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  • 1
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The local atomic environment of the Sb dopant in 2 and 5×1016 ions/cm2 implanted Si samples has been studied by near grazing incidence fluorescence extended x-ray absorption fine structure at different stages of the Sb deactivation process. The annealings were performed at high temperature (900–1000 °C) during various periods: 30 s–4 h. The Sb out-diffusion and the high percentage of Sb precipitates are put into evidence especially for Sb-only implanted samples. The comparison of the Sb and B codiffusion data with the corresponding ones obtained by the diffusion of Sb alone revealed several anomalous effects due to dopant interaction. Moreover, a simulation program including dopant precipitation and donor–acceptor pairing allows us to foresee most of the anomalous phenomena occurring in high-concentration codiffusion experiments. © 1996 American Institute of Physics.
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 5005-5012 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The codiffusion of arsenic and phosphorus implanted in silicon has been investigated after annealing at 900 and 1000 °C for different concentrations of the dopants. Analysis of the profiles was performed using secondary-ion-mass spectroscopy, junction staining, and incremental resistivity and Hall measurements. The results do not evidence any direct interaction between the dopants. All the observed anomalous effects of the codiffusion, compared with the diffusion of the single elements by themselves, seem to be justifiable on the basis of the interactions between the dopants and the defects produced by ion implantation. In addition, it has been observed that the presence of a high concentration of As atoms makes the annealing of the implantation damage faster and strongly reduces the P transient-enhanced diffusion. This effect favors the fabrication of graded shallow junctions with a high-surface-carrier concentration.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 697-703 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An extensive investigation on the diffusion and precipitation of Sb implanted in Si has been carried out. The rapid epitaxial regrowth of the amorphous layer produced by the incident ions brings Sb atoms into a substitutional position up to a concentration threshold of about 3.5 × 1020 cm−3. This high supersaturation (the solubility of Sb in Si is about 2 × 1019 cm−3 at 1000 °C) and the low value of the surface free energy facilitate the nucleation of precipitates, which form and grow in concomitance with the diffusion during the annealing. The kinetics of the precipitation has been investigated at 800, 900, and 1000 °C with isothermal treatments ranging between 3 min and 341 h. The experimental data have been compared with the results of a simulation program that takes into account the precipitation phenomena. Good agreement has been obtained for all the investigated experimental conditions both for total and carrier distributions. The model represents a significant improvement of the simulation of Sb diffusion in silicon; in fact, the more commonly used process codes are inadequate to correctly foresee the dopant distribution in supersaturated conditions.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3250-3258 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An extensive investigation on the diffusion of boron implanted at high concentration in preamorphized silicon has been carried out for rapid thermal annealing and conventional furnace annealing. The rapid process of epitaxial regrowth of the amorphous layer brings B atoms into substitutional positions, and thus electrically active, up to a concentration threshold of about 3.5×1020 cm−3. This value is nearly independent of the annealing temperature and of the implanted dose. Since the concentration of dopant in solution is higher than the solubility value, precipitation phenomena occur in concomitance to diffusion during the annealing. The kinetics of precipitation has been investigated at 800, 900, and 1000 °C with isothermal treatments ranging between 10 s and 171 h. A simulation program taking into account precipitation phenomena has been developed modifying the suprem iii code. The density of nuclei of the new phase has been evaluated on the base of the models of classic nucleation theory, while the rate of precipitation growth has been determined following Ham's theory. Excellent agreement with experimental data has been obtained in a wide range of experimental conditions. The model represents a significative improvement of the simulation of high-concentration B diffusion in Si; the more commonly used process simulations are inadequate to correctly foresee the dopant redistribution in supersaturated conditions.
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  • 5
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Laser-annealed and further thermally annealed arsenic implanted silicon specimens have been investigated in a range of doses from 1×1016 to 5×1016 As/cm2, with different experimental techniques: electrical measurements, transmission electron microscopy (TEM), double-crystal x-ray diffractometry (DCD), and extended x-ray absorption fine structure analysis (EXAFS). On the as laser-annealed samples, in the whole range of doses examined, a lattice contraction of the doped layer has been evidenced by DCD, whereas, on the same specimens, EXAFS measurements have shown the presence of a local expansion around substitutional As atoms. The relationship between strain and carrier concentration has been found to be approximately linear and can be described by the presence of a size and an electronic effect, as recently proposed in the literature. The former effect represents the atomic size contribution, while the latter is the strain induced by the variation of the conduction-band minima due to the doping. After a subsequent thermal annealing in a low-temperature range (350–550 °C), a strong deactivation of the dopant has been evidenced by electrical measurements. From the experimental results, a new model of the first step of the As deactivation phenomenon at low temperature is proposed. It is described by the capture of two electrons from a pair of As atoms in the second neighbor position in the Si lattice, leading to the formation of a positively charged arsenic-vacancy cluster (As2V)+, and to the emission of a negatively charged Si self-interstitial I−. This model takes into account the main phenomena that are experimentally observed simultaneously to the As deactivation, i.e., the transition from a contraction to a dilatation of the strain observed by DCD and the formation of interstitial loops. At relatively high temperatures (650–900 °C), the hypothesis of the coexistence of the clusters and of the observed precipitates has to be taken into account in order to explain the nature of the inactive As. However, whether clustering or precipitation is the dominant phenomenon still remains an open question.
