High Dose Rate Effect of Focused-Ion-Beam Boron Implantation into Silicon (original) (raw)
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Focused boron ion beam implantation into silicon
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1985
Electrical properties of and lattice disorders@i Si substrates implanted with 16 kcV, focused, "B+ ion beam (FIB) have been investigated as a function of current density, beam-scan speed and ion dose, and compared with those obtained by conventional implantation. High electrical activation of the FIB implanted layers is obtained by annealing below 800°C due to the increase in amorphous zones created in the implanted areas. Amorphous zone overlapping occurs at FIB implantation doses of 1-2 x lOI ions/cm* when both high current density and slow scan speed (e-g 20 mA/cm' and 6 X 10s3 cm/s) are maintained. The reason for amorphous zone formation enhancement by FIB implantation is also discussed. Using this FIB B+ implantation, a new approach to fabrication of novel MOSFETs is presented.
Dynamic disordering process in Si during high dose rate B+ ion beam implantation
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1988
The dynamic disordering process in Si during high dose rate focused Bf ion beam (beam diameter 1-2 pm, current density-0.4 A/cm*) implantation has been investigated by cross-sectional TEM observations and ellipsometric analyses. The duration of the scanning ion beam was controlled by changing the beam scan speed. The amount of crystal damage exhibited a strong duration dependence, and more than a one order of magnitude loweimg of the critical dose to form a continuous amorphous layer is observed, compared with that for conventional impl~tation conditions. An activation energy of 0.1-0.2 eV was estimated by the relations between the damage and substrate temperature of the wafer during implantation. This value almost coincides with the migration energy of the doubly negative vacancy (V2-). This result suggests that the migration of V2-plays an important role in the dynamical overlapping of ion damage tracks during high dose rate implantation.
The formation of a continuous amorphous layer by room‐temperature implantation of boron into silicon
Journal of Applied Physics, 1988
Ion implantation of 60 ke V boron into {100} silicon at medium beam currents (150 ttA) was performed at 300-315 K over the dose range from 1 to 8 X 10 16 /cm 2 • Diffraction contrast and high-resolution phase contrast transmission electron microscopy (TEM) were used on planview and 90• cross-section samples to study the formation of a continuous amorphous layer as a function of increasing dose. Our TEM results show that, unlike implantation of Si with heavier ions where amorphization initially occurs at or around the projected range, the amorphization by high dose (> 5 X 1016/cm2) B-+-implanted Si first occurs at and/or near the surface. It is proposed that the buildup of a high concentration of vacancies which inevitably occurs near the surface during high-dose n-' implantation is primarily responsible for the observed near-surface amorphization. Based on the results of this investigation and those available in the published literature, it appears that low temperature (slow recombination rate for point defects) and high beam current (high generation rate for point defects) implantation may result in the optimum conditions for amorphous layer formation with boron.
Channeling implants of boron in silicon
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1991
80 keV B+ ions were implanted in (100) Si with a high-current implanter. The wafers were irradiated at O" and 7O. The feasibility of the 0 D implants was checked testing the influence of several geometrical parameters, such as the twist angle and the flex angle, on the shape and uniformity of the ion depth distributions. The damage generated by a high-fluence B+ implant was lower for the O" implanted samples and the disorder evolution was analyzed after different annealing processes were performed in the 600-1200' C temperature range. Agglomeration and dissolution of extended defects in the 0" implanted samples occurs at temperatures 100 o C lower than those in the 7 o implanted samples.
Range and damage distributions in ultra-low energy boron implantation into silicon
Journal of Stroke & Cerebrovascular Diseases, 1996
An ultra high vacuum, low energy ion implanter was used in conjunction with a range of analytical techniques to study the range and damage distributions of B+ ions implanted at normal incidence into Si(100) samples held at room temperature. Samples were implanted over a dose range from 1E14 ions/cm2 with and without a surface oxide layer and those implanted at 1 keV and below were capped with a nominal 20 nm layer of 28Si by ion beam deposition in situ in order to produce an oxygen equilibration layer for subsequent secondary ion mass spectrometry depth profiling. The samples were analysed using secondary ion mass spectroscopy, medium energy ion scattering, spectroscopic ellipsometry, spreading resistance profiling and high resolution, cross section transmission electron microscopy to obtain the range and damage distributions and junction depths. The general observations were that channelling occurs at all energies studied, and that the relationship between the damage and range distributions depends strongly on bombardment energy. Comparison of the range and damage profiles was carried out to ascertain the role of the surface in determining the behaviour of defects produced very close to it by the low energy implants required for the production of junctions at depths in the 20 to 50 nm range. The role of the surface or silicon/silicon dioxide interface as a defect sink significantly influences the B redistribution behaviour during rapid thermal annealing
Detection of the Defects Induced by Boron High-Energy Ion Implantation of Silicon
Journal of The Electrochemical Society, 2000
A preferential chemical etching method was used to investigate the secondary defects induced in silicon by high-energy boron ion implantation followed by a rapid thermal anneal at 1000ЊC for 30 s in N 2 ambient. The dislocation defects in silicon can be clearly delineated by the etchant of CrO 3 /HF mixing solution. Moreover, a band of striation corresponding to the region of dislocation defects can be observed from the cross-sectional view micrographs of scanning electron microscopy. For the high-energy boron ion implantation at a dose of 3 ϫ 10 14 cm Ϫ2 and energies of 0.5 to 2 MeV studied in this work, the defect density is estimated to be in the order of 6 ϫ 10 6 cm Ϫ2. Furthermore, we found a close correlation between the depth profiles of the observed etching pits and that of the implantation-induced damage.
