Integrated microoxygen sensor based on nanostructured TiO2 thin films

An integrated microoxygen sensor based on the nanostructured TiO₂ thin film is presented. A pair of interdigitated electrodes was designed with the microheater around them on the same layer, which was aimed at simplifying the structure and avoiding fracture of the embedded heater. To fabricate the sensor chips, an optimisation process consisting of 14 steps was designed. The adiabatic cavity was formed by releasing the Si substrate from backside to a certain thickness at first, then a TiO₂ film was prepared by the sol-gel process and patterned by the wet etching process, after that electrodes and the heater were patterned and finally the remaining silicon was thinned further. Response properties to different gases were tested, and the sensor shows a good sensitivity of 0.093 and high selectivity of 0.258 to O₂ than H₂, response time of 51 s and hysteresis of 2.93%. The integrated microoxygen sensor has potential applications on the occasions of miniaturised, integrated, low power and mass production.