Miniaturized vortex transitional Josephson memory cell by a vertically integrated device structure

We have developed the smallest Josephson nondestructive read-out (NDRO) memory cell, called a vortex transitional (VT) memory cell, for a Josephson high-speed 16-Kbit RAM. Its size is 22/spl times/22 /spl mu/m/sup 2/, which is only 16% of the size of previously developed VT memory cells used in Josephson 4-Kbit RAM. This is achieved by developing a vertically integrated device structure and refining small-junction technology. The cell consists of Nb/AlO/sub x//Nb junctions, three Nb wirings, SiO/sub 2/, insulators and Mo resistors. The VT memory cells operate properly, with a large operating margin of /spl plusmn/20%.>