SPATIALLY-AVERAGED MODEL FOR PLASMA ETCH PROCESSES - COMPARISON OF DIFFERENT APPROACHES TO ELECTRON KINETICS

A well stirred reactor model determines spatially averaged species com position in a plasma etch reactor by solving conservation equations fo r species, mass, and electron energy distribution function (EEDF). The reactor is characterized by a chamber volume, surface area, mass flow , pressure, power deposition, and composition of the feed gas. The wel l stirred reactor model is increasingly common in the literature due t o its low requirement of computer resources for detailed chemical kine tics calculations. In such plasma etch models, assumptions on the EEDF , which are needed to determine reaction rate coefficients for electro n impact reactions, are crucial for a prediction of steady state condi tions. In this article we focus on a comparison for three different le vels of sophistication with regard to the electron energy distribution function: obtaining the EEDF from a fully coupled solution of species equations and the Boltzmann equation, pre-computing and tabulating th e EEDF for typical reactor conditions, and assuming a Maxwellian EEDF. The influence of these modeling assumptions on the steady state condi tions of the reactor is examined by various parametric studies for a c hlorine plasma. The results clearly indicate limitations of the two si mplified approaches to electron kinetics. To summarize, in this articl e we show the feasibility of a zero-dimensional model which predicts s teady state reactor conditions from a fully coupled solution of Boltzm ann and species equations. (C) 1998 American Vacuum Society.