Thermal and spatial profiling of TSV-induced stress in 3DICs

The thermal and spatial variation of Cu through silicon via (TSV)-induced stress in 300 mm Si wafers has been investigated for both isolated TSVs and TSV arrays using top-down and cross-sectional spectral microRaman imaging. The TSV-induced stress in Si results from plastic yield of the Cu, is compressive in the immediate vicinity of the TSV, and transitions to a tensile state at larger separations - in quantitative agreement with finite element modeling (FEM). TSV arrays (linear and square) lead to substantial tensile stress enhancement within the array. Moreover, thermal annealing showed that the intra-array Si stress field became more compressive with increased post-CMP thermal annealing while the Si stress-field external to the arrays exhibited little change. This may open potential avenues for reduction of TSV-induced Si stress in 3DICs.