Formation and annealing of defects during high-temperature processing of ion-implanted epitaxial silicon: the role of dopant implants

We have investigated the optical and structural characteristics of defect evolution during high-temperature annealing of keV-ion-implanted epitaxial silicon using optical microscopy (OM), photoluminescence (PL) spectroscopy and transmission electron microscopy (TEM). Postimplantation annealing in oxygen ambient resulted in oxidation-induced stacking faults (OISFs) and dislocations. The PL spectrum of these samples is dominated primarily by a dislocation-related D1 line, which is particularly strong in Al-implanted samples as a consequence of the enhanced formation of dislocations with Al implantation. Comparative analysis of the PL signature and OM observations of defects for different implants suggests that D1 and D2 lines result from dislocations rather than in the OISFs. Indeed, it is found that OISFs act as a nonradiative recombination channel in the luminescence of Si. PL studies of N2-annealed samples indicate the formation of nonradiative defect centres. In the case of dopant implants, after rapid thermal annealing (RTA) for 2 min in N2 ambient, the specific signature of extended defects was found from PL studies, while TEM analysis reveals the presence of <111> precipitates located in a region with a high dislocation density. In comparison with other dopants, Al implants show an enhanced formation of extended defects, and they are found even at a depth beyond the end-of-ion range damage.