Tungsten based electrodes for stacked capacitor ferroelectric memories

Fabrication of high-density ferroelectric memories requires the growth of the ferroelectric material on the drain contact metal. In standard 0.5 mum technology, tungsten plugs are applied to connect the drain contacts to the first metallization level. In this work, we investigated electrode systems to be applied between sputter deposited, ferroelectric PbZr0.35Ti0.65O3 (PZT) and tungsten. Besides the obvious barrier function of such an electrode system, the texture of the PZT is of interest as well. The roughness of chemical vapor deposition (CVD) of W layer before and after etch-back by dry etching resulted in an increased leakage current of the ferroelectric capacitor. The problem could be solved by chemical mechanical polishing (CMP) of the tungsten film.