Laser-induced breakdown spectroscopy for photovoltaic silicon wafer analysis

ABSTRACT The principal subject matter of this work is the application of laser‐induced breakdown spectroscopy for the multi‐elemental analytical characterization of different qualities of solid silicon. The physical process upon which the technique is based is the temporally resolved observation of emission spectra emitted by a micro‐plasma generated by a laser focused on the surface of a given sample. The optimal environmental parameters such as the composition of the buffering gas for the identification and measurement of several metallic, non‐metallic, and dopant impurities were determined. Particular attention was given to boron. A detection limit of 2.10−4 mg/g of boron was found using a calibration curve, which was made in the range of 1 to 100 ppmw. Silicon samples from different production techniques (4C and directional solidification), which permit the segregation of different impurities along the length of the silicon ingot were analyzed using laser‐induced breakdown spectroscopy. Copyright © 2011 John Wiley & Sons, Ltd. Laser‐induced breakdown spectroscopy is used for multi‐elemental analysis of silicon. The method was optimized as regards environmental parameters such as the composition of buffering gas and was used for measurement of several different impurities including boron, for which a detection limit of 0.2 ppmw was found by constructing a calibration curve in the range of 1 to 100 ppmw. Silicon samples from different production techniques (4C and directional solidification) were analyzed as a function of the length of the silicon.