Process dependence of hole trapping in thin nitrided SiO2 films

A systematic investigation of hole trapping in 20-30- mu m nitrided oxides as a function of the nitridation conditions was performed using the avalanche injection technique. Nitridation carried out at relatively low temperatures (700-800 degrees C) and/or for short times brings about an increase of hole traps. Hole trapping reduction can only be achieved for more severe nitridation conditions. A correlation between the reduction of hole trapping and the formation of an oxygen-rich layer near the silicon interface is suggested. The effect of postnitridation annealing treatments both in nitrogen and in oxygen was also studied. Heavy reoxidation after nitridation is necessary to bring about a further reduction of the hole trap density.