Fabrication of Thermally-Driven Polysilicon Microactuator and Its Characterization

열구동형 폴리실리콘 마이크로 액츄에이터의 제작 및 특성분석

A thermally-driven polysilicon microactuator has been fabricated using surface micromachining techniques. It consists of P-doped polysilicon as a structural layer and TEOS(tetraethylorthosilicate) oxide as a sacrificial layer. The polysilicon was annealed for the relaxation of residual stress which is the main cause to its deformation such as bending and buckling. And newly developed HF GPE(gas-phase etching) process was also employed to eliminate the troublesome stiction problem using anhydrous HF gas and CH$_{3}$OH vapor, and successfully fabricated the microactuators. The actuation is incurred by the thermal expansion due to the current flow in the active polysilicon cantilever, which motion is amplified by lever mechanism. The moving distance of polysilicon microactuator was experimentally conformed as large as 21 .mu. m at the input voltage level of 10V and 50Hz square wave. The actuating characteris- tics are also compared with the simulalted results considering heat transfer and thermal expansion in the polysilicon layer. This microactuator technology can be utilized for the fabrication of MEMS (microelectromechanical system) such as microrelay, which requires large displacement or contact force but relatively slow response.