Effects of Crystallographic Orientation on Film Morphological Evolution

The factors that determine the thermal strains, stresses and plastic yielding during the annealing of deposited Al thin films on Si substrates are reviewed. The effect of film texture orientation on dislocation glide is described and is shown to lead to variations in film strain energy with texture orientation. The strain energy difference between adjacent grains of different texture is proposed to account for several morphological changes during film annealing. If grain boundaries are mobile (i.e., with small initial diameter) film stresses and strain energies may induce the (secondary) growth of weakly oriented (110), (112), etc., grains at the expense of the normally favored (111) strongly oriented grains. If grain boundaries are stagnant, the strain energy differences between grains may induce the hillock growth of weakly oriented (110) grains in order to reduce film compressive stresses, and may also induce the depletion “sinking” of strongly oriented (111) grains in order to relieve film tensile stresses. This model generally accounts for these experimental findings of others.