Anomalous width dependence of gate current in high- k metal gate nMOS transistors

Abstract

This letter analyzes the width dependence of gate current observed in nMOS transistors fabricated using the 28-nm gate-first CMOS process. It is experimentally shown that the gate current density is ~10× lower for 80-nm wide high permittivity (K) dielectrics and metal gate nMOS transistors compared with 1-μm wider ones. The physical mechanism responsible for this anomalous width dependence is identified and attributed to the reduction in the average number of positively charged oxygen vacancies present in HfO2 for narrow width transistors.