Online Circuit Reliability Monitoring

In this work we propose an online reliability tracking framework that utilizes a hybrid network of on-chip temperature and delay sensors together with a circuit reliability macromodel. We are concerned specifically with NBTI-induced transistor aging, which manifests itself as the gradual increase of PMOS threshold voltage and increase of circuit delay over time. The key feature of our work is an explicit macromodel which maps operating temperature to circuit degradation. The macromodel allows for cost-effective reliability tracking. The accuracy of the model is improved by online calibration of model parameters via monitoring the delay degradation of ring oscillators. The number of model parameters is relatively small. For example, in ISCAS'85 benchmark circuits, at most 21 parameters are required for the macromodel. The prediction of circuit degradation using our online monitoring strategy can be up to 20% less conservative compared to the worst-case reliability prediction.