Chemical Kinetics of Chlorine in Electron Cyclotron Resonance Plasma Etching of Si

Ono, Ken; Tuda, Mutumi; Nishikawa, K.; Oomori, Tatsuo; Namba, Keisuke

doi:10.1143/jjap.33.4424

Cited by 40 publications

(34 citation statements)

References 13 publications

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“…These conditions are typical for Si etching in high-density plasmas, such as ICP and electron cyclotron resonance plasmas, [66][67][68] where the ion-enhanced reactions are assumed to be dominant mechanisms for etching. The results indicate that roughened features of the order of a few nm occur on etched surfaces, depending markedly on the angle h i of ion incidence.…”

Section: B Numerical Results and Discussionmentioning

confidence: 99%

“…17, and the calibration was made by filling the ICP plasma chamber with pure SiCl 4 gases at different pressures in the range P 0 ¼ 0.05-50 mTorr without discharge to estimate the absolute concentration of etch byproduct neutrals SiCl 4 in the plasma. 66,68 The experiments indicate that the peak absorbance of the 620-cm À1 SiCl 4 band and thus the concentration of SiCl 4 in the plasma increases with increasing bias power P rf or ion energy E i , corresponding to the increase in etch rate of Si with E i as shown in Fig. 17(a); in effect, the concentration of SiCl 4 or byproduct neutrals in the plasma during etching is more than 10% of the feedstock Cl 2 gas density, [SiCl 4 ]/[Cl 2 ] > 0.1, at E i > 200 eV.…”

Section: B Experimental Results and Discussionmentioning

confidence: 99%

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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: B Numerical Results and Discussionmentioning

confidence: 99%

Section: B Experimental Results and Discussionmentioning

confidence: 99%

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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“…[1][2][3][4][5][6][7][8] Electron cyclotron resonance ͑ECR͒ is one of such plasma sources giving high-density plasmas (10 11 -10 12 cm Ϫ3 )at low gas pressures (10 Ϫ3 -10 Ϫ4 Torr͒. [1][2][3][4]9,10 In such LPHD plasma etching, lower neutral-to-ion flux ratios (⌫ n /⌫ i Ͻ 10) are achieved onto substrate surfaces, along with lower sheath voltages or ion energies (E i Ͻ 100 eV͒, 9,10 leading to better etch anisotropy with higher selectivity and less damage. [1][2][3][4] Thus, the etch anisotropy may be largely limited by the ion temperature or their random motion in a plasma, because the sidewall etching resulting from spontaneous reactions of reactive neutrals and from obliquely incident ions scattered in a sheath is considerably reduced in LPHD plasmas.…”

Section: Introductionmentioning

confidence: 99%

Numerical study of the etch anisotropy in low-pressure, high-density plasma etching

Tuda

Nishikawa

Ono

1997

Journal of Applied Physics

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Modeling of fluorine-based high-density plasma etching of anisotropic silicon trenches with oxygen sidewall passivation J. Appl. Phys. 94, 6311 (2003); 10.1063/1.1621713Reduction of silicon recess caused by plasma oxidation during high-density plasma polysilicon gate etching Effects of gas distribution on polysilicon etch rate uniformity for a low pressure, high density plasma Evolution of etched profiles has been numerically studied during low-pressure, high-density ͑LPHD͒ plasma etching of Si in Cl 2 . The surface etch rates were calculated using a reaction model of synergism between incoming ions and neutral reactants, including the spread of ion angular distributions due to their thermal motions and the transport of neutrals arising from the reemission on surfaces in a microstructure. Etched profiles were then simulated using a so-called two-dimensional string algorithm to examine the effects of ion temperature kT i and energy ͑or sheath voltage͒ eV s on the etch anisotropy for different neutral-to-ion flux ratios ⌫ n /⌫ i toward the substrate. Numerical results indicated that in typical Cl 2 LPHD plasma etching environments, where the neutral-to-ion flux ratio is ⌫ n /⌫ i ϳ 1 and the ratio of sheath voltage to ion temperature is eV s /kT i ϳ 100, the chlorinated surface coverage is microscopically nonuniform in etched features: The coverage is very low at the bottom ͑␣ϳ0.1͒, whereas the sidewall surface ͑␣ϳ1͒ is almost saturated with neutrals. This microscopic nonuniformity of the coverage in etched features is the proposed mechanism responsible for the inversely tapered profiles that often occur in LPHD plasma etching. Additionally, the decrease in vertical etch rate in microstructures or the reactive-ion-etching lag due to neutral shadowing effects is also found to become significant in LPHD plasma etching. At such a low flux ratio of ⌫ n /⌫ i ϳ 1, more directional ions with a higher ratio of eV s /kT i տ 500 are required for the anisotropic etching; e.g., for an ion energy ͑or sheath voltage͒ of eV s ϭ 50 eV, the ion temperature in a plasma is required to be kT i Շ 0.1 eV.

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“…1,2 For etching of 0.1 m features in the future fabrication of ULSI, high density plasma sources at low pressure operation such as electron cyclotron resonance ͑ECR͒ plasma have been proposed. [3][4][5][6] ECR plasma etching has been reported to achieve a high anisotropy with a high etching rate. 3,4 In the etching process employing fluorocarbon plasmas, it has been recognized that polymer films are simultaneously deposited on the wafer surface during etching.…”

Section: Introductionmentioning

confidence: 99%

Fluorocarbon radicals and surface reactions in fluorocarbon high density etching plasma. I. O2 addition to electron cyclotron resonance plasma employing CHF3

Takahashi

Hori

Goto

1996

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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Chemical Kinetics of Chlorine in Electron Cyclotron Resonance Plasma Etching of Si

Cited by 40 publications

References 13 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

Numerical study of the etch anisotropy in low-pressure, high-density plasma etching

Fluorocarbon radicals and surface reactions in fluorocarbon high density etching plasma. I. O2 addition to electron cyclotron resonance plasma employing CHF3

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