| The high-g triaxial acceleration sensor is applied to electromagnetic railguns,cruise missiles and other weapons,and plays a vital role in the fuze control system of projectile penetrating hard targets.With the development of intrusive weapons,the demand for high-g acceleration sensors is gradually increasing,so it is necessary to carry out research on high-g acceleration sensors.The trajectory of the projectile in the hard target penetration munitions fuze is in three-dimensional space during the actual motion and has an acceleration peak of 100,000g or more.The piezoresistive high-g triaxial acceleration sensor faces the problems of insufficient measurement capability and low measurement accuracy.To solve the above problems and to ensure the reliability of sensor operation in extreme harsh environments such as real high shock,high temperature and strong magnetic field,this thesis proposes a high-g triaxial acceleration sensor with on-chip temperature compensation.Considering the factors such as structural miniaturization,anti-overload ability and lateral effect,a monolithic triaxial accelerometer is designed,containing three sensitive units,of which the horizontal sensitive unit is designed with a self-supporting beam structure and the vertical unit is miniaturized based on the existing the beam-island structure.Taking the piezoresistive accelerometer as the object of study,the working principle of the sensor was analyzed by utilizing the piezoresistive effect of monocrystalline silicon and establishing a second-order system mechanical model.The relationship between the stress of the structure and the size of the cantilever beam was analyzed by establishing mathematical model to obtain the parameter range of the sensor structure.Based on the above analysis,the influence of the sensor structure parameters on the objective function was studied by the adaptive multi-objective optimization algorithm with the maximum equivalent stress and the inherent frequency as the objective function.Finally,the specific parameters of the structure were determined,and the device size of 6000μm×2900μm.The sensitivity of the sensor was improved and the transverse effect was reduced without sacrificing the inherent frequency.The FEM simulations showed that the first-order frequency of the sensor was 0.66 MHz and the maximum equivalent stress under an acceleration of 200,000 g was 62.6 MPa,which verified the rationality of the structural design.Based on the theoretical analysis of the variation in resistivity and piezoresistive coefficient of monocrystalline silicon changing with temperature in piezoresistive sensors,the design of temperature compensation scheme on polycrystalline silicon wafer is proposed to solve the problem of low measurement accuracy of piezoresistive sensors in high temperature environment.The design of the piezo-resistors and the Wheatstone bridge with temperature compensation was completed by linear stress analysis with the MEMS process principles,and the theoretical sensitivity of the Z-sensitive unit and the X（Y）-sensitive unit were obtained by simulation as 0.17μV/g and 0.21μV/g,with the lateral sensitivity of less than 2%.The temperature drift coefficient of the compensated sensor is 7×10-4（1/℃）,which is a decrease of two orders of magnitude compared to the coefficient before compensation.Finally,by solving the key process technical difficulties such as piezo-resistors fabrication,bulk silicon etching process,and anode bonding,the fabrication process flow of high-g triaxial acceleration sensor is designed. |
