Modeling MEMS devices for Automotive Applications

Copyright © 2004 SAE International Applications of micro-electromechanical systems (MEMS) in automobiles are fairly recent. The two most common examples of MEMS use in automobiles are in crash sensing for airbag deployment, and in manifold absolute pressure sensing. There are, however, several other areas where MEMS devices are expected to replace more traditional technologies within the next few years. MEMS devices/systems (e.g. sensors and actuators) have several vital advantages over more traditional technologies. Because of highly reliable batch processing techniques, large volumes of highly uniform devices can be produced at relatively low unit cost. Since MEMS have virtually no moving parts to wear out, they are extremely reliable and long lasting. With the advent of microprocessor compatibility imposed on many automotive sensor/actuator applications, silicon based MEMS sensors will have a very efficient interaction with the controlling microprocessors. With increasing use of MEMS devices in automotive applications, modeling and simulation of these devices will become more and more important. Although CAE has a very important place in the development cycle of the automobile, the CAE needed for MEMS has some significant differences. Because of the much smaller dimensions of MEMS devices, forces that are normally neglected in macro-structural CAE cannot be neglected any more. Behavior of material in bulk form is quite different from that in thin film form. MEMS devices exhibit the interaction of mechanical, electrical, magnetic, thermal, and other physical phenomena, and therefore simulation of these devices has to be able to capture this multi-physical interaction. This paper will discuss all these important issues that need to be addressed in MEMS modeling and illustrate them through actual simulation cases of MEMS devices