Low energy electron-enhanced etching of Si(100) in hydrogen/helium direct-current plasma

Gillis, H. P.; Choutov, D. A.; Steiner, P.; Piper, J. D. A.; Crouch, J. H.; Dove, Patricia M.; Martin, K. P.

doi:10.1063/1.114000

Cited by 36 publications

(11 citation statements)

References 4 publications

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“…electron force field | fermionic molecular dynamics | floating Gaussian orbitals G reat uncertainties remain concerning how highly excited states (∼100 eV) induced by energetic photons, electrons, ions, or plasmas induce chemical processes at surfaces (1), particularly in large covalent systems (2) relevant to semiconductor fabrication (3). To determine the electron dynamics and atomic mechanisms involved in large-scale highly excited processes, we have developed the electron force field (eFF), a molecular dynamics model that includes electrons.…”

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confidence: 99%

Mechanisms of Auger-induced chemistry derived from wave packet dynamics

Goddard

2009

Proc. Natl. Acad. Sci. U.S.A.

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To understand how core ionization and subsequent Auger decay lead to bond breaking in large systems, we simulate the wave packet dynamics of electrons in the hydrogenated diamond nanoparticle C 197 H 112 . We find that surface core ionizations cause emission of carbon fragments and protons through a direct Auger mechanism, whereas deeper core ionizations cause hydrides to be emitted from the surface via remote heating, consistent with results from photon-stimulated desorption experiments [Hoffman A, Laikhtman A, (2006) J Phys Condens Mater 18:S1517-S1546]. This demonstrates that it is feasible to study the chemistry of highly excited large-scale systems using simulation and analysis tools comparable in simplicity to those used for classical molecular dynamics.electron force field | fermionic molecular dynamics | floating Gaussian orbitals G reat uncertainties remain concerning how highly excited states (∼100 eV) induced by energetic photons, electrons, ions, or plasmas induce chemical processes at surfaces (1), particularly in large covalent systems (2) relevant to semiconductor fabrication (3). To determine the electron dynamics and atomic mechanisms involved in large-scale highly excited processes, we have developed the electron force field (eFF), a molecular dynamics model that includes electrons. We previously used eFF to compute the thermodynamic properties of warm dense hydrogen, and found excellent agreement with high-level theory, as well as both static compression and dynamic shock experiments (4).We report now the application of eFF to study Auger processes in a hydrogenated diamond nanoparticle C 197 H 112 (Fig. 1A). In the Auger process, ionization of a core electron leads to the collapse of a valence electron into the core hole, together with the ejection of another valence electron, all over several femtoseconds (5). During and after this time, secondary processes occur, causing protons, hydrides, and other species to desorb from hydrogen-terminated surfaces (1). We study the coupled electron-nuclear dynamics of both the primary Auger and accompanying secondary processes, ionizing core electrons both at the diamondoid surface and at different depths below the surface. In this way, we determine how the distance over which an Auger excitation relaxes and propagates affects the energies of electrons and composition of atomic species desorbed from the surface.In eFF, all electrons, valence and core, are modeled as spherical Gaussian wave packets:while nuclei are modeled as classical charged particles moving in the mean field of the electrons. The positions x i and sizes s i of the electrons are continuously variable, giving them the flexibility to participate in covalent, ionic, multicenter, and even metallic bonding; p x,i and p s,i are the corresponding conjugate momenta. This description is well-suited for representing highly excited systems, where electron density maxima and spreads may be distorted from equilibrium positions and values.Substituting the above expression into the time-dependent Schr...

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confidence: 99%

Mechanisms of Auger-induced chemistry derived from wave packet dynamics

Goddard

2009

Proc. Natl. Acad. Sci. U.S.A.

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“…While the effect of photons and metastable species is more elusive, their effect on the surface chemistry should not be ignored as they can provide energy at the surface of the film to promote cross-linking reactions leading to hydrogen desorption and bond reconstruction. Few studies report on the importance of electrons, in particular on etching processes [18] thought to be relevant to µc-Si:H formation. Last but not least, silicon clusters and nanocrystals produced in the plasma can also contribute to deposition.…”

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confidence: 98%

New approaches for the production of nano‐, micro‐, and polycrystalline silicon thin films

Cabarrocas

2004

phys. stat. sol. (c)

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We review current models and propose new approaches for the production of silicon thin films by low temperature plasma processes. Growth models have often been borrowed from those developed for hydrogenated amorphous silicon and are based on surface diffusion of SiH 3 . However, in situ growth studies have also pointed out the fast diffusion of hydrogen and its role in the crystallization of the film through subsurface reactions. Moreover, ions and silicon nanocrystals can also play a crucial role in microcrystalline silicon deposition. We show that ion bombardment is responsible for the formation of a disorderd subsurface layer while deposition on a cooled substrate allows us to trap the silicon nanocrystals and to prevent their growth, thus leading to nanocrystalline thin films. The deposition at 200 °C on substrates with a low density of surface defects allows for the surface mobility of the nanocrystals and their agglomeration to form large grains, thus resulting in polycrystalline silicon thin films.

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“…Previous studies using LE4 on other semiconductor materials including GaAs, GaN, and Si have yielded smooth and stoichiometric surfaces with minimal surface damage and high-resolution pattern transfer. [9][10][11] The LE4 experiments were performed on nonpatterned or photoresist (PR) mesa-patterned Hg 1−x Cd x Te (x ∼ 0.3) epitaxial layers grown by molecularbeam epitaxy (MBE) on a (211)-oriented Cd 1−y Zn y Te substrate or a (211)-oriented CdTe (grown by MBE)/ Si substrate. The PR layer was ∼2-m thick, and the mesa trench was ∼8-m wide.…”

Section: Introductionmentioning

confidence: 99%

Low-energy electron-enhanced etching of HgCdTe

Kim

Koga

Gillis

et al. 2003

Journal of Elec Materi

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Low-energy electron-enhanced etching (LE4) is applied to HgCdTe to eliminate ion-induced surface damage. First, LE4 results for patterned samples are illustrated. The LE4 mechanism is understood from a mechanistic study in terms of three etch variables: direct current (DC) bias, gas composition, and sample temperature. For this paper, the effects of DC bias (electron energy) and gas composition (CH 4 concentration) are summarized qualitatively, followed by quantitative evidence. Etch rate, the amount of polymer, surface stoichiometry, and surface roughness have specific relations with each etch variable under competition between pure LE4 and polymer deposition.

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Low energy electron-enhanced etching of Si(100) in hydrogen/helium direct-current plasma

Cited by 36 publications

References 4 publications

Mechanisms of Auger-induced chemistry derived from wave packet dynamics

Mechanisms of Auger-induced chemistry derived from wave packet dynamics

New approaches for the production of nano‐, micro‐, and polycrystalline silicon thin films

Low-energy electron-enhanced etching of HgCdTe

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