A novel micro-fabrication process for integration of Superconductor niobium-based RF circuits with gold-based RF MEMS devices

摘要

A novel 8-mask fabrication process for the integration of Low Temperature Superconducting (LTS) niobium (Nb) RF circuits with gold-based RF MEMS switches is proposed. A fixed and a tunable 3-pole bandpass filter (BPF) are fabricated implementing the new Nb-based fabrication process. The tunable BPF includes nine dc-contact RF MEMS switches. The center frequency of the tunable BPF shifts from 10 GHz to 9 GHz when the three switches that change the length of the resonators are in the ‘on’ state and the other six are in the ‘off’ state. The first version of the tunable BPF is all gold-based, which is measured at room temperature. The insertion loss of the all gold-based tunable BPF is close to 5.5 dB. The switches actuation voltage is around 32 V at room temperature. The fixed version of the BPF is fabricated using Nb as the lossless metal layer. Measurement of the fixed Nb-based BPF shows 4.4 dB improvement in the insertion loss at 4 K. The tunable version of the superconducting BPF is also fabricated and measured at 4 K. There is 1 GHz shift in the center frequency of the filter when the three RF MEMS switches are actuated. The actuation voltage of the gold-based RF MEMS switches at 4 K is about 48 V.