BaTiO3 thin film capacitors deposited by r.f. magnetron sputtering

Abstract

Barium titanate, BaTiO3, thin film capacitors were deposited by r.f. magnetron sputtering using a perpendicular arrangement of the substrate with respect to the target. Capacitors with a single-layer amorphous or polycrystal structure, a bilayer structure of amorphous/polycrystal, and a trilayer structure of amorphous/graded polycrystal/polycrystal were extensively investigated. Comparatively, the single-layer amorphous BaTiO3 capacitor demonstrated the highest breakdown voltage (as high as 2.5 × 106Vcm-1) but lowest dielectric constant of around 16. The single-layer polycrystal BaTiO3 capacitor displayed a much higher dielectric constant of above 300 but also revealed high leakage current which in turn reduced the breakdown voltage. By combining the advantages of the amorphous and polycrystal BaTiO3 films, bilayer and trilayer capacitors were produced, yielding superior electrical properties. An optimum thickness for the amorphous layer minimizes the reduction in effective dielectric constant while providing a low d.c. conductivity of 7.0 × 10-11 Ω-1 cm-1 at a bias of 4 V and a high breakdown voltage of 1.9 x 106Vcm-1.