New electrode-barrier structures for high density ferroelectric memories

In this paper, two electrode-barrier structures based on Pt-Ph and Pt-Ir al loys and their oxides are proposed for high-density ferroelectric memory ap plications. These electrode-barriers are multi-layered, comprising a diffus ion barrier (PtRhOx or PtIrOx), metal alloy (PtRh or PtIr) and another PtRh Ox or PtIrOx laver for fatigue reduction in the case of PZT capacitors. Bot h lead zirconate titanate (PZT) and strontium bismuth tantalate (SBT) capac itors based on the electrode-barriers were used in the present study. The e lectrode-barrier structure acts as a conducting electrode as well as an exc ellent diffusion barrier for lead, bismuth, oxygen and silicon. The PZT tes t capacitors fabricated on these electrode-barriers showed excellent fatigu e resistance with other ferroelectric properties being similar to these on Pt. Also, these electrode-barriers are stable, and remain conductive even u p to the processing temperatures of SET (750 degreesC). This makes direct i ntegration of both PZT and SET capacitors on to a poly-Si plug attainable. In addition, the conducting electrode-barrier structures can be deposited i n situ, directly over n+polycrystalline Si, thereby significantly improving the density of the device.