Structurally supported thin film resonator and method of fabrication

• US 6,635,519 B2
• Filed: 01/10/2002
• Issued: 10/21/2003
• Est. Priority Date: 01/10/2002
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Agere Systems Incorporated (Broadcom, Inc.)
• Inventors: Barber, Bradley Paul, Gammel, Peter Ledel, Wong, Yiu-Huen
• Primary Examiner(s): Le, Vu A.
• Assistant Examiner(s): LUU, PHO M
• Application Number:
  US10/043,969
• Publication Number:
  US 20030129785A1
• Time in Patent Office: 649 Days
• Field of Search: 438/151, 438/48, 438/50, 438/53, 257/414
• US Class Current: 438/151
• CPC Class Codes: H03H 3/04 for obtaining desired frequency or temperature coefficient
• CPC Class Codes: H03H 9/564 implemented with thin-film techniques
• CPC Class Codes: H03H 9/583 comprising a plurality of piezoelectric layers acoustically coupled

Abstract

In the thin film resonator, a piezoelectric membrane is disposed over a substrate. A first support structure defines a space over the substrate and supports the edges of the piezoelectric membrane such that the piezoelectric membrane is disposed over this space. A further support structure is disposed within the space to the piezoelectric membrane.

Claims

1. A thin film resonator device, comprising:

a substrate;

a first piezoelectric membrane disposed over the substrate;

a first support structure defining a space over the substrate and supporting edges of the first piezoelectric membrane such that the first piezoelectric membrane is disposed over the space; and

a first anti-flexing support structure disposed within the space to at least attenuate flexing of the first piezoelectric membrane.

2. The device of claim 1, wherein the first anti-flexing support structure substantially maintains the first piezoelectric membrane in a desired shape.

3. The device of claim 1, wherein the first piezoelectric membrane includes aluminum nitride.

4. The device of claim 1, wherein the first anti-flexing support structure includes at least one of a column and a strut spanning the space.

5. The device of claim 1, wherein the first anti-flexing support structure includes at least one of a peg and a strut indirectly connected to only one of the substrate and the first piezoelectric membrane.

6. The device of claim 1, further comprising:

at least one additional piezoelectric membrane structure disposed over the first piezoelectric membrane, each additional piezoelectric membrane structure including,

an additional anti-flexing support structure disposed over the first piezoelectric membrane, and

an additional piezoelectric member supported by the additional anti-flexing support structure.

7. The device of claim 6, wherein the additional anti-flexing support structure is in alignment with the first anti-flexing support structure.

8. The device of claim 1, further comprising:

a cap structure formed over a top most additional piezoelectric membrane structure, the cap structure including,

a cap support structure formed over the first piezoelectric membrane, and

a cap layer supported by the cap support structure.

9. The device of claim 8, wherein the cap support structure is in alignment with the first anti-flexing support structure.

10. The device of claim 1, further comprising:

a first electrode disposed between the first piezoelectric membrane and at least a portion of the first anti-flexing support structure; and

at least a second electrode disposed over the first piezoelectric membrane.

11. A thin film resonator device, comprising:

a substrate;

a piezoelectric membrane disposed over the substrate;

a first support structure defining a space over the substrate and supporting edges of the piezoelectric membrane such that the piezoelectric membrane is disposed over the space;

a first electrode disposed on a bottom surface of the piezoelectric membrane; and

at least a second electrode disposed over the piezoelectric membrane, portions of the space disposed under the first and second electrodes being an active resonator space; and

an anti-flexing support structure disposed within the active resonator space.

12. A method of fabricating a thin film resonator device, comprising:

forming a sacrificial layer over a semiconductor substrate;

forming a first anti-flexing support structure in the sacrificial layer, the first anti-flexing support structure having a different etch selectivity from the sacrificial layer;

forming an electrode over the sacrificial layer;

forming a first piezoelectric membrane layer over the semiconductor substrate;

etching a portion of the sacrificial layer under the first piezoelectric membrane layer to create a cavity under the first piezoelectric membrane layer such that the first anti-flexing support structure is disposed in the cavity to at least attenuate flexing of the first piezoelectric membrane layer.

