Theory and Experiments of the Impact of Work-Function Variability on Threshold Voltage Variability in MOS Devices

A model for work-function variability (WFV) based on grain orientation differences of the polycrystalline metal gate is proposed, and the impact of the WFV on device and circuit performance is investigated. The model predicts that the WFV will surpass random dopant fluctuation beyond the 22-nm technology node and become the dominant factor to significantly increase static RAM failure probabilities. The prediction is verified through experimental characterization and analysis.