Preparation Of Material And Device Of Infrared Detector Used For Gas Sensing

In recent years，uncooled infrared gas detector based on MEMS technology has becomea research hotspot in the field of sensing. It has huge potential in monitoring the gas such ascombustible gas and toxic gas. It has the advantages of short response time, low cost, lowpower consumption and compatible with the CMOS technology. Gas sensors withsuspended micro-bridge structure makes the detector perform well in thermal insulation，andalso improves the device reliability.In this thesis, vanadium dioxide and titanium nitride serves as the thermal sensitivelayer and absorption structure layer of the detector, were researched and infrared detectorsbased on these materials were fabricated. The thesis mainly includes:（1） The VO₂film is deposited by reaction magnetron sputtering，the method offabrication which meets the need of uncooled infrared gas detector has been developed. TheVO₂thin film is tested by XRD and AFM. Then the reflection spectra of VO₂is obtained byFTIR and used for the calculation of dielectric constant.（2） The TiN is fabricated by reaction magnetron sputtering as well. The changingregularity of electrical properties and optical properties has been studied by changing the gasflow rate of N2.The reflection spectra has been fitted by a model dielectric function to obtainthe dielectric constants of TiN.（3） Three layer membrane stack comprised of TiN/VOx/TiN is simulated by thesoftware of TFCalc and the infrared absorption characteristics in infrared region. The film isfabricated in experiment and tested by FTIR，the result is consistent with the analysis ofsimulation.（4） The theory of VO₂and TiN is combined with the research of the gas detector. Andthe method of preparing porous silicon has been developed. The uncooled infrared gassensor is fabricated successfully by photolithography, dry etching, deposition and lift-offtechnologies. The surface morphology of the infrared gas detector is seen by using the SEM.