Iridium thin film as a bottom electrode for high dielectric (Ba,Sr)TiO3 capacitors

Abstract

We propose Ir thin films as new electrode materials for high dielectric BST capacitors. Ir was found to be superior to Pt in a number of aspects such as resistivity, adhesion and surface roughness. The Pt/BST/Ir/SiO2/Si capacitors showed leakage currents as low as Pt/PST/Pt/SiO2/Si ones, but higher capacitance resulted. For endurance properties with +5V unipolar pulse trains, the dielectric constant of BST films on Ir decreased by only 10% below its initial value after switching of 10(9) cycles while that on Pt degraded by 30% after 10(8) cycles. Ir bottom electrode effects on BST film properties were well explained by the formation of IrO2 phases on the surface of Ir electrodes.