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Insidious contamination by heavy metals such as iron, nickel, and copper can detrimentally affect the performance of microelectronic devices. 1 Issues of iron contamination have been exhaustively studied in the past, whereas the role of nickel and copper contamination in silicon has not been fully investigated. [2][3][4][5][6][7] The degradation of the gate oxide integrity by nickel is comparable to the breakdown effects due to iron contamination. 8,9 Examination of copper behavior in silicon is becoming more and more important because deliberate copper contamination can limit the yield of high-performance microprocessors with copper interconnects. [10][11][12][13] Tailored gettering sites on the silicon wafer must capture the metallic contamination in order to maintain a lasting contaminationfree active device region. Gettering by redistribution of metallic impurities at high temperatures is called segregation-induced gettering, caused, e.g., by a higher solubility of the metal impurity in the getter region. Relaxation-induced gettering means supersaturation of the silicon wafer with metal impurities and the preferred nucleation of metal silicides at crystal defects such as bulk microdefects (BMDs). 14 From a mechanistic point of view, we consider gettering to be segregation induced when it can be observed to result from higher solubility of the chemically identical metallic impurity in the gettering layer, regardless of the temperature at which the metal's solubility in the gettering layer differs from its solubility in the gettered layer. Even when the solubility difference is a function of the cooling rate, we term this kind of gettering "segregation induced," because the driving force is the difference in chemical potential between the chemically identical, dissolved metal species in the gettering layer and gettered layer, respectively. By the same token, "relaxation-induced gettering" is driven by the reduction of the activation energy of silicide formation at crystal defects. "Relaxation-induced gettering" is the result of the precipitation chemical reactions that are facilitated by defect sites.Wafer manufacturers are very interested in obtaining experimental data on both gettering efficiencies and gettering mechanisms of different gettering sites, such as BMDs, polysilicon back sides, and heavily boron-doped substrate wafers (pϩ). Another motive for investigating gettering mechanisms is the need for computer simulation of the gettering phenomenon. [15][16][17][18][19] Recently, Benton et al. 20 have reported experimental data on and proposed a model for iron gettered by increased iron solubility in heavily boron-doped silicon (pϩ). The increased solubility of iron in pϩ silicon is caused by a Fermi level shift combined with acceptor pairing of Fe ϩ forming Fe ϩ B Ϫ pairs. It is not yet clear whether a similar mechanism operates for copper and nickel, too. However, solubility data for copper in heavily boron-doped silicon suggest that pϩ-gettering may also be applicable to copper. 21-25 p/pϩ epitaxial waf...

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