Mechanism of Gradual Increase of Gate Current in High-K Gate Dielectrics and Its Application to Reliability Assessment

To establish the reliability model of the high-k gate dielectrics in the EOT-scaled regime, the gradual increase of the leakage current during the stress time, which makes the precise detection of the breakdown harder, has been studied. It has been clarified that multiple occurrence of soft breakdown (SBD) at plural local spots is the cause of the gradual increase, along with a large initial leakage current. Based on this mechanism, a model for the gradual increase has been proposed. The proposed multiple SBD-based model gives us a warning that we will obtain inaccurate values of the Weibull slope (beta) and the time to breakdown (T_BD or eta), if we do not take into account this mechanism. To avoid such evaluations, a simple reliability assessment method has been also proposed, which realizes the accurate prediction of the breakdown statistics even without experimental detections of the first breakdown