Time‐dependent breakdown of oxynitride gate dielectrics under unipolar ac stress

Time‐dependent dielectric breakdown under unipolar ac stress is investigated for control, nitrided, and reoxidized nitrided oxides, prepared by rapid thermal processing. All these gate dielectrics show longer time‐to‐breakdown under ac stress compared to constant voltage stress. Nevertheless, the extent of retardation of breakdown under ac stress is observed to be minimum for nitrided oxides and maximum for reoxidized nitrided oxides. Differences in detrapping behavior in these gate dielectrics are used to explain different improvement factors for breakdown under ac stress.