M-IVC: Using Multiple Input Vectors to Minimize Aging-Induced Delay

Negative bias temperature instability (NBTI) has been a significant reliability concern in current digital circuit design due to its effect of increasing the path delay with time and in turn degrading the circuit performance. NBTI degradation has strong dependence on input pattern and duty cycles. Based on this observation, we propose to apply multiple input vectors to the combination circuit in a non-uniform way during standby mode. Multiple input vectors can enhance the capability to control the circuit nodes, achieve smaller duty cycles to reduce the stress time of gates and thus mitigate static NBTI. A constrained multi-object optimization model is formalized to find the optimal combination of duty cycles for timing-critical paths, which in turn minimizes the increase of path delay. An ATPG-like procedure is then presented to generate the corresponding input vectors. Experimental results demonstrate that the delay increase of timing-critical paths can be mitigated significantly under long time NBTI effect (10-year) by only applying a small number of vectors.