The Influence of the Initial Supersaturation of Si Interstitial Atoms on the Relative Thermal Stability of Dislocation L
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The Influence of the Initial Supersaturation of Si Interstitial Atoms on the Relative Thermal Stability of Dislocation Loops in Silicon F. Cristiano1, B. Colombeau1, B. de Mauduit1, F. Giles2, M. Omri3 and A. Claverie1 1 CEMES/CNRS, 29 rue J.Marvig, 31055 Toulouse Cedex, France 2 Infineon Technologies, Munich, Germany 3 Faculté des Sciences, Bizerte, Tunisia
ABSTRACT
In this work, we have studied the relative stability of perfect (PDLs) and faulted (FDLs) dislocation loops formed during annealing of preamorphised silicon. In particular, we have investigated the effect of the initial supersaturation of Si interstitial atoms (Si(int)s) created by the implantation process on their thermal evolution. Transmission Electron Microscopy analysis shows that in samples with a low Si interstitial supersaturation, FDLs are the dominant defects while PDLs appear as the most stable defects in highly supersaturated samples. We have calculated the formation energies of both types of dislocation loops and found that, for defects of the same size, FDLs are more energetically stable than PDLs, if their diameter is smaller than 80 nm and viceversa. The application of these calculations to the samples studied in this work indicates that a direct correspondence exists between the formation energy of the two defect families and the number of atoms bound to them. Moreover, we have shown that the relative stability of FDLs and PDLs depends on the initial supersaturation of Si(int)s created during the implantation process.
INTRODUCTION
Dopant diffusion is strongly influenced by the thermal evolution of the various types of extrinsic defects that form when annealing ion implanted silicon [1,2,3]. These defects range from small interstitial clusters to {113} defects [4] and eventually, transform into perfect and/or faulted dislocation loops (PDLs and FDLs, respectively)[5]. During annealing, these defects evolve in size and type through the exchange of Si interstitial atoms (Si(int)). This competitive growth maintains in the defect region a large supersaturation of Si(int)s that acts as a source of point defects for the rest of the wafer. The driving force for this evolution is the reduction of the formation energy of the defects as they grow in size or change their "crystallographical" structure. Their time-evolution reflects the time-dependent decrease of the supersaturation of Si(int) which is at the origin of Transient Enhanced Diffusion (TED) of boron. For this reason, a better knowledge of the thermal behaviour of the different types of defects is needed. The goal of this paper is to study the relative thermal stability of two of the main defects found after high temperature annealing of preamorphised Si wafers, namely the perfect and the faulted dislocations loops. Indeed, a discrepancy emerges from several published studies [6,7] in which, depending on the experimental conditions, FDLs and PDLs are alternatively identified as the most stable defect. In particular, we will study the influence of the initial supersaturation of Si(int
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