Investigating the impact of the defect dynamic characteristics on the PBTI in the high-kappa gate device

摘要

Recent device reliability studies on the metal/high-kappa device observed the inter-convertible characteristics of the electron trap levels between the shallow and deep defect states under cyclic positive-bias temperature stressing. Although the oxygen vacancy and oxygen interstitial defect, being two typical types of defects in the high-kappa oxide, have been criticized as the culprit for the device reliability issue and investigated in many simulations, all results have indicated that the defect levels induced by them were either too shallow or too deep and failed to explain the above experimental observation. Nevertheless, studies on the static characteristics of vacancy-interstitial (V-O-O-i) model showed scattering distributed electron trap levels within the bandgap, making it as a promising defect type that can account for the above experimental observation. In this work, we investigated the dynamic characteristics of the V-O-O-i defect pair under PBTI stress by tuning the relative position of V-O and O-i. Our simulation results show multiple energy barriers for the structure transformation along the O-i migration path, and the charge trap level of the specific defect pair during the O-i migration is shown to be adjustable within the HfO2 band gap, depending on the O-i positions. These results depict an atomic picture to help us understand the defect electrical behavior under cyclic positive bias stress condition.