Gadolinium scandate thin films as an alternative gate dielectric prepared by electron beam evaporation

Abstract

Gadolinium scandate thin films deposited on silicon substrates using electron beam evaporation were investigated. Measurements with Rutherford backscattering spectrometry, high temperature x-ray diffraction, x-ray reflectometry, transmission electron microscopy, and atomic force microscopy were performed. A stoichiometric transfer of material from the source to the substrate in high vacuum could be demonstrated. Homogeneous, amorphous, and smooth films (root mean square surface roughness $<1\mathrm{\AA }$ ) stable up to $1000°\mathrm{C}$ were obtained. Electrical characterization of capacitor stacks revealed a dielectric constant of $\approx 23$ , $C\text{-}V$ curves with small hysteresises and low leakage current densities ($770\mu \mathrm{A}∕{\mathrm{cm}}^2$ for a capacitance equivalent thickness of $1.5\mathrm{nm}$ ).