Noise Reduction Of SixGe1-x and SixGe1-xOy Bolometers by Forming Gas Passivation

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Noise Reduction Of SixGe1-x and SixGe1-xOy
Bolometers by Forming Gas Passivation
Mukti Rana and Donald Butler University of Texas
at Arlington Electrical Engineering
Dept. Arlington, TX 76019 Based in part by work
supported by the National Science
Foundation ECS-0322900
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Bolometer

• Bolometers are the optical sensors whose
  resistivity varies with temperature. When lights
  fall on the bolometer surface the sensing
  material of the bolometer absorbs heat and there
  by changes its resistance.

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Why Noise Reduction is important

• Noise detoriates the Bolometers performance by
  reducing the detectivity, responsivity.
• Amorphous films are characterized by higher noise.

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Bolometer Fabrication
Ashing of PI2737 in Oxygen Plasma
SiN
Ni Contact
NiCr Absorber
SiGeO
SiN
NiCr Arm
PI 2737 Sacrificial Layer
Ni Pad
Al Mirror
SiN Insulation Layer
p-Si Substrate
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Micormacined Bolometer SEM Picture
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Experimental Details of Forming Gas Passivation

• The Bolometers noise was measured in a shielded
  probe station with the help of SRC560 low noise
  preamplifier, HP 3562 dynamic signal analyzer and
  a computer. The noise spectra of same device was
  measured before and after the passivation to
  compare the noise.
• An AXIC Jet First Rapid Thermal Anneal (RTA) was
  used for annealing the sample. The sample was
  kept inside the chamber at a forming gas flow of
  500 SCCM for different intervals of time.

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Results Noise Voltage Power Spectral Density
(PSD) at 0.6uA Bias Current of SiGeO Bolometer
Before and After Forming Gas Passivation