SKM 2023 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 57: Poster: Superconductivity I
TT 57.21: Poster
Donnerstag, 30. März 2023, 15:00–18:00, P2/OG2
Process optimisation for the fabrication of cross-type Nb/Al-AlOx/Nb Josephson junctions — •A. Stoll, F. Bauer, L. Münch, D. Hengstler, A. Ferring-Siebert, F. Krämer, N. Kahne, D. Mazibrada, A. Fleischmann, and C. Enss — Kirchhoff-Institute for Physics, Heidelberg University, Germany.
Josephson tunnel junctions (JJs) are the basic element of many superconducting electronic devices such as qubits or superconducting quantum interference devices (SQUIDs). Since many applications demand a large number of Josephson junctions, a reliable wafer-scale fabrication process yielding JJs with a reproducible and uniform high quality is required. Very often window-type JJs are used, in which the JJ area is defined by openings in an insulating layer. The size of the JJ is thus limited by the alignment accuracy, therfore causing the need for low critical current densities jc and in turn long oxidation times. The transition to cross-type JJs is motivated by reducing the junction area as well as parasitic capacities, and in turn suppressing or completely removing parasitic effects, e.g. LC-resonances, with the additional benefit of simplistic and time efficient fabrication steps. We present how we optimised and retained the quality of our cross-type Nb/Al-AlOx/Nb junctions, for which quality checks of our in-house sputter-deposited niobium films and oxidized aluminium layers were carried out, including the measurement of the critical temperature Tc, stress of the niobium film and junction specific quality features. The parameters for the magnetron sputtering, like the Ar-pressure and power of the sputtering source, were optimised accordingly.