| Infrared sensor is a kind of device that converts infrared radiation quantity into physical quantity.It is widely used in military and civil fields.The types of infrared sensors are mainly divided into photonic infrared sensors and thermal infrared sensors.Although the photonic infrared sensor has a high response frequency,the detection band is narrow and it needs refrigeration in normal operation.In complex application scenarios,the cost of refrigeration system is very high.Thermal infrared sensor can overcome this shortcoming.As an important kind of thermal infrared sensor,thermopile infrared sensor has the advantages of no refrigeration,small size,low production cost and become a research hotspot.However,thermopile sensors have some problems,such as smaller output performance and poor process compatibility compared with photonic sensors.How to improve the output performance and multi-scene working ability of thermopile sensor has become the main direction of current research and development of thermopile sensor.In this thesis,the development history and present situation of infrared technology and thermopile sensor are reviewed,and the main performance parameters of thermopile sensor are analyzed and discussed.By establishing the numerical relationship of each part of the sensor structure,the closed membrane structure of the traditional MEMS thermopile sensor is improved and optimized,that is,a multi-absorption zone structure（suspension layer absorption zone and thermocouple layer coplanar absorption zone）is designed on the basis of the original sensor structure.Then the heat balance model and optimization of the improved new structure were established,and the parameters of each part were analyzed numerically on Matlab.Then,the thermoelectric coupling simulation of the new structure is carried out based on the results of the numerical analysis.The multi-absorption thermopile sensor model is established through the design module of Ansys and the Thermal-Electric module.The variation of the output performance is obtained through simulation and analysis,and the influence of the parameters of the numerical analysis is compared to optimize the structural size parameters.Verify the correctness of the model.The temperature distribution and potential distribution of the thermopile sensor in the multi-absorption zone are analyzed.The results show that the temperature in the absorption zone of the suspension layer increases gradually from the arc contact part.The heat in the absorption zone of the thermocouple layer diffuses from the center to all sides and gradually decreases from the hot junction of the thermocouple connection to the cold junction.The potential of the sensor increases gradually from the electrode derived from the N-type polysilicon thermocouple to the electrode derived from the P-type polysilicon thermocouple.Then the optical characteristics of the absorption region are analyzed and the infrared absorption efficiency of the silicon oxynitride antireflection film is simulated and analyzed by using the finite difference time domain method.The results show that the maximum absorption rate of the absorption zone in the 8-14μm band is increased by about 12%after the addition of 0.6μm thick SiON2 anti-reflection film,and the thermal junction temperature of the thermo sensor with SiON2 anti-reflection absorption zone structure is increased by 0.23℃,and the temperature utilization rate is increased by about 35%.The output electromotive force is about 11.8m V,which is about 3.1m V higher than the original sensor,and the voltage output rate is 35%higher.Then,based on the process and technology involved in the production of multi-absorption zone MEMS thermoelectric reactor sensor,the overall process flow of the device is designed and optimized to form a complete production flow plan of the new structure.And the lithographic layout required by the flow plate is drawn,and the alignment mark is designed to correct the layout rendering,so as to improve the accuracy of the engraving.The multi-absorption zone MEMS thermopile sensor structure proposed in this thesis is an innovation and design of the traditional single-layer closed membrane structure.Combined with the principle of anti-reflection,it has the characteristics of higher output performance and CMOS compatibility,which provides an idea and method for MEMS thermopile sensors to be used in more scenarios in the future.The established antireflective film provides more selectivity and reference for the design of the absorption region structure of thermopile sensor. |
