Space and phase resolved electron energy distribution functions in anindustrial dual-frequency capacitively coupled radio-frequency discharge

摘要

The excitation dynamics in a confined dual-frequency plane parallel CCRF discharge (Exelan, Lam ResearchInc.) is investigated by phase resolved optical emission spectroscopy. The emission from different rare gas linesin a He-O2 plasma with small rare gas admixtures is measured during one low frequency RF-cycle resolving thedynamics within every high frequency cycle with one dimensional spatial resolution along the discharge axis. Atime dependent model, based on rate equations, is developed, that describes the dynamics of the populationdensity of excited levels. Based on this model and the comparison of the excitation of various rare gas states,with different excitation thresholds, time and space resolved electron temperature and propagation velocity ofthe high energetic, directed electrons, accelerated at the sheath edge, are determined. These parameters revealthe time and space resolved electron energy distribution function. The qualitative temporal and spatialdistribution of the density of the high energetic electrons is also derived.