Leveraging existing power control circuits and power delivery architecture for variability measurement

Abstract

Embedded test structures are increasingly being used to measure and analyze performance and power variations in product chips to better understand the impact of process variations. In this work, we propose a minimally-invasive, low-overhead technique for characterizing within-die and die-to-die leakage variation. The proposed technique leverages existing power control circuitry added by designers to reduce the power consumption of inactive functional units. We manipulate these ‘sleep islands’ to isolate and measure their leakage current contribution to the chip-wide leakage current. The measured set of sleep island leakage currents reflect the leakage current variation across the chip at a coarse level of resolution. In order to improve resolution, we propose a multiple power supply port (MSP) measurement technique to provide ‘within-island’ leakage current measurements. A calibration technique is described that corrects for differences between the sleep island and MSP approaches, effectively enabling the same information to be obtained using either technique. We demonstrate the techniques on a set of test chips fabricated in 65-nm SOI technology. The results show that leakage current variations across a small test structure array have both a locally random and globally deterministic component that can be accurately mapped using the sleep island or MSP approaches.