Full characterisation of pull-in in single-sided clamped beams

The most striking characteristic of the voltage-to-deflection curve of an electrostatically actuated beam is pull-in. The actual value of the pull-in voltage depends on: drive mode, temperature dependence and dielectric charging related drift. These aspects have been analysed using structures designed for a 9 V nominal pull-in voltage and fabricated in a commercially available epipoly process. Single-sided clamped beams have been used to avoid any influence of residual stress in the beam on pull-in. Typical results are: less than 5% variation of the pull-in voltage over a wafer, 0.17–1.9 V hysteresis depending on drive mode, a −1 mV/K TC and −12 mV drift during the first 2 weeks of operation.