Berlin 2008 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 12: Dielectric and ferroelectric thin films and nanostructures II

DF 12.2: Vortrag

Donnerstag, 28. Februar 2008, 10:40–11:00, EB 107

Thickness dependence of leakage current through capacitor stacks with high-k materials for DRAM application — •Herbert Schroeder — IEM im Institut für Festkörperforschung und CNI, Forschungszentrum Jülich GmbH, D-52425 Jülich

According to the International Technology Roadmap for Semiconductors (ITRS) the implementation of high-permittivity thin insulating films as dielectrics in capacitors (charge-based memory) and gates (MOSFET) is indispensable within the near future to achieve the documented goals. One of the most important issues for these applications is the sufficiently low leakage current through the metal/insulator/metal (MIM) capacitor stacks. A large number of experimental data on leakage current through MIM thin film capacitor structures is published for high-k perowskite-type mixed oxides, especially for the model alloys SrTiO₃ (STO) and (Ba,Sr)TiO₃ (BST). The mechanistic interpretation of these data is rather contradictory and therefore unsatisfactory. This especially holds for the current dependence on dielectric thickness, for which very different and opposite trends have been observed. This contribution reports simulation results of leakage curves within a new model combining current injection/ejection at the interfaces with drift-diffusion current in the film bulk with special emphasis on dielectric thickness. The main result is that the used model is able to describe all kinds of thickness dependencies as the current is dependent on the defect properties in the dielectric, i.e. type (donor and/or acceptor), densities, energy level in the gap, and type and degree of compensation (ionic, electronic), as well as electrode/interface properties.