Anomalous Width Dependence of Gate Current in High- Metal Gate nMOS Transistors

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.