Surface diffusion model accounting for the temperature dependence of tungsten etching characteristics in a SF6 magnetoplasma

Bounasri, F.; Pelletier, Jacques; Moisan, M.; Chaker, Mohamed

doi:10.1116/1.590010

Cited by 7 publications

(10 citation statements)

References 41 publications

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“…z E-mail: jacobus@dsif.fee.unicamp.br to N F as can be expected 5 within the whole range of plasma parameters investigated, see Fig. 1.…”

Section: Resultssupporting

confidence: 63%

“…For tungsten, the atomic fluorine adsorption was shown to be monolayer-like, 5 with the adsorption rate being proportional to s(1 Ϫ ⌰), where s is the sticking coefficient for fluorine atoms on a bare surface. Due to a strong repulsive interaction between fluorine atoms, adsorption of fluorine is strongly reduced when the surface coverage is close to saturation (⌰ Ϸ 1).…”

Section: Resultsmentioning

confidence: 99%

“…[1][2][3] To avoid this, various techniques have been employed including passivation of sidewalls by carbon-containing species using polymerforming gases 1,4 or substrate cooling. 5 Anisotropic etching was obtained in SF 6 /Ar using low-pressure high-density etchers characterized by relatively high ion-to-radical flux ratios. 2 Usually low anisotropy is achieved with conventional low-density ͑i.e., a low ion-to-radical flux ratio͒ RIE etchers.…”

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confidence: 99%

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Study of Conditions for Anisotropic Plasma Etching of Tungsten and Tungsten Nitride Using SF[sub 6]/Ar Gas Mixtures

Reyes-Betanzo¹,

Moshkalyov²,

Ramos

et al. 2002

J. Electrochem. Soc.

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Results of the study of reactive ion etching of tungsten, tungsten nitride, and silicon in SF 6 /Ar gas mixtures are presented. For plasma diagnostics, optical emission spectroscopy ͑actinometry͒ was used. Using the actinometry technique, it was possible to show that etching mechanisms were different for Si-F and W-F chemistries. Anisotropic etching of tungsten/tungsten nitride using conventional reactive ion etcher has been obtained, and conditions of achieving anisotropic etching have been analyzed. A correlation is found between anisotropy of tungsten etching and the ratio of Si/W etch rates. Mechanisms of fluorine redistribution between the bottom/sidewall surfaces due to surface diffusion and/or reflection are proposed as possible reasons for the observed correlation.The use of tungsten and tungsten nitride thin films in microfabrication attracts much attention due to their high thermal stability, good adherence ͑for tungsten nitride͒, and low sheet resistance. Due to the continuous shrinking of microdevice dimensions, demands on the dimensional control and anisotropy of etch profiles are constantly increasing. For etching of W and WN x films, fluorinecontaining gases ͑in particular SF 6 or CF 4 ͒ are commonly used which provide high etch rates. 1-4 For conventional reactive ion etching ͑RIE͒ reactors, considerable undercutting or formation of concave sidewall profiles due to spontaneous etching of tungsten by fluorine in fluorine-containing plasmas was usually reported. 1-3 To avoid this, various techniques have been employed including passivation of sidewalls by carbon-containing species using polymerforming gases 1,4 or substrate cooling. 5 Anisotropic etching was obtained in SF 6 /Ar using low-pressure high-density etchers characterized by relatively high ion-to-radical flux ratios. 2 Usually low anisotropy is achieved with conventional low-density ͑i.e., a low ion-to-radical flux ratio͒ RIE etchers. In some cases, anisotropic etching in RIE experiments was obtained. 3 However, conditions for anisotropic tungsten etching still are not well understood. The objective of the present study was to find and to model conditions of anisotropic etching of W and WN x in a SF 6 /Ar plasma at normal temperatures, without applying sidewall passivation techniques. A conventional RIE medium pressure reactor was used in this study.The characteristic of a RIE process is a specific combination of chemical and physical ͑ion-induced͒ etching mechanisms. The relative contribution of chemical/physical components of the process determines the profile and anisotropy of the etched features. For a better understanding of etching mechanisms it is important to characterize quantitatively particle fluxes at the surface. Here, in order to characterize the density of fluorine radicals in the plasma, an optical emission spectroscopy ͑the actinometry technique͒ 6 was employed.In order to provide considerable variation of radical/ion fluxes to the processed surfaces, the SF 6 /Ar flow ratio was varied widely in the experiments. The speci...

