SUB-MU-M LINEWIDTH INPUT COILS FOR LOW T(C) INTEGRATED THIN-FILM DC SUPERCONDUCTING QUANTUM INTERFERENCE DEVICES

We have, for the first time, demonstrated integrated dc superconducting quantum interference devices (SQUIDs) with input coils of linewidth down to 0.5-mu-m. The SQUID inductance L consists of a single octagonal washer or two or four such washers configured in parallel. The input coil of inductance L(i), which couples to L with a mutual inductance of M(i), consists of fine-line octagonal spiral(s) fabricated in close proximity to the washer(s). For a two-washer SQUID with twin 80-turn, 0.5-mu-m spirals, L(i)=2.5-mu-H, M(i)=12.7 nH, L=109 pH, and the coupling constant k2=0.85. This entire device occupies an area of less than 0.2 mm2.