Self-Interstitials and Substitutional C in Silicon: Interstitial- Trapping and C- Clustering
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Self-interstitials and substitutional C in silicon: Interstitial- trapping and C- clustering S. Mirabella, S. Scalese, A. Terrasi, and F. Priolo INFM and Dept. of Physics and Astronomy, University of Catania, Corso Italia 57, 95129 Catania, Italy A. Coati, D. De Salvador, E. Napolitani, and M. Berti INFM and Dept. of Physics, University of Padova, Via Marzolo 8, 35131 Padova, Italy ABSTRACT The interactions between self-interstitials (I’s) produced by 20 keV silicon implantation, and substitutional carbon in silicon have been studied using a Si1-yCy layer interposed between a near surface I source and a deeper B spike used as a marker for the I concentration. The Si1-yCy layer behaves as a filtering membrane for the interstitials flowing towards the bulk. This trapping ability is related to the total C amount in the Si1-yCy membrane. Substitutional carbon atoms interacting with self-interstitials are shown to trap I’s, to be removed from their substitutional sites, and to precipitate into the C-rich region. After precipitation, C atoms are not able to further trap injected self-interstitials. The atomistic mechanism leading to Si-interstitial trapping has been investigated by developing a simulation code describing the migration of injected interstitials. By a comparison with the experimental data it was possible to derive quantitative indications on the trapping mechanism. It is shown that one Si-interstitial is able to deactivate about two C traps by means of interstitial trapping and C-clustering reactions.
INTRODUCTION The point defects in crystalline silicon, interstitials (I’s) and vacancies, and their interactions with the most commonly used dopants have been attracted great interest in the semiconductor scientific community [1-4]. In fact, changes in the point defects equilibrium populations cause deviations from the equilibrium diffusion coefficients of the dopants and induce anomalous diffusion, such as the well-known transient enhanced diffusion (TED), that have several implications on the advanced microelectronic technology [5-7]. In particular, it has been demonstrated that B diffuses exclusively via an I mediated process [2,8], and thus B can be used as a sensitive tool to measure the I concentration in the different experimental conditions [2,9,10]. On the other hand, C diffusivity has been shown to be I mediated [11] but, differently from B, C appears to be a trap for Si self- interstitials and thus to be able to reduce I concentration [5,12-14]. Recently, the ability of a remote Si1-yCy layer to suppress the TED of B implanted in preamorphized silicon was demonstrated [7]. Moreover, a competition between C diffusion and C clustering under interstitial injection by thermal oxidation has been shown [15]. So, the I trapping by C involves very complex phenomena. In this paper we study the effect of a Si1-yCy layer placed between a deep B spike and a surface implanted region (Si cap layer) on the TED of the deep B spike. Moreover, we characterized the evolution of both the carbon concentration profile a
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