Atomistic Mechanism of Boron Diffusion in Silicon

Salvador, D. De; Napolitani, E.; Mirabella, S.; Bisognin, G.; Impellizzeri, G.; Carnera, A.; Priolo, F.

doi:10.1103/physrevlett.97.255902

Cited by 31 publications

(35 citation statements)

References 25 publications

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“…In this scenario B, that is the most used p-type dopant in Ge as in Si, seems to show a quite anomalous behavior in Ge. The dominance of interstitials in the B diffusion in Si is well established from different studies [1,7], and this behavior is confirmed also for B in Si-Ge alloys up to 20% Ge contents [8]. In spite of this, there are only a few studies on B diffusion in pure Ge.…”

Section: Introductionsupporting

confidence: 54%

Role of point defects on B diffusion in Ge

Scapellato¹,

Bruno²,

Priolo³

2012

Materials Science in Semiconductor Processing

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Section: Introductionsupporting

confidence: 54%

Role of point defects on B diffusion in Ge

Scapellato¹,

Bruno²,

Priolo³

2012

Materials Science in Semiconductor Processing

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“…In order to quantitatively study the self-interstitial supersaturation, we fitted the B profiles by means of a χ 2 optimization of numerical simulations based on the g-λ diffusion model, 20,24,36 successfully applied also for B diffusion in Ge. 16,19 Here, g gives the B-self-interstitial interaction rate leading to one B diffusion event, while λ is the mean length of 43 and 44)], but the equilibrium self-interstitial density in Si is much larger than in Ge, weakening the effect of self-interstitial injection during OED in Si.…”

Section: Resultsmentioning

confidence: 99%

“…19. SIMS analyses were used to measure B diffusion, whose simulation based on the model of Cowern et al 20,24,36 allows evidence of changes of self-interstitial density in Ge. 3,16,19,37 Figure 3 shows the B profiles of the MBE-Ge after implantation (dashed line) and after annealing at 650…”

Section: Resultsmentioning

confidence: 99%

“…3,19 Therefore, B diffusion is a valuable indirect marker for self-interstitials in Ge, as previously studied in Si with a well-established methodology. [20][21][22][23][24] By using B diffusion, proton irradiation in Ge has been proved to increase the PD density above the equilibrium, leading to a significant radiation enhanced diffusion (RED) of B.…”

Section: Introductionmentioning

confidence: 99%

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Self-interstitials injection in crystalline Ge induced by GeO2nanoclusters

et al. 2011

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The effect of O implantation in crystalline Ge on the density of native point defects has been investigated through transmission electron microscopy and B diffusion experiments. Annealing at 650• C following O implants produces a band of defects (∼5-10 nm), compatible with GeO 2 nanoclusters (NCs). A clear shape transformation from elongated to spherical forms occurs within 2 h, concomitant with a transient enhanced diffusion of B. A large injection of self-interstitials from GeO 2 NCs, giving a vacancy undersaturation, and a long-range migration of self-interstitials are evidenced and discussed.

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“…66 First, boron profiling with secondary ion mass spectrometry (SIMS) has been developed with high accuracy and sensitivity. The improvement of the technique consisted in cooling the samples at À70 C, in order to suppress the long-range anomalous diffusion of B occurring at room temperature during the analysis and thus distorting the profiles, 67 and in flooding the samples with oxygen during the analysis, for enhancing the measurement sensitivity by a factor of 20.…”

Section: B Atomistic Pathways Of B Diffusionmentioning

confidence: 99%

Mechanisms of boron diffusion in silicon and germanium

Mirabella

Salvador

Napolitani

et al. 2013

Journal of Applied Physics

104

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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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Atomistic Mechanism of Boron Diffusion in Silicon

Cited by 31 publications

References 25 publications

Role of point defects on B diffusion in Ge

Role of point defects on B diffusion in Ge

Self-interstitials injection in crystalline Ge induced by GeO2nanoclusters

Mechanisms of boron diffusion in silicon and germanium

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