Ta Based Damascene Resonators
Transmon qubits have become a leading technology in quantum information science (QIS), with fabrication techniques widely accessible. Historically, devices were predominantly made from aluminum (Al) and niobium (Nb), but state-of-the-art transmons now use tantalum (Ta) achieving coherence times up to and exceeding 0.5 milliseconds [1-3]. The differentiation in performance between Ta and Nb-based devices is attributed to the surface oxidation states affecting Two-Level-System (TLS) noise. One approach to quickly evaluating material and device performance consists of fabricating only the readout resonator of a qubit and evaluating the quality factor which is the strategy employed in this project. Our research focuses on Ta coplanar waveguide (CPW) resonators fabricated using a damascene technique producing pristine metal structures within silicon substrates. This approach increases the dielectric substrate's participation ratio while keeping device edges oxide-free due to entrenchment. This collaborative effort, involving Pacific Northwest National Laboratory (PNNL), NY CREATES/SUNY Poly, and Brookhaven National Laboratory (BNL), has resulted in resonators with Q factors as high as 104 at low power. Ongoing studies aim to further understand and improve device performance by systematic analysis of oxygen trapped between device layers during processing. This research showcases the potential for significant improvements in superconducting qubit performance via the damascene process, heralding new possibilities for the advancement of scalable QIS technology.