Split-ladder band N77 filter using transversely-excited film bulk acoustic resonators

Patent metadata

Field	Value
Publication number	US-11916539-B2
Application number	US-202117189246-A
Country	US
Kind code	B2
Filing date	Mar 1, 2021
Priority date	Feb 28, 2020
Publication date	Feb 27, 2024
Grant date	Feb 27, 2024

Abstract

Band N77 bandpass filters include a first plurality of transversely-excited film bulk acoustic resonators (XBARs) on a first chip comprising a first rotated YX-cut lithium niobate piezoelectric plate having a thickness less than or equal to 535 nm, and a second plurality of XBARs on a second chip comprising a second rotated YX-cut lithium niobate piezoelectric plate having a thickness greater than or equal to 556 nm. A circuit card is coupled to the first chip and the second chip. The circuit card includes conductors for making electrical connections between the first chip and the second chip.

First claim

It is claimed:

1. A band N77 bandpass filter comprising:
a first plurality of transversely-excited film bulk acoustic resonators (XBARs) on a first chip comprising a first rotated YX-cut lithium niobate piezoelectric plate having a thickness less than or equal to 535 nm;
a second plurality of XBARs on a second chip comprising a second rotated YX-cut lithium niobate piezoelectric plate having a thickness greater than or equal to 556 nm; and
a circuit card coupled to the first chip and the second chip, the circuit card comprising conductors for making electrical connections between the first chip and the second chip.

2. The band N77 filter of claim 1 , wherein:
the first chip, the second chip, and the circuit card collectively form a ladder filter circuit,
the first plurality of XBARs are series resonators in the ladder filter circuit, and
the second plurality of XBARs are shunt resonators in the ladder filter circuit.

3. The band N77 filter of claim 1 , wherein the first and second piezoelectric plates have Euler angles [0°, β, 0°], where 30°≤β≤38°.

4. A band N77 bandpass filter comprising:
a first chip comprising a first substrate, a first rotated YX-cut lithium niobate plate (1 st LN plate), and a first plurality of acoustic resonators, each of the first plurality of acoustic resonators comprising:
an interdigital transducer (IDT) at the 1 st LN plate, interleaved fingers of the IDT at a respective diaphragm, the diaphragm comprising a respective portion of the 1 st LN plate spanning a respective cavity in the first substrate and a dielectric layer on the 1 st LN plate between the interleaved fingers of the IDT,
wherein an LN-equivalent thickness of the diaphragm is less than 535 nm;

a second chip comprising a second substrate, a second rotated YX-cut lithium niobate plate (2 nd LN plate), and a second plurality of acoustic resonators, each of the second plurality of acoustic resonators comprising:
an interdigital transducer (IDT) at the 2 nd LN plate, interleaved fingers of the IDT at a respective diaphragm, the diaphragm comprising a respective portion of the 2 nd LN plate spanning a respective cavity in the first substrate and a dielectric layer at the 2 nd LN plate between the interleaved fingers of the IDT,
wherein an LN-equivalent thickness of the diaphragm is greater than 556 nm; and

a circuit card coupled to the first chip and the second chip, the circuit card comprising conductors for making electrical connections between the first chip and the second chip.

5. The band N77 filter of claim 4 , wherein:
the first chip, the second chip, and the circuit card collectively form a ladder filter circuit,
the first plurality of acoustic resonators are series resonators in the ladder filter circuit, and
the second plurality of acoustic resonators are shunt resonators in the ladder filter circuit.

6. The band N77 filter of claim 4 , wherein the 1 st LN plate and the 2nd LN plate have Euler angles [0°, β, 0°], where 30°≤β≤38°.

7. The band N77 filter of claim 4 , wherein:
for all IDTs of the first plurality of acoustic resonators, a ratio of a pitch of the interleaved fingers to a thickness of the 1 st LN plate is greater than or equal to 6 and less than or equal to 12.5, and
for all IDTs of the second plurality of acoustic resonators, a ratio of a pitch of the interleaved fingers to a thickness of the 2 nd LN plate is greater than or equal to 6 and less than or equal to 12.5.

8. The band N77 filter of claim 4 , wherein for all IDTs of the first plurality of acoustic resonators and the second plurality of acoustic resonators, a ratio of a mark of the interleaved fingers to a pitch of the interleaved fingers is greater than or equal to 0.2 and less than or equal to 0.3.

9. The band N77 filter of claim 4 , wherein the LN-equivalent thickness of the diaphragm of at least one of the first plurality of acoustic resonators is greater than or equal to 465 nm.

10. The band N77 filter of claim 4 , wherein the LN-equivalent thickness of the diaphragm of at least one of the second plurality of acoustic resonators is less than or equal to 600 nm.

11. The band N77 filter of claim 4 , wherein:
the LN-equivalent thickness of each diaphragm of the first plurality of acoustic resonators is given by
teq≈tp 1+ ks ( td )

where teq is the LN equivalent diaphragm thickness, tp1 is a thickness of the 1 st LN plate, td is a thickness of the respective dielectric layer, and ks is a proportionality constant for the first plurality of acoustic resonators.

12. The band N77 filter of claim 11 , wherein the dielectric layer of the first plurality of acoustic resonators is silicon dioxide and ks=0.45.

13. The band N77 filter of claim 4 , wherein:
the LN-equivalent thickness of each diaphragm of the second plurality of acoustic resonators is given by
teq≈tp 2+ kp ( td )

where teq is the LN equivalent diaphragm thickness, tp2 is a thickness of the 2 nd LN plate, td is a thickness of the respective dielectric layer, and kp is a proportionality constant for the second plurality of acoustic resonators.

14. The band N77 filter of claim 13 , wherein the dielectric layer of the second plurality of acoustic resonators is silicon dioxide and kp=0.59.

Assignees

• Murata Manufacturing Co

Inventors

• Jachowski Doug
• Yantchev Ventsislav
• Garcia Bryant
• Turner Patrick

Classifications

• H03H9/568 Primary

  consisting of a ladder configuration · CPC title

• H03H3/02

  for the manufacture of piezoelectric or electrostrictive resonators or networks (H03H3/08 takes precedence) · CPC title

• H03H9/02031

  consisting of ceramic · CPC title

• 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

• H03H9/132

  characterized by a particular shape · CPC title