Fabrication of a superconducting hot-electron bolometer receiver with micromachined waveguide components

The use of superconducting hot-electron bolometers (HEBs) as mixing elements in terahertz heterodyne receivers has become increasingly attractive in the last few years. Such receivers find application in the fields of radio astronomy, molecular spectroscopy, and atmospheric remote sensing. We have developed a method of fabricating these devices, consisting of a niobium film less than one-quarter micron long and 150 Angstroms thick, using a gallium focused-ion beam (FIB). We intend to build a mixer which incorporates these devices, fabricated on membranes of silicon nitride, with terahertz waveguide components fabricated by laser-micromachining of silicon under CAD control. This paper discusses the three fabrication methods (focused-ion beam, the bulk micromachining of silicon necessary to obtain nitride membranes, and laser micromachining) used in our work.