MEMS: Fabrication of cryogenic bolometers
in: SPIE Proceedings (2012)
Cryogenic bolometers are among the most sensitive devices for the detection of electromagnetic radiation in the sub-millimeter range. Such radiation is of interest for astronomical observations as well as for security cameras. We describe how we fabricate an array of these bolometers Standard contact lithography is sufficient for these relatively coarse features. To increase the sensitivity, it is imperative to weaken the thermal link between the thermistors (the sensing devices) and the temperature bath. This is achieved by placing them on a silicon nitride membrane that is structured so that the thermistors are placed on a silicon nitride platform that is held only by a few beams. We obtain an array of MEMS devices. The fabrication process does not require sophisticated lithographic techniques, but rather great care to achieve the desired yield of 100 % intact bolometers in one array. We discuss bolometer basics and requirements for our applications, critical fabrication issues, and show results of complete systems built for a telescope and for security cameras.