Numerical analysis of surface wave excitation in a planar-type nonmagnetized plasma processing device

Two-dimensional numerical simulations based on the finite-difference time-domain approximation to Maxwell's equations coupled with nonmagnetized cold electron plasma equations are used to study surface wave propagation in a four-layer planar type surface wave plasma processing structure (Komachi et al., 1994) under the assumption that the plasma is overdense. Simulations are used to verify the existence of surface waves along the plasma-dielectric window interface as well as to investigate the excitation mechanism of surface waves. In addition, simulations are used to study the effect of the air gap on the electric field distribution at the plasma-dielectric window interface. It is found that metal edges located along the processing chamber wall sufficiently close to the interface are needed to excite surface waves along the interface. It is also found that the air gap layer helps achieve a more uniform electric field distribution over the processing chamber.