Inductance of superconducting thin-film inductors and structures withlinewidth down to 250 nm has been experimentally evaluated. The inductorsinclude various striplines and microstrips, their 90-degree bends and meanders,interlayer vias, etc., typically used in superconducting digital circuits. Thecircuits have been fabricated by a fully planarized process with 8 niobiumlayers, developed at MIT Lincoln Laboratory for very-large-scalesuperconducting integrated circuits. Excellent run-to-run reproducibility andinductance uniformity of better than 1% across 200-mm wafers have been found.It has been found that the inductance per unit length of stripline andmicrostrip line inductors continues to grow as the inductor linewidth isreduced deep into the submicron range to the widths comparable to the filmthickness and magnetic field penetration depth. It is shown that the linewidthreduction does not lead to widening of the parameter spread due to diminishingsensitivity of the inductance to the linewidth and dielectric thickness. Theexperimental results were compared with numeric inductance extraction usingcommercial software and freeware, and a good agreement was found for 3-Dinductance extractors. Methods of further miniaturization of circuit inductorsfor achieving circuit densities > 10^6 Josephson junctions per cm^2 arediscussed.
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