Investigation into trap-assisted tunneling drain leakage current in NMOSFETs

The impact of hot carrier stress on drain leakage current becomes more severe in ultra-deep submicron NMOSFETs. The mechanisms and characteristics of trap-assisted tunneling drain leakage current (I_TAT) degradation are investigated. Both interface trap and oxide trapped charge are analyzed. The experimental results show that the hot carrier stress makes I_TAT degradation have a strong dependence on the oxide thickness. In thin gate oxide (3.84 nm) NMOSFETs, Itat degradation is attributed mostly to interface trap creation, while in thicker oxide (7.64 nm) NMOSFETs, I_TAT exhibits two stages degradation, a power law degradation rate in the initial stage due to interface trap generation, followed by an accelerated degradation rate in the second stage caused by oxide trapped charge creation.