Tuning-Friendly Body Bias Clustering for Compensating Random Variability in Subthreshold Circuits

Post-fabrication tuning for mitigating manufacturing variability is receiving a significant attention. To reduce leakage increase involved in performance compensation by body biasing, body bias clustering methods have been proposed. However, conventional methods suffer from a large test cost for tuning after fabrication, since there are a tremendous number of body bias assignments. We in this paper propose a low-cost tuning scheme after fabrication and present a layout aware body bias clustering method. The proposed method estimates average leakage power after post-fabrication tuning, and minimizes it. We applied the proposed method to ultralow voltage circuits for suppressing their high sensitivity to random Vth variability, and demonstrated the effectiveness of the proposed method. In the experiments, by just introducing two clusters, leakage power after post-fabrication tuning was reduced by up to 70% compared to a single cluster case