Wet etch process for patterning insulators suitable for epitaxial high T c superconducting thin film multilevel electronic circuits

Abstract

We describe a wet etch process for patterning insulators suitable for multilayer epitaxial highT_c superconductor‐insulator‐superconductor structures down to micronmeter‐scale dimensions. A solution of 7% HF in water gives convenient etch rates for SrTiO₃ and MgO insulators (about 1500 Å/min for single crystals), and easily stops on thin high T_c superconducting layers, due to the high selectivity of this etchant between these insulators and the cuprate superconductors. Using entirely wet etching patterning processes, we have fabricated 5‐turn (20‐turn) coils with zero resistance at 89 K (79 K) and critical currents at 77 K of 2.5 mA (6 μA).