High temperature investigation on a nickel-tin transient liquid-phase wafer bonding up to 600 °C

This paper reports on the capability of a nickel-tin (Ni-Sn) bond solder to be stable at high temperature application up to 600 °C. The Ni-Sn bond solder is fabricated using a transient liquid phase method of a 6'' wafer-level bonding technique. The capability is determined by investigating the phase change of Ni-Sn compounds, which are grown within the bond solder, as well as the mechanical and electrical stability of the bond solder before and after annealing (in vacuum at 600 °C for 24 h). After annealing, the Ni-Sn phase has transformed to a new Ni-Sn phase with a higher re-melting temperature. A shear test has determined that the bond solder exhibits a relatively high bond strength before and after annealing. Using a daisy chain structure, the electrical resistance of the bond solder is determined and encounters a tolerable increase after annealing. Re-melting of the bond solder has not occurred during annealing. The daisy chain structure can be adapted for creating a bond solder which has a dense microstructure.