Enhanced Ferroelectric Properties in Hf_0.5Zr_0.5O₂ Films Using a HfO_0.61N_0.72 Interfacial Layer

Fluorite structured ferroelectrics, such as (Hf, Zr)O₂, attract much interest due to their scalability and compatibility with complementary metal-oxide semiconductors, which make them superior to the conventional ferroelectrics. However, their reliability issues, including their limited endurance, are yet to be resolved. Such issues have been reported to be strongly correlated to the formation and drift of oxygen vacancies concentrated in the interfacial region adjacent to TiN electrodes. In this study, the effect of inserting a sacrificial HfO_0.61N_0.72 interfacial layer between a TiN bottom electrode and a ferroelectric Hf_0.5Zr_0.5O₂ thin film is investigated. The insertion of the 2 nm-thick HfO_0.61N_0.72 interfacial layer decreases the inclusion of the undesirable non-ferroelectric phase by ≈60% and increases the remanent polarization by more than 30%. The reaction barrier property of the sacrificial HfO_0.61N_0.72 layer significantly enhances the reliability of the Hf_0.5Zr_0.5O₂ film, and thus, improves the endurance of the film beyond 1.5 × 10¹¹ switching cycles. This is the highest endurance among the reported values for fluorite-structured ferroelectrics with the remanent polarization kept higher than 10 µC cm^-2.