Single crystalline silicon based surface micromachining for high precision inertial sensors: technology and design for reliability

Abstract

In this paper, a foundry process for surface micromachined inertial sensors such as accelerometers or gyroscopes is introduced, with special attention on reliability aspects. Reliability was a major focus during the development phase, leading to the choice of the single crystalline silicon layer of an SOI device wafer as the mechanically active material. Glass frit wafer bonding is used for capping and hermetic sealing, but in addition to these fundamental reliability aspects, many influences on reliability must be considered, such as the risk of sticking, local stress concentration, electrical effects or the defined limitations of the mechanical movement in the interaction of design and technology. Reliability test results, as well as measures for improving the reliability and performance, are discussed in this paper.