Selectivity in atomically precise etching: Thermal atomic layer etching of a CoFeB alloy and its protection by MgO

Konh, Mahsa; Wang, Yang; Chen, Hang; Bhatt, Subhash; Xiao, John Q.; Teplyakov, Andrew V.

doi:10.1016/j.apsusc.2021.151751

Cited by 10 publications

(8 citation statements)

References 38 publications

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“…Samples were chlorinated in situ using a home-built solid-state electrochemical chlorine source based on silver chloride and cadmium chloride. 30,36,37 This source provides precise fluxes of Cl 2 gas molecules, and the corresponding surface coverage on a sample can be calibrated spectroscopically, as briefly described below. The organic compound was degassed by repeated dosing into the chamber, until the mass spectrum showed the expected m/z fragments.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

“…However, mixedligand compounds were formed for both light (B), and heavy (Co, Fe) elements in the form of M(acac) x Cl y as shown by temperature-programmed desorption (TPD) measurements. 29,30 In fact, the formation of volatile acetylacetonates of Co and Fe does occur, but at much higher temperatures compared to the ones used in ALE. 29,31−33 In a similar approach, one could start considering Cr(acac) 3 and H 3 PS 4 as potential products of the ALE of CrPS 4 .…”

Section: ■ Introductionmentioning

confidence: 99%

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Thermal Atomic Layer Etching Process for 2D van der Waals Material CrPS₄

Piña,

Whalen,

Xiao

et al. 2024

Chem. Mater.

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Preparing two-dimensional (2D) van der Waals materials with atomic-level precision remains a major hurdle, preventing both a number of fundamental explorations of quantum phenomena and a wider range of applications that can be based on a variety of their properties. It is especially challenging for tertiary materials, such as CrPS4, which cannot be produced by controlled deposition but could be managed by etching or thinning in a layer-by-layer approach. Thin flakes of this material can display ferromagnetic or antiferromagnetic behavior depending on the number of layers since the crystal exhibits A-type antiferromagnetic ordering. In order to understand the magnetism down to the monolayer limit and the dynamic excitations in magnons and excitons, and to eventually make devices based on this and similar materials viable, well-controlled layered structures must be produced. The existing methods for controlling CrPS4 thickness, such as mechanical and liquid exfoliation, are not well controlled and are prone to introducing damage to the crystal structure. In this study, we show that thermal atomic layer etching (ALE) can be used to controllably etch the 2D crystals of this material without noticeable contamination. As a starting point, CrPS4 flakes were mechanically exfoliated onto a solid substrate and mounted in an ultra-high vacuum chamber. ALE process consisted of a chlorine gas dose from a solid-state halogen doser followed by exposure to gas-phase acetylacetone (acacH). This ALE approach showed an etch rate of approximately 0.10 nm/cycle at 450 K, confirmed by atomic force microscopy. The etch rate is noticeably faster for the flakes with a large number of defects. The overall process is highly temperature-dependent with a narrow window for successful application.

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Section: ■ Experimental Sectionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Thermal Atomic Layer Etching Process for 2D van der Waals Material CrPS₄

Piña,

Whalen,

Xiao

et al. 2024

Chem. Mater.

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“…Most recently, Konh et al employed a continuous dosage of chlorine and 2,4-pentanedione (acetylacetone, acacH) to etch a CoFeB alloy film, and achieved an etching rate of 0.15 nm/cycle using the thermal dry etching method. It has also been established that MgO can have a protective effect on CoFeB alloy, allowing it to be employed in the manufacturing of MTJ [164]. The whole CoFeB alloy ALE process is shown in Figure 12.…”

Section: Alloysmentioning

confidence: 99%

Recent Progress of Atomic Layer Technology in Spintronics: Mechanism, Materials and Prospects

Tsai

2022

Nanomaterials

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The atomic layer technique is generating a lot of excitement and study due to its profound physics and enormous potential in device fabrication. This article reviews current developments in atomic layer technology for spintronics, including atomic layer deposition (ALD) and atomic layer etching (ALE). To begin, we introduce the main atomic layer deposition techniques. Then, in a brief review, we discuss ALE technology for insulators, semiconductors, metals, and newly created two-dimensional van der Waals materials. Additionally, we compare the critical factors learned from ALD to constructing ALE technology. Finally, we discuss the future prospects and challenges of atomic layer technology in the field of spinronics.

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“…Both ALD and ALE are based on two (or more) sequential self-limiting half-reactions, resulting in the final film thickness being dependent on the number of cycles performed. Increasingly, these atomic-scale processes are being utilized to deposit a wide variety of films for a growing number of applications. − …”

Section: Introductionmentioning

confidence: 99%

Surface Smoothing by Atomic Layer Deposition and Etching for the Fabrication of Nanodevices

Gerritsen

Chittock

Vandalon

et al. 2022

ACS Appl. Nano Mater.

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In many nano(opto)electronic devices, the roughness at surfaces and interfaces is of increasing importance, with roughness often contributing toward losses and defects, which can lead to device failure. Consequently, approaches that either limit roughness or smoothen surfaces are required to minimize surface roughness during fabrication. The atomic-scale processing techniques atomic layer deposition (ALD) and atomic layer etching (ALE) have experimentally been shown to smoothen surfaces, with the added benefit of offering uniform and conformal processing and precise thickness control. However, the mechanisms which drive smoothing during ALD and ALE have not been investigated in detail. In this work, smoothing of surfaces by ALD and ALE is studied using finite difference simulations that describe deposition/etching as a front propagating uniformly and perpendicular to the surface at every point. This uniform front propagation model was validated by performing ALD of amorphous Al 2 O 3 using the TMA/O 2 plasma. ALE from the TMA/SF 6 plasma was also studied and resulted in faster smoothing than predicted by purely considering uniform front propagation. Correspondingly, it was found that for such an ALE process, a second mechanism contributes to the smoothing, hypothesized to be related to curvature-dependent surface fluorination. Individually, the atomic-scale processing techniques enable smoothing; however, ALD and ALE will need to be combined to achieve thin and smooth films, as is demonstrated and discussed in this work for multiple applications.

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Selectivity in atomically precise etching: Thermal atomic layer etching of a CoFeB alloy and its protection by MgO

Cited by 10 publications

References 38 publications

Thermal Atomic Layer Etching Process for 2D van der Waals Material CrPS₄

Thermal Atomic Layer Etching Process for 2D van der Waals Material CrPS₄

Recent Progress of Atomic Layer Technology in Spintronics: Mechanism, Materials and Prospects

Surface Smoothing by Atomic Layer Deposition and Etching for the Fabrication of Nanodevices

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Selectivity in atomically precise etching: Thermal atomic layer etching of a CoFeB alloy and its protection by MgO

Cited by 10 publications

References 38 publications

Thermal Atomic Layer Etching Process for 2D van der Waals Material CrPS4

Thermal Atomic Layer Etching Process for 2D van der Waals Material CrPS4

Recent Progress of Atomic Layer Technology in Spintronics: Mechanism, Materials and Prospects

Surface Smoothing by Atomic Layer Deposition and Etching for the Fabrication of Nanodevices

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Product

Resources

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Thermal Atomic Layer Etching Process for 2D van der Waals Material CrPS₄

Thermal Atomic Layer Etching Process for 2D van der Waals Material CrPS₄