Bulk acoustic wave resonator with mass loading layer
Aspects of this disclosure relate to bulk acoustic wave resonators. A bulk acoustic wave resonator includes a patterned mass loading layer that affects a resonant frequency of the bulk acoustic wave resonator. The patterned mass loading layer can have a duty factor in a range from 0.2 to 0.8 in a main acoustically active region of the bulk acoustic wave resonator. Related filters, acoustic wave dies, radio frequency modules, wireless communications devices, and methods are disclosed.
1. A bulk acoustic wave resonator comprising:
a first electrode over an acoustic reflector;
a piezoelectric layer over the first electrode;
a second electrode over the piezoelectric layer; and
a patterned mass loading layer having a duty factor in a range from 0.2 to 0.8 in a main acoustically active region of the bulk acoustic wave resonator, the patterned mass loading layer arranged to affect a resonant frequency of the bulk acoustic wave resonator.
2. The bulk acoustic wave resonator of claim 1 wherein the patterned mass loading layer has a periodic pattern.
3. The bulk acoustic wave resonator of claim 1 wherein the patterned mass loading layer includes a plurality of strips spaced apart from each other.
4. The bulk acoustic wave resonator of claim 1 wherein the patterned mass loading layer includes a different material than any other layer of the bulk acoustic wave resonator in physical contact with the patterned mass loading layer.
5. The bulk acoustic wave resonator of claim 1 wherein the patterned mass loading layer includes a same material as a layer of the bulk acoustic wave resonator in physical contact with the patterned mass loading layer.
6. The bulk acoustic wave resonator of claim 1 wherein the patterned mass loading layer includes a metal.
7. The bulk acoustic wave resonator of claim 1 wherein the patterned mass loading layer includes a dielectric material.
8. The bulk acoustic wave resonator of claim 1 wherein the patterned mass loading layer is positioned below the piezoelectric layer.
9. The bulk acoustic wave resonator of claim 1 wherein the patterned mass loading layer is positioned above the piezoelectric layer.
10. The bulk acoustic wave resonator of claim 1 wherein the patterned mass loading layer is positioned over the second electrode.
11. The bulk acoustic wave resonator of claim 1 wherein the acoustic reflector is a solid acoustic mirror.
12. The bulk acoustic wave resonator of claim 1 wherein the acoustic reflector is an air cavity.
13. An acoustic wave filter comprising:
a bulk acoustic wave resonator including a first electrode over an acoustic reflector, a piezoelectric layer over the first electrode, a second electrode over the piezoelectric layer, and a patterned mass loading layer having a duty factor in a range from 0.2 to 0.8 in a main acoustically active region of the bulk acoustic wave resonator, the patterned mass loading layer arranged to affect a resonant frequency of the bulk acoustic wave resonator; and
a plurality of additional acoustic wave resonators, the acoustic wave filter configured to filter a radio frequency signal.
14. The acoustic wave filter of claim 13 wherein the patterned mass loading layer has a periodic pattern.
15. The acoustic wave filter of claim 13 wherein the bulk acoustic wave resonator is a series resonator.
16. The acoustic wave filter of claim 13 wherein the bulk acoustic wave resonator is a shunt resonator.
17. A wireless communication device comprising:
an acoustic wave filter including a bulk acoustic wave resonator, the bulk acoustic wave resonator including a first electrode over an acoustic reflector, a piezoelectric layer over the first electrode, a second electrode over the piezoelectric layer, and a patterned mass loading layer having a duty factor in a range from 0.2 to 0.8 in a main acoustically active region of the bulk acoustic wave resonator, the patterned mass loading layer arranged to affect a resonant frequency of the bulk acoustic wave resonator;
an antenna operatively coupled to the acoustic wave filter;
a radio frequency amplifier operatively coupled to the acoustic wave filter and configured to amplify a radio frequency signal; and
a transceiver in communication with the radio frequency amplifier.
18. The wireless communication device of claim 17 further comprising a baseband processor in communication with the transceiver.
19. The wireless communication device of claim 17 wherein the acoustic wave filter is included in a radio frequency front end.
20. The wireless communication device of claim 17 wherein the wireless communication device is a user equipment.