Conformality of Plasma-Assisted ALD: Physical Processes and Modeling

Abstract

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.

Monte Carlo simulations of atomic layer deposition on 3D large surface area structures: Required precursor exposure for pillar- versus hole-type structures

“…For arrays of holes, the exposure is independent of s 0 if H/w is large (above 50) and increases with decreasing s 0 if H/w is small. This result is in agreement with the earlier work by Elam et al 13 and Knoops et al, 22 where the reaction-limited (small H/w) and diffusion-limited (large H/w) regimes were distinguished. For structures with a small H/w ratio, the limiting factor during the deposition will be the sticking probability.…”

“…[12][13][14][15][16][17][18][19][20][21][22][23] At the start of the simulation, a MC particle is generated at a random position in a horizontal "source plane" positioned above the top surface of the 3D structures. The MC particle is emitted with a cosinedistributed random direction and its trajectory is calculated.…”

“…Among those, 2D models have been proposed to simulate thermal [12][13][14][15][16][17][18][19][20] and plasma-enhanced ALD in trenches. [21][22][23] This paper introduces a full 3D MC model, enabling simulation of thermal ALD processes in 3D structures. The model is applied here to compare ALD in an array of holes versus an array of pillars.…”

Аналитическая Модель Атомно-Слоевого Осаждения Тонких Пленок На Стенки Цилиндрических Отверстий С Высоким Аспектным Отношением

“…6 представлены кривые зависимости крити-ческого времени подачи прекурсора TEMAH от аспект-ного отношения цилиндрического отверстия в двойном логарифмическом масштабе аналогично работе [6]. Кри-тическое время на рис.…”

“…Поэтому исследова-ние зависимости времени подачи металлорганических и неорганических прекурсоров, достаточного для обра-зования конформной пленки, от величины аспектного отношения 3D-структур и коэффициента прилипания молекул прекурсора является предметом теоретических исследований ряда авторов [2][3][4][5][6][7][8][9]. Большинство работ в этой области представляет собой численное модели-рование методом Монте-Карло (см., например, [4][5][6]). Из теоретических работ наиболее известной является работа [3], в основе модели которой используется фор-мула для стационарного течения кнудсеновского газа по трубе, соединяющей две полости, а также равный единице коэффициент прилипания частиц прекурсора.…”