Microstructural and electrical properties of (BaxSr1-x)Ti1+yO3+z thin films prepared by RF magnetron sputtering

The electrical and microstructural properties of (BaxSr1-x)Ti1+yO3+z(BST) thin films prepared by RF magnetron sputtering were investigated as a function of deposition temperature over the range of 100degreesC to 650degreesC. Films deposited above approximately 350degreesC on Pt/TiO2/SiO2/Si substrates were polycrystalline with relative permittivites of 100 nm thick BST thin films varying from 100 at 350degreesC to 600 at 650degreesC. For deposition temperatures below approximately 350degreesC, the electrical properties were strongly influenced by the presence of a less crystalline BST layer. Films deposited at 250degreesC were comprised of a multilayer polycrystalline/less crystalline BST structure. The less crystalline BST layer strongly affected both measured dielectric permittivity and leakage properties. Leakage characteristics of Pt/BST(250degreesC)/Pt capacitors exhibited a power law dependence on voltage or an exponential dependence on square root of the applied voltage depending on whether the top Pt electrode adjacent ot the polycrystalline BST layer was biased at a high or low electric potential, respectively. Mechanisms for the observed leakage behavior are discussed.