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

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 (VFB) 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 VFB 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.