High resolution fabrication of Josephson microbridges

Recent advances in fabrication techniques and performance of 100-nm-scale superconducting Josephson microbridges are reviewed. Fabrication requirements imposed by the desired electrical performance are discussed; these lead to very small device dimensions and a three-dimensional structure to ensure good cooling of the active region. Fabrication approaches based on electron-beam lithography and on edge-defined patterning with substrate steps both achieve the desired dimensions and geometries. The self-aligning step-edge approach is simpler and more versatile for dimensions <100 nm, however, and is also ideally suited for production of microbridges employing high-T
c
refractory superconductors. Device performance for recent ultrasmall microbridge devices is summarized and assessed in terms of future limits.