B diffusion and clustering in ion implanted Si: The role of B cluster precursors

103

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...

Section: B-i Clusters Formation and Dissolutionmentioning

confidence: 99%

Section: B-i Clusters Formation and Dissolutionmentioning

confidence: 99%

Mechanisms of boron diffusion in silicon and germanium

Mirabella

Salvador

Napolitani

et al. 2013

103

“…Our present interest in this method concerns primarily defects in semiconductors that are produced by low-energy ion implantation. 8,1,9 For this situation, the computation of the scattering intensity is complicated by the presence of the surface and the correlations between the vacancy and interstitial defects.…”

Section: Introductionmentioning

confidence: 99%

Atomistic simulation of diffuse x-ray scattering from defects in solids

Nordlund

Partyka

Averback

et al. 2000

Diffuse x-ray scattering is a powerful means to study the structure of defects in crystalline solids. The traditional analysis of diffuse x-ray scattering experiments relies on analytical and numerical methods which are not well suited for studying complicated defect configurations. We present here an atomistic simulation method by which the diffuse x-ray scattering can be calculated for an arbitrary finite-sized defect in any material where reliable interatomic force models exist. We present results of the method for point defects, defect clusters and dislocations in semiconductors and metals, and show that surface effects on diffuse scattering, which might be important for the investigation of shallow implantation damage, will be negligible in most practical cases. We also compare the results with x-ray experiments on defects in semiconductors to demonstrate how the method can be used to understand complex damage configurations.

“…It is worthy to note that less B diffusion is observed in the shallow B spike ͑initially covered by F͒ than in the deepest one but this also happens for the Si + implant. This behavior could be explained by the temporal immobilization of B due to the formation of BICs in the damaged region of the F + or Si + implants, 9 which reduces the amount of B available for diffusion. The additional damage cascades generated by the F + coimplantation with Si + would favor BIC formation in the shallow B spike, and thus, a reduction in B diffusion.…”

Section: Resultsmentioning

confidence: 99%

Si interstitial contribution of F+ implants in crystalline Si

López

Pelaz

Duffy

et al. 2008

López, Pedro; Pelaz, L.; Duffy, R.; Meunier-Beillard, P.; Roozeboom, F.; Tak, van der, K.; Breimer, P.; Berkum, van, J.G.M.; Verheijen, M.A.; Kaiser, M. Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers)Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication Citation for published version (APA):López, P., Pelaz, L., Duffy, R., Meunier-Beillard, P., Roozeboom, F., Tak, van der, K., ... Kaiser, M. (2008). Si interstitial contribution of F+ implants in crystalline Si. Journal of Applied Physics, 103(9), 093538-1/4. [093538]. DOI: 10.1063/1.2917297 General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. The F effect in crystalline Si is quantified by monitoring defects and B diffusion in samples implanted with 25 keV F + and/or 40 keV Si + . We estimate that about +0.4 Si interstitials are generated per implanted F + ion, in agreement with the value resulting from the net separation of Frenkel pairs. For short annealings, B diffusion is lower when F + is coimplanted with Si + than when only Si + is implanted, while for longer annealings, B diffusion is higher. This is consistent with a lower but longer-lasting Si interstitial supersaturation set by the additional defects generated by the F + implant.