Microscopic metallic air-bridge arrays for connecting quantum devices

TL;DR

This paper introduces a novel single-exposure fabrication method for creating large arrays of microscopic air-bridges with strong connections, enabling scalable quantum device architectures.

Contribution

It presents a new fabrication technique using tri-layer resist and electron-beam lithography for large, uniform air-bridge arrays in quantum devices.

Findings

Successfully fabricated 400 surface gates for quantum wires

Demonstrated strong metal-metal and metal-substrate connections

Addressed fabrication challenges with water-IPA developer and calibration

Abstract

We present a single-exposure fabrication technique for a very large array of microscopic air-bridges using a tri-layer resist process with electron-beam lithography. The technique is capable of forming air-bridges with strong metal-metal or metal-substrate connections. This was demonstrated by its application in an electron tunnelling device consisting of 400 identical surface gates for defining quantum wires, where the air-bridges are used as suspended connections for the surface gates. This technique enables us to create a large array of uniform one-dimensional channels that are open at both ends. In this article, we outline the details of the fabrication process, together with a study and the solution of the challenges present in the development of the technique, which includes the use of water-IPA (isopropyl alcohol) developer, calibration of resist thickness and numerical simulation of the development.