Superconducting Technology for Digital Applications

Abstract

In this paper, we describe our superconducting digital technology that uses Nb/AlOx/Nb Josephson junctions. Superconducting devices have intrinsically superior characteris- tics than those of semiconductor devices, and Nb/AlOx/Nb junc- tions have ideal current-voltage characteristics for digital applica- tions. Superconducting devices that use Nb/AlOx/Nb junctions have being actively developed because of their high speed and low power characteristics. Presently, we can fabricate more than twenty thousand junctions on one chip. Using niobium technol- ogy, a superconducting 4-kbit RAM has been already successfully developed. We have demonstrated the operation of a network sys- tem with a superconducting network chip. Some problems, such as difficulty in high-speed testing, disturbance from trapped mag- netic flux and so on, have been overcome by techniques such as a clock-driven testing method, moat structures and so on. The developed technologies, such as the fabrication technology, the design technology for moat structures and so on, must become the basic keys for the development of digital applications based on a single flux quantum device, which will be a promising com- ponent for ultra-high speed systems in the twenty-first century.