HTS Films and Multilayers for Electronics
Final rept. 20 Feb 94-19 Feb 97
NORTHROP GRUMMAN SCIENCE AND TECHNOLOGY CENTER PITTSBURGH PA
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This program established a materials and fundamental device base for an integrated circuit fabrication process for HTS digital electronics based on edge SNS Josephson junctions. The process was qualified by demonstration of small-scale single flux quantum SFQ logic circuits fabricated for the first time in an extendible configuration which integrated junctions and HTS groundplanes. Junction materials properties were investigated which affect the reproducibility of critical currents and, ultimately, the scale of circuit integration. Materials properties included the cummulative roughness of multilayer film structures, oxygen mobility in junction electrodes, second-phase precipitates, and crystalline orientation of junction edges. Processing steps investigated in detail included film deposition techniques, parameters, and composition ion milling angles, gas compositions, and edge profiles film edge morphology, clenning, and film coverage groundplanes over and under junctions groundplane oxidation and magnetic penetration depths and use of epitaxial buffer layers, protective cap layers, and low-loss insulations. Technology developed under this program was transferred to an Air Force WLML program where the junctions were optimized with critical current spreads reduced from 1-sigma values of 30 early in the program to 12 by the programs conclusion. Progress is also reported on tasks which address problems fundamental to the understanding of the superconducting state in HTS films, the application of HTS films in passive microwave circuits, and the development of new superconducting devices.
- Electrical and Electronic Equipment
- Electricity and Magnetism
- Solid State Physics