B cluster formation and dissolution in Si: A scenario based on atomistic modeling

Abstract

A comprehensive model of the nucleation, growth, and dissolution of B clusters in Si is presented. We analyze the activation of B in implanted Si on the basis of detailed interactions between B and defects in Si. In the model, the nucleation of B clusters requires a high interstitial supersaturation, which occurs in the damaged region during implantation and at the early stages of the postimplant anneal. B clusters grow by adding interstitial B to preexisting B clusters, resulting in B complexes with a high interstitial content. As the annealing proceeds and the Si interstitial supersaturation decreases, the B clusters emit Si interstitials, leaving small stable B complexes with low interstitial content. The total dissolution of B clusters involves thermally generated Si interstitials, and it is only achieved at very high temperatures or long anneal times.

Mechanisms of boron diffusion in silicon and germanium

“…15), implanted with Si ions, allowed to develop an atomistic simulation for B-I clustering and diffusion, disentangling the B doping from the implantation damage. 79,80 In the upper panel of Fig. 15, the chemical profiles of B delta doped layers are plotted before and after implantation and annealing, evidencing both the diffusion and the clustering caused by implantation.…”

“…Basing on these results, it was argued that BICs: (i) form only in the region of high B concentration and high I supersaturation during implantation (as calculated from the MARLOWE code 79 ), (ii) nucleate starting from an immobile precursor (BI 2 ) during implantation or at the very early stages of annealing, (iii) are of small size, with less than six atoms (so well below the transmission electron microscopy (TEM) detection limit), (iv) their thermal evolution proceeds via the emission of self-interstitials first and then B interstitials, up to the cluster dissolution. 80 Several studies approached the phenomenon of B-I clustering in crystalline Si from a theoretical point of view, calculating the formation energy and structure of each plausible B-I cluster, the energetically favored B:Si stoichiometry, the possible pathways for BIC growth and dissolution and the interactions with I-type defects. [81][82][83][84][85][86][87][88][89] Most calculations provide such properties for small sized BICs (typically less than 10 atoms) and for a fixed structure or composition, while it cannot be excluded that an ensemble of different BICs size occurs in facts.…”

Below-band-gap electroluminescence related to doping spikes in boron-implanted siliconpndiodes

“…Following the model which was proposed by Pelaz et al, 28,29 boron clustering occurs at the very early stage of annealing when the supersaturation of silicon interstitials is very high in ion implanted silicon. 30,31 Boron gathering during the nucleation of the extended defects was also observed by Bonafos and Xia et al 16,17 The preformed B clusters grow by adding interstitial boron in the presence of a high boron concentration, resulting in boron complexes with a high interstitial content.…”

Formation of hydrogen-boron complexes in boron-doped silicon treated with a high concentration of hydrogen atoms

“…The formation of B clusters in highly B-doped Si is a well-known phenomenon. [24][25][26] The characteristics of the B clusters formed by B implantation are as follows. It is known from resistivity and SIMS measurements that B clusters are formed in the case of a doping level of approximately 10 19 cm −3 or more.…”