Compact Degradation Sensors for Monitoring NBTI and Oxide Degradation

We designed two compact in situ NBTI and oxide degradation sensors with digital outputs in 130 nm CMOS. The 308 μm² NBTI sensor and the 150 μm² oxide degradation sensor provide digital frequency outputs and are compatible with a cell-based design methodology without requiring analog supplies. The sensors enable high-volume data collection and monitoring of degradation mechanisms to guide dynamic control schemes and warn of impending device failure. Large scale data-collection permits improved modeling and the potential for insight into the underlying reliability mechanisms. The oxide degradation sensor monitors the change in gate leakage under stress conditions and is the first proposed of its kind. The NBTI sensor is 110× smaller than previous work and is designed to compensate for temperature variations during measurement. A maximum error of 2.2% is observed for the NBTI sensor under process, voltage, and temperature variations. It provides ΔV_th measurement with 3σ accuracy of 1.23 mV from 40° C-110° C.