Fabrication of NbN single flux quantum (SFQ) circuit and operating properties at 10 K

We fabricated a prototype of a single flux quantum (SFQ) logic circuit for operation near 10 K by using NbN, which has a critical temperature around 1 6 K. This circuit is fabricated on a 2-inch silicon (Si) substrate based on the NbN/AlN/NbN tunnel junction having fluctuations in the critical curren t of +/-5% or less from 976 Josephson junctions (JJ). The fabrication of a prototype circuit to generate, propagate, and detect SFQ pulses and the exa mination of its operation confirmed normal operation up to approximately 9. 8 K, which is close to 10 K. In addition, at the operating temperature of 8 .5 K, the operations of elementary cells such as a confluence buffer and a T flip-flop were verified and were successful in the operation of the large st scale circuit, an 8-bit shift register consisting of 105 JJ. (C) 2001 Sc ripta Technica.