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Zaera F. The surface chemistry of the atomic layer deposition of metal thin films. NANOTECHNOLOGY 2024; 35:362001. [PMID: 38888294 DOI: 10.1088/1361-6528/ad54cb] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2024] [Accepted: 06/06/2024] [Indexed: 06/20/2024]
Abstract
In this perspective we discuss the progress made in the mechanistic studies of the surface chemistry associated with the atomic layer deposition (ALD) of metal films and the usefulness of that knowledge for the optimization of existing film growth processes and for the design of new ones. Our focus is on the deposition of late transition metals. We start by introducing some of the main surface-sensitive techniques and approaches used in this research. We comment on the general nature of the metallorganic complexes used as precursors for these depositions, and the uniqueness that solid surfaces and the absence of liquid solvents bring to the ALD chemistry and differentiate it from what is known from metalorganic chemistry in solution. We then delve into the adsorption and thermal chemistry of those precursors, highlighting the complex and stepwise nature of the decomposition of the organic ligands that usually ensued upon their thermal activation. We discuss the criteria relevant for the selection of co-reactants to be used on the second half of the ALD cycle, with emphasis on the redox chemistry often associated with the growth of metallic films starting from complexes with metal cations. Additional considerations include the nature of the substrate and the final structural and chemical properties of the growing films, which we indicate rarely retain the homogeneous 2D structure often aimed for. We end with some general conclusions and personal thoughts about the future of this field.
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Affiliation(s)
- Francisco Zaera
- Department of Chemistry, University of California, Riverside, CA 92521, United States of America
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Young MJ, Bedford NM, Yanguas-Gil A, Letourneau S, Coile M, Mandia DJ, Aoun B, Cavanagh AS, George SM, Elam JW. Probing the Atomic-Scale Structure of Amorphous Aluminum Oxide Grown by Atomic Layer Deposition. ACS APPLIED MATERIALS & INTERFACES 2020; 12:22804-22814. [PMID: 32309922 DOI: 10.1021/acsami.0c01905] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Atomic layer deposition (ALD) is a well-established technique for depositing nanoscale coatings with pristine control of film thickness and composition. The trimethylaluminum (TMA) and water (H2O) ALD chemistry is inarguably the most widely used and yet to date, we have little information about the atomic-scale structure of the amorphous aluminum oxide (AlOx) formed by this chemistry. This lack of understanding hinders our ability to establish process-structure-property relationships and ultimately limits technological advancements employing AlOx made via ALD. In this work, we employ synchrotron high-energy X-ray diffraction (HE-XRD) coupled with pair distribution function (PDF) analysis to characterize the atomic structure of amorphous AlOx ALD coatings. We combine ex situ and in operando HE-XRD measurements on ALD AlOx and fit these experimental data using stochastic structural modeling to reveal variations in the Al-O bond length, Al and O coordination environment, and extent of Al vacancies as a function of growth conditions. In particular, the local atomic structure of ALD AlOx is found to change with the substrate and number of ALD cycles. The observed trends are consistent with the formation of bulk Al2O3 surrounded by an O-rich surface layer. We deconvolute these data to reveal atomic-scale structural information for both the bulk and surface phases. Overall, this work demonstrates the usefulness of HE-XRD and PDF analysis in improving our understanding of the structure of amorphous ALD thin films and provides a pathway to evaluate how process changes impact the structure and properties of ALD films.
