Characterization of elastic moduli of Cu thin films using nanoindentation technique

The elastic moduli in perpendicular and parallel directions to surface of Cu thin film were investigated by nanoindentation test and micro-cantilever beam bending test and the elastic moduli were compared with the theoretical estimations of elastic moduli based on the texture analysis. The thickness of electroplated Cu thin film, characterized by surface profiler, was varied as 3-12 μm with varying the electroplating condition. The specimens for micro-cantilever beam bending test were fabricated by lithography and isotropic etching process. Elastic modulus in perpendicular direction of Cu thin film, measured by nanoindentation test, was obtained as 123-99 GPa and decreased with increasing the film thickness. Elastic modulus in parallel direction of Cu thin film, measured by micro-cantilever beam bending test using nanoindentation technique, was obtained as 121 GPa for 2.8 μm thick Cu thin film and 90 GPa for 10.5 μm thick Cu thin film. Texture of Cu thin film was analyzed from the orientation distribution function calculated from the pole-figures obtained by X-ray diffraction technique. Cu thin film with thickness of 3 μm showed strong 〈1 1 0〉 texture, while 〈1 1 3〉 texture increased with increasing the thickness of Cu thin film. The theoretical estimations of elastic moduli in both perpendicular and parallel directions to surface of Cu thin film based on the texture analysis showed a good agreement with experimental measurements based on the nanoindentation technique.