Estimating materials parameters in thin-film BAW resonators using measured dispersion curves

Tapani Makkonen (Corresponding Author), Tuomas Pensala (Corresponding Author), Juha Vartiainen, Jouni.V. Knuuttila, Jyrki Kaitila, Martti M. Salomaa

    Research output: Contribution to journalArticleScientificpeer-review

    24 Citations (Scopus)

    Abstract

    The dispersion curves of Lamb-wave modes propagating along a multilayer structure are important for the operation of thin-film bulk acoustic wave (BAW) devices. For instance, the behavior of the side resonances that may contaminate the electrical response of a thin-film BAW resonator depends on the dispersion relation of the layer stack. Because the dispersion behavior depends on the materials parameters (and thicknesses) of the layers in the structure, measurement of the dispersion curves provides a tool for determining the materials parameters of thin films. We have determined the dispersion curves for a multilayer structure through measuring the mechanical displacement profiles over the top electrode of a thin-film BAW resonator at several frequencies using a homodyne Michelson laser interferometer. The layer thicknesses are obtained using scanning electron microscope (SEM) measurements. In the numerical computation of the dispersion curves, the piezoelectricity and full anisotropy of the materials are taken into account. The materials parameters of the piezoelectric layer are determined through fitting the measured and computed dispersion curves.
    Original languageEnglish
    Pages (from-to)42 - 51
    Number of pages10
    JournalIEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
    Volume51
    Issue number1
    DOIs
    Publication statusPublished - 2004
    MoE publication typeA1 Journal article-refereed

    Keywords

    • thin films
    • thin film devices
    • thin-film bulk acoustic wave devices
    • BAW
    • BAW resonators

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