Design Of High Natural Frequency Acceleration Structure

MEMS is a kind of technology combining semiconductor technology and mechanicalengineering, which has developed rapidly in recent years and has a broad application prospectdue to its huge advantages. Silicon which has excellent electrical and mechanical propertiesbecomes one of the significant materials in the MEMS field. MEMS piezoresistiveacceleration sensors developed very early and fast due to the simplicity and maturity of theirprinciples, structures and fabrication processes. In order to improve the performances ofMEMS piezoresistive acceleration sensors, many researchers proposed various kinds ofsensitive structures. At present, although most of the general sensors use cantilever beamstructures due to their stabilization and maturity, the working mechanism and performanceoptimization of them tend toward perfection. In addition to the limitation of fabricationprocesses, it is very difficult to further improve the performance of general structures.In order to further improve the performance of MEMS piezoresistive acceleration sensors,an acceleration structure with a micro beam is designed. This new structure can maintain highsensitivity while possessing high natural frequency and strong overload capacity. In order toimprove the temperature characteristics, the compatibility with IC and sensitivity, polysiliconnanofilm is taken as strain resistance. Take full range acceleration of100g as an example, theoptimized designing method of sensor was given through finite element analysis. With anapplied voltage of5V, the sensor has the full range voltage of approximately150mV, and hasthe natural frequency of approximately37.5kHz. The overload capacity is250times higherthan the full range acceleration. Moreover, aiming at the deficiencies of this new structure, twoother improved structures were designed. The most reasonable structure is selected through thecontrastive analysis of these three structures’ geometrical parameters and performance.General fabrication processes and layout design of the most reasonable structure are given.