Film bulk acoustic resonator (FBAR) devices with simplified packaging
First Claim
1. An encapsulated film bulk acoustic resonator (FBAR) device, comprising:
- a substrate;
an FBAR stack over the substrate, the FBAR stack comprising an FBAR and having a top surface remote from the substrate, the FBAR comprising opposed planar electrodes and a piezoelectric element between the electrodes;
means for acoustically isolating the FBAR stack from the substrate;
encapsulant covering the FBAR stack; and
an acoustic Bragg reflector between the top surface of the FBAR stack and the encapsulant, the acoustic Bragg reflector comprising a metal Bragg layer and a plastic Bragg layer juxtaposed with the metal Bragg layer, wherein;
the FBAR device has a band-pass characteristic having a center frequency;
at least one of the Bragg layers has a nominal thickness equal to one quarter of the wavelength in the material of the respective Bragg layer of an acoustic signal equal in frequency to the center frequency; and
the metal Bragg layer is thinner than the nominal thickness.
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Accused Products
Abstract
The encapsulated film bulk acoustic resonator (FBAR) device comprises a substrate, an FBAR stack over the substrate, an element for acoustically isolating the FBAR stack from the substrate, encapsulant covering the FBAR stack, and an acoustic Bragg reflector between the top surface of the FBAR stack and the encapsulant. The FBAR stack comprises an FBAR and has a top surface remote from the substrate. The FBAR comprises opposed planar electrodes and a piezoelectric element between the electrodes. The acoustic Bragg reflector comprises a metal Bragg layer and a plastic Bragg layer juxtaposed with the metal Bragg layer. The large ratio between the acoustic impedances of the metal of the metal Bragg layer and the plastic material of the plastic Bragg layer enables the acoustic Bragg reflector to provide sufficient acoustic isolation between the FBAR and the encapsulant for the frequency response of the FBAR device to exhibit minor, if any, spurious artifacts arising from undesirable acoustic coupling between the FBAR and the encapsulant.
348 Citations
21 Claims
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1. An encapsulated film bulk acoustic resonator (FBAR) device, comprising:
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a substrate; an FBAR stack over the substrate, the FBAR stack comprising an FBAR and having a top surface remote from the substrate, the FBAR comprising opposed planar electrodes and a piezoelectric element between the electrodes; means for acoustically isolating the FBAR stack from the substrate; encapsulant covering the FBAR stack; and an acoustic Bragg reflector between the top surface of the FBAR stack and the encapsulant, the acoustic Bragg reflector comprising a metal Bragg layer and a plastic Bragg layer juxtaposed with the metal Bragg layer, wherein; the FBAR device has a band-pass characteristic having a center frequency;
at least one of the Bragg layers has a nominal thickness equal to one quarter of the wavelength in the material of the respective Bragg layer of an acoustic signal equal in frequency to the center frequency; and
the metal Bragg layer is thinner than the nominal thickness. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. An encapsulated film bulk acoustic resonator (FBAR) device, comprising:
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a substrate; an FBAR stack over the substrate, the FBAR stack comprising an FBAR and having a top surface remote from the substrate, the FBAR comprising opposed planar electrodes and a piezoelectric element between the electrodes; means for acoustically isolating acoustically the FBAR stack from the substrate;
encapsulant covering the FBAR stack; andan acoustic Bragg reflector between the top surface of the FBAR stack and the encapsulant, the acoustic Bragg reflector comprising a first Bragg layer and a second Bragg layer juxtaposed with the first Bragg layer, the first Bragg layer comprising a first material having an acoustic impedance less than five Mrayl and the second Bragg layer comprising a second material having an acoustic impedance greater than 50 Mrayl wherein; the FBAR device has a band-pass characteristic having a center frequency;
at least one of the Bragg layers has a nominal thickness equal to one quarter of the wavelength in the material of the respective Bragg layer of an acoustic signal equal in frequency to the center frequency; and
the metal Bragg layer is thinner than the nominal thickness. - View Dependent Claims (19)
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20. An encapsulated film bulk acoustic resonator (FBAR) device, comprising:
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a substrate; an FBAR stack over the substrate, the FBAR stack comprising an FBAR and having a top surface remote from the substrate, the FBAR comprising opposed planar electrodes and a piezoelectric element between the electrodes; means for acoustically isolating acoustically the FBAR stack from the substrate; encapsulant covering the FBAR stack; and an acoustic Bragg reflector between the top surface of the FBAR stack and the encapsulant, the acoustic Bragg reflector comprising a first Bragg layer and a second Bragg layer juxtaposed with the first Bragg layer, the first Bragg layer comprising a first material having a first acoustic impedance and the second Bragg layer comprising a second material having a second acoustic impedance, the second acoustic impedance and the first acoustic impedance having a ratio greater than ten wherein; the FBAR device has a band-pass characteristic having a center frequency;
at least one of the Bragg layers has a nominal thickness equal to one quarter of the wavelength in the material of the respective Bragg layer of an acoustic signal equal in frequency to the center frequency; and
the metal Bragg layer is thinner than the nominal thickness. - View Dependent Claims (21)
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Specification