Suppression of interface-state generation in reoxidized nitrided oxide gate dielectrics

Abstract

Reoxidized nitrided oxide gate dielectrics are characterized following electrical stress, in order to study the mechanism by which they are able to inhibit interface‐state generation, as compared to silicon dioxide. It is found that the energy spectrum of the few interface states which are generated in reoxidized nitrided oxides differs from that of states generated in lightly nitrided oxides or in silicon dioxide. We have also measured interface‐state generation as a function of stress time and stress polarity for different dielectrics, and observed two characteristic types of fluence dependencies. Interface states which are generated linearly with fluence are modeled using a simple first‐order rate equation, which depends on the density of interface‐state precursor sites. A sublinear fluence dependence is successfully modeled by including the effect of interfacial strain relaxation. Based on these results, we argue that the first type of interface‐state generation, which follows a linear fluence dependence, is suppressed in electrically‐stressed reoxidized nitrided oxides because the interface has fewer defect precursor sites.