For the realization of modern 3D (Integrated Circuits) ICs new interconnect structures, such as through-silicon-vias and solder bumps, together with complex multi-level 3D ICs are gaining importance.
In the development of electronics packaging the principal aims are to lower cost, increase the packaging density, and improve performance while still maintaining or even improving the reliability of an integrated circuit. The application of new structures and materials inevitably introduces new reliability issues. The interconnect reliability is affected by degradation processes induced by thermal gradients, electromigration, and stressmigration.
Due to new technologies and ongoing miniaturization, the impact of the microstructure, which defines material properties and residual stresses in a metallic interconnect structure, gains importance. The systematic reliability study of interconnects in 3D stacked chips is currently not available. The reliability assessment of specific components of 3D interconnects and whole chips demands development of new TCAD methods and their utilization in combination with experimental reliability tests. The focus of our work is the development of models and simulation tools applicable to the most urgent reliability issues of modern 3D interconnects. Application of new materials and material compounds makes a multi-level modeling approach a necessity. The study of material properties demands approaches on the atomistic and microstructural levels. Within the scope of our research, the influence of the technology process conditions on microstructure and the residual stress in interconnects are studied and included in the overall analysis.
A wide spectrum of physical models and numerical methods is applied starting with ab initio calculations and molecular dynamics simulations at the lowest level. For a reliability study of interconnect components, such as through-silicon-vias and solder bumps, continuum mechanics and electromigration models are used and simulations based on the finite element method are carried out.