Development of scanning x-ray fluorescence microscope with spatial resolution of 30nm using Kirkpatrick-Baez mirror optics

We developed a high-spatial-resolution scanning x-ray fluorescence microscope (SXFM) using Kirkpatrick-Baez mirrors. As a result of two-dimensional focusing tests at BL29XUL of SPring-8, the full width at half maximum of the focused beam was achieved to be 50×30nm2 (V×H) under the best focusing conditions. The measured beam profiles were in good agreement with simulated results. Moreover, beam size was controllable within the wide range of 30–1400nm by changing the virtual source size, although photon flux and size were in a trade-off relationship. To demonstrate SXFM performance, a fine test chart fabricated using focused ion beam system was observed to determine the best spatial resolution. The element distribution inside a logo mark of SPring-8 in the test chart, which has a minimum linewidth of approximately 50–60nm, was visualized with a spatial resolution better than 30nm using the smallest focused x-ray beam.