Abstract
Because of the increased need for higher levels of integration of capacitors and piezoelectric generators, such as in energy harvesting devices, the dielectrics used in capacitors have changed from traditional materials to complex oxides. One important candidate material for future integrated capacitors is (Ba,Sr)TiO3 (BST), because of its high dielectric and piezoelectric constants and its low leakage current. However, growth of BST films requires high temperatures of about 700°C, and the electrical properties of BST can be degraded by patterning processes. In the present study, BST thin films were deposited on sapphire and Pt/sapphire substrates using RF magnetron sputtering. Layered capacitors were then prepared using a metal mask method, and in-plane capacitors with interdigital electrodes were fabricated by lithography and wet etching. The electrical properties of the capacitors were evaluated, and defect energy levels were investigated using thermally stimulated current (TSC) measurements. The TSC results indicated the presence of three kinds of defects in the BST, with activation energies of 0.6, 0.7 and 0.8 eV. An annealing process was carried out in an attempt to remove damage caused by wet processing. This was found to reduce the dielectric loss, and the optimum annealing temperature was determined to be 200°C.
