Anomalous diffusion of nitrogen in nitrogen-implanted silicon

Hockett, R. S.

doi:10.1063/1.101266

Cited by 33 publications

(19 citation statements)

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“…In the Epi-Si case the clusters are slowly emitting mobile N, so there is still a source of N from the peak toward the bulk of the wafer. While the diffusion in CZ-Si reproduces closely that reported by Hockett,9 in Epi-Si the nitrogen diffusion behavior is completely different. It is remarkable that up to 750°C 30 min nitrogen is immobile in Epi substrates, whereas for the same thermal treatment it diffuses for ϳ8 m into the bulk in CZ-Si.…”

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confidence: 76%

Effect of Oxygen on the Diffusion of Nitrogen Implanted in Silicon

Mannino

Libertino

Napolitani

et al. 2004

Electrochem. Solid-State Lett.

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Nitrogen implants were performed in Si wafers of variable purity, i.e., epitaxial layers, float zone, and Czochralski silicon ͑CZ-Si͒. The diffusion behavior of nitrogen reported by Hockett in Appl. Phys. Lett., 54, 1793 ͑1989͒, where nitrogen diffuses for several micrometers at temperatures as low as 750°C and the profiles assume a ''double-peak'' structure, is peculiar of CZ-Si. In contrast, in pure epitaxial-Si, nitrogen is immobile at low temperature but, at a higher temperature ͑850°C͒, the broadening of the nitrogen profile never assumes the shape observed in CZ-Si. Our results suggest that oxygen determines the shape of the nitrogen diffusion profiles.Nitrogen is currently attracting a broad interest in the semiconductor industry due to the possibility it offers to improve thin oxide reliability, prevent dopant penetration, silicide stability, and to control grown-in defects during the Si ingot growth. 1-3 A full implementation of such an atomic impurity into wafer processing still requires a deeper knowledge of the interaction mechanism of nitrogen with dopants, with other impurities present in the silicon substrate ͑e.g., oxygen and carbon͒ and, more important, of its diffusion mechanism. In this respect several theoretical studies have been performed to explain the preferred locations of the nitrogen atoms in the silicon lattice and some possible diffusion paths. 4-6 Almost all the experiments are devoted to the investigation of thin-oxide properties and fabrication in the presence of nitrogen, but much less work has been done on the experimental determination of nitrogen diffusion behavior. 7-10 Moreover, under quasi-identical experimental conditions, some striking discrepancies can be found, for example, between the mobility that allows nitrogen to diffuse out of the sample through the surface, as recently reported by Adam et al., 10 and the partial immobility close to the surface, associated with long-range diffusion ͑for several micrometers͒ into the bulk, reported by Hockett. 9 In this paper we explore nitrogen diffusion by intentionally varying the impurity content of the silicon substrate in which nitrogen is implanted at medium energy. Our approach, not used so far in other experiments reported in the literature, allows one to learn more about the diffusion beahvior of nitrogen, through the establishment of the conditions under which nitrogen may diffuse easily at low temperatures for several micrometers or when the tendency for nitrogen to form complexes with impurities or itself prevails.In this work ͑100͒-oriented n-type crystalline Si wafers were used. In particular, epitaxially grown Si layers ͑Epi͒, Float zone ͑FZ͒, and Czochralski ͑CZ͒ grown wafers with resistivities of 5-15 ⍀ cm have been used. This allowed us to use samples with widely different concentrations of intrinsic contaminants, from the most pure Epi to the CZ material rich of C and O ͑i.e., ͓C͔ and ͓O͔ varied in the range ϳ10 15 to 10 18 /cm 3 ). These samples were implanted with N ions at an energy of 240 keV and fluences o...

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confidence: 76%

Effect of Oxygen on the Diffusion of Nitrogen Implanted in Silicon

Mannino

Libertino

Napolitani

et al. 2004

Electrochem. Solid-State Lett.

