Quality and mechanical reliabiltiy assessment of wafer-bonded micromechanicla components

摘要

Strength tests and fracture mechanics models for Silicon wafer-bonded components are presented which can be applied during the development of bonding technologies, for the yield improvement and failure analysis as well as for the reliabiltiy assessemtn of micromechanical sensors and actuators. Special attention is given to the influences of atomic bonding strength, the interface voids and the noteches caused by etching steps prior to bonding on the fracture limit. If wafer-bonded inteerfaces are exposed to a mechanicla loading for an extended time, e.g. in the order to months or years, stress corrosion effects decrease the bonding strength. As a consequence, stressed sensors and actuatiors fabricated by wafer bonding can suddenly fail during appkication after a load-dependent lifetime. Based on an appropriate fracture mehcanics modle, the time-to-failure data could be theoretically predicted.