THIN FILM CERAMIC GAS/TEMPERATURE MICRO-SENSORS

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THIN FILM CERAMIC GAS/TEMPERATURE MICRO-SENSORS

• Paul JooYoung Lee
• Joo.Y.Lee_at_colorado.edu
• Advisor Prof. Rishi Raj
• Department of Mechanical Engineering
• University of Colorado at Boulder
• Acknowledgement U.S. Department of Energy

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Project Outline

• Developing thin film ceramic gas-temperature
  sensor
• A ceramic micro-sensor to detect gas and
  temperature
• Fabrication of thin conducting SiCN
  micro-patterns on insulating substrates
• Establish electrical properties of the SiCN thin
  film sensor at high temperatures (1000 deg. C)

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Polymer Derived SiCN Conducting Ceramic

• Made from monomer liquid precursor, CerasetTM
  plus photo-initiator mixture
• Silicon CarboNitride amorphous ceramic
• Excellent oxidation resistance
• Electrically semi-conducting
• Resistance of the film changes with the
  surrounding temperature and gas environment

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Ceramic Micro-sensor?
Polymer Derived Ceramics (PDC) Technology
Conducting ceramic micro-sensors on
substrate (Batch processing capability leads to
cheap production)
Micro-electronics/ MEMS Fabrication
Technology Many identical chips on one
wafer/substrate

Conducting Ceramic - SiCN
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Fabrication
Microelectronics Technology
Spin-coat precursor onto substrate and pattern
using UV lithography
Photo-sensitive precursor and insulating,
refractory substrate
Array of polymer micro-patterns on the substrate
Heat treat the whole substrate (polymer ?ceramic)
Annealing heat treatment to conducting ceramic
Non-conducting ceramic patterns on the substrate
Many conducting ceramic devices on one substrate
Polymer Derived Ceramics
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Electrical Properties

• Ceramic
• ? refractory, oxidation resistant
• ? Working temperature 1000 deg. C

• Establish the relationship, conductivity vs
  temperature/gas type ? gas/temperature sensor

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Methodology

• Increase sensitivity ? Reduce resistivity of the
  thin film
• Doping with boron or other dopants
• Annealing condition changes
• Electrical property measurement
• Four point probe test resistivity measurement
  of thin films (Commercially available 300 deg.
  C max)
• Build Four point probe testing unit for high
  temperature environment

• Sealed testing unit can readily change the gas
  environment
• Measure the resistance response vs temperature
  and surrounding gas type