1. 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

2. 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)

3. Polymer Derived SiCN Conducting Ceramic Made from monomer liquid precursor, Ceraset TM 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

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

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

6. Electrical Properties Ceramic  refractory, oxidation resistant  Working temperature = 1000 deg. C Establish the relationship, conductivity vs temperature/gas type  gas/temperature sensor

7. 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