Advanced electrical characterization of atomic layer deposited Al2O3 MIS-based structures

The electrical properties of Al2O3-based metal-insulator-semiconductor capacitors have been investigated. Three different metal gate electrodes were used: two mid-gap metals (TiN and tungsten) and aluminum, a metal with a work function close to the silicon electron affinity. Aluminum oxide films were grown on p-type silicon substrates by atomic layer deposition using trymethylaluminum and water as aluminum and oxygen precursors, respectively. The use of aluminum as the gate electrode prevents the formation of defects inside the oxide layers that could trap charge as has been found for W and TiN gate electrodes using C-V curves and flat band voltage transients. The use of TiN or W as gate electrodes increases the interfacial trap density. However, the leakage current, that follows a Fowler-Nordheim behavior, is low when using TiN electrodes due to a higher cathode barrier height.