Unveiling the Capacitance Overestimation of HfO2-ZrO2 Solid Solution in Morphotropic Phase Boundary

Abstract

Owing to its high process compatibility and exceptionally high dielectric constant (k) at zero bias, the HfO₂–ZrO₂ solid solution near the morphotropic phase boundary (MPB) has been extensively investigated as a promising dielectric material for next-generation dynamic random-access memory (DRAM) capacitors. Despite significant research efforts to apply MPB thin films to DRAM capacitors, conventional electrical characterization methods have critical limitations. Specifically, while the typical operating voltage of DRAM capacitors is approximately 0.8 V, most prior studies have evaluated the dielectric properties under considerably higher voltage ranges, leading to substantial overestimation of capacitance. In this study, we systematically investigated the dielectric properties of MPB thin films within a voltage range of 0.5 V, closely aligned with practical DRAM capacitor operating conditions, and clarified the origin of capacitance overestimation. By employing two consecutive low-voltage sweeps, we suppressed two major sources of capacitance overestimation (dynamic and extrinsic components), enabling the accurate evaluation of feasible k-values relevant to DRAM applications. Furthermore, first-order reversal-curve measurements revealed a correlation between the domain configurations and dielectric performance. Notably, the optimal composition for maximising the k-value differed between the low- and high-voltage measurement regimes. These findings demonstrate that preventing capacitance overestimation and optimising the composition to control the domain configurations are critical steps toward the reliable implementation of MPB thin films in next-generation DRAM devices.