Wafer-level sandwiched packaging for high-yield fabrication of high-performance mems inertial sensors

A wafer-level sandwiched packaging technology is developed for micromechanical sensors such as inertial sensors, which comprise movable parts, e.g. spring-mass structures. Via a thin polymer intermediate layer of benzocyclobuene (BCB), a pre-micromachined silicon cap wafer is aligned bonded with the sensor-chip wafer. Prior to the BCB bonding, the sensor-chip wafer was formed by anodic bonding a Pyrex-7740 glass wafer to the silicon wafer with the sensing elements formed. This sandwich wafer level packaging can protect the formed micromechanical structures from damage or dirty during the saw dicing, and facilitates plastic molding device package. With the technique, various kinds of accelerometers have been high-yield and low-cost packaged.