High-resolution x-ray reflectivity study of thin layered Pt-electrodes for integrated ferroelectric devices

The structural interface properties of layered Pt/Ti/SiO₂/Si electrodes have been investigated using high-resolution specular and diffuse x-ray reflectivity under grazing angles. Currently this multilayer system represents a technological standard as bottom electrodes for ferroelectric thin-film applications. For the electronic and ferroelectric properties of integrated devices, the film-electrode interface is of crucial importance. We focused on Pt 1000 Å/Ti 100 Å/SiO₂/Si electrodes prepared under annealing conditions as employed in industrial processing, prior to the deposition of ferroelectric films. The comparison between annealed and non-annealed electrodes clearly revealed strong interfacial effects due to interdiffusion and oxidation of Ti, especially at the Pt-Ti interface. Migration of Ti into the Pt layer results in a shift of the critical angle due to the enclosure of TiO_2-x within the Pt layer. The heterogeneous distribution of TiO_2-x suggests a diffusion mechanism mainly along the Pt grain boundaries. At the SiO₂ interface a relatively weakly oxidized Ti layer of 20 Å remained, which is most probably correlated with the remaining adhesion to the substrate.