Abstract
Coherent x-ray diffraction imaging (CXDI) is becoming an important 3D quantitative microscopy technique, allowing structural investigation of a wide range of delicate mesoscale samples that cannot be imaged by other techniques like electron microscopy. Here we report high-resolution 3D CXDI performed on spherical microcomposites consisting of a polymer core coated with a triple layer of nickel–gold–silica. These composites are of high interest to the microelectronics industry, where they are applied in conducting adhesives as fine-pitch electrical contacts—which requires an exceptional degree of uniformity and reproducibility. Experimental techniques that can assess the state of the composites non-destructively, preferably also while embedded in electronic chips, are thus in high demand. We demonstrate that using CXDI, all four different material components of the composite could be identified, with radii matching well to the nominal specifications of the manufacturer. Moreover, CXDI provided detailed maps of layer thicknesses, roughnesses, and defects such as holes, thus also facilitating cross-layer correlations. The side length of the voxels in the reconstruction, given by the experimental geometry, was 16 nm. The effective resolution enabled resolving even the thinnest coating layer of nominal width. We discuss critically the influence of the weak phase approximation and the projection approximation on the reconstructed electron density estimates, demonstrating that the latter has to be employed. We conclude that CXDI has excellent potential as a metrology tool for microscale composites.
© 2017 Optical Society of America
Full Article | PDF ArticleMore Like This
Henry N. Chapman, Anton Barty, Stefano Marchesini, Aleksandr Noy, Stefan P. Hau-Riege, Congwu Cui, Malcolm R. Howells, Rachel Rosen, Haifeng He, John C. H. Spence, Uwe Weierstall, Tobias Beetz, Chris Jacobsen, and David Shapiro
J. Opt. Soc. Am. A 23(5) 1179-1200 (2006)
S. Marchesini, H. N. Chapman, S. P. Hau-Riege, R. A. London, A. Szoke, H. He, M. R. Howells, H. Padmore, R. Rosen, J. C. H. Spence, and U. Weierstall
Opt. Express 11(19) 2344-2353 (2003)
Eirik Torbjørn Bakken Skjønsfjell, Yuriy Chushkin, Federico Zontone, Nilesh Patil, Alain Gibaud, and Dag W. Breiby
Opt. Express 24(10) 10710-10722 (2016)