Surface micromachining

Abstract

An overview of surface micromachining techniques is given and major applications are described. The sacrificial layer technology for the fabrication of free-standing thin-film structures (e.g. polysilicon) by lateral underetching of an underlying sacrificial layer (e.g. silicon dioxide) is discussed in detail. Another technological approach uses the combination of standard IC processing steps with crystal-orientation-dependent etching of the silicon substrate surface for the construction of free-standing multilayer microstructures. A third surface micromachining technique is based on isotropic plasma etching of the silicon substrate for the realization of micromechanical structures at the wafer surface. The state of the art of microstructures realized by the sacrificial layer technology is illustrated by several examples such as comb actuators, micromotors, switches, resonators and microcavities.