The influence of electron temperature on pattern-dependent charging during etching in high-density plasmas

The effect of the electron temperature (T_e) on charging potentials that develop in trenches during plasma etching of high aspect ratio polysilicon-on-insulator structures is studied by two-dimensional Monte Carlo simulations. Larger values of T_e cause the potential of the upper photoresist sidewalls to become more negative; thus, more electrons are repelled back and the electron current density to the trench bottom decreases. The ensuing larger charging potential at the bottom surface perturbs the local ion dynamics so that more ions are deflected towards the polysilicon sidewalk causing (a) more severe lateral etching (notching) and (b) larger gale potentials, thereby increasing the probability of tunneling currents through the underlying gate oxide. The simulation results capture reported experimental trends and offer new insight into the nature of charging damage.