3D integration of MEMS and CMOS via Cu-Cu bonding with simultaneous formation of electrical, mechanical and hermetic bonds

A silicon-on-insulator (SOI) micro-electromechanical system (MEMS) accelerometer, complementary Metal oxide semiconductor (CMOS) readout circuit and simultaneous hermetic encapsulation using low temperature Cu-Cu bonding are investigated for 3D heterogeneous integration of MEMS and CMOS. The MEMS accelerometer is fabricated using bulk micromachining technology. A CMOS-based readout circuit is designed in AMS 0.35μm (2P4M) process. Consequently, hermetic encapsulation by low temperature Cu-Cu thermo-compression bonding has been investigated. According to MIL-STD 883E standard, excellent hermeticity is obtained. A TSV-less stacking method is proposed. Compared with the common integration technologies such as through silicon via (TSV) and wire bonding, this method forms the electrical contact, mechanical support and hermetic seal simultaneously via Cu-Cu thermo-compression bonding.