Quasi-breakdown in ultra-thin SiO/sub 2/ films: occurrence characterization and reliability assessment methodology
This paper discusses different statistical approaches for the quasi-breakdown phenomenon. In particular, a novel methodology based on the idea that breakdown and quasi-breakdown are competing mechanisms and that they have to be separately analyzed, is developed and well validated for oxide thickness ranging from 3.5 down to 2.5 nm. This methodology is demonstrated to well explain all the quasi-breakdown rate variations with temperature, voltage, area and oxide thickness. Moreover, this new approach enables to rigorously determine the quasi-breakdown acceleration factor with temperature and electric field, which have been found to be different from the breakdown ones. As a result, and confirmed by the difference observed between the obtained time to breakdown and time to quasi-breakdown spreads, the defects at the origin of both phenomena have to be different. Finally, a reliability assessment methodology is presented enabling a proper analysis of both phenomena for reliability evaluation and lifetime prediction.