Unraveling thermo-mechanical stress-driven grain evolution and rotation in through-silicon vias for advanced packaging

As the dimensions of Cu-filled through-silicon vias (TSVs) in 3D integrated circuits (ICs) continue to scale down, the microstructure of the Cu filler critically impacts the mechanical integrity and reliability of advanced packaging. This study develops a physics-based numerical framework to elucidate the thermo-mechanical stress-driven grain evolution and crystallographic rotation within TSVs. The results demonstrate that thermal stress accelerates grain coarsening and leads to preferential occupancy of the Cu filler by grains with the [100] direction aligned with the x -axis. This orientation selectivity is governed by anisotropic elastic strain energy distributions, which drive both rotation and stabilization of energetically favorable grains. Moreover, the TSV exhibits a significant decrease in the Young’s modulus of the Cu filler, indicating softening and reduced hardness, in agreement with previous experiments. These findings offer mechanistic insight and a predictive framework for stress-driven grain evolution, enabling microstructure-level design to enhance TSV reliability in advanced 3D packaging.