The relevance of deeply-scaled FET threshold voltage shifts for operation lifetimes

In nm-sized FET devices with just a few gate oxide defects, the typically measured threshold voltage shifts are not obviously correlated with the device behavior at high gate bias. The largest shifts observed at the threshold voltage after the capture of a single carrier are reduced at higher gate biases. This degradation-mitigating effect is further shown to be amplified at lower channel doping. The understanding gained from 3D numerical simulations is captured in a simple analytic description of a single trapped-charge impact on the FET characteristics in the entire gate bias range. Potential use is illustrated in an improved lifetime projection and in circuit simulations of time-dependent variability.