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 degrees 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 degrees 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 degrees 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 < kappa < 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.