Copper gettering by aluminum precipitates in aluminum-implanted silicon

Copper in Si is shown to be strongly gettered by Al-rich precipitates forme d by implanting Al to supersaturation and then annealing. At temperatures r anging from 600 to 800 degreesC a layer containing Al precipitates is found to getter Cu from Cu silicide located on the opposite side of a 0.25 mm Si wafer, indicating a substantially lower chemical potential for the Cu in t he molten-Al phase. Cu gettering proceeds rapidly until an atomic ratio of approximately 2 Cu atoms to 1 Al atom is reached in the precipitated Al reg ion, after which the gettering process slows down. Redistribution of Cu fro m one Al-rich layer to another at low Cu concentrations demonstrates that a segregation-type gettering mechanism is operating. Cu gettering occurs pri marily in the region containing the precipitated Al rather than in the regi on where the Al is entirely substitutional. (C) 2001 American Institute of Physics.