Piezoresistive CMOS beams for inertial sensing

This paper presents a preliminary study concerning the use of front-side bulk micromachining (FSBM) for inertial sensing. When using such a low-cost fabrication approach, the obtained suspended structure do not feature important seismic mass while both CMOS design rules and wet etching do not allow for capacitive detection. Using the standard CMOS polysilicon for piezoresistive detection, obtained results demonstrate that acceptable performance can be reached. In particular, the noise level in polysilicon gauges is low enough to enable a resolution of about 0.5g while sensitivity can be improved by designing dedicated on-chip amplification circuitry. Using both an analytical approach and experimental results, a sensitivity of about 27mV/g is expected for a CMOS-based sensor.