Achieving Morphotropic Phase Boundary at Extremely Low-Temperature (200 °C) in HZO (>10 nm) Films Using Microwave Annealing

Abstract

Thick Hafnium-Zirconium oxide (HZO) films (>10 nm) near morphotropic phase boundary (MPB) are promising for high-k dielectrics in display driving devices and susceptible piezoelectric and temperature sensors. As the demand for flexible systems increases with technological advancements, the overall process temperature must be kept below $400~^{\circ }$ C to be suitable for flexible substrates. However, achieving the MPB in hafnia-based materials generally required higher crystallization temperatures than the deposition temperature (above $300~^{\circ }$ C). In this work, we achieved a high dielectric constant of 39.5 near the MPB in a 15 nm-thick HZO (1:5) film with microwave annealing (MWA) at a temperature of $200~^{\circ }$ C. MWA-treated HZO films present a higher dielectric constant and a lower leakage current density at a low electric field than the furnace-treated, despite the much shorter annealing time (1 min) than the furnace (60 min). Grazing incidence X-ray diffraction (GIXRD) analysis revealed that the m-phase ( $20\lt \kappa \lt 25$ ) proportion is lower in MWA (5.2%) than in the furnace (9.8%). Also, transport mechanism analysis demonstrated that MWA (0.82 eV) shows a higher Schottky barrier height than the furnace (0.75 eV), resulting in lower current density at low electric fields. This study presents a promising approach for employing high- $\kappa $ HZO films near MPB in next-generation flexible electronic systems.