Atomic-scale cellular model and profile simulation of Si etching: Formation of surface roughness and residue

Tsuda, Hitoshi; Mori, Masahito; Takao, Yoshinori; Eriguchi, Koji; Ono, Ken

doi:10.1016/j.tsf.2009.11.043

Cited by 24 publications

(23 citation statements)

References 23 publications

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“…The ASCeM-3D methodology has been described in part in our previous papers, 46,47 together with the surface chemistry and kinetics concerned, which is basically an extension of the ASCeM-2D. [40][41][42][43][44][45] In more detail, the simulation domain is a square W ¼ 50 nm on a side with a depth of 630 nm, consisting of a number of small cubic cells of atomic size L ¼ q Si À1/3 ¼ 2.7 Å (185 Â 185 Â 2333 % 8 Â 10 7 cells in total), where q Si ¼ 5.0 Â 10 22 cm À3 is the atomic density of Si substrates. The substrates initially occupy a lower 620-nm-deep layer therein (or the substrate surfaces are initially flat, being located 10 nm downward from the top of the domain).…”

Section: Numerical Analysismentioning

confidence: 99%

“…It should be noted that the reflection and penetration of energetic ions incident on feature surfaces is a second one of the prominent features characterizing the ASCeM model; in practice, without the effects of ion reflection from surfaces on incidence, the ASCeM does not reproduce the evolution of 3D nanoscale surface features such as roughness and ripples as shown below and that of 2D nanoscale profile anomalies such as microtrench and micropillars as reported previously. [43][44][45] …”

Section: Surface Chemistry and Kineticsmentioning

confidence: 99%

“…21 We have developed a semi-empirical, atomic-scale cellular model (ASCeM) for simulating plasma-surface interactions and the resulting feature profile evolution during plasma etching of Si, based on the Monte Carlo algorithm with the cell removal method for interface evolution; [40][41][42][43][44][45][46][47] in effect, a two-dimensional ASCeM model (ASCeM-2D) reproduced the evolution of nanometer-scale profile anomalies on sidewalls and bottom surfaces of the feature, together with pattern-size or aspect-ratio dependences of them, during Si trench etching in Cl 2 and Cl 2 /O 2 plasmas. [40][41][42][43][44][45] However, the ASCeM-2D was found to be insufficient to reproduce the nanoscale surface roughness formed during plasma etching, probably because the formation and evolution of roughness is 3D as well as stochastic. 24,28 Therefore, we have recently developed a 3D ASCeM model (ASCeM-3D) to simulate the evolution of 3D feature profiles, including nanoscale surface features such as roughness, during Si etching in Cl-based plasmas.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Surface roughening and rippling during plasma etching of silicon: Numerical investigations and a comparison with experiments

Tsuda¹,

Nakazaki²,

Takao³

et al. 2014

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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Surface loss rates of H and Cl radicals in an inductively coupled plasma etcher derived from time-resolved electron density and optical emission measurementsModeling of fluorine-based high-density plasma etching of anisotropic silicon trenches with oxygen sidewall passivation Atomic-or nanometer-scale surface roughening and rippling during Si etching in high-density Cl 2 and Cl 2 /O 2 plasmas have been investigated by developing a three-dimensional atomic-scale cellular model (ASCeM-3D), which is a 3D Monte Carlo-based simulation model for plasma-surface interactions and the feature profile evolution during plasma etching. The model took into account the behavior of Cl þ ions, Cl and O neutrals, and etch products and byproducts of SiCl x and SiCl x O y in microstructures and on feature surfaces therein. The surface chemistry and kinetics included surface chlorination, chemical etching, ion-enhanced etching, sputtering, surface oxidation, redeposition of etch products desorbed from feature surfaces being etched, and deposition of etch byproducts coming from the plasma. The model also took into account the ion reflection or scattering from feature surfaces on incidence and/or the ion penetration into substrates, along with geometrical shadowing of the feature and surface reemission of neutrals. The simulation domain was taken to consist of small cubic cells of atomic size, and the evolving interfaces were represented by removing Si atoms from and/or allocating them to the cells concerned. Calculations were performed for square substrates 50 nm on a side by varying the ion incidence angle onto substrate surfaces, typically with an incoming ion energy, ion flux, and neutral reactant-to-ion flux ratio of E i ¼ 100 eV, C i 0 ¼ 1.0 Â 10 16 cm À2 s À1 , and C n 0 /C i 0 ¼ 100. Numerical results showed that nanoscale roughened surface features evolve with time during etching, depending markedly on ion incidence angle; in effect, at h i ¼ 0 or normal incidence, concavo-convex features are formed randomly on surfaces. On the other hand, at increased h i ¼ 45 or oblique incidence, ripple structures with a wavelength of the order of 15 nm are formed on surfaces perpendicularly to the direction of ion incidence; in contrast, at further increased h i ! 75 or grazing incidence, small ripples or slitlike grooves with a wavelength of <5 nm are formed on surfaces parallel to the direction of ion incidence. Such surface roughening and rippling in response to ion incidence angle were also found to depend significantly on ion energy and incoming fluxes of neutral reactants, oxygen, and etch byproducts. Two-dimensional power spectral density analysis of the roughened feature surfaces simulated was employed in some cases to further characterize the lateral as well as vertical extent of the roughness. The authors discuss possible mechanisms responsible for the formation and evolution of the surface roughness and ripples during plasma etching, including stochastic roughening, local micromasking, and effects of ion reflection, surface temp...

