Microstructure and dielectric properties of La2O3 films prepared by ion beam assistant electron-beam evaporation

Ultrathin La2O3 gate dielectric films were prepared on Si substrate by ion assistant electron-beam evaporation. The growth processing, interfacial structure and electrical properties were investigated by various techniques. From XRD results, we found that the La2O3 films maintained the amorphous state up to a high annealing temperature of 900 °C for 5 min. From XPS results, we also discovered that the La atoms of the La2O3 films did not react with silicon substrate to form any La-compound at the interfacial layer. However, a SiO2 interfacial layer was formed by the diffusion of O atoms of the La2O3 films to the silicon substrate. From the atomic force microscopy image, we disclosed that the surface of the amorphous La2O3 film was very flat. Moreover, the La2O3 film showed a dielectric constant of 15.5 at 1 MHz, and the leakage current density of the La2O3 film was 7.56 × 10−6 A/cm2 at a gate bias voltage of 1 V.