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Yukun Gong Dissertation.pdf (3.69 MB)

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Electrochemical Atomic Layer Etching of Copper and Ruthenium

Gong, Yukun
http://orcid.org/0000-0001-6860-3893
http://rave.ohiolink.edu/etdc/view?acc_num=case1625783128128316

Abstract Details

2021, Doctor of Philosophy, Case Western Reserve University, Chemical Engineering.
Due to an increasing need for atomic-scale tailoring of materials in various applications such as advanced semiconductor processing, atomic layer etching (ALE) is critically needed in order to achieve atomic-level control over etching. Existing vapor-phase, plasma-assisted etching processes do not provide such atomic-scale control in the etching process. Other drawbacks associated with plasma etching techniques include contamination of surfaces and the generation of toxic gaseous byproducts. To address these issues, electrochemical atomic layer etching (e-ALE) utilizing benign liquid-phase chemistry in combination with electrode potential manipulation is developed herein. Electrochemical ALE enables atomically-precise tailoring of surfaces. In the present work, novel e-ALE processes for copper (Cu) and ruthenium (Ru) are demonstrated. A two-step process for etching one metal atomic layer per e-ALE cycle is utilized, where the surface monolayer of the bulk metal film is first oxidized followed by selective etching of the oxidized monolayer without etching the underlying metal. Performing these two steps sequentially enables the removal of metal films in a true ALE mode, i.e., one atomic layer at a time. Surface roughness is not amplified during etching thereby providing the atomic-level precision required in applications. The e-ALE process is advantageous over conventional vapor-phase processes for the following reasons: (i) e-ALE generates stable aquo-complexes which do not contaminate the metal surface; (ii) e-ALE reduces the system complexity and cost and increases throughput in comparison with conventional plasma-assisted etching processes. Layer-by-layer etching of Cu and Ru is experimentally confirmed using electrochemical and microscopic methods. In e-ALE of Cu, through thermodynamic considerations of the Cu surface-limited sulfidization reaction, the optimal sulfidization potential is determined at which surface roughness of Cu is not significantly amplified during etching. Such thermodynamic considerations provide a theory-guided approach for the design of e-ALE sequences.
Rohan Akolkar, Ph.D. (Advisor)
Robert Savinell, Ph.D. (Committee Member)
Christine Duval, Ph.D. (Committee Member)
Mark De Guire, Ph.D. (Committee Member)
120 p.
Chemical Engineering; Nanotechnology
electrochemical atomic layer etching; selective etching; sulfidization of copper; thermodynamic equilibrium

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Citations

  • Gong, Y. (2021). Electrochemical Atomic Layer Etching of Copper and Ruthenium [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1625783128128316

    APA Style (7th edition)

  • Gong, Yukun. Electrochemical Atomic Layer Etching of Copper and Ruthenium. 2021. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1625783128128316.

    MLA Style (8th edition)

  • Gong, Yukun. "Electrochemical Atomic Layer Etching of Copper and Ruthenium." Doctoral dissertation, Case Western Reserve University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=case1625783128128316

    Chicago Manual of Style (17th edition)

case1625783128128316
746
© 2021, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.