DETERMINATION OF TRACE-METALS ON A SILICO N-WAFER BY ACID DISSOLUTIONAND GRAPHITE-FURNACE AAS

A simple and rapid method was developed for sampling metals such as Na , Al, Ca, Cr, Fe, Ni, and Cu on the silicon wafer surface and for dete rmination of these trace metals by graphite furnace AAS. Whereas a poo r recovery was obtained for copper when using only HF as the dissolvin g reagent, a mixture of 0.1wt% HF and 1wt% H2O2 was found to oxidize t he silicon and dissolve the copper to improve the recovery to nearly 1 00%. It is important to keep the silicon dioxide thickness greater tha n ca. 0.1 nm by controlling such factors as temperature and concentrat ion of HF and H2O2 However, the sensitivity of aluminum was decreased by interference from hydrofluoric acid. It was improved by drying in t he presence of magnesium as an effective modifier. For a 6 inch wafer, this method is easily applicable to the determination of 10(9) simila r to 10(10) atoms/cm(2) for metals.