Berlin 2008 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 22: High-k Dielectric Materials - Synthesis, Properties, Applications

DS 22.2: Hauptvortrag

Mittwoch, 27. Februar 2008, 17:15–17:45, H 2032

Towards a better understanding of the dielectric collapse in high-K BST thin film capacitors — •Regina Dittmann¹, Rafael Plonka², Nikolay Pertsev³, Susanne Hoffmann-Eifert¹, and Rainer Waser^1,2 — ¹Institut für Festkörperforschung, Forschungszentrum Jülich, 52425 Jülich — ²Institut für Werkstoffe der Elektrotechnik, RWTH Aachen, 52056 Aachen — ³A. F. Ioffe Physico-Technical Institute, 194021 St. Petersburg, Russia

According to permittivities in the order of 10.000 observed in bulk ceramic samples, the perovskite material BaxSr1-xTiO3 (BST) is a promising candidate for future DRAM storage capacitors. A considerable drawback is that in polycrystalline thin films, the permittivity collapses to values in the order of 100 and decreases strongly with decreasing thickness. We addressed the influence of defects, substrates-imposed strain and the electrode interfaces on the dielectric collapse by investigating fully epitaxial SrRuO3/BST/SrRuO3 thin film capacitors. High resolution transmission electron microscope investigations prove the SrRuO3-BST interfaces to be atomically sharp and free of any defective "dead-layers". These capacitors exhibit bulk-like permittivity in the order 4000 and their thickness dependence can be well described by an extended Ginzburg-Landau-Devonshire model by taking into account plastic strain relaxation in BST thin films and finite screening of depolarizing fields by the SrRuO3 electrodes. We will compare the data to thin film capacitors with noble metal electrodes and discuss which type of interface is superior in terms of its screening ability.