An Overview of Materials and Process Aspects of Josephson Integrated Circuit Fabrication

Presented here is an overview of materials and process aspects of a method that has been developed for fabricating experimental integrated circuits containing Josephson junctions as active elements. Superconducting Pb-alloy thin films are used for forming the junction electrodes, and a combination of thermal and rf oxidation is used for forming the tunnel barrier oxides. In addition to the junctions, the circuits, which are formed above an insulated, superconducting Nb ground plane, also contain: superconducting Pb-alloy lines, contacts, and transformers; AuIn2, damping and terminating resistors; insulated crossings; etc. Insulation between the ground plane and overlying conducting layers is achieved through use of a combination of Nb2O5, and SiO. The latter is also used to achieve insulation between overlying conducting layers and as a final protective coating. Photoresist processes are used for layer patterning.