Equilibrium calculations for plasmas of volatile halides of III, IV and VI group elements mixed with H2 and H2 + CX4 (X = H, Cl, F) relevant to PECVD of isotopic materials

Abstract

The composition of hydrogen and hydrogen-methane plasmas containing ~ 10% of BX3, SiX4, GeX4 (X = F, Cl), SF6, MoF6 and WF6 is calculated for the temperature range ~ 300–4000 K using the equilibrium chemical model. The calculations provide valuable information about thermodynamic parameters (pressure, temperature) needed for condensation of pure elements (in H2 plasma) and their carbides (in H2 + CH4 plasma) and about intermediate reaction products. Using volatile fluorides for plasma chemical deposition alleviates obtaining monoisotopic elements and their isotopic compounds because fluorine is monoisotopic. PECVD is promising method for one-step conversion of fluorides to elemental isotopes and their carbides. For fluorides, further insight is needed into properties of plasmas supported by different types of discharges.