Finite Element Analysis of the Effect of Surface Roughness on Nanometer-scale Contact

Low temperature process has been a technological goal of interconnect and bonding of solid materials. Especially, surface activated bonding (SAB) is a key technology of high density electronic packaging and interconnect. By decreasing the bonding temperature using SAB method, the problem of the thermal expansion coefficient mismatch between diverse materials is solved. And, high accuracy positioning is realized. In this study, FEM analysis of the contact process is investigated for bonding Au thin films on Si wafers with nanometer-scale roughness. The influence factors to the contact ratio and the stress distribution are clarified quantitatively in terms of applied load, adhesion force between contact surfaces, and residual stress. A rough surface with periodical distributed asperities bonded onto a rigid plane was investigated by using FEM numerical simulation for elasto-plastically deformation. The necessary condition for the full contact of the surfaces is that the amplitude height of surface roughness is less than 3.0 nm.