In2O3/TiN bi-layer electrode for ZrO2-based metal-insulator-metal capacitor

Abstract

This study investigates the improvement of the electrical properties in TiN/ZrO₂/TiN metal–insulator-metal (MIM) capacitors for dynamic random access memory (DRAM) applications through the introduction of In₂O₃. The oxidation potential between the TiN electrode and the ZrO₂ dielectric film induces an oxygen scavenging effect, resulting in the formation of oxygen vacancies within the ZrO₂. This formation of oxygen vacancies severely degrades not only the electrical properties but also the overall performance of MIM capacitors. By introducing of an In₂O₃ buffer layer at the ZrO₂/TiN interface, we effectively reduce oxygen vacancies by supplying oxygen to the ZrO₂ and TiO_xN_y interfacial layer, based on low oxygen vacancy formation energy of In₂O₃. Furthermore, the cubic phase of In₂O₃ induced into a tetragonal phase of ZrO₂. Consequently, the introduction of In₂O₃ increases the capacitance density and leakage characteristic of the MIM capacitor, simultaneously, by enhancing the crystallinity and suppressing the formation of oxygen vacancy in ZrO₂. Eventually, the insertion of 1.5 nm of In₂O₃ significantly improved the leakage current characteristics, achieving a minimum equivalent oxide thickness of 0.75 nm that satisfies the DRAM leakage current density specification (<10⁻⁷ A/cm²) at an applied voltage of + 0.8 V.