Quality and mechanical reliability assessment of wafer-bonded micromechanical components

Strength tests and fracture mechanics models for Silicon wafer-bonded compo nents are presented which can be applied during the development of bonding technologies, for the yield improvement and failure analysis as well as for the reliability assessment of micromechanical sensors and actuators. Speci al attention is given to the influences of atomic bonding strength, the int erface voids and the notches caused by etching steps prior to bonding on th e fracture limit. If wafer-bonded interfaces are exposed to a mechanical lo ading for an extended time, e.g. in the order of months or years, stress co rrosion effects decrease the bonding strength. As a consequence, stressed s ensors and actuators fabricated by wafer bonding can suddenly fail during a pplication after a load-dependent lifetime. Based on an appropriate fractur e mechanics model, the time-to-failure data could be theoretically predicte d. (C) 1999 Elsevier Science Ltd. All rights reserved.