Breakthrough TaC Coatings of SiC Crystal Growth
When silicon carbide crystals grow, the "environment" of the growth interface between the axial center of the crystal and the edge is different, which increases the crystal stress at the edge, and the crystal edge is prone to "comprehensive defects" due to the influence of the "carbon" of the graphite ring. Solving the edge problem or increasing the effective area of the center (more than 95%) is an important technical topic.
As macroscopic defects such as "micropipes" and "wrappings" are gradually controlled by the industry, challenging silicon carbide crystals to "grow fast, grow thick, and grow up", the edge "comprehensive defects" are extremely prominent. The increase of the edge "comprehensive defects" will increase in multiples of the square of the diameter and the thickness.
The use of tantalum carbide TaC coating is to solve the edge problem and improve the quality of crystal growth, which is one of the core technical directions of "growing fast, growing thick and growing". In order to promote the development of industry technology and solve the dependence on "import" of key materials, HIPER has made a breakthrough in solving the tantalum carbide coating technology (CVD), which has reached the international advanced level.
Tantalum carbide TaC coating is not difficult from the perspective of realization, and it is easy to realize by sintering, CVD and other methods. The sintering method uses tantalum carbide powder or precursors, adds active components (usually metals) and binders (usually long-chain polymers), and coats them on the surface of graphite substrates for high-temperature sintering. The CVD method uses TaCl5+H2+CH4 at 900-1500°C to deposit on the surface of the graphite substrate.
However, basic parameters such as crystal orientation of tantalum carbide deposition, uniform film thickness, stress release between coating and graphite substrate, and surface cracks are extremely challenging. Especially in the sic crystal growth environment, having a stable service life is the core parameter and the most difficult point.
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