Reduction of Annealing Temperature of Hf0.5Zr0.5O2 Thin Films via Deep-Ultraviolet Irradiation

Abstract

Low-temperature deposition of inorganic ferroelectric (FE) thin films is indispensable for realizing flexible inorganic-FE memories. Doped HfO2-based FE thin films commonly require high crystallization temperature (> 450oC), which hinders their growth on flexible substrates. Here we report that the crystallization temperature of the metastable orthorhombic (O-phase) in Hf0.5Zr0.5O2 thin films can be lowered to 350oC via a deep ultraviolet (DUV) irradiation process carried out prior to thermal annealing. The DUV irradiation can initialize a nucleation process of the crystal growth, and the subsequent rapid thermal annealing at 350oC crystallizes the Hf0.5Zr0.5O2 thin film in crystalline O-phase. The DUV-irradiated films annealed at 350oC exhibit the excellent FE characteristics, whereas the non-irradiated films exhibit FE characteristics only above 450oC annealing temperature. Our results suggest that DUV irradiation and photoactivation can lower the crystallization temperature of HZO thin films toward the realization of flexible FE random access memories.