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Affiliation(s)
- Matthias J Young
- Department of Biomedical, Biological, and Chemical Engineering, University of Missouri, Columbia 65211, Missouri, United States
- Department of Chemistry, University of Missouri, Columbia 65211, Missouri, United States
- Applied Materials Division, Argonne National Laboratory, Lemont 60439, Illinois, United States
| | - Nicholas M Bedford
- School of Chemical Engineering, University of New South Wales, Sydney 2052, New South Wales, Australia
| | - Angel Yanguas-Gil
- Applied Materials Division, Argonne National Laboratory, Lemont 60439, Illinois, United States
| | - Steven Letourneau
- Applied Materials Division, Argonne National Laboratory, Lemont 60439, Illinois, United States
| | - Matthew Coile
- Applied Materials Division, Argonne National Laboratory, Lemont 60439, Illinois, United States
| | - David J Mandia
- Applied Materials Division, Argonne National Laboratory, Lemont 60439, Illinois, United States
| | - Bachir Aoun
- X-ray Sciences Division, Argonne National Laboratory, Lemont 60439, Illinois, United States
| | - Andrew S Cavanagh
- Department of Chemistry, University of Colorado Boulder, Boulder 80309, Colorado, United States
| | - Steven M George
- Department of Chemistry, University of Colorado Boulder, Boulder 80309, Colorado, United States
| | - Jeffrey W Elam
- Applied Materials Division, Argonne National Laboratory, Lemont 60439, Illinois, United States
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Chen B, Qin X, Lien C, Bouman M, Konh M, Duan Y, Teplyakov AV, Zaera F. Thermal Chemistry of Metal Organic Compounds Adsorbed on Oxide Surfaces. Organometallics 2019. [DOI: 10.1021/acs.organomet.9b00636] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Bo Chen
- Department of Chemistry, University of California, Riverside, California 92521, United States
| | - Xiangdong Qin
- Department of Chemistry, University of California, Riverside, California 92521, United States
| | - Clinton Lien
- Department of Chemistry, University of California, Riverside, California 92521, United States
| | - Menno Bouman
- Department of Chemistry, University of California, Riverside, California 92521, United States
| | - Mahsa Konh
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Yichen Duan
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Andrew V. Teplyakov
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Francisco Zaera
- Department of Chemistry, University of California, Riverside, California 92521, United States
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Cao Y, Chen B, Guerrero-Sánchez J, Lee I, Zhou X, Takeuchi N, Zaera F. Controlling Selectivity in Unsaturated Aldehyde Hydrogenation Using Single-Site Alloy Catalysts. ACS Catal 2019. [DOI: 10.1021/acscatal.9b02547] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Yueqiang Cao
- Department of Chemistry and UCR Center for Catalysis, University of California, Riverside, California 92521, United States
- State Key Laboratory of Chemical Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, China
| | - Bo Chen
- Department of Chemistry and UCR Center for Catalysis, University of California, Riverside, California 92521, United States
| | - Jonathan Guerrero-Sánchez
- Centro de Nanociencias y Nanotecnología, Universidad Nacional Autónoma de México, Apartado Postal 14, Ensenada, Baja California 22800, Mexico
| | - Ilkeun Lee
- Department of Chemistry and UCR Center for Catalysis, University of California, Riverside, California 92521, United States
| | - Xinggui Zhou
- State Key Laboratory of Chemical Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, China
| | - Noboru Takeuchi
- Department of Chemistry and UCR Center for Catalysis, University of California, Riverside, California 92521, United States
- Centro de Nanociencias y Nanotecnología, Universidad Nacional Autónoma de México, Apartado Postal 14, Ensenada, Baja California 22800, Mexico
| | - Francisco Zaera
- Department of Chemistry and UCR Center for Catalysis, University of California, Riverside, California 92521, United States
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Lien C, Konh M, Chen B, Teplyakov AV, Zaera F. Gas-Phase Electron-Impact Activation of Atomic Layer Deposition (ALD) Precursors: MeCpPtMe 3. J Phys Chem Lett 2018; 9:4602-4606. [PMID: 30067025 DOI: 10.1021/acs.jpclett.8b02125] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The use of gas-phase electron-impact activation of metalorganic complexes to facilitate atomic layer depositions (ALD) was tested for the case of (methylcyclopentadienyl)Pt(IV) trimethyl (MeCpPtMe3) on silicon oxide films. Uptake enhancements of more than 1 order of magnitude were calculated from X-ray photoelectron spectroscopy (XPS) data. On the basis of the measured C:Pt ratios, the surface species were estimated to mainly consist of MeCpPt moieties, likely because of the prevalent formation of [MeCpPtMe x- nH]+ ions after gas-phase ionization (as determined by mass spectrometry). Counterintuitively, more extensive adsorption was observed on thick SiO2 films than on the native thin SiO2 film that forms on Si(100) wafers, despite the former having virtually no surface OH groups. The adsorption of MeCpPt fragments on silicon oxide surfaces was determined by density functional theory (DFT) calculations to be highly exothermic and to favor attachment to Si-O-Si bridge sites.
