Finite element modeling of microscale thermal residual stresses in Al interconnects

An elastic-plastic crystalline constitutive model implemented in a finite-element code has been used to predict the microscale thermal residual stresses in Al−1%Si−0.5%Cu interconnects. This fully three-dimensional model accounts for the individual grain orientations in these interconnects, as measured by orientation imaging microscopy. The influence of specific crystal orientations on the residual stress distribution in these interconnects was studied in detail. A sensitivity analysis was performed to identify the parameters that influence strongly the predicted values of the residual stresses and their distributions. For the interconnects studied here, the residual stresses in the metal lines were found to be quite sensitive to the elastic modulus of the passivation material and its geometry. In addition, the volume averages of the predicted stresses were in reasonable agreement with the experimentally determined values from the x-ray technique.