Band energy and electronic behavior of HfO2 on In2O3 thin films enhanced by oxygen annealing

Abstract

This study investigated the band alignment and material properties of HfO2 on In2O3 after oxygen annealing. HfO2 and In2O3 samples were deposited using plasma-enhanced atomic layer deposition and subjected to oxygen annealing. The samples were then characterized using x-ray diffraction, transmission electron microscopy, x-ray photoelectron spectroscopy, reflection electron energy loss spectroscopy, ultraviolet photoelectron spectroscopy, inverse photoemission spectroscopy, and conductive atomic force microscopy. During the plasma-enhanced atomic layer deposition of HfO2 on In2O3, oxygen-deficient In2O3 regions were formed at the HfO2/In2O3 interface. These regions were healed in the presence of O2 during annealing. XPS depth profile analysis revealed an increase in interfacial oxygen concentration with the rise in annealing temperature. The conduction and valence band offsets (ΔEC and ΔEV) between HfO2 and In2O3 were determined to be 1.6 and 0.7 eV, respectively, while interfacial defect states were identified at approximately 1.3 eV above the In2O3 valence band. Additionally, the increased prominence of the higher-energy In 3d5/2 peak (444.8 eV) after annealing indicates a reduction in interfacial defect density. These results indicate that oxygen annealing not only mitigates interfacial defects but also significantly reduces oxide leakage current, making it a promising approach for developing high-performance and thermally stable HfO2 gate dielectrics in In2O3-based integrated circuit applications.