Effects of a SiO₂ buffer layer on the flatband voltage shift of La₂O₃ gate dielectric grown by using remote plasma atomic layer deposition

Abstract

In this study, the physical and the electrical properties of La₂O₃ with and without a SiO₂ buffer layer deposited by using remote plasma atomic layer deposition were investigated. A 1-nm-thick SiO₂ buffer layer was grown on Si (100) substrates by rapid thermal annealing (RTA). The chemical bonding states at the interface between the La₂O₃ films and both Si and SiO₂/Si substrates were analyzed using X-ray photoelectron spectroscopy (XPS). From the XPS results, the relative intensities of the La-silicate peaks of the La₂O₃ film deposited on the Si substrate were higher than those of the La₂O₃ film deposited on the SiO₂ buffer layer. The electrical properties of the films were studied by generating capacitance-voltage and current-voltage curves. The flatband voltage (V _FB ) for the 4-nm and the 7-nm-thick La₂O₃ films on the Si substrate were −0.86 V and −0.93 V, respectively. On the other hand, the V _FB values for the 4-nm and 7-nm-thick La₂O₃ films on the SiO₂ buffer layer were −0.73 V and −0.49 V, respectively.