CVD TaC Coated Rings

Semicorex CVD TaC Coated Rings are precision-engineered components designed specifically for the crystal growth process, particularly within the directional solidification and Czochralski (CZ) pulling systems. These CVD TaC Coated Rings function as flow guide components—commonly referred to as “flow guide rings” or “gas deflection rings”—and play a critical role in maintaining stable gas flow patterns and thermal environments during the crystal growth phase.

Taking silicon carbide wafer growth as an example, graphite materials and carbon-carbon composite materials in thermal field materials are difficult to meet the complex atmosphere (Si, SiC₂, Si₂C) process at 2300℃. Not only is the service life short, different parts are replaced every one to ten furnaces, and the dialysis and volatilization of graphite at high temperatures can easily lead to crystal defects such as carbon inclusions. In order to ensure the high quality and stable growth of semiconductor crystals, and considering the cost of industrial production, ultra-high temperature corrosion-resistant ceramic coatings are prepared on the surface of graphite parts, which will extend the life of graphite components, inhibit impurity migration and improve crystal purity. In the epitaxial growth of silicon carbide, silicon carbide coated graphite susceptors are usually used to carry and heat single crystal substrates. Their service life still needs to be improved, and silicon carbide deposits on the interface need to be cleaned regularly. In contrast, tantalum carbide (TaC) coatings are more resistant to corrosive atmospheres and high temperatures, and are the core technology for such SiC crystals to "grow, grow thick, and grow well".

TaC has a melting point of up to 3880℃, and has high mechanical strength, hardness, and thermal shock resistance; it has good chemical inertness and thermal stability to ammonia, hydrogen, and silicon-containing vapor at high temperatures. Graphite (carbon-carbon composite) materials coated with TaC coatings are very likely to replace traditional high-purity graphite, pBN coatings, SiC coated parts, etc. In addition, in the field of aerospace, TaC has great potential to be used as a high-temperature anti-oxidation and anti-ablation coating, and has broad application prospects. However, there are still many challenges to achieve the preparation of dense, uniform, and non-flaking TaC coatings on the surface of graphite and promote industrial mass production. In this process, exploring the protection mechanism of the coating, innovating the production process, and competing with the top foreign level are crucial for the third-generation semiconductor crystal growth and epitaxy.

The SiC PVT process using a set of conventional graphite and CVD TaC Coated Rings was modeled to understand the effect of emissivity on temperature distribution, which may lead to changes in growth rate and ingot shape. It is shown that CVD TaC Coated Rings will achieve more uniform temperatures compared to existing graphite. In addition, the excellent thermal and chemical stability of the TaC coating prevents the reaction of carbon with Si vapor. As a result, the TaC coating makes the distribution of C/Si in the radial direction more uniform.