Saturation profile based conformality analysis for atomic layer deposition: aluminum oxide in lateral high-aspect-ratio channels

Yim, Jihong; Ylivaara, Oili; Ylilammi, Markku; Korpelainen, Virpi; Haimi, Eero; Verkama, Emma; Utriainen, Mikko; Puurunen, Riikka L.

doi:10.1039/d0cp03358h

Cited by 30 publications

(103 citation statements)

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“…To study the film conformality, plasma ALD of SiO 2 and TiO 2 was carried out on all-silicon microscopic lateral-high-aspect-ratio (LHAR) trench structures (PillarHall LHAR generation 3 and 4), which are described in detail in previous publications (see, for instance, Gao et al 16 and Yim et al 17 ). The main advantage of these structures is that the horizontally oriented trenches have extremely high aspect ratios of up to 10 000, such that film growth in practice never reaches the end of the trench.…”

Section: Methodsmentioning

confidence: 99%

Oxygen Recombination Probability Data for Plasma-Assisted Atomic Layer Deposition of SiO₂ and TiO₂

et al. 2021

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Atomic layer deposition (ALD) can provide nanometer-thin films with excellent conformality on demanding three-dimensional (3D) substrates. This also holds for plasma-assisted ALD, provided that the loss of reactive radicals through surface recombination is sufficiently low. In this work, we determine the surface recombination probability r of oxygen radicals during plasma ALD of SiO 2 and TiO 2 for substrate temperatures from 100 to ∼240 °C and plasma pressures from 12 to 130 mTorr (for SiO 2 ). For both processes, the determined values of r are very low, i.e., ∼10 –4 or lower, and decrease with temperature and pressure down to ∼10 –5 within the studied ranges. Accordingly, deposition on trench structures with aspect ratios (ARs) of <200 is typically not significantly limited by recombination and obtaining excellent film conformality is relatively facile. For higher AR values, e.g., approaching 1000, the plasma time needed to reach saturation increases exponentially and becomes increasingly dependent on the process conditions and the corresponding value of r . Similar dependence on process conditions can be present for plasma ALD of other materials as well, where, in certain cases, film growth is already recombination-limited for AR values of ∼10. Radical recombination data and trends as provided by this work are valuable for optimizing plasma ALD throughput and feasibility for high-AR applications and can also serve as input for modeling of radical recombination mechanisms.

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Section: Methodsmentioning

confidence: 99%

Oxygen Recombination Probability Data for Plasma-Assisted Atomic Layer Deposition of SiO₂ and TiO₂

et al. 2021

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“…The width W (m) of the microchannel is orders of magnitude larger than H, and the length L (m) is considered infinite (the channel end effects are not considered). While the model has been constructed with lateral HAR (LHAR) structures in mind, 35,36 it is indifferent to the orientation of the structure and thus describes vertical trenches (and any other orientation) as well.…”

Section: Basic Ald Process and Geometry Assumptionsmentioning

confidence: 99%

“…11,12,29,30,32,33 Recently, microscopic lateral high-aspect-ratio (LHAR) test channels have emerged for thickness profile measurements. 18,[34][35][36] Such LHAR structures simplify conformality analysis: after ALD, the roof of the structure can be removed, exposing the film to detailed analysis. [35][36][37] Further, a method has been developed by Arts et al 30 to be used in conjunction with microscopic LHAR test channels, where the sticking coefficient c can be calculated from the slope [at surface coverage 𝜃 (-) of 1/2] of the Type 1 normalized thickness profile [Figure 1(b)] through a simple square root relation.…”

Section: Introductionmentioning

confidence: 99%

“…18,[34][35][36] Such LHAR structures simplify conformality analysis: after ALD, the roof of the structure can be removed, exposing the film to detailed analysis. [35][36][37] Further, a method has been developed by Arts et al 30 to be used in conjunction with microscopic LHAR test channels, where the sticking coefficient c can be calculated from the slope [at surface coverage 𝜃 (-) of 1/2] of the Type 1 normalized thickness profile [Figure 1(b)] through a simple square root relation. 30 This slope method was derived empirically from the diffusion-reaction model of Yanguas-Gil and Elam at free molecular flow conditions.…”

Section: Introductionmentioning

confidence: 99%

“…The classifications of thickness profiles and the regions are as in ref. 36, except that here we use the term thickness profile instead of saturation profile.…”

