Chapter 14: MEMS (Micro-Electro-Mechanical Systems) for Automotive and Consumer Applications

Operating principle of a yaw rate sensing element
Operating principle of a yaw rate sensing element

MEMS sensors gained over the last two decades an impressive width of applications:
(a) ESP: A car is skidding and stabilizes itself without driver intervention
(b) Free-fall detection: A laptop falls to the floor and protects the hard drive by parking the read/write drive head automatically before impact.
(c) Airbag: An airbag fires before the driver/occupant involved in an impending automotive crash impacts the steering wheel, thereby significantly reducing physical injury risk.
MEMS sensors are sensing the environmental conditions and are giving input to electronic control systems. These crucial MEMS sensors are making system reactions to human needs more intelligent, precise, and at much faster reaction rates than humanly possible. Important prerequisites for the success of sensors are their size, functionality, power consumption, and costs. This technical progress in sensor development is realized by micro-machining. The development of these processes was the breakthrough to industrial mass-production for micro-electro-mechanical systems (MEMS). Besides leading-edge micromechanical processes, innovative and robust ASIC designs, thorough simulations of the electrical and mechanical behavior, a deep understanding of the interactions (mainly over temperature and lifetime) of the package and the mechanical structures needed. This was achieved over the last 20 years by intense and successful development activities combined with the experience of volume production of billions of sensors.
This chapter gives an overview of current MEMS technology, its applications and the market share. The MEMS processes are described, and the challenges of MEMS, compared to standard IC fabrication, are discussed. The evolution of MEMS requirements is presented, and a short survey of MEMS applications is shown. Concepts of the newest inertial sensors for ESP-systems are given with an emphasis on the design concepts of the sensing element and the evaluation circuit for achieving excellent noise performance. The chapter concludes with an outlook on arising new MEMS applications such as energy harvester and micro fuel cells.


Udo Gómez
Jiri Marek