Stress relaxation induced faceted Cu and W particles on the surfaces of Cu-Zr and W thin films

Faceted copper and tungsten particles in submicron-scale were obtained by annealing copper-zirconium thin films on polyimide (PI) substrates as well as in the deposited tungsten films on Si substrates. It was interesting to find that the Cu particles are faceted and seem to be single crystal from their extraordinarily regular appearance. However, it is another case for W particles which are polycrystalline and irregular. Different mechanisms are put forward to elucidate the formation of Cu and W particles according to the morphological characterization, residual stress analysis and their distinct atomic diffusivity.