Structural Design And Simulation Analysis For Bulk Micromachined Resonant Dual-axis Accelerometers Based On Crab-leg Supporting Beams

Micro-accelerometer is a kind of mechanical sensor used to measure acceleration.It has the advantages of small volume,light weight,easy integration,low power and cost,mass production and so on.Micro-accelerometer is also widely used in consumer electronics,health care,games entertainment,automotive electronics,earthquake monitoring,aerospace,missile guidance and other fields.Bulk micromachined resonant accelerometers can achieve a lower noise level because full-wafer thick proof mass can be fabricated.However,the thickness of supporting beams is far less than that of the proof mass.If the gravity center of the proof mass deviates from the neutral plane of the supporting system,the proof mass will rotate under in-plane acceleration,resulting in greater cross-axis sensitivity.The research group proposed a bulk micromachined resonant dual-axis accelerometer based on non-coplanar resonat beams and supporting beams which is composed of crab-leg supporting beams,equal cross-section resonant beams,a proof mass and a frame.The gravity center of the proof mass lies within the neutral plane of crab-leg supporting beams fabricated by the masked-maskless etching,which reduces the cross-coupling interference caused by rotation of the proof mass.However,due to the large in-plane elastic stiffness of equal cross-section resonant beams,the in-plane detection sensitivity of the accelerometer is low,and the proof mass will still rotate at a certain angle under in-plane acceleration.On the basis,two new resonant beams-the double tine beam and the H-beam are proposed in this paper.Among them,the double tine beam converts the rigid tensile/compressive deformation into bending deformation at the tine,which reduces the in-plane elastic stiffness of the resonant beam and the cross-axis sensitivity of the resonant dual-axis accelerometer.The simulation results show that the Cross-axis sensitivities C_XYand C_YXcaused by in-plane lateral acceleration are 0.097%and0.816%,respectively.The cross-axis sensitivities C_XZand C_YZcaused by Z-axis acceleration are 0.496%and 0.949%,respectively.The H-type resonant beam adopts the principle of electromagnetic excitation/electromagnetic detection,and the resonant beam with smaller width can be fabricated under same process conditions,so the H-type resonant beam can reduce the in-plane elastic stiffness of the resonant beam and the cross-axis sensitivity of the resonant dual-axis accelerometer.Simulation results show the sensitivity of X-axis and Y-axis are 146.87 Hz/g and 55.75 Hz/g,respectively.When the thickness of H-type resonant beam is 5μm,the cross-axis sensitivities C_XYand C_YXcaused by in-plane lateral acceleration are 0.016%and 0.035%,respectively.The cross-axis sensitivity C_XZand C_YZcaused by Z-axis acceleration are both 0.49%.So the designed resonant biaxial accelerometer based on non-coplanar resonant beams and supporting beams has higher in-plane detection sensitivity and lower cross-axis sensitivity.