Anisotropic atomic layer etching of W using fluorine radicals/oxygen ion beam

Kim, Doo San; Kim, Ju Eun; Lee, Won Oh; Park, Jin Woo; Gill, You Jung; Jeong, Byeong Hwa; Yeom, Geun Young

doi:10.1002/ppap.201900081

Cited by 16 publications

(11 citation statements)

References 31 publications

(44 reference statements)

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“…In 2019, Kim et al suggested a method for fluorination oxidation, in which a layer of WF y was produced at room temperature using NF 3 plasma, and then the volatile WO x F y was made during the removal process by oxygen plasma reacting with the surface layer. Although the oxygen plasma would react with W, the exposure period of W was kept to less than or equal to 30 s/cycle by maintaining the oxygen plasma's voltage at 30 V [150].…”

Section: Signal Element Metalsmentioning

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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Section: Signal Element Metalsmentioning

confidence: 99%

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

Tsai

2022

Nanomaterials

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“…ALE can be accomplished using either plasma ALE or thermal ALE. − Plasma ALE produces anisotropic etching by employing energetic ions or neutrals to remove the modified surface species by a sputtering process . Plasma Si ALE is the model plasma ALE system that has been demonstrated using halide adsorption and Ar + ion exposures. − A variety of other plasma ALE processes have been developed for SiO 2 , , HfO 2 , Al 2 O 3 , InP, GaN, W, graphene, and polymers …”

Section: Introductionmentioning

confidence: 99%

“…2 Plasma Si ALE is the model plasma ALE system that has been demonstrated using halide adsorption and Ar + ion exposures. 5−8 A variety of other plasma ALE processes have been developed for SiO 2 , 9,10 HfO 2 , 11 Al 2 O 3 , 12 InP, 13 GaN, 14 W, 15 graphene, 16 and polymers. 17 Thermal atomic layer etching (ALE) produces isotropic etching using thermal reactions for etching.…”

Section: Introductionmentioning

confidence: 99%

Thermal Atomic Layer Etching of Gallium Oxide Using Sequential Exposures of HF and Various Metal Precursors

2020

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Gallium oxide (Ga 2 O 3 ) is a transparent semiconducting oxide with a large band gap that has applications for power electronics and optoelectronics. Ga 2 O 3 device fabrication requires etching for many processing steps. In this work, the thermal atomic layer etching (ALE) of Ga 2 O 3 was performed using hydrofluoric acid (HF) and a wide range of different metal precursors including BCl 3 , AlCl(CH 3 ) 2 , Al(CH 3 ) 3 , TiCl 4 , and Ga(N(CH 3 ) 2 ) 3 . Because Ga 2 O 3 is not a particularly stable oxide, the B-, Al-, or Ti-containing metal precursors can possibly convert the surface of Ga 2 O 3 to B 2 O 3 , Al 2 O 3 , or TiO 2 . These metal precursors can also provide Cl, CH 3 , and N(CH 3 ) 2 ligands for ligand-exchange reactions. Consequently, the thermal ALE of Ga 2 O 3 can occur via "conversion-etch" or fluorination and ligand-exchange reaction pathways. Using sequential HF and BCl 3 exposures and in situ spectroscopic ellipsometry techniques, Ga 2 O 3 etch rates were observed to vary from 0.59 to 1.35 Å/cycle at temperatures from 150 to 200 °C, respectively. The Ga 2 O 3 etch rates were also self-limiting versus HF and BCl 3 exposure. The lack of BCl 3 pressure dependence for the etch rates argued against the conversion-etch mechanism and in favor of a fluorination and ligand-exchange reaction pathway. In situ quartz crystal microbalance techniques also revealed that Ga 2 O 3 could be etched using sequential exposures of HF and various other metal precursors. Ga 2 O 3 etch rates at 250 °C were 1.2, 0.82, 0.85, and 0.23 Å/cycle for AlCl(CH 3 ) 2 , Al(CH 3 ) 3 , TiCl 4 , and Ga(N(CH 3 ) 2 ) 3 as the metal precursors, respectively. The mass changes during the individual exposures of HF and the AlCl(CH 3 ) 2 and Al(CH 3 ) 3 metal precursors argued for a fluorination and ligand-exchange mechanism. The AlCl(CH 3 ) 2 and Al(CH 3 ) 3 exposures may also lead to some conversion of Ga 2 O 3 to Al 2 O 3 . In contrast, the mass changes during the HF and TiCl 4 exposures were consistent with the conversion of the surface of Ga 2 O 3 to TiO 2 and then the spontaneous removal of the TiO 2 surface layer by HF. Distinctly different behavior was observed during the HF and Ga(N(CH 3 ) 2 ) 3 exposures. The large mass gain during the Ga(N(CH 3 ) 2 ) 3 exposures suggested that Ga(N(CH 3 ) 2 ) 3 can adsorb on the fluorinated Ga 2 O 3 surface prior to the ligand-exchange reaction. The wide range of metal precursors that can etch Ga 2 O 3 argues that the ability of these precursors to convert Ga 2 O 3 or to undergo ligand-exchange reactions provides multiple pathways for effective thermal Ga 2 O 3 ALE.

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“…While there are anisotropic W ALE processing methodologies available, 45 isotropic thermal ALE techniques are required to perform conformal etch in high aspect ratio structures. Indeed, progress toward the isotropic thermal ALE of metallic W has been reported by the groups of George and Parsons.…”

Section: Introductionmentioning

confidence: 99%

Mechanism of Thermal Atomic Layer Etch of W Metal Using Sequential Oxidation and Chlorination: A First-Principles Study

Natarajan

Nolan

Theofanis

et al. 2020

ACS Appl. Mater. Interfaces

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Thermal atomic layer etch (ALE) of W metal can be achieved by sequential self-limiting oxidation and chlorination reactions at elevated temperatures. In this paper, we analyze the reaction mechanisms of W ALE using the first-principles simulation. We show that oxidizing agents such as O 2 , O 3 , and N 2 O can be used to produce a WO x surface layer in the first step of an ALE process with ozone being the most reactive. While the oxidation pulse on clean W is very exergonic, our study suggests that runaway oxidation of W is not thermodynamically favorable. In the second ALE pulse, WCl 6 and Cl 2 remove the oxidized surface W atoms by the formation of volatile tungsten oxychloride (W x O y Cl z ) species. In this pulse, each adsorbed WCl 6 molecule was found to remove one surface W atom with a moderate energy cost. Our calculations further show that the desorption of the additional etch products is endothermic by up to 4.7 eV. Our findings are consistent with the high temperatures needed to produce ALE in experiments. In total, our quantum chemical calculations have identified the lowest energy pathways for ALE of tungsten metal along with the most likely etch products, and these findings may help guide the development of improved etch reagents.

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Anisotropic atomic layer etching of W using fluorine radicals/oxygen ion beam

Cited by 16 publications

References 31 publications

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

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

Thermal Atomic Layer Etching of Gallium Oxide Using Sequential Exposures of HF and Various Metal Precursors

Mechanism of Thermal Atomic Layer Etch of W Metal Using Sequential Oxidation and Chlorination: A First-Principles Study

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