Abstract A semi-empirical profile simulator was employed to better understand fundamental mechanisms of feature evolution in a high aspect ratio contact plasma etch process. Simulation results showed that the net deposition rate of polymer on sidewall defined the necking and surface scattering of ions from the secondary facet caused the formation of bowing. As neutral depositor flux was increased, the resulting profile showed a monotonic increase in necking. In contrast, the extent of bowing showed a maximum, such that minimal bowing was obtained at low and at high depositor fluxes. Primary faceting of photo resist showed only a small influence on the SiO 2 etch profile.