Fabrication of airbridges with gradient exposure

TL;DR

This paper introduces a gradient exposure fabrication technique for superconducting airbridges that simplifies production, enhances flexibility, and improves yield, benefiting large-scale quantum circuits.

Contribution

A novel gradient exposure method for fabricating superconducting airbridges that reduces complexity and increases scalability compared to existing techniques.

Findings

Produces lossless superconducting airbridges

Offers flexible size customization

Achieves high fabrication yield

Abstract

In superconducting quantum circuits, airbridges are critical for eliminating parasitic slotline modes of coplanar waveguide circuits and reducing crosstalks between direct current magnetic flux biases. Here, we present a technique for fabricating superconducting airbridges. With this technique, a single layer of photoresist is employed, and the gradient exposure process is used to define the profile of airbridges. In order to properly obtain the bridge profile, we design exposure dosage based on residual photoresist thickness and laser power calibrations. Compared with other airbridge fabrication techniques, the gradient exposure fabrication technique provides the ability to produce lossless superconducting airbridges with flexible size and, thus, is more suitable for large-scale superconducting quantum circuits. Furthermore, this method reduces the complexity of the fabrication process and provides a high fabrication yield.