Micromachined room-temperature microbolometers for millimeter-wave detection

We have combined silicon micromachining technology with planar circuits to fabricate room-temperature niobium microbolometers for millimeter-wave detection. In this type of detector, a thin niobium film, with a dimension much smaller than the wavelength and fabricated on a 1 mu m thick Si3N4 membrane, acts both as a radiation absorber and temperature sensor. Incident radiation is coupled into the microbolometer by a 0.37 lambda dipole antenna of center frequency 95 GHz with a 3 dB bandwidth of 15%, which is impedance matched with the Nb film. An electrical noise equivalent power (NEP) of 4.5 X 10(-10) W/root Hz has been achieved. This is comparable to the best commercial room-temperature millimeter-wave detectors. (C) 1996 American Institute of Physics.