Design and Fabrication of iicroelectromechanical Systems

An attempt has been made to summarize some of the important developments in the emerging technology of microelectrom echanical systems (MEMS) from the mechanical engineering perspective. In the micro domain, design and fabrication issues are very much different from those of the macro world. The reason for this is twofold. First, the limitations of the micromachining techniques give way to new exigencies that are nonexistent in the macromachinery. One such difficulty is the virtual loss of the third dimension, since most of the microstructures are fabricated by integrated circuit based micromachining techniques that are predominantly planar. Second, the batch-produced micro structures that require no further assembly, offer significant economical advantage over their macro counterparts. Furthermore, elec­ tronic circuits and sensors can be integrated with micromechanical structures. In order to best utilize these features, it becomes necessary to establish new concepts for the design of MEMS. Alternate physical forms of the conventional joints are considered to improve the manufacturability of micromechanisms and the idea of using compliant mechanisms for micromechanical applications is put forth. The paper also reviews some of the fabrication techniques and the micromechanical devices that have already been made. In particular, it discusses the fabrication of a motor-driven four-bar linkage using the "boron-doped bulk-silicon dissolved-wafer process" developed at The University of Michigan's Center for Integrated Sensors and Circuits.