Cavity-less film bulk acoustic resonator (FBAR) devices
First Claim
1. A film bulk acoustic resonator (FBAR) device, comprising:
- a substrate;
an acoustic Bragg reflector over the substrate, the acoustic Bragg reflector comprising a metal Bragg layer and a plastic Bragg layer juxtaposed with the metal Bragg layer;
a piezoelectric element over the acoustic Bragg reflector; and
a remote-side electrode over the piezoelectric element 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 film bulk acoustic resonator (FBAR) device comprises a substrate, an acoustic Bragg reflector over the substrate, a piezoelectric element over the acoustic Bragg reflector, and a remote-side electrode over the piezoelectric element. The acoustic Bragg reflector comprises a metal Bragg layer juxtaposed with a plastic Bragg layer. The large ratio between the acoustic impedances of the plastic material of the plastic Bragg layer and the metal of the metal Bragg layer provides sufficient acoustic isolation between the FBAR and the substrate 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 substrate.
368 Citations
29 Claims
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1. A film bulk acoustic resonator (FBAR) device, comprising:
- a substrate;
an acoustic Bragg reflector over the substrate, the acoustic Bragg reflector comprising a metal Bragg layer and a plastic Bragg layer juxtaposed with the metal Bragg layer;
a piezoelectric element over the acoustic Bragg reflector; and
a remote-side electrode over the piezoelectric element 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, 18, 19, 20, 21)
- a substrate;
-
22. A film bulk acoustic resonator (FBAR) device, comprising:
- a substrate;
an acoustic Bragg reflector over the substrate, 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, the second Bragg layer comprising a second material having an acoustic impedance greater than 50 Mrayl;
a piezoelectric element over the acoustic Bragg reflector; and
a remote-side electrode over the piezoelectric element, 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 (23, 24, 25)
- a substrate;
-
26. A film bulk acoustic resonator (FBAR) device, comprising:
- a substrate;
an acoustic Bragg reflector over the substrate, 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, 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;
a piezoelectric element over the second Bragg layer; and
a remote-side electrode over the piezoelectric element, 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 (27, 28, 29)
- a substrate;
Specification