Transient enhanced diffusion of boron in Si

Jain, Suresh; Schoenmaker, Wim; Lindsay, Richard; Stolk, P. A.; Decoutere, Stefaan; Willander, Magnus; Maes, H.E.

doi:10.1063/1.1471941

Cited by 232 publications

(131 citation statements)

References 98 publications

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“…The B spikes with a concentration of 3 Â 10 19 cm À3 that interfere with the diffusion profile reveal an immobile fraction of B in Ge. This is similar to the behavior of B in Si where B-interstitial clusters have been identified as the origin of the immobile B fraction [28]. The concept of an interstitialmediated diffusion in Ge under irradiation is confirmed by the diffusion behavior of P. P diffusion is mediated by donor-vacancy pairs via the vacancy mechanism [see Eq.…”

Section: Prl 103 255501 (2009) P H Y S I C a L R E V I E W L E T T Esupporting

confidence: 53%

“…However, interstitials in Ge can be formed under irradiation as demonstrated in previous studies [10,13]. Stimulated by these results and the understanding on the evolution of interstitial clusters in Si [28], the impact of implantation damage on the diffusion in Ge was investigated by several research groups [11,12,29]. However, post anneals of dopant implanted Ge did not reveal any significant TED or transient retarded diffusion (TRD) [29,30].…”

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confidence: 99%

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Interstitial-Mediated Diffusion in Germanium under Proton Irradiation

et al. 2009

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We report experiments on the impact of 2.5 MeV proton irradiation on self-diffusion and dopant diffusion in germanium (Ge). Self-diffusion under irradiation reveals an unusual depth independent broadening of the Ge isotope multilayer structure. This behavior and the observed enhanced diffusion of B and retarded diffusion of P demonstrates that an interstitial-mediated diffusion process dominates in Ge under irradiation. This fundamental finding opens up unique ways to suppress vacancy-mediated diffusion in Ge and to solve the donor deactivation problem that hinders the fabrication of Ge-based nanoelectronic devices. DOI: 10.1103/PhysRevLett.103.255501 PACS numbers: 61.80.Jh, 61.72.jj, 61.82.Fk, 81.40.Wx Over the past few years the elemental semiconductor Ge has been the subject of many experimental [1-13] and theoretical investigations [14][15][16][17][18][19][20][21][22][23][24][25] to elucidate the electronic and diffusion properties of point defects as well as their interaction. Understanding these properties helps to develop strategies for efficient defect engineering that are crucial for the fabrication of the next generation of nanoelectronic devices. Utilizing Ge instead of silicon (Si) for complementary metal oxide semiconductors (CMOS) technology one can take advantage of the higher electron and hole mobilities in Ge compared to Si [26]. Whereas the p-channel Ge-MOSFET (metal oxide semiconductor fieldeffect transistor) made of heavily B doped source and drain regions was already demonstrated [27], the n-channel MOSFET remains a challenge due to the enhanced diffusion of n-type dopants such as P, As, and Sb under extrinsic doping conditions and the deactivation of the donors for concentrations exceeding 10 19 cm À3 [7,9,27]. The enhanced diffusion is a consequence of the singly negatively charged donor-vacancy ðAVÞ À pair that mediates donor diffusion in Ge according to the reaction [7,9] where A þ s and V 2À are the singly positively charged substitutional donor with A 2 fP; As; Sbg and the doubly negatively charged vacancy (V 2À ), respectively. The deactivation is related to the formation of inactive donorvacancy clusters whose formation is favored due to Coulomb attraction between A þ s and ðAVÞ À via the reaction [9]The formation of A 2 V and even bigger clusters A n V m is consistent with the predictions of density functional theory calculations [23]. Reactions (1) and (2) indicate that the donor-vacancy pair mediates both the diffusion and deactivation of n-type dopants in Ge. Effective defect engineering that aims to suppress the enhanced diffusion and deactivation of donors in Ge should reduce the concentration of the AV pairs. In this letter we demonstrate that defect engineering with Ge interstitials makes it possible to effectively suppress the enhanced diffusion of donor atoms.

