DISTRIBUTION OF SPECIES WITHIN AN ETHYLENE ELECTRON-CYCLOTRON RESONANCE-MICROWAVE PLASMA

Electron cyclotron resonance microwave plasmas consisting of 2% ethyle ne in hydrogen and 2% ethylene in deuterium have been probed using the pulsed supersonic, plasma sampling technique. Comparison of the compo sitions of these two chemically equivalent plasmas provides the basis for examining the details of species interconversion and overall hydro carbon chemistry within these plasmas. The ethylene/hydrogen plasma is shown to be composed of 9% ethane radical (C2H5), 38% ethylene (C2H4) , 8% ethylene radical (C2H3), and 41% acetylene (C2H2), with the remai ning counts attributed to impurities in the plasma. Due to interferenc es between the daughter ions of the radical species and the parent ion s of ethylene and acetylene, the concentrations of radical species, re ported above, represent only a lower limit estimate, based only on the parent ion intensity. Analysis of the mass spectrum obtained for the analogous deuterium plasma, based on the results from the hydrogen pla sma experiments, reveal the acetylene components of the deuterium plas ma to be 14% undeuterated (C2H2), 43% singly deuterated (C2HD), and 43 % doubly deuterated (C2D2). The extensive deuteration of the acetylene indicates that the majority of the chemistry in these plasmas is repe ated cycles of hydrogen (deuterium) atom addition to acetylene followe d by abstractions from the radical species (C2HxD3-x) The absence of a ny significant intensity due to doubly, triply, or fully deuterated et hylenes indicates that the addition of hydrogen (deuterium) to the rad ical species C2HxD3-x is a much more rare event than abstraction. (C) 1998 American Vacuum Society. [S0734-2101(98)09204-5].