Impurity detection in solid and molten silicon by laser induced breakdown spectroscopy

The application of Laser Induced Breakdown Spectroscopy (LIBS) for the analysis of both solid and molten silicon has been developed. This technique provides fast and reliable chemical characterization of silicon. This work will present the investigation of experimental parameters such as buffering gas nature and pressure in order to find the most suitable conditions to quantify boron in solid silicon. These results show that the signal to background ratio (SBR) is improved by both the use of helium and argon instead of air and by reducing the pressure to 500 mbar. Using calibrated samples, calibration curves were prepared for boron and limits of detection of the order of 0.2 ppm were obtained working at a distance of 50 cm from the sample. Additionally, the capabilities of LIBS to analyze molten silicon (1410 °C) was demonstrated, opening the way for LIBS to be used as a process analytical technique.