Theoretical Screening of Candidate Materials for DRAM Capacitors and Experimental Demonstration of a Cubic-Hafnia MIM Capacitor

To screen candidate materials for dynamic random-access memory capacitors, the tunneling probability at a constant equivalent oxide thickness (EOT) of metal-insulator-metal (MIM) capacitors was theoretically maximized according to a tradeoff between permittivity and band offset. As a result, it was found that cubic HfO₂ with a TiN electrode is a promising candidate. TiN/Al-doped HfO₂/TiN MIM capacitors were fabricated by inserting Al₂O₃ layers for phase control of HfO₂ and for suppression of TiN oxidation. The fabricated capacitors exhibit leakage current of 80 nA/cm² at 1 V and EOT of 0.7 nm. Moreover, the main leakage current was estimated to originate from oxygen vacancies.