Fabrication of Freestanding Metallic MEMS Actuator for Minimal Stress-Induced Air-gap Variations

Abstract

Suspended micro/nano-structures are the essential building blocks for a variety of micro/nano electromechanical (N/MEMS) applications. Owing to process variability these suspended blocks comprised significant residual-stress/stress-gradient during the fabrication, resulting in curled actuator profile that directly affects the actuation-gap ($G$). The electrostatic switching devices are highly sensitive to gap variations (as pull-in voltage, $V_{pi}^{2}\propto G^{3}$). The present method and the results of its experimental investigation provide a compatible process for realizing invariant actuation air-gap using effective bending control essential requirement for electrostatic devices. We report a laser-driven scheme for stress reduction in the cantilever-based molybdenum micro-actuators without using any high-temperature process, like rapid thermal annealing (RTA). Finally, this method helps to realize freestanding micro/nano-actuators for various M/NEM devices (e.g. resonators, sensors and actuators) and can be used to reduce stress in back end of line (BEOL) technology.