Effect of plasma N2 and thermal NH3 nitridation in HfO2 for ultrathin equivalent oxide thickness

Abstract

Two methods of HfO2 nitridation including plasma N2 nitridation and thermal NH3 anneal were studied for ultrathin HfO2 gate dielectrics with <1 nm equivalent oxide thickness (EOT). The detailed nitridation mechanism, nitrogen depth profile, and nitrogen behavior during the anneal process were thoroughly investigated by XPS and SIMS analysis for the two types of nitridation processes at different process conditions. Intermediate metastable nitrogen was observed and found to be important during the plasma nitridation process. For thermal NH3 nitridation, pressure was found to be most critical to control the nitrogen profile while process time and temperature produced second order effects. The physical analyses on the impacts of various process conditions are well correlated to the electrical properties of the films, such as leakage current, EOT, mobility, and transistor bias temperature instability.