Low-sensitivity to process variations aging sensor for automotive safety-critical applications

In this paper, circuit failure prediction by timing degradation is used to monitor semiconductor aging, which is a safety-critical problem in the automotive market. Reliability and variability issues are worsening with device scaling down. For safe operation, we propose on-chip, on-line aging monitoring. A novel aging sensor (to be selectively inserted in key locations in the design and to be activated from time to time) is proposed. The aging sensor is a programmable delay sensor, allowing decision-making for several degrees of severity in the aging process. It detects abnormal delays, regardless of their origin. Hence, it can uncover ¿normal¿ aging (namely, due to NBTI) and delay faults due to physical defects activated by long circuit operation. The proposed aging sensor has been optimized to exhibit low sensitivity to PVT (Process, power supply Voltage and Temperature) variations. Moreover, the area overhead of the new architecture is significantly less than the one of other aging sensors presented in the literature. Simulation results with a 65 nm sensor design are presented, ascertaining its usefulness and its low sensitivity, in particular to process variations.