Effects of high working pressure on dielectric properties of sputtered (Ba,Sr)TiO3 films on Ir electrodes

Abstract

High working pressure (47 mTorr) was used for rf-sputtered (Ba,Sr)TiO3 (BST) films on Ir bottom electrodes to enhance the in situ formation of IrO2 without postannealing. We verified that oxygen plasma bombardment on the Ir surface during the deposition of BST films was the dominant mechanism for in situ IrO2 formation under the condition of high working pressure. The as-deposited BST film of 100 nm grown at 500 °C shows a high dielectric constant of 630 (at 10 kHz); however, the leakage current is relatively large (6×10−5 A/cm2 at 100 kV/cm). The large leakage current results from the rough interface due to the formation of thick IrO2. To reduce leakage current, the double-layer technology was used, in which a thin BST film (5 nm) was first deposited with pure Ar, and followed by the deposition of a thick film (95 nm) with mixture gas (Ar/O2=1). The thin BST layer can significantly reduce the roughness of IrO2, resulting in lower leakage current (4×10−7 A/cm2); however, since the thin BST layer is oxygen deficient, the dielectric constant is reduced to 443.