Gettering efficiencies for Cu and Ni as a function of size and density of oxygen precipitates in p/p- silicon epitaxial wafers

We have measured the gettering efficiencies for Cu and Ni in plp-Si epitaxi al wafers. The wafers were pretreated to obtain oxygen precipitates of diff erent sizes and densities in the bulk. Gettering tests started with a repro ducible spin-on spiking in the range of 10(12) atoms/cm(2), followed by the rmal treatment to drive-in and redistribute the impurities in the wafer. Su bsequently, the wafers were analyzed by a novel stratigraphical layer-by-la yer etching technique in combination with inductively coupled plasma mass s pectrometry. Gettering efficiencies for Ni did not depend on oxygen precipi tate sizes and densities as long as DeltaO(i) was larger than 0.2 x 10(17) atoms/cm(3) and the bulk micro defect densities were detectable by preferen tial etching (10(7) cm(-3)). In these cases, gettering efficiencies were 96 %-99% for Ni, while wafers not containing any measurable BMDs exhibited no detectable gettering. Cu exhibited a more complex behavior because the tota l Cu contamination was found to be divided into two species, one mobile and the other immobile species. A dependence on BMD size and BMD density of th e Cu distributions in the wafers was also detected. Gettering effects were increased with increasing BMD densities and sizes. For BMD densities < 10(9 ) cm(-3), Cu was not efficiently gettered by oxygen precipitates. Even for BMD densities > 10(10) to cm(-3), gettering effects due to oxygen precipita tes were one order of magnitude lower than in heavily boron-doped silicon.