Technologies, applications, and reliabilities of microelectromechanical systems (MEMS)

Microelectromechanical System (MEMS) means batchfabricated miniature devices that integrate sensors and/or actuators to signal conditioning circuits on silicon chips. MEMS is expected as a key component for realizing a new function to various existing systems in consumer, automobile, aeronautics, and instrument applications. Mechanical sensors, such as pressure sensors, accelerometers, and vibrating gyroscopes have been and will be one of the major applications of MEMS. They started with “bulk silicon type” with single crystals silicon structure using piezoresistive sensor and fabrication by anisotropic etching of silicon. They now move into “surface type” with thin films as structures using capacitive sensors and fabrication by sacrificial etching technique. Optical devices are another successful application of MEMS. Not only projection display devices, but also thermal type infrared image sensors and optical switches for fiber optical telecommunication systems have been developed. Such application expansion and product development demand knowledge of the mechanical properties of materials in MEMS. Especially, the mechanical reliabilities are being matters of great concern. Researches on the investigation of the mechanisms and the development of fatigue life prediction methods are being undertaken widely, which will provide us proper knowledge on the fatigue failure and lifetime prediction of MEMS devices.