Interfacial Layer Selection Methodology for Customized Ferroelectric Memories

This study presents a material selection strategy for the interfacial layer (IL) in ferroelectric (FE) memory stacks. The nucleation-limited switching (NLS) model was applied to analyze the switching kinetics of the metal/FE/insulator/metal (MFIM) structure, where Hf $_{\text{0.5}}$ Zr $_{\text{0.5}}$ O $_{\text{2}}$ (HZO) was used as the FE. Activation field ( $\textit{E}_{\textit{a}}$ ) and characteristic switching time ( $\tau$ ) were extracted for various 1-nm-thick ILs, including those of SiO $_{\text{2}}$ , La $_{\text{2}}$ O $_{\text{3}}$ (LaO), AlN, and Hf $_{\text{3}}$ N $_{\text{4}}$ (HfN). The adaptation of HZO/LaO reduced the $\textit{E}_{\textit{a}}$ by $\sim$ 44% in relation to that of HZO without an IL (MFM-HZO), resulting in considerably faster switching in the low-electric-field ( E ) region ( $<$ 4 MV $\cdot$ cm $^{-\text{1}}$ )—a highly suitable criterion for applications in 1-bit nonvolatile memories. In contrast, HZO/AlN showed the broadest $\tau$ distribution due to the large $\textit{E}_{\textit{a}}$ ( $\sim$ 200% of MFM-HZO), which led to the stabilization of multiple-intermediate polarization states. Promising potentiation and depression characteristics were obtained for multibit synapse applications when an incremental pulse time scheme with a step size of 10 ns was used.