Kinetic model of a low-pressure microwave discharge in O2-H2 including the effects of O- ions on thecharacteristics for plasma maintenance

Abstract

A consistent theoretical analysis of a low-pressure (p = 1 Torr) microwave discharge ( MHz and 2450 MHz) in O2-H2 is presented. The model is based on the coupled solutions to the homogeneous electron Boltzmann equation and a system of rate balance equations for the dominant neutral and charged particles in the discharge. The sustaining electric field is self-consistently derived from the set of continuity and momentum transfer equations for electrons and ions O2+, O+, NO+, N4+, and O-. A deviation from the classical ambipolar diffusion is observed due to the presence of O- ions. The recombination of O(3P) atoms on the tube walls is taken into account through a Monte-Carlo-like simulation of a sequence of elementary surface processes. This formulation provides results for the mean input power absorbed from the field per electron, , and for the concentrations of and O(3P) in satisfactory agreement with measured data. Other important calculated data such as the concentrations of the ionic species and the percentage contributions of the various ionization mechanisms are also reported.