Characteristics of intrinsic Josephson junctions using a Bi2Sr2CaCu2Ox thin film estimated overall in a chip

摘要

Integrated test chips of BiSr2CaCu2Ox thin-film-type intrinsic Josephson junctions (IJJs) are fabricated, and the yield of showing proper IJJ characteristics is examined. The thin-film type is expected to be suitable for applications to integrated circuits using THz electromagnetic waves, but its low fabrication yield is an issue to be solved. The chip size is 12x12 mm(2) in which 90 IJJs are included. Bi2Sr2CaCu2Ox, thin films are prepared via two steps. First the films are deposited on a low temperature (200 degreesC) substrate by a precisely controlled evaporation method. Next they are annealed at high temperatures (875 and 878 degreesC). The annealing time is varied to find an optimum condition. The best chip has a 70% yield of showing multiple-branch structure that is the most typical current vs voltage characteristics of IJJs. The relationship between the yield and the surface smoothness and the IJJ size dependence of the yield are also discussed. (C) 2004 Elsevier B.V. All rights reserved.