Shallow junctions by high-dose As implants in Si: experiments and modeling

Tsai, M. Y.; Morehead, F. F.; Baglin, J. E. E.; Michel, A. E.

doi:10.1063/1.328078

Cited by 173 publications

(55 citation statements)

References 11 publications

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“…The definite nature of the conclusion contrasts with results from other techniques. Varied mechanisms have been suggested to explain the primary cause for deactivation, including the following: the formation of small As clusters, 18 the formation of As precipitates, 19 the creation of structural defects working as traps, 20 and the migration of As from substitutional to interstitial sites. 21,22 Although the substitutional nature of deactivated As impurities is not longer under discussion, 23,24 the details of the responsible defect are still under debate.…”

Section: A Extraction Of the Position Of Deactivated Arsenicmentioning

confidence: 99%

Lattice compression of Si crystals and crystallographic position of As impurities measured with x-ray standing wave spectroscopy

Herrera-Gómez

Rousseau

Woicik

et al. 1999

Journal of Applied Physics

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In an earlier letter [Appl. Phys. Lett. 68, 3090 (1996)] we reported results about heavily arsenic doped silicon crystals, where we unambiguously showed, based on x-ray standing wave spectroscopy (XSW) and other techniques, that electrically deactivated As remains essentially substitutional. In this article we present the analysis methodology that led us to said conclusion, and show how from further analysis it is possible to extract the compression or expansion of thin epitaxial layers. We report the evolution of the compression of highly As doped Si epitaxial layers as deactivation takes place. The XSW measurements required a very small thickness of the doped layer and a perfect registry between the substrate and the surface layer. We found larger values for compression than previously reported, which may be explained by the absence of structural defects on our samples that relax the interface stress. Our results show a saturation on the compression as the electron concentration increases. We also report an estimation of the small displacement from perfect substitutional positions suffered by deactivated As.

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Section: A Extraction Of the Position Of Deactivated Arsenicmentioning

confidence: 99%

Lattice compression of Si crystals and crystallographic position of As impurities measured with x-ray standing wave spectroscopy

Herrera-Gómez

Rousseau

Woicik

et al. 1999

Journal of Applied Physics

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“…Most of these authors suggest the formation of complex point defects or clusters in thermal equilibrium with the As in solution (1)(2)(3)(4)(5)(6). The existence of arsenic clusters, however, is presently not more than a hypothesis.…”

mentioning

confidence: 99%

Electron Microscopy of As Supersaturated Silicon

Armigliato¹,

Nobili²,

Solmi³

et al. 1986

J. Electrochem. Soc.

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Silicon specimens have been implanted with 1 • 1016 and 5 • 1016 As + ions/cm 2 and annealed with a pulsed ruby laser, thus giving rise to a supersaturated solution. Subsequent heat-treatments carried out in an inert ambient at either 450 ~ or 900~ led to a strong deactivation of the dopant. The physical nature of the inactive arsenic has been investigated by transmission electron microscopy (TEM), both in the weak beam and the high resolution imaging modes. For both doses and annealing temperatures, the presence of precipitates, having a diameter ranging from 1.5 to 3 nm, has been observed. Other defects, such as dislocations, perfect and faulted loops, and rod-like defects have also been detected in our TEM investigations. Despite the high density of the detected precipitates, the corresponding amount of arsenic atoms, as deduced by assuming an SiAs composition, can account for only a fraction of the inactive dopant. A possible explanation is that particles in the subnanometer range are invisible even in the high resolution images. This hypothesis is supported by the absence of contrast found in corresponding simulated high resolution images.Arsenic, due to the high solubility and low diffusivity, is the silicon n-type dopant more commonly used in VLSI circuits, both for the source and drain of MOS transistors and the emitter of bipolar transistors.Several works performed in recent years have investigated the physical nature of electrically inactive As, which is present in silicon at high doping levels. Most of these authors suggest the formation of complex point defects or clusters in thermal equilibrium with the As in solution (1-6). The existence of arsenic clusters, however, is presently not more than a hypothesis. Chu and Masters (7), from-angle-scanned channeling studies, reported results that are compatible with cluster formation, but there is not, up to now, direct evidence of the arsenic clusters.Recent work (8, 9) performed on ion-implanted and laser-annealed silicon, doped with As in a wide range of compositions, provided evidence that the electrically active concentration depends only on temperature, a finding leading to the conclusion that a two-phase equilibrium takes place. The formation of a second phase was also indicated by the isochronal heating behavior, showing a reverse annealing typical of a precipitation process (8). Precipitates were, in fact, detected by small angle x-ray scattering (SAXS), a technique that is suitable because of the noticeably different atomic numbers of Si and As. These determinations provided information on the size distribution and shape of these precipitates that was found to be in agreement with the classical theory of nucleation, which predicts a decrease in particle density and an increase in particle size as the supersaturation decreases (9). Moreover, most of these particles should be coherent with the silicon matrix, as expected from the RBS experiments performed in channeling conditions (7, 10), showing that the off-axis concentration is markedly lower than...

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“…Finally, an automatic time selection scheme is used to reduce At during periods of rapid clustering or declustering in order to improve tracking of the active and clustered fractions. Figure 7 compares the above model and experimental profiles [14] measured after implanting arsenic at 140 keV through 0.025 ^m of SiOj at 2 X 10 ions/cm and then annealing at 1000°C for 20 min and at 800°C for 60 min. Note that the total profile is essentially unchanged during the 800°C step but that the active fraction decreases due to clustering.…”

Section: Aik)c^(k -H) = R -H A^k) + A(k%^jk + 1)mentioning

confidence: 96%

“…The equations involved in the .model [14] can be written Equations (6) must be solved subject to boundary and initial conditions. The most general boundary conditions used in silicon, which cover evaporation, predeposition, epitaxy, and reflecting boundaries, are…”

Section: Arsenic Kinetic Modelmentioning

confidence: 99%