Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Softwaretechnik-Trends

Superconducting Devices for Radioastronomy; First Steps in Chile: SNS-junction Fabrication

V. Conte, José Luis Giordano, Javier Luzuriaga, Juan Zarate, H. Pastoriza

Published Mar 1, 2010• 0 citations
OpenAlex

Abstract

We present results of the microfabrication of Josephson Junctions (JJs) of Superconductor-Normal-superconductor (SNS) type, as a first step in the acquisition of the know-how of superconducting devices applied to radioastronomy. A twojunction SQUID was built using a Nb/Al bilayer deposited on a Si wafer. The procedure needs only one mask and a single UV exposure (i.e., one photolithography step). We show the micrograph and the observed non linear characteristic I-V curve at 4K of the first device fabricated in the framework of ALMA Grant 31090010.

Related papers

SNS and SIS Josephson junctions with dimensions down to the submicron region prepared by a unified technology

Ludwig Fritzsch, H. Elsner, M. Schubert +1 more

Several applications of Josephson junctions (JJs) in low-temperature superconducting circuits such as programmable voltage standards and SFQ logical circuits or SQUID sensors require JJs with sub-µm dimensions. A method for preparing superconductor-isolator-superconductor (SIS) JJs as well as superconductor-normal metal-superconductor (SNS) JJs was developed which allows the preparation of both types of junctions by nearly the same technological process. Titanium is used as the normal metal for the SNS JJ. Ti can be anodically oxidized and a technology similar to the well-tried Nb-Al technology for SIS JJs can be applied to the SNS system, too. By electron-beam exposure of a negative deep UV photoresist (ma-N 2400) a stable resist mask is generated which has to withstand the following three self-aligned process steps: etching of the Nb counterelectrode by RIE, isolation by anodization and lifting of a SiO planarization layer. By this process SNS (Nb-Ti-Nb) and SIS (Nb-Al/AlO x -Nb) Josephson junctions with smallest junction areas of 0.49 µm 2 were prepared and characterized by dc measurements and under the influence of microwave irradiation. The Nb-Ti-Nb junctions have I c R n products of 87 µV. They can be used for programmable Josephson voltage standard circuits at frequencies of 70 GHz.

Superconductor Science and Technology•Nov 1, 1999•9 citations

Planar SNS Josephson junctions using multilayer Bi system

Kentaro Setsune, Koichi Mizuno, Hidetaka Higashino +1 more

Planar S/N/S Josephson junctions were successfully fabricated by multi-layered thin films of Bi-based high-Tc oxide superconductors. Two Bi2Sr2Ca1Cu2O(x) films and Bi2Sr2Cu1O(y) film were successively layered as superconducting electrodes and normal conducting buffer layer, respectively. These films were epitaxially deposited on (100) MgO substrate by in situ process of RF magnetron sputtering. Microjunction areas were defined by photolithography and Ar ion milling. These S/N/S type junctions clearly exhibited the AC Josephson effect under the irradiation of radio frequency waves of 12 GHz. More than 20th Shapiro steps were observed and those step heights were oscillated according to the irradiation power. These characteristics were stable and reproducible for different configuration of function area.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Mar 1, 1991•1 citation

SNS junction on Nb-Ti base for microwave circuits

M. Schubert, Ludwig Fritzsch, G. Wende +1 more

Superconductor-normal metal-superconductor (SNS) junctions are well-suited for large-scale integrated superconducting circuits. Potential applications are programmable voltage standards, digital-to-analog converters and large-scale RSFQ circuits. The application of SNS junctions provides some advantages, e.g. a simplified fabrication technology and reduced parasitic inductances. But it requires a technological process with dimensions down to the submicrometer region to achieve sufficiently high characteristic voltages I/sub C/R/sub N/. In our process the normal metal interlayer is titanium. Therefore the sidewall insulation of the junctions can be made by anodization, as it is known from the Nb-Al technology. Nb-Ti-Nb Josephson junctions and junction arrays were fabricated down to the submicrometer range with I/sub C/R/sub N/ values up to 87 microvolt depending on the titanium thickness. Their measured critical currents have a small spread of about 10 percent. Shapiro steps are observed under the influence of microwave irradiation. For the application of such junctions in a programmable Josephson voltage standard a new type of microwave circuit using coplanar strips is proposed and successfully tested in 10 V SIS circuits.

