Characterizing superconducting airbridges fabricated using a grayscale electron-beam lithography process

In developing large-scale superconducting quantum processors, micron-size superconducting airbridges play a crucial role. Here, we report on the development of a grayscale lithography process using electron beam lithography, which is capable of fabricating aluminum airbridges with sizes ranging from 1 to 30 µm in length [1]. We characterized these structures through imaging and electrical measurements at millikelvin temperatures. Specifically, we benchmark the process by measuring the quality factor of quarter-wave coplanar waveguide resonators, incorporating airbridges at the shorted end. The broad range of accessible airbridge dimensions offers flexibility in connecting different elements on the chip in a single lithographic step. This approach is fully compatible with different material systems and could help to reduce the number of processing steps involved in device fabrication.

Reference:

[1] Janzen, N. et al. Applied Physics Letters 121.9 (2022)