Depopulation kinetics of electron traps in thin oxynitride films

This work reports both experimental and theoretical results of the depopulation kinetics of electron traps in silicon oxides annealed in ammonia ambient at a temperature of 1050°C for 30, 60, or 180 min. Results show a significant modification of the spatial and energy distribution of traps in oxynitride after employing a heavy nitridation. Specifically, we found that sample with longer annealing duration has large depopulation rate and is more sensitive to the electric field than the sample with a shorter period of annealing. In addition, the nitrided oxides were found to have only a small percentage of traps with shallow energy levels (< 1 eV) and the percentage remains fairly unchanged for different nitridation conditions. However, the deeper traps (> 1 eV) increase significantly as the nitridation proceeds. By considering the re-trapping effect and the spatial and energy distributions of traps, a new depopulation theory of the electron traps in thin oxynitride is developed and most of the experimental observations can be explained with the present model.