Diffusion of Iron in Silicon Dioxide

Ramappa, Deepak A.; Henley, Worth B.

doi:10.1149/1.1392548

Cited by 50 publications

(43 citation statements)

References 18 publications

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“…They found that in bonded SOI wafers the diffusivity of iron was 2 ϫ 10 Ϫ14 cm 2 /s at 1050°C, and 10 Ϫ15 cm 2 /s at 900°C. These values are close to Fe diffusivity in silica glass measured by Atkinson et al, 27 and to the values of Ramappa et al, 28 who reported the equation D ϭ 4 ϫ 10 Ϫ8 exp(Ϫ1.51/kT). For comparison, the diffusivity of iron in crystalline silicon is in the range of 10 Ϫ6 cm 2 /s at the same temperatures.…”

Section: Modeling Resultssupporting

confidence: 90%

Modeling of Competitive Gettering of Iron in Silicon Integrated Circuit Technology

Istratov

Huber²,

Weber

2003

J. Electrochem. Soc.

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Areas of heavy doping, implantation damage, and lattice strains, which are part of any silicon-integrated circuit device, can provide efficient traps for metals and compete for impurities with intentionally introduced gettering sites. In this article we introduce the concept of competitive gettering between gettering sites and devices and perform modeling of competitive gettering in p/p ϩ epi wafers, wafers with internal gettering sites, and silicon-on-insulator ͑SOI͒ wafers. The impact of the substrate resistivity, density of oxide precipitates, and denuded zone/epi layer width is analyzed for a wide span of cooling ranges. It is found that the major consequence of the effect of gettering by devices is that by the end of cooling, the metal concentration in the device area can substantially exceed its average concentration in the wafer, and device yield could degrade. This can be prevented by optimizing the substrate gettering properties. Although fast cooling rates inherent in rapid thermal processing represent a challenge for gettering, it is shown that optimized gettering can perform well even if the wafer is cooled in a rapid thermal processing system at a rate between 5 and 100 degrees per second. Our modeling results indicate that SOI wafers behave differently than epitaxial or bulk wafers because the buried oxide layer provides a barrier for diffusion of metals between the device area and the substrate. The last section of the article presents an experimental proof of principle of competitive gettering.Gettering has been used in semiconductor processing for over forty years ͑see, for example, Ref. 1͒. The physical principles of gettering are well understood, a high density of precipitation sites or enhanced metal solubility in the gettering layer creates a metal concentration gradient from the near-surface ͑device͒ layer towards the gettering layer, and stimulates diffusion of the dissolved metals to the gettering sites ͑see recent reviews 2-4 for a detailed discussion͒. Although the principle of gettering is simple, its efficiency may vary in a wide range depending on the properties of the gettering layer, initial distribution and concentration of metals in the wafer, the range of temperatures of the thermal processing, and finally, the cooling rate. Due to the complexity of these factors, gettering has always been a practical art, whereby gettering properties of each shipment of wafers were individually tailored to a specific process or customer. Optimization was usually achieved by trying wafers with different properties and different thermal histories ͑or even cut from different parts of the ingot͒ on a production line until the most robust type of wafers was identified.The necessity of fine-tuning the gettering properties of the wafer to individual processes led to customer-tailored wafer specifications. In the last decade, a significant effort was made to engineer processes which allow one to form highly efficient gettering sites independent of the initial wafer properties ͑e.g., magic denuded zones,...

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Section: Modeling Resultssupporting

confidence: 90%

Modeling of Competitive Gettering of Iron in Silicon Integrated Circuit Technology

Istratov

Huber²,

Weber

2003

J. Electrochem. Soc.

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“…This is because previous experimental data indicated that the diffusion of metallic atoms in SiO 2 and SiN x follows Fick's law of [17][18][19] The Gaussian distribution of the chemical composition at the interface in our unannealed samples should be attributed to the roughness at the HfO 2 / SiO 2 ͑SiON͒ interfaces and Hf diffusion that occurred during sample fabrication, such as during the Hf deposition. 12 Because the shape of the electron probe also affects the measured chemical distribution, the distribution is a convolution of the electron probe shape and the chemical distribution profile due to the roughness and the Hf diffusion at the interface.…”

