NBTI mechanism in ultra-thin gate dielectric - nitrogen-originated mechanism in SiON

Abstract

We have investigated the mechanism of negative bias temperature (NBT) degradation of p/sup +/-gate p-MOSFETs having SiON and SiO/sub 2/ films. As a result, it was found that NBT degradation of SiO/sub 2/ is improved by fluorine incorporation, while no effect is observed in that of SiON, and that the activation energy of NBT degradation in SiON is lower than that in SiO/sub 2/. From these experimental results, it is inferred that nitrogen-originated NBT degradation dominates NBT degradation in SiON. It was also found that non-energetic holes existing in the inversion layer contribute to NBT degradation for both SiON and SiO/sub 2/ films, and that the oxide field is indispensable for NBT degradation.