Elimination of the axial deformation problem of Cu-TSV in 3D integration

The out‐of‐plane expansion of Copper Through‐Silicon‐Via (Cu‐TSV) is a concern in 3D stacking of chips, since it pushes against the BEOL, thus posing a possible reliability risk. In this study we demonstrate a solution for the Cu‐TSV out‐of‐plane expansion problem resulting in a non‐deformed BEOL. This is achieved through gaining a good understanding of the thermo‐mechanical behavior of Cu by experiments and adopting this learning in our process flow.