Research On Fabrication Process Of Ring Universal MEMS Inertial Switch

With the continuous development of micro electro mechanical system technology,MEMS sensors,MEMS actuators and other MEMS devices have been applied in some industrial fields.As a kind of inertial impact detection sensor composed of spring and mass,MEMS inertial switch has a good application prospect in aviation,aerospace and transportation industry because of its advantages such as small size,low cost and low energy consumption.Therefore,the manufacturing process of MEMS inertial switch is receiving more and more attention.In recent years,UV-LIGA technology has been applied in the manufacture process of MEMS inertial switch because of its low cost and short process cycle.According to the design requirements,a new type of ring universal MEMS inertial switch structure and related dimensions were determined,and the processing route was developed according to the characteristics of the switch.A high aspect ratio MEMS inertial switch was made on the metal substrate based on UV-LIGA technology.The effects of different photolithographic parameters on the morphology and dimension of high aspect ratio SU-8molds were studied by UV lithography.The parameters of photolithography were optimized.he effect of ultrasonic aging technique on reducing the stress in the high aspect ratio SU-8film was studied.In view of the problems of poor quality caused by the serious “lateral erosion” of SU-8in the process of making high aspect ratio and fine-line micro electroforming molds,SU-8UV lithography was studied.The effects of different exposure dose and PEB time on SU-8UV lithography were studied experimentally.The results show that with the increase of the exposure dose,the phenomenon of "lateral erosion" of SU-8 film is obviously improved,but after the exposure dose increases to a certain extent,the fine line SU-8 channel will turn black;with the post-bake time extension,the phenomenon of "lateral erosion" will be improved.Finally,on the basis of the above experimental results,the process parameters of SU-8 UV lithography are optimized,and a high-quality micro-electroforming photoresist mold was developed.In order to solve the problem of cracking,deformation and shedding caused by the internal stress result from the UV lithography process of high aspect ratio SU-8 mold,the ultrasonic aging technology was applied to the fabrication process of silo-type SU-8 film,and the effect of ultrasonic aging technology on reducing internal stresst of SU-8 mold was studied experimentally.The experimental results show that the internal stress has beenreduced,and the SU-8 mold was less likely to fall off the substrate.The retention rate of the SU-8 microstructure was 34.4% higher than that of the non-treatment.Based on the above results,a high aspect ratio SU-8 mold with low internal stress was successfully fabricated.Based on the above experimental results,a high aspect ratio passive MEMS inertial switch was fabricated on the metal substrate by 5 times SU-8 lithography and 5 times micro electroforming by UV-LIGA technology.The external dimensions of the switch are:3935×3935×234 ?m,of which the smallest line width is 12?m,the highest aspect ratio of the single layer is 10:1,and the highest aspect ratio of the multi-layer is 20:1.The error of line width of important structure is analyzed by statistical analysis method,and the error of line width is reduced from 5.5?m to 1.0?m by using error compensation method.