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 oxygen and fo rming gas (95% Ar, 5% H-2) were investigated. The Schottky barrier height f or thermionic emission of electrons from the cathode varied depending on an nealing conditions. The electrically measured barrier height of 0.67 eV in the as deposited film significantly increased to 1.29 eV by annealing at 55 0 degrees C for 15 min in oxygen, while the magnitude of the relaxation cur rents were only slightly affected. A subsequent anneal at 400 degrees C in forming gas for 20 min decreased the barrier height to 0.92 eV and increase d the dielectric relaxation currents by an order of magnitude. Re-annealing in oxygen at 400 degrees C for 20 min improved the leakage but still resul ted in an estimated 28% charge loss due to the slow polarization currents f or the large (10(4) mu m(2)) unpassivated planar capacitors used in this st udy. (C) 1999 Elsevier Science Limited. All rights reserved.