Reduction of the anomalous VT behavior in MOSFETs with high-kappa/metal gate stacks

Abstract

This study investigates the impact of different nitridation processes on hafnium silicon oxynitride (HfSiON) dielectrics. It is demonstrated that the threshold voltage (V-T vs. L-g) behavior at short gate lengths is strongly impacted by the nitridation process, depending on the Hf/(Hf+Si) ratio and the HfSiON thickness. A Plasma nitridation in oxidizing ambient results in a modification of the dielectric that can explain the anomalous V-T behavior in devices integrated with hafnium-based dielectrics and metal gate. Reduction in anomalous V-T behavior and limited gate leakage is achieved by applying a thermal nitridation in a NH3 ambient on Hf-rich silicon oxynitride.