Effect of nitrogen distribution in nitrided oxide prepared by rapid thermal annealing on its electrical characteristics

Very thin oxides in nm range were nitrided by lamp heated rapid thermal annealing in an ammonia ambient. The nitrided oxides were studied using Auger electron spectroscopy, angular resolved x-ray photoelectron spectroscopy, secondary ion mass spectroscopy, and electrical metal–insulator–semiconductor (MIS) characterization. It is found by Auger depth profiling that the thickness of the oxide film does not increase by nitridation. The hydrogen concentration increases monotonically as nitridation proceeds. In the early stages of nitridation, nitrogen piles up at SiOxNy/Si interface and in the final stages it distributes uniformly throughout the film. Fixed charge and interface state densities increase with nitrogen concentration at the interface up to a critical nitrogen concentration (about 9%). Beyond this value, they decrease as nitridation proceeds. Nitrided oxides of the same nitrogen distribution, that were obtained at different nitridation temperatures, show the same electrical MIS characteristics. These results are explained by a model where nitrogen incorporation kinetics and formation of defects relevant to the MIS characteristics are affected by interfacial strain.