Investigation of the low-pressure plasma-chemical conversion of fluorocarbon waste gases

Abstract

The kinetics of the plasma-chemical conversion of a number of saturated, as well as of unsaturated, fluorocarbon compounds is studied in an oxygen-based rf discharge by FTIR spectroscopy. Unsaturated fluorocarbons are rapidly converted into CF4 and C2F6, which, in the presence of silica walls, are finally converted quantitatively into SiF4 (etch reaction). The results of this investigation are used to design a plasma-chemical reactor for the conversion of fluorocarbon exhaust gases into SiF4 in the vacuum line of a technological low-pressure plasma reactor. Furthermore, it is shown that the primary conversion product SiF4 can be effectively converted into CaF2 in a heterogeneous reaction with a CaO/Ca(OH)2 absorber, also in the low-pressure line of the pumping system.