HILLOCK GROWTH ON ALUMINUM AND ALUMINUM-ALLOY FILMS

The size distributions of hillocks formed on Al and Al alloy films were measured and related to their growth mechanisms. The compositions of these films were as follows: pure Al, Al-1.7wt.%Cu, Al-7.6wt.%Cu, Al-15wt.%Cu, and Al-1.7wt.%Cu- < 1wt.%Si. They were formed under a variety of experimental conditions. In almost all cases the hillock size distributions were log-normal, which, in analogy with the nucleation and growth of thin films, is the distribution that would be expected for hillock growth by mobility coalescence. In the case of the Al-15wt.%Cu films, which were isothermally annealed in vacuum at 300-degrees-C, the distributions gradually changed from log-normal initially to one that had some of the characteristics of Ostwald ripening.