LEAKAGE CURRENTS IN BA0.7SR0.3TIO3 THIN-FILMS FOR ULTRAHIGH-DENSITY DYNAMIC RANDOM-ACCESS MEMORIES

(Ba,Sr)TiO3 (BST) thin films grown by chemical vapor deposition and wi th platinum (Pt) top and bottom electrodes have been characterized wit h respect to the leakage current as a function of temperature and appl ied voltage. The data can be interpreted via a thermionic emission mod el. The Schottky approximation accounts for superohmic behavior at hig her fields, but the barrier lowering is stronger than expected from th is theory. While the leakage mechanism is comparable to SrTiO3 thin fi lms prepared by chemical solution deposition, the absolute values of t he leakage current are significantly lower for the metalorganic chemic al vapor deposition (MOCVD) prepared BST film. This is presumably due to a more homogeneous microstructure of the latter and may also be due to different electrode processing. The influence of the film thicknes s on the leakage in combination with additional findings is used to di scuss the field distribution in the films under a dc voltage stress. ( C) 1997 American Institute of Physics.