Ion distribution functions in inductively coupled radio frequency discharges in argon–chlorine mixtures

Abstract

We report on measurements of positive ion energies, current densities, and angular distributions at the grounded electrode of inductively coupled discharges in mixtures of argon and chlorine. We also report on ion species and Langmuir probe measurements for these discharges. The inductive drive in our gaseous electronics conference reference cell produced high plasma densities (1011–1012/cm3) and stable plasma potentials. As a result, ion energy distributions consisted of a single peak well separated from zero energy. At pressures of 2.5–20 mTorr and constant rf power, the addition of Cl2 to an Ar discharge lowered ion current densities, reduced ion energies, and reduced the width of the ion energy distributions. Half-widths of the ion angular distributions ranged from 4.5° to 8.5° with the distributions broadening with increases in pressure or rf power. The addition of Cl2 to Ar discharges made the angular distributions less sensitive to total pressure. Cl+ replaced Ar+ as the dominant ionized species when small amounts of chlorine were added to Ar discharges.