Orientation-dependent atomic diffusion and interfacial evolution in Au–Si eutectic bonding: A molecular dynamics study

Abstract

This work systematically investigates the interfacial structure evolution, atomic diffusion behavior, strain distribution, and defect formation mechanisms of Au–Si bonding systems with different crystallographic orientation combinations. The results demonstrate that the interfacial properties, atomic mobility, and eutectic bonding performance of the bonding systems strongly depend on the crystal orientation of the Au–Si interfaces. Among the Au–Si (100) bonding systems, the Si (100)–Au (110) interface exhibits the strongest interfacial diffusion capability and atomic mixing behavior due to the relatively open atomic arrangement of the Au (110) surface, which effectively reduces the eutectic nucleation barrier and expands the effective eutectic reaction region. In the Au–Si (110) bonding systems, although the Si (110)–Au (100) and Si (110)–Au (110) interfaces exhibit relatively high mean squared displacement values, the actual number of diffused atoms and the diffusion depth along the z-direction remain limited because of the high vertical diffusion barrier of the Si (110) crystal plane. In addition, obvious stacking faults, localized hexagonal close packed phase transformation, and dislocation structures are observed in these systems, indicating that the interfacial strain could be released through defect-mediated structural evolution. Overall, the simulation results confirm that the Si (100)–Au (110) interface is the most favorable structure for Au–Si eutectic bonding.