Three-dimensional micro-Raman spectroscopy mapping of stress induced in Si by Cu-filled through-Si vias

Three-dimensional (3D) micro-Raman spectroscopy mapping of mechanical stress induced by Cu through-Si vias (TSVs) in the Si substrate is reported. The 3D-map is obtained by combining 2D-maps measured at different positions along the cross-section of TSVs. The results highlight the relaxing effect of cross-sectioning on the stress field and show that conventional 2D-measurements on cross-sections can seriously underestimate the real stress values. Using this technique, the impact of post-plating anneal on the TSV stress is measured and shown to correlate very well with TSV stress data obtained from wafer bending experiments.