Filters with bulk acoustic wave devices
A filter is disclosed. The filter can be a band pass filter or a band rejection filter. The filter can have bulk acoustic wave resonators. The filter can include a shunt bulk acoustic wave resonator and a series bulk acoustic wave resonator. The shunt bulk acoustic wave resonator and the series bulk acoustic wave resonator include different raised frame structures. The different raised frame structures contribute to one of the shunt bulk acoustic wave resonator or the series bulk acoustic wave resonator to have a higher quality factor below a resonant frequency than the other.
1. A band pass filter with bulk acoustic wave resonators, the band pass filter comprising:
a shunt bulk acoustic wave resonator including a first support layer, a first piezoelectric layer over the first support layer, first and second multi-gradient raised frame structures over the first piezoelectric layer, the first and second multi-gradient raised frame structures located on opposing sides of a first acoustically active region, and a first passivation layer over the first and second multi-gradient raised frame structures, the shunt bulk acoustic wave resonator having a first resonant frequency and a first anti-resonant frequency; and
a series bulk acoustic wave resonator including a second support layer, a second piezoelectric layer over the second support layer, and a third and fourth multi-gradient raised frame structures over the second piezoelectric layer, the third and fourth multi-gradient raised frame structures located on opposing sides of a second acoustically active region, and a second passivation layer over the first and second multi-gradient raised frame structures, the third and fourth multi-gradient raised frame structures being different than the first and second multi-gradient raised frame structures, the series bulk acoustic wave resonator having a second resonant frequency and a second anti-resonant frequency, the third and fourth multi-gradient raised frame structures contributing to the series bulk acoustic wave resonator having a higher quality factor below the second resonant frequency than the shunt bulk acoustic wave resonator has below the first resonant frequency, and the band pass filter having a pass band.
2. The band pass filter of claim 1 wherein the first and second multi-gradient raised frame structures contribute to the shunt bulk acoustic wave resonator having a higher quality factor between the first resonant frequency and the first anti-resonant frequency than the series bulk acoustic wave resonator has between the second resonant frequency and the second anti-resonant frequency.
3. The band pass filter of claim 1 wherein the third and fourth multi-gradient raised frame structures provide less mass loading than the first and second multi-gradient raised frame structures.
4. The band pass filter of claim 1 wherein the first and second multi-gradient raised frame structures have at least one more raised frame layer than the third and fourth multi-gradient raised frame structures.
5. The band pass filter of claim 1 wherein the first and second multi-gradient raised frame structures are a dual-layer raised frame structure.
6. The band pass filter of claim 1 further comprising a solid acoustic mirror between the first support layer and the first piezoelectric layer.
7. The band pass filter of claim 1 wherein the shunt bulk acoustic wave resonator includes a cavity in the first support layer.
8. The band pass filter of claim 1 wherein the first and second multi-gradient raised frame structures have a first layer that includes an oxide and a second layer that includes a metal.
9. The band pass filter of claim 1 further comprising a plurality of additional shunt bulk acoustic wave resonators coupled to the shunt bulk acoustic wave resonator, and a plurality of additional series resonators coupled to the series bulk acoustic wave resonator.
10. The band pass filter of claim 1 wherein the first and second multi-gradient raised frame structures include an oxide layer that is in contact with the first piezoelectric layer of the shunt bulk acoustic wave resonator, and the third and fourth multi-gradient raised frame structures do not include an oxide layer that is in contact with the second piezoelectric layer in an active region of the series bulk acoustic wave resonator.
11. The band pass filter of claim 10 wherein the series bulk acoustic wave resonator or the shunt bulk acoustic wave resonator includes a recessed frame structure,
when the series bulk acoustic wave resonator includes the recessed frame structure, the recessed frame structure is positioned between the first acoustically active region of the series bulk acoustic wave resonator and the first multi-gradient raised frame structure, and
when the shunt bulk acoustic wave resonator includes the recessed frame structure, the recessed frame structure is positioned between the second acoustically active region of the shunt bulk acoustic wave resonator and the third multi-gradient raised frame structure.
