Measurement of MEMS Actuator Deflection by C-V Method

Abstract

This study explores the correlation between indirect and direct deflection measurement techniques for MEMS actuators. The measured airgap capacitance is used to calculate deflection using parallel plate model and FEM extracted model for indirect technique. Direct device deflection is measured using an optical profilometer. A 110 µm long and 2.5 µm thick Si-folded cantilever beam with 460 nm airgap electrostatic actuation is used for the measurement. The characterization shows that the device pre-pull-in deflection is up to 98 nm for 4V range with both the methods. The calculated data demonstrate that, in contrast to the parallel plate, which has a 12.7% mean square error, the FEM calibrated model agrees with profilometer to within 8.6% for pre-pull-in deflection.