Microsystèmes - Definitions, principles and technologies

The microsystem concept was born in the late 1980s in the United States, as a result of efforts at UC Berkeley to integrate sensors, associated signal processing and actuators on a single silicon chip. The novelty at the time lay in the integration of electrostatic actuators in the form of rotary or linear motors. This concept very quickly aroused keen interest in the industrial world, with prospects for integration and collective manufacturing at lower cost. Numerous examples were explored, and several generations of products were marketed from 1990-2000 onwards, from accelerometers in car airbags to inkjet print heads, micro-mirrors in video projectors, micro-switches and filters for telecoms or micro-fluidic chips.

These new devices are called MEMS (Micro Electro Mechanical Systems) in the USA, micromachines in Japan and MST (MicroSystems Technologies) in Europe, or simply microsystèmes in France. A major advantage is that they combine microelectronics and manufacturing technologies in a single design.

The following article begins with some background on the birth of the microsystems concept, with a few illustrative examples, then goes on to give the definitions and main operating principles enabling their design. It describes the basic functions available in terms of sensors (micromechanical, chemical and biochemical, optical, magnetic...), and actuators (electrostatic, piezoelectric and electromagnetic...). It then presents the manufacturing processes, in particular those specific to microsystems, right through to the packaging aspects. It describes the basic manufacturing technologies, explaining how they are inspired by microelectronics and where they are new. A number of applications are provided for illustration throughout the article.