Fabricating low loss, lumped element niobium resonators

Over the past decade there has been a significant improvement in the quality of on-chip superconducting microwave components for various applications including quantum sensing and computation. However, scaling these sensitive quantum devices for potential applications like Stage-IV CMB experiments which require more than 500,000 superconducting TES bolometers for its proposed telescope or a high-efficiency microwave to millimeter-wave quantum transducer, will require these components to be made more compact while maintaining their high quality. Current on-chip microwave resonators with large interdigitated capacitors (IDCs) are incompatible with such future devices due to larger footprints and degraded performance with increasing capacitances. As opposed to some of the previous attempts to make compact high quality components from Al or TiN, our approach is to use niobium for our resonators. We have modelled our device using the planar 3D EM simulator SONNET, developed a fabrication procedure, fabricated initial prototype circuits, and evaluated device performance in a cryogenic environment. We will report our most recent results.