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Section: Numerical Analysismentioning

confidence: 99%

Section: Surface Chemistry and Kineticsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Surface roughening and rippling during plasma etching of silicon: Numerical investigations and a comparison with experiments

Tsuda¹,

Nakazaki²,

Takao³

et al. 2014

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

Self Cite

View full text Add to dashboard Cite

show abstract

“…Formation of surface ripples, waves, cones, and other patterns are often seen during low energy ion sputtering of inorganic materials. [141][142][143][144][145][146][147] Surface roughening of resists and underlayers during plasma etching using fluorocarbon gases has been attributed to localized fluorocarbon deposition. [136][137][138] A model of ripple formation on surfaces during low energy ion sputtering that considers the angular dependence of the sputter yield and surface diffusion has been proposed by Bradley and Harper 136 ͑see also below͒.…”

Section: Examples Of Plasma-induced Surface/line Edge Roughness In Rementioning

confidence: 99%

Plasma-polymer interactions: A review of progress in understanding polymer resist mask durability during plasma etching for nanoscale fabrication

Oehrlein

Phaneuf

Graves

2011

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

174

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Negative electron-beam resist hard mask ion beam etching process for the fabrication of nanoscale magnetic tunnel junctions Photolithographic patterning of organic materials and plasma-based transfer of photoresist patterns into other materials have been remarkably successful in enabling the production of nanometer scale devices in various industries. These processes involve exposure of highly sensitive polymeric nanostructures to energetic particle fluxes that can greatly alter surface and near-surface properties of polymers. The extension of lithographic approaches to nanoscale technology also increasingly involves organic mask patterns produced using soft lithography, block copolymer self-assembly, and extreme ultraviolet lithographic techniques. In each case, an organic film-based image is produced, which is subsequently transferred by plasma etching techniques into underlying films/substrates to produce nanoscale materials templates. The demand for nanometer scale resolution of image transfer protocols requires understanding and control of plasma/organic mask interactions to a degree that has not been achieved. For manufacturing of below 30 nm scale devices, controlling introduction of surface and line edge roughness in organic mask features has become a key challenge. In this article, the authors examine published observations and the scientific understanding that is available in the literature, on factors that control etching resistance and stability of resist templates in plasma etching environments. The survey of the available literature highlights that while overall resist composition can provide a first estimate of etching resistance in a plasma etch environment, the molecular structure for the resist polymer plays a critical role in changes of the morphology of resist patterns, i.e., introduction of surface roughness. Our own recent results are consistent with literature data that transfer of resist surface roughness into the resist sidewalls followed by roughness extension into feature sidewalls during plasma etch is a formation mechanism of rough sidewalls. The authors next summarize the results of studies on chemical and morphological changes induced in selected model polymers and advanced photoresist materials as a result of interaction with fluorocarbon/Ar plasma, and combinations of energetic ion beam/vacuum ultraviolet ͑UV͒ irradiation in an ultrahigh vacuum system, which are aimed at the fundamental origins of polymer surface roughness, and on establishing the respective roles of ͑a͒ polymer structure/chemistry and ͑b͒ plasma-process parameters on the consequences of the plasma-polymer interactions. Plasma induced resist polymer modifications include formation of a thin ͑ϳ1-3 nm͒ dense graphitic layer at the polymer surface due to ion bombardment and deeper-lying modifications produced by plasma-generated vacuum ultraviolet ͑VUV͒ irradiation. The relative importance of the latter depends strongly on initial polymer structure, whereas the ion bombardment induced modified layers are similar for ...

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“…Of course, in case if there is only a single material present, then this intrinsic error could be mitigated. Many cellular-model simulators (see, for example, (25)(26)(27)(28)(29)(30)) had opted for the use of only the smallest possible cell sizes (the atomic-scale cellular model), such that each cell contains only a single molecule. In this case, the whole algorithm for chemical reactions is significantly simplified.…”

Section: Introductionmentioning

confidence: 99%

Feature Profile 2D and 3D Simulation with Etching, Deposition, and Implantation Processes

Moroz

2013

ECS Trans.

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Interaction of plasmas with solid materials during materials processing involves many phenomena. In most cases, processes of etching, deposition, and implantation go on at the same time, and the final result depends on the balance between those processes. Here, the current approach and progress in feature profile simulations via FPS3D are presented. The FPS3D code provides a convenient environment for simulations of processing for any set of materials and fluxes, as well as for any surface and volume reactions. Moreover, the code can treat "recipes" with arbitrary number of steps, each step having its own set of fluxes. To properly compute effects of implantation, the code estimates penetration depths for all used gaseous species interacting with all used solid materials. We report here on the current status of FPS3D as well as on a supporting molecular dynamics code, MDSS, which is mainly used to prepare data for the input and chemistry files for FPS3D.

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Atomic-scale cellular model and profile simulation of Si etching: Formation of surface roughness and residue

Cited by 24 publications

References 23 publications

Surface roughening and rippling during plasma etching of silicon: Numerical investigations and a comparison with experiments

Surface roughening and rippling during plasma etching of silicon: Numerical investigations and a comparison with experiments

Plasma-polymer interactions: A review of progress in understanding polymer resist mask durability during plasma etching for nanoscale fabrication

Feature Profile 2D and 3D Simulation with Etching, Deposition, and Implantation Processes

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