超電導エレクトロニクス ジョセフソンデジタルＬＳＩ技術

Abstract

Superconductive LSI with Josephson junctions have features such as low-power dissipation and high switching speed. This paper describes the recent progress of Josephson digital LSI technology. Firstly, we reviewed our developed 4-Kbit RAM with vortex transitional memory cells to illustrate the operation of the superconductive LSI using Josephson junctions. We developed a fabrication process tehnology for the 4-Kbit RAM. In the 4-Kbit RAM, a suitable moat structure was designed to reduce the influence of the trapped magnetic flux. The RAM is characterized by 380 ps access time, 99.8% bit yield, and 9.5mW power dissipation. Furthermore, we discuss GHz testing which is one of the most significant issues concerning Josephson digital LSIs. Finally, we discuss a future application for the Josephson digital LSI. The Josephson digital LSI has a special operating feature at a clock frequency of several GHz. We propose a superconductive ring pipelined network between processor elements at such a high-speed application. The prototype chip was designed and estimated to be able to operate at approximately 10GHz. A clock with a frequency of several GHz clock is an impontant feature for future Josephson digital LSI technology.