A miniature, high sensitivity, surface micro-machined displacement sensor with high resolution

In this paper, two types of cantilever based micromechanical structures have been reported in order to reduce the operating voltage by design optimization. Out of these two structures, the first one is a simple cantilever beam integrated with a tip, and having an enlarged actuation electrode to reduce the actuation voltage and taken as a reference structure. The second structure is an identical version of the first one except having a symmetric serpentine flexure for further reduction of actuation voltage. The dimensions of the structures are optimized obeying standard PolyMUMPs process. The work emphasises on the analysis of relationships among the tip current, tip voltage and actuation voltage of the second type of structure in low tunneling voltage region as well as in a medium tip voltage region which is less than the work function of the poly silicon. Based on these analysis, the serpentine structure has been implemented as a displacement sensor with high resolution and sensitivity, The displacement sensitivity of the sensor is in the order of 10^-2 m/A in tunneling region and 10^-4 m/A in mid voltage region. In both domains, displacement resolution is in Å order.