INVESTIGATION OF THE ELASTIC-MODULUS OF THIN-FILMS USING SIMPLE BIAXIAL BENDING TECHNIQUES

The increasing use of thin films in numerous applications has raised t he interest in the mechanical behavior of thin films; particularly the hardness and thr elastic modulus of these films. The aim of the prese nt study is to evaluate a simple biaxial bending technique to measure the elastic modulus of films with thicknesses ranging from 0.1 to 2 mu m. In this range, it can be difficult to use simple indentation techn iques owing to the influence of the substrate, and in order to determi ne the performance of these systems it is often essential to be able t o determine the elastic modulus unambiguously. Tests have been carried out on glass substrates, and magnetron sputtered metal films (copper and aluminium) have been deposited on glass discs to evaluate the film properties. The samples were loaded in biaxial flexure using a paint load on the disc supported by three point supports. The bending appara tus uses a commercially available micromechanical probe (UMIS 2000) th at enables the measurement of very low loads and small displacements. Comparison is made between the force-displacement response of the disc with and without the sputtered film. Analysis of the bending response gave values of the elastic modulus for the glass discs of E = 54.7 +/ - 0.4 GPa, while E = 116 +/- 8 Cpa for the copper films and E = 84 +/- 5 Cpa for the aluminium films. (C) 1997 Elsevier Science S.A.