The Electrode-Ferroelectric Interface as the Primary Constraint on Endurance and Retention in HZO-Based Ferroelectric Capacitors

Ferroelectric hafnium-zirconium oxide is one of the most relevant CMOS-compatible materials for next-generation, non-volatile memory devices. Nevertheless, performance reliability remains an issue. With TiN electrodes (the most reported electrode material), Hf-Zr-based ferroelectric capacitors struggle to provide reliable retention due to electrode-ferroelectric interface interactions. Although Hf-Zr-based ferroelectric capacitors are fabricated with other electrodes, the focus is predominantly directed toward obtaining a large ferroelectric response. The impact of the electrodes on data retention for these ferroelectrics remains underreported and greater insight is needed to improve device reliability. Here, a comprehensive set of electrodes are evaluated with emphasis on the core ferroelectric memory reliability metrics of endurance, retention, and imprint. Metal-ferroelectric-metal capacitors comprised of a Hf0.5Zr0.5O2 layer deposited between different combinations of nitride (TiN, TiAlN, and NbN), pure metal (W), and oxide (MoO2, RuO2, and IrO2) top and bottom electrodes are fabricated for the investigation. From the electrical, physical, and structural analysis, the low reactivity of the electrode with the ferroelectric is found to be key for improved reliability of the ferroelectric capacitor. This understanding of interface properties provides necessary insight for the broad implementation of Hf-Zr-based ferroelectrics in memory technology and, overall, boosts the development of next-generation memories.