Investigation of surface boundary conditions for continuum modeling of RF plasmas

TL;DR

This study examines how different boundary conditions on solid surfaces influence the behavior of RF plasmas in continuum models, highlighting the importance of thermal and diffusion fluxes in plasma-surface interactions.

Contribution

It systematically surveys various boundary conditions and their effects on plasma modeling, emphasizing the significance of fluxes and electric potential interactions.

Findings

Boundary conditions significantly affect sheath and plasma behavior.

Thermal and diffusion fluxes are crucial for accurate modeling.

Pure drift boundary conditions may fail to produce a sheath.

Abstract

This work was motivated by a lacking general consensus in the exact form of the boundary conditions (BCs) required on the solid surfaces for the continuum modeling of RF plasmas. Various kinds of number and energy density BCs on solid surfaces were surveyed and how they interacted with the electric potential BC to affect the plasma was examined in two fundamental RF plasma reactor configurations. A second-order local mean energy approximation with equations governing the electron and ion number densities, and the electron energy density was used to model the plasmas. Zero densities and various combinations of drift, diffusion and thermal fluxes were considered to set up BCs. It was shown that the choice of BC can have a significant impact on the sheath and bulk plasma. The thermal and diffusion fluxes to the surface were found to be important. A pure drift BC for dielectric walls failed to produce a sheath.