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

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.