The Test And Analysis Of Silicon MHP And SnO₂Thin Film

The metal oxide semiconductor gas sensor has attained widespread attention and research since its appearance. Generally, its working temperature is high to200-450degC aiming at getting high sensitivity, so it is consists of the heater and the sensitive materials. Metal oxide gas sensor has been widely used in industrial inspection, environmental protection etc.In recent years, microhotplate becomes the first choice of the gas sensor’s heater for its low power consumption, fast thermal response, easy integrated etc. Firstly, this paper simulate the power consumption, temperature gradient, temperature response, thermal expansion, and thermal stress of the microhotplate, which was design and manufactured by our research group. And the power consumption, temperature response, and atmosphere pressure influence on the heating resistance of the microhotplate were experimental tested. Secondly, we prepared SnC>2thin film by RF magnetron sputtering, and the thickness of the film is150nm,250nm, and350nm respectively. Then we use X-ray diffraction(XRD) and scanning electron microscopy(SEM) to measure the surface morphologies of the SnO2thin film with different thickness, and use energy dispersive spectrometer(EDS) to analysis the element consists of the film. Finally, the static gas distribution method was used to test the response of the gas sensors, which were sputtered different thickness SnO2thin film, to benzene, methanol, ethanol, and acetone. The response time, recovery time, optimum operating temperature, the relationship between the sensitivity and the gas concentration, and the SnO2thin film thickness influence were concerned.The simulation result indicates that, the microhotplate heated to300degC requires only26mW, thermal response time less than7ms, which is verified by experiment test; moreover the temperature distribution gradient and the deformation is small. The SEM pictures show that the surface of the thin film is smooth and intensity. And the gas sensing properties test indicates that the response time increases with the film thickness, but the recovery time shows no significant law, and the sensor with250nm SnO2thin film has maximum sensitivity, lower optimum operating temperature, and a good sensitivity to gas concentration.