ALL-NB THIN-FILM MICROBRIDGE-TYPE JOSEPHSON-JUNCTION FOR SUBMILLIMETER-WAVE DETECTION

A copolymer of methyl methacrylate (MMA) and 3-triethoxysilylpropyl me thacrylate (ESPMA) was proposed as a positive-working electron beam (E B) resist of a new type. It was found that it had 4-10 times the resis tance of polymethylmethacrylate (PMMA) against CBrF3 plasma damage. Th e mechanism of etching Nb in reactive-ion-etching (RIE) was deciphered . Using the new EB resist and nanometer process technology, an all-Nb thin film microbridge was fabricated. It shows the a.c. Josephson effe ct, i.e. the Shapiro steps upto the 11th were observed under millimete r-wave (70 GHz) radiation. In addition the coherently Working performa nce of the series array of these thin-film microbridges were observed definitively.