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Discusses the fabrication and electrical performance of an all refractory niobium-nitrogen medium scale integrated circuit process. Fabrication of Josephson junctions; Plasma etching of in situ radio frequency sputter deposited trilayers of niobium-nitrogen/magnesium-oxygen/niobium-nitrogen; Use of a deposited silicon dioxide film for wiring and resistor insulation.

We have developed a sub-μm Nb/Al-AlNx /Nb Josephson junction and integrated circuit fabrication process using deep-UV lithography and inductively coupled plasma etch tools. The baseline process consists of 11 masking steps including ground plane, PdAu resistor, Nb/A1-AlNx/Nb trilayer, and two additional Nb wiring layers. The AINx tunnel barriers are grown with plasma nitridation. These junctions exhibit low subgap leakage even at current densities exceeding 100 kA/cm2. The critical current spread of a series array of 50-kA/cm2, 0.6 μm diameter junctions is under 3%. For very high current density applications, these junctions are a good candidate to replace Nb/Al-A1Ox /Nb junctions particularly in future generations of very high speed, rapid single flux quantum logic circuits. In this paper we discuss our baseline fabrication process and device characterization including junction capacitance extraction from direct measurements of the Josephson plasma frequency. [ABSTRACT FROM AUTHOR]

Thin films of Y1Ba2Cu3O7-x (YBCO) with and without underlayers of SrTiO3 (STO) were deposited via pulsed laser deposition onto substrates of sapphire and silicon-on-sapphire (SOS) in a single vacuum step. The YBCO films with STO underlayers displayed better superconducting transitions than the YBCO films without underlayers, with zero-resistance temperatures of 86.5 and 75 K for films with underlayers on sapphire and SOS substrates, respectively. X-ray diffraction and secondary-ion mass spectroscopy have been used to explore the role played by the STO underlayer in improving film quality. [ABSTRACT FROM AUTHOR]