Fabrication process optimization for high-quality niobium coplanar waveguide resonators

We present a variety of treatments for optimizing the quality factors of coplanar waveguide resonators made of niobium films on Si 100 substrates. We explore adding aluminum capping layers and aluminum seed layers underneath the niobium, seeking to promote self-limiting oxide formation and better lattice matching at the metal-substrate boundary. We also explore additional film treatments to improve the resonator quality factors, including different etching, descumming, and resist stripping methods.