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Proceedings Paper

Micromachined room-temperature microbolometer for millimeter-wave detection and focal-plane imaging arrays
Author(s): Arifur Rahman; Erik K. Duerr; Gert de Lange; Qing Hu
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Paper Abstract

We have combined silicon micromachining technology with planar circuits to fabricated 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, is fabricated on a 1-micrometers thick Si3N4 membrane of square and cross geometries. The Nb film acts both as a radiation absorber and temperature sensor. Incident radiation is coupled into the microbolometer by a 0.37 (lambda) dipole antenna with a center frequency of 95 GHz and a 3-db bandwidth of 15%, which is impedance matched with the Nb film. The dipole antennas is placed inside a micromachined pyramidal cavity formed by anisotropically etched Si wafers. To increase the Gaussian beam coupling efficiency, a machined square or circular horn is placed in front of the micromachined section. Circular horns interface more easily with die-based manufacturing processes; therefore, we have developed simulation tools that allow us to model circular machined horns. We have fabricated both single element receivers and 3 X 3 focal-plane arrays using uncooled Nb microbolometers. An electrical NEP level of 8.3 X 10-11 W/(root)Hz has been achieved for a single- element receiver. This NEP level is better than that of the commercial room-temperature pyroelectric millimeter-wave detectors. The frequency response of the microbolometer has a ln(1/f) dependence with frequency, and the roll-off frequency is approximately 35 kHz.

Paper Details

Date Published: 27 June 1997
PDF: 12 pages
Proc. SPIE 3064, Passive Millimeter-Wave Imaging Technology, (27 June 1997); doi: 10.1117/12.277073
Show Author Affiliations
Arifur Rahman, Massachusetts Institute of Technology (United States)
Erik K. Duerr, Massachusetts Institute of Technology (United States)
Gert de Lange, Massachusetts Institute of Technology (United States)
Qing Hu, Massachusetts Institute of Technology (United States)

Published in SPIE Proceedings Vol. 3064:
Passive Millimeter-Wave Imaging Technology
Roger M. Smith, Editor(s)

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