AVS 51st International Symposium
    Electronic Materials and Processing Thursday Sessions
       Session EM-ThA

Paper EM-ThA3
Tailoring of the Microwave Dielectric Properties of Ba@sub 1-x.@Sr@sub x@TiO@sub 3@ Based Thin Films by Acceptor Doping

Thursday, November 18, 2004, 2:40 pm, Room 304B

Session: Multifunctional Materials
Presenter: M.W. Cole, U.S. Army Research Laboratory
Authors: M.W. Cole, U.S. Army Research Laboratory
R.G. Geyer, National Institute of Standards and Technology
W.D. Nothwang, U.S. Army Research Laboratory
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In this work, material compositional design and optimized film processing methods, were employed to simultaneously lower the dielectric loss and enhance the dielectric tunability of Ba@sub 1-x.@Sr@sub x@TiO@sub 3@ (BST) based thin films without compromising the device impedance matching (permittivity less than 500) and device control voltage (less than 10 Volts) requirements. The films compositional design was achieved by Mg doping BST from 3 to 10 mol-percent via the metalorganic solution deposition (MOSD) technique and post-deposition annealing in an oxygen ambience. The films dielectric loss at these doping levels was identical, tan delta of 0.007, and the permittivity values ranged from 339 to 220. Device quality values of tunability, 40 and 32 percent, for the 3 and 7 mol-percent doped BST films, respectively, were achieved by elevating the applied bias to 474 kV/cm. This device quality tuning is compatible with voltage requirements of current semiconductor based systems. The results suggest that the low level acceptor doping from 3 to 7 mol-percent, optimized precursor solution concentration (0.43 M), and oxygenated post-deposition thermal processing were found to work in concert to lower dielectric loss, limit defect density concentration, optimize film microstructure, and eliminate undesirable film/electrode interfacial phases. The enhanced dielectric and insulating properties of the 3 to 7 mol-percent Mg doped BST thin films make them excellent candidates for integration into tunable devices.