The effect of Ag-alloying on the microstructural and thermo-mechanical properties of electrochemically deposited Cu thin films was investigated using the focused ion beam technique, scanning electron microscopy and the electron back scatter diffraction (EBSD) technique as well as the substrate curvature method to study their stress-temperature and stress relaxation behavior. The results show that the linear elastic behavior of 1 mu m thick Cu films is significantly improved by alloying. Additionally, after annealing such films have an excellent low electrical resistivity of 1.9-2.0 mu Omega cm, which meets the requirements of the roadmap ITRS [International Technology Roadmap for Semiconductors, Edition 2003, part: interconnect, available at http://public.itrs.net/]. (c) 2005 Elsevier B.V. All rights reserved.