Estimation of NBTI Degradation using IDDQ Measurement

Negative bias temperature instability (NBTI) has emerged as a major reliability degradation factor in nano-scale CMOS technology. In this paper, we analyze the impact of NBTI degradation in both the maximum operating frequency (f_MAX) and the total standby leakage current (I_DDQ) of digital CMOS circuits. Our analysis shows that due to NBTI, both f_MAX and I_DDQ reduce with time with a fix exponent of 1/6 (~t^1/6). Based on this analysis, we develop temporal f_MAX-I_DDQ model and apply it to several ISCAS´85 benchmark circuits designed using BPTM 70nm file. Results show that f_MAX and I_DDQ can reduce by more than 8% and 30% in 3 years operation time, respectively. Furthermore, we show that f_MAX and I_DDQ degradations are highly correlated throughout the operating lifetime, and using this fact, one can avoid expensive f_MAX testing and predict f_MAX degradations as a function of I_DDQ measures.