Diffusion of boron in silicon during post-implantation annealing

Solmi, S.; Baruffaldi, Fabio; Canteri, R.

doi:10.1063/1.348740

Cited by 181 publications

(68 citation statements)

References 24 publications

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“…14) typically leads to a peak portion of the B profile, which is electrically inactive and immobile, and a lower part of the profile undergoing TED, with a concentration threshold about one order of magnitude below the B solid solubility. 72,73 Quite soon, it was proposed that the process responsible for the non equilibrium B precipitation through boron-interstitial clusters (BICs) formation was the same responsible for the TED effect, i.e., the I supersaturation. 73 Further confirmation of this came with the evidence that B clustering effectively contributes to lower the I supersaturation following ion implantation.…”

Section: B-i Clusters Formation and Dissolutionmentioning

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: B-i Clusters Formation and Dissolutionmentioning

confidence: 99%

“…[60][61][62]72 In the following, a concise selection of the numerous papers dedicated to this phenomenon will be presented, with the aim to elucidate the main issues which could affect the B diffusion.…”

Section: B-i Clusters Formation and Dissolutionmentioning

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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“…The calculations have been compared to several experiments including the ones from Solmi [4] and Cowern [6]. Fig.…”

Section: Comparison With Experimentsmentioning

confidence: 99%

“…There is no amorphization, however it is known that extended defects can appear as well as activation levels greater than the solubility limit (Csol) [4]. The modeling…”

Section: Initial Conditionsmentioning

confidence: 99%

Modeling High Concentration Boron Diffusion with Dynamic Clustering: Influence of the Initial Conditions

Baccus¹,

Vandenbossche²

1993

Simulation of Semiconductor Devices and Processes

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Boron diffusion and activation at high concentrations are key problems in the formation of shallow P+ junctions. Therefore, it is needed to understand and to predict accuratly the dopant behaviour under these conditions. In this paper, the modeling of boron is discussed, by the use of a non-equilibrium pointdefect model, including amorphization and a dynamic clustering component. The initial conditions are of major importance not only for the transient enhanced diffusion, but also for the amount of active dopant. As a result, it is possible to obtain activation levels greater than the solubility limit, as observed experimentally. The point-defect diffusion modelA non-equilibrium point defect-model has been used throughout the study. It solves rigorously the interactions between dopants and point-defects (including charged species) and takes into account the ion implantation damage. Five coupled equations are needed to solve the diffusion of boron : substitutional boron Bs, interstitial boron Bi, interstitial I, vacancy V, and Poisson equation [I]. In this frame, the simplest modeling of a boron cluster is given by : B s + B i tt B sBi , where the cluster is considered as immobile and in nonequilibrium. Such cluster has been already proposed in a static form [2] or a dynamic one [3] as chosen here. This adds a sixth equation to the system. It is possible to include clusters containing more atoms, but it does not give a significant improvement. Initial conditionsIn the case of high-dose boron ion implantation, it is difficult to determine exactly the initial conditions. There is no amorphization, however it is known that extended defects can appear as well as activation levels greater than the solubility limit (Csol) [4]. The modeling

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“…Short-time, high-temperature treatments, such as transient-rapid thermal annealing (T-RTA), are compatible with the requirement of low thermal budget processing [2,3]. Analysis of doping and damage profiles of implanted silicon has been performed using a number of techniques, such as (cross-section) transmission electron microscopy ((X)TEM) [4][5][6][7][8][9], secondary ion mass spectrometry (SIMS) [10][11][12][13], Rutherford backscattering spectrometry (RBS) [14], Secco etching [ 15] C-t measurements [ 16,17] or C-V measurements [16]. Most of these techniques are destructive or require special sample preparation.…”

Section: Introductionmentioning

confidence: 99%

Optimization of ion implantation damage annealing by means of high-resolution X-ray diffraction

et al. 1993

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High-resolution X-ray diffraction (HR-XRD) was investigated as a possible technique for the qualitative analysis of damage annealing of low-dose, high-energy implanted (001) silicon, implanted with dopants smaller than the host atom. The choice of proper Bragg reflection for the rocking-curve measurements is shown to be of crucial importance. The graphic construction of the Ewald sphere is a useful aid for this purpose. As the in-plane lattice constant is confined by the underlying substrate, a change occurs in the perpendicular direction only. Therefore the (026)~ reflection appears to be the most suitable for the detection of changes in lattice constant caused by implantation damage. Qualitative analysis of rocking curves of P-and B-implanted Si samples was compared with electrical measurements and cross-section transmission electron micrographs. It could be established that the minimum implantation doses of P and B at energies ranging from 0.5 to 1.5 MeV, for which HR-XRD is sensitive enough, are about 1.5 x 10 ~4 cm -2 and 5 x 10 ~3 cm -2 respectively. The minimum peak temperature needed for complete damage anneal by transient-rapid thermal annealing was about 1400 K for all doses considered.

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Diffusion of boron in silicon during post-implantation annealing

Cited by 181 publications

References 24 publications

Mechanisms of boron diffusion in silicon and germanium

Mechanisms of boron diffusion in silicon and germanium

Modeling High Concentration Boron Diffusion with Dynamic Clustering: Influence of the Initial Conditions

Optimization of ion implantation damage annealing by means of high-resolution X-ray diffraction

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