ANALYSIS OF LOW-ENERGY BORON IMPLANTS IN SILICON THROUGH SIO2-FILMS -IMPLANTATION DAMAGE AND ANOMALOUS DIFFUSION

The experimental investigation reported in this paper focuses on the e ffect of induced implantation damage on the boron diffusion process. B oron is implanted at various fluences and energies in Cz-(100) silicon through different oxide layer thicknesses. Rapid thermal annealing (R TA) is used to activate shallow p(+) layers (0.1-0.15 mu m) following boron implantation. Concentrations versus depth boron profiles are mea sured using a secondary ion mass spectrometry (SIMS) analyser. An enha nced boron diffusion is detected in the tail region when the oxide thi ckness decreases. If the concentration peak is located at the oxide/si licon interface or in the substrate, further implantation damage is ge nerated. This observed enhanced boron diffusion is thus attributed to the implantation-induced damage. The point defects, which act as a dri ving force for this enhanced boron diffusion at different annealing st ages, are detected by the deep level transient spectroscopy (DLTS) tec hnique. In particular, the effect of knocked-on oxygen during the impl antation step on the generation of deep centres and defects is investi gated. Finally, all the results reveal that DLTS coupled to SIMS analy sis provides an efficient method with which to identify the origin and the nature of implanted and RTA related defects.