Thermal and spatial dependence of TSV-induced stress in Si

The thermal and spatial variation of Cu TSV-induced stress has been investigated for 1×4 arrays of 5 μm diameter × 50 μm TSVs using microRaman imaging. Following post-CMP annealing the measured Si Raman shift outside the TSV array is slightly modified. In strong contrast, the Si Raman shift midway between TSVs transitions from a tensile to compressive state as the annealing temperature increases. Topographic analysis implies this shift is associated with thermally-induced Cu extrusion.