This paper reports the influence of carbon coimplantation on the redistribution of phosphorus implanted in preamorphized Si. A strong influence of the carbon location, with respect to the P profile, is evidenced. With the help of specific simulations, a model is proposed to explain this dependence. It is shown that, in optimized conditions, it is possible to achieve P profiles suitable for the thin junctions required for future device generations.
Carbon co-implantation after pre-amorphization implantation (PAI) has been studied for Boron shallow implants and can be also used to reduce Phosphorus diffusion. The expected role of Carbon is to trap Si interstitials responsible of Phosphorus diffusion. A known drawback of this kind of co-implantation is junction leakage caused by Carbon deep levels. To find a compromise between diffusion reduction and leakages, it is necessary to optimize the location and the amount of Carbon with respect to Si interstitials.In this work, we present full sheet experiments optimizing Carbon implanted energy and dose in order to minimize Phosphorus diffusion. First, we performed a PAI with Germanium. Then Carbon was implanted at several energies and doses to locate its projected range (Rp) at various locations with respect to the Phosphorus peak and the amorphous/crystalline interface. Finally the Phosphorus implant was placed completely within the amorphized area. Dopants were activated by a spike anneal at 1080°C, 1055°C or 1000°C. SIMS analysis and Rs measurements were used to understand Carbon action on Phosphorus diffusion and activation. The role of C in suppressing P diffusion is discussed in regards of the specificities of P diffusion mechanism.
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