Stress evaluation in thin films: Micro-focus synchrotron X-ray diffraction combined with focused ion beam patterning for do evaluation

Conference item

Nanocrystalline metallic coatings of sub-micron thickness are widely used in modern microelectronic applications. In X-ray diffraction experiments to determine both the residual and applied stresses in nanocrystalline coatings, one difficult challenge that comes up invariably is the determination of the strain-free lattice spacing do. The present study addresses this challenge by using the focused ion beam (FIB) to generate a built-in strain-free reference by patterning (milling) a 50 × 50 μm2 region of the coating to produce an array of small stress-relieved "islands" ~ 0.8 × 0.8 μm2 each. Transmission X-ray diffraction setup was used for data collection at DIFFABS beamline (Synchrotron SOLEIL, France). A 150 nm-thick multi-layered W-Cu nano-composite thin film on polyimide (Kapton®) substrate was studied. The samples were loaded incrementally using a compact uniaxial loading device, and micro-beam diffraction data were collected on and away from the reference array. It was shown experimentally that the "island" array remained approximately strain free throughout the experiment, providing an on-board do lattice spacing reference. The changing lattice spacing d in the coating was also monitored away from the array, to deduce the elastic strain evolution during deformation. The results and their implications are presented and discussed. © 2013 Elsevier B.V.

Authors: Baimpas, N; Le Bourhis, E; Eve, S; Thiaudière, D; Hardie, C

• Host title: Thin Solid Films
• Volume: 549
• Pages: 245-250
• Publication date: 2013-12-31
• DOI: 10.1016/j.tsf.2013.07.019
• ISSN: 0040-6090