Effect of Annealing Temperature on the Microstructure and Optical Properties of Lanthanum-Doped Hafnium Oxide

Abstract

Lanthanum-doped HfO2 films were deposited on Si by sol–gel technology. The effects of annealing temperature on the optical properties, interface chemistry, and energy band structure of Lanthanum-doped HfO2 films have been investigated. The crystallinity and surface morphologies of the films are strongly dependent on the annealing temperature. X-ray diffraction (XRD) analysis showed a monoclinic phase, and there was a tendency to preferentially grow with increasing temperature. The calculated grain sizes ranged from 17.1 to 22.4 nm on average. It was also confirmed from Raman spectroscopy that increasing the annealing temperature can improve the crystallinity of the films. The surface of the film was smooth, and the film had good interfacial contact with the silicon substrate. The band gap increased from 5.53 to 5.91 eV with increasing annealing temperature. The calculated conduction band offset and valence band offset both exceeded 1 eV. In conclusion, smaller grain size, good crystallinity and interfacial contact can be obtained by adjusting the annealing temperature. Higher conduction band and valence band offsets can meet the minimum barrier height requirements of complementary metal oxide semiconductors (CMOS) and have potential applications.