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

Thick Hafnium-Zirconium oxide (HZO) films (>10 nm) near morphotropic phase boundary (MPB) are promising for high-<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> 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 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∘</sup>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 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∘</sup>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 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∘</sup>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 < κ < 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-κ HZO films near MPB in next-generation flexible electronic systems.