Effect of Micro Texture of Electroplated Copper Thin Films on Their Mechanical Properties

Abstract

The mechanical properties of copper thin films formed by electroplating were compared with cold-rolled copper films using tensile test and nano-indentation. Both the Young's modulus and tensile strength of the films were found to vary drastically depending on the microstructure of the films. Though the Young's modulus of the cold-rolled film was almost same as that of bulk material, that of the electroplated thin film was about a fourth of that of bulk material. The microstructure of the electroplated film was polycrystalline and a columnar structure with a diameter of a few hundreds-micron and the strength of the grain boundaries of the columnar grains seemed to be rather week. The superplastic deformation was observed in the film due to the cooperative grain boundary sliding. In addition, there was a sharp indentation depth dependence of Young's modulus of the film. There was also a plane distribution of Young's modulus near the surface of the film depending on the distribution of the diameter of the columnar grains.