Hydrogenated Amorphous Silicon Carbide: A Low-Loss Deposited Dielectric for Microwave to Submillimeter-Wave Superconducting Circuits

Low-loss deposited dielectrics will benefit superconducting devices such as integrated spectrometers, qubits, and kinetic inductance parametric amplifiers. Compared with planar structures, multilayer structures microstrips are more compact eliminate radiation loss at high frequencies. Multilayer most easily fabricated dielectrics, which typically exhibit higher dielectric than crystalline dielectrics. We measure the subkelvin low-power microwave millimeter-submillimeter-wave of hydrogenated amorphous silicon carbide ($a$-SiC:H), using chips Nb-Ti-$\mathrm{N}/a$-SiC:H/Nb-Ti-N microstrip resonators. deposit $a$-SiC:H by plasma-enhanced chemical vapor deposition a substrate temperature $400{\phantom{\rule{0.1em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$. The has millimeter-submillimeter tangent ranging from $0.9\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ 270 GHz to $1.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ 385 GHz. is $3.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$. These lowest tangents that have been reported for resonators films free blisters low stress: $\ensuremath{-}20$ MPa compressive 200-nm thickness 60 tensile 1000-nm thickness.