the SiC seed crystal 22 is pressed down by the support stand 142 of the support part 14. The adhesive is carbonized at high temperatures to reduce or eliminate the adhesive force so that the self-sacrificial plate 18 is easily broken. When the adhesive force is eliminated, the self-sacrificial plate 18 is freed from the lid 16. In this way, the growing crystal (SiC single crystal) and the self-sacrificial plate 18 are freed during the temperature rise process, but a polycrystalline adhesion layer grows between the growing crystal and the self-sacrificial plate 18 in a region with a periphery width of about 1 mm. Therefore, the growing crystal and the self-sacrificial plate 18 are adhered to each other only in a region with a periphery width of 1 mm, and the self-sacrificial plate 18 is broken starting from this adhesion region. Therefore, the stress applied to the SiC single crystal grown on the SiC seed crystal 22 is alleviated, and the SiC single crystal is less likely to crack. Therefore, the self-sacrificial plate 18 is more likely to crack before the SiC single crystal cracks.

[0032] Next, an example of a method for producing a SiC single crystal by sublimation using crucible 10 will be described. A sublimation recrystallization method (Rayleigh method) is used for growing a SiC single crystal. The sublimation recrystallization method is a method for growing a SiC single crystal by creating a temperature gradient between the lower and upper parts of crucible 10, heating and sublimating charged SiC raw material 20 at a high temperature (2000°C or higher), and recrystallizing it on a SiC seed crystal 22 placed on pedestal 162.

[0033] As described above, since the crucible 10 according to the first embodiment is provided with the self-sacrificial plate 18, the self-sacrificial plate 18 breaks before the SiC single crystal breaks. As a result, it is possible to suppress cracking of the SiC single crystal.

[0034] <Embodiment 2> Referring to FIG. 2, in the crucible according to the second embodiment, the self-sacrificial plate 18 has an upper surface facing the lower surface 160 of the lid 16, and the upper surface has one or more scribes 180. When the self-sacrificial plate 18 is viewed from above, the scribes 180 may be straight lines, broken lines, curved lines, or a combination thereof. The scribes 180 may be short, long, or a combination thereof. The scribes 180 may be formed in large numbers on the periphery of the self-sacrificial plate 18, may be formed in large numbers in the center, or may be formed evenly all over the plate. Since the scribes 180 are formed on the self-sacrificial plate 18, the self-sacrificial plate 18 is prone to cracking starting from the scribes 180.

[0035] <Embodiment 3> 3, in the crucible according to the third embodiment, the self-sacrificial plate 18 has a diameter larger than that of the pedestal 162. The periphery of the self-sacrificial plate 18 reaches outside beyond the periphery of the pedestal 162. In this case, the self-sacrificial plate 18 protruding from the pedestal 162 functions as a barrier and can prevent the SiC polycrystal grown in the space 24 around the pedestal 162 from reaching the grown SiC single crystal 26.

[0036] If the self-sacrificial plate 18 is not provided, while the SiC single crystal 26 grows, SiC polycrystals are formed in the space 24 around the pedestal 162, and an adhesion layer may be formed between the pedestal 162 and the grown SiC single crystal 26. If an adhesion layer is formed, the grown SiC single crystal 26 may crack when the crucible 10 is cooled to room temperature. This is because there is a difference in thermal expansion coefficient between the pedestal 162 and the SiC single crystal 26. The difference in thermal expansion coefficient between the extrusion material and the SiC single crystal 26 is larger than the difference in thermal expansion coefficient between the CIP material and the SiC single crystal 26. If the pedestal 162 is made of an extrusion material, the SiC single crystal is more likely to crack. Therefore, the self-sacrificial plate 18 is made of a CIP material. EXAMPLES

[0037] Experiments were carried out to determine whether or not the self-sacrificial plate 18 would crack when the thickness of the self-sacrificial plate 18 was 2 mm, 1 mm, 0.8 mm, and 0.5 mm. The results are shown in Table 1.

