The pull-in of symmetrically and asymmetrically driven microstructures and the use in DC voltage references

Abstract

Micromechanical structures have been designed, fabricated in silicon and tested for use as on-chip voltage reference Applications are in electrical metrology and in integrated silicon Microsystems. Microbeams of 100 /spl mu/m length, 3 /spl mu/m width and 11 /spl mu/m thickness are electrostatically actuated with a very reproducible pull-in voltage. The structure can be either symmetrically or asymmetrically actuated, resulting in different pull-in voltages, as well as different operational specifications e.g. hysteresis and reproducibility. A two dimensional energy-based analytical model for the static pull-in is derived for both actuation types and compared with measurements. Devices have been designed and fabricated in an epi-poly process. Measurements show a pull-in voltage in the 9.1-9.5 V range for the asymmetric case and 10.5-11 V range for the symmetric case, both in agreement with modeling.