MOSFET drain current reduction under Fowler-Nordheim and channel hot carrier injection before gate oxide breakdown

We studied the degradation of MOSFETs with 3.2 nm gate oxide under Fowler-Nordheim and channel hot carrier injection, focusing on the evolution of the characteristics before the occurrence of any oxide breakdown, soft or hard. In order to assess the damage and understand its origin, we monitored different parameters: transfer and output characteristics, gate leakage, charge pumping current, and low frequency noise. After both types of stress, the MOSFETs showed a substantial drop of the transconductance accompanied by a moderate increase of the threshold voltage and a reduction of the drain saturation current. At the same time we observed the increase of the gate leakage current , charge pumping current, and 1/f noise. We interpreted these results in terms of slow and fast interface-trap creation in the gate oxide, highlighting the correlation between the defects responsible for the different degradations observed. In particular we linked the SILC generation to the low frequency noise increase. Finally we tried to recover the damage by injecting electrons across the oxide at moderate field, reducing only SILC and 1/f noise in this way.