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Wafer-Scale Electrical Characterization of Al/Al x O y /Al Tunnel Junctions for Process Monitoring at Room Temperature.

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Title: Wafer-Scale Electrical Characterization of Al/Al x O y /Al Tunnel Junctions for Process Monitoring at Room Temperature.
Authors: Lang, Simon Johann Klaus1 (AUTHOR) ignaz.eisele@emft.fraunhofer.de, Eisele, Ignaz1,2 (AUTHOR), Weber, Johannes1,3 (AUTHOR), Schewski, Alexandra1 (AUTHOR), Music, Emir1,2 (AUTHOR), Maiwald, Alwin1,3 (AUTHOR), Hahn, Martin1 (AUTHOR), Zahn, Daniela1 (AUTHOR), Luo, Zhen3 (AUTHOR), Nebrich, Lars1 (AUTHOR), Schoof, Benedikt3 (AUTHOR), Mayer, Thomas1 (AUTHOR), Sturm-Rogon, Leonhard1 (AUTHOR), Lerch, Wilfried1 (AUTHOR), Pereira, Rui Nuno1 (AUTHOR), Kutter, Christoph1,2 (AUTHOR) christoph.kutter@emft.fraunhofer.de
Source: Nanomaterials (2079-4991). May2026, Vol. 16 Issue 10, p569. 11p.
Subjects: Tunnel junctions (Materials science), Electric measurements, Surface defects, Josephson junctions, Complementary metal oxide semiconductors, Oxide coating
Abstract: Josephson junctions are key elements in superconducting qubits. Their efficient wafer-scale characterization is crucial for process control and optimization, motivating analysis approaches that extend beyond conventional cryogenic measurements. In this work, we demonstrate that room temperature (RT) capacitance and current–voltage measurements, combined with appropriate data analysis, enable extraction of relevant junction parameters such as oxide thickness, tunnel coefficient, and interfacial defect density. Furthermore, different charge transport mechanisms can be identified from detailed current–voltage analysis. We evaluate our characterization technique using tunnel junctions fabricated on 200 mm wafers in a complementary metal–oxide–semiconductor (CMOS)-compatible subtractive process. The results show a homogeneous average oxide thickness across the wafer with a variation below 3%. A dependence of the tunnel coefficient on oxide thickness indicates a stoichiometry gradient within the oxide. Additionally, low interfacial defect densities in the range of 70–5000 defects/cm2 are observed in our junctions, increasing with decreasing oxide thickness, suggesting that wet etching used for thickness control introduces interfacial trap states. Our study highlights the importance of advanced RT characterization for extracting tunnel junction parameters on the wafer scale, enabling effective process monitoring and optimization in industrial superconducting qubit manufacturing. [ABSTRACT FROM AUTHOR]
Copyright of Nanomaterials (2079-4991) is the property of MDPI and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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  Data: Wafer-Scale Electrical Characterization of Al/Al x O y /Al Tunnel Junctions for Process Monitoring at Room Temperature.
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  Data: <searchLink fieldCode="AR" term="%22Lang%2C+Simon+Johann+Klaus%22">Lang, Simon Johann Klaus</searchLink><relatesTo>1</relatesTo> (AUTHOR)<i> ignaz.eisele@emft.fraunhofer.de</i><br /><searchLink fieldCode="AR" term="%22Eisele%2C+Ignaz%22">Eisele, Ignaz</searchLink><relatesTo>1,2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Weber%2C+Johannes%22">Weber, Johannes</searchLink><relatesTo>1,3</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Schewski%2C+Alexandra%22">Schewski, Alexandra</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Music%2C+Emir%22">Music, Emir</searchLink><relatesTo>1,2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Maiwald%2C+Alwin%22">Maiwald, Alwin</searchLink><relatesTo>1,3</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Hahn%2C+Martin%22">Hahn, Martin</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Zahn%2C+Daniela%22">Zahn, Daniela</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Luo%2C+Zhen%22">Luo, Zhen</searchLink><relatesTo>3</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Nebrich%2C+Lars%22">Nebrich, Lars</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Schoof%2C+Benedikt%22">Schoof, Benedikt</searchLink><relatesTo>3</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Mayer%2C+Thomas%22">Mayer, Thomas</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Sturm-Rogon%2C+Leonhard%22">Sturm-Rogon, Leonhard</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Lerch%2C+Wilfried%22">Lerch, Wilfried</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Pereira%2C+Rui+Nuno%22">Pereira, Rui Nuno</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Kutter%2C+Christoph%22">Kutter, Christoph</searchLink><relatesTo>1,2</relatesTo> (AUTHOR)<i> christoph.kutter@emft.fraunhofer.de</i>
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  Data: <searchLink fieldCode="JN" term="%22Nanomaterials+%282079-4991%29%22">Nanomaterials (2079-4991)</searchLink>. May2026, Vol. 16 Issue 10, p569. 11p.
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  Data: <searchLink fieldCode="DE" term="%22Tunnel+junctions+%28Materials+science%29%22">Tunnel junctions (Materials science)</searchLink><br /><searchLink fieldCode="DE" term="%22Electric+measurements%22">Electric measurements</searchLink><br /><searchLink fieldCode="DE" term="%22Surface+defects%22">Surface defects</searchLink><br /><searchLink fieldCode="DE" term="%22Josephson+junctions%22">Josephson junctions</searchLink><br /><searchLink fieldCode="DE" term="%22Complementary+metal+oxide+semiconductors%22">Complementary metal oxide semiconductors</searchLink><br /><searchLink fieldCode="DE" term="%22Oxide+coating%22">Oxide coating</searchLink>
– Name: Abstract
  Label: Abstract
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  Data: Josephson junctions are key elements in superconducting qubits. Their efficient wafer-scale characterization is crucial for process control and optimization, motivating analysis approaches that extend beyond conventional cryogenic measurements. In this work, we demonstrate that room temperature (RT) capacitance and current–voltage measurements, combined with appropriate data analysis, enable extraction of relevant junction parameters such as oxide thickness, tunnel coefficient, and interfacial defect density. Furthermore, different charge transport mechanisms can be identified from detailed current–voltage analysis. We evaluate our characterization technique using tunnel junctions fabricated on 200 mm wafers in a complementary metal–oxide–semiconductor (CMOS)-compatible subtractive process. The results show a homogeneous average oxide thickness across the wafer with a variation below 3%. A dependence of the tunnel coefficient on oxide thickness indicates a stoichiometry gradient within the oxide. Additionally, low interfacial defect densities in the range of 70–5000 defects/cm2 are observed in our junctions, increasing with decreasing oxide thickness, suggesting that wet etching used for thickness control introduces interfacial trap states. Our study highlights the importance of advanced RT characterization for extracting tunnel junction parameters on the wafer scale, enabling effective process monitoring and optimization in industrial superconducting qubit manufacturing. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
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  Data: <i>Copyright of Nanomaterials (2079-4991) is the property of MDPI and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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        Value: 10.3390/nano16100569
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      – Code: eng
        Text: English
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      Pagination:
        PageCount: 11
        StartPage: 569
    Subjects:
      – SubjectFull: Tunnel junctions (Materials science)
        Type: general
      – SubjectFull: Electric measurements
        Type: general
      – SubjectFull: Surface defects
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      – SubjectFull: Josephson junctions
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      – SubjectFull: Complementary metal oxide semiconductors
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      – SubjectFull: Oxide coating
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      – TitleFull: Wafer-Scale Electrical Characterization of Al/Al x O y /Al Tunnel Junctions for Process Monitoring at Room Temperature.
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