μ-Raman Spectroscopy and FE-Analysis of thermo-mechanical Stresses in TSV Periphery

In this paper the thermo-mechanical behavior of Through Silicon Vias (TSVs) is in the center of interest. Therefore a Finite Element model was developed, which calculates emerging stresses and strains in TSV periphery during annealing. For validation of the simulation results mu-Raman measurements on according test samples were carried out. Samples underwent annealing at 250 degrees C for 2 h. Warpage and Raman shifts were measured subsequently. Because of the complex stress distribution in TSV periphery a linear relation between stress and Raman shift cannot be presumed. For this reason an evaluation routine is introduced, that enables comparison of Raman measurements and simulation. Thereby, not only the calculation of Raman shifts out of FE data is executed. Further physical effects like penetration depth and laser spot size are taken into account. This procedure enables to move from the evaluation of single node results to a constrained section containing the laser excited region. In summary our paper succeeds in developing a new evaluation algorithm for the transformation of calculated mechanical strains in TSV periphery into Raman shifts. First comparisons of measurements and FE-results deliver much better fitting of data.