Effects of Al concentration and annealing method on crystalline and ferroelectric properties of Al:HfO ₂ thin films

Abstract Flash lamp annealing (FLA) and rapid thermal annealing (RTA) were comparatively investigated to clarify their effects on the crystallinity and ferroelectric properties of Al-doped HfO2 (HAO) thin films. HAO films with an Al concentration of 0–12% were deposited by atomic layer deposition and crystallized using either FLA or RTA. Grazing-incidence X-ray diffraction revealed that FLA induces stronger in-plane tensile stress in the HAO layer than RTA by suppressing stress relaxation in the TiN electrode during millisecond-scale ultrafast heating. This stress promotes the ferroelectric orthorhombic phase while suppressing the monoclinic phase. Electrical measurements showed that FLA-treated films exhibited higher remanent polarization than RTA-treated films. Under FLA, both crystallinity and polarization peaked at an Al concentration of 2%, whereas higher Al concentrations suppressed crystallization and ferroelectricity. These results indicate that FLA is an effective low-thermal-budget annealing method for high-performance HAO films with optimized Al concentration.