In-depth Raman spectroscopy analysis of various parameters affecting the mechanical stress near the surface and bulk of Cu-TSVs

This paper discusses mechanical stress measured with micro-Raman spectroscopy in the silicon substrate near Cu-Through Silicon Vias (TSV). A discussion of the relation between the observed Raman shift and the various stress tensor components is given, showing that this relation is often wrongly applied, and that in many cases the compressive stress along the vertical axis of the TSV, dominates the Raman results and hides the tensile axial component which is of most relevance for its impact on CMOS devices. The effect of measurement depth, TSV depth and density, and an oxide cap is shown. Both surface and cross-sectional results are discussed. Also a direct correlation between results from Raman measurements and electrical results from FET-arrays near a TSV is given.