Damage behavior of Cu-Ta bilayered films under cyclic loading

Damage behavior of Cu-Ta bilayered films bonded to polyimide (PI) substrates has been investigated by cyclic loading tests. Experimental results show that fatigue cracks preferentially initiated in the Ta layer close to the Ta-PI interface and propagated into the Cu layer perpendicular to the interface. The alignment of nanometer-sized Cu grains resulted from the potential GB sliding combined with a small amount of grain rotation was found in the damage zone ahead of the crack tip, and that is suggested to be a likely damage mechanism to accommodate cyclic plastic strain ahead of the fatigue crack tip of the submicrometer-thick Cu layer. © 2007 Materials Research Society.