Analysis of reliability of flip-flops under transistor aging effects in nano-scale CMOS technology

The effect of aging has become an important reliability concern in modern CMOS technology. NBTI and PBTI are known to bring about an increase in threshold voltage of the PMOS and NMOS respectively. This paper studies the effect of NBTI and PBTI on different flip-flop circuits with key parameters such as setup time, hold time, clock to output delay and data to output delay. The results in a predictive 32 nm technology show an increase of 0.43 to 1.23 pico-seconds in data-to-output delay depending on the Flip-Flop type. Moreover, we propose a method to use dual threshold voltage assignment to mitigate the effect of transistor aging on pulse triggered Flip-Flops. Dual Vth results show lower delay as well as 30% reduction in delay aging using the proposed dual threshold voltage method.