Wet etching of gold films compatible with high T_c superconducting thin films

Abstract

We report a wet etch process for selective patterning or removing gold (Au) layers on top of high Tc YBa2Cu3O7 (YBCO) thin-film structures. As an etchant for Au, an aqueous solution of potassium iodide (KI) and iodide (I) was chosen. This etchant does not degrade YBCO or any commonly used substrate materials (SrTiO3, MgO, zirconia, and NdGaO3). This KI and I solution gives convenient etch rates of 200-300 Å/min and easily stops on the YBCO due to its high selectivity. Using this wet chemical etching process, we have fabricated structures with better than 1 μm resolution. We have found this etchant to be very useful for secondary electron microscopy analysis of high Tc device structures.