Characterizing within-die variation from multiple supply port IDDQ measurements

The importance of within-die process variation and its impact on product yield has increased significantly with scaling. Within-die variation is typically monitored by embedding characterization circuits in product chips. In this work, we propose a minimally-invasive, low-overhead technique for characterizing within-die variation. The proposed technique monitors within-die variation by measuring quiescent (I_DDQ) currents at multiple power supply ports during wafer-probe test. We show that the spatially distributed nature of power ports enables spatial observation of process variation. We demonstrate our methodology on an experimental test-chip fabricated in 65-nm technology. The measurement results show that the I_DDQ currents drawn by multiple power supply ports correlate very well with the variation trends introduced by state-dependent leakage patterns.