Method for growing silicon carbide crystal on growth surface

Abstract

[Problem] In the field of silicon carbide (SiC) crystal growth, precise controls of temperature and gas flow have been essential. In particular, temperature gradient causes crystal defects and thermoelectric field strain, which reduces the yield of SiC substrates and prevents a reduction in manufacturing costs. [Solution] The source substrate made of silicon carbide sublimates the source molecules from its sublimation surface. These molecules are transported stably and evenly to the growth surface of the seed substrate, which is also made of silicon carbide, by the force of gravity. This method does not require a temperature gradient, and it is possible to form multiple SiC growth layers simultaneously. It also prevents SiC molecules from falling off the back surface of the seed substrate or from the gap between the source substrate and the seed substrate. As a result, the efficiency of SiC material usage is improved, leading to increased productivity and reduced manufacturing costs. ​

Claims

1. A method for growing silicon carbide crystals on a growth surface, comprising: Carbon and silicon molecules are synthesized as raw material molecules. Silicon carbide is made into a plate-like structure as a raw material substrate. The raw material molecules are sublimated from the sublimation surface of the raw material substrate. The aforementioned raw material molecules are crystallized on the growth surface made of silicon carbide. The plate-like structure that grows into silicon carbide crystals is regarded as the growth substrate. The growth substrate is arranged in a gravitational field with the growth surface vertically upward. The raw material substrate is arranged opposite it with its sublimation surface vertically downward. The vertically downward side of the growth substrate is composed of carbon, boron nitride (BN), aluminum oxide (Al₂O₃), and zirconium oxide (ZrO₂). A protective film with a thickness of more than 10 μm and no gaps is formed by either yttrium oxide (Y₂O₃) or tantalum carbide (TaC). The sublimation surface and the opposite growth surface are spaced at a certain interval of more than 0.1 mm and less than 3 mm. The gap between the growth surface and the sublimation surface is filled with one or more inactive gases of helium (He), neon (Ne), nitrogen (N₂), argon (Ar), and krypton (Kr) at a pressure of more than 700 hPa and less than 1300 hPa, and the average temperature is maintained at more than 1900 °C and less than 2300 °C.

2. The silicon carbide crystal growth method as described in claim 1, wherein the raw material substrate is composed of silicon carbide microcrystals or micropowder, and the specific gravity (JIS R1634) of the raw material substrate is 1.6 g / cm³ or more and 3.1 g / cm³ or less.

3. The silicon carbide crystal growth method as described in claim 1, wherein a single crystal silicon carbide is exposed on the growth surface, and the angle between the growth surface and the substrate surface of the crystal lattice is more than 1 degree and less than 12 degrees.

4. The silicon carbide crystal growth method as described in claim 3, wherein the raw material substrate is composed of silicon carbide microcrystals or micropowder, and the specific gravity (JIS R1634) of the raw material substrate is 1.6 g / cm³ or more and 3.1 g / cm³ or less.

5. The silicon carbide crystal growth method as described in claim 3, wherein the sublimation surface of the raw material substrate exposes single-crystal silicon carbide, and the adjacency angle between the sublimation surface and the base surface of the crystal lattice is at least 2 degrees higher than the adjacency angle between the growth surface facing the sublimation surface and the base surface of the crystal lattice.

6. The silicon carbide crystal growth method as described in claim 5, wherein the raw material substrate is made of single-crystal silicon carbide, and a raw material auxiliary substrate is disposed vertically above the raw material substrate, the raw material auxiliary substrate being composed of silicon carbide microcrystals or micro powder, the specific gravity (JIS R 1634) being 1.6 g / cm³ or more and 3.1 g / cm³ or less.

7. The silicon carbide crystal growth method according to any one of claims 1 to 6, wherein the growth substrate and the raw material substrate are in the shape of a disc and are coaxially arranged, and the diameter of the raw material substrate is more than 1.1 times the diameter of the growth substrate.

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