Ion energy distribution at an r.f.-biased electrode in an inductively coupled plasma affected by collisions in a sheath

Abstract

Ion energy distributions (IEDs) at an r.f.-biased electrode in an inductively coupled plasma-etching chamber were measured by an r.f. floating ion energy analyzer (IEA) with a quadrupole mass spectrometer (QMS). For ArO 2 plasma, the IEDs of Ar + and O 2 + could be qualitatively explained by a model calculation that included charge exchange collisions in the sheath. On the other hand, the IED of O + could not be explained by the model. However, if we assume that a fast O + was generated from a fast O 2 + in the sheath, the measured O + IED can be qualitatively explained. For ArC 3F 8 plasma, CF + and CF 2 + IEDs also could not be explained by the simple charge exchange model, but if we assume that both a fast CF + and a fast CF 2 + were generated from fast CF 3 + in the sheath, the measured IEDs can be qualitatively explained.