Effects of N distribution on charge trapping and TDDB characteristics of N2O annealed wet oxide

Wet pyrogenic oxide of different thicknesses was annealed in N2O ambient an d the N concentration in the films was studied by using SIMS (Secondary ion mass spectroscopy). It was found that for a certain annealing time and tem perature, the N concentration (at %) increases with decreasing the wet oxid e thickness and the location of the peak of N is observed near the interfac e of nitrided Oxide and Si substrate. On the contrary, after nitridation th e concentration of H is higher in the thicker wet oxide of thickness 100 An gstrom and also does not change much from the surface to the interface, For the thinner wet oxide of thickness 40 Angstrom, the concentration of H is less and decreases toward the interface. Gate dielectrics were characterized using high-frequency and quasi-static m easurements. After a constant current stress, a large distortion was observ ed for the N2O annealed wet oxide of 98 Angstrom whereas for the N2O anneal ed wet oxide of 51 Angstrom the distortion was small. With increasing stres sing time, hole trap is followed by electron trapping for the wet oxide of 98 Angstrom whereas for the N2O annealed wet oxide of 51 Angstrom, hole tra pping increases a little at the beginning and then saturates. From the TDDB characteristics, a longer t(BD) was observed for N2O annealed wet oxide of 51 Angstrom compared to 98 Angstrom. From the experimental results, it can be suggested that the improved reliability of thin gate oxide is due to th e large amount of N concentration near the interface only. Hence for the de vice fabrication process, if the wet oxide is nitrided in N2O ambient, the reliability of gate oxide will be improved in the ultrathin region.