Stacked crystal filter structures
AssigneeQorvo US, Inc.
InventorYazid Yusuf
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Abstract
Acoustic resonators, such as bulk acoustic wave (BAW) resonators and, in particular, acoustic resonators including stacked crystal filters (SCFs) are disclosed. SCF structures are disclosed with increased spurious free ranges by providing various arrangements of acoustically soft materials in one or more locations that correspond with high stress regions of one or more modes. For SCFs operating in first order modes, relative amounts of acoustically soft materials within shared electrodes may be increased. One or more additional layers of acoustically soft materials may also be added to SCF structures near shared electrodes. Accordingly, SCFs may be provided with increased frequency spreads between first order modes and second order modes.
Claims26
A stacked crystal filter (SCF) comprising:
- a first piezoelectric layer;
- a second piezoelectric layer;
- a shared electrode between the first piezoelectric layer and the second piezoelectric layer;
- a first electrode on the first piezoelectric layer opposite the shared electrode;
- and
- a second electrode on the second piezoelectric layer opposite the shared electrode;
- wherein the shared electrode comprises a thickness as measured between the first piezoelectric layer and the second piezoelectric layer that is at least two and a half times greater than at least one of a thickness of the first electrode or a thickness of the second electrode.
A stacked crystal filter (SCF) comprising:
- a first piezoelectric layer;
- a second piezoelectric layer;
- a shared electrode between the first piezoelectric layer and the second piezoelectric layer;
- a first electrode on the first piezoelectric layer opposite the shared electrode;
- a second electrode on the second piezoelectric layer opposite the shared electrode;
- and
- a first layer between the shared electrode and the second piezoelectric layer, the first layer comprising a material with a stiffness parameter that is lower than a stiffness parameter of the second piezoelectric layer;
- wherein a frequency of a second order mode is at least 2.5 times higher than a frequency of a first order mode.
Dependencies are inferred from the claim text.