On the analysis of the activation mechanisms of sub-melt laser anneals

Clarysse, Trudo; Bogdanowicz, Janusz; Goossens, Jozefien; Moussa, Alain; Rosseel, Erik; Vandervorst, Wilfried; Petersen, Dirch Hjorth; Lin, Rong; Nielsen, Peter Brønnum; Hansen, Ole; Merklin, Gregory T.; Bennett, Nick; Cowern, N.E.B.

doi:10.1016/j.mseb.2008.09.038

Cited by 26 publications

(18 citation statements)

References 7 publications

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“…Actually, the electrical measurements for quantifying the BIC dissolution can be affected by scattering effects by B clusters on the mobility of charge carriers, which alters the determination of the active B amount. 6,[93][94][95][96] To properly measure the BIC dissolution energetics, we used the diffusion criterion together with a proper rate equation model able to fit the chemical profiles, to simulate the B diffusion and to extract the clustered B amount produced by a controlled I supersaturation into MBE grown Si samples containing various B doped regions. 97 It was clearly shown that B clusters dissolve following two distinct paths with different energy barriers (3.6 or 4.8 eV) and rates, the slowest one (with the 4.8 eV barrier) being present only for B concentration above the solid solubility.…”

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

103

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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%

Mechanisms of boron diffusion in silicon and germanium

Mirabella

Salvador

Napolitani

et al. 2013

Journal of Applied Physics

103

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“…27 Micro Hall effect measurements were used for their ability to accurately measure the electrical properties of ultrashallow junctions. [28][29][30] Micro Hall effect characterization was completed using a CAPRES microRSP M-150 M4PP fitted with Au-coated probes, a probe spacing of 20 lm, and a permanent magnet with a magnetic flux density of 0.475 T. Hall sheet number (n H ) and mobility values (l H ) were adjusted to obtain the carrier sheet number (n s ) and drift mobility (l d ) by using a scattering factor (r H ) of 1.21 as determined empirically. 7 The carrier density and drift mobility are related to the Hall values by n s ¼ n H Â r H and…”

Section: à2mentioning

confidence: 99%

Activation and thermal stability of ultra-shallow B+-implants in Ge

Yates

Darby

Petersen

et al. 2012

Journal of Applied Physics

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The activation and thermal stability of ultra-shallow B+ implants in crystalline (c-Ge) and preamorphized Ge (PA-Ge) following rapid thermal annealing was investigated using micro Hall effect and ion beam analysis techniques. The residual implanted dose of ultra-shallow B+ implants in Ge was characterized using elastic recoil detection and was determined to correlate well with simulations with a dose loss of 23.2%, 21.4%, and 17.6% due to ion backscattering for 2, 4, and 6 keV implants in Ge, respectively. The electrical activation of ultra-shallow B+ implants at 2, 4, and 6 keV to fluences ranging from 5.0 × 1013 to 5.0 × 1015 cm−2 was studied using micro Hall effect measurements after annealing at 400–600 °C for 60 s. For both c-Ge and PA-Ge, a large fraction of the implanted dose is rendered inactive due to the formation of a presumable B-Ge cluster. The B lattice location in samples annealed at 400 °C for 60 s was characterized by channeling analysis with a 650 keV H+ beam by utilizing the 11B(p, α)2α nuclear reaction and confirmed the large fraction of off-lattice B for both c-Ge and PA-Ge. Within the investigated annealing range, no significant change in activation was observed. An increase in the fraction of activated dopant was observed with increasing energy which suggests that the surface proximity and the local point defect environment has a strong impact on B activation in Ge. The results suggest the presence of an inactive B-Ge cluster for ultra-shallow implants in both c-Ge and PA-Ge that remains stable upon annealing for temperatures up to 600 °C.

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“…The activation level was estimated from the SIMS depth profile by integrating the dopant concentration under a cutoff value. The latter one defines the activation level when the active dose obtained from the integration corresponds to the Rs value, using an iterative procedure [11]. Under similar anneal conditions, the activation level of the junction fabricated from BII is ~2.3 × 10 20 cm -3 with Rs~320 Ω/sq and xj~24 nm.…”

Section: Pmos With Boron Dopingmentioning

confidence: 99%

Use of p- and n-type vapor phase doping and sub-melt laser anneal for extension junctions in sub-32 nm CMOS technology

et al. 2010

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We evaluated the combination of vapor phase doping and sub-melt laser anneal as a novel doping strategy for the fabrication of source and drain extension junctions in sub-32 nm CMOS technology, aiming at both planar and non-planar device applications. High quality ultra shallow junctions with abrupt profiles in Si substrates were demonstrated on 300 mm Si substrates. The excellent results obtained for the sheet resistance and the junction depth with boron allowed us to fulfill the requirements for the 32 nm as well as for the 22 nm technology nodes in the PMOS case by choosing appropriate laser anneal conditions. For instance, using 3 laser scans at 1300 °C, we measured an active dopant concentration of about 2.1 × 10 20 cm -3 and a junction depth of 12 nm. With arsenic for NMOS, ultra shallow junctions were achieved as well. However, as also seen for other junction fabrication schemes, low dopant activation level and active dose (in the range of 1-4 × 10 13 cm -2 ) were observed although dopant concentration versus depth profiles indicate that the dopant atoms were properly driven into the substrate during the anneal step. The electrical deactivation of a large part of the in-diffused dopants was responsible for the high sheet resistance values.

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On the analysis of the activation mechanisms of sub-melt laser anneals

Cited by 26 publications

References 7 publications

Mechanisms of boron diffusion in silicon and germanium

Mechanisms of boron diffusion in silicon and germanium

Activation and thermal stability of ultra-shallow B+-implants in Ge

Use of p- and n-type vapor phase doping and sub-melt laser anneal for extension junctions in sub-32 nm CMOS technology

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