Section: Discussionmentioning

confidence: 60%

The influence of incorporated nitrogen on the thermal stability of amorphous HfO2 and Hf silicate

Ikarashi

Watanabe

Masuzaki

et al. 2006

Journal of Applied Physics

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We investigated the thermal stability of a N-incorporated amorphous Hf silicate film in terms of Hf diffusion in the film using high-angle annular-dark-field scanning transmission electron microscopy. We first examined HfxSi1−xO2 (x=0.5,1.0) films with and without N incorporation. Our analysis showed that N incorporation (15at.% of N) into the Hf0.5Si0.5O2 film significantly suppressed chemical component separation during annealing at 1000°C. In contrast, clear separation of Hf-rich and Hf-poor (SiO2-rich) regions occurred in the Hf0.5Si0.5O2 film without N incorporation. In addition, HfO2 crystalline particle formation was observed in the HfO2 films with and without N incorporation (25at.% of N). These results strongly suggest that Si–N bonding in the N-incorporated Hf0.5Si0.5O2 film, rather than Hf–N chemical bonding, is the main cause of the suppression of the chemical component separation and HfO2 crystallization. Second, we examined Hf diffusion in a SiO2 film with and without N incorporation and found that the N incorporation significantly reduced the Hf diffusion. We therefore infer that the suppression of the chemical component separation in the N-incorporated Hf silicate film can be explained in terms of the suppression of Hf diffusion by the Si–O, N network in the N-incorporated Hf silicate film.

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“…This agrees with the work by Smith et al, 44 where the solubilities of iron in Si and SiO 2 were found to be similar. However, Ramappa and Henley 45 reported a strong tendency of iron to segregate into the SiO 2 layer. As discussed by Istratov et al in a review paper of iron in silicon, 1 the interaction of iron with SiO 2 and Si is complex and may involve chemical binding reactions that are dependent on the specific process conditions.…”

Section: Discussionmentioning

confidence: 99%

Gettering of interstitial iron in silicon by plasma-enhanced chemical vapour deposited silicon nitride films

Liu

Sun

Markevich

et al. 2016

Journal of Applied Physics

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It is known that the interstitial iron concentration in silicon is reduced after annealing silicon wafers coated with plasma-enhanced chemical vapour deposited (PECVD) silicon nitride films. The underlying mechanism for the significant iron reduction has remained unclear and is investigated in this work. Secondary ion mass spectrometry (SIMS) depth profiling of iron is performed on annealed iron-contaminated single-crystalline silicon wafers passivated with PECVD silicon nitride films. SIMS measurements reveal a high concentration of iron uniformly distributed in the annealed silicon nitride films. This accumulation of iron in the silicon nitride film matches the interstitial iron loss in the silicon bulk. This finding conclusively shows that the interstitial iron is gettered by the silicon nitride films during annealing over a wide temperature range from 250 °C to 900 °C, via a segregation gettering effect. Further experimental evidence is presented to support this finding. Deep-level transient spectroscopy analysis shows that no new electrically active defects are formed in the silicon bulk after annealing iron-containing silicon with silicon nitride films, confirming that the interstitial iron loss is not due to a change in the chemical structure of iron related defects in the silicon bulk. In addition, once the annealed silicon nitride films are removed, subsequent high temperature processes do not result in any reappearance of iron. Finally, the experimentally measured iron decay kinetics are shown to agree with a model of iron diffusion to the surface gettering sites, indicating a diffusion-limited iron gettering process for temperatures below 700 °C. The gettering process is found to become reaction-limited at higher temperatures.

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Diffusion of Iron in Silicon Dioxide

Cited by 50 publications

References 18 publications

Modeling of Competitive Gettering of Iron in Silicon Integrated Circuit Technology

Modeling of Competitive Gettering of Iron in Silicon Integrated Circuit Technology

The influence of incorporated nitrogen on the thermal stability of amorphous HfO2 and Hf silicate

Gettering of interstitial iron in silicon by plasma-enhanced chemical vapour deposited silicon nitride films

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