Research And Development Of MEMS Gas Sensor And Micro-manufacturing Platform

Metal oxide semiconductor gas sensor,with simple structure,small size,low power consumption,low price and other characteristics,is widely used in food safety,medical detection,air quality monitoring and other fields.Based on Micro-Electro-MechanicalSystems(MEMS)technology,micro-hot-plate devices can be manufactured by such processes as lithography,sputtering,etching and micro-jet film forming,so as to achieve sub-millimeter scale device integration and significantly reduce device power consumption and cost,which will also be the general trend of sensor development.At present,the sensor micromanufacturing platform based on MEMS technology mainly uses silicon chip as the chip base and is compatible with film forming processes such as sputtering.However,the high-performance gas-sensitive film is mainly composed of porous thick film and slurry micro-spraying as the film forming process.The matching of temperature field and stress field among porous gassensitive film,electrode and substrate will affect the stability and power consumption of the device.Oxide ceramics,metal electrodes,and metal oxide gas-sensitive membranes have inherent advantages in matching parameters such as expansion coefficient and thermal conductivity.This paper develops a set of ceramic MEMS gas sensor manufacturing platform,including ultraviolet lithography,laser etching,micro-jet film formation,auxiliary packaging and other functions,with the characteristics of process coherence,high precision,modularity and so on.UV lithography is realized by the contact exposure between mask plate and substrate,and the high-precision automatic alignment between mask plate and substrate is realized based on the multi-freedom mobile platform.The 355 nm ultraviolet laser and the highprecision vibrating mirror system are used to realize the etching of the substrate with the inner width of 20?m.A glass nozzle with ultra-fine aperture and electrostatic micro-spraying method are used to realize fixed-point micro-spraying of gas-sensitive film.The film forming diameter can be less than 100?m.Secondly,in order to improve the processing accuracy of the gas sensor micromanufacturing platform,the lithography process and laser etching process parameters of the platform are optimized respectively.By optimizing the pattern line width and exposure time parameters,a complete pattern with a line width of 20.16?m is obtained.By adjusting the distance of the laser galvanometer light,the laser line width of the laser is at a minimum of 21.9?m,corresponding to the maximum power density.Next,through the magnetron sputtering coating and micro-spray film formation experiments,the UV lithography and micro-spray film formation processes are evaluated.The results show that the uniformity deviation of the line width of the metal electrode is 0.045 and the uniformity deviation of the electrode resistance is 0.036 by the photolithography process and magnetron sputtering,which meets the expected requirement that the uniformity deviation is less than 0.05;The average deviation of the film diameter consistency of the material is 0.034,which meets the expected requirements.Finally,this paper designs,optimizes and manufactures a gas sensor device,which consists of a hole protection mesh housing,a gas sensitive array chip,a ceramic pad and a semiconductor shell.In the design process,three electrode distribution schemes are designed for the micro-hot plate structure in gas-sensitive array chip,which are coplanar,heteroplanar and laminated.In order to solve the heat dissipation problem of gas-sensitive array chip,two kinds of high-mounted ceramic chips with different structures are designed.Considering the operating environment and mechanical strength of the gas sensor device,a porous protective net is designed to ensure the device can work stably.In the process of optimization,the temperature field of gas-sensitive array chip under different conditions is simulated by using the finite element analysis software ANSYS.In the manufacturing process,the gas sensor array chip is prepared by photolithography,magnetron sputtering,laser etching and micro-jet film,and the chip is packaged in the semiconductor tube shell by binding the glue and the gold wire.