Stabilized Platinum Electrodes for Ferroelectric Film Deposition using Ti, Ta and Zr Adhesion Layers

Pt-based metallizations using different adhesion layers (Ti, Zr and Ta) were studied for use as electrodes for ferroelectric thin films on oxidized silicon substrates. Different ways of oxidizing the adhesion layers prior to ferroelectric film growth are compared, with regard to obtaining stable, adherent Pt films of well-defined (111) orientation, while avoiding lead diffusion through the electrode. Upon in-situ deposition of PbTiO 3 at high excess lead flux, lead diffusion through the Pt film was found to depend strongly on the adhesion layer and the stabilization treatment. Pre-oxidation reduces lead diffusion during the later processing. Ti diffuses through the electrode upon oxidation, whereas Ta and Zr stay in place, in analogy to the diffusivities in the corresponding oxides. A novel oxidation treatment was developed to produce stable, adherent metallizations with controlled orientation and good barrier properties against lead diffusion.