HIGH DIELECTRIC-CONSTANT (BA,SR)TIO3 THIN-FILMS PREPARED ON RUO2 SAPPHIRE

RuO2 thin films have been prepared onto sapphire by reactive sputtering with Ar+O2 plasma and their application as the bottom electrode in the high dielectric constant (Ba0.5Sr0.5)TiO3 (BST) thin film capacitor has been studied. RuO2 films with rutile structure are obtained with O2 content greater than 0.7. The dielectric constants of the sputtered (Ba0.5Sr0.5)TiO3 films on the RuO2 films are 250 for 49-nm-thick film and 460 for 130-nm-thick film. These values are comparable with those on Pt and Pd, which are commonly used as the bottom electrodes. No remarkable interdiffusion at the BST/RuO2 interface region and no hillocks at the RuO2 surface were observed, even after BST film deposition at 620-degrees-C. RuO2 is one of the promising materials for use as the bottom electrode for the (Ba0.5Sr0.5)TiO3 thin film capacitor.