On the thermal activation of negative bias temperature instability

The temperature dependence of negative bias temperature instability (NBTI) is investigated on 2.0 nm SiO₂ devices from temperatures ranging from 300 K down to 6 K with a measurement window of ~12 ms to 100 s. Results indicate that classic NBTI degradation is observed down to ~200 K and rarely observed at temperatures below 140 K in the experimental window. Since experimental results show the charge trapping component contributing to NBTI is thermally activated, the results cannot be explained with the conventionally employed elastic tunneling theory. A new mechanism is observed at temperatures below 200 K where device performance during stress conditions improves rather than degrades with time, which is opposite to the ¿classical¿ NBTI phenomenon.