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Section: Prl 103 255501 (2009) P H Y S I C a L R E V I E W L E T T Esupporting

confidence: 53%

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confidence: 99%

Interstitial-Mediated Diffusion in Germanium under Proton Irradiation

et al. 2009

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“…4,65 Typically, ion implantation in Ge hardly comes up with the formation of stable I-type defects. Only recently, it has been clarified that end-of-range (EOR) extended defects do also form in Ge after pre-amorphization followed by SPE regrowth, 111,112 even if defects are much smaller and less stable than in Si.…”

Section: B Diffusion In C-ge: the Role Of Self-interstitials A Bmentioning

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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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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“…This phenomenon is called transient-enhanced diffusion ͑TED͒, and it may be several orders of magnitude faster than normal thermal diffusion. TED is particularly dramatic for boron, 2 the most frequently used p dopant, hindering thus the further miniaturization of CMOS devices.…”

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confidence: 99%

Lattice site investigation of F in preamorphized Si

et al. 2007

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The lattice location of F atoms in Si was experimentally studied. Si single crystals were amorphized, implanted with F, and afterwards the amorphous layer was recrystallized. Some of the samples prepared in this way were also annealed at 750°C for 60 min. The 19 F͑p , ␣␥͒ 16O resonant nuclear reaction at 340.5 keV was employed to measure the probability of a close encounter between protons and F nuclei as a function of the incident angle with respect to six major crystalline directions. The predictions of several ab initio calculations proved to be incompatible with the present experimental findings. The miniaturization of complementary metal-oxidesemiconductor ͑CMOS͒ devices requires the confinement of dopants very close to the surface. In the microelectronics industry, the dopants are introduced through ion implantation. This technique is widely used because the depth and concentration of the dopant are easily controlled and reproduced. However, the implantation process generates point defects ͑self-interstitials and vacancies͒ in the target at a concentration well above the thermodynamical equilibrium level.1 These defects undesirably accelerate the dopant diffusion. This phenomenon is called transient-enhanced diffusion ͑TED͒, and it may be several orders of magnitude faster than normal thermal diffusion. TED is particularly dramatic for boron, 2 the most frequently used p dopant, hindering thus the further miniaturization of CMOS devices.In order to reduce the boron TED, coimplantation of F is currently used in the microelectronics industry, although the role F plays in the reduction of boron TED has not yet been entirely understood. To better understand the mechanism whereby F leads to a decrease of boron TED, substantial experimental and theoretical work has been carried out. Up to now, it is known that the slowing down of boron TED occurs by the interaction between F and point defects, and it has been suggested that F atoms form complexes with these defects. [3][4][5][6][7][8][9] By ab initio calculations, several authors 5,7,8,10 have found that the lowest-energy state for a single interstitial F in Si is at the bond-centered the ͑BC͒ site in the +1 charge state or at the tetrahedral ͑T͒ site in the −1 charge state, depending on the Fermi energy. However, in Refs. 5 and 7 it was obtained that fluorine-vacancy ͑FV͒ complexes are highly favored over the interstitial configuration. From the experimental standpoint, the detection of FV complexes by positron annihilation spectroscopy has been reported in Refs. 3, 4, and 9 and also through sheet resistance measurement in Ref. 6. On the other hand, electric quadrupole hyperfine interaction and preliminary channeling experiments have indicated that F might occupy either bond or antibonding ͑AB͒ interstitial sites. 11,12 In the present work, the lattice location of F atoms in Si was experimentally investigated. Czochralski n-type ͑P-doped͒ ͗100͘-Si single crystals with 10-20 ⍀ cm resistivity were amorphized from the surface down to a depth of about 440 nm wit...

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Transient enhanced diffusion of boron in Si

Cited by 232 publications

References 98 publications

Interstitial-Mediated Diffusion in Germanium under Proton Irradiation

Interstitial-Mediated Diffusion in Germanium under Proton Irradiation

Mechanisms of boron diffusion in silicon and germanium

Lattice site investigation of F in preamorphized Si

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