Simulation of ion energy distributions in Ar/CH4 rf discharges with ion extraction

Abstract

Capacitive radio-frequency discharges in argon–methane gas mixture are used for hydrocarbon deposition on substrates. Ion energy distributions (IEDs) are important for the physics in such discharges. One diagnostics for obtaining IEDs is the energy resolved mass spectrometry. A one-dimensional particle-in-cell code has been used to give better insight into the principle of operation of the ion extraction to interpret more exactly the measured IEDs at the powered electrode. The effects of the ion transfer optics and the modulation effects of the potential between the aperture and ion extractor lens have been studied. A better match between simulation and experiment is achieved by introducing an effective drift length for the ion optics. However, problems remain for reactive species like hydrocarbons indicating more complex plasma reactions within the mass spectrometer.