Investigation of the plasma chemistry relevant for diamond deposition withchlorinated hydrocarbons

We have investigated the plasma chemistry of process gases consisting of hy drogen with a small admixture of chlorinated methanes in a pulsed r.f. disc harge. The temporal development of certain species in the plasma was explor ed by experiment and simulation. Experiment and simulation are in good agre ement and show a very fast decomposition of the chlorinated methanes to the main stable species hydrogen chloride, methane, and acetylene. Chlorinated methyl radicals, which are possible diamond growth species, are created du ring the decomposition process. However, they decompose so quickly that the y occur only within a few ms after the first contact of the feed stock gas with the plasma. The simulation showed that atomic chlorine is, besides ato mic hydrogen and the methyl radical, the third most important radical in th e gas phase. Chlorine in the gas phase increases the methyl radical concent ration at lower temperatures. As atomic chlorine generates active surface s ites more efficiently than atomic hydrogen and higher methyl radical concen trations are present at lower temperatures, higher growth rates are possibl e with chlorinated process gas mixtures. (C) 2001 Elsevier Science Ltd. All rights reserved.