Impact of N-2 Coimplant on Phosphorus Diffusion and Activation for n/p Ge Junctions

Shallow source/drain (S/D) junctions are crucial for the realization of scaled FETs at advanced CMOS technology nodes. This article demonstrates the suppression of phosphorus (P) diffusion in germanium (Ge) during annealing by coimplantation of nitrogen (N-2). Furthermore, the impact of N-2 implant energy and dose on dopant (P) diffusion is presented. It is shown that dopant diffusion is suppressed with increasing N-2 implant energy and dose. However, the decrease in junction depth comes at the cost of dopant deactivation. An optimized implant condition that provides substantial reduction in junction depth with reasonable dopant activation is demonstrated in this article.