Exploring Materials for RF Transmission Lines in Cryogenic Systems

Superconducting systems operating in cryogenic environments represent a rapidly evolving domain with diverse applications spanning from quantum computing to medical diagnostics. To optimize and enhance the performance of such systems, a comprehensive understanding of material properties and their responses under cryogenic conditions is imperative. This work investigates the RF and DC electrical performance of passive structures, specifically transmission lines, at both room and cryogenic temperatures. S-parameter measurements were conducted on Coplanar Waveguides (CPWs) transmission lines, which are crucial for interaction with qubit chips and the resonators to read out the qubit states. Additionally, DC electrical testing is performed on the CPWs to analyse the resistance across the signal and ground metal lines. A series of test structures using different substrates and metal lines are fabricated for s-parameter testing at both room and cryogenic temperatures. This paper presents the impact of the superconducting environment on material RF loss and resistance.