Plasma immersion ion implantation for impurity gettering in silicon

The authors have utilized plasma immersion ion implantation (PIII) to demonstrate effective gettering of metallic impurities in silicon wafers. Metallic impurities such as Ni, Cu or Au were intentionally diffused into Si as marker impurities. The Ar or Ne atoms were ionized in an electron cyclotron resonance (ECR) plasma chamber. The ions were accelerated by a negative voltage applied to the wafer and implanted into the wafer. The as-implanted saturation dose can be as high as 5 x 1016 cm-2. After an annealing step at 1000 degree C for 1 hour in a N2 ambient, the retained doses and the amount of gettered impurities were measured with Rutherford backscattering spectrometry (RBS). With a retained Ar dose in 1015 cm-2 range after annealing, the gettered Ni, Cu and Au were 3.0 x 1014 cm-2, 3.0 x 1014 cm-2 and 4.4 x 1013 cm-2 respectively. 5 refs., 4 figs., 1 tab