Laue scanner: A new method for determination of grain orientations and grain boundary types of multicrystalline silicon on a full wafer scale

The grain structure, especially the grain orientation, number and type of grain boundaries, influences many of the properties of multicrystalline (mc) silicon (Si) wafers used for manufacturing solar cells. In order to increase the efficiency of silicon solar cells, the relation between material defects, such as dislocations, impurities and precipitates, and the grain structure must be understood. Currently no measurement system exists that can determine the grain orientation on a full mc Si wafer with an area of 156 x 156 mm(2). The most widely used measuring method is electron backscatter diffraction (EBSD). However, it is only possible to measure small sample sizes by EBSD depending on the scanning electron microscopy stage, and moreover a time-consuming surface preparation is needed. In this paper an innovative fast characterization method is presented that allows the orientation measurement of as-cut and polished Si samples up to 380 x 400 mm2. This method, known as the Laue scanner, is based on X-ray diffraction. Experimental and theoretical considerations, limits of the system and example results of possible tasks are shown and discussed.