Studies of Electron-Molecule Collisions in Semiconductor Processing Plasmas

Abstract

In the plasmas used in semiconductor fabrication, collisions between electrons and polyatomic molecules produce reactive fragments that drive etching and other processes at the wafer surface. Extensive and reliable data on electron-molecular collisions are therefore essential to simulations of plasma reactors. For the low electron energies and polyatomic gases (e.g., C_2F_6C_4F_8) that are of interest, both measurements and calculations are difficult, and many needed cross sections are lacking. However, rapid advances in computer speeds now make such calculations feasible. Because the fastest computers are highly parallel, both a formulation that accounts well for the physics of low-energy collisions and an implementation that is efficient on parallel architectures are required. We will give an overview of our formulation of the electron-molecule collision problem and of its implementation for parallel machines, and of some results of its application that will illustrate the progress we have made in studying polyatomic gases of interest to the semiconductor industry.