[en] The measurement of metal impurities on the surface of silicon wafer by Total reflection X-Ray Fluorescence is commonly accepted by the semiconductor industry ISO TC 201 W62 was organized in 1993 as a secretary country in Japan ISO 14706 specified a Total reflection X-Ray Fluorescence method for measurements of metal impurities on the silicon wafer surface with atomic surface density from 1x10¹⁰ atoms/cm² to 1x10¹⁴ atoms/cm² at Dec 2000. In ULSI manufacturing, the measurements for metal impurities of less than 10¹⁰ atoms/cm² are currently required on the silicon wafer of Total reflection X-Ray Fluorescence chemical preparation method (DADD) has been adopted to collected and concentrate metal impurities into a small area on the surface of silicon wafer. In order to certificate the accuracy of quantification of metal impurities in the drying residue that is obtained by chemical preparation method we are going to specify this chemical preparation method. The results of the firsts round robin test RRT) carried out with three experimental conditions depended on each laboratories had pretty big measurement error the second RRT was done under the experimental conditions used with the recovery solution of HF(2%) H₂O₂(2%) and the addition of vanadium of scandium as a internal standard. 20 Laboratories (Japan: 11, US: 3, Europe: 6)gave a combination of the chemical preparation method and Total reflection X-Ray Fluorescence, AAS or ICP-MS results good reproducibility of less than 20 % Cv and repeatability of less than 10 % Cv