AVS 49th International Symposium
    Thin Films Tuesday Sessions
       Session TF-TuM

Invited Paper TF-TuM2
Mechanical Testing of Thin Films: Experiments and Analysis

Tuesday, November 5, 2002, 8:40 am, Room C-101

Session: Mechanical Properties of Thin Films
Presenter: O. Kraft, Forschungszentrum Karlsruhe, Germany
Authors: O. Kraft, Forschungszentrum Karlsruhe, Germany
R. Schwaiger, Massachusetts Institute of Technology
Correspondent: Click to Email
Several specialized testing techniques have been developed to study the mechanical behavior of thin films, including thermal cycling experiments, micro-tensile testing, bulge testing, nanoindentation, and microbeam deflection. They are specifically aimed at determining material properties such as Young's modulus, yield strength, strain hardening rate, ultimate tensile or fracture strength of thin film materials. For these techniques, however, the required sample geometry, loading and straining conditions can be quite different, and as a result, comparisons between the different techniques are not straightforward. This is illustrated in this paper by studying the deformation behavior of sputter-deposited Cu films with thicknesses between 200 and 1500 nm by considering results from several techniques. In particular, nanoindentation and microbeam deflection experiments on identical samples will be compared which were both analyzed by using finite element modeling. The main difference between the two techniques is that the plastic strain is less than 1 % during a bending experiment while it is about 8 % during indentation. It will be shown that it is not possible to describe the stress-strain behavior of the films over this wide range of plastic strains by the use of a simple bi-linear material law. Nevertheless, both techniques show that during deformation of thin metal films strong strain hardening effects are present.