Microleverage Mechanism Assisted Novel Biaxial Piezoresistive Micro Accelerometer With Improved Sensitivity

A novel structure was presented for a microelectromechanical system (MEMS) piezoresistive (PZR) accelerometer. Taking the advantage of the effects of the tiny piezoresistive beam (TPB) to generate stress concentration region (SCR) and microleverage mechanism to amplify the force, a PZR accelerometer was proposed with improved sensitivity. The measured sensitivity was determined by the amplified inertia force applied to the TPBs. Based on the model analyses, the force amplification factor was influenced by the beams' spring constants and the distance between support beam and TPB. The simulations were further carried out to verify the effects of amplifying force and find out the effects of dimensional parameters on amplification factor. The results suggested that the amplification factor was influenced by support and hinge beam widths dramatically, and also affected by the distance between support beam and TPB. Based on the simulation findings, three prototypes (denoted by XJTU_11, XJTU_12, and XJTU_32) were proposed with different support and hinge beam widths along with the distance between support beam and TPB to verify the amplification effect. Furthermore, the prototypes were successfully fabricated by MEMS technology with a size of $4.4\times4.4$ mm and packaged for experimental tests. The sensitivities were determined to be 1.03 mV/g/5 V, 0.871 mV/g/5 V, and 0.736 mV/g/5 V for XJTU_11, XJTU_12, and XJTU_32, respectively. The sensitivity of XJTU_11 increased by 18.4% and 40.1% compared with XJTU_12 and XJTU_32, respectively. The results indicated that the higher amplification factor was beneficial to the device to obtain the higher sensitivity. The figure of merit (FOM) showed that proposed accelerometer obtained a more favorable comprehensive performance. This new design provided a good strategy and revealed the promising potential in improving the accelerometer's sensitivity.