Research On Key Technology Of Micro Hot Plate Semiconductor Sensor For Sarin Detection

The metal oxide gas-sensing semiconductor sensor performs qualitative and quantitative detection through the change of the conductivity of the sensitive material caused by the target,it has the characteristics of high sensitivity,fast response recovery,and easy miniaturization.Gas-sensitive semiconductor sensors are generally composed of two parts:sensitive materials and heating devices.The heating device provides the sensitive material with a stable working temperature to improve the reaction efficiency of the sensitive material.Micro-hotplates based on MEMS technology have the advantages of small size,low power consumption,and easy integration.They gradually replace traditional ceramic substrates and become a future development trend.However,the power consumption of the existing commercial micro-hotplates is relatively large,and it is difficult to meet the military application requirements of unmanned platform installation and distributed monitoring network with long battery life and low power consumption;And there are few studies on chemical warfare agents such as sarin,and there is no mature and reliable micro-hot plate semiconductor gas sensor product,which is difficult to meet the needs of CWAs detection.In order to study the factors affecting the performance of the micro-hot plate,reduce the power consumption of the micro-hot plate,and enable the self-developed micro-hot plate to be well combined with sensitive materials,this paper focuses on the key technologies of the micro-hot plate semiconductor sensor for sarin detection,the main research contents include:1.Model construction and simulation design of micro-hot plateThe research analyzes the theoretical models applicable to the micro-hot plate structure,including the heat loss model and the thin film thermal stress analysis model.Based on the theoretical model,a suspended structure micro-hot plate is designed.The support layer and isolation layer are made of silicon dioxide and silicon nitride composite structure,the shape of the heating electrode is a back type,and the test electrode is an interdigital structure.The 3D model of the micro-hot plate was constructed in SOLIDWORKS software,and the steady-state thermal simulation and thermal stress simulation of the micro-hot plate were carried out based on ANSYS Workbench finite element simulation software.By changing the parameter settings,the influence trend of key parameters such as the length,width,material composition,and film thickness of the cantilever beam on temperature and stress was studied,and the optimal parameter design was obtained.The power consumption of the micro-hot plate obtained by the final simulation optimization is 18.8m W,the temperature gradient is1.5%,and the thermal stress is 48MPa.The power consumption of the micro-hot plate is ideal,which provides key parameters and design layout for subsequent micro-hot plate tape-out preparation,It provides theoretical guidance from the level of simulation design,which lays a solid foundation for the development of micro-hot plate semiconductor sensors.2.Research on preparation technology of micro-hot plateBased on mature MEMS tape-out processes such as photolithography,chemical vapor deposition,reactive ion etching,etc.,a set of micro-hot plate fabrication process flow is designed.In order to verify the feasibility of the technological process,a tape-out experiment was carried out:The first tape-out used a wet etching process to form a suspended film.The tape-out results showed that the cantilever beam was broken and the edge was cracked,after analysis,silicon dioxide will also corrode at a lower rate in wet etching,causes the cantilever beam to break due to excessive stress;Using the back dry etching process to replace the wet etching process,the second tape-out was carried out,the results show that there is no abnormality in the structure of the cantilever beam,but it is found that the micro-hot plate has the phenomenon of black silicon,the reason for analysis is that it is caused by the uneven heat conduction at the bottom during etching;By adjusting the thickness of the bottom adhesive layer,the adhesive layer is changed from paraffin to silicone oil,and the third tape-out was carried out,the micro-hot plate was successfully prepared.Through three times of process tape-out optimization,the problems of cantilever fracture and black silicon were solved,and the micro-hot plate preparation process was determined.In order to study the performance of the micro-hot plate,a micro-hot plate performance test platform was built,and the self-developed micro-hot plate was characterized.The key performance parameters such as chip consistency,temperature resistance characteristics,power characteristics,thermal response time characteristics,and stability of the micro-hot plate were measured,and compared with the commercial micro-hot plate.The experimental results show that the structure and morphology of the self-developed micro-hot plate are complete,the electrode outline is clear and the error is only 0.246μm;And the resistance consistency is good,the temperature is stable during heating,it has good temperature resistance characteristics;When the working temperature is 400℃,the power consumption of the self-developed micro-hot plate is only 23m W,the thermal response time is 9.6ms,and the heating efficiency is 0.71mm²·℃/m W,and the overall performance is better.3.Preparation and Characterization of Micro-Hot Plate Semiconductor Sensor for Sarin DetectionIn order to verify the practicability of the self-developed micro-hot plate and prove that the micro-hot plate can be effectively combined with sensitive materials,the research on the preparation of the micro-hot plate semiconductor sensor was carried out,and the characteristic test of sarin was carried out.First,the sensitive material Au/In₂O₃/Zn O,which is sensitive to sarin,is optimized,and a high-precision mask for depositing sensitive materials is designed and fabricated,Au/In₂O₃/Zn O was deposited on the surface of the micro-hot plate heating platform by a magnetron sputtering process,and the combination of the micro-hot plate and the sensitive material was realized.The micro-hot plate is packaged with a ceramic tube and shell,and the micro-hot plate semiconductor sensor is integrated.A set of gas-sensing test platform for sarin detection is built,which mainly includes four parts:gas distribution system,heating system,data acquisition system and test software.Based on the gas-sensing test platform,the sarin sensing experiment was carried out,and the response curve was analyzed.The results show that the sensitivity of the self-developed micro-hot plate semiconductor sensor is1.5,the response time is 15s,the recovery time is 10s,The integrated sensor can realize sensitive detection of sarin,and it can also prove that the developed micro-hot plate has a stable structure and good heating performance,and the method of depositing sensitive materials by magnetron sputtering process is feasible and effective.This paper focuses on the research on the micro-hot plate semiconductor sensor,focusing on the key technologies such as the micro-hot plate structure simulation,the micro-hot plate preparation process,and the sensitive detection of sarin.The above research content lays the foundation for overcoming the detection of chemical warfare agents by micro-hot plate semiconductor sensors,and has potential application value in the development of sensitive detection of toxic chemical and chemical reconnaissance equipment,and has broad application prospects in the field of CWAs and toxic and harmful gas detection.