Radio-frequency-sputtered tetragonal barium titanate films on silicon

Abstract

Polycrystalline films of BaTiO3 displaying electron diffraction patterns identical to that of bulk tetragonal BaTiO3 and ferroelectric properties are regularly observed for BaTiO3 films thicker than 1000 Å rf-sputtered deposited at 5 Å/min onto silicon substrates at temperatures above 500°C. A severe interaction problem between the silicon substrate and the BaTiO3 contaminates the film, but can be avoided by growing a passivation barrier of SiO2 on the silicon substrate before depositing BaTiO3. Despite a coefficient of thermal expansion mismatch between BaTiO3 and silicon, thin films with good electrical insulation properties can be obtained by reducing the substrate temperature during the deposition by 7.0°C/min to a final substrate temperature of 200°C.