100 GHz Demonstrations Based on the Single-Flux-Quantum Cell Library for the 10 kA/cm2 Nb Multi-Layer Process

Yuki YAMANASHI  Toshiki KAINUMA  Nobuyuki YOSHIKAWA  Irina KATAEVA  Hiroyuki AKAIKE  Akira FUJIMAKI  Masamitsu TANAKA  Naofumi TAKAGI  Shuichi NAGASAWA  Mutsuo HIDAKA  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E93-C   No.4   pp.440-444
Publication Date: 2010/04/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E93.C.440
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Frontiers of Superconductive Electronics)
Category: Digital Applications
Keyword: 
single flux quantum circuit,  Josephson junction,  cell library,  adder,  

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Summary: 
A single flux quantum (SFQ) logic cell library has been developed for the 10 kA/cm2 Nb multi-layer fabrication process to efficiently design large-scale SFQ digital circuits. In the new cell library, the critical current density of Josephson junctions is increased from 2.5 kA/cm2 to 10 kA/cm2 compared to our conventional cell library, and the McCumber-Stwart parameter of each Josephson junction is increased to 2 in order to increase the circuit operation speed. More than 300 cells have been designed, including fundamental logic cells and wiring cells for passive interconnects. We have measured all cells and confirmed they stably operate with wide operating margins. On-chip high-speed test of the toggle flip-flop (TFF) cell has been performed by measuring the input and output voltages. The TFF cell at the input frequency of up to 400 GHz was confirmed to operate correctly. Also, several fundamental digital circuits, a 4-bit concurrent-flow shift register and a bit-serial adder have been designed using the new cell library, and the correct operations of the circuits have been demonstrated at high clock frequencies of more than 100 GHz.