[0038] [Table 1]

[0039] <Experimental conditions> In the experiment, the crucible 10 according to the first embodiment was used. The crucible including the lid is made of an extrusion material. The self-sacrificial plate is made of a CIP material. The diameter of the self-sacrificial plate is 150 mm. The thickness of the grown SiC single crystal (grown crystal) is 10 mm. The linear expansion coefficient of the self-sacrificial plate is temperature dependent, not anisotropic, and isotropic. The elastic constant of the self-sacrificial plate is isotropic and not temperature dependent. The Young's modulus of the self-sacrificial plate is 9.8 MPa, and the Poisson's ratio is 0.2. The linear expansion coefficient of the grown crystal is temperature dependent, not anisotropic, and isotropic. The elastic constant of the grown crystal is isotropic and not temperature dependent. The Young's modulus of the grown crystal is 500 MPa, and the Poisson's ratio is 0.21. An adhesion layer with a width of 1 mm around the circumference exists between the grown crystal and the self-sacrificial plate. The SiC raw material was placed in a crucible, heated and sublimated at 2300°C, and recrystallized on the SiC seed crystal to grow a SiC single crystal. The temperature was then lowered from 2300°C to room temperature.

[0040] As shown in Table 1, the 2.0 mm self-sacrificial plate 18 did not crack, but the 1.0 mm, 0.8 mm, and 0.5 mm self-sacrificial plates 18 cracked.

[0041] In addition, a simulation was performed on the stress (Mises equivalent stress) generated in the self-sacrificial plate and the growing crystal, and the results are shown in Table 2 and Figures 4 to 6.

[0042] [Table 2]

[0043] Looking broadly at the graphs in Figures 4 to 6, it was found that the thinner the self-sacrificial plate, the smaller the stress on the grown crystal. In other words, it was found that the thinner the self-sacrificial plate, the less likely the grown crystal is to crack and the more likely the self-sacrificial plate is to crack. It was also found that the stress on the self-sacrificial plate and the grown crystal is almost independent of the diameter of the grown crystal. Therefore, it was found that regardless of the diameter of the grown crystal, if the thickness of the self-sacrificial plate is 1.5 mm or less, the grown crystal is less likely to crack and the self-sacrificial plate is more likely to crack.

[0044] As described above, by optimizing the thickness of the self-sacrificial plate, it is possible to make the grown crystal less likely to break by making the self-sacrificial plate more likely to break, regardless of the diameter of the grown crystal.

[0045] Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and can be modified within the scope of the claims. [Explanation of symbols]

[0046] 10: Crucible 12: Container 14: Support part 16: Lid 18: Self-sacrifice board 22:SiC seed crystal 26: SiC single crystal 160: Bottom surface 162: Pedestal

Claims

1. A crucible used in producing a SiC single crystal by a sublimation method, A container made of graphite; a lid made of graphite, the lid being provided on the container and having a lower surface for mounting a SiC seed crystal; a self-sacrificial plate disposed between the lid and the SiC seed crystal and more fragile than the SiC single crystal.

2. 2. The crucible of claim 1, The self-sacrificial plate has a hardness less than a hardness of the SiC seed crystal.

3. 2. The crucible of claim 1, the self-sacrificial plate having a fracture strength less than a fracture strength of the SiC seed crystal.

4. 2. The crucible of claim 1, The self-sacrificial plate has a thickness of 1.5 mm or less.

5. 2. The crucible of claim 1, The self-sacrificial plate is made of graphite.

6. 2. The crucible of claim 1, The self-sacrificial plate is made of CIP material.

7. 2. The crucible of claim 1, The self-sacrificial plate has an upper surface opposite a lower surface of the lid, the upper surface having one or more scribes.

8. The crucible of claim 1 further comprising: A crucible comprising a support for supporting the SiC seed crystal.

9. 2. The crucible of claim 1, The lid is The crucible includes a circular base having the lower surface.

10. 10. The crucible of claim 9, The crucible, wherein the self-sacrificial plate is made of a CIP material and the base is made of an extruded material.

11. 10. The crucible of claim 9, The self-sacrificial plate has a diameter greater than a diameter of the pedestal.

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