Experiments on atomic-scale mechanisms of diffusion

Cowern, N.E.B.; Walle, G. F. A. van de; Gravesteijn, D.J.; Vriezema, C. J.

doi:10.1103/physrevlett.67.212

Cited by 135 publications

(111 citation statements)

References 4 publications

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“…This fact evidences that the interstitial density enhancement due to oxidation helps the B migration rate, while the inverse reaction, independent of the interstitial density, decreases with temperature because of the energy barrier to the conversion of mobile B into substitutional B. 56 Given the crucial role of Is in B diffusion, any variation of the density of these point-defects (PDs) can heavily affect the B migration. In fact, beyond the surface oxidation, a further and more efficient way to increase the I density is the ion implantation followed by thermal annealing, which produces an Is excess roughly equal to the implanted ion dose ("plus one model" [57][58][59] ).…”

Section: A Milestones On the B Diffusion Mechanismmentioning

confidence: 99%

“…They investigated the migration of B in Si through chemical profiling of a narrow MBE-grown B profile and appropriate modeling based on the interstitial mediated process. 1,56 Within this model, substitutional (immobile) B can be converted (with a frequency rate, g) into a migrating species after a proper interaction with I. Hence, B diffusion occurs thanks to the formation of mobile B, and goes on up to its recombination into substitutional form.…”

Section: A Milestones On the B Diffusion Mechanismmentioning

confidence: 99%

“…Regardless of diffusion conditions, reported data indicate a migration length smaller than 10 nm for temperatures higher than $600 C and a saturation behavior for lower temperatures. In Si, k has a negative activation energy ($À0.6 eV, 14,56 ) as a consequence of the competition between migration and dissociation of the mobile species, thus the migration length reduces by increasing the temperature. In Fig.…”

Section: B Diffusion In C-ge: the Role Of Self-interstitials A Bmentioning

confidence: 99%

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Mechanisms of boron diffusion in silicon and germanium

Mirabella

Salvador

Napolitani

et al. 2013

Journal of Applied Physics

103

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B migration in Si and Ge matrices raised a vast attention because of its inﬂuence on the production of conﬁned, highly p-doped regions, as required by the miniaturization trend. In this scenario, the diffusion of B atoms can take place under severe conditions, often concomitant, such as very large concentration gradients, non-equilibrium point defect density, amorphous-crystalline transition, extrinsic doping level, co-doping, B clusters formation and dissolution, ultra-short high-temperature annealing. In this paper, we review a large amount of experimental work and present our current understanding of the B diffusion mechanism, disentangling concomitant effects and describing the underlying physics. Whatever the matrix, B migration in amorphous (a-) or crystalline (c-) Si, or c-Ge is revealed to be an indirect process, activated by point defects of the hosting medium. In a-Si in the 450-650 C range, B diffusivity is 5 orders of magnitude higher than in c-Si, with a transient longer than the typical amorphous relaxation time. A quick B precipitation is also evidenced for concentrations larger than 2 x10^20 B/cm3. B migration in a-Si occurs with the creation of a metastable mobile B, jumping between adjacent sites, stimulated by dangling bonds of a-Si whose density is enhanced by B itself (larger B density causes higher B diffusivity). Similar activation energies for migration of B atoms (3.0 eV) and of dangling bonds (2.6 eV) have been extracted. In c-Si, B diffusion is largely affected by the Fermi level position, occurring through the interaction between the negatively charged substitutional B and a self-interstitial (I) in the neutral or doubly positively charged state, if under intrinsic or extrinsic (p-type doping) conditions, respectively. After charge exchanges, the migrating, uncharged BI pair is formed. Under high n-type doping conditions, B diffusion occurs also through the negatively charged BI pair, even if the migration is depressed by Coulomb pairing with n-type dopants. The interplay between B clustering and migration is also modeled, since B diffusion is greatly affected by precipitation. Small (below 1 nm) and relatively large (5-10 nm in size) BI clusters have been identiﬁed with different energy barriers for thermal dissolution (3.6 or 4.8 eV, respectively). In c-Ge, B motion is by far less evident than in c-Si, even if the migration mechanism is revealed to be similarly assisted by Is. If Is density is increased well above the equilibrium (as during ion irradiation), B diffusion occurs up to quite large extents and also at relatively low temperatures, disclosing the underlying mechanism. The lower B diffusivity and the larger activation barrier (4.65 eV, rather than 3.45 eV in c-Si) can be explained by the intrinsic shortage of Is in Ge and by their large formation energy. B diffusion can be strongly enhanced with a proper point defect engineering, as achieved with embedded GeO2 nanoclusters, causing at 650 °C a large Is supersaturation. These aspects of B diffusion are presented and discus...

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Section: A Milestones On the B Diffusion Mechanismmentioning

confidence: 99%

Section: A Milestones On the B Diffusion Mechanismmentioning

confidence: 99%

Section: B Diffusion In C-ge: the Role Of Self-interstitials A Bmentioning

confidence: 99%

See 1 more Smart Citation

Mechanisms of boron diffusion in silicon and germanium

Mirabella

Salvador

Napolitani

et al. 2013

Journal of Applied Physics

103

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“…( ) The temperature dependence of Λ using the parameters of table I is displayed in Fig.3, both for intrinsic and doped silicon, and compared with experimental values for almost intrinsic materials [19,21]. With the values we are using, Λ ∝ p/ni for e F ~ ei.…”

Section: Physical Modelsmentioning

confidence: 99%

Physical modeling of Fermi-level effects for decanano device process simulations

Martín-Bragado

Pinacho

Castrillo

et al. 2004

Materials Science and Engineering: B

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We report on a physically-based Fermi-level modeling approach designed to be accurate and yet amenable to be implemented in a device-size process simulator. We use an atomistic kinetic Monte Carlo method in conjunction with a continuum treatment for carrier densities. results. This modeling scheme has proved to be very computationally efficient for realistic device-dimension process simulations. We present an illustrative set of simulation results for two common dopants, Boron and Arsenic, and discuss the potential of this approach for accurate process simulation of decanano CMOS devices. *Electronic address: ignacio.martin@tel.uva.es 1

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“…2 Ion implantation also introduces defects into the crystal which are repaired by annealing at a temperature of about 800°C. Boron diffuses by kick-in and kick-out reactions with silicon interstitials, 3,4 as illustrated in Fig. 1 and diffuses particularly fast during annealing.…”

Section: Introductionmentioning

confidence: 99%

Elastic interaction energy between a silicon interstitial and a carbon substitutional in a silicon crystal

2007

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The strain interaction energy between a silicon interstitial and a carbon substitutional in a silicon crystal was modeled by a continuum Green's function method and by atomistic simulation. The interaction energy is proportional to d −3 , where d is separation distance between the defects. The pair interaction energy was found to be less than 0.04 meV for d Ͼ 6 nm increasing to more than about 0.1 meV for d Ͻ 3 nm. The energies are unlikely to influence the diffusional behavior of the defects except at distances of one or two unit cells. The potential between the point defects is repulsive if they are oriented along the ͑100͒ crystal axis, but attractive if they are positioned along ͑110͒ or ͑111͒.

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Experiments on atomic-scale mechanisms of diffusion

Cited by 135 publications

References 4 publications

Mechanisms of boron diffusion in silicon and germanium

Mechanisms of boron diffusion in silicon and germanium

Physical modeling of Fermi-level effects for decanano device process simulations

Elastic interaction energy between a silicon interstitial and a carbon substitutional in a silicon crystal

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