Wafer-Level Packaging of MEMS Accelerometers with Through-Wafer Interconnects

Abstract

Micromachined accelerometers were packaged at waferlevel by bonding a through-hole etched cap wafer to a micromachined device wafer using glass frit. Interconnections from the bond pads on the device wafer to the top of the cap wafer were made through the holes using sputter-deposition of metals. The bonded pair was then solder bumped, and diced for individually packaged devices. The wafer-level packaged dual-axis accelerometer was 2.3 mm by 2.3 mm in size (the same as its unpackaged die) and 1.1 mm in thickness. This small form factor device demonstrated the same functionality as production accelerometers when it was probed in wafer form as well as when it was mounted on a board. This waferlevel packaging method allows significant cost savings over traditional micromachined device packaging.