• Login
    View Item 
    •   Home
    • Theses & Dissertations
    • 2021 - Mines Theses & Dissertations
    • View Item
    •   Home
    • Theses & Dissertations
    • 2021 - Mines Theses & Dissertations
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Browse

    All of Mines RepositoryCommunitiesPublication DateAuthorsTitlesSubjectsThis CollectionPublication DateAuthorsTitlesSubjects

    My Account

    Login

    Mines Links

    Arthur Lakes LibraryColorado School of Mines

    Statistics

    Display Statistics

    Strategies to enhance etch selectivity during plasma-assisted atomic layer etching of silicon-based dielectrics

    • CSV
    • RefMan
    • EndNote
    • BibTex
    • RefWorks
    Thumbnail
    Name:
    Gasvoda_mines_0052E_12140.pdf
    Size:
    18.71Mb
    Format:
    PDF
    Download
    Thumbnail
    Name:
    supplemental.zip
    Size:
    2.436Mb
    Format:
    Unknown
    Download
    Author
    Gasvoda, Ryan J.
    Advisor
    Agarwal, Sumit
    Date issued
    2021
    Keywords
    atomic layer etching
    infrared spectroscopy
    silicon dielectrics
    etching
    ALE
    plasma etching
    
    Metadata
    Show full item record
    URI
    https://hdl.handle.net/11124/176443
    Abstract
    Stringent processing windows are required for the fabrication of sub-7-nm semiconductor devices, which in turn place severe constraints on conventional plasma-assisted etching. Atomic layer etching (ALE) is a promising etching technique that can provide high etch fidelity, directionality, atomic-scale control, and selectivity to meet and even exceed the process constraints. In this work, we primarily focused on two research objectives: identification of the underlying surface phenomena during ALE of both SiO2 and SiNx using in situ attenuated total reflection Fourier transform infrared spectroscopy combined with in situ four wavelength ellipsometry; using selective gas-phase surface functionalization to enhance the overall etch selectivity of SiO2 to SiNx and vice versa. We first studied plasma-assisted ALE of SiO2 using two sequential half-cycles consisting of fluorocarbon (CFx) deposition and an activation step. Contrary to conventional etching, the interface between the CFx and SiO2 films remains atomically abrupt throughout the ALE process. This is attributed to the complete removal of the CFx film from the surface in every activation half-cycle. We also showed that the etch of SiO2 increases with increasing ALE cycle number due to the accumulation of a CFx film on the reactor walls which releases excess etchant into the chamber during the activation half-cycle. Typically, selectivity is achieved through manipulating the plasma and processing parameters in both half-cycles. To further increase overall etch selectivity, we developed a technique in which the SiO2 or SiNx surface is selectively functionalized through the gas-phase with a hydrocarbon prior to the start of or during ALE. This abundance of hydrocarbon on the functionalized surface promotes the formation of an etch inhibiting graphitic hydrofluorocarbon film after just a few ALE cycles. We demonstrated the facile selective gas-phase surface functionalization of SiO2 over SiNx with cyclic azasilanes and the selective gas-phase surface functionalization of SiNx over SiO2 with aldehydes. The overall etch of a cyclic azasilane functionalized SiO2 film is reduced to ~23% of the original etch of the bare SiO2 surface and etching ceased after ~4 ALE cycles due to the formation of an etch stop layer. Thus, this selective functionalization of SiO2 can be used to increase SiNx to SiO2 etch selectivity. ALE on an aldehyde functionalized SiNx film led to a decrease in the SiNx etch which ultimately translated to an increase in SiO2 to SiNx etch selectivity from ~2.1 to ~4.5. Lastly, we evaluated this functionalization method on a partially etched SiNx which mimics that found in various etch approaches. We show that an aldehyde will react with the damaged and etched SiNx surface. That functionalization also leads to an etch reduction. Therefore, we can use this selective functionalization methodology on a wide variety of etch processes.
    Rights
    Copyright of the original work is retained by the author.
    Collections
    2021 - Mines Theses & Dissertations

    entitlement

     
    DSpace software (copyright © 2002 - 2023)  DuraSpace
    Quick Guide | Contact Us
    Open Repository is a service operated by 
    Atmire NV
     

    Export search results

    The export option will allow you to export the current search results of the entered query to a file. Different formats are available for download. To export the items, click on the button corresponding with the preferred download format.

    By default, clicking on the export buttons will result in a download of the allowed maximum amount of items.

    To select a subset of the search results, click "Selective Export" button and make a selection of the items you want to export. The amount of items that can be exported at once is similarly restricted as the full export.

    After making a selection, click one of the export format buttons. The amount of items that will be exported is indicated in the bubble next to export format.