Complete Suppression of the Transient Enhanced Diffusion of B Implanted in Preamorphized Si by Interstitial Trapping in
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Complete Suppression of the Transient Enhanced Diffusion of B Implanted in Preamorphized Si by Interstitial Trapping in a Spatially Separated C-Rich Layer E. Napolitani1, A. Coati1, D. De Salvador1, A. Carnera1, S. Mirabella2, S. Scalese2, F. Priolo2 1 INFM and Dipartimento di Fisica, via Marzolo 8, 35131 Padova, ITALY. 2 INFM and Dipartimento di Fisica e Astronomia, Corso Italia 57, 95129 Catania, ITALY. ABSTRACT A method for completely suppressing the transient enhanced diffusion (TED) of boron implanted in preamorphized silicon is demonstrated. Boron is implanted in a molecular beam epitaxy (MBE) grown silicon sample that has been previously amorphized by silicon implantation. The sample is then annealed in order to epitaxially regrow the amorphous layer and electrically activate the dopant. The back-flow of silicon interstitials released by the preamorphization end-of-range (EOR) damage is completely trapped by a carbon-rich silicon layer interposed by MBE between the damage and the implanted boron. No appreciable TED is observed in the samples up to complete dissolution of the EOR damage, and complete electrical activation is obtained. The method might be considered for the realization of ultra shallow junctions for the far future complementary metal-oxide semiconductor technology nodes.
INTRODUCTION The realization of ultra shallow junctions for the future complementary metal-oxide semiconductor (CMOS) technology nodes [1] is extremely challenging for the ion implantation community, as well as for researchers involved in point defect-dopant interactions in silicon. In fact, even by implanting the dopant extremely close to the surface, i.e. by reducing the implant energy well below 1 keV, the broadening, produced during the post-implantation activation annealing by the transient enhanced diffusion (TED) [2,3], still severely hinders the application of the above processes to the most aggressive CMOS device scaling rules. Several attempts have been made to control and reduce the TED of boron in silicon. Implantation in preamorphized silicon is one of the most studied and promising methods, due to the advantage of suppressing dopant channeling and the capability of the end-of-range (EOR) defects (mainly dislocation loops) to trap the excess interstitials left by the preamorphization implant. However, since the dislocation size and density critically depend on the implant and annealing conditions, interstitial trapping and, consequently, TED suppression not always occur [4, 5], and in most cases an increase of enhanced diffusion is even observed due to the release of interstitials from EOR defects dissolution [4]. Substitutional C incorporation in Si is another promising method for reducing TED, due to its high efficiency in trapping the silicon I, as reported by Stolk et al. [6]. However, there are several studies reporting the detrimental effect on the electrical properties of the material due to the presence of carbon [7,8]. Therefore, even if C is effective in reducing TED, a method for TED suppression involvi
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