Vapour phase decomposition (VPD) is a method used in the semiconductor industry to improve the sensitivity of total-reflection x-ray fluorescence spectroscopy by changing the contaminant from a thin layer (which has an angle-dependent fluorescence intensity in the TXRF-domain) to a granular residue.
In standard atomic absorption spectroscopy (AAS), the impurity is dissolved together with the matrix element.
The method has yielded good results for the detection and measurement of nickel and iron.
To improve the range of elemental impurities and lower detection limits, the acid droplets obtained from the silicon wafers are analyzed by ICP-MS (Inductively coupled plasma mass spectrometry).
This technique, VPD ICP-MS provides accurate measurement of up to 60 elements and detection limits of in the range of 1E6-E10 atoms/sq.cm on the silicon wafer.