Production of semiconductor silicon is based on a CVD process which uses silane (SiH4) or trichlorosilane (Cl3SiH) as a precursor. When heated up to 900-1200 °C, the precursors decompose and free silicon deposits onto seed particles. To increase the process efficiency the CVD process was integrated into a microwave-heated flow-bed reactor (FBR).
Silicon is a strong absorber of microwave radiation (at 2.45 GHz and 915 MHz), which allows the silicon seeds to be heated directly, leading to high process temperatures. Furthermore, optimized temperature distribution can be achieved using the flow-bed reactor, and the risk of contamination due to high wall temperatures can be reduced, too.
These two effects lead to more heterogenic deposition of the silicon on the seed particles as well as to better process control. Increased process efficiency and a higher process yield are major advantages of the MW-CVD process.
Besides the production of solar-grade silicon, the deposition process can also be used to coat other materials such as carbon fiber tissues or porous carbon particles. Compared to conventional processes, higher coating efficiency and increased throughput were achieved.