OFF-CHIP SUPERCONDUCTOR WIRING IN MULTICHIP-MODULE FOR JOSEPHSON LSI CIRCUIT

A superconducting multichip module using Nb/Polyimide on a mullite mul tilayer ceramic substrate has been developed for Josephson LSI circuit s. The Nb/Polyimide stacked layers on the mullite multilayer ceramic s ubstrate makes it possible to fabricate superconducting off-chip wirin g for control signal line. We named the MCM ''SuperMCM.'' The supercon ducting transmission line is designed to have the characteristic imped ance of 14 OMEGA to match with the Josephson devices. The superconduct ing critical temperature, critical current density and critical curren t at a via hole are 8.5 K, 8.2 x 10(5) A/cm2 and 2.5 A, respectively. The SuperMCM also provides matching circuits employing quarter wavelen gth striplines for driving Josephson LSI circuits at a microwave frequ ency, and DC bias circuits in the mullite multilayer ceramic substrate . The characteristics of the matching circuit is measured in the frequ ency range up to 3.6 GHz and the microwave current gain of 20 dB is ob tained at 1.2 GHz, which revealed that the SuperMCM has the ability to drive the Josephson LSI circuits at more than 1.2 GHz clock speed.