Effect of external circuit on the self-bias of capacitively coupled plasma driven by tailored voltage waveforms

Abstract

In this work, the influences of the direct current blocking capacitor, stray capacitance, and stray resistance in the external circuit on the self-bias driven by tailored voltage waveform (TVW)-driven asymmetric capacitive discharges are investigated using a one-dimensional three-velocity particle-in-cell/Monte Carlo collision model coupled with an external circuit. Under a zero-initial-phase sinusoidal TVW drive with an amplitude ratio of 3:2:1, a dc self-bias voltage is generated and can be significantly modulated by the blocking capacitor, stray resistance, and stray capacitance. The approximate adjustment ranges of each external circuit parameter, as well as an optimized combination of circuit parameters under specific discharge conditions are presented. Based on bias control using a single external component, combined control of multiple external circuit parameters enables a wider tuning range of plasma density, ion flux, and ion energy at the boundary. In addition, the mechanisms responsible for the formation of positive and negative self-bias voltages at different pressures are discussed. These results may provide insight and a theoretical reference for the engineering design of bias control in electrical asymmetric capacitively coupled plasma systems.