MOCVD of High-Dielectric-Constant Lanthanum Oxide Thin Films

Lanthanum oxide thin films were fabricated on Si substrates by the metallorganic chemical vapor deposition (MOCVD) method at substrate temperatures ranging from 400 to 650°C. From the results of X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), cross-sectional scanning transmission electron microscopy (STEM), and energy-dispersive X-ray (EDX) analyses, the enhanced chemical reaction at the interface between the Si substrate and the films was revealed, which results in the generation of an interfacial layer of SiO 2 (1-2 nm thick) and lanthanum silicate at all the experimental substrate temperatures. We found that a thin silicon oxynitride layer on the Si substrate is effective in suppressing the interfacial reaction and in increasing the dielectric constant of the lanthanum oxide deposited on it. The thin silicon oxynitride layer is also effective in reducing the leakage current through the film. For the stacked La-oxide/SiON film, the dielectric constant of the lanthanum oxide film was 19 and the leakage current density was 3 X 10 -6 A/cm 2 at the oxide voltage of 1 V for a film with an equivalent oxide thickness of 2.4 nm.