Date of Award

12-24-2025

Date Published

January 2026

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Physics

Advisor(s)

Ivan Pechenezhskiy

Keywords

Fabrication;Film Stress;Niobium;Quality Factor;Resonator;Superconducting

Subject Categories

Physical Sciences and Mathematics | Physics

Abstract

Superconducting qubits are a leading platform for scalable quantum computation. This platform offers high gate speeds and can make use of readily scalable complementary metal-oxide semiconductor (CMOS) fabrication techniques. However, superconducting qubits are susceptible to a variety of losses that arise in systems with superconductors, such as due to ubiquitous two-level systems, quasiparticles, and more. Designing fabrication processes to mitigate and manage these loss sources is critical to achieving scalable quantum computation. However, many of these loss sources are set during fabrication processing, of which there can be many different steps, each with its own parameter space. Exploring this space with qubits would be prohibitively time-consuming. Coplanar waveguide resonators provide a suitable proxy system for minimizing loss while costing less time and money to fabricate and measure. In this thesis, we explore the results of such an optimization performed on niobium resonators. Niobium is a widely used material platform for superconducting qubit circuits. We report highly consistent state-of-the-art resonator quality factors, with clear improvements over the previous fabrication recipe, and correlate the observed improvements to the internal quality factors with microstructural changes induced by hydrofluoric acid treatment, photoresist stripping, and choice of sputter deposition conditions. Additionally, we provide a detailed description of our fab process to ensure reproducibility in other lab facilities. Finally, we address some intriguing anomalies uncovered in temperature-dependent quality factors of the niobium resonators and show a correlation of the quality factors with compressive film stress.

Access

Open Access

Download

Included in

Physics Commons

Share

COinS