Development of TiN/AlN-based superconducting qubit components

TL;DR

This study reports on the fabrication and characterization of TiN/AlN-based superconducting qubit components, including Josephson junctions and resonators, advancing nitride material integration in quantum computing hardware.

Contribution

It introduces a complete fabrication process for TiN/AlN/TiN junctions and evaluates their material properties relevant to qubit performance.

Findings

Critical current of junctions ranges from 150 μA to 2 μA.

Material properties such as sputtering rates and critical temperatures were characterized.

Internal quality factors of TiN resonators were measured in the GHz regime.

Abstract

This paper presents the fabrication and characterization of superconducting qubit components from titanium nitride (TiN) and aluminum nitride (AlN) layers to create Josephson junctions and superconducting resonators in an all-nitride architecture. Our methodology comprises a complete process flow for the fabrication of TiN/AlN/TiN junctions, characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), ellipsometry and DC electrical measurements. We evaluated the sputtering rates of AlN under varied conditions, the critical temperatures of TiN thin films for different sputtering environments, and the internal quality factors of TiN resonators in the few-GHz regime, fabricated from these films. Overall, this offered insights into the material properties critical to qubit performance. Measurements of the dependence of the critical current of the TiN / AlN / TiN junctions yielded values ranging from 150 ${\mu}$A to 2 ${\mu}$A, for AlN barrier thicknesses up to ca. 5 nm, respectively. Our findings demonstrate advances in the fabrication of nitride-based superconducting qubit components, which may find applications in quantum computing technologies based on novel materials.