Physical insight into the phenomenon of B clustering in Si at room temperature

The interaction between the crystal defects and the implanted dopants in Si is at the origin of the diffusion and the electrical de-activation that are detrimental for the realization of the ultra-shallow junctions required by the semiconductor technology roadmap. In this contest, the B clustering phenomenon under non-equilibrium conditions is of particular interest for the scientific community.It has been shown that ion channeling technique is an extremely powerful tool to reveal the room temperature formation of small boron-interstitial-clusters (BICs) through the detection of subnanometric B off-lattice displacement.In this paper, we review our recent results on BIC formation in B-doped Si samples on a large range of B concentration (1019–1021 at/cm3). At room temperature B atoms undergo an off-lattice displacement, with a characteristic channeling mark, if a supersaturation of Si self-interstitials (Is) is maintained by ion irradiation. The B displacement rate is limited by the fluence of excess Is per B atom and can be reproduced using a simple model of B–Is interaction with the formation of small B clusters. In the early stage of Is injection the formation of B2I clusters with the structure of split (1 0 0) has been detected by performing channeling angular scans along the <1 0 0> and <1 1 0> crystal axes.