Lattice site location of ultra-shallow implanted B in Si using ion beam analysis
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Lattice site location of ultra-shallow implanted B in Si using ion beam analysis Hajime Kobayashi, Ichiro Nomachi, Susumu Kusanagi and Fumitaka Nishiyama* Sony Corporation, Technical Support Center, Yokohama, Japan * Hiroshima University, Department of Applied Physics and Chemistry, Higashi-Hiroshima, Japan
ABSTRACT We have investigated the lattice site location of B in Si using ion channeling in combination with nuclear reaction analysis (NRA). Silicon samples implanted with Boron at an energy of 10 keV and a dose of 5 × 1014 cm-2 (low dose samples) or 5 × 1015 cm-2 (high dose samples) were annealed at 1000 °C for 10 seconds (RTA) or at 800 °C for 10 minutes (FA). The activation efficiencies of these samples were estimated from the B atomic concentration and the hole concentration obtained by secondary ion mass spectrometry (SIMS) and spreading resistance profiling (SRP), respectively. We also studied the ion implantation damage of Si crystals using ion channeling combined with Rutherford backscattering spectrometry (RBS). We found that the activation efficiency is proportional to the substitutionality, meaning that substitutional B is fully activated without any carrier compensation. We also found that B atoms go to the substitutional sites and are activated up to the solubility limit in the high dose samples. However, the ion implantation damage of the crystalline Si in the high dose samples increases somewhat after annealing.
INTRODUCTION In scaling down the dimension of ULSI circuits, a higher concentration of B is required, and the activation efficiency becomes less than unity even below the solubility limit of B in Si [1-3]. Transient enhanced diffusion (TED) studies suggest that some of the boron becomes immobile in highly doped regions, and these B atoms are considered to form B-interstitial Si clusters (B-I clusters) [4,5]. Transmission electron microscopy (TEM) observations suggest that dissolution of {311} defects is a source of excess interstitial Si, which causes both TED and B-I cluster formation [6]. Since these clusters are assumed to be electrically inactive, they cause a decrease in the activation efficiency. The lattice site location of B is important to understand the relationship between the B clustering and the deactivation. However, little is known about the lattice site location of B. So, we have investigated the lattice site location of B using channeling-NRA. SIMS and SRP are used to estimate the activation efficiency. We also studied the ion implantation damage of Si crystals using. In this paper, we demonstrate the relationship between the lattice site location of B in Si and the activation efficiency, and suggest the relationship between the ion implant damage and the post-implant annealing.
EXPERIMENTAL PROCEDURE B ions were implanted into n-type Si(100) substrates at an energy of 10 keV with a dose of 5 × 10 cm-2 (low dose samples) or 5 × 1015 cm-2 (high dose samples). Post-implant anneal were performed at 1000 °C for 10 seconds (RTA) or at 800 °C for 10 minutes (FA). A 10 nm-thick
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