Reducing intrinsic loss in superconducting resonators by surface treatment and deep etching of silicon substrates

TL;DR

This paper demonstrates methods to enhance superconducting resonator quality factors by surface treatment and deep etching of silicon substrates, reducing two-level system losses and achieving over 1 million internal quality factor in the quantum regime.

Contribution

It introduces combined surface treatment and deep etching techniques to minimize losses in superconducting resonators, improving their performance in quantum applications.

Findings

Achieved internal quality factors above 1 million.

Surface treatment and deep etching reduce two-level system losses.

Further interface optimization could enhance performance.

Abstract

We present microwave-frequency NbTiN resonators on silicon, systematically achieving internal quality factors above 1 M in the quantum regime. We use two techniques to reduce losses associated with two-level systems: an additional substrate surface treatment prior to NbTiN deposition to optimize the metal-substrate interface, and deep reactive-ion etching of the substrate to displace the substrate-vacuum interfaces away from high electric fields. The temperature and power dependence of resonator behavior indicate that two-level systems still contribute significantly to energy dissipation, suggesting that more interface optimization could further improve performance.