Studies of Mode Transitions in Inductively Coupled Plasma Reactors

Optical emission spectroscopy and Langmuir probe measurements have been used to study mode transitions and hysterisis in a GEC Inductively Coupled Plasma reactor operating in both Ar and Ar/O$_{2}$ mixtures over a range of pressures. Ar emission line ratios have been used to monitor the variations of the electron temperature and the influence of the metastable Ar atoms in both discharge modes [1]. The first results show a smooth decrease of the electron temperature with power, followed by an abrupt transition when the plasma jumps to the H mode, with a clear reduction in electron temperature. Similar results are obtained with a Langmuir probe. Also, a strong variation of the metastable density with the transition was observed. Its influence on the transition and associated hysteresis will be discussed. \newline \newline [1] S. A. Moshkalyov, P. G. Steen, S. Gomez, and W. G. Graham, Appl. Phys. Lett., \textbf{75}, 328 (1999).