Ultra-thin Gate Oxide Lifetime Projection and Degradation Mechanism beyond 90 nm CMOS Technology

In this work, the ultra-thin oxide (Tox=1.6 nm, named as core oxide) and thick oxide (Tox=5.2 nm, named as input/output, IO oxide) lifetime projection and comparison for nFET and pFET under inversion mode stress were investigated. The lifetime of core pFET is worse than that of core nFET, this is opposite to the behavior of their stress leakage current comparison. Nevertheless, the lifetime of IO nFET is worse than that of IO pFET, this is consistent with the behavior of their stress leakage current comparison. In addition, the core pFET possesses smaller exponent n value and TBD comparing with core nFET. In order to investigate this phenomenon, core pFET with substrate bias Vbs is applied to support the proposed mechanism. Presumably due to the larger anode hole current and more hydrogen proton release events result in the core pFET oxide revealing smaller exponent n value, smaller TBD, smaller lifetime prediction and more progressive BD phenomenon than those of core nFET oxide under inversion mode stress.