When silicon carbide crystal grows, the “environment” of the growth interface between the axial center of the crystal and the edge is different, so that the crystal stress on the edge increases, and the crystal edge is easy to produce “comprehensive defects” due to the influence of the graphite stop ring “carbon”, how to solve the edge problem or increase the effective area of the center (more than 95%) is an important technical topic.
As macro defects such as “microtubules” and “inclusions” are gradually controlled by the industry, challenging silicon carbide crystals to “grow fast, long and thick, and grow up”, the edge “comprehensive defects” are abnormally prominent, and with the increase in the diameter and thickness of silicon carbide crystals, the edge “comprehensive defects” will be multiplied by the diameter square and 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 up”. In order to promote the development of industry technology and solve the “import” dependence of key materials, Hengpu has breakthrough solved the tantalum carbide coating technology (CVD) and reached the international advanced level.
Tantalum carbide TaC coating, from the perspective of realization is not difficult, with sintering, CVD and other methods are easy to achieve. Sintering method, the use of tantalum carbide powder or precursor, adding active ingredients (generally metal) and bonding agent (generally long chain polymer), coated to the surface of the graphite substrate sintered at high temperature. By CVD method, TaCl5+H2+CH4 was deposited on the surface of graphite matrix at 900-1500℃.
However, the basic parameters such as crystal orientation of tantalum carbide deposition, uniform film thickness, stress release between coating and graphite matrix, surface cracks, etc., are extremely challenging. Especially in the sic crystal growth environment, a stable service life is the core parameter, is the most difficult.
Post time: Jul-21-2023