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

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 × 10⁶V cm^-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 10⁶V cm^-1.