Integration of Niobium Low-Temperature-Superconducting RF Circuits With Gold-Based RF MEMS Switches

A novel eight-mask fabrication process for the integration of low-temperature-superconducting niobium (Nb) RF circuits with gold-based RF microelectromechanical system (MEMS) switches is proposed. DC-contact and capacitive-contact RF MEMS switches integrated with Nb-based transmission lines are presented for the first time. A comparison of the RF performance of the switches at room and cryogenic temperatures indicate that the proposed gold-based MEMS fabrication process did have a major impact on the superconducting characteristics of Nb. A switched capacitor bank is also designed, implementing a dc-contact RF MEMS switch. The measured results of the capacitor bank show the variation of the capacitance value from 0.22 to 5.25 pF at 4 K. A thermal analysis of the devices under test (DUTs) is also performed, and an investigation is carried out to minimize the thermal loss between the chuck and the DUT.