A model for power law creep controlled hillock growth

A model for power law creep controlled hillock growth is developed. We first develop closed form solutions for the growth of a hillock and the corresponding stress relaxation in a film using a power law creep constitutive law that includes a threshold stress for creep. This general model is then adapted to describe hillocking in aluminum films by including the effect of power law breakdown and using an incremental solution technique. The model is used to predict hillock growth and the corresponding stress relaxation kinetics in aluminum thin films, and the results are compared to the predictions of Chaudhariʹs diffusion controlled model. Chaudhariʹs model predicts that hillocks in aluminum will rapidly grow to large, empirically unaccountable volumes, whereas the power law model can be made to match the experiments with a suitable choice of the threshold stress.