Transversely-excited film bulk acoustic resonator for reduced YX-cut piezoelectric coupling
A filter may include a substrate and a rotated YX-cut piezoelectric plate coupled to the substrate. The filter also may include an interdigital transducer (IDT) formed on a portion of the rotated YX-cut piezoelectric plate forming a diaphragm that spans a cavity between the rotated YX-cut piezoelectric plate and the substrate. The IDT includes interleaved fingers that are disposed on the diaphragm. The IDT has an aperture that is less than or equal to 4 times a pitch of the interleaved fingers.
1 . An acoustic resonator device, comprising:
a substrate;
a rotated YX-cut piezoelectric layer coupled to the substrate and including a diaphragm that is over a cavity; and
an interdigital transducer (IDT) including interleaved fingers at the diaphragm of the rotated YX-cut piezoelectric layer,
wherein the IDT has an aperture that is in a range between 10.8 μm and 33 μm, and
wherein the IDT has a pitch that is between 2 and 20 times a width of the interleaved fingers.
2 . The acoustic resonator device of claim 1 , wherein the aperture is approximately 3.6 times the pitch of the interleaved fingers.
3 . The acoustic resonator device of claim 1 ,
wherein the aperture of the IDT is in a range between a first aperture and a second aperture that is less than or equal to 4 times the pitch of the interleaved fingers, and
wherein the first aperture corresponds to a first effective acoustic coupling and the second aperture corresponds to a second effective acoustic coupling that is greater than the first effective acoustic coupling.
4 . The acoustic resonator device of claim 1 ,
wherein the IDT comprises a pair of busbars facing each other with a plurality of interleaved fingers extending from each respective busbar, and
wherein the aperture of the IDT is a distance of an overlap between the respective fingers extending from each of the pair of busbars in a direction perpendicular to a surface of the respective busbars from which the interleaved fingers extends.
5 . The acoustic resonator device of claim 1 , wherein the rotated YX-cut piezoelectric layer comprises 120-yx cut lithium niobate.
6 . The acoustic resonator device of claim 1 , wherein the rotated YX-cut piezoelectric layer comprises 128-yx cut lithium niobate.
7 . The acoustic resonator device of claim 1 , wherein the pitch of the IDT is one-half of an acoustic wavelength at a resonance frequency of the acoustic resonator device.
8 . A filter, comprising:
a substrate having a surface;
a Y-rotated piezoelectric layer attached to the surface of the substrate except for a portion of the Y-rotated piezoelectric layer that comprises a diaphragm that spans a cavity; and
an interdigital transducer (IDT) including interleaved fingers at the diaphragm of the rotated Y-rotated piezoelectric layer,
wherein the IDT has an aperture that is in a range between 10.8 μm and 33 μm, and
wherein the IDT has a pitch that is between 2 and 20 times a width of the interleaved fingers.
9 . The filter of claim 8 , wherein the aperture is approximately 3.6 times the pitch of the interleaved fingers.
10 . The filter of claim 8 ,
wherein the aperture of the filter is in a range between a first aperture and a second aperture that is less than or equal to 4 times the pitch of the interleaved fingers, and
wherein the first aperture corresponds to a first effective acoustic coupling and the second aperture corresponds to a second effective acoustic coupling that is greater than the first effective acoustic coupling.
11 . The filter of claim 8 ,
wherein the IDT comprises a pair of busbars facing each other with a plurality of interleaved fingers extending from each respective busbar, and
wherein the aperture of the IDT is a distance of an overlap between the respective fingers extending from each of the pair of busbars in a direction perpendicular to a surface of the respective busbars from which the interleaved fingers extends.
12 . The filter of claim 8 , wherein the Y-rotated piezoelectric layer comprises 120-yx cut lithium niobate.
13 . The filter of claim 8 , wherein the Y-rotated piezoelectric layer comprises 128-yx cut lithium niobate.
14 . A filter, comprising:
a substrate;
a rotated YX-cut piezoelectric layer attached to at least a portion of a surface of the substrate; and
an interdigital transducer (IDT) comprising interleaved fingers on at least a portion of the rotated YX-cut piezoelectric layer that spans a cavity between the rotated YX-cut piezoelectric layer and the substrate,
wherein the IDT has a distance between a plurality of busbars that is in a range of 10.8 μm to 33 μm.
15 . The filter of claim 14 , wherein the distance between the plurality of busbars is approximately 3.6 times the pitch of the interleaved fingers.
16 . The filter of claim 14 ,
wherein the distance between the plurality of busbars is in a range between a first distance and a second distance that is less than or equal to 4 times the pitch of the interleaved fingers, and
wherein the first distance corresponds to a first effective acoustic coupling and the second distance corresponds to a second effective acoustic coupling that is greater than the first effective acoustic coupling.
17 . The filter of claim 14 , wherein the rotated YX-cut piezoelectric layer comprises 120-yx cut lithium niobate.
18 . The filter of claim 14 , wherein the rotated YX-cut piezoelectric layer comprises 128-yx cut lithium niobate.