Fabrication of high quality Nb/AlO/sub /x-Al/Nb Josephson junctions. III. Annealing stability of AlO/sub /x tunneling barriers

Shiota, T.; Imamura, Takeshi; Hasuo, S.

doi:10.1109/77.182734

Cited by 29 publications

(19 citation statements)

References 12 publications

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“…However, as superconducting applications mature and begin to demand whole-wafer technology, it becomes necessary to ensure that post-fabrication processes do not adversely affect device quality. It is well known that thermal annealing, as might occur in bump-bonding processes, can reduce device quality through physical changes to the tunneling barrier in Josephson junctions at temperatures as low as 125 C [3], [4]. This degradation is normally observed as a reduction in critical current and increased sub-gap leakage.…”

Section: Introductionmentioning

confidence: 98%

Thermal annealing of Nb/Al-AlO/sub x//Nb Josephson junctions

Migacz¹,

Huber

2003

IEEE Trans. Appl. Supercond.

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We thermally annealed single un-shunted Josephson junctions at temperatures of 110 to 270 C for durations of 2.5 to 90 minutes. We also exposed some junctions for three separate 15-minute periods in order to compare the result with that of a continuous 45-minute exposure. After annealing, we measured the changes in junction properties such as critical current , normal state resistance , and junction quality parameter . decreases with increased exposure, (starting at approximately 125 C) andincreases, such that the product remains roughly constant up to 200 C, at which point also begins to decrease.declines slightly with increased exposure, but with a large amount of scatter. Samples with interrupted exposures degraded less than if annealed continuously. Based on our results, we find that junctions can tolerate an exposure of up to 90 minutes at temperatures as high as 200 C without significant degradation in performance, though allowances will need to be made for shifts in critical current. Junctions exposed for up to 15 minutes at 225 C are degraded further but may still function well enough for some applications.

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Section: Introductionmentioning

confidence: 98%

Thermal annealing of Nb/Al-AlO/sub x//Nb Josephson junctions

Migacz¹,

Huber

2003

IEEE Trans. Appl. Supercond.

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“…Since an annealing above 200°C deteriorates the characteristics of Nb/AlOx-Al/Nb junctions [ 101, [ 111, the process temperature has been limited up to 200°C. Recently, however, many efforts have been focused on improvement of the annealing stability [12], [13]. In future, annealing at higher temperatures will be probably used in circuit fabrication or chip-packaging processes.…”

Section: Annealing Stabilitymentioning

confidence: 99%

High-resistivity Zr resistors with Ti barrier layer for Nb Josephson circuits

Shiota

Ohara

Imamura

et al. 1993

IEEE Trans. Appl. Supercond.

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We apply Zr resistors to Josephson integrated circuits in place of MO because a Zr thin film has about five times the resistivity of MO. Zr resistors do not need to be protected during etching, unlike conventional MO resistors, because Zr has much smaller etching rate than Nb. Zr resistors occupy only 25% of a unit cell area. Using Zr resistors reduces the area of the Josephson gate and allows increased circuit integration. We found increased contact resistance between Zr and Nb films after annealing about 350°C but suppressed it with a Ti barrier. We were able to fabricate resistors with a resistance variation throughout a wafer of within 2.8%.

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“…275°C, AlO x barrier apparently grows due to diffusion of oxygen through the junction's counter electrode. 3,4 However, there are experimental facts, which do not fit the suggested trend and cannot be explained within the same approach. In the number of studies, unusual drop of R n value of Nb/ Al-AlO x / Nb ͑Refs.…”

Section: Introductionmentioning

confidence: 99%

“…[3][4][5][6][7][8][9][10] The interest to this subject was constantly supported by applications 11,12 and related to that life-time and reliability questions. An increase in the junction normal state resistance R n ͑decrease in critical current I c ͒ followed by further degradation of its characteristics at even higher temperatures, seemed to be a commonly agreed trend.…”

Section: Introductionmentioning

confidence: 99%

Aging- and annealing-induced variations in Nb/Al–AlOx/Nb tunnel junction properties

Pavolotsky

Dochev

Belitsky

2011

Journal of Applied Physics

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In this paper, we present studies of room temperature aging and annealing of Nb/ Al-AlO x / Nb tunnel junctions with the size of 2 -3 m 2 . We observed a noticeable drop of junction normal resistance R n unusually combined with increase in subgap resistance R j as a result of aging. Variation in both R n and R j are subject to the junction size effect. An effect of aging history on the junction degradation after consequent annealing was discovered. Discussion and interpretation of the observed phenomena are presented in terms of structural ordering and reconstruction in the AlO x layer, driven by diffusion flows enhanced due to stress relaxation processes in the Al layer interfacing the AlO x layer.

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Fabrication of high quality Nb/AlO/sub /x-Al/Nb Josephson junctions. III. Annealing stability of AlO/sub /x tunneling barriers

Cited by 29 publications

References 12 publications

Thermal annealing of Nb/Al-AlO/sub x//Nb Josephson junctions

Thermal annealing of Nb/Al-AlO/sub x//Nb Josephson junctions

High-resistivity Zr resistors with Ti barrier layer for Nb Josephson circuits

Aging- and annealing-induced variations in Nb/Al–AlOx/Nb tunnel junction properties

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