NASA BroadBand Detectors

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NASA Broad-Band Detectors

• Clouds and the Earths Radiant Energy System
  (CERES) Program
• Staring large area detectors (1.5 mm x 1.5 mm and
  0.4 mm x 0.4 mm) in 1 x 4 or 1 x 5 arrays
• Noise Equivalent Power (NEP) Vn/Rv lt 5 x10-10 W
  Thermal time constant tth lt 7 msec
• Flat spectral response over 0.3 mm to greater
  than 100 mm

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Microbolometer Layout
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Schematic of Design
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Modeling Results
Optical modeling of the pixel geometry has been
performed. Utilization of a two-mirror
microbolometer significantly improves the
uniformity of the optical absorption. The model
will be refined to fine tune the thickness of the
detector layers. A three-mirror geometry will be
explored.
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• An SEM micrograph of a YBaCuO microbolometer
  prototype. The pixel size is 0.4 mm x 0.4 mm.
  Holes are used to allow for the removal of the
  polyimide sacrificial layer. The pixel uses a
  dual-mirror design. The maximum cavity height is
  approximately 16 mm.

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Summary and Comments

• Y-Ba-Cu-O can be deposited easily by rf
  sputtering at ambient temperature. Processing is
  post-CMOS and micromachining compatible.
• Y-Ba-Cu-O has a relatively high TCR (3.5/K) and
  low 1/f-noise, attractive as a bolometer.
• Multi-mirror and absorber design can enhance
  spectral bandwidth of uncooled IR microbolometers.