Characterization of pulsed laser deposited Ba0.6Sr0.4TiO3 on Pt-coated silicon substrates

The high dielectric constant (Ba,Sr)TiO3 (BST) films have been widely used to realize capacitors integrated on silicon with a high value of capacitance. The multilayer Pt/Ti/SiO2/Si is one of the most currently used bottom electrodes for the integration of BST on silicon. However, the crystal orientation and the dielectric properties of ferroelectric thin films are greatly influenced by the underlying Pt/Ti metallization, and particularly by the out-diffusion of titanium towards the platinum surface during thermal treatments. In this study, we show that the heating stage of the Pt/Ti/SiO2/Si substrate before the BST pulsed laser deposition is of primary importance in both favoring the (1 1 1) growth of the BST material within a wide range of oxygen deposition pressure and in reducing drastically the loss tangent values of Al/ BST/Pt capacitors because of the oxygen saturation of platinum. Electrical measurements indicate the existence of an interfacial layer degrading the capacitance. They support the presence of an interfacial depleted layer. The dramatic increase of the loss tangent under positive polarities applied on the platinum electrode is attributed to the ohmic contact of the BST/Al interface. Except this increase, all of the electrical properties are very promising in view to realize capacitors with high capacitance value and low dispersion. (C) 2002 Elsevier Science Ltd. All rights reserved.