Thermomechanical stress analysis of copper/silicon interface in through silicon vias using FEM simulations and experimental analysis

This paper reports results on FEM modeling in order to calculate stress distribution at the Cu/Si boundary of TSVs after the fabrication process (annealing) using ANSYS software. Residual interfacial shear stress is estimated to be close of 200MPa for a 5μm radius circular copper filled TSVs while Von-Mises simulations give a radial distribution with a maximum above 500MPa around the TSV. All these results are in good agreement with those recently published by E. Suhir on same configuration. Experimental detection and characterization capability of stress distribution around the circular TSV have been conducted by Scanning Acoustic Microscopy (SAM) technique in C-SCAN mode using specifically shear wave mode imaging. We demonstrated that such an analysis can provide complementary information on stress analysis in contrast of classical C-SCAN longitudinal imaging mode. Micro-Raman spectroscopy has been also used to measure the stress profile into the silicon wafer around the circular TSV under Laser illumination by monitoring the wavelength shift of the Raman peak.