Effects of annealing conditions on charge loss mechanisms in MOCVD Ba_0·7Sr_0·3TiO₃ 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 oxygen and forming gas (95% Ar, 5% H2) were investigated. The Schottky barrier height for thermionic emission of electrons from the cathode varied depending on annealing conditions. The electrically measured barrier height of 0·67 eV in the as deposited film significantly increased to 1·29eV by annealing at 550°C for 15min in oxygen, while the magnitude of the relaxation currents were only slightly affected. A subsequent anneal at 400°C in forming gas for 20min decreased the barrier height to 0·92eV and increased the dielectric relaxation currents by an order of magnitude. Re-annealing in oxygen at 400°C for 20min improved the leakage but still resulted in an estimated 28% charge loss due to the slow polarization currents for the large (104μm2) unpassivated planar capacitors used in this study.