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  • 6
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The influence of the lattice defects induced by silicon-ion implantation on the B, P, As, and Sb diffusivities is investigated after annealing between 700 and 900 °C. The nature and depth position of the residual implantation defects in undoped samples is determined by the analysis of the rocking curves obtained by triple-crystal x-ray diffraction and transmission electron microscopy. In particular, besides the interstitial dislocation loops and clusters below the original amorphous-crystal interface, the epitaxial regrowth of the amorphized silicon leaves a vacancy-rich surface layer and a deeper region enriched in interstitials. These regions correspond to those where Monte Carlo simulations of defect production foresee excess point defects. Accordingly, as the dopant is located in correspondence with the vacancy or interstitial clusters, different behaviors of anomalous diffusion are observed. In the deep region where an interstitial excess is present, B and P show marked enhanced diffusion, while only a small enhancement is exhibited by As and Sb. On the contrary, retarded diffusivity for B and light enhancement for As and Sb are observed in the surface layer. These different trends are consistent with the different accepted contributions of vacancies and interstitials to the diffusion mechanisms of the investigated dopants.
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  • 7
    ISSN: 1432-0630
    Keywords: 61.70-r ; 61.70.At ; 61.70.Sk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The electrical activation of boron implanted in crystalline and preamorphized silicon has been investigated during rapid thermal annealing performed with halogen lamps. Samples implanted with B+ fluences ranging between 5×1014 and 1×1016cm−2 and treated at temperatures between 900°C and 1100°C have been examined. When boron is implanted in crystalline Si, activation proceeds slowly atT<1000°C and cannot be completed in times typical of rapid thermal annealing (a few tens of seconds). The analysis of carrier profiles indicates that the time constant for activation is strongly affected by local damage and dopant concentration. If the total boron concentration exceeds equilibrium solubility, precipitation occurs concomitant to activation, even if the substitutional boron fraction is still lower than equilibrium solubility. ForT≧1000°C complete activation is obtained in times of about 10 s. In the case of preamorphized Si the activation occurs very quickly, during the recrystallization of the amorphous layer, for all the examined temperatures.
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  • 8
    ISSN: 1432-0630
    Keywords: 61.70 ; 64 ; 72.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The thermal evolution of monoclinic SiAs precipitates at 1050° C in silicon samples implanted with 1 and 1.5×1017 As/cm2 was followed by transmission electron microscopy (TEM) and secondary neutral mass spectrometry (SNMS). These experiments show, for the first time, the coexistence of two different states of As in silicon, i.e., the electrically active and the inactive mobile dopant, in equilibrium with monoclinic SiAs precipitates. Moreover, they provide, for the saturation concentration of As in silicon, which includes both these states, a value of 3×1021 cm−3 at 1050° C.
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  • 9
    ISSN: 1432-0630
    Keywords: 61.70-r ; 61.70.At ; 61.70.Sk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The electrical activation of boron implanted in crystalline and preamorphized silicon has been investigated during rapid thermal annealing performed with halogen lamps. Samples implanted with B+ fluences ranging between 5×1014 and 1×1016cm−2 and treated at temperatures between 900°C and 1100°C have been examined. When boron is implanted in crystalline Si, activation proceeds slowly atT<1000°C and cannot be completed in times typical of rapid thermal annealing (a few tens of seconds). The analysis of carrier profiles indicates that the time constant for activation is strongly affected by local damage and dopant concentration. If the total boron concentration exceeds equilibrium solubility, precipitation occurs concomitant to activation, even if the substitutional boron fraction is still lower than equilibrium solubility. ForT≧1000°C complete activation is obtained in times of about 10 s. In the case of preamorphized Si the activation occurs very quickly, during the recrystallization of the amorphous layer, for all the examined temperatures.
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  • 10
    ISSN: 1432-0630
    Keywords: 61.80 ; 68.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract 30 keV boron ions are implanted at doses of 2×1014 and 2×1015 cm−2 in 〈100〉 silicon wafers kept at room or liquid-nitrogen temperatures. The samples are analyzed by double-crystal X-ray diffraction, transmission electron microscopy and secondary ion-mass spectrometry before and after furnace annealing at 800°C. The low-dose implant does not amorphize the substrate at any of the temperatures, and residual defects together with a remarkably enhanced boron diffusion are observed after annealing. The high-dose implant amorphizes the substrate only at low temperature. In this case, unlike the room-temperature implant, the absence of any residual defect, the incorporation of the dopant in substitutional position and a negligible profile braodening of boron are obtained after annealing. In principle, this process proves itself a promising step for the fabrication of p +/n shallow junctions with good electrical characteristics.
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