Modulating individual thickness for optimized combination of strength and ductility in Cu/Ru multilayer films

The effect of individual thickness on the mechanical properties of Cu/Ru multilayer films deposited onto flexible substrate was investigated by uniaxial tension tests. It is found that both strength and ductility of the Cu/Ru multilayer films are remarkably dependent on the individual thickness. An optimized combination of strength and ductility is obtained when the individual thickness is 20nm. The strengthening mechanism changes from the confined layer slip of single dislocations to the load-bearing effect and the individual thickness dependent ductility is due to the competition between the stress intensity factor in Ru layers and the plasticity deformation in Cu layers. •The strength and ductility of Cu/Ru multilayers depend on individual thickness (h).•An optimized combination of strength and ductility is obtained when h is 20nm.•This finding may play an important role in the working stability of MEMS.