Study of the effect of grain boundary migration on hillock formation in Althin films

We have studied the effect of grain boundary migration on hillock formation in unpassivated Al thin films during thermal cycling. Hillocking occurs mo re frequently in Al films that experience grain growth during thermal cycli ng than in films with stabilized grain structures. The hillocking frequency is at least four times greater in the films that experience grain growth, as judged by the number of hillocks observed per initial grain boundary tri ple junction. This latter measure takes account of the smaller initial grai n size in the film that experiences grain growth and shows that grain bound ary migration itself must enhance the hillocking frequency. (C) 2001 Americ an Institute of Physics.