Photolithography-Only Fabrication of Transmons Using Double-Oblique Evaporation

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 104 nm2, 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 20mK, where we observe basic transmon qubit operation with f01=4.865 GHz, T1∼9μs, and T∗2∼0.4μs. These results demonstrate the feasibility of realizing functional transmon devices in a photolithography-only process using double-oblique evaporation.