The role of nitrogen incorporation in Hf-based high-k dielectrics: reduction in electron charge traps

The N incorporation effect in Hf-based high-k gate dielectrics has been studied by the first-principles calculations. Interactions between N atoms and oxygen vacancies (Vos) in HfO₂ are investigated. Our calculations show that N atoms favorably occupy nearest neighbor oxygen sites to Vos. As a result, electron charge traps at Vos are remarkably suppressed due to the strong repulsive Coulomb interactions between electrons and negatively charged N^3- ions. These results indicate that N incorporation improves positive bias temperature instability (PBTI) in Hf related high-k gate stacks. Moreover, our calculations have also revealed that the Vo formation energy is remarkably reduced by N incorporation.