Stacked bulk acoustic resonator band-pass filter with controllable pass bandwidth
First Claim
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1. A method of fabricating an acoustically-coupled device, the method comprising:
- fabricating a first film bulk acoustic resonator (FBAR);
fabricating an acoustic decoupler on the first FBAR;
fabricating a second FBAR on the acoustic decoupler, including subjecting the acoustic decoupler to a fabrication temperature; and
prior to fabricating the second FBAR, baking the first FBAR and the acoustic decoupler at a baking temperature not lower than the fabrication temperature.
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Abstract
The band-pass filter has a stacked pair of film bulk acoustic resonators (FBARs) and an acoustic decoupler between the FBARs. Each of the FBARs has opposed planar electrodes and a layer of piezoelectric material between the electrodes. The acoustic decoupler controls the coupling of acoustic energy between the FBARs. Specifically, the acoustic decoupler couples less acoustic energy between the FBARs than would be coupled by direct contact between the FBARs. The reduced acoustic coupling gives the band-pass filter desirable in-band and out-of-band properties.
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Citations
20 Claims
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1. A method of fabricating an acoustically-coupled device, the method comprising:
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fabricating a first film bulk acoustic resonator (FBAR); fabricating an acoustic decoupler on the first FBAR; fabricating a second FBAR on the acoustic decoupler, including subjecting the acoustic decoupler to a fabrication temperature; and prior to fabricating the second FBAR, baking the first FBAR and the acoustic decoupler at a baking temperature not lower than the fabrication temperature. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of fabricating an acoustically-coupled device, the method comprising:
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forming a first film bulk acoustic resonator (FBAR) over a substrate; forming an acoustic decoupler over the first FBAR; baking the deposited first FBAR and the acoustic decoupler at a first temperature; and forming a second FBAR over the acoustic decoupler after baking the first FBAR and the acoustic decoupler, reaching a second temperature while forming the second FBAR, wherein the second temperature does not exceed the first temperature. - View Dependent Claims (14, 15, 16, 17)
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18. A method of fabricating an acoustic filter, the method comprising:
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filling a cavity in a substrate with a fill material; forming a first film bulk acoustic resonator (FBAR) over the fill material and the substrate; forming an acoustic decoupler over the first FBAR; and forming a second FBAR over the acoustic decoupler, wherein, prior to forming the second FBAR, baking the first FBAR and the acoustic decoupler at a baking temperature that is not less than a temperature used for forming the second FBAR. - View Dependent Claims (19, 20)
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Specification