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

This study investigates the impact of different nitridation processes on hafnium silicon oxynitride (HfSiON) dielectrics. It is demonstrated that the threshold voltage (VT vs. Lg) 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 VT behavior in devices integrated with hafnium-based dielectrics and metal gate. Reduction in anomalous VT behavior and limited gate leakage is achieved by applying a thermal nitridation in a NH3 ambient on Hf-rich silicon oxynitride.