Similarities and differences between direct current and radio-frequency glow discharges: a mathematical simulation

A comprehensive three-dimensional modeling network has been developed both for argon glow discharges operating in the direct current (dc) and in the r adio-frequency (rf) mode. The model network consists of various Monte Carlo , fluid and collisional-radiative models to describe the behavior of the el ectrons, argon atoms, argon ions, fast argon atoms, argon atoms in various excited levels, sputtered copper atoms and the corresponding ions, both in the ground state and in various excited levels. Typical results of the simu lations comprise the electrical characteristics of the glow discharge, the densities, fluxes and energies of the various plasma species, information a bout collisions in the plasma, optical emission intensities and erosion rat es due to sputtering. The results for the dc and the rf discharges have bee n compared. It is found that for the same input power (i.e., power effectiv ely going into the plasma) and pressure, the rf discharge requires lower vo ltages than the dc discharge, in agreement with experimental data. The eros ion rates and optical emission intensities are, however, rather similar in both operation modes, which is also in agreement with experiment.