Surface acoustic wave devices using piezoelectric film on silicon carbide

Patent metadata

Field	Value
Publication number	US-12015392-B2
Application number	US-202117211094-A
Country	US
Kind code	B2
Filing date	Mar 24, 2021
Priority date	Mar 26, 2020
Publication date	Jun 18, 2024
Grant date	Jun 18, 2024

Abstract

An acoustic resonator includes a piezoelectric thin film (PTF) disposed on a carrier substrate. The PTF confines a fundamental shear-horizontal (SH0) surface-acoustic wave (SAW) within the PTF. The acoustic resonator includes an input bus line coupled to an input source and a ground bus line coupled to a ground potential. The acoustic resonator includes a first grating reflector disposed at a first end of the PTF and coupled between the input bus line and the ground bus line. The acoustic resonator includes a second grating reflector disposed at a second end of the PTF and coupled between the input bus line and the ground bus line. The acoustic resonator includes interdigital transducers (IDTs) disposed between the first grating reflector and the second grating reflector. Each IDT includes an input electrode coupled to the input bus line, and a ground electrode coupled to the ground bus line.

First claim

What is claimed is:

1. An acoustic resonator comprising:
a piezoelectric thin film disposed on a carrier substrate, wherein the piezoelectric thin film is adapted to confine a fundamental shear horizontal (SH0) surface acoustic wave (SAW) within the piezoelectric thin film;
an input bus line coupled to an input source;
a ground bus line coupled to a ground potential;
a first grating reflector disposed at a first end of the piezoelectric thin film and coupled between the input bus line and the ground bus line;
a second grating reflector disposed at a second end of the piezoelectric thin film, the second end being opposite the first end, the second grating reflector being coupled between the input bus line and the ground bus line; and
a plurality of interdigital transducers (IDTs) disposed between the first grating reflector and the second grating reflector, wherein each IDT comprises an input electrode and a ground electrode, the input electrode being coupled to the input bus line and the ground electrode being coupled to the ground bus line.

2. The acoustic resonator of claim 1 , wherein the piezoelectric thin film is one of an X-cut lithium niobate (LiNbO 3 ) thin film or lithium tantalate (LiTaO 3 ) thin film.

3. The acoustic resonator of claim 1 , wherein the carrier substrate is one of diamond, sapphire, alpha-quartz, or silicon carbide (SiC), wherein the SiC is one of four-hexagonal (4H)-SiC or six-hexagonal (6H)-SiC.

4. The acoustic resonator of claim 1 , wherein the piezoelectric thin film is solid-mounted piezoelectric thin film.

5. The acoustic resonator of claim 1 , wherein the first grating reflector and the second grating reflector each comprise a plurality of parallel metal strips, wherein a periodicity of the metal strips is half of a periodicity of the IDTs.

6. The acoustic resonator of claim 1 , wherein a distal end of the input electrode is separated from the ground bus line by a first distance, and a distal end of the ground electrode is separated from the input bus line by one of the first distance or a second distance.

7. The acoustic resonator of claim 1 , wherein a distal end of the input electrode is separated from a distal end of the ground electrode by a second distance, the second distance being an aperture width of the acoustic resonator.

8. The acoustic resonator of claim 7 , wherein a ratio of the aperture width to a width of the input electrode and the ground electrode is between 20 and 100.

9. The acoustic resonator of claim 1 , wherein the first grating reflector is separated from a first IDT of the plurality of IDTs by a first distance, and the second grating reflector is separated from a second IDT of the plurality of IDTs by the first distance.

10. The acoustic resonator of claim 1 , wherein a ratio of a thickness of the piezoelectric thin film to a wavelength of the SH0-SAW is less than 0.35.

