LOW-ENERGY (3-100 EV) ELECTRON-BOMBARDMENT-INDUCED NITRIDATION OF THIN SIO2-FILMS - PHYSICOCHEMICAL AND ELECTRICAL ANALYSES

Low-energy (3-100 eV) electrons are shown to be efficient promoters of the superficial nitridation of thin SiO2 films grown on boron-doped S i(100) using low pure NH3 pressures (less-than-or-equal-to 2 x 10(-4) mbar) at ambient temperature. The initial concentration (almost-equal- to 10(15) at. CM-3) of ionized acceptors in silicon near the SiO2/Si i nterface is first lowered by the nitridation process and then restored by hydrogen annealing at 450-degrees-C. The ultrahigh vacuum experime ntal set-up permits us to uncouple two important effects from a therma lly-assisted (700-950-degrees-C) r.f. NH3 plasma nitridation process: the role played by low-energy (3-5 eV) electrons and the temperature. It is found that the existence of charged particles near the sample su rface must be taken into account in the plasma reaction process and th at the main effect of thermal activation is to enhance the reaction an d the diffusion of nitrogen species through the SiO2 layer up to the S iO2/Si interface.