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Soares J, Mane AU, Choudhury D, Letourneau S, Hues SM, Elam JW, Graugnard E. Thermal Atomic Layer Etching of MoS 2 Using MoF 6 and H 2O. Chem Mater 2023; 35:927-936. [PMID: 36818590 PMCID: PMC9933903 DOI: 10.1021/acs.chemmater.2c02549] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/18/2022] [Revised: 12/23/2022] [Indexed: 06/18/2023]
Abstract
Two-dimensional (2D) layered materials offer unique properties that make them attractive for continued scaling in electronic and optoelectronic device applications. Successful integration of 2D materials into semiconductor manufacturing requires high-volume and high-precision processes for deposition and etching. Several promising large-scale deposition approaches have been reported for a range of 2D materials, but fewer studies have reported removal processes. Thermal atomic layer etching (ALE) is a scalable processing technique that offers precise control over isotropic material removal. In this work, we report a thermal ALE process for molybdenum disulfide (MoS2). We show that MoF6 can be used as a fluorination source, which, when combined with alternating exposures of H2O, etches both amorphous and crystalline MoS2 films deposited by atomic layer deposition. To characterize the ALE process and understand the etching reaction mechanism, in situ quartz crystal microbalance (QCM), Fourier transform infrared (FTIR), and quadrupole mass spectrometry (QMS) experiments were performed. From temperature-dependent in situ QCM experiments, the mass change per cycle was -5.7 ng/cm2 at 150 °C and reached -270.6 ng/cm2 at 300 °C, nearly 50× greater. The temperature dependence followed Arrhenius behavior with an activation energy of 13 ± 1 kcal/mol. At 200 °C, QCM revealed a mass gain following exposure to MoF6 and a net mass loss after exposure to H2O. FTIR revealed the consumption of Mo-O species and formation of Mo-F and MoF x =O species following exposures of MoF6 and the reverse behavior following H2O exposures. QMS measurements, combined with thermodynamic calculations, supported the removal of Mo and S through the formation of volatile MoF2O2 and H2S byproducts. The proposed etching mechanism involves a two-stage oxidation of Mo through the ALE half-reactions. Etch rates of 0.5 Å/cycle for amorphous films and 0.2 Å/cycle for annealed films were measured by ex situ ellipsometry, X-ray reflectivity, and transmission electron microscopy. Precisely etching amorphous films and subsequently annealing them yielded crystalline, few-layer MoS2 thin films. This thermal MoS2 ALE process provides a new mechanism for fluorination-based ALE and offers a low-temperature approach for integrating amorphous and crystalline 2D MoS2 films into high-volume device manufacturing with tight thermal budgets.
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Affiliation(s)
- Jake Soares
- Micron
School of Material Science and Engineering, Boise State University, 1910 University Dr., Boise, Idaho83725, United
States
| | - Anil U. Mane
- Applied
Materials Division, Argonne National Laboratory, 9700 S Cass Avenue, Lemont, Illinois60439, United States
| | - Devika Choudhury
- Applied
Materials Division, Argonne National Laboratory, 9700 S Cass Avenue, Lemont, Illinois60439, United States
| | - Steven Letourneau
- Applied
Materials Division, Argonne National Laboratory, 9700 S Cass Avenue, Lemont, Illinois60439, United States
| | - Steven M. Hues
- Micron
School of Material Science and Engineering, Boise State University, 1910 University Dr., Boise, Idaho83725, United
States
| | - Jeffrey W. Elam
- Applied
Materials Division, Argonne National Laboratory, 9700 S Cass Avenue, Lemont, Illinois60439, United States
| | - Elton Graugnard
- Micron
School of Material Science and Engineering, Boise State University, 1910 University Dr., Boise, Idaho83725, United
States
- Center
for Advanced Energy Studies, Idaho
Falls, Idaho83401, United States
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Hues SM, Wyatt JR, Colton RJ, Black BH. Effect of hydrogen substitution on the mass spectrometry and size-exclusion chromatography of perfluorinated polyether fluids as determined by time-of-flight secondary ion mass spectrometry. Anal Chem 2002. [DOI: 10.1021/ac00209a021] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Gillen G, M Hues S. Doped gelatin films as a model matrix for molecular secondary ion mass spectrometry studies of biological soft tissue. J Am Soc Mass Spectrom 1993; 4:419-423. [PMID: 24234939 DOI: 10.1016/1044-0305(93)85007-k] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/1992] [Revised: 12/18/1992] [Accepted: 01/05/1993] [Indexed: 06/02/2023]
Abstract
Porcine gelatin films doped with a number of biological compounds at various concentrations and prepared by spin-casting have been used as model biological tissue matrices for studying organic ion emission in molecular secondary ion mass spectrometry. For many compounds, portions of the working curves were found to be linear over several orders of magnitude in concentration. Detection limits for the, analyzed compounds were in the parts per million range for several organic salt compounds but high (0.1 wt%) for others. Owing to the presence of a significant chemical background, the poorest detection limits were generally obtained from compounds with low molecular weights. Secondary ion yield matrix effects, indicated by a reduction in ionization efficiency at higher concentrations, were observed for several organic salt compounds.
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Affiliation(s)
- G Gillen
- Surface and Microanalysis Science Division, National Institute of Standards and Technology, 20899, Gaithersburg, MD
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Gillen G, Phelps JM, Nelson RW, Williams P, Hues SM. Secondary ion yield matrix effects in SIMS depth profiles of Si/Ge multilayers. SURF INTERFACE ANAL 1989. [DOI: 10.1002/sia.740141114] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Hues SM, Bhadra R, Grimsditch M, Fullerton E, Schuller IK. Effect of high-energy ion irradiation on the elastic moduli of Ag/Co superlattices. Phys Rev B Condens Matter 1989; 39:12966-12968. [PMID: 9948185 DOI: 10.1103/physrevb.39.12966] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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