Shadow evaporation is commonly used to micro-fabricate the key element of superconducting qubits - the Josephson junction. However, in conventional two-angle deposition circuit topology, unwanted stray Josephson junctions are created which contribute to dielectric loss. So far, this could be avoided by shorting the stray junctions with a so-called bandage layer deposited in an additional lithography step, which may further contaminate the chip surface. Here, we present an improved shadow evaporation technique allowing one to fabricate sub-micrometer-sized Josephson junctions together with bandage layers in a single lithography step. We also show that junction aging is significantly reduced when junction electrodes are oxidized in an oxygen atmosphere directly after deposition.
@article{arxiv.2101.01453,
title = {In-situ bandaged Josephson junctions for superconducting quantum processors},
author = {Alexander Bilmes and Alexander K. Händel and Serhii Volosheniuk and Alexey V. Ustinov and Jürgen Lisenfeld},
journal= {arXiv preprint arXiv:2101.01453},
year = {2021}
}