Ultra-high-speed rapid single-flux-quantum digital circuits. using a planarized-niobium-trilaver josephson junction technology

Josephson junction integrated circuits using Rapid Single-nux-Quantum (RSFQ) logic are capable of performing logic operations at ultrahigh clock frequencies in excess of 100 GHz [ 11. In order to reach such a speed, Josephson junctions with high critical current density (jc=10kAkm2) and small area (S=lpm2) must be used. In this report, we will describe the first simple RSFQ circuits fabricated using two versions (A and B) of the PARTS technology [2]. The most important new feature of this technology is circuit planarization which allows superconducting contact between the counter electrode of the Nb trilayer and the wiring layer without opening a via inside the Josephson junction area S . Thus the area can be kept close to the minimum allowed by the particular patterning technology.