Finite element modeling of microscale thermal residual stresses in Al interconnects

An elastic-plastic crystalline constitutive model implemented in a finite-e lement code has been used to predict the microscale thermal residual stress es in Al-1%Si-0.5%Cu interconnects. This fully three-dimensional model acco unts for the individual grain orientations in these interconnects, as measu red by orientation imaging microscopy. The influence of specific crystal or ientations on the residual stress distribution in these interconnects was s tudied in detail. A sensitivity analysis was performed to identify the para meters that influence strongly the predicted values of the residual stresse s and their distributions. For the interconnects studied here, the residual stresses in the metal lines were found to be quite sensitive to the elasti c modulus of the passivation material and its geometry. In addition, the vo lume averages of the predicted stresses were in reasonable agreement with t he experimentally determined values from the x-ray technique.