Depth‐selective elemental imaging of microSD card by confocal micro XRF analysis

A semiconductor device, a microSD card, was measured by using two XRF instruments. 2D elemental images were obtained using a micro‐XRF system with a spatial resolution of 10 µm. Elemental distributions of the near‐surface region of the sample were clearly shown. Titanium was observed in the resin constituting the sample. Nickel and gold were observed on a terminal and localization of the sample. Elemental distribution of copper reflected the circuit structure of the measurement area that was in the neighborhood of the sample surface. Moreover, the elemental depth distributions of the sample were measured by using a confocal micro‐XRF instrument. The confocal micro‐XRF instrument was constructed in the laboratory with fine‐focus polycapillary x‐ray optics. The depth resolution of the developed spectrometer was 13.7 µm at an energy of Au Lβ (11.4 keV). The elemental images obtained at near‐surface by confocal micro‐XRF were the same as the results obtained from 2D micro‐XRF. However, different Cu images were obtained at a depth of several tens of micrometers. This indicates that microSD cards consist of a few different Cu‐circuit structure designs. The elemental depth distributions of each circuit structure of the semiconductor device were clearly shown by confocal micro‐XRF. Copyright © 2013 John Wiley & Sons, Ltd.