Performance of Superconducting Resonators Suspended on SiN Membranes

TL;DR

This study demonstrates high-quality superconducting resonators suspended on thin SiN membranes with high aspect ratios, showing comparable performance to on-substrate resonators and expanding the potential applications of membrane-based device suspension.

Contribution

It provides the first detailed investigation of maximum membrane aspect ratios and device quality for superconducting resonators fully suspended on SiN membranes.

Findings

Resonators achieved internal quality factors of ~10^5 at single photon levels.

Membranes do not impair resonator thermalization.

High aspect ratio membranes are feasible for superconducting device suspension.

Abstract

Suspending devices on thin SiN membranes can limit their interaction with the bulk substrate and reduce parasitic capacitance to ground. While suspending devices on membranes is used in many fields including radiation detection using superconducting circuits, there has been less investigation into maximum membrane aspect ratios and achievable suspended device quality, metrics important to establish the applicable scope of the technique. Here, we investigate these metrics by fabricating superconducting coplanar waveguide resonators entirely atop thin ($\sim$110 nm) SiN membranes, where the membrane's shortest length to thickness yields an aspect ratio of approximately $7.4 \times 10^3$. We compare these membrane resonators to on-substrate resonators on the same chip, finding similar internal quality factors $\sim$$10^5$ at single photon levels. Furthermore, we confirm that these membranes do not adversely affect resonator thermalization and conduct further materials characterization. By achieving high quality superconducting circuit devices fully suspended on thin SiN membranes, our results help expand the technique's scope to potential uses including incorporating higher aspect ratio membranes for device suspension and creating larger footprint, high impedance, and high quality devices.