Preparation and electrical properties of (Ba,Sr)TiO3 thin films deposited by liquid source misted chemical deposition

(Ba,Sr)TiO3 (BST) thin films were grown on platinized Si wafers by liquid source misted chemical deposition (LSMCD). The electrical properties of BST films were investigated on Pt/SiO2/Si and Pt/Ti/SiO2/Si. BST thin films were deposited at room temperature and a pressure of 700 torr followed by a pre-baking step at 240 degreesC and a baking step at 500 degreesC. The top electrode was fabricated by rf sputter-deposition of 100-nm-thick Pt film on the BST film. The fabricated capacitors were annealed at 750 degreesC to crystallize sufficiently. A dielectric constant of 212 and a leakage current density of 5.8 X 10(-7) (A/cm(2)) at +1.1 V were achieved at a thickness of 115 nm. The significant increase in leakage current and the rapid failure of BST thin film capacitors resulted from the formation of hillocks at bottom electrode Pt, which was verified by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM) during heat treatment. The electrical properties of BST films were improved by a heat treatment under mixed ambient gas of N-2 and O-2. (C) 2001 Elsevier Science B.V. All rights reserved.