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“…z E-mail: jacobus@dsif.fee.unicamp.br to N F as can be expected 5 within the whole range of plasma parameters investigated, see Fig. 1.…”

Section: Resultssupporting

confidence: 63%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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Study of Conditions for Anisotropic Plasma Etching of Tungsten and Tungsten Nitride Using SF[sub 6]/Ar Gas Mixtures

Reyes-Betanzo¹,

Moshkalyov²,

Ramos

et al. 2002

J. Electrochem. Soc.

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“…As reported by some researchers, [5][6][7] the addition of O 2 to SF 6 for tungsten etching improves etching verticality through the formation of a less volatile WO x F y layer on the tungsten surface. In the etching of tungsten-coated samples patterned with a NEB31 resist, the addition of oxygen to the SF 6 etch chemistry showed some influence on sidewall protection and thus on verticality, but eroded the resist etching mask seriously even at very small O 2 concentrations (e.g., a gas ratio of SF 6 : O 2 ¼ 30 : 3 sccm-the minimum controllable O 2 flow rate with the etching system).…”

Section: Resultsmentioning

confidence: 74%

Optical Emission Spectrometry of Plasma in Low-Damage Sub-100 nm Tungsten Gate Reactive Ion Etching Process for Compound Semiconductor Transistors

Li¹,

Zhou²,

Wilkinson³

et al. 2006

Jpn. J. Appl. Phys.

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In this study, we investigate in situ optical emission spectra from plasma in the reactive ion etching (RIE) of tungsten, a suitable candidate for gate metallization in compound-semiconductor-based high-mobility channel devices. This results in a detailed understanding of the effects of etching parameters vital to reducing etch induced damage and improving etching performance. A SF6 based chemistry was used with other functional gases, such as N2, O2, and CHF3. Van de Pauw (VdP) structures on GaAs based high electron mobility transistor (HEMT) layer structures were used for evaluating plasma-induced damage in the RIE process. The optimised process results in a maximum increase of 15% in the sheet resistance of the semiconductor material. Etched tungsten line widths down to 25 nm with well controlled profile were obtained by adjusting the etching conditions based on the understanding of the etching mechanism.

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“…Finally, rather than determining the activation energies from the variation of the lateral etch rate V L measured by scanning electron microscopy (SEM) with the risk of introducing systematic errors on their absolute values from one measurement to the other, it is therefore preferable to determine the activation energies from the ratio V L / V V of lateral and vertical etch rates directly measured by SEM on the etch profiles . Another advantage of using the V L / V V ratio is that, just as the anisotropy A (cf.…”

Section: Questions Specific To the Diversity Of Polymers In Plasma Etmentioning

confidence: 99%

Oxygen plasma etching of hydrocarbon‐like polymers: Part II experimental validation

Bès

Koo

Phan

et al. 2018

Plasma Processes & Polymers

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The objective in Part II is to verify whether the model developed in Part I for the etching of polymers in oxygen plasmas can apply to all types of polymers. The experimental parametric study of the etching of different polymers in oxygen plasmas and under distinct operating conditions confirms that their etching kinetics follow the general laws derived from the modeling: 1) under identical operating conditions, the etch rates of polymer films with equal carbon concentration are the same and 2) the activation energies for spontaneous etching are shown to be effectively independent of the plasma operating conditions, and their values, common to all polymers, are 0.76 ± 0.05 eV for CO 2 desorption and 0.40 ± 0.05 eV for CO desorption.

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Surface diffusion model accounting for the temperature dependence of tungsten etching characteristics in a SF6 magnetoplasma

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Cited by 7 publications

References 41 publications

Study of Conditions for Anisotropic Plasma Etching of Tungsten and Tungsten Nitride Using SF[sub 6]/Ar Gas Mixtures

Study of Conditions for Anisotropic Plasma Etching of Tungsten and Tungsten Nitride Using SF[sub 6]/Ar Gas Mixtures

Optical Emission Spectrometry of Plasma in Low-Damage Sub-100 nm Tungsten Gate Reactive Ion Etching Process for Compound Semiconductor Transistors

Oxygen plasma etching of hydrocarbon‐like polymers: Part II experimental validation

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