Laser-induced thermo-compression bonding for Cu-Au heterogeneous nanojoining

Surface tension-induced shrinkage of heterogeneously bonded interfaces is a key factor in limiting the performance of nanostructures. Herein, we demonstrate a laser-induced thermo-compression bonding technology to suppress surface tension-induced shrinkage of Cu-Au bonded interface. A focused laser beam is used to apply localized heating and scattering force to the exposed Cu nanowire. The laser-induced scattering force and the heating can be adjusted by regulating the exposure intensity. When the ratio of scattering forces to the gravity of the exposed nanowire reaches 3.6×10³, the molten Cu nanowire is compressed into flattened shape rather than shrinking into nanosphere by the surface tension. As a result, the Cu-Au bonding interface is broadened fourfold by the scattering force, leading to a reduction in contact resistance of approximately 56%. This noncontact thermo-compression bonding technology provides significant possibilities for the interconnect packaging and integration of nanodevices.