Ultra low energy (100-2000 eV) boron implantation into crystalline and silicon-preamorphized silicon
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 1991
Very low energy (<1 keV) B + ion implantation has been carried out on both crystalline and silicon-preamorphized silicon. The amorphous layer depth was determined using Rutherford backscattering analysis (RBS). The penetration depth and channelling tail of B + ions into silicon was studied as a function of ion energy (100-2000 eV) and low temperature regrowth/annealing (T < 600° C), using secondary ion mass spectroscopy (SIMS). These studies also involved low energy (40-60 eV) ion beam deposition (IBD) of 10-20 nm isotopic 28Si + cap layer at room temperature to enable accurate SIMS depth profile measurements to be carried out. The results show the extent of the channelling tails at these low energies and indicate that sub 40 nm p +-n junctions with estimated carrier concentrations as high as 10 20 cm -3 can be obtained.
Lattice location of boron implanted silicon after laser annealing
Lettere Al Nuovo Cimento, 1978
Boron implanted (100)Si specimens were irradiated with Q-swicthed ruby laser pulse of (40+50) ns duration and of 0.7 or 2.7 J/cm 2 energy. The ion implanted amorphous layer becomes single crystal as measured by channeling effect with 1.6 MeV He + baekscattering after 2.7 J/cm ~ laser pulse irradiation, and the boron atoms are almost substitutionally located as determined by the liB(p, ~)SBe nuclear reaction. The 0.7 J/cm 2 laser pulse does not induce the amorphous to single-crystal transition no lattice location of boron was found by channeling, and the implanted ion concentration profile is the same as the as implanted one. Changes in the profile were found instead after the 2.7 J/cm 2 laser pulse irradiation.
The loss of boron in ultra-shallow boron implanted Si under heavy ion irradiation
Radiation Effects and Defects in Solids, 2006
Heavy ion impact has been known to cause a loss of light elements from the near-surface region of the irradiated sample. One of the possible approaches to a better understanding of the processes responsible for the release of specific elements is to irradiate shallow-implanted samples, which exhibit a wellknown depth distribution of the implanted species. In this work, the samples studied were produced by implantation of Si <1 0 0> wafers with 11 B at implantation energies of 250 and 500 eV and fluence of 1.0 × 10 15 atoms/cm 2 . Elastic Recoil Detection Analysis was applied to monitor the remnant boron fluence in the sample. Irradiation of the samples by a 14.2 MeV 19 F 4+ beam resulted in a slow decrease of boron remnant fluence with initial loss rates of the order of 0.05 B atom per impact ion. Under irradiation with 12 MeV 32 S 3+ ions, the remnant boron fluence in Si decreased exponentially with a much faster loss rate of boron and became constant after a certain heavy ion irradiation dose. A simple model, which assumes a finite desorption range and corresponding depletion of the nearsurface region, was used to describe the observations. The depletion depths under the given irradiation conditions were calculated from the measured data.
Depth of origin of desorbed boron In heavy ion irradiation of ultra-shallow boron implanted Si
Radiation Effects and Defects in Solids
Heavy ion impact has been known to cause a loss of light elements from the near-surface region of the irradiated sample. One of the possible approaches to a better understanding of the processes responsible for the release of specific elements is to irradiate shallow-implanted samples, which exhibit a wellknown depth distribution of the implanted species. In this work, the samples studied were produced by implantation of Si <1 0 0> wafers with 11 B at implantation energies of 250 and 500 eV and fluence of 1.0 × 10 15 atoms/cm 2 . Elastic Recoil Detection Analysis was applied to monitor the remnant boron fluence in the sample. Irradiation of the samples by a 14.2 MeV 19 F 4+ beam resulted in a slow decrease of boron remnant fluence with initial loss rates of the order of 0.05 B atom per impact ion. Under irradiation with 12 MeV 32 S 3+ ions, the remnant boron fluence in Si decreased exponentially with a much faster loss rate of boron and became constant after a certain heavy ion irradiation dose. A simple model, which assumes a finite desorption range and corresponding depletion of the nearsurface region, was used to describe the observations. The depletion depths under the given irradiation conditions were calculated from the measured data.
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