Plasma etching of semiconductor trenches by two processes

Summary form only given. Two-dimensional plasma etching profiles with analytical etch rates are analyzed for a long semiconductor trench with two processes acting concurrently. The first model assumes a linear superposition (series combination) of etch rates for isotropic etching and etching by shadowed chemically activated neutral molecules or radicals. The etch rates for both processes were found previously as exact analytical expressions. Etch profiles appear to be a weighted composite of our previous profiles. The model approximates the diffusion of directed neutrals along the etched surface. The second model treats etching by neutrals and ions where the synergism of the etching by the radicals and the surface activation of the reactants by the ions is described by Langmuir adsorption kinetics. The net etch rate is a parallel combination of the etch rates. The approximate analytical expressions for etch rates of the ions proportional to the ion energy flux and the uniform isotropic etch rates for the neutral radicals already derived are used. The evolution equation for the etch profiles are calculated numerically on MATLAB by integrating three ordinary differential equations for the trajectories. An equation for the slope of the etch profile is a new feature. The models are compared with earlier models that treated diffusion of neutral radicals as well as a series combination of ion and isotropic neutral etch rates.