AVS 63rd International Symposium & Exhibition
    Plasma Science and Technology Thursday Sessions
       Session PS-ThP

Paper PS-ThP27
Modeling of Electron Kinetics in rf Discharges at Low and High Pressures

Thursday, November 10, 2016, 6:00 pm, Room Hall D

Session: Plasma Science and Technology Division Poster Session
Presenter: Ananth Bhoj, ESI US R&D Inc.
Authors: A.N. Bhoj, ESI US R&D Inc.
Z.A. Xiong, ESI US R&D Inc.
V.I. Kolobov, CFD Research Corporation
Correspondent: Click to Email
Low temperature plasmas (LTPs) are used for numerous applications over a wide range of gas pressures from a few mTorr up to ambient pressures (760 Torr). Simulations of LTPs involve the multiphysics coupling of gas flow, heat transfer, plasma physics, volumetric and surface chemistry and electromagnetics. For CAE models like CFD-ACE+, to accurately capture the plasma physics, a kinetic treatment is often important for different plasma species. In particular, while the mean free paths and the energy relaxation lengths for ions and neutrals are similar, they differ vastly for electrons. This memory effect for elastic collisions of electrons with neutrals has a profound influence to electron kinetics. The kinetic treatment for electrons assumes significance because the electron energy distribution function (EEDF) in highly non-Maxwellian in most cases, and the electron-induced reaction rates are sensitive to the tail of the EEDF. At very low pressures, global models that assume diffusion dominated electron transport with conservation of total energy are useful to quickly estimate plasma characteristics and trends in RF systems. In this approach, the EEDF depends on the total electron energy and energy dependence is obtained by spatially averaging the Fokker-Planck (FP) equation for the EEDF. At intermediate pressures, the tail of the EEDF becomes local, whereas the rest of the EEDF remains non-local. In this regime, the isotropic part of the EEDF depends both on energy and space, so nonlocal effects must be explicitly accounted for by solving the FP equation. Such EEDF nonlocality behavior has been shown to extend up to pL = 10 Torr-cm. Beyond this range, fluid models with non-Maxwellian EEDFs based on lookup tables are computationally more efficient and capture the physics well. We show examples of simulations in these various regimes using CFD-ACE+.