Influence of boron-interstitials clusters on hole mobility degradation in high dose boron-implanted ultrashallow junctions

Séverac, Fabrice; Cristiano, Fuccio; Bedel-Pereira, Eléna; Fazzini, Pier Francesco; Boucher, Jonathan; Lerch, W.; Hamm, Silke

doi:10.1063/1.3446844

Cited by 8 publications

(12 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…1, boron chemical profiles are shown for preamorphized Si implanted with 0.5 keV, 1Â10 15 B þ /cm 2 . 6 Significant differences both in the diffused profiles and in the B activation levels were evidenced, due to the interplay with the concomitant thermal evolution of the extended defects created by the PAI and of the clustered B. In fact, for the higher temperature anneals, B profiles show a clear immobile peak (indicated by the arrows) due to B precipitation, not visible at 750 C because of the low B diffusivity.…”

Section: Introductionmentioning

confidence: 99%

“…In fact, for the higher temperature anneals, B profiles show a clear immobile peak (indicated by the arrows) due to B precipitation, not visible at 750 C because of the low B diffusivity. 6 For low thermal budget, a less effective defect dissolution occurs, determining a lower Is density and, as a consequence, a lower boron broadening. The spike or flash anneal gives out a broader final boron profile since larger Is emission from extended defects occurs as well as the concomitant B clusters dissolution.…”

Section: Introductionmentioning

confidence: 99%

“…On the other hand, B clusters significantly act as independent scattering centers, lowering the hole mobility down to $40% of its theoretical value. 6 It should be noted that in such extreme conditions, many phenomena actually occur, which heavily affect the diffusion and the electrical activation of boron atoms and, finally, influence the achievement of ultra-shallow and custom-shaped junctions. In order to allow simulation software tools managing the complexity of this last process, a continuous upgrading is needed in the comprehension of the physics underlying all these phenomena, among which the B diffusion and clustering, at very high dopant concentrations, in amorphous Si or in crystalline Si, and, recently, also in Ge lattices.…”

Section: Introductionmentioning

confidence: 99%

“…[6][7][8][9] Under such extreme conditions, the diffusion of B occurs with features that need to be detailed and modeled. Just to appreciate the effect of some post-implantation annealing recipes (750 C-15 min, 1000 C spike, and 1300 C single or multiple flash anneals), in Fig.…”

Section: Introductionmentioning

confidence: 99%

“…11 In addition, it was clearly demonstrated that B de-activation is partly due to the dopant clustering in the amorphous phase prior to the completion of the SPER process. 6,12,13 Thus, B migration and precipitation in a-Si need to be detailed, for a complete description of B diffusion.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Mechanisms of boron diffusion in silicon and germanium

Mirabella

Salvador

Napolitani

et al. 2013

Journal of Applied Physics

104

View full text Add to dashboard Cite

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...

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%