Bottom electrode and barrier materials issues in stacked capacitor type ferroelectric memories

A number of basic materials issues need to be solved to successfully realize the stacked ferroelectric capacitor cell concept, which is needed for FERAM with densities beyond about 1Mb. This paper discusses barrier materials selection and the role of bottom electrode microstructure for future PZT-based FERAM based on the stacked cell concept. Conventional methods for PZT texture control, employing Pt as a template layer, are less suited for stacked cell layouts, because of the poor diffusion barrier properties of Pt. Modification of the microstructure of RuO2 bottom electrodes has allowed us to eliminate the effect of underlying layers on the texture of PZT. The advantages of this approach in view of increasing circuit density of PZT-based FERAMs are discussed.