Development of TiN Vacuum-Gap Capacitor Lumped-Element Kinetic Inductance Detectors

We report on the implementation of a vacuum parallel-plate capacitor manufactured using a straightforward process that allows to accurately set nanoscale vacuum gaps in order to reach fairly large capacitances with small footprints. Vacuum gaps between 150 and 300 nm have been achieved. To prevent native oxides and therefore two-level systems, both electrodes are made of TiN-based layers. We implemented the vacuum parallel-plate capacitors into lumped-element kinetic inductance detectors and compared their performances to standard interdigitated capacitor-based detectors. The vacuum capacitor detectors achieved higher quality factors (up to 1.1 × 106) and lower frequency noise (2.8 ± 0.5 Hz2/Hz at 10 Hz). Furthermore, we demonstrate that the noise generated within the meander of the lumped-element kinetic inductance detector can be as important as the one generated in the capacitance.