A Hybrid Josephson Transmission Line and Passive Transmission Line Routing Framework for Single Flux Quantum Logic

The single flux quantum (SFQ) logic family is a novel digital logic as it provides ultrafast and energy-efficient circuits. For large-scale SFQ circuit design, specialized electronic design automation (EDA) tools are required due to the differences in logic type, timing constraints, and circuit architecture, in contrast to the Complementary metal-oxide-semiconductor (CMOS) logic. In order to improve the overall performance of an SFQ circuit, an efficient routing algorithm should be applied during the layout design to perform accurate timing adjustment for fixing hold violations and optimizing critical paths. Thus, a hybrid Josephson transmission line and passive transmission line routing framework is proposed. It consists of four main modules and an exploration of the potential timing performance based on the given layout placement. The proposed routing tool is demonstrated on seven testbench circuits. The obtained results demonstrate that the operating frequency is greatly improved, and all the hold violations are eliminated for each circuit.