Self-bias voltage formation and charged particle dynamics in multi-frequency capacitively coupled plasmas

TL;DR

This study investigates how electrode surface properties influence self-bias voltage formation and particle dynamics in multi-frequency capacitively coupled plasmas using simulations and modeling.

Contribution

It introduces a detailed analysis of how electron reflection and secondary electron yield affect plasma asymmetry and self-bias voltage in multi-frequency RF plasmas.

Findings

Electron reflection slightly affects discharge asymmetry.

Secondary electrons significantly influence plasma asymmetry.

Asymmetry varies with phase angle and number of harmonics.

Abstract

In this work, we analyze the creation of the discharge asymmetry and the concomitant formation of the DC self-bias voltage in capacitively coupled radio frequency plasmas driven by multi-frequency waveforms, as a function of the electrode surface characteristics. For this latter, we consider and vary the coefficients that characterize the elastic reflection of the electrons from the surfaces and the ion-induced secondary electron yield. Our investigations are based on Particle-in-Cell/Monte Carlo Collision simulations of the plasma and on a model that aids the understanding of the computational results. Electron reflection from the electrodes is found to affect slightly the discharge asymmetry in the presence of multi-frequency excitation, whereas secondary electrons cause distinct changes to the asymmetry of the plasma as a function of the phase angle between the harmonics of the driving voltage waveform and as a function the number of these harmonics.