FABRICATION OF SUBMICRON NB ALOX/NB JOSEPHSON-JUNCTIONS USING ECR PLASMA-ETCHING TECHNIQUE/

It is important to develop a high-yielding and reproducible fabricatio n process of submicron Nb/AlOx/Nb Josephson junctions tee improve the integration level and the operating speed of Josephson LSI circuits. F or this purpose, we have developed a junction fabrication process by i ntroducing an electron cyclotron resonance (ECR) plasma, etching techn ique with CF4 gas. In the ECR plasma etching technique, highly anisotr opic etching of Nb was achieved, Over-etching was reduced by 86%. Wt h ave successfully fabricated Nb/AlOx/Nb junctions with critical current density of 10(4) A/cm(2) using the cross-line patterning (CLIP) metho d and the electron beam (EB) lithography technique, where the size of the junctions was varied from 2 mu m to 0.5 mu m at 0.1 mu m intervals . High-quality submicron junctions far integrated circuits with small spread of critical current Ic was obtained. High uniformity of He was achieved. The characteristics of the fabricated junctions are discusse d and compared with the junctions fabricated by RIE technique.