Side-wall spacer passivated sub-μm Josephson junction fabrication process

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    17 Citations (Scopus)


    We present a structure and a fabrication method for superconducting tunnel junctions down to the dimensions of 200 nm using i-line UV lithography. The key element is a sidewall-passivating spacer structure (SWAPS) which is shaped for smooth crossline contacting and low parasitic capacitance. The SWAPS structure enables formation of junctions with dimensions at or below the lithography-limited linewidth. An additional benefit is avoiding the excessive use of amorphous dielectric materials which is favorable in sub-Kelvin microwave applications often plagued by nonlinear and lossy dielectrics. We apply the structure to niobium trilayer junctions, and provide characterization results yielding evidence on wafer-scale scalability, and critical current density tuning in the range of 0.1-3.0 kA cm-2. We discuss the applicability of the junction process in the context of different applications, such as SQUID magnetometers and Josephson parametric amplifiers.

    Original languageEnglish
    Article number125016
    Number of pages6
    JournalSuperconductor Science and Technology
    Issue number12
    Publication statusPublished - 16 Nov 2017
    MoE publication typeA1 Journal article-refereed


    This work has received funding from the Academy of Finland through grants 287768 and 284594, and through the European Unions Horizon 2020 research and innovation programme under grant agreement No. 686865.


    • Josephson junction
    • Josephson parametric amplifier
    • magnetometer
    • spacer
    • trilayer
    • tunnel junction
    • OtaNano


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