Photo-assisted etching of silicon in chlorine- and bromine-containing plasmas

Zhu, Weiye; Sridhar, Shyam; Liu, Lei; Hernández, Eduardo A. Lugo; Donnelly, Vincent M.; Economou, Demetre J.

doi:10.1063/1.4878895

Cited by 28 publications

(13 citation statements)

References 70 publications

(96 reference statements)

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“…Examples include spontaneous chemical etching of the substrate (e.g. Cl atom etching of heavily n-doped poly-silicon [17]), photo-assisted etching [18], substrate sputtering, or excessive roughening of the surface.…”

Section: Introductionmentioning

confidence: 99%

Atomic layer etching of silicon dioxide using alternating C₄F₈and energetic Ar⁺plasma beams

Kaler

Lou

Donnelly

et al. 2017

J. Phys. D: Appl. Phys.

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Atomic layer etching (ALE) of SiO 2 was studied by alternating exposure of a 5 nm-thick SiO 2 film on Si substrate to (1) a plasma beam emanating from a cC 4 F 8 inductively coupled plasma (ICP), to grow a fluorocarbon (FC) film composed mainly of CF 2 , and (2) an energetic (130 eV) Ar + ion beam extracted from a separate Ar ICP. In situ x-ray photoelectron spectroscopy was used to analyze the chemical composition of the near-surface region, and to quantify the thickness of the FC and SiO 2 films. A very thin (3-6 Å), near self-limiting thickness CF 2-rich FC film was found to deposit on the SiO 2 surface with exposure to continuous or pulsed power C 4 F 8 plasma beams, under conditions that generated a large relative flux of CF 2. Following this, a FC film of similar composition grew at ~10 times slower rate. Exposure of the thin film to the Ar + beam led to removal of 1.9 Å SiO 2. An estimated yield of 1.3 SiO 2 molecules-per-Ar + was found for a single ALE step. The rate of 1.9 Å/cycle persisted over multiple ALE cycles, but a carbon-rich residual film did build up. This film can be removed by a brief exposure to an O 2-containing plasma beam.

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Section: Introductionmentioning

confidence: 99%

Atomic layer etching of silicon dioxide using alternating C₄F₈and energetic Ar⁺plasma beams

Kaler

Lou

Donnelly

et al. 2017

J. Phys. D: Appl. Phys.

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“…Donnelly's and Economou's groups 46,142 reported on the importance of photo-assisted etching of silicon in chlorineand bromine-containing plasmas for very low ion bombardment energies using nearly mono-energetic ion energy distributions. At this time the mechanistic origin of this observation is not well understood.…”

Section: Issues and Needsmentioning

confidence: 99%

Atomic Layer Etching at the Tipping Point: An Overview

Oehrlein

Metzler

2015

ECS J. Solid State Sci. Technol.

225

162

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The ability to achieve near-atomic precision in etching different materials when transferring lithographically defined templates is a requirement of increasing importance for nanoscale structure fabrication in the semiconductor and related industries. The use of ultra-thin gate dielectrics, ultra thin channels, and sub-20 nm film thicknesses in field effect transistors and other devices requires near-atomic scale etching control and selectivity. There is an emerging consensus that as critical dimensions approach the sub-10 nm scale, the need for an etching method corresponding to Atomic Layer Deposition (ALD), i.e. Atomic Layer Etching (ALE), has become essential, and that the more than 30-year quest to complement/replace continuous directional plasma etching (PE) methods for critical applications by a sequence of individual, self-limited surface reaction steps has reached a crucial stage. A key advantage of this approach relative to continuous PE is that it enables optimization of the individual steps with regard to reactant adsorption, self-limited etching, selectivity relative to other materials, and damage of critical surface layers. In this overview we present basic approaches to ALE of materials, discuss similarities/crucial differences relative to thermal and plasma-enhanced ALD, and then review selected results on ALE of materials aimed at pattern transfer. The overview concludes with a discussion of opportunities and challenges ahead. A requirement of increasing importance for nanoscale device fabrication is the ability to achieve atomic scale etching control and materials selectivity during pattern transfer.1-8 An etching method corresponding to Atomic Layer Deposition (ALD), i.e. Atomic Layer Etching (ALE), is expected to satisfy these needs as critical dimensions continue to shrink below the 10 nm scale.Demonstrations of self-limited dry etching methods capable of near-atomic resolution have a long history in the dry etching community and a brief review will be presented below. Key challenges for these approaches have been specialized equipment, long process times and low throughput.9,10 However, a recent demonstration using a commercial plasma etch tool 10 and activities within the dry etching community 11 provide indications that the situation has changed, and that we may have reached for ALE the Tipping Point which Gladwell defined as the "the moment of critical mass, the threshold, the boiling point" when "ideas and products and messages and behaviors spread like viruses do".12 This is due to several factors, including unprecedented demands on dry etching technology introduced by the semiconductor device evolution according to Moore's law that can be satisfied by atomic layer etching, advanced capabilities in plasma etch, and the existence of a critical level of information on plasma etch and ALD methods as applied in the semiconductor fabrication space.In this article we will provide a review of background of these approaches, and focus on issues that have to be overcome for widespread implement...

