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The understanding of the behavior of arsenic in highly doped near surface silicon layers is of crucial importance for the formation of N-type ultrashallow junctions in current and future very large scale integrated technology. This is of particular relevance when studying recently developed implantation and annealing methods. Past theoretical as well as experimental investigations have suggested that the increase in As concentration, and therefore the reciprocal proximity of several As atoms, leads to a drastic increase in electrically inactive defects giving only marginal reduction in sheet resistance. Monoclinic SiAs aggregates as well as various arsenic-vacancy clusters contribute to the deactivation of arsenic. This study aims to correlate between the results of electrical activation measurements and x-ray absorption fine structure measurements. Samples were doped with a nominal fluence of 1×1015–3×1015 atoms/cm2, implanted at 2 keV, and annealed by rapid thermal treatments, laser submelt treatments, and a combination of both. Hall effect and sheet resistance measurements have been performed to obtain the density of charge carriers. Secondary ion mass spectrometry has been employed to measure the depth profile and the total retained fluences. The percentage of substitutional arsenic has been obtained by least-squares fits of the measured x-ray absorption spectra with simulated spectra of relaxed structures of the defects obtained by density functional theory. A good agreement with the Hall effect measured electrically active dose fraction has been obtained and a quantification of the population of the different defects involved has been attempted. [ABSTRACT FROM AUTHOR]

Boron marker-layer structures have been used to analyze the evolution of boron-interstitial clusters (BICs) formed during transient enhanced diffusion. Our approach is based on the measure of B activation by spreading resistance profiling after annealing of Si implantation damage. We investigated a wide range of implant conditions in terms of defect densities below and above the amorphization threshold of Si. We found a common behavior of BICs in terms of trapping and release processes of B atoms. The BICs density as a function of time for different concentration ratios of I and B has been determined. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Boron ultralow energy (0.2–3 keV) high dose (1×1015 cm-2) implants in single crystalline Si (100) were characterized by secondary ion mass spectrometry using an ultralow energy (0.35–0.5 keV) O2+ ion primary beam and collecting positive secondary ions. In particular, the not fully oxidizing approaches (primary beam oblique incidence and ultrahigh vacuum analysis atmosphere) were investigated because they are expected to provide better accuracy on the profile shape, especially in the region between the surface and the native oxide/substrate interface. The main drawback represented by an early formation of roughness on the crater bottom has been overcome by combining the ion sputtering with the rotation of the sample during the analysis. The reduced formation of roughness ensures more stable sputtering conditions and a more stable erosion rate with a more accurate depth calibration. The measured dose values were then cross-checked comparing them with results of soft x-ray synchrotron radiation grazing incidence x-ray fluorescence. [ABSTRACT FROM AUTHOR]