• Login
    View Item 
    •   Home
    • UA Graduate and Undergraduate Research
    • UA Theses and Dissertations
    • Master's Theses
    • View Item
    •   Home
    • UA Graduate and Undergraduate Research
    • UA Theses and Dissertations
    • Master's Theses
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Browse

    All of UA Campus RepositoryCommunitiesTitleAuthorsIssue DateSubmit DateSubjectsPublisherJournalThis CollectionTitleAuthorsIssue DateSubmit DateSubjectsPublisherJournal

    My Account

    LoginRegister

    About

    AboutUA Faculty PublicationsUA DissertationsUA Master's ThesesUA Honors ThesesUA PressUA YearbooksUA CatalogsUA Libraries

    Statistics

    Most Popular ItemsStatistics by CountryMost Popular Authors

    COMSOL Multiphysics Simulations of Wet Etching of High-Aspect-Ratio Structures with Surface Charge

    • CSV
    • RefMan
    • EndNote
    • BibTex
    • RefWorks
    Thumbnail
    Name:
    azu_etd_16637_sip1_m.pdf
    Size:
    1.865Mb
    Format:
    PDF
    Download
    Author
    O'Connell, Ryan
    Issue Date
    2018
    Keywords
    Chemistry
    COMSOL
    Etching
    Materials
    Modeling
    Advisor
    Raghavan, Srini
    
    Metadata
    Show full item record
    Publisher
    The University of Arizona.
    Rights
    Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction, presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
    Abstract
    In semiconductor manufacturing, the miniaturization of devices has always been a strong driving force in the industry. Making the individual transistors smaller makes it possible to increase the number of transistors on a given size chip, resulting in greater processing power and data storage capabilities. As the critical dimensions of today’s technology nodes approach the atomic scale, it is no longer feasible to obtain the same progression of increased transistor count through simple scaling. In the memory industry, new innovations are being incorporated into the manufacturing process, such as the verticalization of NAND memory to keep up with the demand for increased transistor density. With these innovations come new processing challenges, such as wet etching in extremely high-aspect-ratio (HAR) structures while maintaining top-to-bottom uniformity. The objective of this work was to create simulations in COMSOL Multiphysics that depict the time-dependent etching progress in HAR structures. A dynamic etching model was developed to predict the lateral recession profile of a HAR polysilicon trench bounded on the top and bottom by silicon dioxide (SiO2) etched by tetramethylammonium hydroxide. The model considered the diffusion of active etchant species, surface charging of polysilicon and SiO2, and reaction byproduct accumulation on the top-to-bottom etching profile. The results of the simulations suggest that the diffusion of reactant species into the trench could influence the top-to-bottom etch uniformity if the reaction order is greater than 1. The surface charging on polysilicon and SiO2 does not appear to affect the overall top-to-bottom uniformity but leads to a localized reduction in the etch rate in the corners of the trench where the polysilicon meets the SiO2. The secondary etching simulation was developed to model the wet etching of thin SiO2 films sandwiched between silicon layers, a structure that is often used to create cantilever microstructures. Etching models of SiO2 in hydrofluoric acid (HF) from the literature were utilized to provide boundary velocities in moving-boundary simulations of a dynamic etching process as a function of local concentrations of etchant species. The influence of the surface charge present on silicon in the Si/SiO2/Si stacked structures on the etch rate of SiO2 was modeled for varied thicknesses of SiO2. The etch rate of thin films of SiO2 was compared to the bulk etch rate without electrostatic interference. The simulations did not suggest that the SiO2 thickness in the stacked structure has a strong impact its etch rate because etch rate is dominated by neutral species.
    Type
    text
    Electronic Thesis
    Degree Name
    M.S.
    Degree Level
    masters
    Degree Program
    Graduate College
    Materials Science & Engineering
    Degree Grantor
    University of Arizona
    Collections
    Master's Theses

    entitlement

     
    The University of Arizona Libraries | 1510 E. University Blvd. | Tucson, AZ 85721-0055
    Tel 520-621-6442 | repository@u.library.arizona.edu
    DSpace software copyright © 2002-2017  DuraSpace
    Quick Guide | Contact Us | Send Feedback
    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.