NDLI: Process-Induced Variability of <formula formulatype=inline> <tex Notation=TeX>${rm Nb/Al}/{rm AlO}_{rm x}/{rm Nb}$</tex></formula> Junctions in Superconductor Integrated <newline/>Circuits and Protection Against It

Content Provider	IEEE Xplore Digital Library
Author	Tolpygo, S.K. Amparo, D. Yohannes, D.T. Meckbach, M. Kirichenko, A.F.
Copyright Year	2002
Abstract	It is shown that the critical current density, j_c of Nb/AlO_x/Nb Josephson junctions in multilayered structures such as superconductor integrated circuits depends on the junction environment and on which wiring layers make contacts to the junction electrodes, and at which stage of the fabrication process. In particular, it is shown that contact holes between the junction base electrode layer and Nb ground plane layer in proximity to the junctions increase their j_c and degrade the junction quality. This effect alone may induce enough variation in the properties of Josephson junctions in superconductor integrated circuits to significantly reduce margin of operation and yield of complex circuits. Numerous test structures have been designed, fabricated at various technological regimes, and exhaustively tested in order to investigate various phenomena leading to damage of tunnel barrier or local variation of j_c in Nb/Al/AlO_x/Nb junctions. The results indicate that layer-dependent and local environment effects on j_c are mainly due to electromigration and interlayer diffusion of impurity (hydrogen) atoms around contacts between different layers and changes in hydrogen concentration brought about by wafer processing. Based on the gained insight into the materials science of the phenomenon, methods for minimization and prevention of process-induced changes to Nb/Al/AlO_x/Nb tunnel junctions have been developed.
Sponsorship	Council on Superconductivity Appl. Superconductivity Conference Inc MIT
Starting Page	135
Ending Page	139
Page Count	5
File Size	1269545
File Format	PDF
ISSN	10518223
Volume Number	19
Issue Number	3
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2009-06-01
Publisher Place	U.S.A.
Access Restriction	One Nation One Subscription (ONOS)
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Niobium Josephson junctions Superconducting integrated circuits Superconducting epitaxial layers Electrodes Circuit testing Hydrogen Critical current density Wiring Fabrication superconducting integrated circuits Josephson device fabrication Nb/AlOx/Nb tunnel junctions
Content Type	Text
Resource Type	Article
Subject	Condensed Matter Physics Electronic, Optical and Magnetic Materials Electrical and Electronic Engineering

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Inductance of Circuit Structures for MIT LL Superconductor Electronics Fabrication Process With 8 Niobium Layers

Diffusion Stop-Layers for Superconducting Integrated Circuits and Qubits With Nb-Based Josephson Junctions

Effect of Electrical Stress on Josephson Tunneling Characteristics of ${rm Nb/Al/AlO}_{x}/{rm Nb}$ Junctions

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Improvement of Fabrication Process for 10-${rm kA/cm}^{2}$ Multi-Layer Nb Integrated Circuits

Fabrication and characterization of all-refractory NbCN/Al/AlO/sub x//Al/Nb junctions

Improved Characteristics of Intrinsically Shunted ${rm Nb/Al}-{rm AlO}_{x}-{rm Nb}$ Josephson Junctions

Process-Induced Variability of ${rm Nb/Al}/{rm AlO}_{rm x}/{rm Nb}$ Junctions in Superconductor Integrated Circuits and Protection Against It

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