Hot carrier enhanced gate current and its impact on short channel nMOSFET reliability with ultra-thin gate oxides

We have investigated hot carrier stress degradation for short channel (100 nm and 80 nm) nMOSFETs with ultra-thin gate oxides (2.5 nm). Under high drain bias, gate current was measured well above that is expected from direct tunneling itself We have found that this hot carrier enhanced gate current mechanism plays a significant role in the degradation of nMOSFETs. The degradation under very accelerated stress bias, where hot carrier enhanced gate current is dominant, was relatively insensitive to stress bias and time, compared to the degradation under low voltage hot carrier stress. Unless properly considered, the additional mechanism can cause the extrapolated lifetime to be overestimated.