Effect of Annealing Temperature on the Structure and Properties of La 2 O 3 High-K Gate Dielectric Films Prepared by the Sol-Gel Method.

This article presents the sol-gel method for depositing La₂O₃ thin films on n-type Si substrates and quartz substrates, and investigates the impact of annealing temperature on the microcomposition, surface morphology, optical properties, and band characteristics of the films. X-ray diffraction (XRD) analysis indicates that the films are amorphous below 500 °C, with annealing resulting in a hexagonal-phase La₂O₃ (h-a₂O₃) and new non-hydrated impurities. Fourier-transform infrared (FTIR) analysis reveals that the prepared La₂O₃ film is unaffected by moisture. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) provide evidence that the La₂O₃ film has a smooth, uniform surface without cracks. The roughness increases from 0.426 nm to 1.200 nm, and the film thins from 54.85 nm to 49.80 nm as the annealing temperature rises. The film's transmittance is above 75%, as measured by UV-Vis, and the calculated optical bandgap increases from 5.11 eV to 5.75 eV. The calculated band offset of the La₂O₃ film is greater than 1 eV, which meets the minimum requirements for MOS devices, thus providing promising prospects for La₂O₃ films in MOS applications. [ABSTRACT FROM AUTHOR]