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

Several bottom electrode systems for ferroelectric thin film deposition onto reactive substrates or reactive metal films were investigated with respect to chemical barrier properties and contact resistivity. Such electrode systems should not deteriorate by oxidation, and should prevent oxygen diffusion into the underlying base metal. The protective performance of Pt, Ru, RuO2/Ru, and Cr was evaluated on reactive substances such as W, Zr, Mo, and TiN. On most materials, a reactive and passivating metal such as Cr offers protection up to a higher temperature than noble metals. This is explained by preferential oxidation. On Cr, a RuO2 electrode allowed oxidation resistance to more than 800 C without any Cr diffusion: the RuO2 serves both as an electrode and as a barrier to Cr. In order to reduce the contact resistance due to the formation of a Cr2O3 film at the RuO2/Cr interface, a Ru interlayer was inserted. This combination allowed a low contact resistance to be maintained up to 700 C. 21 refs.