Overpressurized bubbles versus voids formed in helium implanted and annealed silicon

Fichtner, P.F.P.; Kaschny, J.R.; Yankov, R.A.; Mücklich, A.; Kreißig, U.; Skorupa, W.

doi:10.1063/1.118251

Cited by 72 publications

(51 citation statements)

References 12 publications

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“…4,43,44 In all these cases, the platelets formed parallel to close-packed planes under conditions of missing vacancy supply, while in Si platelet-type structures aligned to ͑100͒ planes have been reported. 45 The concentration of He atoms contained in resolvable plateletlike ''bubbles,'' c He * ͑total number of He atoms in bubbles per total number of matrix atoms, which is generally smaller than the concentration of implanted He, c He * Ͻc He ͒ may be estimated from the volume fraction occupied by these bubbles, N B V B , according to…”

Section: Helium Plateletsmentioning

confidence: 99%

Microstructural evolution of helium-implanted α-SiC

2000

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Helium has a decisive effect on the microstructure of silicon carbide materials after implantation and subsequent annealing. A dense population of bubbles and dislocation loops is already observed at relatively low displacement doses after annealing of helium-implanted ␣-SiC, while no visible damage appears after irradiation without helium implantation under otherwise equal conditions. The defects are separated from grain boundaries by defect-free zones of approximately 0.5 m width. The most intriguing features of the evolving microstructure are lenticular cavities ͑platelets͒, which transform to disk-shaped arrangements of bubbles with associated dislocation loops or even stacks of loops. The observed microstructural evolution and its dependence on implantation dose, annealing temperature, and time are quantitatively explained and discussed in terms of diffusion of interstitial He atoms and their clustering between adjacent lattice planes, thus forming nanocracks during implantation. The relaxation of the high gas pressure by matrix atom transfer from bubbles to loops during annealing and the coarsening of bubble-loop complexes are described by a coupled twocomponent Ostwald ripening process.

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Section: Helium Plateletsmentioning

confidence: 99%

Microstructural evolution of helium-implanted α-SiC

2000

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“…3͒ around some of the bubbles is also consistent with an overpressurized state. 9 The shoulder peak near 1000 K appearing for the 673 and 773 K implantations could be also related to the nucleation of larger overpressurized bubbles. The temperature of maximum release and the FWHM value are in agreement with a bubble size of 3 nm.…”

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confidence: 99%

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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“…This point should be further clarified. However, it seems important to remark that, different from the case of He implanted in silicon where overpressurized bubbles may form, 8 the implantation with heavier mass inert gas ions can lead to a damage induced relaxation process which reduces or prevents the build up of the overpressure. 15 Without a significant release of Ne atoms from the samples, the bubbles should achieve thermodynamic equilibrium conditions where the internal gas pressure is compensated by the surface tension of the surrounding matrix, thereby avoiding the appearance of a negative strain.…”

Section: Resultsmentioning

confidence: 99%

“…He induced cavities in c-Si are very efficient gettering sites for metal impurities, so that He implantation presents potential applications for silicon device technology. [7][8][9] Implantation of Si with noble gas ions other than He ϩ at high temperatures has received little attention up to the present.…”

Section: Introductionmentioning

confidence: 99%

Strain development and damage accumulation during neon ion implantation into silicon at elevated temperatures

Cima

Boudinov

Souza

et al. 2000

Journal of Applied Physics

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The development of mechanical strain and accumulation of damage in silicon single crystals implanted with Ne ions to doses in the range of 0.1-1.0 ϫ10 17 cm Ϫ2 at temperatures from 200 to 600°C were investigated employing Rutherford backscattering spectrometry, high resolution x-ray diffraction ͑HRXRD͒ analysis and cross section transmission electron microscopy ͑XTEM͒. Two distinct layers have been found in the implanted material: A near-surface layer (Ͻ 0.2 m thick͒ where no extended defects are observed and a buried layer (Ϸ0.5 m thick͒ containing a dense array of dislocation loops and defect clusters. XTEM analysis revealed a distribution of small spherical cavities presumably filled with Ne, with a diameter Ͻ4 nm, extending along the entire depth of the implanted layer. HRXRD studies showed the presence of a positive strain ͑of expansion͒, irrespective of the implanted dose and temperature. The findings are discussed in terms of the proposed model which assumes that vacancy-type defects are consumed during the formation of Ne bubbles.

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Overpressurized bubbles versus voids formed in helium implanted and annealed silicon

Cited by 72 publications

References 12 publications

Microstructural evolution of helium-implanted α-SiC

Microstructural evolution of helium-implanted α-SiC

On the effects of implantation temperature in helium implanted silicon

Strain development and damage accumulation during neon ion implantation into silicon at elevated temperatures

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