Retargeting RSFQ cells to a submicron fabrication process

There is a desire to move current state-of-the-art niobium Josephson IC fabrication processes (~3 μm) to smaller sub-micron linewidths in order to realize a decrease in gate size and increase in both speed and packing density. However, cost and time dictates that a way be found to reuse the existing RSFQ gate/cell development that has been done at the 3-μm level. Cell retargeting is the process of migrating existing designs to a new technology, with the effort focused on the maximum reuse of existing material. We have investigated a number of issues critical to this process, including both the physical and electrical aspects. Comments are made on methodologies for RSFQ cell retargeting with respect to existing reduced-linewidth JJ fabrication processes. Experimental demonstrations are shown for retargeted RSFQ static digital frequency dividers (toggle flip-flops) operating at 220 GHz, 240 GHz, and 395 GHz