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Affiliation(s)
- Clinton Lien
- Department of Chemistry , University of California , Riverside , California 02521 , United States
| | - Mahsa Konh
- Department of Chemistry and Biochemistry , University of Delaware , Newark , Delaware 19716 , United States
| | - Bo Chen
- Department of Chemistry , University of California , Riverside , California 02521 , United States
| | - Andrew V Teplyakov
- Department of Chemistry and Biochemistry , University of Delaware , Newark , Delaware 19716 , United States
| | - Francisco Zaera
- Department of Chemistry , University of California , Riverside , California 02521 , United States
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Barry ST, Teplyakov AV, Zaera F. The Chemistry of Inorganic Precursors during the Chemical Deposition of Films on Solid Surfaces. Acc Chem Res 2018; 51:800-809. [PMID: 29489341 DOI: 10.1021/acs.accounts.8b00012] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The deposition of thin solid films is central to many industrial applications, and chemical vapor deposition (CVD) methods are particularly useful for this task. For one, the isotropic nature of the adsorption of chemical species affords even coverages on surfaces with rough topographies, an increasingly common requirement in microelectronics. Furthermore, by splitting the overall film-depositing reactions into two or more complementary and self-limiting steps, as it is done in atomic layer depositions (ALD), film thicknesses can be controlled down to the sub-monolayer level. Thanks to the availability of a vast array of inorganic and metalorganic precursors, CVD and ALD are quite versatile and can be engineered to deposit virtually any type of solid material. On the negative side, the surface chemistry that takes place in these processes is often complex, and can include undesirable side reactions leading to the incorporation of impurities in the growing films. Appropriate precursors and deposition conditions need to be chosen to minimize these problems, and that requires a proper understanding of the underlying surface chemistry. The precursors for CVD and ALD are often designed and chosen based on their known thermal chemistry from inorganic chemistry studies, taking advantage of the vast knowledge developed in that field over the years. Although a good first approximation, however, this approach can lead to wrong choices, because the reactions of these precursors at gas-solid interfaces can be quite different from what is seen in solution. For one, solvents often aid in the displacement of ligands in metalorganic compounds, providing the right dielectric environment, temporarily coordinating to the metal, or facilitating multiple ligand-complex interactions to increase reaction probabilities; these options are not available in the gas-solid reactions associated with CVD and ALD. Moreover, solid surfaces act as unique "ligands", if these reactions are to be viewed from the point of view of the metalorganic complexes used as precursors: they are bulky and rigid, can provide multiple binding sites for a single reaction, and can promote unique bonding modes, especially on metals, which have delocalized electronic structures. The differences between the molecular and surface chemistry of CVD and ALD precursors can result in significant variations in their reactivity, ultimately leading to unpredictable properties in the newly grown films. In this Account, we discuss some of the main similarities and differences in chemistry that CVD/ALD precursors follow on surfaces when contrasted against their known behavior in solution, with emphasis on our own work but also referencing other key contributions. Our approach is unique in that it combines expertise from the inorganic, surface science, and quantum-mechanics fields to better understand the mechanistic details of the chemistry of CVD and ALD processes and to identify new criteria to consider when designing CVD/ALD precursors.
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Affiliation(s)
- Seán T. Barry
- Department of Chemistry, Carleton University, Ottawa, Ontario K1S 5B6, Canada
| | - Andrew V. Teplyakov
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Francisco Zaera
- Department of Chemistry, University of California, Riverside, California 92521, United States
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