The Study On Thermoelectric Effect Of High-temperature Microheater

Microheaters are a key component for catalytic combustion type,metal oxide semiconductor and even infrared gas sensors.Due to low heating temperature,the research are focused on the uniformity of temperature distribution and power optimization of microheaters,which used in catalytic combustion type,metal oxide semiconductor and infrared gas sensors.As high-temperature silicon microheaters for methane gas detection sensors based on MEMS achieves breakthrough,thermoelectric effect will have a significant effect on the characteristics of micro-scale high-temperature silicon microheaters.In this paper,the thermoelectric effect of high temperature microheaters was studied by finite element simulation and experiment,in order to fully master the characteristics of high-temperature silicon microheaters,and then use the characteristics of high-temperature microheaters to obtain gas sensing information more effectively,explore the formation of a new type of methane sensing method.Firstly,the heat transfer process was analyzed and a simplified heat transfer equation was given.For different types of silicon microheaters,Joule thermal simulation was carried out and the heat transfer rules of the microheaters during the Joule thermal analysis process was initially mastered.Secondly,for the N-type and P-type doped monocrystalline silicon bridge microheaters and the U-shaped microheaters,thermal-electric coupling analysis was performed considering the thermoelectric effect.The role of thermoelectric effect in high-temperature microheaters was studied.The results show that the thermoelectric effect in high-temperature microheaters causes a significant shift in the temperature distribution,especially under sinusoidal AC excitation,the temperature distribution shift on microheaters oscillates with the same frequency of excitation.It indicates that high-temperature microheaters driven by AC excitation can contain richer thermal information.Based on the above result,two new sensing structures were designed and analyzed,the results show that both of the designed sensing structures can convert the temperature offset into a measurable voltage signal,which caused by the thermoelectric effect in a high-temperature silicon microheater.In the end,Raman spectroscopy was used to test and analyze the temperature distribution under different currents in a single microheater.At the same time,the new sensing structure was tested under different current.The results show that the temperature distribution of high-temperature silicon microheaters shifts in different degrees under different excitations,and the new sensing structure can effectively convert the temperature offset into electricity output.The experimental results of the new sensing structure are in good agreement with the simulation results.The results of simulation and experiment show that the thermoelectric effect in the micro-heater can produce more abundant thermal information,and the sensor structure designed in this paper can effectively convert the thermal information into electrical signals.Therefore,it is expected to be used for MEMS gas sensors for methane gas detection.