Achieving low-temperature wafer level bonding with Cu-Sn-In ternary at 150 °C

In this work, a low-temperature wafer-level bonding process at 150 °C was carried out on Si wafers containing 10 µm-sized microbumps based the Cu-Sn-In ternary system. Thermodynamic study shows that addition of enables low-melting temperature metals to reach liquid phase below melting point (157 °C) and promotes rapid solidification intermetallic layer, which are beneficial for achieving bonding. Microstructural observation high quality with low amount defect. SEM TEM characterization concludes single-phase formed in bond identified as Cu6(Sn,In)5 hexagonal lattice. Mechanical tensile test indicates has mechanical strength 30 MPa, adequate 3D heterogeneous integration.