Self-annealing and aging effect characterization on copper seed thin films

Self-annealing and seed-aging effects are probably among the most important topics of recent investigations on the microstructural changes in copper thin films and of their effects on electrical and optical properties. Aim of this work is the characterization of self-annealing and seed-aging effects together with their possible correlation. The combined analysis of resistivity and reffectivity of seed layer samples is also compared with X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and atomic force microscopy (AFM) results. Copper seed characterization of self-annealing effect evidences that mean grain size increase with time does not impact film resistivity only: surface roughness shows a 40% increase after 200 h from film deposition and the (111) preferential orientation of the copper crystallites parallel to the surface becomes more pronounced. Seed-aging effect study underlines a dependency of the optical reffectivity on surface chemical contamination, whereas it does not seem affected by the evolution of surface roughness. Copper oxidation in air is due to the formation of a bi-layer of Cu2O and Cu(OH)(2), the latter showing a weak stability under high vacuum environment. Vacuum annealed samples present a significant increase in reflectivity values, which is maintained even after many hours from copper seed deposition. (c) 2005 Elsevier B.V. All rights reserved.