Investigation into trap-assisted tunneling drain leakage current in NMOSFETs

Abstract

The impact of hot carrier stress on drain leakage current becomes more severe in ultra-deep sub-micron NMOSFETs. The mechanisms and characteristics of trap-assisted tunneling drain leakage current ( ITAT ) degradation are investigated. Both interface trap and oxide trapped charge are analyzed. The experimental results show that the hot carrier stress makes ITAT degradation have a strong dependence on the oxide thickness. In thin gate oxide (3.84nm)NMOSFETs, ITAT degradation is attributed mostly to interface trap creation, while in thicker oxide(7.64nm) NMOSFETs, ITAT 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.