Vapour phase decomposition
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Vapour phase decomposition (VPD) is a method used in the semiconductor industry to improve the sensitivity of atomic absorption spectroscopy (AAS) in order to detect metal impurities of very small concentrations on wafer surfaces.
This can be achieved by enhancing the impurity concentration in the solution to be analyzed. In standard AAS, the impurity is dissolved together with the matrix element. In VPD, the surface of the wafer is exposed to hydrofluoric acid vapour, which causes the surface oxide to dissolve together with the impurity metals. The acid droplets, condensed on the surface, are then analyzed using AAS.
The method has yielded good results for the detection and measurement of nickel and iron.
