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ST329 - Sub-μm Josephson Junctions for Superconducting Quantum Devices
Sub-µm Josephson Junctions for Superconducting Quantum Devices
J. M. Meckbach, Member, IEEE, M. Merker, S. J. Buehler, K. Ilin,
B. Neumeier, U. Kienzle, E. Goldobin, R. Kleiner, D. Koelle, M. Siegel
Abstract - For high-performance superconducting quantum devices, based on Josephson junctions (JJs), decreasing lateral sizes is of great importance. Fabrication of sub-µm JJs is challenging, due to non-flat surfaces with step heights of up to several 100 nm generated during the fabrication process. We have refined a fabrication process with significantly decreased film thicknesses, resulting in almost flat surfaces at intermediate steps during the JJ definition. In combination with a mix-&-match process, combining electron-beam lithography (EBL) and conventional photolithography, we can fabricate JJs with lateral dimensions down to 0.023 µm². We propose this refined process as an alternative to the commonly used chemical-mechanical polishing (CMP) procedure. Transport measurements of JJs, having critical-current densities ranging from 50 to 104 A/cm² are presented at
4.2 K. Our JJ process yields excellent quality parameters, Rsg/RN up to ~50, Vm from 15 to 80 mV and Vgap up to ~50,Vm from 15 to 80 mV andVgap up to
2.81 mV, and also allows the fabrication of high-quality, sub-µm wide, long JJs (LJJs) for the study of Josephson vortex behavior. The developed technique can also be used for similar multi-layer processes and is very promising for fabricating sub-µm JJs for quantum devices such as SQUIDs, qubits and SIS mixers.
Keywords - Josephson junctions, SIS mixers
IEEE/CSC & ESAS European Superconductivity News Forum (ESNF) No. 23 January 2013; Category 4.
The published version of this preprint appeared in IEEE Transactions on Applied Superconductivity 23, 1100504 (June 2013).