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The effect of photomask pattern shape for a counter-electrode on critical current (I(sub c)) uniformity and controllability in Nb/AlO(sub x)/Nb junctions is evaluated. Although no difference is found in the (I(sub c)) uniformity between square and OPC junctions, the OPC junctions exhibited smaller shrinkage in junction size than the square junction.

The authors evaluated the effect of photomask pattern shape for a counter-electrode on critical current Ic uniformity and controllability in Nb/AlOx/Nb junctions. Circular, square, and 2 kinds of optical proximity correction (OPC) square patterns were used as the mask pattern shape. Although there was no difference in the Ic uniformity between square and OPC junctions, the OPC junctions exhibited smaller shrinkage in junction size than the square junction. In addition, the OPC junctions improved the chip-to-chip variation in the shrinkage. The circular junction exhibited the smallest variation in the shrinkage, and had an ad- vantage in 4 uniformity for smaller than 1.0 μm² junctions in comparison with the other junctions. The shrinkage of the circular junction was the largest of all the junctions. This paper describes the recommended choice of the photomask pattern shape for several Nb LSI technologies. [ABSTRACT FROM AUTHOR]

We developed an 8.5 /spl mu/m/spl times/11.5 /spl mu/m vortex transitional (VT) memory cell. The memory cell is the smallest Josephson memory cell ever reported. The cell was fabricated by electron cyclotron resonance plasma etching and bias-sputtering planarization. This is also the first Josephson circuit fabricated with sub-micron minimum feature size. Proper nondestructive read-out operation was verified even after half-selected conditions. An operating margin of /spl plusmn/14% was obtained for control currents I/sub X/ and I/sub Y/. These results are promising for developing a 1-Mbit/cm/sup 2/ density Josephson RAM. [ABSTRACT FROM PUBLISHER]