Di- and Tricarboxylic-Acid-Based Etches for Processing High Temperature Superconducting Thin Films

The development of passive and active electronics from high temperature superconducting thin films depends on the development of process technology capable of producing appropriate feature sizes without degrading the key superconducting properties. We present a new class of chelating etches based on di- and tricarboxylic acids that are compatible with positive photoresists and can produce submicrometer feature sizes while typically producing increases the microwave surface resistance at 94 GHz by less than 10%. This simple etching process works well for both the Y-Ba-Cu-O and Tl-Ba-Ca-Cu-O systems.