Method for Removing Impurities by Treating Silicon Tetrachloride with Hydrogen Plasma

The transformation of organochlorine and organic impurities such as CCl4, C2H2Cl2, C2HCl3, C2Cl4, C2H2Cl4, CH4, C3H8, C4H10, and C6H6 in the content range of 10−2–10−6 wt.%, as well as BCl3 impurities at the level of 3 × 10−2 wt.%, was considered. A method has been developed for removing limiting impurities of carbon and boron during the process of the hydrogen reduction of silicon tetrachloride in a high-frequency arc gas discharge at atmospheric pressure. The thermodynamic and gas-dynamic analyses of the reduction process of silicon tetrachloride in hydrogen plasma, along with the behavior of organochlorine impurities, organic substances, and boron trichloride, was conducted. These analyses suggest that under equilibrium conditions, the conversion reactions of impurities result in the formation of silicon carbide and boron silicide. Potential chemical reactions for the conversion of the studied impurities into silicon carbide and boron silicide have been proposed. A new potential for plasma chemical processes has been identified, enabling the effective purification of chlorosilanes from both limiting and limited impurities. The results demonstrate the possibility of significantly reducing the concentrations of organochlorine and organic impurities, as well as boron trichloride, during the reduction of silicon tetrachloride in hydrogen plasma. The maximum conversion rates achieved included 99% for the organochlorine impurity CCl4 to silicon carbide, 91% for benzene impurity to silicon carbide, and 86% for boron trichloride to boron silicide.