Wafer level sandwich packaging technology for three-axis piezoresistive accelerometer

A technology for packaging a three-axis piezo-resistive accelerometer, namely, “wafer level sandwich packaging” was developed. This technology consists of three key processes: first, concurrent bonding of three stacked wafers; second, eutectic bonding using Au-Sn alloyed metal; and third, a top cap separation by polishing. It was used to fabricate the smallest dies for a piezoresistive accelerometer, namely, 1.18 mm wide, 1.32 mm long and 0.6 mm high, reported to date.