Disparity between current and voltage driven capacitively coupled radio frequency discharges
Sebastian Wilczek, Jan Trieschmann, Julian Schulze, Donkó, Zoltán, Ralf Peter Brinkmann
Plasma Sources Science and Technology, Accepted Manuscript online 2 October 2018 https://doi.org/10.1088/1361-6595/aae5c1
In simulation as well as analytical modeling studies of low-pressure capacitively coupled radio frequency (CCRF) discharges, the assumption of both a driving voltage source and a driving current source is commonly used. It is unclear, however, how and to what extent the choice of the mode of driving, that prescribes either a sinusoidal discharge voltage or a sinusoidal discharge current, itself defines the discharge dynamics that results from these studies. To address this issue, 1d3v cylindrical Particle-In-Cell/Monte Carlo collisions (PIC/MCC) simulations of asymmetric capacitively coupled radio frequency discharges are performed in the low pressure regime ($p<2$ Pa). We study the nonlocal and nonlinear dynamics of these discharges on a nanosecond timescale. We find that the excitation of the plasma series resonance (PSR) in the voltage driven case strongly enhances the nonlinear electron power dissipation. However, this resonance is suppressed when a current source is used, because the excitation of harmonics in the RF current is not allowed. Consequently, significant differences between both driving sources are observed in the plasma density as well as in the electron and the power coupling dynamics. We conclude that caution is advised in comparisons between simulations and experiments, as in the former the discharge dynamics is partly defined by the method of driving of the plasma source, while in the latter the addressed resonance phenomena are inherently present at low pressures.