Arsenic clustering and precipitation analysis in ion-implanted Si wafers by X-ray absorption spectroscopy and SIMS

EXAFS and SIMS have been used to obtain clustering and precipitation information in As (arsenic) implanted Si wafers. CZ(001) Si wafers were first implanted by As at 100 keV to a dose of 1×10 ¹⁵/cm² followed by a second As⁺ implantation at 20-30 keV with doses of 1×10¹⁵/cm² -1×10¹⁸/cm². From the SIMS concentration depth profiles and the corresponding UT-MARLOWE simulations, the region where the As-concentration is above the solid solubility level was determined. The coordination numbers (N) and the nearest-neighbor distances (R) to As atoms in the first shell were extracted from Fourier analysis of the EXAFS data. When arsenic precipitates as monoclinic SiAs, the nearest neighbor distances and coordination numbers are ~2.36 and ~3, as opposed to ~2.40 and ~4 when As is substitutional. Based on this information, the critical implant dose where the precipitation of As starts, and the ratio of the substitutional to precipitate As in the samples was determined