Polysilicon CVD
The Chemical Vapor Deposition (CVD) process involves the deposition of silicon atoms onto a substrate, typically a heated silicon rod, from a gaseous chemical precursor—such as Trichlorosilane (TCS)—in a controlled environment. The reaction causes the silicon to deposit onto the substrate in the form of high-purity polysilicon, while byproducts such as hydrogen chloride are removed from the system.
TCS Decomposition
TCS is broken down (decomposed) into its constituent elements—silicon and chlorine—under controlled high-temperature conditions. The decomposition of TCS plays a key role in ensuring that the silicon deposited in the CVD process is of the highest possible purity. The TCS decomposition reaction occurs when TCS (SiHCl₃) is exposed to high temperatures, typically around 1100°C to 1200°C, in the presence of hydrogen (Hâ‚‚) gas.
Off Gas Recovery
In the production of polysilicon through the Chemical Vapor Deposition (CVD) process, off-gases are generated as a byproduct of chemical reactions. These off-gases typically contain a variety of substances, including unreacted chlorosilane gases, reaction byproducts like hydrogen chloride (HCl), and other volatile compounds. Efficiently capturing, recovering, and neutralizing these off-gases is critical not only for maintaining environmental standards but also for optimizing the overall efficiency and cost-effectiveness of the polysilicon production process.