Conducting barriers for direct contact of PZT thin films on reactive substrates

Several bottom electrode systems for ferroelectric thin film deposition ont o reactive substrates or reactive metal films have been investigated with r espect to chemical barrier properties and contact resistivity. Such electro de systems should not deteriorate by oxidation, and should prevent oxygen d iffusion into the underlying base metal. First, the protective performance of Pt, Ru, RuO2/Ru, and Cr has been evaluated on reactive substances such a s W, Zr, Mo, and TiN; On most materials, a reactive and passivating metal s uch as Cr offers protection up to a higher temperature than noble metals. T his is explained by preferential oxidation. On Cr, a RuO2 electrode allowed oxidation resistance to more than 800 degrees C without any Cr diffusion: the RuO2 serves both as an electrode and as a barrier to Cr. In order to re duce the contact resistance due to the formation of a Cr2O3 film at the RuO 2/Cr interface, a Ru interlayer was inserted, giving an RuO2/Ru/Cr. This co mbination allowed maintaining a low contact resistance up to 700 degrees C. (C) 1999 The Electrochemical Society. S0013-4651(98)12-012-8. All rights r eserved.