Distribution of metal impurities in silicon wafers using imaging-mode multi-elemental laser-induced breakdown spectrometry

Abstract

Laser-induced breakdown spectrometry (LIBS) was used as a procedure for testing the distribution of metal impurities in silicon wafer samples. The method is based on surface and tomographic distribution analysis by monitoring the plasma emission produced by a Nd:YAG pulsed laser operating on the second harmonic wavelength generated from 1064 nm. Non-textured silicon wafers from different manufacturers were used. A total area of 20×20 mm ² was analysed with a lateral resolution of 750 µm and a depth resolution of 0.8 µm. Variables which produced the best plasma emission were optimised. Three dimensional distribution maps of copper, aluminium and calcium impurities in silicon samples were obtained. Significant differences in the distribution of the impurities between samples from different sources were observed.