A laser plasma X-ray source for the analysis of wafer surfaces by grazing emission X-ray fluorescence spectrometry

A wavelength-dispersive X-ray fluorescence spectrometer incorporating a novel X-ray source with which X-rays are generated by means of light pulses from a powerful femtosecond laser is described. The instrument has been designed in order to explore whether laser-induced X-rays can replace conventional X-ray sources in the examination of wafer surfaces for traces of contaminant elements by X-ray fluorescence spectrometry. The laser plasma source developed employs as target an ultra-thin (10–20 μm) silicon foil situated parallel to and a few mm above the wafer surface to be analyzed. The Si-K α radiation emitted from the laser plasma cloud produced on the surface of the target as a result of the interaction of the femtosecond laser pulse with the silicon foil is used for the excitation of aluminium atoms on the surface of the sample wafer.