An all-niobium eight level process for small and medium scale applications

The eight mask-level circuit process described is based on reproducible, high quality, all-niobium Josephson junctions. The junctions are fabricated from in situ trilayer films of Nb/Al-AlOx/Nb using the Selective Niobium Etching and Anodization Process (SNEAP). The quality of our junctions can be characterized by the figure of merit Vm, which is reproducibly greater than 40 mV at critical current densities of nearly 2 kA/cm². These junctions have been incorporated into an eight level process that has been used to fabricate a voltage standard, a time domain reflectometer (TDR), and other circuits. This paper will describe the eight level process, the junction characteristics, and the application of this process to circuit fabrication.