Wet Chemical Etching of High T_C Superconductors by Ethylenediaminetetraacetic Acid (EDTA)

Abstract

A novel chemical etchant for the high temperature superconducting material YBa₂Cu₃O_7-x is demonstrated. The etching solution which consists of ethylenediaminetetraacetic acid (EDTA) in water does not degrade the properties of the superconducting films and is suitable for applications with standard photolithography. We have etched 2-200 μm wide wires which show no degradation of T_c ( within 1 K accuracy of the measurements) and show zero-resistance temperature ≥90 K. The etchant exhibits a polishing effect by selectively removing the porous and semiconducting surface layers which are formed during high temperature annealing process. The dense bulk of the films are etched at a rate of 1400 Å/min which provides control for fine-line patterning of thin film material. The critical current densities of the unpatterned films which are polished by reactions with EDTA remain unaffected and are measured to be about 5 x 10⁶ A/cm².