Wafer-level Hermetic Packaged Dual-axis Digital Microaccelerometer

A wafer-level hermetic packaged X/Y dual-axis digital microaccelerometer is presented. The MEMS sensing element of the microaccelerometer is fabricated by the sacrificial bulk micromachining (SBM) process. The two microaccelerometers are fabricated on a same silicon substrate, and thus have a perfect orthogonality. To protect the silicon structure of the sensing element, a wafer-level hermetic packaging process is performed. The interface circuit of the microaccelerometer is fabricated using the 0.18 mum CMOS process. The capacitance change of the sensing element is converted to voltage signal by a charge amplifier. The analog signal is converted to digital signal by an A/D converter and a digital filter. The microaccelerometer has the scale factor of 9839 count/g, the output nonlinearity of 0.35 %FSO, the input range of plusmn0.83 g and the bias instability of 2.2965 mg for the x-axis, and the scale factor of 10087 count/g, the output nonlinearity of 0.38 %FSO, the input range of plusmn0.81 g and the bias stability of 7.1881 mg for the y-axis