Transversely-excited film bulk acoustic resonator filters with sub-resonators having different mark and pitch

Patent metadata

Field	Value
Publication number	US-12375062-B2
Application number	US-202418620535-A
Country	US
Kind code	B2
Filing date	Mar 28, 2024
Priority date	Feb 28, 2020
Publication date	Jul 29, 2025
Grant date	Jul 29, 2025

Abstract

Radio frequency filters are disclosed. A bandpass filter is discloses that includes one first bulk acoustic resonator on a first chip including a first piezoelectric layer having an LN-equivalent thickness less than or equal to 535 nm; a second bulk acoustic resonator on a second chip including a second piezoelectric layer having a thickness greater than the LN-equivalent thickness of the piezoelectric layer on the first chip; and a circuit card coupled to the first chip and the second chip and that electrically connects the first chip to the second chip.

First claim

What is claimed:

1. A bandpass filter comprising:
at least one first bulk acoustic resonator on a first chip comprising a first piezoelectric layer comprising lithium niobate (LN) and having an LN-equivalent thickness teqa less than or equal to 535 nm;
at least one second bulk acoustic resonator on a second chip comprising a second piezoelectric layer having a thickness greater than the LN-equivalent thickness teqa of the piezoelectric layer on the first chip; and
a circuit card coupled to the first chip and the second chip and that electrically connects the first chip to the second chip,
wherein the LN-equivalent thickness teqa of the first piezoelectric layer is defined by the formula:

teqa
≈

tp

+

ka
⁡
(
tfsd
)

,

wherein tp is a thickness of the first piezoelectric layer, tfsd is a thickness of a dielectric layer at the at least one first bulk acoustic resonator, ka is a constant for the at least one first bulk acoustic resonator, and ka=0.45.

2. The bandpass filter according to claim 1 , wherein the first chip and the second chip are electrically connected in a ladder filter circuit.

3. The bandpass filter according to claim 1 , wherein each of the at least one first bulk acoustic resonator and the at least one second bulk acoustic resonator are laterally-excited.

4. The bandpass filter according to claim 1 , wherein the first and second piezoelectric layers are rotated YX-cut.

5. The bandpass filter according to claim 1 , wherein the first and second piezoelectric layers each have Euler angles [0°, β, 0°], where 30°≤β≤38°.

6. The bandpass filter according to claim 1 , wherein the circuit card comprises at least one interconnection that electrically connects the first and second chip.

7. The bandpass filter according to claim 1 , wherein a pitch of the at least one first bulk acoustic resonator is different than a pitch of the at least one second bulk acoustic resonator.

8. The bandpass filter according to claim 7 , wherein the at least one first bulk acoustic resonator comprises at least two sub-resonators, and the at least one second bulk acoustic resonator comprises at least two sub-resonators.

9. The bandpass filter according to claim 8 , wherein the two sub-resonators of the at least one first bulk acoustic resonator are connected in parallel, and the two sub-resonators of the at least one second bulk acoustic resonator are connected in parallel.

10. The bandpass filter according to claim 1 , wherein the dielectric layer at the at least one first bulk acoustic resonator comprises silicon oxide.

11. The bandpass filter according to claim 1 , wherein the at least one first bulk acoustic resonator is one of a plurality of bulk acoustic resonators connected in series to each other on the first chip.

12. The bandpass filter according to claim 1 , wherein the at least one second bulk acoustic resonator is one of a plurality of bulk acoustic resonators connected in parallel to each other on the second chip.

13. A split-ladder filter comprising:
at least one first bulk acoustic resonator on a first chip comprising a first piezoelectric layer comprising lithium niobate (LN) and having an LN-equivalent thickness teqa less than or equal to 535 nm, wherein the at least one first bulk acoustic resonator comprises at least two first sub-resonators having approximately a same aperture and length, wherein the at least two first sub-resonators are connected in parallel and have a first pitch;
at least one second bulk acoustic resonator on a second chip comprising a second piezoelectric layer having a thickness greater than the LN-equivalent thickness teqa of the first piezoelectric layer on the first chip, wherein the at least one second bulk acoustic resonator comprises at least two second sub-resonators having approximately a same aperture and length, wherein the at least two second sub-resonators are connected in parallel and have a second pitch; and
a circuit card coupled to the first chip and the second chip and that electrically connects the first chip to the second chip,
wherein the LN-equivalent thickness teqa of the first piezoelectric layer is defined by the formula:

teqa
≈

tp

+

ka
⁡
(
tfsd
)

,

wherein tp is a thickness of the first piezoelectric layer, tfsd is a thickness of a dielectric layer at the at least one first bulk acoustic resonator, and ka is a constant for the at least one first bulk acoustic resonator.

14. The split-ladder filter according to claim 13 , wherein the first chip and the second chip are electrically connected in a ladder filter circuit.

15. The split-ladder filter according to claim 13 , wherein the at least one first bulk acoustic resonator and the at least one second bulk acoustic resonator are laterally-excited.

16. The split-ladder filter according to claim 13 , wherein the first and second piezoelectric layers are rotated YX-cut, and ka=0.45.

17. The split-ladder filter according to claim 13 , wherein the first and second piezoelectric layers each have Euler angles [0°, β, 0°], where 30°≤β≤38°.

18. The split-ladder filter according to claim 13 , wherein the at least one first bulk acoustic resonator is one of a plurality of series resonators on the first chip in the split-ladder filter, and wherein the at least one second bulk acoustic resonator is one of a plurality of shunt resonators on the second chip in the split-ladder filter, wherein the first pitch is different than a respective pitch of at least one other series resonator, and wherein the second pitch is different than a respective pitch of at least one other shunt resonator.

19. The split-ladder filter according to claim 18 , wherein at least one of the plurality of series resonators other than the at least one first bulk acoustic resonator is split into at least two sub-resonators, and at least one of the plurality of shunt resonators other than the at least one second bulk acoustic resonator is split into at least two sub-resonators.

20. The split-ladder filter according to claim 13 , wherein the dielectric layer at the at least one first bulk acoustic resonator comprises silicon oxide.

Assignees

• Murata Manufacturing Co

Inventors

• Jachowski Douglas
• Dyer Greg

Classifications

• H03H9/02228

  Guided bulk acoustic wave devices or Lamb wave devices having interdigital transducers situated in parallel planes on either side of a piezoelectric layer · CPC title

• H03H9/176

  consisting of ceramic material (H03H9/177, H03H9/178 take precedence) · CPC title

• H03H9/174

  Membranes · CPC title

• H03H9/132

  characterized by a particular shape · CPC title

• H03H2003/023

  the resonators or networks being of the membrane type · CPC title