High-Q trenched aluminum coplanar resonators with an ultrasonic edge microcutting for superconducting quantum devices

TL;DR

This paper presents high-Q superconducting aluminum coplanar waveguide resonators with ultrasonic edge microcutting, demonstrating improved dielectric performance for quantum devices, and investigates fabrication techniques affecting quality factors.

Contribution

It introduces a novel ultrasonic edge microcutting process that enhances the quality factors of aluminum CPW resonators used in superconducting quantum circuits.

Findings

Achieved internal quality factors exceeding 5x10^6 at high power

Best low-power quality factor of 4.4x10^6 with wet etched aluminum

Ultrasonic microcutting improves dielectric loss performance

Abstract

Dielectric losses are one of the key factors limiting the coherence of superconducting qubits. The impact of materials and fabrication steps on dielectric losses can be evaluated using coplanar waveguide (CPW) microwave resonators. Here, we report on superconducting CPW microwave resonators with internal quality factors systematically exceeding 5x106 at high powers and 2x106 (with the best value of 4.4x106) at low power. Such performance is demonstrated for 100-nm-thick aluminum resonators with 7-10.5 um center trace on high-resistivity silicon substrates commonly used in quantum Josephson junction circuits. We investigate internal quality factors of the resonators with both dry and wet aluminum etching, as well as deep and isotropic reactive ion etching of silicon substrate. Josephson junction compatible CPW resonators fabrication process with both airbridges and silicon substrate etching is proposed. Finally, we demonstrate the effect of airbridges positions and extra process steps on the overall dielectric losses. The best quality fa ctors are obtained for the wet etched aluminum resonators and isotropically removed substrate with the proposed ultrasonic metal edge microcutting.