11. An acoustic filter comprising:
a first shunt resonator coupled to a ground potential
a second shunt resonator coupled to the ground potential; and
a series resonator coupled between the first shunt resonator and the second shunt resonator and to an input source, wherein the first shunt resonator, the second shunt resonator, and the series resonator each comprises:
a piezoelectric thin film disposed on a carrier substrate, wherein the piezoelectric thin film is adapted to confine a fundamental shear horizontal (SH0) surface acoustic wave (SAW) within the piezoelectric thin film;
an input bus line coupled to the input source;
a ground bus line coupled to the ground potential;
a first grating reflector disposed at a first end of the piezoelectric thin film and coupled between the input bus line and the ground bus line;
a second grating reflector disposed at a second end of the piezoelectric thin film, the second end being opposite the first end, the second grating reflector being coupled between the input bus line and the ground bus line; and
a plurality of interdigital transducers (IDTs) disposed between the first grating reflector and the second grating reflector, wherein each IDT comprises an input electrode and a ground electrode.

12. The acoustic filter of claim 11 , wherein the input electrode is coupled to an input pad and the ground electrode is coupled to a ground pad, and wherein the input pad is coupled to the input source and the ground pad is coupled to the ground potential.

13. The acoustic filter of claim 11 , wherein the piezoelectric thin film is one of an X-cut lithium niobate (LiNbO 3 ) thin film or lithium tantalate (LiTaO 3 ) thin film.

14. The acoustic filter of claim 11 , wherein the carrier substrate is one of diamond, sapphire, alpha-quartz, or silicon carbide (SiC), wherein the SiC is four-hexagonal (4H)-SiC or six-hexagonal (6H)-SiC.

15. The acoustic filter of claim 11 , wherein the series resonator operates at a first frequency, the first shunt resonator and the second shunt resonator operate at a second frequency that is offset from the first frequency, and wherein a bandwidth of the acoustic filter is approximately the offset.

16. The acoustic filter of claim 15 , wherein the offset is approximately a spectral separation between a resonant frequency of the first shunt resonator and an anti-resonant frequency of the series resonator.

17. The acoustic filter of claim 15 , wherein the offset is determined by varying a periodicity of the plurality of IDTs.

18. An apparatus comprising:
a piezoelectric thin film disposed on a carrier substrate, wherein the piezoelectric thin film is adapted to propagate a fundamental shear horizontal (SH0) surface acoustic wave (SAW);
a plurality of pairs of interdigital transducer (IDT) electrodes disposed on top of the piezoelectric thin film, wherein each pair of the plurality of pairs of IDT electrodes comprises a signal electrode and a ground electrode, wherein signal electrodes between adjacent pairs of the plurality of pairs of IDTs are separated by a first period;
a first grating reflector disposed at a first end of the piezoelectric thin film and separated from a first end of the plurality of pairs of IDT electrodes, wherein the first grating reflector comprises a first set of electrically-shorted metal strips separated according to a second period; and
a second grating reflector disposed at a second end of the piezoelectric thin film and separated from a second end of the plurality of pairs of IDT electrodes.

19. The apparatus of claim 18 , wherein the second period is approximately half of the first period.

20. The apparatus of claim 18 , wherein the signal electrode extends distally away from an input bus line and the ground electrode extends distally away from a ground bus line, and wherein an aperture of the apparatus comprises a distance between a distal end of the signal electrode and a distal end of the ground electrode.

21. The apparatus of claim 18 , wherein the second grating reflector comprises a second set of electrically-shorted metal strips separated according to a third period.

22. The apparatus of claim 21 , wherein a separation between the first grating reflector and the first end of the plurality of pairs of IDT electrodes comprises a first distance, and wherein a separation between the second end of the plurality of pairs of IDTs and the second grating reflector comprises a second distance.

23. The apparatus of claim 18 , wherein the piezoelectric thin film is one of an X-cut lithium niobate (LiNbO 3 ) thin film or lithium tantalate

Assignees

• Board Of Trustees Of The Univ Of Illinois
• Univ Illinois

Inventors

• Zhang Shibin
• Lu Ruochen
• Link Steffen
• Yang Yansong
• Gong Songbin

Classifications

• H03H9/02992

  Details of bus bars, contact pads or other electrical connections for finger electrodes · CPC title

• H03H9/25

  Constructional features of resonators using surface acoustic waves {(devices for manipulating acoustic surface waves in general G10K11/36)} · CPC title

• H03H9/145

  for networks using surface acoustic waves · CPC title

• H03H9/6483

  Ladder SAW filters · CPC title

• H03H9/02637

  Details concerning reflective or coupling arrays · CPC title