12. A band rejection filter with bulk acoustic wave resonators, the band rejection filter comprising:
a series bulk acoustic wave resonator including a first support layer, a first piezoelectric layer over the first support layer, first and second multi-gradient raised frame structures over the first piezoelectric layer, the first and second multi-gradient raised frame structures located on opposing sides of a first acoustically active region, and a first passivation layer over the first and second multi-gradient raised frame structures, the series bulk acoustic wave resonator having a first resonant frequency and a first anti-resonant frequency; and
a shunt bulk acoustic wave resonator including a second support layer, a second piezoelectric layer over the second support layer, and third and fourth multi-gradient raised frame structures over the second piezoelectric layer, the third and fourth multi-gradient raised frame structures located on opposing sides of a second acoustically active region, and a second passivation layer over the third and fourth multi-gradient raised frame structures, the third and fourth multi-gradient raised frame structures being different than the first and second multi-gradient raised frame structures, the shunt bulk acoustic wave resonator having a second resonant frequency and a second anti-resonant frequency, the third and fourth multi-gradient raised frame structures contribute to the shunt bulk acoustic wave resonator having a higher quality factor below the second resonant frequency than the series bulk acoustic wave resonator has below the first resonant frequency, and the band rejection filter having a rejection band.
13. The band rejection filter of claim 12 wherein the first and second multi-gradient raised frame structures contribute to the series bulk acoustic wave resonator having a higher quality factor between the first resonant frequency and the first anti-resonant frequency than the shunt bulk acoustic wave resonator has between the second resonant frequency and the second anti-resonant frequency.
14. The band rejection filter of claim 12 wherein the third and fourth multi-gradient raised frame structures provides less mass loading than the first and second multi-gradient raised frame structures.
15. The band rejection filter of claim 12 wherein the first and second multi-gradient raised frame structures have at least one more raised frame layers than the third and fourth multi-gradient raised frame structures.
16. The band rejection filter of claim 12 further comprising a solid acoustic mirror between the first support layer and the first piezoelectric layer.
17. The band rejection filter of claim 12 wherein the series bulk acoustic wave resonator includes a cavity in the first support layer.
18. The band rejection filter of claim 12 wherein the series bulk acoustic wave resonator or the shunt bulk acoustic wave resonator includes a recessed frame structure,
when the series bulk acoustic wave resonator includes the recessed frame structure, the recessed frame structure is positioned between the first acoustically active region of the series bulk acoustic wave resonator and the first multi-gradient raised frame structure, and
when the shunt bulk acoustic wave resonator includes the recessed frame structure, the recessed frame structure is positioned between the second acoustically active region of the shunt bulk acoustic wave resonator and the third multi-gradient raised frame structure.
19. A radio frequency module comprising:
a filter including:
a shunt bulk acoustic wave resonator including a first support layer, a first piezoelectric layer over the first support layer, and first and second multi-gradient raised frame structures over the first piezoelectric layer, the first and second multi-gradient raised frame structures located on opposing sides of an active region, and a first passivation layer over the first and second multi-gradient raised frame structures, the shunt bulk acoustic wave resonator having a first resonant frequency and a first anti-resonant frequency;
a series bulk acoustic wave resonator including a second support layer, a second piezoelectric layer over the second support layer, third and fourth multi-gradient raised frame structures over the second piezoelectric layer, and a second passivation layer over the third and fourth multi-gradient raised frame structures, the third and fourth multi-gradient raised frame structures being different than the first and second multi-gradient raised frame structures, the series bulk acoustic wave resonator having a second resonant frequency and a second anti-resonant frequency, the third and fourth multi-gradient raised frame structures contributing to the series bulk acoustic wave resonator having a higher quality factor below the second resonant frequency than the shunt bulk acoustic wave resonator has below the first resonant frequency, and the filter having a pass band; and
a radio frequency circuit element coupled to the filter, the filter and the radio frequency circuit element being enclosed within a common package.
20. The radio frequency module of claim 19 further comprising a switch configured to selectively couple a terminal of the filter to an antenna port of the radio frequency module, wherein the radio frequency circuit element is a radio frequency amplifier arranged to amplify a radio frequency signal.