Fabrication of Planar-Integrated SIS Mixer Circuits with Improved Uniformity and Yield

Single-pixel prototype superconductor–insulator–superconductor (SIS) mixer integrated circuits (ICs) for multi-beam heterodyne receivers were fabricated. We introduced plasma-enhanced chemical vapor deposition (PE-CVD) for insulator layer deposition and machine-aligned via-hole etching for contact-hole definition on SIS junctions to achieve high uniformity and yield. In the PE-CVD, we applied a compressive/tensile/compressive SiO2 trilayer technique to control the film stress. The SiO2 trilayer stress was stable and negligibly low. The uniformity and junction quality yield of the single-pixel prototype SIS mixer ICs were improved in the process applying the PE-CVD and the via-hole etching.