On-Wafer Vector-Network-Analyzer Measurements at mK Temperatures

We describe a system for performing on-wafer vector-network-analyzer measurements from 100 MHz to 15 GHz at mK temperatures (i.e., less than 20 mK). We first demonstrate a camera-less probe positioning system and calibrate this system at 4.4 K. We then use this positioning system to perform both on-wafer scattering-parameter calibrations and on-wafer large-signal-network-analysis calibrations at 4.4 K and mK temperatures. The scattering-parameter calibrations were based on cooled printed transmission lines while the power and electrical phase calibrations required for on-wafer large-signal network analysis calibrations were performed by transferring room temperature coaxial power and electrical phase calibrations through long attenuated coaxial lines to our cryogenic on-wafer reference plane. Finally, we perform scattering-parameter measurements of common interconnect structures and measurements of modulated-signals typical of those used to control superconducting transmon qubits commonly used in quantum-computing applications. We also demonstrate our ability to predistort the modulated signals we created, and we assess the drift and stability of our system, which we found to be on the order of a few tenths of a dB and a few degrees.