The Design And Measurement Of GaAs Substrate Meso-piezoresistive Micromechanical Gyroscope

With the rapid development of micro nano-materials preparation technology and micro nano-devices processing technology, the new devices based on superlattice quantum well structure were developed, and various effects were generated for the distinctness in nano-materials and structure dimensions. The new concept sensors based on these effects have been widely proposed immediately. Resonant tunneling structure (RTS) is a new type of piezoresistive device with meso-piezoresistive effect, and has the advantages of high sensitivity, small temperature drift. The micro-machine gyroscope is an inertial sensor to measure the angular velocity or angular displacement with the features of small size, light weight and high reliability, having great potential in the field of inertial navigation. It is an innovative research that combination the meso-piezoresistive effect of RTS with Coriolis effect used in MEMS gyroscope, which can improve the sensitivity of micro-gyroscope essentially.A GaAs substrate meso-piezoresistive MEMS gyroscopes based on meso-piezoresistive effect theory of the resonant tunneling structure is proposed in the paper, which introduces the design, processing and testing of meso-piezoresistive micromachine gyroscope. The gyroscope using electromagnetic driving and meso-piezoresistive detection methods, a fold-type orthogonal beam is used to achieve the requirements of drive and detection methods. The modal matching design of gyroscope is finished using ANSYS optimal design, the natural frequencies of driving modal and detecting modal are 3530Hz and 3671Hz, respectively. According to the damping analyzed of drive direction and detection direction, when the displacement gap is 15μm, the direction in the quality factor of drive and test direction are 4595.5 and 166 in atmospheric environment; the Coriolis effect simulation is processed by using ANSYS transient analysis. The GaAs/AlAs/InGaAs double-barrier single-well tunneling film structure is grown on the semi-insulating GaAs substrate using molecular beam epitaxy (MBE) technology. The RTS structure and gyroscope structure are fabricated by using GaAs substrate surface processing technology and bulk processing technology and achieved the processes compatible.According to the principle of electromagnetic drive and meso-piezoresistive detection, a simple test interface circuit is designed, and the characteristics of drive direction, detect direction and Coriolis effect are tested respectively. As the problem of process precision, it is show that the natural frequency and quality factor of drive direction are 4020Hz and 200.5, respectively. The output sensitivity of detect direction at 1 KHz and 4 KHz were 7.51mV/g and 100.74mV/g, respectively. The sensitivity of Coriolis effect is 9.35μV/°/s in the range of±550°/s.This is the primary exploration research of new concept meso-piezoresistive GaAs substrate micromachined gyroscope. As the problems existing in initial design, processing and testing, so it is worth studying the optimization of gyroscope structure, the improvement of processing technology and measurement method in future. The meso-piezoresistive micromachined gyroscope proposed in the paper has the potential of improving performances, and also shows potential applications.