Charge trapping in thin nitrided SiO2 films

Electron avalanche injection has been used to study electron trapping and positive charge generation in thin (10–30 nm) ammonia-annealed silicon dioxide films as a function of process conditions. It is found that the electron traps induced by nitridation are characterized by a capture cross section of ∼10−16 cm2 and by a density which increases with nitridation temperature and time. These results suggest that the traps are due to the nitrogen itself at oxygen sites. Even though electron traps in conventional oxides enhance the positive charge generation rate, the turn-around effect in nitrided oxides is greatly reduced or completely eliminated under severe nitridation conditions. The process dependence of the turn-around effect suggests that the nitrogen near the interface is mainly responsible for this effect.