Vision for single flux quantum very large scale integrated technology**This technology was exported from the United States in accordance with the USDepartment of Commerce Export Administration Regulations (EAR) for ultimatedestination in the United Kingdom. Diversion contrary to US law prohibited.

Abstract

Single flux quantum (SFQ) electronics is extremely fast and has very low on-chip powerdissipation. SFQ VLSI is an excellent candidate for high-performance computing and otherapplications requiring extremely high-speed signal processing. Despite this, SFQ technologyhas generally not been accepted for system implementation. We argue that this is due, atleast in part, to the use of outdated tools to produce SFQ circuits and chips. Assuming theuse of tools equivalent to those employed in the semiconductor industry, we estimate thedensity of Josephson junctions, circuit speed, and power dissipation that could be achievedwith SFQ technology. Today, CMOS lithography is at 90–65 nm with about 20 layers.Assuming equivalent technology, aggressively increasing the current density above100 kA cm−2 to achieve junction speeds approximately 1000 GHz, and reducing device footprints by convertingdevice profiles from planar to vertical, one could expect to integrate about 250 M Josephson junctionscm−2 into SFQ digital circuits. This should enable circuit operation with clock frequencies above200 GHz and place approximately 20 K gates within a radius of one clock period. As aresult, complete microprocessors, including integrated memory registers, could befabricated on a single chip.