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“…Profiles after ion implantation [18,19] are considerably more complex, and the possibility of a catalytic effect of oxygen on nitrogen diffusion was reported recently [20]. In the analysis of Adam et al [21], nitrogen dimers were not taken into consideration nor apparently needed to obtain an excellent description of the experimental profiles.…”

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confidence: 99%

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confidence: 99%

Ab InitioIdentification of the Nitrogen Diffusion Mechanism in Silicon

et al. 2005

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In this Letter, we present ab initio results identifying a new diffusion path for the nitrogen pair complex in silicon, resulting in an effective diffusivity of 67 expÿ2:38 eV=kT cm 2 =s. This nudged elastic band result is compared with other nitrogen diffusion paths and mechanisms, and is determined to have unmatched agreement with experimental results. It is also shown that careful consideration of total energy corrections and use of a fully temperature-dependent diffusion prefactor have modest but important effects on the calculation of diffusivity for paired and for interstitial nitrogen. DOI: 10.1103/PhysRevLett.95.025901 PACS numbers: 66.30.Jt, 61.72.Bb, 61.82.Fk Nitrogen doping of silicon has become a process of increasing importance because of its various effects on the formation of extended defects in silicon. The first prominently reported effect was the complete suppression of void formation in float-zone processed crystals [1]. In Czochralski-grown silicon, because of an additional interaction with oxygen, the mechanism is less effective and a higher density of relatively smaller voids and grown-in oxide precipitates was observed in nitrogen-doped crystals [2]. Finally, nitrogen is known to increase the mechanical strength of silicon by locking dislocations [3] and, when implanted with a sufficient dose, to reduce the oxidation rate [4]. In partial explanation of the above effects, it has been shown that the N 2 pair readily complexes with vacancies, both in a metastable, immobile N 2 V configuration, and in the very stable N 2 V 2 configuration which can form from either the reaction N 2 V V ! N 2 V 2 or N 2 V 2 ! N 2 V 2 [5,6]. The N 2 V 2 complex has been shown to attract oxygen into stable complexes, indicating the possibility of further oxygen precipitate nucleation based on the N 2 pair.As early as the investigations of Stein [7] in 1985, it was concluded from isotope shifts that the nitrogen dimer configuration is prevalent at room temperature. Jones et al. [8] confirmed this conclusion using a combination of spectroscopic and ab initio investigations. Except for the work of Gali et al. [9], who calculated a binding energy of 1.73 eV, all theoretical investigations agree on a rather high binding energy between 3.67 and 4.3 eV [6,10 -12]. In contrast, the primary diffusion mechanism for nitrogen, in general, and the N 2 pair, in particular, has been disputed in the literature.In a variety of experimental investigations based on nitrogen outdiffusion from doped substrates [13] or on the indiffusion of nitrogen from the ambient [14 -17], the profiles obtained were interpreted in terms of the diffusion of N 2 as an entity. The diffusion data obtained are shown in Fig. 1 and can be described best by a diffusion constant of D N 2 35 expÿ2:34=kT cm 2 =s( 1) with the 90% confidence interval for the activation energy ranging from 2.01 to 2.77 eV. Profiles after ion implantation [18,19] are considerably more complex, and the possibility of a catalytic effect of oxygen on nitrogen diffusion was repor...

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“…Profiles after ion implantation [28,29] are considerably more complex and the possibility of a catalytic effect of oxygen on nitrogen diffusion has been reported recently [30]. In the analysis of Adam et al [31] nitrogen dimers were not taken into consideration nor apparently needed to obtain an excellent description of the experimental profiles.…”

Section: Ab Initio Identification Of the Nitrogen Diffusion Mechanismmentioning

confidence: 97%

Ab initio assisted process modeling for Si-based nanoelectronic devices

Windl

2005

Materials Science and Engineering: B

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Anomalous diffusion of nitrogen in nitrogen-implanted silicon

Cited by 33 publications

References 3 publications

Effect of Oxygen on the Diffusion of Nitrogen Implanted in Silicon

Effect of Oxygen on the Diffusion of Nitrogen Implanted in Silicon

Ab InitioIdentification of the Nitrogen Diffusion Mechanism in Silicon

Ab initio assisted process modeling for Si-based nanoelectronic devices

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