Reaction Mechanisms in Both a CHF₃/O₂/Ar and CHF₃/H₂/Ar Radio Frequency Plasma Environment

Abstract

A radio frequency (RF) plasma system used to decompose trifluoromethane (CHF3 or HFC-23) is demonstrated. The CHF3 decomposition fractions (ηCHF3) and mole fractions of detected products in the effluent gas streams of CHF3/O2/Ar and CHF3/H2/Ar plasma systems, respectively, have been determined. The effects of four experimental parameters, input power, O2/CHF3 or H2/CHF3 ratio, operational pressure, and the CHF3 feeding concentration were investigated. The same species detected in the effluent gas streams of both CHF3/O2/Ar and CHF3/H2/Ar plasma systems were CH2F2, CF4, HF, and SiF4. However, the CO2 and COF2 were detected only in the CHF3/O2/Ar plasma system and the CH4, C2H2, and CH3F were detected only in the CHF3/H2/Ar plasma system. The results of a model sensitivity analysis showed that the input power was the most influential parameter for ηCHF3 both in the CHF3/O2/Ar and CHF3/H2/Ar plasma systems. Furthermore, the possible reaction pathways were built up and elucidated in this study. The addition of hydrogen for CHF3 decomposition can produce a significant amount of HF and the main carbonaceous byproducts were CH4 and C2H2. Even though the ηCHF3 in the CHF3/H2/Ar plasma system is lower than that in the CHF3/O2/Ar plasma system, but due to the more advantages mentioned above, a hydrogen-based RF plasma system is a better alternative to decompose CHF3.