Fast low-temperature–pressure Cu-Sn mechanical interlock bonding (MIB) applied for 3D integration

[Display omitted] •A mechanical interlock Cu-Sn bonding technology is proposed.•The pre-bonding is achieved at 150&200 °C with the pressure of 0.40 MPa in 5 min.•Owing to the interlock structure, the pre-bonded chips can afford shear force.•The bonded chips are conductive and have high shear strength.•Large Cu6Sn5 grains in the IMC indicate good electromigration resistance. Multi-chip bonding in 3D integration always consumes much processing time. This study provides a novel mechanical interlock bonding (MIB) technology, which can save bonding time and has lower bonding temperature and pressure. The mechanical interlock structure enables pre-bonded pairs to afford shear force for further transferring. Chip-to-chip bonding is implemented by pre-bonding at the temperature of 150 and 200 °C with the pressure of 0.40 MPa in 5 min, and one-time annealing at the temperature of 260 °C in 30 min. The average shear strength of 70.39 MPa and average Kelvin resistance of 3.23 mΩ show good bonding quality. Interface observation shows continuous intermetallic compound (IMC) comprised of Cu3Sn/Cu6Sn5/Cu3Sn has formed. Large Cu6Sn5 grains are detected which indicate good electromigration resistance. This MIB technology is an economical technology which can be used in 3D integration.