Silicon carbide (SiC) has two crystal structures: β-SiC (cubic) at low temperatures and α-SiC (hexagonal) at high temperatures. SiC has strong bonding and is stable thermally, chemically, and mechanically. It exists in different polytypes with varying physical properties.
4H-SiC is ideal for high-voltage, high-temperature, radiation-resistant power devices due to its high breakdown electric field and electron mobility. It is the most advanced 3rd-generation semiconductor, offering superior performance and maturity. Compared to silicon, it has a higher breakdown field and electron mobility. Key characteristics of 4H-SiC include:
- The critical breakdown field strength is nearly 10 times higher than silicon material.
- It has a thermal conductivity three times higher than silicon material.
- It has a saturation electron drift velocity twice that of silicon material.
- It has good radiation resistance and chemical stability.
- Like silicon material, it can undergo thermal oxidation to form a silicon dioxide-insulating layer on the surface.
SiC industry chain mainly includes powder, single crystal materials, epitaxial materials, chip preparation, power devices, module packaging, and applications.
SiC Crystals ：
This includes physical vapor transport, high-temperature chemical vapor deposition, and liquid phase methods. Physical vapor transport is the main industrial method, using graphite heating elements heated by an induction coil. Silicon carbide powder and seed crystals are placed in a graphite crucible. By adjusting the temperature gradient, the silicon carbide raw materials decompose into vapor phase substances in the high-temperature zone and then grow into SiC crystals on the seed crystals.
SiC substrate:
SiC substrates with high transparency, no damage, and low roughness are produced through different steps. The international standard for SiC substrates has changed from 4 inches to 6 inches, and there is also the development of an 8-inch conductive SiC substrate.
SiC epitaxy:
SiC epitaxial materials are grown using various methods such as chemical vapor deposition (CVD), liquid phase epitaxy, molecular beam epitaxy, and sublimation epitaxy. Among these, CVD is widely used for large-scale production. In CVD, high-purity argon or hydrogen gas is used to transport Si and C source gases into the deposition chamber. A chemical reaction occurs, resulting in the formation of SiC molecules that deposit onto the silicon carbide substrate, matching its crystal orientation. The epitaxial wafers can be doped with either n-type or p-type dopants.
SiC devices:
SiC power devices, including diodes, MOSFETs, and modules, are widely used in industry. They come in through-hole packages. SiC Schottky diodes and MOSFETs below 1200V are commonly used. SiC power modules combine MOSFETs and diodes, with the driver chip usually external. It can also be integrated for better performance, creating an intelligent module.
SiC semiconductor materials have promising market potential in next-generation power electronic devices. As technology advances and production scales up, the cost of SiC materials is expected to decrease, driving the commercialization of SiC power electronic devices.
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