Development status of SiC coated graphite technology
SiC coated graphite substrates are commonly used as components for supporting and heating single crystal substrates in metal organic chemical vapor deposition (MOCVD) equipment. MOCVD equipment is a key equipment for the research and industrialization of epitaxial growth of compound semiconductor single crystal substrates. The thermal stability, thermal uniformity, and other performance parameters of SiC coated graphite substrates play a decisive role in the quality of epitaxial material growth, and are therefore the core key components of MOCVD equipment.
Choosing the β - SiC (3C SiC) crystal form as the coating, this crystal form has a series of excellent properties such as good thermodynamic stability, oxidation resistance, and corrosion resistance compared to other crystal forms. At the same time, it has a thermal conductivity that is basically the same as graphite. Therefore, it endows the graphite base with special properties, which can effectively solve the failure of the graphite base caused by high-temperature oxidation and corrosion during service, making the surface of the graphite base dense, pore free, high temperature resistant, corrosion-resistant, and oxidation resistant, thereby improving the quality of crystal epitaxy and the service life of the graphite base (the service life of SiC coated graphite base is measured in furnace cycles).
The SiC coated graphite base needs to withstand one cycle of high and low temperatures for each furnace, during which the SiC coating is prone to cracking, collapse, and other damage, which will cause the chips on the base to be contaminated and seriously affect the service life of the base. Therefore, the quality of SiC coating directly affects the service life of graphite substrate.
To ensure the good and stable performance of SiC coated graphite substrate, in addition to the substrate properties such as purity and processing precision of high-purity graphite, the main difficulty lies in maintaining the consistency of crystal structure, surface morphology, and thickness of SiC coating. The growth process of high-quality coatings requires extremely strict requirements. During the growth process of SiC polycrystalline coatings, there may be more than 100 types of crystal transformation, and the temperature and other conditions for different crystal transformation are relatively small; The larger the size of the base and the thicker the coating, the higher the technical difficulty. In addition, it is more difficult to control the uniformity of the coating on irregular surfaces such as arcs, chamfers, steps, etc. Therefore, subtle changes in factors such as temperature, pressure, and atmosphere during the growth process of coatings can directly affect product quality and service life. At present, the service life (furnace number) of graphite base is the most critical indicator for measuring products.
The entry of SiC coated graphite base into the supply chain requires great cooperation from equipment manufacturers and equipment users for application verification. Only when the product's service life reaches the international advanced level can it have a competitive advantage in the market.
Firstly, SiC coated graphite base products must undergo application verification by MOCVD equipment manufacturers. After the product is tested on MOCVD equipment, the equipment manufacturer evaluates the product from multiple dimensions such as usage quality and lifespan. Through repeated delivery and feedback, technical and process adjustments are continuously made from both production and usage aspects to achieve international advanced performance and competitive advantages. Finally, the product is verified and added to the supplier list, and its development and verification time generally takes 2-3 years. At the same time, equipment manufacturers also have certain requirements for the production equipment of SiC coated graphite bases: once the SiC coated graphite base samples provided by the base manufacturer pass the equipment manufacturer's verification, the base manufacturer shall not easily replace the production equipment of the base. Under the condition that the sample passes the acceptance smoothly, the verification process takes 2-3 weeks. Due to strict requirements for production equipment, any new equipment added by the base manufacturer during the expansion process must be verified by the equipment manufacturer.
The entry of SiC coated graphite base into the supply chain requires great cooperation from equipment manufacturers and equipment users for application verification. Only when the product's service life reaches the international advanced level can it have a competitive advantage in the market.
Firstly, SiC coated graphite base products must undergo application verification by MOCVD equipment manufacturers. After the product is tested on MOCVD equipment, the equipment manufacturer evaluates the product from multiple dimensions such as usage quality and lifespan. Through repeated delivery and feedback, technical and process adjustments are continuously made from both production and usage aspects to achieve international advanced performance and competitive advantages. Finally, the product is verified and added to the supplier list, and its development and verification time generally takes 2-3 years. At the same time, equipment manufacturers also have certain requirements for the production equipment of SiC coated graphite bases: once the SiC coated graphite base samples provided by the base manufacturer pass the equipment manufacturer's verification, the base manufacturer shall not easily replace the production equipment of the base. Under the condition that the sample passes the acceptance smoothly, the verification process takes 2-3 weeks. Due to strict requirements for production equipment, any new equipment added by the base manufacturer during the expansion process must be verified by the equipment manufacturer.
Secondly, the equipment user also needs to evaluate and verify the performance and stability of SiC coated graphite base products used as consumables in the actual production process to ensure that the produced epitaxial wafers meet the corresponding requirements. This verification process takes 9-12 months, and only after passing the verification can large-scale purchase orders be achieved. Both equipment manufacturers and equipment users will not easily change their supplier lists, resulting in strong user stickiness and a high threshold for entering the market.
SiC coated graphite substrates are a niche market with a relatively small overall market size. SiC coated graphite base products have high technical barriers and therefore have high technical added value. Depending on their size and quality, the unit price of each product ranges from tens of thousands to tens of thousands of yuan. The market for SiC coated graphite base products is directly related to factors such as the inventory of MOCVD equipment and product service life. According to calculations, there are currently over a thousand MOCVD equipment in use in China, with a single SiC coated graphite base having a service life of about 1-1.5 months. The market for SiC coated graphite bases as consumables is approximately 100 million yuan. The semiconductor industry in China is developing rapidly. With the gradual increase in the localization rate of MOCVD epitaxial equipment and the expansion of other process applications, the market for SiC coated graphite base products is expected to grow rapidly in the future. According to industry insiders' preliminary estimates, the domestic graphite pedestal market will exceed 500 million yuan in the next few years.
At present, the verification of domestic SiC coated graphite base products entering the industry chain is underway, and the time for the products to enter the industry chain is too long. Accelerating the verification process is necessary to provide better feedback on product quality and create a healthy competitive environment between products, which is beneficial for improving the overall level of SiC coated graphite base products. SiC coated graphite base, as the core component of compound semiconductor industrialization equipment, mastering the key core technology of its production and manufacturing, realizing the localization of the entire industry chain of raw materials, processes and equipment, is of great strategic significance for ensuring the development of China's semiconductor industry. The field of domestically produced SiC coated graphite bases is booming, and the product quality is expected to reach the international advanced level soon.