High-responsivity vacuumless microbolometer arrays microfabricated on thermally isolated suspended membranes

This paper reports a low-cost vacuum-less wavelength-selective mid-infrared (3-5 mu m) micro bolometer array for atmospheric gas detection fabricated on top of a thin SiN membrane. Each microbolometer consists of a SiN platform with a polysilicon thermistor and a stacked frequency-selective Fabry-Perot cavity/Salisbury absorber suspended above a Pt reflector. The bolometer structures are fabricated on top of a thin, thermally insulated SiN membrane formed by back-etching the underlying substrate. When operated under atmospheric conditions, the thermal isolation of the supporting membrane results in a 10-fold enhancement in average device responsivity (similar to 40000 V/W) compared to that of devices supported on solid substrates (similar to 4500 V/W).