TF-SAW resonator with improved quality factor, RF filter and method of manufacturing a TF-SAW resonator

Patent metadata

Field	Value
Publication number	US-11588464-B2
Application number	US-201917047796-A
Country	US
Kind code	B2
Filing date	Mar 14, 2019
Priority date	Apr 16, 2018
Publication date	Feb 21, 2023
Grant date	Feb 21, 2023

Abstract

A TF-SAW resonator with improved quality factor is provided. The resonator has its piezoelectric material in the form of a thin film and an electrode structure arranged on the piezoelectric layer. Pitch (P) and metallization ratio (n) are chosen to maximize the quality factor (Q).

First claim

The invention claimed is:

1. A thin-film surface acoustic wave (TF-SAW) resonator, comprising:
a carrier substrate;
a piezoelectric layer on or above the carrier substrate, the piezoelectric layer having a thickness T;
a charge reduction layer arranged between the carrier substrate and the piezoelectric layer; and
an electrode structure comprising an interdigital transducer (IDT) structure on the piezoelectric layer, the IDT structure having a pitch P and a metallization ratio η, wherein:
the piezoelectric layer is a thin film comprising a piezoelectric material, and
the pitch P and the metallization ratio η maximize a quality factor Q of the TF-SAW resonator.

2. The TF-SAW resonator of claim 1 , wherein P and η depend on the thickness T of the piezoelectric layer.

3. The TF-SAW resonator of claim 1 , wherein the piezoelectric material comprises LiNbO 3 or LiTaO 3 .

4. The TF-SAW resonator of claim 1 , further comprising an intermediate layer between the carrier substrate and the piezoelectric layer, wherein an acoustic velocity in the intermediate layer is smaller than in the piezoelectric layer.

5. The TF-SAW resonator of claim 1 , further comprising a temperature compensation layer between the carrier substrate and the piezoelectric layer.

6. An RF filter comprising two or more TF-SAW resonators of claim 1 , wherein P and η are chosen for each resonator individually.

7. The TF-SAW resonator of claim 1 , wherein P and η depend on the thickness T of the piezoelectric layer, but are independent from an external electric environment of the resonator.

8. A method of manufacturing a thin-film surface acoustic wave (TF-SAW) resonator, comprising:
depositing a piezoelectric layer comprising a piezoelectric material on or above a carrier substrate utilizing wafer bonding with thin film processing or a thin film layer deposition technique;
arranging a charge reduction layer between the carrier substrate and the piezoelectric layer; and
structuring an electrode structure comprising an interdigital transducer (IDT) structure on the piezoelectric layer with a pitch P and a metallization ratio η chosen to maximize a quality factor Q of the TF-SAW resonator.

9. The TF-SAW resonator of claim 8 , wherein the charge reduction layer comprises polycrystalline silicon.

10. The method of claim 8 , wherein P and η are chosen considering a thickness T of the piezoelectric layer but are independent from an external electric environment of the resonator.

11. The method of claim 8 , further comprising locally trimming a thickness T of the piezoelectric layer.

12. The TF-SAW resonator of claim 8 , wherein P and η depend on a thickness T of the piezoelectric layer.

13. The TF-SAW resonator of claim 8 , wherein the piezoelectric material comprises LiNbO 3 or LiTaO 3 .

14. A radio frequency (RF) filter comprising two or more thin-film surface acoustic wave (TF-SAW) resonators, the TF-SAW resonators comprising:
a carrier substrate;
a piezoelectric layer on or above the carrier substrate, the piezoelectric layer having a thickness T; and
an electrode structure comprising an interdigital transducer (IDT) structure on the piezoelectric layer, the IDT structure having a pitch P and a metallization ratio η, wherein:
P and η are chosen for each TF-SAW resonator individually,
the piezoelectric layer is a thin film comprising a piezoelectric material, and
the pitch P and the metallization ratio η maximize a quality factor Q of the TF-SAW resonator.

15. The RF filter of claim 14 , wherein P and η depend on the thickness T of the piezoelectric layer, but are independent from an external electric environment of the resonators.

16. The RF filter of claim 14 , wherein P and η depend on the thickness T of the piezoelectric layer.

17. The RF filter of claim 14 , wherein the piezoelectric material comprises LiNbO 3 or LiTaO 3 .

18. The RF filter of claim 14 , wherein the TF-SAW resonators further comprise an intermediate layer between the carrier substrate and the piezoelectric layer, wherein an acoustic velocity in the intermediate layer is smaller than in the piezoelectric layer.

19. The RF filter of claim 14 , wherein the TF-SAW resonators further comprise a temperature compensation layer between the carrier substrate and the piezoelectric layer.

Assignees

• RF360 Europe GmbH

Inventors

• Huck Christian
• Knapp Matthias

Classifications

• H03H9/02834

  of temperature influence (cut angles H03H9/02543) · CPC title

• H03H9/02944

  of ohmic loss · CPC title

• H03H9/6489

  Compensation of undesirable effects · CPC title

• H03H9/145

  for networks using surface acoustic waves · CPC title

• H03H9/02559

  of lithium niobate or lithium-tantalate substrates · CPC title