The effect of oxygen on the electrical activation and diffusion of ion-implanted boron

Transient enhanced diffusion (TED) and electrical activation (EA) of ion-implanted boron during rapid thermal annealing has been investigated using three types of boron doped p-type Si (100) substrates: (a) Ct 20 Omega cm, (b) 3 mu m thick 20 Omega cm epitaxial Si layer (epi-layer) grown on a 20 Omega cm Ct substrate, and (c) 3 mu m thick 20 Omega cm epi-layer grown on a 5 m Omega cm Fz substrate. The level of oxygen is known to decrease from material type (a) to (c). The samples were implanted with 20 keV, 5x10(13) cm(-2) boron and subjected to rapid thermal annealing (RTA) at various temperatures and times. The EA and TED were studied using spreading resistance profiling (SRP) and secondary ion mass spectrometry (SIMS), respectively. Although the amount of TED is almost identical for the three substrates, the EA is found to be significantly higher in the epi-layers compared to Ct substrates. It is speculated that the trapping of vacancies by oxygen in the ion-damaged region leads to an increase in the interstitial supersaturation during annealing, which then results in enhanced boron clustering and reduced electrical activation in the peak of the implanted profile.