Helium desorption/permeation from bubbles in silicon: A novel method of void production

Griffioen, C.C.; Evans, John H.; Jong, P.C. de; Veen, A. van

doi:10.1016/0168-583x(87)90522-2

Cited by 251 publications

(110 citation statements)

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“…Some of these clusters will interact with other more stable clusters leading to larger He n -V m agglomerates and finally cavities. Helium desorption from small unstable vacancy clusters, has been previously reported for temperature as low as 400 K. 6 The cavities become more and more faceted as the temperature increases, and finally, at a higher temperature ͑1073 K͒, no more cavities are observed. Helium is known to be the vital component in cavity formation so that even at high temperatures, it is the agglomeration of gas and vacancies that leads to cavity formation.…”

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“…As for helium release in the hightemperature part of the spectrum, this is due to permeation from cavities to the surface. 6,7 This process also involves diffusion of helium through the silicon lattice however the limiting process is the penetration of He in the cavity into the silicon matrix. The peak observed close to 1300 K for 473-873 K implantation temperatures is thus identified as a release by permeation from interior cavities.…”

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On the effects of implantation temperature in helium implanted silicon

Oliviero

David

Beaufort

et al. 2002

Applied Physics Letters

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He ϩ ions were implanted into silicon with a fluence of 5ϫ10 16 cm Ϫ2 at different temperatures ranging from 473 to 1073 K. Samples were analyzed by thermal helium desorption spectroscopy and by transmission electron microscopy. As far as cavity formation is concerned, the behavior can be divided into three stages depending on the implantation temperature. However, it is found that helium release from cavities is governed by a single mechanism regardless of the implantation temperature. © 2002 American Institute of Physics. ͓DOI: 10.1063/1.1525059͔With the miniaturization of microelectronic devices, the purity requirements of semiconductors become extremely severe. In particular, the density of metallic impurities in the active region of the devices must be extremely low. Such an impurity level can only be reached by a gettering treatment.In the last few years, work 1,2 has shown that helium induced cavities in silicon can be used as very efficient gettering sites. Cavities in silicon are usually formed by high dose He ion implantation. During subsequent annealing at temperatures above 700°C, bubbles grow and He is released from them by gas outdiffusion, leading to void formation, i.e., empty cavities. Metallic impurities can be trapped on the cavities at their internal surfaces. 1 Numerous studies have been performed varying implantation parameters 3 to optimize cavity formation. The effects of varying the implantation temperature have, however, not received much attention. In this letter, a combination of thermal helium desorption spectroscopy ͑THDS͒ and transmission electron microscopy ͑TEM͒ was used to study the effect of implantation temperature.All the experiments were performed on commercial n -n ϩ silicon wafers. The n-type layer was epitaxially grown on a ͗111͘ orientated n ϩ substrate of Czochralski silicon. The doping concentration of the 100 m thick n region was 1ϫ10 14 P cm Ϫ3 . These samples were implanted to a constant dose of 5ϫ10 16 ions cm Ϫ2 with 50 keV helium ions (Rpϭ500 nm and ⌬Rpϭ140 nm according to SRIM calculations͒. 4 The beam current was kept at 40 A. The structure of the implantation damage was studied with crosssectional TEM using a JEOL 200 CX operating at 200 kV. In order to study cavities with minimal contrast from the unavoidable accompanying lattice damage, specimens were tilted from their ͗110͘ orientation by few degrees in order to reduce diffraction effects. They were also imaged in underfocus and overfocus conditions to highlight the cavity edges with Fresnel contrast. THDS measurements were performed in an ultrahigh vacuum chamber (10 Ϫ8 Pa͒. Helium desorption was monitored using a quadrupole mass spectrometer Balzers QMG 111B while the sample was annealed with a constant heating rate of 5 K/s.The thermal desorption spectrum of helium from the sample implanted at 473 K is shown in Fig. 1͑a͒. Helium release clearly occurs partially at a low temperature from 700 to 900 K and in a high-temperature regime centered at about 1300 K with all the helium being released by 1400 K. Fo...

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On the effects of implantation temperature in helium implanted silicon

Oliviero

David

Beaufort

et al. 2002

Applied Physics Letters

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“…Small clusters dissociate at low temperature, and the dissolving of larger clusters needs higher annealing temperature. This mechanism can interpret the fact that divacancies dissolve at relatively low temperature of 200± 3008C and that the migration and coalescence of voids observed by XTEM only occur at temperature higher than 7008C [1].…”

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“…The voids present in the surface region of the 7008C annealed sample shrank in size (2 nm in diameter), while the void population decreased. Since the implanted He effuses out from the bubbles at temperature higher than 7008C [1,4,11], thè bubbles' observed in Fig. 1c are empty voids.…”

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Defect distribution and evolution in He+ implanted Si studied by variable-energy positron beam

et al. 1998

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The distribution and annealing behavior of the vacancy-type defects and displaced Si atoms in crystal Si caused by 7 £ 10 16 cm 22 , 140 keV He 1 implantation have been studied by variable-energy positron annihilation technology, cross-sectional transmission electron microscopy and Rutherford backscattering and channel spectroscopy. It was found that in the as-implanted sample, a region 400 nm wide around the projected range was heavily damaged by the implantation and dense microbubbles with diameters of 1.5±6 nm were formed in this region, while the near surface region was slightly damaged and small vacancy clusters less than 1 nm in diameter and some microbubbles scattered in this region. The defects in the heavily damaged region were stable at temperature below 4008C and began to recrystallize from the crystalline Si in the near surface layer by solid phase epitaxy at temperatures higher than 6008C. High temperature (11008C) was needed to anneal out most of the defects in this heavily damaged layer. The small vacancy clusters in the near surface region become removable at 3008C and could be removed at 7008C by dissociation and diffusing both to the surface and to the heavily damaged region. The diameter of the microbubbles in the original heavily damaged region increased with the increasing of annealing temperature and their density decreased with the increasing of annealing temperature at temperatures above 7008C. The annealing behavior of the vacancy clusters induced by He 1 implantation is discussed by thermodynamical process. q 1998 Elsevier Science S.A. All rights reserved.

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