Ribbon Growth on Substrate (RGS) silicon wafers are casted directly from the silicon melt onto reusable substrates. Material losses by wafer sawing are omitted and high production speeds can be achieved. However, multicrystalline RGS silicon as it is produced today incorporates high densities of crystal defects and impurities limiting the efficiency of the corresponding solar cells. The local impact of crystal defects on material quality is estimated via models developed by Donolato and Micard et al.. By theoretically negating the impact of grain boundaries and dislocations, charge carrier diffusion lengths are still limited to values o 100 mm. In addition to crystal defects which are common in other multicrystalline silicon materials, we found current collecting structures within grain boundaries. These structures can be associated with carbon and oxygen precipitation and are the cause for shunting phenomena. We conclude that high impurity concentrations are the dominant factor for limiting the performance of RGS silicon solar cells.

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As the semiconductor industry further shrinks feature sizes, new analytical solutions are required for elemental composition analysis. Conventional EDX analysis is limited by the obtainable energy resolution. In order to analyze extremely small impurity particles, material doping, interdiffusion effects or small chip structures, the diameter of the area hit by an electron beam and particularly the volume of electron-surface interaction has to be reduced accordingly. This can be achieved by reducing the electron beam energy.X-ray spectroscopy is most frequently used for damage free material testing. Nowadays, semiconductor based energy dispersive X-ray spectrometers (EDS) are employed on a routine basis and are frequently used in combination with scanning electron microscopes (SEMs). But performance is limited by their rather poor energy resolution, which is typically in the 130eV range for a 6keV X-ray line, and their limited capability of resolving X-ray lines within short spectral ranges. Further, overlaps of spectral lines are most critical in the low energy range.