IEEE Transactions on Applied Superconductivity•Mar 1, 2001•12 citations

A simple method to fabricate Josephson junctions

Imran Mahboob, Satoshi Sasaki, Takaaki Takenaka

A minimal method to fabricate Al/AlO$_x$/Al Josephson junctions (JJs) using photolithography and argon etching, before metallization and oxidation, is demonstrated. JJs with areas ranging from 1 to 6 $μ$m$^2$ can be fabricated and, with the appropriate oxidation conditions, the junction resistance can be varied by $\sim$2 orders of magnitude. Transmission electron microscopy reveals the successful fabrication of JJs with few grain boundaries suggesting reduced energy loss from two-level-systems. Superconducting QUantum Interference Devices (SQUIDs) fabricated from this methodology exhibit reduced resistance variation over multiple chips, compared with electron beam lithography, and the devices can sustain repeated thermal cycles to 10 mK with the excellent flux response remaining unchanged. The quantum applications of this technology are demonstrated by embedding a SQUID resonator into a 3D cavity and parametrically amplifying low photon numbers with gains of $\sim$40 dB. This work establishes the simplest approach to fabricating JJs to date, and it could prove pivotal to the widespread utilization of superconducting circuit-based quantum technologies.

quant-pharXiv:2604.25195•Apr 29, 2026•0 citations

Superconductor-normal metal-superconductor process development for the fabrication of small Josephson junctions in ramp type configuration

R. Pöpel, Daniel Hagedorn, Thomas Weimann +2 more

At PTB, a fabrication process has been developed in SNS Nb/PdAu/Nb technology for the verification of small Josephson junctions (JJs) in the deep sub-micron range to enable the implementation of JJs as active elements in highly integrated superconducting circuits. Two steps of this technological development are described with regard to appropriately designed circuit layouts of JJ series arrays (JJAs), the first one in a conventional window type junction (WTJ) configuration and the second one in a ramp type junction (RTJ) configuration. Test circuits of JJAs containing up to 10 000 JJs have been fabricated and experimentally tested. In WTJ configuration, the circuits proved to be sensitive to external perturbing effects affecting the stability of circuit operation. In contrast to that, in RTJ configuration, the circuits realized showed correct function and a high grade of reliability of operation. To produce RTJ circuits, the technology parameters have been set to realize JJs with contact areas of A = 0.25 µm × 1.3 µm. At a thickness of the PdAu normal metal layer of d = 40 nm, the values achieved for the critical current density and for the product of critical current and normal state resistance are about jc = 200 kA cm-2 and about Ic RN = 21 µV.

Superconductor Science and Technology•Jan 19, 2000•20 citations

Towards Fabrication of Sub-Micrometer Cross-Type Aluminum Josephson Junctions

Stephan Mechold, Katja Peiselt, Matthias Schmelz +5 more

The performance of superconducting electronic devices such as superconducting quantum bits (qubits) and superconducting quantum interference devices (SQUIDs) strongly relies on high-quality Josephson junctions (JJ) and their integration into surrounding circuit elements. Therefore, a corresponding fabrication technology should allow for the fabrication of all required elements including the JJs, inductances, capacitances and waveguides. For a long time, shadow evaporation technique was the state of the art for the implementation of sub-μ m sized JJs based on aluminum for qubits of high coherence times. Although, the use of a single lithographic step represents a major advantage of this technique. However, shadowing effects limit sample size, device complexity, and thus scalability of the circuitry. To overcome these limitations and to meet the demands of next generation scalable quantum circuits, in this work we introduce our cross -type JJ aluminum technology, where JJs are defined by the overlap of two narrow perpendicular stripes. We discuss the technological challenges, with a focus on our newly developed dry etching process for patterning of the aluminum thin film. Compared to a lift-off based process, this advanced wafer-scale fabrication technology offers a high integration density and the required design flexibility. We will present first results on cross -type aluminum JJs.

