Development of a MEMS position transducer using bulk piezoresistivity of suspensions

This paper addresses a new position transducer for nanopositioners fabricated through a standard micro-electromechanical systems (MEMS) process. The sensor works based on bulk piezoresistivity of a pair of single-crystal silicon beams, which suspend a nanopositioner stage. The beams are deliberately angled to experience opposite axial forces during the motion, yielding opposite piezoresistive changes in their resistances. A Wheatstone bridge and an instrumentation amplifier differentially transform the changes in the beam resistances into the output voltage of the sensor. In comparison with a sensors employing just one monocrystalline or polycrystalline silicon flexible beam as piezoresistor, the proposed design has considerably more linear characteristics, higher resolution and dynamic range, as well as lower noise and drift.