Damage in etching of (Ba,Sr)TiO3 thin films using inductively coupled plasma

Abstract

High dielectric (Ba, Sr)TiO3 thin films were etched in an inductively coupled plasma as a function of the Cl-2/Ar gas mixing ratio. Under Cl-2 (20)/Ar (80), the maximum etch rate of the BST film was 400 Angstrom /min and the selectivities of BST to Pt and PR obtained were 0.4 and 0.2, respectively. Etching by-products remained on the surface of BST and resulted in varying the stochiometry. Therefore, we investigated the surface of the etched BST using x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and x-ray diffraction (XRD). From the results of XPS analysis, we found that metal (Ba or Sr) chloride compounds remained on the surface of the etched BST for high boiling points. The morphology of the etched surface was evaluated with AFM. The surface roughness decreased as the Cl-2 increased in the Cl-2 /Ar plasma. From the results of XRD analysis, the crystallinity of etched BST films under Ar only and under Cl-2 (20)/Ar (80) was similar to that of as-deposited BST, However. the (100) diffraction peak abruptly decreased at the Cl-2 only plasma. It was assumed that metal (Ba or Sr) chloride compounds remained on the etched BST surface and changed the stoichiometry, resulting in crystallinity of the BST film during the etch process. (C) 2001 American Vacuum Society.