2-DIMENSIONAL MODEL FOR THERMAL PLASMA CHEMICAL-VAPOR-DEPOSITION

A formulation of a global mathematical two-dimensional model for Therm al Plasma Chemical Vapor Deposition (TPCVD) is reported. Both gas-phas e and surface chemical kinetics as well as ordinary and thermal diffus ion are incorporated. Flow is assumed to be steady, laminar and swirll ess at this stage. The results include velocity, pressure, density, te mperature and chemical species distributions in the reactor, and the h eat flux and the film growth characteristics at the substrate. The mod el has been applied to a low pressure diamond TPCVD. Two basic cases h ave been investigated: (1) supersonic jet regime, and (2) high speed s ubsonic jet regime. The results for both cases are presented and compa red. In both cases, the hydrocarbon species needed for the diamond for mation are assumed to be premixed in the plasma jet. The main conclusi ons are: (1) The low pressure high speed jets are very narrow and slow down only at the substrate through a bow shock, (2) the faster the je t, the bigger the total deposited amount of diamond but also the highe r the heat flux and diamond growth rate nonuniformities.