Elastic boundary wave substrate and elastic boundary wave functional element using the substrate
AssigneePanasonic Corporation
InventorsKazuhiko Yamanouchi, Yusuke Satoh
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Abstract
The structure of the patent is a substrate wherein a metal electrode, a dielectric thin film, and a further dielectric thin film are adhered onto a piezoelectric substrate. A substrate wherein elastic wave energy is confined in the piezoelectric substrate can be obtained. In particular, when a SiO2 thin film and an AlN thin film are used as thin films 4 and 5, respectively, a substrate excellent in an electromechanical coupling coefficient (k2) and a temperature characteristic of frequency can be yielded by making the film thicknesses of electrodes 2 and 3 and those of the thin films 4 and 5 into optimal values.
Claims4
An elastic boundary wave functional element comprising:
- a LiNbO3 substrate;
- a film electrode formed above the LiNbO3 substrate;
- a SiO2 film formed above the film electrode;
- and
- a thin film formed above the SiO2 film, the thin film having a transverse wave velocity larger than that of SiO2 film,
- wherein the film electrode has a ratio H2/λ or H3/λ that is 0.05 or more, symbol H2 representing a film thickness of the film electrode, symbol λ representing the wavelength of the central frequency of the boundary wave,
- wherein the SiO2 film has a ratio H4/λ that is 0.4 or more and 1 or less, symbol H4 representing a film thickness of the SiO2 film,
- wherein the thin film has a ratio H5/λ, symbol H5 representing a film thickness of the thin film,
- wherein the functional element is structured and arranged such that when an energy radiation exists in the thickness direction of the substrate, and
- an energy exists in the surface of the thin film,
- the energy radiation in the thickness direction of the substrate is ⅛ or less of the whole energy, and the energy of the surface of the thin film is ⅛ or less of the whole energy, and
- wherein SV wave energy is larger than SH wave energy at a boundary between the LiNbO3 substrate and the SiO2 film.
Dependencies are inferred from the claim text.