Nanomechanical response and creep behavior of electroless deposited copper films under nanoindentation test

The nanomechanical response and creep behavior of electroless plated copper (Cu) films have been investigated in this research by using a nanoindentation test. The hardness and elastic modulus of the nanostructural Cu films with a large amount of small grains in size of only 5 nm were measured as 1.5 and 120 GPa, respectively. The Cu films deformed elastically at first and then yielded at a stress of 3.3 GPa. Grain-boundary sliding and grain rotation were expected to dominate the deformation of the Cu films. The Cu films showed a creep strain rate of about 5 × 10−5 s−1 under the nanoindentation test, and the creep strain rate–stress relation exhibited a typical power law expression with a stress exponent of 6.4. The high creep strain rate but low stress exponent of the Cu films implied a fixed creep behavior consisting of grain-boundary sliding and grain rotation by the fast diffusion of Cu atoms through the large amount of grain-boundary.