Repairing of Etching-Induced Damage of High-k Ba0.5Sr0.5TiO3 Thin Films by Oxygen Surface Plasma Treatment

Abstract

Ba0.5Sr0.5TiO3 (BST) thin films were patterned for fabricating BST capacitors in a helicon-wave plasma system. The optimization conditions were an Ar (80%)/Cl2 (20%) gas mixture with a helicon-wave plasma power and a substrate bias rf power of 1500 and 90 W, respectively. From results of X-ray photoelectron spectroscopy, physical ion bombardment is more effective than chemical reaction for removing Sr, while Ti can be removed by the formation of volatile TiClx. Ba was primarily removed by chemically assisted physical etching (such as that using BaClx). Some etching residues consisting of Ba and Sr were found after the BST films were etched and increased leakage current density. Oxygen surface plasma treatment can effectively repair surface damage caused by etching, and it reduced the leakage current density of the BST capacitor from 4.0×10-7 to 3.0×10-8 A/cm2 at 1 MV/cm and increased the breakdown field to ∼2 MV/cm at 1.0×10-6 A/cm2.