Abstract
Increased performance requirements in terms of the environment, safety and comfort have recently been imposed on automobiles to ensure efficient use of the earth´s limited natural resources, as well as safety and comfort in users´ lives. To fulfill these requirements, automobiles now incorporate various sensors for feedback control based on the information that these sensors provide. Especially, air-bag technology and other similar safety enhancement technologies, which directly protect human lives, have developed dramatically since they became commercially practicable in the late 1980s. An air-bag system incorporates acceleration sensors for collision detection. They are categorized as critical parts. A current-model automobile with full options would incorporate 10 or more acceleration sensors.
Denso acquired expertise in MEMS technology when the company first commercialized pressure sensors in 1981. The company made full use of this technology and in 1989 developed and marketed a piezo-resistive semiconductor-based acceleration sensor ahead of its competitors. In the latter half of the 1990s, acceleration sensors used in automobiles had to be miniaturized, intelligent, energy efficient, and be capable of performing self-diagnosis. Of these functions, self-diagnosis was clearly the most important. Various capacitive systems have been developed by applying MEMS technology as well as introduced by others.(1)-(2) Subsequently, in 2000 we successfully developed a capacitive semiconductor-based acceleration sensor with a built-in self-diagnosis function, and achieved production growth.
In recent years, however, increased use of automotive acceleration sensors has resulted in increased demand for miniaturization and cost reduction. Under these circumstances, we reconsidered double-sided processing and adopted original surface processing alone, thereby making possible substantial miniaturization and cost reduction.
Keywords: Acceleration sensor, Air-bag system, Self-diagnosis function, MEMS technology, Semiconductor sensor