Enhanced Ferroelectric Properties in Hf0.5Zr0.5O2 Films Using a HfO0.61N0.72 Interfacial Layer

Fluorite structured ferroelectrics, such as (Hf, Zr)O-2, 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 HfO0.61N0.72 interfacial layer between a TiN bottom electrode and a ferroelectric Hf0.5Zr0.5O2 thin film is investigated. The insertion of the 2 nm-thick HfO0.61N0.72 interfacial layer decreases the inclusion of the undesirable non-ferroelectric phase by approximate to 60% and increases the remanent polarization by more than 30%. The reaction barrier property of the sacrificial HfO0.61N0.72 layer significantly enhances the reliability of the Hf0.5Zr0.5O2 film, and thus, improves the endurance of the film beyond 1.5 x 10(11) switching cycles. This is the highest endurance among the reported values for fluorite-structured ferroelectrics with the remanent polarization kept higher than 10 mu C cm(-2).