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arXiv · 2605.19590

Photolithography-Only Fabrication of Transmons Using Double-Oblique Evaporation

K. Aoyanagi·S. Abe·S. Chen·T. Inada·C. Kawai·Y. Mino·K. Nakamura·K. Nakazono·T. Nitta·K. Watanabe
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Abstract

We investigate a photolithography-only fabrication process for transmon Josephson junctions using a modified double-oblique evaporation geometry. Using a bilayer resist process and Al shadow evaporation, we fabricate junction structures and confirm by optical and scanning electron microscopy that the resulting narrowed crossing region reaches a geometrical area on the order of $10^4~\mathrm{nm}^2$, which lies in the size range relevant to qubit junction fabrication. Room-temperature resistance screening shows that the junction resistance falls within the target range for the present transmon design over a usable process window and exhibits a clear design dependence. We further implement fabricated junctions in transmon devices and evaluate them in a three-dimensional Al cavity at $20 \, \mathrm{mK}$, where we observe basic transmon qubit operation with $f_{01}$=4.865 GHz, $T_1 \sim 9 \, \mu \mathrm{s}$, and $T_2^* \sim 0.4 \, \mu \mathrm{s}$. These results demonstrate the feasibility of realizing functional transmon devices in a photolithography-only process using double-oblique evaporation.

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K. Aoyanagi, S. Abe, S. Chen, T. Inada, C. Kawai, Y. Mino, K. Nakamura, K. Nakazono, T. Nitta, K. Watanabe. 2026-05-19. Photolithography-Only Fabrication of Transmons Using Double-Oblique Evaporation. https://arxiv.org/abs/2605.19590

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