Effects of annealing conditions on charge loss mechanisms in MOCVD Ba0.7Sr0.3TiO3 thin film capacitors

The leakage and dielectric relaxation currents of MOCVD Ba0.7Sr0.3TiO3 thin films with Pt electrodes after post top electrode anneals in O2 and forming gas (95% Ar, 5% H2) were studied. The Schottky barrier height for thermionic emission of electrons from the cathode varied depending on annealing conditions. A barrier height of 0.67 eV in the as-deposited film significantly increased to 1.29 eV by annealing at 550 C for 15 min in O2, while the magnitude of the relaxation currents were only slightly affected. A subsequent anneal at 400 C in forming gas for 20 min decreased the barrier height to 0.92 eV and increased the dielectric relaxation currents by an order of magnitude. Re-annealing in O2 at 400 C for 20 min improved the leakage but still resulted in an estimated 28% charge loss due to the slow polarisation currents for the large (10 exp(4) micron2) unpassivated planar capacitors used in this study. 20 refs.