With the continuous development of PVT technology for preparing SiC single crystals, the entire SiC single crystal industry chain is also constantly evolving. "High-purity materials and two-coating" will continuously provide the SiC single crystal production chain with high-purity raw materials and consumables.
High-purity SiC powder: According to statistics, the purity (mass fraction, the same below) of SiC powder used for silicon carbide crystal growth ranges from 99.95% to 99.9999%. Currently, the improved self-propagating high-temperature synthesis method is the most representative among high-purity SiC powder synthesis methods. This method is simple, efficient, and commonly used to prepare SiC powder, typically for synthesizing high-purity SiC powder.
High-purity carbon powder: The purity of carbon powder directly affects the purity of SiC powder. Currently, companies such as SGL Carbon (Germany) and Mersen (USA) have mastered high-purity carbon powder purification processes, while Dingli Technology in China has mastered the purification process for 6N carbon powder.
High-purity graphite: High-purity graphite products are widely used in third-generation semiconductor single crystal growth equipment, mainly for graphite crucibles and heaters in SiC single crystal growth furnaces. They are also commonly used in GaN epitaxial growth on graphite substrates and high-temperature ablation-resistant coated graphite substrates.
High-purity rigid felt: In the PVT single crystal growth process, carbon fiber rigid felt plays a role in heat preservation, and the purity of the rigid felt is crucial for the successful growth of SiC crystals. Impurities in the insulating rigid felt material are one of the sources of contamination during the growth process. The content of key impurity elements in carbon fiber rigid felt must be controlled below 10⁻⁶, and the total ash content must be strictly controlled.
SiC Coating
SiC coatings are primarily used as consumables in semiconductor manufacturing. Key performance indicators include coating uniformity, coefficient of thermal expansion, and thermal conductivity. Silicon carbide-coated graphite disks are among the best substrates currently available for single-crystal silicon epitaxial growth and gallium nitride (GaN) epitaxial growth, and are a core component of epitaxial furnaces.
Tantalum Carbide (TaC) Coating
TaC-coated graphite exhibits better chemical corrosion resistance than bare graphite or SiC-coated graphite. It can be used stably at temperatures up to 2600℃ and does not react with many metal elements. It is the best-performing coating for third-generation semiconductor single-crystal growth and wafer etching, significantly improving temperature and impurity control during the process and producing high-quality silicon carbide wafers and related epitaxial wafers. It is particularly suitable for growing GaN or AlN single crystals in MOCVD equipment and SiC single crystals in PVT equipment, resulting in a significant improvement in the quality of the grown single crystals.
High-purity SiC powder, as the direct raw material for growing SiC crystals, directly affects the quality of SiC single crystals. The purity of high-purity carbon powder determines the purity of SiC powder. Among the many impurities, nitrogen (N) content is the highest, and further research is needed to reduce N content. High-purity hard felt and high-purity graphite products are essential components of PVT equipment, and their impurities and ash content have a significant impact on crystal quality during growth. As protective coatings, SiC and TaC coatings face challenges in CVD coating preparation, such as achieving good, uniform, and thick deposition, which require further exploration.