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THIN FILM CERAMIC GAS/TEMPERATURE MICRO-SENSORS. Paul JooYoung Lee Joo.Y.Lee@colorado.edu Advisor: Prof. Rishi Raj Department of Mechanical Engineering University of Colorado at Boulder Acknowledgement: U.S. Department of Energy. Project Outline.
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THIN FILM CERAMIC GAS/TEMPERATURE MICRO-SENSORS Paul JooYoung Lee Joo.Y.Lee@colorado.edu Advisor: Prof. Rishi Raj Department of Mechanical Engineering University of Colorado at Boulder Acknowledgement: U.S. Department of Energy
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)
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
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
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 Annealing heat treatment to conducting ceramic Heat treat the whole substrate (polymer ceramic) Many conducting ceramic devices on one substrate Non-conducting ceramic patterns on the substrate Polymer Derived Ceramics
Electrical Properties • Ceramic refractory, oxidation resistant Working temperature = 1000 deg. C • Establish the relationship, conductivity vs temperature/gas type gas/temperature sensor
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