IEEE Transactions on Applied Superconductivity•Dec 18, 2023•2 citations
We present results of the microfabrication of Josephson Junctions (JJs) of Superconductor-Normal-superconductor (SNS) type, as a first step in the acquisition of the know-how of superconducting devices applied to radioastronomy. A twojunction SQUID was built using a Nb/Al bilayer deposited on a Si wafer. The procedure needs only one mask and a single UV exposure (i.e., one photolithography step). We show the micrograph and the observed non linear characteristic I-V curve at 4K of the first device fabricated in the framework of ALMA Grant 31090010.
Several applications of Josephson junctions (JJs) in low-temperature superconducting circuits such as programmable voltage standards and SFQ logical circuits or SQUID sensors require JJs with sub-µm dimensions. A method for preparing superconductor-isolator-superconductor (SIS) JJs as well as superconductor-normal metal-superconductor (SNS) JJs was developed which allows the preparation of both types of junctions by nearly the same technological process. Titanium is used as the normal metal for the SNS JJ. Ti can be anodically oxidized and a technology similar to the well-tried Nb-Al technology for SIS JJs can be applied to the SNS system, too. By electron-beam exposure of a negative deep UV photoresist (ma-N 2400) a stable resist mask is generated which has to withstand the following three self-aligned process steps: etching of the Nb counterelectrode by RIE, isolation by anodization and lifting of a SiO planarization layer. By this process SNS (Nb-Ti-Nb) and SIS (Nb-Al/AlO x -Nb) Josephson junctions with smallest junction areas of 0.49 µm 2 were prepared and characterized by dc measurements and under the influence of microwave irradiation. The Nb-Ti-Nb junctions have I c R n products of 87 µV. They can be used for programmable Josephson voltage standard circuits at frequencies of 70 GHz.
Planar S/N/S Josephson junctions were successfully fabricated by multi-layered thin films of Bi-based high-Tc oxide superconductors. Two Bi2Sr2Ca1Cu2O(x) films and Bi2Sr2Cu1O(y) film were successively layered as superconducting electrodes and normal conducting buffer layer, respectively. These films were epitaxially deposited on (100) MgO substrate by in situ process of RF magnetron sputtering. Microjunction areas were defined by photolithography and Ar ion milling. These S/N/S type junctions clearly exhibited the AC Josephson effect under the irradiation of radio frequency waves of 12 GHz. More than 20th Shapiro steps were observed and those step heights were oscillated according to the irradiation power. These characteristics were stable and reproducible for different configuration of function area.
Superconductor-normal metal-superconductor (SNS) junctions are well-suited for large-scale integrated superconducting circuits. Potential applications are programmable voltage standards, digital-to-analog converters and large-scale RSFQ circuits. The application of SNS junctions provides some advantages, e.g. a simplified fabrication technology and reduced parasitic inductances. But it requires a technological process with dimensions down to the submicrometer region to achieve sufficiently high characteristic voltages I/sub C/R/sub N/. In our process the normal metal interlayer is titanium. Therefore the sidewall insulation of the junctions can be made by anodization, as it is known from the Nb-Al technology. Nb-Ti-Nb Josephson junctions and junction arrays were fabricated down to the submicrometer range with I/sub C/R/sub N/ values up to 87 microvolt depending on the titanium thickness. Their measured critical currents have a small spread of about 10 percent. Shapiro steps are observed under the influence of microwave irradiation. For the application of such junctions in a programmable Josephson voltage standard a new type of microwave circuit using coplanar strips is proposed and successfully tested in 10 V SIS circuits.
A minimal method to fabricate Al/AlOx_xx​/Al Josephson junctions (JJs) using photolithography and argon etching, before metallization and oxidation, is demonstrated. JJs with areas ranging from 1 to 6 μμμm2^22 can be fabricated and, with the appropriate oxidation conditions, the junction resistance can be varied by $\sim$2 orders of magnitude. Transmission electron microscopy reveals the successful fabrication of JJs with few grain boundaries suggesting reduced energy loss from two-level-systems. Superconducting QUantum Interference Devices (SQUIDs) fabricated from this methodology exhibit reduced resistance variation over multiple chips, compared with electron beam lithography, and the devices can sustain repeated thermal cycles to 10 mK with the excellent flux response remaining unchanged. The quantum applications of this technology are demonstrated by embedding a SQUID resonator into a 3D cavity and parametrically amplifying low photon numbers with gains of $\sim$40 dB. This work establishes the simplest approach to fabricating JJs to date, and it could prove pivotal to the widespread utilization of superconducting circuit-based quantum technologies.
At PTB, a fabrication process has been developed in SNS Nb/PdAu/Nb technology for the verification of small Josephson junctions (JJs) in the deep sub-micron range to enable the implementation of JJs as active elements in highly integrated superconducting circuits. Two steps of this technological development are described with regard to appropriately designed circuit layouts of JJ series arrays (JJAs), the first one in a conventional window type junction (WTJ) configuration and the second one in a ramp type junction (RTJ) configuration. Test circuits of JJAs containing up to 10 000 JJs have been fabricated and experimentally tested. In WTJ configuration, the circuits proved to be sensitive to external perturbing effects affecting the stability of circuit operation. In contrast to that, in RTJ configuration, the circuits realized showed correct function and a high grade of reliability of operation. To produce RTJ circuits, the technology parameters have been set to realize JJs with contact areas of A = 0.25 µm × 1.3 µm. At a thickness of the PdAu normal metal layer of d = 40 nm, the values achieved for the critical current density and for the product of critical current and normal state resistance are about jc = 200 kA cm-2 and about Ic RN = 21 µV.
The performance of superconducting electronic devices such as superconducting quantum bits (qubits) and superconducting quantum interference devices (SQUIDs) strongly relies on high-quality Josephson junctions (JJ) and their integration into surrounding circuit elements. Therefore, a corresponding fabrication technology should allow for the fabrication of all required elements including the JJs, inductances, capacitances and waveguides. For a long time, shadow evaporation technique was the state of the art for the implementation of sub-μ m sized JJs based on aluminum for qubits of high coherence times. Although, the use of a single lithographic step represents a major advantage of this technique. However, shadowing effects limit sample size, device complexity, and thus scalability of the circuitry. To overcome these limitations and to meet the demands of next generation scalable quantum circuits, in this work we introduce our cross -type JJ aluminum technology, where JJs are defined by the overlap of two narrow perpendicular stripes. We discuss the technological challenges, with a focus on our newly developed dry etching process for patterning of the aluminum thin film. Compared to a lift-off based process, this advanced wafer-scale fabrication technology offers a high integration density and the required design flexibility. We will present first results on cross -type aluminum JJs.