Kinetics of the Reactions Involving CF[sub 2] and CF in a Pure Tetrafluoromethane Plasma: II. Production and Loss of CF[sub 2] and CF in the Processes of Fluorocarbon Polymerization

Mechanisms for the production and loss of CF[sub 2] and CF radicals in a glow discharge in pure CF[sub 4] are investigated by the time-resolved laser-induced fluorescence method. The fluorocarbon polymerization processes are shown to contribute significantly to the production of radicals both in the plasma volume and on the surface of the discharge tube. The effective frequencies of both the volume and surface processes of radical production and loss are determined. An analysis of these frequencies allowed us to study the polymerization mechanism in a CF[sub 4] plasma at a high relative concentration of F atoms and low ion energy. It is shown that, at elevated pressures, when the density of C[sub x]F[sub y] polymer particles in the plasma volume becomes comparable with the density of simple fluorocarbon radicals, the electron-impact dissociation of these particles is the main channel for the production of CF[sub 2] and CF radicals. Another source of CF[sub 2] and CF radicals is related to the reactions of C[sub n]F[sub 2m+1] unsaturated fluorocarbon particles both in the plasma volume and on the surface of a fluorocarbon film arising on the discharge tube wall. The C[sub x]F[sub y] fluorocarbon polymer particles form both in the discharge volume and on the fluorocarbon film surface also in the course of the film destruction. At lowered pressures, the main channel for the production of CF[sub 2] and CF is the direct electron-impact dissociation of CF[sub 4] molecules, whereas the loss of these radicals at the tube wall is the main loss channel. The probabilities of the heterogeneous losses of CF[sub 2] and CF radicals on the heavily fluorinated surface of the fluorocarbon film at low ion energies are determined. Under these conditions, the surface recombination of the F[sub ch] chemisorbed fluorine atoms and CF[sub x][sup ph] physisorbed radicals with the production of an activated complex is shown to be the most probable mechanism for the...