Qubit compatible superconducting interconnects

TL;DR

This paper introduces a fabrication process for superconducting interconnects compatible with quantum circuits, enabling 3D integration without lossy dielectrics, and demonstrates their robustness and superconducting properties.

Contribution

The authors develop a reliable fabrication method for superconducting interconnects that are compatible with qubit technology and demonstrate their mechanical and superconducting performance.

Findings

Superconducting transition temperature of 1.1 K

Average critical current of 26.8 mA

Mechanical robustness confirmed by shear and thermal tests

Abstract

We present a fabrication process for fully superconducting interconnects compatible with superconducting qubit technology. These interconnects allow for the 3D integration of quantum circuits without introducing lossy amorphous dielectrics. They are composed of indium bumps several microns tall separated from an aluminum base layer by titanium nitride which serves as a diffusion barrier. We measure the whole structure to be superconducting (transition temperature of 1.1$\,$K), limited by the aluminum. These interconnects have an average critical current of 26.8$\,$mA, and mechanical shear and thermal cycle testing indicate that these devices are mechanically robust. Our process provides a method that reliably yields superconducting interconnects suitable for use with superconducting qubits.