Inline Characterization of Diamond Wire Sawn Multicrystalline Silicon Wafers

While for monocrystalline silicon ingot slicing diamond wire sawing processes are widely used, the general approach for slicing multicrystalline bricks has been based on slurry wire processes. Driven by a strong decrease in wafer prices recently, wafer manufacturers of multicrystalline materials switched rather quickly to the diamond-cut process, although several severe technological challenges were to be faced. Unfortunately, sawing is more difficult and an adaptation of solar cell production is essential for texturing processes considering diamond-cut wafer surface morphology. Also characterization methodologies must be adapted to these new material properties. Especially saw mark inspection and thickness topology measurements are key aspects of developments. General imaging methods also need to be evaluated for defect detection and wafer rating purpose. In this paper, an overview of inline characterization methods and their applicability on diamond-cut wafers will be given. Five out of eight methods need hardware or software adjustments to work on diamond-cut wafers. Special attention is paid to the photoluminescence analysis which allows a forecast of solar cell parameters if the relevant defect features are correctly extracted from the images. Due to the increased optical artifacts, this is not a trivial task.