Silicon Microcantilevers with Piezoresistive and MSE Detection

We have fabricated 340 nm thick U-shaped microcantilevers with electrical output to be used as sensors for biomolecular detection, which requires a force resolution better than 100 pN. Piezoresistors or MOS transistors have been used as integrated electromechanical transducers. The devices have been fabricated by N-type doping using As ion implantation to obtain shallow junctions, and have been oriented on the (100) crystallographic direction (45deg from the wafer flat) to maximize piezoresistance. Both types of cantilevers have been successfully fabricated. The integrated MOSFETs have shown good conduction characteristics. We report an (amplified) force sensitivity of 60 muV/pN for piezoresistive cantilevers 250 mum long and 8 mum wide.