Oxygen‐Vacancy‐Regulated Crystallization and Ferroelectric Phase Stabilization in Hf 0.5 Zr 0.5 O 2 Thin Films

Defect‐regulated crystallization pathways govern metastable phase formation in functional oxides, yet the role of oxygen‐vacancy‐related oxygen deficiency in crystallization and ferroelectric phase stabilization in ultrathin Hf 0.5 Zr 0.5 O 2 remains unresolved. This work combines atomic‐layer‐deposition ozone‐dose tuning with temperature‐resolved in situ grazing‐incidence wide‐angle X‐ray scattering reciprocal‐space mapping to track crystallization in 10 nm Hf 0.5 Zr 0.5 O 2 thin films with systematically varied, X‐ray Photoelectron Spectroscopy‐inferred relative oxygen‐deficiency levels. Vacancy‐lean films crystallize at lower temperatures than vacancy‐rich films (370°C vs. 400°C) and exhibit a lower comparative apparent activation energy for crystallization (3.6 × 10 2 vs. 4.4 × 10 2 kJ mol −1 ), together with more efficient lateral crystallite growth and a larger strain‐free d‐spacing consistent with an increased orthorhombic‐phase contribution. In contrast, vacancy‐rich films show delayed crystallization, suppressed lateral coarsening, and stronger tetragonal‐phase retention. The vacancy‐lean film achieves a switchable polarization, 2P r , of 19.9 µC cm −2 after annealing at 400°C, within a back‐end‐of‐line‐relevant thermal budget; higher annealing temperatures induce partial monoclinic transformation and reduce polarization. These results identify oxygen‐deficiency control as a practical route to tune crystallization pathways and low‐temperature ferroelectric phase formation in HfO 2 ‐based thin films.