SEM-based system for 100nm x-ray tomography for the analysis of porous silicon

Synchrotron radiation is a good candidate for 3D imaging at high resolution. However, the difficult access to 3rd generation synchrotron sources is prohibitive for daily analyses and we present hereafter a step towards x-ray nanotomography using a laboratory system. To have a lens-free system, we use the electron beam of an SEM to produce x-rays through the interaction between the SEM electron beam and a metallic anode. The inherent x-ray source size can be properly shaped using different anode materials and geometries. This flexible system makes it possible to perform x-ray imaging at energies of up to 10keV and resolution down to 100nm. Because of a low SNR, the exposure time is long and forces to have a low angular sampling. This is counterbalanced by using algebraic reconstruction algorithms. The technique has been applied to the study of plasma FIB-prepared macroporous silicon samples. Those samples come from the controlled porosification of 200mm silicon wafer, with thicknesses from few nm to few hundreds of micrometers. We quantified the 3D pore network, which is of interest for the optimization of the production of such materials.