Method for performance improvement and size shrinkage of a three-axis piezoresistive accelerometer with guard-ring structure

A stress isolation guard-ring to reduce the unwanted signals induced by the environmental disturbances for a packaged three-axis piezoresistive accelerometer is proposed [1-2]. This study further reports an optimum design to shrink the size of guard-ring, yet maintain the performance of accelerometer. The commercial finite element analysis (FEA) software, CoventorWare, is employed to evaluate the candidate designs of sensors. The Taguchi´s optimum design method is further employed to improve the sensor performances under environment disturbances and to shrink the size of the stress isolation structure. Based on the results, the performance of the accelerometer is improved both in offset shift and sensitivity shift for one order of magnitude, and the size of the stress isolation structure (the sum of guard-ring length/width and connection bridge length) has been shrunk for 29% (from 138 μm to 98 μm). Moreover, the unwanted higher vibration modes are far away from the first three modes. The proposed accelerometer design keeps the advantages of the original three-axis accelerometer design.