Theoretical and experimental Raman spectroscopy study of mechanical stress induced by electronic packaging

The mechanical stress induced in Si chips by the packaging process (effect of die attach, flip chip bumping, etc.) is measured by micro-Raman spectroscopy. The measurements are performed on the [110] cross-section surface of the polished samples. This study shows that the current Raman formula for top-surface measurements cannot be used for cross-section measurements due to the anisotropic property of Si. The new formula for cross-section measurements is introduced in this paper. The experimental results are compared to finite element simulations. The Raman results correlate very well with the FE calculations. It shows that micro-Raman spectroscopy is a very interesting technique to study packaging induced stress in Si chips and to validate finite element calculations.