Modeling of Si self-diffusion in SiO2: Effect of the Si/SiO2 interface including time-dependent diffusivity

Uematsu, Masashi; Kageshima, Hiroyuki; Takahashi, Yasuo; Fukatsu, Shigeto; Itoh, Kohei M.; Shiraishi, Kenji; Gösele, U.

doi:10.1063/1.1644623

Cited by 72 publications

(80 citation statements)

References 17 publications

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“…In Si-rich silica Uematsu 14 has shown that SiO is the main diffusing species; this may be the limiting process in pressure relief for our case. The diffusivities obtained in the present work, which vary from 10 -20 cm 2 /s to 10 -23 cm 2 /s for our range of temperatures, are considerably larger than those reported in previous studies of diffusion under equilibrium or near-equilibrium conditions.…”

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confidence: 60%

Mechanism of stress relaxation in Ge nanocrystals embedded in SiO2

Sharp

et al. 2005

Applied Physics Letters

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Ion-beam-synthesized 74 Ge nanocrystals embedded in an amorphous silica matrix exhibit large compressive stresses in the as-grown state. The compressive stress is determined quantitatively by evaluating the Raman line shift referenced to the line position of freestanding nanocrystals. Post-growth thermal treatments lead to stress reduction. The stress relief process is shown to be governed by the diffusive flux of matrix atoms away from the local nanocrystal growth region. A theoretical model that quantitatively describes this process is presented.

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confidence: 60%

Mechanism of stress relaxation in Ge nanocrystals embedded in SiO2

Sharp

et al. 2005

Applied Physics Letters

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“…It should be noted that KMC simulations with measured Si self-diffusivities [14,15] lead to too long annealing times or too high temperatures. Obviously, the diffusive Si mass transport by a mobile SiO 2 defect with local Si excess (that could either be named Si interstitial, SiO molecule [14], or oxygen vacancy [16]) does not necessarily follow the same mechanism than as the 28 SiO 2 / 30 SiO 2 interface broadening, which was analyzed in self-diffusivity studies. In this letter, the discrepancy between diffusive Si mass transport and Si self-diffusivity will not be discussed as our theoretical predictions aim at the reaction pathway of SiO x decomposition rather than at a quantitative prediction of annealing time and temperature.…”

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confidence: 99%

Multi-dot floating-gates for nonvolatile semiconductor memories: Their ion beam synthesis and morphology

Müller

Bonafos

Heinig

et al. 2004

Applied Physics Letters

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Scalability and performance of current flash memories can be improved substantially by replacing the floating poly-Si gate by a layer of Si dots. This multi-dot layer can be fabricated CMOS-compatibly in very thin gate oxide by ion beam synthesis (IBS). Here, we present both experimental and theoretical studies on IBS of multidot layers consisting of Si nanocrystals (NCs). The NCs are produced by ultra low energy Si + ion implantation, which causes a high Si supersaturation in the shallow implantation region. During post-implantation annealing, this supersaturation leads to phase separation of the excess Si from the SiO 2 . Till now, the study of this phase separation process suffered from the weak Z contrast between Si and SiO 2 in Transmission Electron Microscopy (TEM). Here, this imaging problem is resolved by mapping Si plasmon losses with a Scanning Transmission Electron Microscopy equipped with a parallel Electron Energy Loss Spectroscopy system (PEELS-STEM). Additionally, kinetic lattice Monte Carlo simulations of Si phase separation have been performed and compared with the experimental Si plasmon maps. It has been predicted theoretically that the morphology of the multidot Si floating-gate changes with increasing ion fluence from isolated, spherical NCs to percolated spinodal Si pattern. These patterns agree remarkably with PEELS-STEM images. However, the predicted fluence for spinodal patterns is lower than the experimental one. Because oxidants of the ambient atmosphere penetrate into the as-implanted SiO 2 , a substantial fraction of the implanted Si might be lost due to oxidation.Metal-Oxide-Silicon Field-Effect-Transistors (MOSFETs) with an electrically isolated ("floating") gate layer embedded in the gate oxide are currently used as flash memories. The replacement of this floating-gate by a layer of discrete Si nanocrystals (NCs) [1] improves the performance of flash memories substantially [2]. The reduced probability for a complete discharging of the multi-dot floating-gate by oxide defects allows thinner tunnel oxides. In turn, the floatinggate will be charged/discharged by quantum mechanical direct electron tunneling (instead of defect-generating FowlerNordheim tunneling). The memory operation voltage can be reduced and scalability is improved. Using ion beam synthesis, the multi-dot floating-gate can be fabricated along with standard CMOS processing [3]. Si + ions are implanted at ultra low energies into the gate oxide, causing there a high Si supersaturation. During post-implantation annealing, this Si supersaturation leads to phase separation of elemental Si from SiO 2 [4]. Imaging this phase separation process is difficult. Till now, Transmission Electron Microscopy (TEM) has suffered from weak Z contrast between Si and SiO 2 phases. Recently, this problem was partially overcome by Fresnel imaging using under-focused bright field conditions [5]. Thus, the distance of the layer of phase separated Si from the transistor channel could be determined [6,7]. However, this technique fails to resol...

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“…However, it is reported that in pillar oxidation, the total amount of Si is not preserved ("missing Si"). 4) Essentially, in the thermal oxidation of Si, some experimental 5,6) and theoretical studies [7][8][9][10] show that the self-diffusion of Si in SiO 2 is affected by SiO generated from the Si=SiO 2 interface. It is believed that the behavior of SiO is significantly related to three-dimensional oxidation.…”

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confidence: 99%

Oxygen concentration dependence of silicon oxide dynamical properties

Yajima¹,

Shiraishi²,

Endoh³

et al. 2018

Jpn. J. Appl. Phys.

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To understand oxidation in three-dimensional silicon, dynamic characteristics of a SiO x system with various stoichiometries were investigated. The calculated results show that the self-diffusion coefficient increases as oxygen density decreases, and the increase is large when the temperature is low. It also shows that the self-diffusion coefficient saturates, when the number of removed oxygen atoms is sufficiently large. Then, approximate analytical equations are derived from the calculated results, and the previously reported expression is confirmed in the extremely low-SiO-density range.

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Modeling of Si self-diffusion in SiO2: Effect of the Si/SiO2 interface including time-dependent diffusivity

Abstract: Structural relaxation and self-diffusion in covalent amorphous solids: Silicon nitride as a model system

Cited by 72 publications

References 17 publications

Mechanism of stress relaxation in Ge nanocrystals embedded in SiO2

Mechanism of stress relaxation in Ge nanocrystals embedded in SiO2

Multi-dot floating-gates for nonvolatile semiconductor memories: Their ion beam synthesis and morphology

Oxygen concentration dependence of silicon oxide dynamical properties

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