Optical, electrical, and structural characteristics of yttrium oxide films deposited on plasma etched silicon substrates

Yttrium oxide thin films were deposited on Si(100) substrates using the rf-sputtering technique at low power density and low temperatures (up to 300°C). Previous to deposition, the substrates were plasma etched during different lengths of time. The characteristics of these films and the effect of surface etching on the substrate were studied by ellipsometry, x-ray diffraction at grazing angle, atomic force microscopy, and x-ray energy dispersive spectroscopy (EDS). The deposited films were polycrystalline, presenting cubic and/or monoclinic phases. The deposition rate, refractive index, surface roughness, and degree of crystallinity were strongly dependent on etching time of the substrate, especially for low deposition temperatures. The electrical characterization of the films incorporated in a metal-oxide-semiconductor structure showed a good dielectric constant value (up to 11), surface states densities as low as 6.7×10¹¹ cm^-2eV^-1 at midgap and breakdown strength in the range of 1.16-4.84 MV/cm. EDS measurements on these films showed a higher oxygen content than expected for Y₂O₃ stoichiometry.