Electrical and physical characterization of remote plasma oxidized HfO2 gate dielectrics

Bi-layer gate stacks consisting of a HfO₂ and an interfacial layer are fabricated by remote plasma oxidation (RPO) of Hf metal deposited on an Si substrate. Hf metal is fully oxidized by the RPO even at a temperature as low as 400°C due to radical oxygens, leading to an improvement in the quality of HfO₂ with less impact to the interfacial layer growth. An insufficient oxidation leads to a deterioration of mobility with increasing interface traps and positive bias temperature instability, which is likely caused by the oxygen vacancies acting as traps induced by the remaining Hf metal. The SiO₂-like interface improves the mobility with reduced interface states. Full oxidation and the controlled SiO₂-like interface demonstrate RPO as a promising way for gate-stack optimization.