Micromachined millimeter-wave SIS-mixers

Micromachined SIS-mixers for 90-115 GHz and for 180-230 GHz have been fabricated and tested. A micromachined SIS-mixer consists of an antenna-coupled superconducting tunnel junction fabricated on a thin SiN membrane which is placed inside a pyramidal horn structure. The horn is formed by anisotropic KOH-etching of [100] Si along the (111) crystal planes. The high accuracy of the etching and the ease of whole-wafer fabrication make this type of SIS mixers attractive for applications both at high frequencies and in imaging arrays. Experimental results show that high-quality tunnel junctions can be reliably fabricated on thin SiN membranes. Experiments also show that the junctions are adequately cooled on the membrane and that sufficient LO-power can be coupled.<>