THE SURFACE EFFECT ON THE TENSILE STRENGTH OF MICROMACHINED POLYSILICON FILMS FOR MEMS

In order to accomplish reliable mechanical design of MEMS, the infuences of surface roughness and octadecyltrichlorosilane (OTS) self-assembled monolayers (SAMs) on the mechani- cal properties of micromachined polysilicon flms for MEMS are investigated. Surface efect on the fracture properties of micromachined polysilicon flms is evaluated with a new microtensile testing method using a magnet-coil force actuator. Statistical analysis of the surface roughness efects on the tensile strength predicated the surface roughness characterization of polysilicon flms being tested and the direct relation of the mechanical properties with the surface roughness features. The fracture strength decreases with the increase of the surface roughness. The octadecyltrichlorosi- lane self-assembled monolayers coating leads to an increase of the average fracture strength up to 32.46%. Surface roughness and the hydrophobic properties of specimen when coated with OTS flms are the two main factors infuencing the tensile strength of micromachined polysilicon flms for MEMS.