Free-standing silicon shadow masks for transmon qubit fabrication

TL;DR

This paper introduces a novel silicon shadow mask technique for superconducting qubit fabrication that reduces residues and helps control surface losses, achieving comparable qubit coherence to traditional methods.

Contribution

It presents a new resist-free nanofabrication method using silicon shadow masks, improving surface quality control in transmon qubit production.

Findings

Silicon shadow masks eliminate organic residues in fabrication.

Qubits made with these masks show coherence similar to standard methods.

The technique offers a pathway to better surface loss understanding.

Abstract

Nanofabrication techniques for superconducting qubits rely on resist-based masks patterned by electron-beam or optical lithography. We have developed an alternative nanofabrication technique based on free-standing silicon shadow masks fabricated from silicon-on-insulator wafers. These silicon shadow masks not only eliminate organic residues associated with resist-based lithography, but also provide a pathway to better understand and control surface-dielectric losses in superconducting qubits by decoupling mask fabrication from substrate preparation. We have successfully fabricated aluminum 3D transmon superconducting qubits with these shadow masks and found coherence quality factors comparable to those fabricated with standard techniques.