An atomistic scale study on solidification in ultrafine interconnects

The electronic packaging technologies have been developed into the three-dimensional era to fulfill the increasing demands for lightweight, portable products. Recently, nano materials and structures have been investigated extensively to enable interconnection in microscale or even submicron scale. However, it is still challenging to establish the link between the atomistic scale structures to the properties of the nano materials. In addition, the physical mechanisms involved in the adoption of the nano materials have not yet been fully understood. This work presents an atomistic scale study on the solidification process in ultrafine interconnects using a phase field crystal method. The solidification rate, the grain boundary formation and the atomistic arrangement in the interconnects of different geometries are discussed. Simulation results show that the nuclei in the barrel-shaped and the rectangular joints grow faster than those in the hourglass-shaped joints. In addition, the grain boundary formation in the interconnects differs in different geometries. It is found that one of the grain boundaries in the hourglass-shaped interconnect is shifted compared to that in the thinner hourglass-shaped interconnects. Furthermore, the displacements between atoms in the simulated atomistic microstructure relative to the perfect lattice are plotted to show the geometry effect on the atomistic arrangement. Results show that the magnitude of the displacements depends on the geometry of the interconnects, and that the pattern of the stream-line plot of displacements is influenced by the position of the nucleus.