Characterization of Gd2O3 films deposited on Si(100) by electron-beam evaporation

Gadolinium oxide films were deposited on Si(100) substrates from a rod-fed electron beam evaporator using a pressed-powder Gd2O3 target. Films 25 nm thick were shown to be stoichiometric Gd2O3 by Rutherford backscattering and had a dielectric constant at 100 kHz of 16.0 +/- 0.3. Transmission electron microscopy and X-ray reflectivity measurements showed that films 7-13 nm thick annealed in oxygen consisted of three distinct layers, an interfacial silicon dioxide layer next to the substrate, a second amorphous oxide layer containing silicon, gadolinium, and oxygen above this, and a polycrystalline Gd2O3 layer on top. Annealing in oxygen reduced the leakage currents, increased the thickness of the silicon dioxide layer, and increased the grain size of the top Gd2O3 layer. The characteristics of the leakage currents through the gadolinium oxide were consistent with a Frenkel-Poole conduction mechanism with a silicon-Gd2O3 band offset of 1.8 V. Interfaces with excellent electrical properties, characteristic of good SiO2, were obtained after annealing in oxygen. Annealing of the films in vacuum prior to oxygen annealing reduced the thickness of the interfacial silicon dioxide. (C) 2001 The Electrochemical Society. All rights reserved.