Endurance Enhancement in Hafnia-Based Ferroelectric Capacitor Through Anti-Ferroelectric Zirconia Seed Layer for Memory Applications

In this work, the ferroelectric (FE) Hf0.5Zr0.5O2 (HZO) capacitor with a novel anti-ferroelectric (AFE) ZrO2 seed layer is thoroughly investigated for memory applications, by comparing with both HZO capacitors without seed layer and with O-phase-dominated ZrO2 seed layer. A fully vacuum-sealed system is used for device fabrication to mitigate the interfacial defects during the material growth process, and the process conditions are carefully optimized. Experimental results demonstrated that the ZrO2-based seed layer can enhance ferroelectricity of the HZO capacitor, and the T-phase-dominated ZrO2 seed layer can further largely enhance the endurance to more than $10^{9}$ without ferroelectricity penalty. Detailed analysis are further performed and demonstrated that the enhanced performance is resulted from the significantly suppressed M-phase ratio and oxygen vacancies. The T-phase dominated ZrO2 seed layer results in only 3.7% M-phase ratio in HZO and 12% reduction of trap charge density compared with conventional FE capacitors. Moreover, the slower leakage current growth rate in the interface also helps the endurance improvement in the proposed design, indicating its great potential for high reliable FeRAM application.