Acoustic resonator performance enhancement using selective metal etch

• US 20060132262A1
• Filed: 12/22/2004
• Published: 06/22/2006
• Est. Priority Date: 12/22/2004
• 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: Feng, Hongjun, Fazzio, Ronald S.
• Granted Patent: US 7,791,434 B2
• Time in Patent Office: Days
• US Class Current: 333/187
• CPC Class Codes: H03H 9/02118 of lateral leakage between adjacent resonators
• CPC Class Codes: H03H 9/173 Air-gaps

Abstract

An acoustic resonator that includes a substrate, a first electrode, a layer of piezoelectric material, and a second electrode. The substrate has a first surface and the first electrode is adjacent the first surface of the substrate. The layer of piezoelectric material is adjacent the first electrode. The second electrode is adjacent the layer of piezoelectric material, and the second electrode lies in a first plane and has an edge. The layer of piezoelectric material has a recessed feature adjacent the edge of the second electrode.

Claims

1. An acoustic resonator comprising:

a substrate;

a first electrode adjacent the substrate;

a piezoelectric layer adjacent the first electrode, wherein the piezoelectric layer includes a recessed feature; and

a second electrode adjacent the piezoelectric layer, the second electrode having an edge.

2. The acoustic resonator of claim 1, wherein a depression is formed in the substrate and wherein the first electrode spans the depression.

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, the passivation layer lying in a second plane that is generally parallel to the first plane and having an edge.

5. The acoustic resonator of claim 1, wherein the recessed feature in the piezoelectric layer is outside the edge of the second electrode.

6. The acoustic resonator of claim 1 further including fill material in the recessed feature of the piezoelectric layer.

7. The acoustic resonator of claim 6, wherein the second electrode comprises a material that is the same as the fill material in the recessed feature.

8. The acoustic resonator of claim 6, wherein the fill material is a material selected from the group comprising dielectrics, metals, piezoelectrics, Mo, Pt, Al, Cu, W, Au, Ag, polyimide, BCB, SiO₂, Si₃N₄, AlN, ZnO, LiNbO₃, PZT, LiTaO₃, and Al₂O₃.

9. The acoustic resonator of claim 5, wherein the recessed feature extends around a substantial portion of the perimeter of the second electrode.

10. The acoustic resonator of claim 1 wherein the recessed feature has a depth in the piezoelectric layer that is on the order of hundreds to thousands of angstroms and a width on the order of fractions of a micron to microns.

11. The acoustic resonator of claim 5 wherein the recessed feature is offset from the edge of second electrode by zero to 10s of microns.

12. An acoustic resonator comprising:

a substrate having a first surface;

a first electrode adjacent the first surface of the substrate;

a layer of piezoelectric material adjacent the first electrode;

a second electrode adjacent the layer of piezoelectric material, the second electrode lying in a first plane and having an edge; and

a passivation layer adjacent the second electrode, the passivation layer lying in a second plane that is generally parallel to the first plane and having an edge;

wherein the layer of piezoelectric material has a recessed feature adjacent the edge of the second electrode.

13. The acoustic resonator of claim 12 wherein a depression 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 further including fill material in the recessed feature of the layer of piezoelectric material.

16. The acoustic resonator of claim 15 wherein second electrode comprises a material that is the same as the fill material in the recessed feature.

17. The acoustic resonator of claim 15 wherein the fill material is a material selected from the group comprising dielectrics, metals, piezoelectrics, Mo, Pt, Al, Cu, W, Au, Ag, polyimide, BCB, SiO₂, Si₃N₄, AlN, ZnO, LiNbO₃, PZT, LiTaO₃, and Al₂O₃.

18. The acoustic resonator of claim 12, wherein the recessed feature in the piezoelectric layer is outside the edge of the second electrode.

19. 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;

a passivation layer adjacent the layer of piezoelectric material, wherein the passivation layer includes a recessed feature; and

fill material in the recessed feature of the passivation layer.

20. The acoustic resonator of claim 19 wherein second electrode comprises a material that is the same as the fill material in the recessed feature.

21. The acoustic resonator of claim 19 wherein the fill material is a material selected from the group comprising dielectrics, metals, piezoelectrics, Mo, Pt, Al, Cu, W, Au, Ag, polyimide, BCB, SiO₂, Si₃N₄, AlN, ZnO, LiNbO₃, PZT, LiTaO₃, or Al₂O₃.

22. The acoustic resonator of claim 19 wherein the recessed feature has a depth in the passivation layer that is on the order of ten to thousands of angstroms and a width on the order of fractions of a micron to microns.

23. The acoustic resonator of claim 19, wherein the recessed feature extends around a substantial portion of the perimeter of the passivation layer.