Effects of annealing on the electrical and interfacial properties of amorphous lanthanum scandate high-κ films prepared by molecular beam deposition

Abstract

Amorphous LaScO3 thin films were grown on (100) Si by molecular beam deposition and the effects of postdeposition thermal treatments on the film properties were studied after anneals in O2 or inert Ar atmosphere at 400 or 650 °C. Rutherford backscattering spectrometry, transmission electron microscopy, x-ray diffraction, and x-ray photoelectron spectroscopy (XPS) were employed to investigate the samples. Capacitance-voltage and current-voltage measurements allowed their electrical characterization. Postdeposition annealing in O2 reduces hysteresis, flatband voltage, and also leakage current density. In contrast, films treated in Ar ambient revealed a different behavior. The observations were associated with the interface evolution as studied by XPS, which verify that an O2 atmosphere favors the formation of a SiO2-rich interface between the film and the Si substrate, while a La-Sc-silicate-like compound predominates in this region after treating the samples in Ar. Additionally, postdeposition annealing results in an improvement of the dielectric constant up to 33, which is higher than that previously determined for LaScO3 or other amorphous alternative high-κ oxide films deposited by various techniques.