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“…Because of the lower reactivity of bromine towards silicon compared to fluorine, the etching of very thin layers can be more properly controlled with bromine-based plasmas. [1][2][3][4][5][6][7] A bromine-containing gas that is often used for silicon etching is HBr, which is commonly mixed with Cl 2 and/or CF 4 . [8][9][10][11][12][13] Furthermore, HBr can also be combined with a noble gas like helium, to tune the ratio between physical ion sputtering and chemical etching, or with O 2 , for controlling the anisotropy during etching.…”

Section: Introductionmentioning

confidence: 99%

Role of vibrationally excited HBr in a HBr/He inductively coupled plasma used for etching of silicon

Tinck

Bogaerts

2016

J. Phys. D: Appl. Phys.

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In this work, the role of vibrationally excited HBr (HBr (vib) ) is computationally investigated for a HBr/He inductively coupled plasma applied for Si etching. It is found that at least 50% of all dissociations of HBr occur through HBr (vib) . This additional dissociation pathway through HBr (vib) makes the plasma significantly more atomic. It also results in a slightly higher electron temperature (i.e., about 0.2 eV higher compared to simulation results where HBr (vib) is not included), as well as a higher gas temperature (i.e., about 50 K higher than without including HBr (vib) ), due to the enhanced Franck-Condon heating through HBr (vib) dissociation, at the conditions investigated. Most importantly, the calculated etch rate with HBr (vib) included in the model is a factor 3 higher than in the case without HBr (vib) , due to the higher fluxes of etching species (i.e., H and Br), while the chemical composition of the wafer surface shows no significant difference. Our calculations clearly show the importance of including HBr (vib) for accurate modeling of HBr-containing plasmas.

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Photo-assisted etching of silicon in chlorine- and bromine-containing plasmas

Cited by 28 publications

References 70 publications

Atomic layer etching of silicon dioxide using alternating C₄F₈and energetic Ar⁺plasma beams

Atomic layer etching of silicon dioxide using alternating C₄F₈and energetic Ar⁺plasma beams

Atomic Layer Etching at the Tipping Point: An Overview

Role of vibrationally excited HBr in a HBr/He inductively coupled plasma used for etching of silicon

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Photo-assisted etching of silicon in chlorine- and bromine-containing plasmas

Cited by 28 publications

References 70 publications

Atomic layer etching of silicon dioxide using alternating C4F8and energetic Ar+plasma beams

Atomic layer etching of silicon dioxide using alternating C4F8and energetic Ar+plasma beams

Atomic Layer Etching at the Tipping Point: An Overview

Role of vibrationally excited HBr in a HBr/He inductively coupled plasma used for etching of silicon

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Atomic layer etching of silicon dioxide using alternating C₄F₈and energetic Ar⁺plasma beams

Atomic layer etching of silicon dioxide using alternating C₄F₈and energetic Ar⁺plasma beams