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 effect of induced implantation damage on the boron diffusion process. Boron is implanted at various fluences and energies in Cz-(100) silicon through different oxide layer thicknesses. Rapid thermal annealing (RTA) is used to activate shallow p(+) layers (0.1-0.15 mu m) following boron implantation. Concentrations versus depth boron profiles are measured using a secondary ion mass spectrometry (SIMS) analyser. An enhanced boron diffusion is detected in the tail region when the oxide thickness decreases. If the concentration peak is located at the oxide/silicon interface or in the substrate, further implantation damage is generated. This observed enhanced boron diffusion is thus attributed to the implantation-induced damage. The point defects, which act as a driving force for this enhanced boron diffusion at different annealing stages, are detected by the deep level transient spectroscopy (DLTS) technique. In particular, the effect of knocked-on oxygen during the implantation step on the generation of deep centres and defects is investigated. Finally, all the results reveal that DLTS coupled to SIMS analysis provides an efficient method with which to identify the origin and the nature of implanted and RTA related defects.