Effect of nitrogen profile on electrical characteristics of ultrathin SiO2 films nitrided by RTP

Rapid thermal nitridation and reoxidation of thin films of SiO2 can significantly reduce the generation of electron traps during high field injection and enhance the charge to breakdown. This improvement is particularly relevant for the fabrication of EEPROMs with a high endurance. Our study is an attempt to explain these observations by correlating the influence of technological parameters on charge trapping and breakdown of ultrathin oxynitride films with the nitrogen profile as measured by secondary ion mass spectroscopy (SIMS). We show that the main factor for improving charge to breakdown of these films is the nitrogen concentration at the silicon-oxide interface rather than the total dose of nitrogen introduced into the oxide during the nitridation step. This substantiates the results obtained previously by measurements of the oxidation resistance of this interface.