Characteristics of junctions and resistors fabricated using an all-NbN superconductor integrated circuit foundry process
Trilayer NbN/MgO/NbN tunnel junctions and Mo and NbN/sub x/ resistors fabricated over a NbN ground plane form the basis of a high performance, 10 K, superconductor integrated circuit foundry process. To produce high yield LSI and VLSI superconductor integrated circuits requires predictable device characteristics, stable, well-characterized, thin film deposition processes, and control of critical dimensions (CD). In this paper, we discuss improvements in thin film deposition processes, device characteristics, and CD control. Repeatable trilayer characteristics have been achieved through the use of feedback control of critical MgO and NbN sputtering parameters. Run-to-run variations in MgO film thickness have been reduced to less than /spl plusmn/1.0% (1/spl sigma/) using a novel computer feedback control technique. Improvements in MgO deposition uniformity and CD control of junction size have reduced across wafer I/sub c/ nonuniformity to less than /spl plusmn/10% (3/spl sigma/) and 100 junction array I/sub c/ nonuniformity on 0.5 cm chips to /spl plusmn/2% (1/spl sigma/). We report on the electrical characteristics of junctions and resistors and on component spreads and stability of our NbN foundry process.