A single-sided process for differentially cooled electrothermal micro-actuators

A simple method for increasing the thermal efficiency of shape bimorph electrothermal micro-actuators is proposed, based on a reduction of gas conduction cooling beneath the hot arms by a deep, localized undercut. A single-sided, single-mask SCREAM-type process for fabricating differentially cooled actuators in a bonded silicon-on-insulator material is demonstrated. The process uses deep reactive ion etching and undercut to form suspended parts and isotropic reactive ion etching and lift-off of sacrificial shields to form localized mesas. The advantage of the method is confirmed using folded electrothermal actuators, and an approximate halving of the drive power is demonstrated by variations in the substrate profile in the vicinity of a series of actuators with the same mechanical design.