LTS Josephson junction critical current uniformities for LSI applications

Manufacturing yields of large scale superconducting circuits depend strongly on the uniformity of junction critical currents. We report on junction manufacturing tolerances based on extensive measurements of Nb- and NbN-based junction arrays and individual junctions. Transient waveforms induced by switching of a single junction have sufficient amplitude to switch other junctions in a series array. We have measured the effect of sympathetic switching and developed damping structures to dissipate switching transients. Comparisons of critical current distributions measured on individual junctions with critical current distributions determined from series junction arrays are presented. In addition, the validity of using series arrays of large numbers of junctions to assess the critical current uniformity is discussed.<
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