Section: Introductionmentioning

confidence: 99%

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Conformality of atomic layer deposition in microchannels: impact of process parameters on the simulated thickness profile

Yim

Verkama

Velasco

et al. 2021

Preprint

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Unparalleled conformality is driving ever new applications for atomic layer deposition (ALD), a thin film growth method based on repeated self-terminating gas-solid reactions. In this work, we re-implemented a diffusion-reaction model from the literature to simulate the propagation of film growth in wide microchannels and used that model to explore trends in both the thickness profile as a function of process parameters and different diffusion regimes. In the model, partial pressure of ALD reactant was analytically approximated. Simulations were made as function of kinetic and process parameters such as temperature, (lumped) sticking coefficient, molar mass of the ALD reactant, reactant’s exposure time and pressure, total pressure, density of the grown material, and growth per cycle (GPC) of the ALD process. Increasing the molar mass and the GPC, for example, resulted in a decreasing penetration depth into the microchannel. The influence of the mass and size of the inert gas molecules on the thickness profile depended on the diffusion regime (free molecular flow vs. transition flow). The modelling was compared to a recent slope method to extract the sticking coefficient. The slope method gave systematically somewhat higher sticking coefficient values compared to the input sticking coefficient values; potential reasons behind the observed differences are discussed.

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Atomic Layer Deposition

Ommen

Goulas

Puurunen

2021

Kirk-Othmer Encyclopedia of Chemical Technology

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Atomic layer deposition (ALD) is a gas‐phase method to grow layers of solid materials with subnanometer precision. It has been invented independently in the Soviet Union in the 1960s under the name molecular layering, and in the 1970s in Finland under the name atomic layer epitaxy. ALD relies on alternatingly exposing a surface to gaseous reactants—separated by a purge step—that react in a self‐terminating manner. This article introduces the fundamentals of the surface chemistry of ideal ALD, including saturating and irreversible reactions, growth per cycle, monolayer concepts relevant to ALD, typical surface reaction mechanisms, saturation‐limiting factors, growth modes, area‐selective ALD, growth kinetics, and conformality. It also discusses typical deviations from ideal ALD. Over the years, many different ALD process chemistries have been developed. A range of reactor systems is available, depending on the type of substrate and required productivity. ALD is broadly applicable in practice since it couples nanoscale precision with a good scalability and can be used to deposit a large variety of materials. In recent years, the interest in ALD has been growing strongly. The most important sector regarding commercial applications of ALD is currently the semiconductor industry.

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Saturation profile based conformality analysis for atomic layer deposition: aluminum oxide in lateral high-aspect-ratio channels

Abstract: Atomic layer deposition (ALD) raises global interest through its unparalleled conformality. This work describes new microscopic lateral high-aspect-ratio (LHAR) test structures for conformality analysis of ALD. The LHAR structures are...

Cited by 30 publications

References 53 publications

Oxygen Recombination Probability Data for Plasma-Assisted Atomic Layer Deposition of SiO₂ and TiO₂

Oxygen Recombination Probability Data for Plasma-Assisted Atomic Layer Deposition of SiO₂ and TiO₂

Conformality of atomic layer deposition in microchannels: impact of process parameters on the simulated thickness profile

Atomic Layer Deposition

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Saturation profile based conformality analysis for atomic layer deposition: aluminum oxide in lateral high-aspect-ratio channels

Abstract: Atomic layer deposition (ALD) raises global interest through its unparalleled conformality. This work describes new microscopic lateral high-aspect-ratio (LHAR) test structures for conformality analysis of ALD. The LHAR structures are...

Cited by 30 publications

References 53 publications

Oxygen Recombination Probability Data for Plasma-Assisted Atomic Layer Deposition of SiO2 and TiO2

Oxygen Recombination Probability Data for Plasma-Assisted Atomic Layer Deposition of SiO2 and TiO2

Conformality of atomic layer deposition in microchannels: impact of process parameters on the simulated thickness profile

Atomic Layer Deposition

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Product

Resources

About

Oxygen Recombination Probability Data for Plasma-Assisted Atomic Layer Deposition of SiO₂ and TiO₂

Oxygen Recombination Probability Data for Plasma-Assisted Atomic Layer Deposition of SiO₂ and TiO₂