A quantitative method of metal impurities depth profiling for gettering evaluation in silicon wafers

A quantitative method of metal impurities depth profiling in silicon wafers has been developed by applying wet-chemical preparation of silicon and determination of metal impurities in solution by graphite furnace atomic absorption spectroscopy (GF-AAS). Three different methodologies of sample preparation are used: Drop etching (DE) for surface oxide etching, drop sandwich etching (DSE) for near surface silicon bulk etching and bulk decomposition (ED) for total silicon bulk dissolution. By applying this concept, the redistribution of Fe in p- and n-type silicon wafers is analyzed after intentional contamination by spin-coating and annealing in N-2 ambient at 900 degrees C. Similar depth profiles are found for Fe in p and n-type silicon wafers. No loss of Fe by evaporation is observed in p-and n-type wafers. The method is applied to gettering evaluation of metal impurities in internal gettering (IG), external gettering (EG), p/p(+) epi and SIMOX wafers.