The linkage between macroscopic gettering mechanisms and electronic configuration of 3d-elements in p/p plus epitaxial silicon wafers

We have measured the gettering efficiencies for Cr, Mn, Fe, Co, Ni and Cu i n p/p+ epitaxial wafers. The Bettering test started with a reproducible spi n-on contamination on the front side of the wafers in the 10(12)-10(14) ato ms/cm(2) range, followed by thermal treatment to redistribute the metallic impurities in the wafer. The gettering efficiencies were measured by a nove l wet chemical stratigraphic etching technique in combination with inductiv ely-coupled plasma mass spectrometry. The residual bulk metal contamination was also measured by this method. This procedure led to global distributio ns of the 3d elements on the wafer's front side, in the bulk of the wafer a nd on the wafer's back side. Recovery rates were found to be 34%, 2.3%, 100 %, 85%, 100% and 100% for Cr, Mn, Fe, Co, Ni and Cu, respectively. An impur ity segregation effect in the wafer bulk was measured for Cu (100%) and Cr (34%), while no detectable segregation-induced gettering mechanisms were de tected for the other elements in the applied concentration range. The segre gation-induced gettering mechanisms were interpreted from the electronic st ructure of the metallic impurities. For segregation gettering by increased solubility in p+ silicon, the metallic species must form donors. Only Cu+ ( 3d(10)) and Cr+ (3d(5)) can form singly positively charged species that exh ibit a spherical electronic distribution. It is well known from spinell str uctures that 3d(10) and, to a smaller extent 3d5, are stable configurations in tetrahedral structures like the silicon lattice. Thus, we link the segr egation-induced gettering mechanism in p/p+ epitaxial wafer to the electron ic configuration of the 3d elements.