Ion energy and angular distributions in inductively driven radio frequency discharges in chlorine

In this article, we report values of ion energy and angular distributions measured at the grounded electrode of an inductively coupled discharge in chlorine gas. The inductive rf drive in our cell produced high plasma densities (1011/cm3 electron densities) and stable plasma potentials. As a result, ion energy distributions typically consisted of a single peak well separated from zero energy. Mean ion energy varied inversely with pressure, decreasing from 13 to 9 eV as the discharge pressure increased from 20 to 60 mTorr. Half-widths of the ion angular distributions in these experiments varied from 6° to 7.5°, corresponding to transverse energies from 0.13 to 0.21 eV. During the course of the experiment, ion energies gradually decreased, probably due to the buildup of contaminants on the chamber walls. Cell wall temperature also was an important variable, with ion fluxes to the lower electrode increasing and the ion angular distribution narrowing as the cell temperature increased.