NITRIDATION OF THIN SIO2-FILMS INDUCED BY LOW-ENERGY (3-100 EV) ELECTRON-BOMBARDMENT

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 (< 10(-1) mbar) at ambient tempera ture. The initial active boron concentration in silicon (approximately 10(15) cm-3) is first lowered near the SiO2/Si interface by the nitri dation process and then restored by a hydrogen annealing at 450-degree s-C. The ultra-high vacuum experimental set-up permits us to uncouple two important effects from a thermally-assisted RF NH3 plasma nitridat ion process : the role played by low energy (3-5 eV) electrons and the temperature. It is found that the presence of electrons near the samp le surface must be taken into account in the plasma reaction process a nd that the main effect of thermal activation is to enhance the reacti on and the diffusion of nitrogen species through the SiO2/Si interface .