The effect of surface quenching coefficients of $O_2(a^{1}{\Delta}g)$ and $O_2(b^{1}{\Sigma}g^{+})$ on capacitively coupled $Ar$/$O_2$ discharge: A global/equivalent circuit model study

TL;DR

This study uses a global model to analyze how surface quenching coefficients of specific oxygen metastables influence plasma characteristics in Ar/O2 discharges, highlighting the importance of both metastables in plasma behavior.

Contribution

It introduces the inclusion of both $O_2(a^{1}{\Delta}g)$ and $O_2(b^{1}{\\Sigma}g^{+})$ metastables into a global model, revealing their combined impact on plasma properties.

Findings

Surface quenching coefficients significantly affect plasma impedance and sheath voltage.

Both metastables play crucial roles, and their effects vary with wall material.

Adjusting quenching coefficients alters particle densities and power absorption.

Abstract

Capacitively coupled discharges operated in mixtures of $Ar$ and $O_2$ are extensively utilized in plasma etching and deposition processes due to the oxidative properties and precursor functionality of the reactive species produced in the discharge. In $Ar$/$O_2$ discharges, the surface quenching coefficient of $O_2(a^{1}{\Delta}g)$ is known to affect this metastable density, which, in turn, affects the electronegativity and other important plasma characteristics. In this work, in addition to $O_2(a^{1}{\Delta}g)$, $O_2(b^{1}{\Sigma}g^{+})$ and its associated reactions are incorporated into a global/equivalent circuit model of an $Ar$/$O_2$ discharge. By independently adjusting the quenching coefficients of both metastable species, changes of these surface coefficients are found to significantly affect the discharge characteristics, indicating that the role of $O_2(b^{1}{\Sigma}g^{+})$ cannot be neglected. The effects of their respective surface quenching coefficients of these metastables based on various wall materials on the discharge are revealed including their effects on different particle species densities, plasma impedance, voltage drops across the sheaths, as well as plasma power absorption.