Abstract: A silicon machined high-performance monolithic triaxial piezoresistive accelerometer is developed for measurements on the order of 100,000g.A three-beam-mass scheme with tiny beams is developed for the xand yaxial elements,and a three-beam-twin-mass structure is developed for thez axial element.Both of these structures feature high sensitivity and high resonance frequency compared with a conventional cantilever structure or cantilever-mass structure.ANSYS is used to analyze and optically design the accelerometer.The three sensing elements are monolithically integrated by micromachining techniques of double-sided deep etching combined with piezoresistive processes.The middle structure silicon layer is anodic bonded with glass substrate and BCB bonded with a top cap silicon layer for the purpose of plastic packaging to improve the reliability of the accelerometer.A dropping-bar system is used to characterize the accelerometer.The sensitivities in the x,y,and z axes are measured to be 2.28,2.36,and 2.52μV/g,respectively,while the corresponding resonant frequencies are 309,302,and 156kHz.Using a Dongling shock test machine,the nonlinearity is tested by comparison calibration and measured to be 1.4% and 1.8% for the y and z axial elements,respectively.

Key words: silicon micromachining technology, triaxial accelerometer, piezoresistive, high-g, plastic package