Cyclic deformation of polycrystalline Cu films
- 1 January 2003
- journal article
- research article
- Published by Informa UK Limited in Philosophical Magazine
- Vol. 83 (6), 693-710
- https://doi.org/10.1080/0141861021000056690
Abstract
Fatigue impairs the reliability of macroscopic metallic components utilized in a variety of technological applications. However, the fatigue behaviour of thin metal films and small-scale components used in microelectronics and mechanical microdevices has yet to be explored in detail. The fatigue behaviour in submicrometre thin films is likely to differ from that in bulk material, since the volume necessary for the formation of dislocation structures typical of cyclic deformation in bulk material is larger than that available in thin films. The thin-film dimensions and microstructure, therefore, affect the microscopic processes responsible for fatigue. The fatigue behaviour of Cu films 0.4, 0.8 and 3.0 µm thick on polyimide substrates was investigated. The specimens were fatigued at a total strain amplitude of 0.5% using an electromechanical tensile-testing machine. This work focuses on the characterization of fatigue mechanisms and the resulting fatigue damage of thin Cu films. Extrusions similar to those observed in bulk material were found at the film surfaces after cyclic loading. Voids observed beneath the extrusions, close to the film-substrate interface, contributed significantly to thin-film failure. Thinner films were more fatigue resistant and contained fewer and smaller extrusions than thicker films did. A small thickness appears to inhibit void nucleation. This observation is explained in terms of vacancy diffusion and annihilation at free surfaces or grain boundaries. Transmission electron microscopy investigations confirmed that no long-range dislocation structures have developed during fatigue loading of the films investigated.Keywords
This publication has 38 references indexed in Scilit:
- Crack-like grain-boundary diffusion wedges in thin metal filmsActa Materialia, 1999
- A review of focused ion beam milling techniques for TEM specimen preparationMicron, 1999
- Fundamental aspects of low amplitude cyclic deformation in face-centred cubic crystalsProgress in Materials Science, 1992
- The dependence of dislocation microstructure on plastic strain amplitude in cyclically strained copper single crystalsActa Metallurgica, 1984
- A model of extrusions and intrusions in fatigued metals I. Point-defect production and the growth of extrusionsPhilosophical Magazine A, 1981
- The temperature dependence of the saturation stress and dislocation substructure in fatigued copper single crystalsActa Metallurgica, 1980
- Vacancy dipoles in fatigued copperPhilosophical Magazine, 1976
- Weak-beam study of dislocation structures in fatigued copperPhilosophical Magazine, 1976
- Strain localization in cyclic deformation of copper single crystalsPhilosophical Magazine, 1975
- Cyclic stress-strain response of F.C.C. metals and alloys—II Dislocation structures and mechanismsActa Metallurgica, 1967