Effect of heating ramp rates on transient enhanced diffusion in ion-implanted silicon

Boron marker-layer structures have been used to analyze the heating ramp-rate dependence of transient enhanced dopant diffusion (TED) during rapid thermal annealing of Si implantation damage. The study uses short anneals with heating ramp rates in the range 0.1-350 degreesC/s, and peak temperatures in the range 900-1100 degreesC. Increasing the ramp rate is found to reduce the amount of profile broadening caused by TED, as well as reducing the smaller amount of normal "thermal-equilibrium" diffusion which is related to thermal budget. The results show why high ramp rates lead to improved B-implant activation and junction-depth control in Si devices. An Ostwald ripening model of interstitial-cluster evolution describes the detailed trends in the data and predicts further improvements in the case of ultrarapid annealing.