Intrinsic mechanism of non-linearity in Weibull TDDB lifetime and its impact on lifetime prediction

Anomalous TDDB statistics, i.e., non-linear Weibull plot of TDDB lifetime, has been observed in thick SiO₂ gate dielectrics. Different from the already reported `extrinsic´ mechanisms in thin gate dielectrics such as thickness variation, the mechanism of this new anomalous behavior is `intrinsic´. Just the charging to native and generated defects under the stress induces steep decrease in the defect generation rate, resulting in non-linear Weibull plot. This `intrinsic´ mechanism, charging-induced dynamic stress relaxation effect, prevents us from accurately predicting TDDB lifetimes utilizing the conventional various scaling procedures such as failure rate scaling and area scaling. Therefore, well consideration of this mechanism is crucial for the accurate TDDB lifetime predictions not only in Si devices but also in various compound devices having thick gate dielectrics such as GaN and SiC power devices.