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

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.