Fabrication of wide-IF 200–300GHz superconductor–insulator–superconductor mixers with suspended metal beam leads formed on silicon-on-insulator

Abstract

We report on a fabrication process that uses SOI substrates and micromachining techniques to form wide-IF SIS mixer devices that have suspended metal beam leads for rf grounding. The mixers are formed on thin 25μm membranes of Si, and are designed to operate in the 200–300GHz band. Potential applications are in tropospheric chemistry, where increased sensitivity detectors and wide-IF bandwidth receivers are desired. They will also be useful in astrophysics to monitor absorption lines for CO at 230GHz to study distant, highly redshifted galaxies by reducing scan times. Aside from a description of the fabrication process, electrical measurements of these Nb∕Al–AlNx∕Nb trilayer devices will also be presented. Since device quality is sensitive to thermal excursions, the new beam lead process appears to be compatible with conventional SIS device fabrication technology.