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

Abstract

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 side-wall-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.

arXiv comment8 pages, 4 figures

References in corpus (5)

• Decoherence in Josephson Qubits from Dielectric Loss
• Fabrication of stable and reproducible sub-micron tunnel junctions
• Coherence and multimode correlations from vacuum fluctuations in a microwave superconducting cavity
• Overlap junctions for high coherence superconducting qubits
• Fabrication process-induced variations of Nb/Al/AlOx/Nb Josephson junctions in superconductor integrated circuits

Cited by in corpus (9)

• Investigation of microwave loss induced by oxide regrowth in high-Q Nb resonators
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• Characterizing cryogenic amplifiers with a matched temperature-variable noise source
• A low-noise on-chip coherent microwave source
• Circuit quantum electrodynamic model of dissipative-dispersive Josephson traveling-wave parametric amplifiers
• Flux-driven Josephson parametric amplifier for sub-GHz frequencies fabricated with side-wall passivated spacer junction technology
• Efficient electronic cooling above 2 K by niobium-based superconducting tunnel junctions
• Low barrier ZrO${}_x$-based Josephson junctions
• Coulomb Blockade Thermometry on a Wide Temperature Range