Effects of a SiO _2 buffer layer on the flatband voltage shift of La _2O _3 gate dielectric grown by using remote plasma atomic layer deposition

摘要

In this study, the physical and the electrical properties of La _2O _3 with and without a SiO _2 buffer layer deposited by using remote plasma atomic layer deposition were investigated. A 1-nm-thick SiO _2 buffer layer was grown on Si (100) substrates by rapid thermal annealing (RTA). The chemical bonding states at the interface between the La _2O _3 films and both Si and SiO _2/Si substrates were analyzed using X-ray photoelectron spectroscopy (XPS). From the XPS results, the relative intensities of the La-silicate peaks of the La _2O _3 film deposited on the Si substrate were higher than those of the La _2O _3 film deposited on the SiO _2 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 La _2O _3 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 La _2O _3 films on the SiO _2 buffer layer were -0. 73 V and -0. 49 V, respectively.