KINETICS OF HYDROGEN ATOM RECOMBINATION ON SURFACES<sup>1</sup>

Wood, Bernard J.; Wise, Henry

doi:10.1021/j100828a015

Cited by 161 publications

(53 citation statements)

References 2 publications

(2 reference statements)

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“…19 Wood and Wise reported that most metals have a fairly constant recombination probability for hydrogen radicals over a wide temperature range. 20 The surface conditions during ALD can differ from those in the reported studies, affecting the value of r.…”

Section: Plasma-assisted Aldmentioning

confidence: 77%

Conformality of Plasma-Assisted ALD: Physical Processes and Modeling

Knoops

Langereis

Sanden

et al. 2010

J. Electrochem. Soc.

173

116

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Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers)Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. For plasma-assisted atomic layer deposition ͑ALD͒, reaching conformal deposition in high aspect ratio structures is less straightforward than for thermal ALD due to surface recombination loss of plasma radicals. To obtain a detailed insight into the consequences of this additional radical loss, the physical processes in plasma-assisted ALD affecting conformality were identified and investigated through Monte Carlo simulations. The conformality was dictated by the recombination probability r, the reaction probability s, and the diffusion rate of particles. When recombination losses play a role, the saturation dose depended strongly on the value of r. For the deposition profiles, a minimum at the bottom of trench structures was observed ͑before reaching saturation͒, which was more pronounced with larger values of r. In turn, three deposition regimes could be identified, i.e., a reaction-limited regime, a diffusion-limited regime, and a new regime that is recombination-limited. For low values of r, conformal deposition in high aspect ratio structures can still be achieved, as observed for several metal oxides, even for aspect ratios as large as 30. For high surface recombination loss probabilities, as appears to be the case for many metals, achieving a reasonable conformality becomes challenging, especially for aspect ratios Ͼ10.

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Section: Plasma-assisted Aldmentioning

confidence: 77%

Conformality of Plasma-Assisted ALD: Physical Processes and Modeling

Knoops

Langereis

Sanden

et al. 2010

J. Electrochem. Soc.

173

116

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“…Note that the surface temperature can also affect the value of r, for example, a significant temperature dependence was reported for oxygen radicals on silica, 305 whereas the temperature dependence of H radicals on metals was less prominent. 306 The influence of the value of r can be illustrated by the results obtained from simple two-dimensional Monte Carlo simulations, in which the evolution of the deposition profile within a trench of high aspect ratio was studied as a function of the incoming radical flux. 304,337 This was achieved by considering only the plasma exposure step during a single ALD cycle.…”

Section: Challenges Of Plasma-assisted Aldmentioning

confidence: 99%

Plasma-Assisted Atomic Layer Deposition: Basics, Opportunities, and Challenges

Profijt

Potts

Sanden

et al. 2011

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

729

537

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Plasma-assisted atomic layer deposition (ALD) is an energy-enhanced method for the synthesis of ultra-thin films with Å-level resolution in which a plasma is employed during one step of the cyclic deposition process. The use of plasma species as reactants allows for more freedom in processing conditions and for a wider range of material properties compared with the conventional thermally-driven ALD method. Due to the continuous miniaturization in the microelectronics industry and the increasing relevance of ultra-thin films in many other applications, the deposition method has rapidly gained popularity in recent years, as is apparent from the increased number of articles published on the topic and plasma-assisted ALD reactors installed. To address the main differences between plasma-assisted ALD and thermal ALD, some basic aspects related to processing plasmas are presented in this review article. The plasma species and their role in the surface chemistry are addressed and different equipment configurations, including radical-enhanced ALD, direct plasma ALD, and remote plasma ALD, are described. The benefits and challenges provided by the use of a plasma step are presented and it is shown that the use of a plasma leads to a wider choice in material properties, substrate temperature, choice of precursors, and processing conditions, but that the processing can also be compromised by reduced film conformality and plasma damage. Finally, several reported emerging applications of plasma-assisted ALD are reviewed. It is expected that the merits offered by plasma-assisted ALD will further increase the interest of equipment manufacturers for developing industrial-scale deposition configurations such that the method will find its use in several manufacturing applications.

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“…Approximately 1 out of every 5 atoms which collide with the surface undergo recombination. (The hydrogen content of the palladium was not noted during this study (27) and the efficiency may increase as the hydrogen content increases since the surface coverage increases with the bulk content.) Because of the rapid absorption which takes place via H atom generation it can be concluded that a significant fraction of the hydrogen atoms do not recombine but undergo the transition to the absorbed state.…”

Section: Discussionmentioning

confidence: 74%

“…Palladium has a very high efficiency for the H-H recombination reaction (27). Approximately 1 out of every 5 atoms which collide with the surface undergo recombination.…”

Section: Discussionmentioning

confidence: 99%

The Reaction of Hydrogen Atoms with Palladium and its Alloys

Oates¹,

Flanagan²

1975

Can. J. Chem.

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H atoms, which have been generated in the gas phase, have been allowed to interact with palladium metal and several of its substitutional f.c.c. alloys. It has been found that quite high concentrations of interstitial hydrogen can be introduced in this manner even in the absence of poisons such as H2S. The kinetics of hydrogen uptake have been followed as a function of the hydrogen content of the palladium. The kinetics of the subsequent loss of hydrogen from the palladium have been investigated. Mechanisms for the surface reactions of hydrogen on palladium are discussed.

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KINETICS OF HYDROGEN ATOM RECOMBINATION ON SURFACES¹

Cited by 161 publications

References 2 publications

Conformality of Plasma-Assisted ALD: Physical Processes and Modeling

Conformality of Plasma-Assisted ALD: Physical Processes and Modeling

Plasma-Assisted Atomic Layer Deposition: Basics, Opportunities, and Challenges

The Reaction of Hydrogen Atoms with Palladium and its Alloys

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KINETICS OF HYDROGEN ATOM RECOMBINATION ON SURFACES1

Cited by 161 publications

References 2 publications

Conformality of Plasma-Assisted ALD: Physical Processes and Modeling

Conformality of Plasma-Assisted ALD: Physical Processes and Modeling

Plasma-Assisted Atomic Layer Deposition: Basics, Opportunities, and Challenges

The Reaction of Hydrogen Atoms with Palladium and its Alloys

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KINETICS OF HYDROGEN ATOM RECOMBINATION ON SURFACES¹