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 th at develop in trenches during plasma etching of high aspect ratio poly silicon-on-insulator structures is studied by two-dimensional Monte Ca rlo simulations. Larger values of T-e cause the potential of the upper photoresist sidewalls to become more negative; thus, more electrons a re repelled back and the electron current density to the trench bottom decreases. The ensuing larger charging potential at the bottom surfac e perturbs the local ion dynamics so that more ions are deflected towa rds the polysilicon sidewalls causing (a) more severe lateral etching (notching) and (b) larger gate potentials, thereby increasing the prob ability of tunneling currents through the underlying gate oxide. The s imulation results capture reported experimental trends and offer new i nsight into the nature of charging damage. (C) 1997 American Institute of Physics.