A self-aligned nano-fabrication process for vertical NbN-MgO-NbN Josephson junctions

  1. A. Grimm,
  2. S. Jebari,
  3. D. Hazra,
  4. F. Blanchet,
  5. F. Gustavo,
  6. J.-L. Thomassin,
  7. and M. Hofheinz
We present a new process for fabricating vertical NbN-MgO-NbN Josephson junctions using self-aligned silicon nitride spacers. It allows for a wide range of junction areas from 0.02 um^2 to several 100 um^2. At the same time, it is suited for the implementation of complex microwave circuits with transmission line impedances ranging from < 1 Ohm to > 1 kOhm. The constituent thin films and the finished junctions are characterized. The latter are shown to have high gap voltages (> 4 mV) and low sub-gap leakage currents.
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