Boron diffusion in amorphous silicon

Venezia, V. C.; Duffy, Ray; Pelaz, Lourdes; Hopstaken, M.; Maas, G.C.J.; Dao, T.; Tamminga, Y.; Graat, P. C. J.

doi:10.1016/j.mseb.2005.08.079

Cited by 28 publications

(32 citation statements)

References 8 publications

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“…30,31 Conversely, theoretical calculations recently showed that the Si self-diffusion in a-Si is enhanced in presence of a high percentage of coordination defects, pointing out that selfdiffusion can be assisted by db or fb. 32 Similarly, B diffusion in a-Si was measured to be larger in the as implanted state than in the relaxed one, 10,11,33 showing peculiar features, such as a transient behavior and a dopant concentration dependence, which will be described in the next paragraph.…”

Section: A Defects and Diffusion In Amorphous Simentioning

confidence: 89%

“…To explain this feature, a diffusion coefficient increasing with the B concentration (n B ) has been suggested. 10 Still, by looking at Fig. 3, for a fixed B concentration (e.g., n B ¼ 1 Â 10 19 B/cm 3 ), one observes a different broadening of the two B boxes, the larger for the higher B concentration box.…”

Section: B Main Features Of B Migrationmentioning

confidence: 93%

“…n c was found to be temperature independent, with a value of about 2.2 Â 10 20 B/cm 3 , again in full agreement with literature indications. 10 The proposed model is able to explain both the peculiar concentration dependence and the transient behavior of B diffusion in a-Si. The concentration dependent diffusion is simulated considering that the higher the B density, the more db are present, promoting a faster B diffusion.…”

Section: Defect Assisted B Diffusionmentioning

confidence: 95%

“…Venezia et al investigated the diffusion of ultra-shallow implanted B in a-Si using a SOI (silicon on insulator) substrate to suppress the SPER and hence to enlarge the range of annealing temperatures and times in the a phase. 10 They evidenced that the B diffusivity in a-Si is a transient phenomenon and it is enhanced at high B concentrations, deviating from the Fick's laws and causing a concentration gradient which is not reduced after diffusion.…”

Section: B Main Features Of B Migrationmentioning

confidence: 99%

“…Both the diffusion and clustering in a-Si cannot be neglected, since they influence the final B profile and its activation in the desired ultrashallow junction. In fact, B diffusivity in a-Si is measured to be more than five orders of magnitude larger than in crystalline Si at the same temperature, 10,11 so, even if the SPER can be completed during the rump-up stage of a flash annealing, boron atoms will experience a non negligible diffusion. B diffusion coefficient (D B ) in a-Si, at the temperature of 650 C and at a concentration level of 1Â10 20 B/cm 3 , can be as high as D B ¼ 7Â10 À14 cm 2 /s, while in c-Si, D B is about 1Â10 À19 cm 2 /s.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: A Defects and Diffusion In Amorphous Simentioning

confidence: 89%

Section: B Main Features Of B Migrationmentioning

confidence: 93%

Section: Defect Assisted B Diffusionmentioning

confidence: 95%

Section: B Main Features Of B Migrationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 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

show abstract

Continuum simulation of solid phase epitaxial regrowth of amorphized silicon including most advanced physical interactions

Delalleau

Pakfar

Bazizi

et al. 2010

Physica Status Solidi (a)

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Solid‐phase‐epitaxial regrowth (SPER) of Si amorphized by ion implantation is considered as a potential solution for the fabrication of highly‐activated ultra‐shallow junctions for future technology nodes of Si CMOS devices. In the frame of 32 and 22 nm technologies node development, SPER occurs after amorphizing implantations used in source/drain regions. To get an accurate simulation of dopant activation and junction depth position, a suitable continuum SPER model, implemented into a commercial simulator, is now mandatory. This TCAD model must consider the different physical effects associated with SPER: silicon regrowth rate, dopants redistribution snow plough effect, and interaction with silicon point defects. In this work, using a previously established model, we have implemented an improved physically based model for SPER and, several formulations have been developed to enable a robust/accurate modeling of the recrystallization velocity. It takes into account the direct interaction between amorphous/crystalline interface kinetics and point defects, and a regrowth rate dependent on temperature. Simulation results of dopant concentration profiles are in good agreement with experimental data and can provide important insight for optimizing the bulk silicon process as well in one dimension as two dimensions.

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Metastable Activation of Dopants by Solid Phase Epitaxial Recrystallisation

Duffy

2014

Subsecond Annealing of Advanced Materials

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Boron diffusion in amorphous silicon

Cited by 28 publications

References 8 publications

Mechanisms of boron diffusion in silicon and germanium

Mechanisms of boron diffusion in silicon and germanium

Continuum simulation of solid phase epitaxial regrowth of amorphized silicon including most advanced physical interactions

Metastable Activation of Dopants by Solid Phase Epitaxial Recrystallisation

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