Stability and Oxidation Behavior of Ir Thin Film Electrodes on Si and SiO2

This paper examines factors affecting the oxidation behavior of Ir thin film electrodes and the stability of bilayer Ir/Ir-Ir-O-Si electrodes on silicon substrates. We first examine the morphology and texture of faceted IrO2 extrusions formed on the Ir films during thermal oxidation, and show that an Ir grain-growth anneal in N2 at 650°C for 5 min prior to the oxidation treatment increases both the areal density of IrO2 extrusions and the IrO2<110> x-ray diffraction intensity while decreasing apparent film roughness. We then examine the stability of bilayer lr(100 nm)/Ir(20 nm) films on polycrystalline silicon and show how fairly mild oxygen anneals of the Ir(20 nm)/Si structures can provide an in-situ formed Ir-O-Si barrier that protects the subsequently deposited Ir(100 nm) layer from silicidation reactions during annealing in N2 ambients at 750°C. Transmission electron microscopy indicates that this in-situ formed barrier at the Ir/Si interface has a two layer structure comprising an IrSix underlayer in contact with the silicon substrate and an SiO2 overlayer directly below the remaining Ir.