# Overlap junctions for high coherence superconducting qubits

## TL;DR

This paper presents a new fabrication method for high-coherence superconducting qubits using overlap junctions formed with standard processes, eliminating shadow masks and enabling CMOS-compatible manufacturing.

## Contribution

It introduces an overlap junction fabrication technique with in situ Ar milling that maintains high coherence and simplifies the process for scalable quantum device production.

## Key findings

- High coherence achieved with overlap junctions on aluminum surfaces.
- Elimination of angle-dependent shadow masks in junction fabrication.
- Compatibility with conventional CMOS processing methods.

## Abstract

Fabrication of sub-micron Josephson junctions is demonstrated using standard processing techniques for high-coherence, superconducting qubits. These junctions are made in two separate lithography steps with normal-angle evaporation. Most significantly, this work demonstrates that it is possible to achieve high coherence with junctions formed on aluminum surfaces cleaned in situ with Ar milling before the junction oxidation. This method eliminates the angle-dependent shadow masks typically used for small junctions. Therefore, this is conducive to the implementation of typical methods for improving margins and yield using conventional CMOS processing. The current method uses electron-beam lithography and an additive process to define the top and bottom electrodes. Extension of this work to optical lithography and subtractive processes is discussed.