Low-Loss, High-Coherence Airbridge Interconnects Fabricated by Single-Step Lithography

  1. Jibang Fu,
  2. Bo Ren,
  3. Jiandong Ouyang,
  4. Cong Li,
  5. Kechengqi Zhu,
  6. Yonggang Che,
  7. Xiang Fu,
  8. Shichuan Xue,
  9. Zhaohua Yang,
  10. Mingtang Deng,
  11. and Junjie Wu
Airbridges are essential for creating high-performance, low-parasitic interconnects in integrated circuits and quantum devices. Conventional multi-step fabrication methods hinder miniaturization and introduce process-related defects. We report a simplified process for fabricating nanoscale airbridges using only a single electron-beam lithography step. By optimizing a multilayer resist stack with a triple-exposure-dose scheme and a thermal reflow step, we achieve smooth, suspended metallic bridges with sub-200-nm features that exhibit robust mechanical stability. Fabricated within a gradiometric SQUID design for superconducting transmon qubits, these airbridges introduce no measurable additional loss in the relaxation time T1, while enabling a 2.5-fold enhancement of the dephasing time T∗2. This efficient method offers a practical route toward integrating high-performance three-dimensional interconnects in advanced quantum and nano-electronic devices.
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