Microstructure formation in electrochemically deposited Copper thin films

Abstract

The influence of the electrochemical potential and deposition mode on the preferred orientation, morphology and microstructure of crystallites in electrochemically deposited (BCD) copper thin films was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and the diffraction of back-scattered electrons (EBSD). As a working electrode for the BCD process, thin gold layers were employed that were deposited on floating-glass substrates in a vacuum evaporation process. With increasing negative electrochemical potential in the BCD process, the deposition mode changed from the charge transfer controlled one to the diffusion controlled one. At the highest electro-chemical potentials, the copper deposition and the hydrogen release were running concurrently. The change of the deposition mode was accompanied by a change of the surface roughness of the thin films and by a change of the direction and degree of the preferred orientation of crystallites. The surface roughness of the deposited copper thin films increased with increasing electrochemical potential. Compact plate-like crystallites with the preferred orientation {111} grew in the transport controlled deposition mode. Development of the {111} texture was supported by the {111} preferred orientation of the gold layers and by surface energy of copper, which is the lowest in the (111) plane. The diffusion controlled deposition mode was characterized by the growth of globular {110}oriented crystallites. The {110} texture resulted from the minimization of the anisotropic strain energy of copper via reduction of the structure defects in this deposition modus. For highest electrochemical potentials, the copper deposition run simultaneously with the development of hydrogen that resulted in growth of needle-like crystallites with the {100} texture. © 2007 WILEY-VCH Verlag GmbH & Co. KGaA.