Three-dimensionally combined carbonized polymer sensor and heater

This paper presents for the first time fabrication process of a three-dimensionally combined carbonized NO2 sensor and the microresistive heater for the future integration of the nitrogen dioxide gas detection system. The carbonized photo-resist as an absorbent of nitrogen dioxide sensor and the three-dimensional bridge-type of SU8 resistive heater are fabricated by using sequential patterning and the carbonization process of the photo-resists. The maximum temperature of the carbonized process for both sensor and heater structure are properly optimized through the optical microscope, SEM, FE-SEM observation of the carbonized structures and the responses of the gas sensor to a 5 ppm of NO2 gas. As the maximum temperature of the carbonization process for the positive photo-resist sensor increases, the structural shrinkage increases and the electrical resistance decreases. The carbon sensor processed at 700 °C shows the most stable electrical response and has the higher sensitivity to a 5 ppm of NO2 gas. By increasing the sensing area of the gas sensor, the sensitivity of the photo-resist sensor also increases. The bridge-type SU8 heater structure can be fabricated successfully without any structural failure when the maximum temperature of the carbonization process is 650 °C.