In situ spectroscopic ellipsometry of SIS barrier formation

Cyberey, Michael E.; Lichtenberger, Arthur W.

doi:10.1109/irmmw-thz.2014.6956458

Cited by 3 publications

(3 citation statements)

References 4 publications

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“…The resulting thicknesses, as determined by in-situ ellipsometry (discussed elsewhere [8], [13]), at 30 s nitridation time are plotted in Fig. 6 vs the RD of the ICP.…”

Section: B Effects Of Dissociation On Aln Growthmentioning

confidence: 99%

Optical Spectroscopic Analysis of ICP Nitridation for SIS Junctions With AlN Barriers

Cyberey

Oakland

Zhang

et al. 2015

IEEE Trans. Appl. Supercond.

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High quality, low-leakage superconductorinsulatorsuperconductor (SIS) junctions with Nb electrodes and aluminum oxide barriers are widely reported in the literature, and have become integral in the design and fabrication of various superconducting circuits. However, as current densities are increased, aluminum oxide based tunnel barriers show excess leakage currents due to defects and pinholes in the barrier layer. First reported by our group in 2007, AlN tunnel barriers grown via inductively coupled plasma (ICP) nitridation of Al overlayers are a promising alternative, producing low-leakage Nb/Al-AlN/Nb SIS junctions, with current densities in excess of 30 kA/cm 2 . A correlation between junction quality and plasma dissociation has been reported for Nb/Al-AlN/Nb junctions produced via an electron cyclotron resonance (ECR) plasma. In this work, a quantitative measure of the relative dissociation (RD) of an ICP is determined through the use of a commercially available Ocean Optics USB4000 Optical Spectrometer. The effects of various ICP parameters on the RD, and a correlation between the RD and quality of the resulting Nb/Al-AlN/Nb junctions are reported.Index Terms-Aluminum nitride, inductively coupled plasma, superconductorinsulatorsuperconductor (SIS), spectroscopy. 1051-8223

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“…The resulting thicknesses, as determined by in-situ ellipsometry (discussed elsewhere [8], [13]), at 30 s nitridation time are plotted in Fig. 6 vs the RD of the ICP.…”

Section: B Effects Of Dissociation On Aln Growthmentioning

confidence: 99%

Optical Spectroscopic Analysis of ICP Nitridation for SIS Junctions With AlN Barriers

Cyberey

Oakland

Zhang

et al. 2015

IEEE Trans. Appl. Supercond.

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“…With this software it is possible to select a physical model and fit with data acquired by means spectroscopic ellipsometry. For the data presented in this work an ellipsometric growth model, similar to that reported in [23] for Al-AlN tunnel barrier growth, was used to track the real-time oxide growth in situ. The optically thin Al overlaye was modeled using a sum of Lorentz and a single Drude Oscillator, the Al-oxide layer was modeled using a Cauchy-Urbach dispersion, and all optically thick Nb and Al films were modeled using pseudo optical constants obtained by directly inverting the ellipsometry equations from a single measurement.…”

Section: Methodsmentioning

confidence: 99%

“…Films were exposed to undiluted and diluted oxygen under both dynamic and static thermal oxidation settings for 8100 seconds and the thickness profile of each oxidation process was recorded in situ by the ellipsometer with a 25 µm by 60 µm spot size from just off the center of wafer. The optical constants of Al overlayer film were modeled using a sum of four Lorentz and a single Drude oscillators [23].…”

Section: A Initial Study-alo X Thickness Repeatabilitymentioning

confidence: 99%

Optical Spectroscopic Study of AlN-Based SIS Devices Grown by Inductively Coupled Plasma

Farrahi¹,

Cyberey²,

Eller³

et al. 2019

IEEE Trans. Appl. Supercond.

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High quality Nb-based superconductor-insulatorsuperconductor (SIS) junctions with Al oxide (AlOx) tunnel barriers grown from Al overlayers are widely reported in the literature. However, the thin barriers required for high critical current density (Jc) junctions exhibit defects that result in significant subgap leakage current that is detrimental for many applications. High quality, high-Jc junctions can be realized with AlNx barriers, but control of Jc is more difficult than with AlOx. It is therefore of interest to study the growth of thin AlOx barriers with the ultimate goal of achieving high quality, high-Jc AlOx junctions. In this work, 100% O2 and 2% O2 in Ar gas mixtures are used both statically and dynamically to grow AlOx tunnel barriers over a large range of oxygen exposures. In situ ellipsometry is used for the first time to extensively measure AlOx tunnel barrier growth in real time, revealing a number of unexpected patterns. Finally, a set of test junction wafers was fabricated that exhibited the well-known dependence of Jc on oxygen exposure (E) in order to further validate the experimental setup.

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NbTiN/AlN/NbTiN SIS Junctions Realized by Reactive Bias Target Ion Beam Deposition

Cyberey

Farrahi

et al. 2019

IEEE Trans. Appl. Supercond.

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In situ spectroscopic ellipsometry of SIS barrier formation

Cited by 3 publications

References 4 publications

Optical Spectroscopic Analysis of ICP Nitridation for SIS Junctions With AlN Barriers

Optical Spectroscopic Analysis of ICP Nitridation for SIS Junctions With AlN Barriers

Optical Spectroscopic Study of AlN-Based SIS Devices Grown by Inductively Coupled Plasma

NbTiN/AlN/NbTiN SIS Junctions Realized by Reactive Bias Target Ion Beam Deposition

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