Investigation of the Time-Dependent BTI-induced Degradation Distribution for Ring Oscillators in Ultra-Long-Term Stress Conditions

BTI-induced degradation of 65 nm FDSOI ring oscillators (ROs) was measured using a long-term measurement system. Temperature and supply voltage were set to 125°C and a nominal voltage of 1.2 V, respectively. Over a measurement period of 300 days, the average BTI-induced degradation exhibited a power-law behavior. The frequency distributions of 840 ROs transitioned from a Gaussian distribution at the short time to multiple Gaussian distributions at the long time. This shift is attributed to two distinct degradation mechanisms; defects close to the interface and those in proximity to the gate. Although the averaged BTI-induced degradation follows a power-law function. As stress time increased, RTN-induced frequency variations also increased, which makes the frequency distributions wider as stress time.