Modeling and diagnostics of the structure of rf glow discharges in Ar at 13.56 MHz

Abstract

The structure of rf glow discharges in Ar at 13.56 MHz is described, making use of a relaxation continuum model. The model includes consideration of the relaxation kinetics for the momentum and energy of charged particles. The discharge structure and plasma property are modeled using molecular quantities (i.e., collision cross sections, radiative lifetimes, etc.) and macroscopic transport quantities for charged particles. Spatiotemporal distributions for the field and the net production rate and density of particles are studied in detail in the bulk plasma as well as the ion sheath under periodic steady-state conditions. In particular, the temporal profiles including phase shift and nonlinear variation with respect to the applied-voltage wave form are discussed. Each type of excited atom shows a different spatiotemporal density distribution due to different loss mechanisms, although the production profiles are similar. That is, Ar${(}^3$ ${\mathit{p}}_5$) is controlled by a radiative decay and quenching in collisions with Ar${(}^1$ ${\mathit{S}}_0$), while Ar${(}^3$ ${\mathit{P}}_{0,2}$) is controlled by diffusion. The validity of the relaxation continuum model is investigated by the observation of external electric properties and the measurement of spatiotemporally resolved optical emission from the rf glow. Quantitative comparison of the results from theory and experiment supports the validity of the relaxation continuum model. The relaxation continuum model is simple and physically reasonable.