Laser-induced breakdown spectroscopy for photovoltaic silicon wafer analysis

摘要

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 100ppmw. 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.