A NEW DESIGN APPROACH FOR HIGH-T-C BASED RSFQ LOGIC

We suggest a new design of Rapid Single Flux Quantum (RSFQ) logic circ uits which is based on a single superconducting layer and does not req uire a superconducting ground plane. The small inductances of about 10 pH, that are obligatory for the RSFQ applications, are formed as narro w slits with width comparable to the London penetration depth (congrue nt to 0.15 mu m). The design allows us to decrease the geometric size of the RSFQ cell and can be applied to low- T-c circuits as well. Test circuits have been implemented using YBaCuO grain boundary junctions on asymmetric 32 degrees Y-ZrO2 bi-crystals to measure the slit induct ance per unit length and the mutual inductance of neighboring slits. A typical inductance of a 0.4 mu m slit was determined to be 0.7pH/mu m . We present a new design and a computer simulation of a flip-flop cir cuit based on these inductance measurements. To realize these circuits experimentally one needs at least two grain boundaries, separated by a distance of 10 to 15 mu m, or to use bi-epitaxial or step-edge junct ion technology.