THERMAL CHARACTERIZATION OF SURFACE-MICROMACHINED SILICON-NITRIDE MEMBRANES FOR THERMAL INFRARED DETECTORS

The aim of this work is to provide a thorough thermal characterization of membrane structures intended for thermal infrared detector arrays. The fabrication has been conducted at temperatures below 400 degrees C to allow future post processing onto existing CMOS readout circuitry . Our choices of membrane material and processing technique were plasm a enhanced chemical vapor deposited silicon nitride (SiN) and surface micromachining, respectively. The characterization gave for the therma l conductance (G) and thermal mass between the membrane and its surrou ndings 1.8 . 10(-7) W/K and 1.7 . 10(-9) J/K, respectively, which are close to the best reported values elsewhere. From these results the th ermal conductivity and specific heat of SiN were extracted as 4.5 +/- 0.7 W/m.K and 1500 +/- 230 J/kg.K. The contribution to G from differen t heat transfer mechanisms are estimated. A model describing the press ure dependence of G was developed and verified experimentally in the p ressure interval [5 . 10(-3), 1000] mbar. Finally, the influence of th e thermal properties of the membrane on infrared detector performance is discussed.