Aging-aware standard cell library design

Transistor aging, mostly due to Bias Temperature Instability (BTI), is one of the major unreliability sources at nano-scale technology nodes. BTI causes the circuit delay to increase and eventually leads to a decrease in the circuit lifetime. Typically, standard cells in the library are optimized according to the design time delay, however, due to the asymmetric effect of BTI, the rise and fall delays might become significantly imbalanced over the lifetime. In this paper, the BTI effect is mitigated by balancing the rise and fall delays of the standard cells at the excepted lifetime. We find an optimal tradeoff between the increase in the size of the library and the lifetime improvement (timing margin reduction) by non-uniform extension of the library cells for various ranges of the input signal probabilities. The simulation results reveal that our technique can prolong the circuit lifetime by around 150% with a negligible area overhead.