Operation of sub-micron gap electrostatic comb-drive actuators

Abstract

Resonant and nonresonant operation of submicron gap, electrostatic, comb-drive actuators is reported. Using a single-mask process and a 4- mu m-thick phosphorus-doped polysilicon layer as the structural material, a resonant actuator and a nonresonant, linear actuator were fabricated and tested. Resonant displacement amplitude of +or-5.2 mu m was observed in a resonant actuator with 0.3- mu m gaps when an AC drive voltage of 11.5 V (peak) without bias was applied. Maximum displacements of 3.6 mu m were observed in a nonresonant linear actuator with 0.2- mu m gaps when a DC drive voltage of 11.1 V was applied. A postrelease assembly technique is used to position and fix the comb-drive suspension such that the drive electrodes of the nonresonant linear actuator are in the submicron gap region prior to the application of the drive voltage. Measured displacements of linear actuators with 0.2-0.65- mu m gaps show little hysteresis and observed performance parameters which are in good agreement with theoretical predictions.