Role of fluorine in suppressing boron transient enhanced diffusion in preamorphized Si

Impellizzeri, G.; Santos, José Luiz dos; Mirabella, S.; Priolo, F.; Napolitani, E.; Carnera, A.

doi:10.1063/1.1675935

Cited by 55 publications

(27 citation statements)

References 13 publications

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“…The effect of F in engineering point defects (vacancies and self-interstitials) and, as a consequence, in affecting the diffusion of dopants in Si was extensively investigated by our group, and consists in the annihilation of self-interstitials at nano-bubbles introduced in the crystalline matrix through a complex mechanism of F segregation and incorporation within the crystalline phase. [18][19][20][21][22][23][24][25][26] The aim of this work is to study in detail the effect of F in modifying As diffusion in Ge. For this purpose, we performed structural and chemical characterizations of Ge samples co-implanted with F and As and annealed with different thermal budgets.…”

Section: Introductionmentioning

confidence: 99%

Fluorine effect on As diffusion in Ge

Impellizzeri

Boninelli

Priolo

et al. 2011

Journal of Applied Physics

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The enhanced diffusion of donor atoms, via a vacancy (V)-mechanism, severely affects the realization of ultrahigh doped regions in miniaturized germanium (Ge) based devices. In this work, we report a study about the effect of fluorine (F) on the diffusion of arsenic (As) in Ge and give insights on the physical mechanisms involved. With these aims we employed experiments in Ge co-implanted with F and As and density functional theory calculations. We demonstrate that the implantation of F enriches the Ge matrix in V, causing an enhanced diffusion of As within the layer amorphized by F and As implantation and subsequently regrown by solid phase epitaxy. Next to the end-of-range damaged region F forms complexes with Ge interstitials, that act as sinks for V and induce an abrupt suppression of As diffusion. The interaction of Ge interstitials with fluorine interstitials is confirmed by theoretical calculations. Finally, we prove that a possible F-As chemical interaction does not play any significant role on dopant diffusion. These results can be applied to realize abrupt ultra-shallow n-type doped regions in future generation of Ge-based devices.

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Section: Introductionmentioning

confidence: 99%

Fluorine effect on As diffusion in Ge

Impellizzeri

Boninelli

Priolo

et al. 2011

Journal of Applied Physics

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“…Moreover, the implantation conditions were similar to those used in Ref. 13. After F implantation, the samples were recrystallized by solid-phase epitaxy ͑SPE͒ through annealing at 450°C for 30 min plus 700°C for 80 s in an N 2 ambient.…”

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“…The 750°C/60 min annealing was performed in order to promote the interaction of F with self-interstitials released from the end-of-range region, as in Ref. 13. A subsequent site investigation should verify whether the interaction changes the F configuration.…”

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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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“…Other studies conclude that FV or FI complexes suppress B diffusion by reducing I emission from extended I defects generated by implantation. 3,4 Variable-energy positron annihilation spectroscopy ͑VE-PAS͒ is used here to probe the nature of the complexes formed by the implanted F ions. The technique has been used to identify FV complexes in thermally treated F-implanted Si.…”

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Fluorine-vacancy complexes in ultrashallow B-implanted Si

Abdulmalik

Coleman

Cowern

et al. 2006

Applied Physics Letters

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Shallow fluorine-vacancy ͑FV͒ complexes in Si have been directly observed using variable-energy positron annihilation spectroscopy and secondary ion mass spectrometry. The FV complexes, introduced to combat the deactivation and transient-enhanced diffusion of ultrashallow boron, were observed in preamorphized Si wafers implanted with 0.5 keV B and 10 keV F ions at a dose of 10 15 cm −2 , and then annealed isothermally at 800°C for times ranging from 1 to 2700 s. The results are in agreement with a model which predicts that the complexes are of the form F 3n V n , with n most probably being 1 and/or 2. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2335594͔Interest in the beneficial consequences of implanting F ions in Si has grown in recent years as defect engineering has been developed to meet the continuing challenges of device miniaturization. The application of particular interest here concerns ultrashallow B implantation into preamorphized Si regrown via solid-phase epitaxy ͑SPE͒; efficient activation of the B while limiting its diffusion is the key to the formation of ultrashallow junctions. Recent work by Cowern et al. 1 showed that F in B-implanted Si can form clusters that trap interstitals ͑I͒ released from the band of end-of-range ͑EOR͒ defects, which in turn both retard the transient enhanced diffusion of B implants and significantly decrease their deactivation. Kham et al. 2 linked F found at half the projected ion range to the formation of clusters of F with vacancies ͑V͒ in this region. Other studies conclude that FV or FI complexes suppress B diffusion by reducing I emission from extended I defects generated by implantation. 3,4 Variable-energy positron annihilation spectroscopy ͑VE-PAS͒ is used here to probe the nature of the complexes formed by the implanted F ions. The technique has been used to identify FV complexes in thermally treated F-implanted Si. 5,6 VEPAS measures the Doppler broadening of the 511 keV ␥-ray annihilation line, whose extent is determined by the average momentum of the electrons at the annihilation site. The broadening is characterized by the line-shape parameter S, defined as the central fraction of the 511 keV line. S for a chosen experimental setup has a characteristic value for each annihilation site, for example, for pure bulk Si or for each specific vacancy-type defect, the latter being strong positron traps. The mean depth z of positrons implanted with energy E ͑keV͒ is determined from the relation z = 17.2 E 1.6 nm. Secondary ion mass spectrometry ͑SIMS͒ measurements were performed to determine atomic profiles.Samples used in this study were n-type ͗100͘ Cz Si wafers with a resistivity of 10-20 ⍀ cm. All wafers were first preamorphized with 30 keV, 10 15 cm −2 Ge ions, and implanted with 0.5 keV B ions at 10 15 cm −2 . Half of the samples were additionally implanted with F ions at 10 keV and 10 15 cm −2 , placing the F ions between the B implants and the amorphous-crystalline interface. After restoring the amorphous layer to crystallinity via SPE regrowth ...

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Role of fluorine in suppressing boron transient enhanced diffusion in preamorphized Si

Cited by 55 publications

References 13 publications

Fluorine effect on As diffusion in Ge

Fluorine effect on As diffusion in Ge

Lattice site investigation of F in preamorphized Si

Fluorine-vacancy complexes in ultrashallow B-implanted Si

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