Laser ablation/ionization technique for trace element analysis

The laser ablation/ionization technique combined with a reflectron time-of-flight mass spectrometer was used for detection of trace elements in industry-made semiconductor samples of Si and GaAs. A sample atomization was carried out by a 10-ns Q-snaitched Nd:YAG laser operated at a wavelength of 1064 nm. The ablated atoms were ionized by a two-color (1+1) REMPI technique. An abundance level of several ppb was determined for a number of elements (B, Al, Fe, Cr). The overall detection efficiency of the instrument was found to be 10 -4 . The layer-by-layer analysis of Si sample doped with 10 -6 As was accomplished by a frequency-doubled 10-ns Nd:YAG laser for sample ablation and a KrF ercimer laser for ionization of ablated neutral species