A Diaphragm Triaxial Force Sensor Using Soi Technology With High Sensitivity and Large Force Range

This paper reports a diaphragm triaxial force sensor fabricated on a SOI wafer with silicon piezoresistors as sensing elements. A 700μm × 700μm × 20μm sized photoresist was used as a force contact interface and DRIE technology was adopted to form a back cavity with a 30μm thick diaphragm. By optimizing the resistance and layout of the piezoresistors, a normal force of 720mV/N along Z-axis, a shear force of 259.8mV/N along X-axis, and a shear force of 285.6mV/N along Y-axis were obtained for the unpackaged sensor respectively. The minimum detectable force was calculated to be 2.8μN with a force range of 1.4N. By packaging this sensor with a designed resin structure, the force range is expanded to more than 40N, and the sensitivities of the three axes are still keep greater than 10mV/N.