THE ROLE OF THE PLASMA IN THE CHEMISTRY OF LOW-PRESSURE PLASMA ETCHERS

A new procedure for the calculation of neutral transport at long mean free paths is applied to describing plasma chemistry in a low neutral pressure high plasma density plasma reactor. The method is based on a novel ''propagator'' technique. The calculation of propagators to allow for various effects such as variable mean free path and anisotropic scattering is demonstrated. The role of the plasma in determining the neutral species behavior is investigated in some detail. The transport to the walls and the recycling of ions and hot neutrals are examined and shown to strongly affect the chemistry. The effects of truncating the hot tail of the electron distribution function and altering the spatial distribution of hot electrons are also calculated, and are shown for the most part to be relatively small provided the power deposition is held constant. The values of sticking coefficients for neutral radicals are shown to have a significant effect. The model results match experimental trends for CF4 and CF3 densities as functions of power, pressure and inlet dow rate variation.