Acoustic resonator performance enhancement using alternating frame structure

• US 20060071736A1
• Filed: 06/23/2005
• Published: 04/06/2006
• Est. Priority Date: 10/01/2004
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Avago Technologies Wireless IP Singapore Pte Limited (Broadcom, Inc.)
• Inventors: Ruby, Richard C., Bradley, Paul D., Feng, Hongjun, Fazzio, Ronald S.
• Granted Patent: US 7,388,454 B2
• Time in Patent Office: Days
• US Class Current: 333/187
• CPC Class Codes: H03H 2003/0428 of an electrode
• CPC Class Codes: H03H 3/02 for the manufacture of piezoelectric or electrostrictive resonators or networks H03H3/08 takes precedence
• CPC Class Codes: H03H 9/02086 Means for compensation or elimination of undesirable effects
• CPC Class Codes: H03H 9/02149 of ageing changes of characteristics, e.g. electro-acousto-migration
• CPC Class Codes: H03H 9/13 for networks consisting of piezoelectric or electrostrictive materials H03H9/145 takes precedence
• CPC Class Codes: H03H 9/132 characterized by a particular shape
• CPC Class Codes: H03H 9/173 Air-gaps

Abstract

Disclosed is an acoustic resonator that includes a substrate, a first electrode, a layer of piezoelectric material, a second electrode, and an alternating frame region. The first electrode is adjacent the substrate, and the first electrode has an outer perimeter. The piezoelectric layer is adjacent the first electrode. The second electrode is adjacent the piezoelectric layer and the second electrode has an outer perimeter. The alternating frame region is on one of the first and second electrodes.

Claims

1. An acoustic resonator comprising:

a substrate;

a first electrode adjacent the substrate, wherein the first electrode has an outer perimeter;

a piezoelectric layer adjacent the first electrode;

a second electrode adjacent the piezoelectric layer, wherein the second electrode has an outer perimeter; and

an alternating frame region on one of the first and second electrodes.

2. The acoustic resonator of claim 1, wherein a depression is formed in the substrate and wherein the depression has a depression perimeter.

3. The acoustic resonator of claim 1, wherein an acoustic mirror is formed in the substrate and wherein the first electrode spans the acoustic mirror.

4. The acoustic resonator of claim 1 further including a passivation layer adjacent the second electrode.

5. The acoustic resonator of claim 1, wherein the alternating frame region includes at least one raised frame adjacent at least one relatively recessed region.

6. The acoustic resonator of claim 5, wherein the alternating frame region is a distributed Bragg reflector.

7. The acoustic resonator of claim 5, wherein at least one raised frame of the alternating frame region is a material selected from the group comprising dielectrics, metals, metal alloys, piezoelectrics, Mo, Pt, Al, Cu, W, Au, Ag, polyimide, BCB, SiO₂, Si₃N₄, AlN, ZnO, LiNbO₃, PZT, LiTaO₃, and Al₂O₃.

8. The acoustic resonator of claim 2, wherein the alternating frame region is outside the depression perimeter adjacent the outer perimeter of the second electrode.

9. The acoustic resonator of claim 2, wherein the alternating frame region overlaps the depression perimeter.

10. The acoustic resonator of claim 2, wherein the alternating frame region is inside the depression perimeter.

11. The acoustic resonator of claim 1, wherein the alternating frame region extends around a substantial portion of the outer perimeter of one of the first and second electrodes.

12. An acoustic resonator comprising:

a first electrode;

a layer of piezoelectric material adjacent the first electrode;

a second electrode adjacent the layer of piezoelectric material, the second electrode having an outer perimeter; and

an alternating frame region configured on the second electrode adjacent the outer perimeter.

13. The acoustic resonator of claim 12, wherein a depression having a depression perimeter is formed in the first surface of the substrate and wherein the first electrode spans the depression.

14. The acoustic resonator of claim 12, wherein an acoustic mirror is formed in the first surface of the substrate and wherein the first electrode spans the acoustic mirror.

15. The acoustic resonator of claim 12, wherein the alternating frame region further comprises a first region having a first acoustic impedance and a second region having a second acoustic impedance, the first and second acoustic impedances being different such that certain wavelengths of signals within the acoustic resonator reflect and interfere to improve Q.

16. The acoustic resonator of claim 15, wherein alternating frame region comprises at least a first raised frame and a second raised frame on the second electrode, the first and second raised frames being spaced apart from each other.

17. The acoustic resonator of claim 16, wherein the alternating frame region is a distributed Bragg reflector.

18. The acoustic resonator of claim 16, wherein first and second spaced apart raised frames are the same width.

19. The acoustic resonator of claim 16, wherein the first frame is wider than the second frame.

20. The acoustic resonator of claim 16, wherein the first frame is thicker than the second electrode.

21. The acoustic resonator of claim 16, further including a recessed region inside the first and second raised frames.

22. An acoustic resonator comprising:

a substrate;

a first electrode adjacent the substrate;

a layer of piezoelectric material adjacent the first electrode;

a second electrode adjacent the layer of piezoelectric material, wherein the first electrode, the layer of piezoelectric material and the second electrode together form an acoustic membrane having an outer edge and a center; and

means adjacent the outer edge of the acoustic membrane for trapping lateral modes within the acoustic membrane.

23. The acoustic resonator of claim 22, including a alternating frame region adjacent the outer edge of the acoustic membrane.

24. The acoustic resonator of claim 23, wherein the alternating frame region further comprises a first region having a first acoustic impedance and a second having a second acoustic impedance, the first and second acoustic impedances being different such that certain wavelengths of signals within the acoustic resonator reflect and interfere to improve Q.

25. The acoustic resonator of claim 24, wherein the alternating frame region comprises a plurality of raised frames on the second electrode, each of the plurality of raised frames being spaced apart.

26. The acoustic resonator of claim 22, wherein at least one of the raised frames on the second electrode stiffens the edge of the acoustic membrane thereby trapping modes within the resonator.

27. A method for fabricating an acoustic resonator comprising:

providing a substrate;

fabricating a first electrode adjacent the substrate;

fabricating a piezoelectric layer adjacent the first electrode;

depositing electrode material to form a second electrode up to a first thickness adjacent the piezoelectric layer;

depositing a first photo mask over the second electrode;

depositing additional material to form at least one raised frame on the second electrode;

removing the photo mask thereby revealing an alternating frame region on the second electrode.

28. The method of claim 27 further including depositing additional material to form a plurality of raised frames on the second electrode.

29. The method of claim 27 further including forming a depression in the substrate.