Superconductor-insulator-normal-conductor-insulator-superconductor (Nb/AlxOy/Al/AlxOy/Nb) process development for integrated circuit applications

The paper reports on recent developments in a new technology process in LTS implementation to fabricate intrinsically shunted tunnel junctions. The pr ocess has been realized in SINIS Nb/AlxOy/Al/AlxOy/Nb multilayer thin-film technology. In various test series, circuits containing a large variety of single junctions and junction arrays of different contact areas and sizes w ere fabricated and measured. By variation of the oxidation parameters the f abrication process has been optimized for application in integrated circuit s operating in RSFQ impulse logic. The junction parameter values realized f or the critical current density j(c) range to up to about j(c) = 1000 A cm( -2), those for the characteristic voltage V-c to up to about V-c = 230 mu V . The junctions show nearly non-hysteretic current-voltage characteristics; the intra-wafer parameter spread is below 10%. The junctions realized fulf il the requirements imposed for digital RSFQ circuit operation at clock fre quencies in the lower GHz frequency range.