The influence of the secondary electron induced asymmetry on the Electrical Asymmetry Effect in capacitively coupled plasmas

TL;DR

This paper explores how secondary electron asymmetry influences the electrical asymmetry effect in capacitive plasmas, revealing a non-linear interaction that can enhance control over plasma characteristics.

Contribution

It investigates the combined impact of the Electrical Asymmetry Effect and Secondary Electron Asymmetry Effect in dual-frequency capacitive plasmas with different electrode materials, showing their non-linear interaction.

Findings

Superposition of EAE and SEAE is non-linear.

Combining effects enlarges control over dc self-bias.

Enhanced control of mean ion energy achieved.

Abstract

In geometrically symmetric capacitive radio-frequency plasmas driven by two consecutive harmonics a dc self-bias can be generated as a function of the phase shift between the driving frequencies via the Electrical Asymmetry Effect (EAE). Recently the Secondary Electron Asymmetry Effect (SEAE) was discovered (T. Lafleur, P. Chabert and J.P. Booth, J. Phys. D: Appl. Phys. 46 135201 (2013)): unequal secondary electron emission coefficients at both electrodes were found to induce an asymmetry in single frequency capacitive plasmas. Here, we investigate the simultaneous presence of both effects, i.e. a dual-frequency plasma driven by two consecutive harmonics with different electrode materials. We find, that the superposition of the EAE and the SEAE is non-linear, i.e. the asymmetries generated by each individual effect do not simply add up. The control ranges of the dc self-bias and the mean ion energy can be enlarged, if both effects are combined.