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 etch-ing do not allow for capacitive detection. Using the stan-dard CMOS polysilicon for piezoresistive detection, ob-tained 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