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

Laser-induced breakdown spectrometry (LIBS) was used as a procedure for tes ting the distribution of metal impurities in silicon wafer samples. The met hod is based on surface and tomographic distribution analysis by monitoring the plasma emission produced by a Nd:YAG pulsed laser operating on the sec ond harmonic wavelength generated from 1064 nm. Non-textured silicon wafers from different manufacturers were used. A total area of 20 x 20 mm(2) was analysed with a lateral; resolution of 750 mu m and a depth resolution of 0 .8 mu m. Variables which produced the best plasma emission were optimised. Three dimensional distribution maps of copper, aluminium and calcium impuri ties in silicon samples were obtained. Significant differences in the distr ibution of the impurities between samples from different sources were obser ved.