Fabrication and electrical measurement of ultra-small superconducting junctions

Abstract A new type of broadband active electrically small antenna (ESA) based on superconducting quantum arrays (SQAs) has been proposed and developed. These antennas are capable of providing both sensing and amplification of broadband electromagnetic signals with a very high spurious-free dynamic range (SFDR)—up to 100 dB (and even more)—with high sensitivity. The frequency band can range up to tens of gigahertz, depending on Josephson junction characteristic frequency, set by fabrication. In this paper we review theoretical and experimental studies of SQAs and SQA-based antenna prototypes of both transformer and transformer-less types. The ESA prototypes evaluated were fabricated using a standard Nb process with critical current density 4.5 kA cm −2 . Measured device characteristics, design issues and comparative analysis of various ESA types, as well as requirements for interfaces, are reviewed and discussed.Abstract A new type of broadband active electrically small antenna (ESA) based on superconducting quantum arrays (SQAs) has been proposed and developed. These antennas are capable of providing both sensing and amplification of broadband electromagnetic signals with a very high spurious-free dynamic range (SFDR)—up to 100 dB (and even more)—with high sensitivity. The frequency band can range up to tens of gigahertz, depending on Josephson junction characteristic frequency, set by fabrication. In this paper we review theoretical and experimental studies of SQAs and SQA-based antenna prototypes of both transformer and transformer-less types. The ESA prototypes evaluated were fabricated using a standard Nb process with critical current density 4.5 kA cm −2 . Measured device characteristics, design issues and comparative analysis of various ESA types, as well as requirements for interfaces, are reviewed and discussed.

Superconductor Science and TechnologyJun 19, 201724 citations

Fabrication of Superconducting Devices and Circuits

J MMURDUCK

Elsevier eBooksJan 1, 20001 citation

Improving Josephson junction reproducibility for superconducting quantum circuits: junction area fluctuation

Anastasiya A. Pishchimova, Nikita S. Smirnov, Daria A. Moskaleva +6 more

Abstract Josephson superconducting qubits and parametric amplifiers are prominent examples of superconducting quantum circuits that have shown rapid progress in recent years. As such devices become more complex, the requirements for reproducibility of their electrical properties across a chip are being tightened. Critical current of the Josephson junction Ic is the essential electrical parameter in a chip. So, its variation is to be minimized. According to the Ambegaokar–Baratoff formula, critical current is related to normal-state resistance, which can be measured at room temperature. In this study, we focused on the dominant source of non-uniformity for the Josephson junction critical current–junction area variation. We optimized Josephson junction fabrication process and demonstrated resistance variation of 9.8–4.4% and 4.8–2.3% across 22 × 22 mm2 and 5 × 10 mm2 chip areas, respectively. For a wide range of junction areas from 0.008 to 0.12 μm2, we ensure a small linewidth standard deviation of 4 nm measured over 4500 junctions with linear dimensions from 80 to 680 nm. We found that the dominate source of junction area variation limiting ${\mathrm{I}}_{\mathrm{c}}$ I c reproducibility is the imperfection of the evaporation system. The developed fabrication process was tested on superconducting highly coherent transmon qubits (T1 > 100 μs) and a nonlinear asymmetric inductive element parametric amplifier.Abstract Josephson superconducting qubits and parametric amplifiers are prominent examples of superconducting quantum circuits that have shown rapid progress in recent years. As such devices become more complex, the requirements for reproducibility of their electrical properties across a chip are being tightened. Critical current of the Josephson junction Ic is the essential electrical parameter in a chip. So, its variation is to be minimized. According to the Ambegaokar–Baratoff formula, critical current is related to normal-state resistance, which can be measured at room temperature. In this study, we focused on the dominant source of non-uniformity for the Josephson junction critical current–junction area variation. We optimized Josephson junction fabrication process and demonstrated resistance variation of 9.8–4.4% and 4.8–2.3% across 22 × 22 mm2 and 5 × 10 mm2 chip areas, respectively. For a wide range of junction areas from 0.008 to 0.12 μm2, we ensure a small linewidth standard deviation of 4 nm measured over 4500 junctions with linear dimensions from 80 to 680 nm. We found that the dominate source of junction area variation limiting $${\mathrm{I}}_{\mathrm{c}}$$ I c reproducibility is the imperfection of the evaporation system. The developed fabrication process was tested on superconducting highly coherent transmon qubits (T1 > 100 μs) and a nonlinear asymmetric inductive element parametric amplifier.

arXiv:2210.15293Scientific ReportsApr 25, 202339 citations

Fabrication of three-dimensional superconducting tunnel junctions

Go Fujii, Masahiro Ukibe, Shigetomo Shiki +1 more

IEICE Technical Report; IEICE Tech. Rep.Oct 8, 20140 citations

Superconducting electronics: current status and future prospects

Marty Nisenoff

CryogenicsJan 1, 198830 citations

Fabrication of deep-sub-micrometer NbN/AlN/NbN epitaxial junctions on a Si-substrate

Wei Qiu, Hirotaka Terai

We have developed a novel fabrication process for ultra-small, full-epitaxial NbN Josephson junctions on a TiN buffered silicon (Si) substrate. We use an electron beam lithography for junction definition followed by a reactive-ion-etch (RIE). A chemical mechanical polishing process and an RIE by using CHF 3 gas formed reliable electrical contacts for the junction electrodes. All junctions, with a junction size down to 0.27 μ m in diameter, showed excellent current–voltage characteristics with a clear gap and small sub-gap leakage current. We have confirmed that the quality of the junctions was maintained after the removal of the SiO 2 dielectric interlayer.We have developed a novel fabrication process for ultra-small, full-epitaxial NbN Josephson junctions on a TiN buffered silicon (Si) substrate. We use an electron beam lithography for junction definition followed by a reactive-ion-etch (RIE). A chemical mechanical polishing process and an RIE by using CHF 3 gas formed reliable electrical contacts for the junction electrodes. All junctions, with a junction size down to 0.27 μ m in diameter, showed excellent current–voltage characteristics with a clear gap and small sub-gap leakage current. We have confirmed that the quality of the junctions was maintained after the removal of the SiO 2 dielectric interlayer.

arXiv:2004.00922Applied Physics ExpressOct 9, 202013 citations

{\mathrm{I}}_{\mathrm{c}}

I c reproducibility is the imperfection of the evaporation system. The developed fabrication process was tested on superconducting highly coherent transmon qubits (T1 > 100 μs) and a nonlinear asymmetric inductive element parametric amplifier.