CVD TaC coating Guide Ring

Semixlab's CVD TaC coating Guide Ring is designed for the PVT SiC single crystal growth process and uses chemical vapor deposition (CVD) technology to form a highly dense tantalum carbide (TaC) coating on the surface of a high-purity graphite substrate. The product is used in the PVT process to ensure SiC single crystal quality and growth efficiency by precisely controlling the thermal field distribution and airflow direction of the SiC single crystal growth furnace. Suitable for a variety of mainstream SiC single crystal growth furnace systems and homemade systems, suitable for high temperature (> 2000°C) and strong corrosive atmosphere.

Tantalum carbide (TaC), as a typical representative of ultra-high temperature ceramics, has a melting point of 3880℃, a Mohs hardness of nearly 10, excellent thermal conductivity (about 22 W/m·K) and low thermal expansion coefficient (6.6×10-6 K-1), and the thermal expansion matching degree with graphite substrate is significantly better than that of traditional SiC coating. The TaC coating was grown in the temperature range of 1373~1673K by chemical vapor deposition (CVD) using the TaCl₅-C₃H₆-H₂-Ar reaction system, which allowed for accurate control of coating thickness (50~300μm), grain size, and free carbon content. The results show that when the deposition temperature reaches 1573K, TaC coating presents a crack-free compact sintering interface, and the grains form a continuous anti-spalling structure through metallurgical bonding. The number of thermal shock resistance cycles is more than 5 times higher than that of uncoated graphite. A gradient transition layer design, such as the TaC/Ta₂O composite structure, was introduced in the process to further ease the interface stress between the coating and the substrate and ensure that it maintains geometric stability despite severe temperature fluctuations (>1000 °C/ min).

In the PVT growth furnace, the CVD TaC coated Deflector ring is responsible for guiding the gas phase transmission path, maintaining the axial temperature gradient, and supporting the seed crystal and the raw material crucible. Traditional graphite components are easy to react with Si/C vapor to form volatile carbides at high temperatures, resulting in surface erosion and release of impurities, which directly affect the purity of the crystal. Due to its extreme chemical inertness, CVD TaC coating exhibits near zero reactivity to Si, C vapor and byproducts (such as HCl) at 2300℃, effectively blocking the diffusion of substrate impurities (Fe, Al and other metal elements) to the growth interface. The measured data show that after the TaC coating guide ring is used, the microtubule density of 6-inch SiC single crystal is reduced to < 0.5cm-2, and the resistivity uniformity is increased to within ±3%, which is especially suitable for the mass production of SiC MOSFETs above 1200V for electric drive modules of new energy vehicles.

In order to adapt to the mainstream PVT SiC single crystal growth equipment, the CVD TaC coating Guide Ring adopts a modular design. By optimizing the precursor flow rate and deposition path, the coating thickness uniformity deviation is controlled within ±3%, even in the face of complex flow channel structures (such as spiral gas channel, porous medium layer), full surface coverage can be achieved. Compared with the traditional spray or sintered coating, the CVD process gives the TaC layer a microhardness of up to 25GPa and an interface bonding strength of > 50MPa. After 2000 hours of continuous high temperature operation, the coating quality loss rate is less than 0.1%, which significantly extends the part replacement cycle. According to statistics, the SiC ingot production line using the guide ring can extend the effective growth time per furnace to more than 120 hours, increase the annual production capacity by about 18%, and reduce the unplanned downtime due to component failure by 70%.

Temperature gradient control of SiC single crystal growing furnace.

Silicon carbide crystal expanding and directional growth guidance.

Ultra-high temperature performance: TaC coating temperature resistance up to 2000°C, high temperature stability is better than traditional SiC coating.

Strong corrosion resistance: Excellent resistance to strong corrosive media such as molten silicon and carbon vapor.

Precise thermal field control: high coating uniformity (grain size 5-15μm) to ensure single crystal growth consistency.

Customized design: Support complex structure guide ring processing, suitable for multi-brand and self-designed single crystal furnace growth system.