SNS and SIS Josephson junctions with dimensions down to the submicron region prepared by a unified technology

Several applications of Josephson junctions (JJs) in low-temperature superc onducting circuits such as programmable voltage standards and SFQ logical c ircuits or SQUID sensors require JJs with sub-mu m dimensions. A method for preparing superconductor-isolator-superconductor (SIS) JJs as well as supe rconductor-normal metal-superconductor (SNS) JJs was developed which allows the preparation of both types of junctions by nearly the same technologica l process. Titanium is used as the normal metal for the SNS JJ. Ti can be a nodically oxidized and a technology similar to the well-tried Nb-Al technol ogy for SIS JJs can be applied to the SNS system, too. By electron-beam exp osure of a negative deep UV photoresist (ma-N 2400) a stable resist mask is generated which has to withstand the following three self-aligned process steps: etching of the Nb counterelectrode by RIE, isolation by anodization and lifting of a SiO planarization layer. By this process SNS (Nb-Ti-Nb) an d SIS (Nb-Al/AlOx-Nb) Josephson junctions with smallest junction areas of 0 .49 mu m(2) were prepared and characterized by de measurements and under th e influence of microwave irradiation. The Nb-Ti-Nb junctions have IcRn prod ucts of 87 mu V. They can be used for programmable Josephson voltage standa rd circuits at frequencies of 70 GHz.