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Synchrotron X-Ray Topography has been used in Total Reflection Topography (TRT) mode to observe strain induced surface bumps due to the presence of underlying misfit dislocations in strained layer SiGe on Si epitaxial heterostructures. In these experiments the x-rays approached the sample surfaces at grazing incident angles below the total external reflection critical angles for a number of reflections and hence surface strain features nominally less than a few tens of Ångstroms from the sample surface have been observed. These are similar to the surface bumpiness observed by Atomic Force Microscopy, albeit on a much larger lateral length scale. The fact that TRT mode images were taken was confirmed by the observation of clear and conventional back reflection topographic images of misfit dislocations in all samples when the grazing incidence angle became greater than the critical angle. [ABSTRACT FROM AUTHOR]

Synchrotron X-ray topographs of epitaxial laterally overgrown GaAs (ELO) samples are made in both transmission and reflection geometries. Samples grown on GaAs substrates with separated and merged ELO layers are studied. Transmission, transmission section, back-reflection, back reflection section and grazing incidence X-ray topographs are compared. The topographs, complementary to each other, show that the bending of the ELO layers is visible in all geometries, though ELO images are seen in different ways in different geometries. The observed contrast of the ELO layers is explained using a model based on orientational image contrast. A pair of back-reflection section and back-reflection topographs taken subsequently from the same position is required for successful and unambigious interpretation of topographs. [ABSTRACT FROM AUTHOR]

Reflection topographs of annealed Czochralski-grown silicon wafers are made with synchrotron white beam radiation at grazing angles of 0.2 degree to 3 degree. Information on the uniformity of the denuded zone is obtained from a number of grazing incidence topographs, which according to calculations turn out to be almost completely monochromatic having a negligible harmonic content. The calculated penetration depth ranges from 1 to 100 µm depending on the grazing angle and reflection used. The grazing incidence topographs are compared with section topographs of the same samples. [ABSTRACT FROM AUTHOR]

White beam synchrotron x-ray topography (WBSXRT) is a non-destructive technique, which is capable of analysing the strain and/or dislocation distribution in single crystal materials. This paper discusses the application of WBSXRT to the analysis of strain fields due to the microelectronic packaging of integrated circuits. A ball grid array package containing an Intel® Pentium® III microprocessor was employed to investigate the spatial extent of strain fields imposed on the underlying silicon substrate due to the reflow process for lead–tin solder bumps. Large area and section back-reflection SXRT images were taken before and after the reflow process at 350°C in atmosphere. The effects of strain imposed by the overlying bump structures in these x-ray topographs have been observed principally via orientational contrast. This was also the situation after the reflow process due to severe stresses in the underlying silicon beneath the lead bumps. The estimated magnitudes of shear stress, |τxy|, imposed on the underlying silicon were calculated to be of the order of 100 MPa. A simulation of the orientational contrast at the edge of bump was performed based on the kinematical theory of x-ray diffraction (Rantamäki R et al 1999 J. Appl. Phys.86 4298). The degree of lattice distortion is well fitted to the topographs of the post-reflow sample. The spatial strain in the underlying silicon was relieved dramatically after the lead bumps were removed from the wafer, which confirms that the solder bump formation is indeed a major source of strain in the underlying Si. Finite element modelling was performed in two-dimensional plane strain mode. The magnitudes and spatial distribution of the stresses after the reflow process are in good agreement with the SXRT results. [ABSTRACT FROM AUTHOR]