13. The method of claim 12, wherein the forming a first anti-flexing support structure step forms the first anti-flexing support structure so that after the etching step, the first anti-flexing support structure substantially maintains the first piezoelectric membrane layer over the cavity in a desired shape.

14. The method of claim 12, wherein the first piezoelectric membrane layer includes aluminum nitride.

15. The method of claim 12, wherein the first anti-flexing support structure includes at least one of a column and a strut spanning the space.

16. The device of claim 12, wherein the first anti-flexing support structure includes at least one of a peg and a strut indirectly connected to only one of the substrate and the first piezoelectric membrane layer.

17. The method of claim 12, wherein the forming a first anti-flexing support structure step comprises:

etching the sacrificial layer according to a support structure pattern;

forming a support structure material layer, having a different etch selectivity from the sacrificial layer, over the semiconductor substrate; and

planarizing a resulting structure to expose the sacrificial layer.

18. The method of claim 12, wherein the etching step comprises:

forming at least one contact hole in the first piezoelectric membrane layer and the electrode to expose the sacrificial layer; and

etching the sacrificial layer via the contact hole.

19. The method of claim 18, prior to the forming a sacrificial layer step, further comprising:

forming a lower barrier layer over the semiconductor substrate, the lower barrier layer having a different etch selectivity than the sacrificial layer.

20. The method of claim 19, further comprising:

forming lateral barrier structures in the sacrificial layer, the lateral barrier structures having a different etch selectivity than the sacrificial layer.

21. The method of claim 12, further comprising:

forming a cap support structure over the first piezoelectric membrane layer; and

forming a cap layer supported by the cap support structure.

22. The method of claim 21, wherein the cap support structure is in alignment with the first anti-flexing support structure.

23. The method of claim 12, further comprising:

forming at least one additional piezoelectric membrane structure disposed over the first piezoelectric membrane, each additional piezoelectric membrane structure including,

an additional anti-flexing support structure disposed over the first piezoelectric membrane, and

an additional piezoelectric member supported by the additional anti-flexing support structure.

24. The method of claim 23, wherein the additional anti-flexing support structure is in alignment with the first anti-flexing support structure.

25. The method of claim 12, further comprising:

forming at least one other electrode over the first piezoelectric membrane layer.

26. A method of fabricating a thin film resonator device, comprising:

forming a sacrificial layer over a semiconductor substrate;

forming an anti-flexing support structure in the sacrificial layer, the anti-flexing support structure having a different etch selectivity from the sacrificial layer;

forming a first electrode over the sacrificial layer;

forming a piezoelectric membrane layer over the semiconductor substrate;

forming at least one second electrode over the piezoelectric membrane layer; and

etching a portion of the sacrificial layer under the piezoelectric membrane layer to create a cavity under the piezoelectric membrane layer such that the anti-flexing support structure is disposed in the cavity under both the first and second electrodes.

27. A thin film resonator device, comprising:

a substrate;

a piezoelectric membrane disposed over the substrate;

a first support structure defining a space over the substrate and supporting edges of the piezoelectric membrane such that the piezoelectric membrane is disposed over the space; and

an acoustical support structure disposed within the space to acoustically modify the piezoelectric membrane.

28. A method of fabricating a thin film resonator device, comprising:

forming a sacrificial layer over a semiconductor substrate;

forming an acoustic support structure in the sacrificial layer, the acoustic support structure having a different etch selectivity from the sacrificial layer;

forming an electrode over the sacrificial layer;

forming a piezoelectric membrane layer over the semiconductor substrate;

etching a portion of the sacrificial layer under the piezoelectric membrane layer to create a cavity under the piezoelectric membrane layer such that the acoustical support structure is disposed in the cavity to acoustically modify the piezoelectric membrane layer.