Study of Electrical Characteristics on Thermally Nitrided SiO2 (Nitroxide) Films

A significant influence of thermal nitridation on the electrical characteristics of nitroxide films was found in this study. Nitridation at temperatures lower than 1000°C results in a great negative shift of flatband voltage V FB . However, the value of V FB continuously decreases with the increasing of nitridation time at nitridation above 1000°C. After annealing of nitroxide films in N 2 gas at 1000°C for 30 min, a decrease of V FB , compared with the same nitridation conditions, was observed. From quasi‐static C‐V measurements, it shows that not only interface fixed charge Q SS but also surface‐state density N SS are reduced in the decreasing of V FB after annealing the films in N 2 gas. This effect is more prominent for nitridation at lower temperatures; however, there still exists some degree of reduction in V FB for nitridation at higher temperature and longer time. The negative bias‐temperature instability, sometimes called “slow trapping,” is revealed by accelerated aging with negative gate bias at elevated temperatures. It is found that the instability problem is more severe for samples which are nitrided at lower temperatures but N 2 annealing can reduce the negative bias‐temperature instability. After N 2 annealing, nitroxide films prepared with nitridation above 1150°C provide good properties for MOS devices.