Tapered electrode in an acoustic resonator

• US 20040263287A1
• Filed: 06/30/2003
• Published: 12/30/2004
• Est. Priority Date: 06/30/2003
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Wang, Li-Peng, Ginsburg, Eyal, Rubin, Doron, Bar-Sadeh, Eyal, Talalyevsky, Alexander
• Granted Patent: US 6,924,717 B2
• Time in Patent Office: Days
• US Class Current: 333/187
• CPC Class Codes: H03H 9/02133 of stress
• CPC Class Codes: H03H 9/132 characterized by a particular shape

Abstract

An apparatus and method to provide a tapered electrode in an acoustic resonator. A piezoelectric (PZ) layer, such as Aluminum Nitride (AIN), is formed over a bottom electrode having a tapered end. A top electrode is positioned on the PZ layer. The tapered end of the bottom electrode creates a mild topography to the under layer of the PZ material to prevent cracking in the PZ layer. The tapered end also decreases acoustic losses in the acoustic resonator because the PZ grains are highly oriented. In one embodiment, the acoustic resonator is a film bulk acoustic resonator (FBAR).

Claims

1. An apparatus, comprising:

an electrode including a tapered end; and

a piezoelectric material of an acoustic resonator disposed over the electrode.

2. The apparatus of claim 1 wherein the piezoelectric material comprises Aluminum Nitride (AIN), Zinc Oxide (ZnO), or lead titanate zirconate (PZT).

3. The apparatus of claim 1 wherein the tapered end has an angle between approximately five and thirty degrees.

4. The apparatus of claim 1 wherein the electrode comprises at least one of aluminum, gold, chromium, platinum, molybdenum.

5. The apparatus of claim 1, further comprising a top electrode adjacent to a second side of the piezoelectric material, wherein the electrode is a bottom electrode adjacent to a first side of the piezoelectric material.

6. The apparatus of claim 5, further comprising a substrate layer under the bottom electrode.

7. The apparatus of claim 6, further comprising a dielectric layer between the substrate layer and the bottom electrode.

8. The apparatus of claim 1 wherein the tapered end is formed through a wet etching process.

9. The apparatus of claim 1 wherein the acoustic resonator is a film bulk acoustic resonator (FBAR).

10. A film bulk acoustic resonator (FBAR), comprising:

a bottom electrode including a tapered end;

a piezoelectric layer layered on the bottom electrode; and

a top electrode positioned on top of the piezoelectric layer wherein at least a portion of the piezoelectric layer is disposed between the bottom electrode and the top electrode.

11. The apparatus of claim 10, further comprising a substrate positioned under the bottom electrode.

12. The apparatus of claim 10 wherein the tapered end has an angle between approximately five and thirty degrees between a flat bottom side of the tapered end and a sloped upper side of the tapered end.

13. The apparatus of claim 10 wherein a first surface area of the bottom electrode is less than a surface area of the piezoelectric layer.

14. The apparatus of claim 13 wherein at least a portion of a parameter of the bottom electrode includes the tapered end.

15. A method, comprising:

forming a metal layer on top of a dielectric layer; and

shaping the metal layer to form a tapered electrode of an acoustic resonator.

16. The method of claim 15, further comprising placing a photoresist layer on top of the metal layer.

17. The method of claim 16 wherein shaping the metal layer comprises wet etching the metal layer to form the tapered electrode.

18. The method of claim 15 wherein the tapered electrode has an angle between approximately five and thirty degrees.

19. An apparatus, comprising:

a piezoelectric layer of an acoustic resonator; and

means for preventing cracks in the piezoelectric layer.

20. The apparatus of claim 19 wherein the means for preventing cracks comprises a bottom electrode including a tapered end positioned under the piezoelectric layer.

21. The apparatus of claim 20 wherein the tapered end has an angle between approximately five and thirty degrees.

22. The apparatus of claim 20 wherein the acoustic resonator is a film bulk acoustic resonator (FBAR).

23. The apparatus of claim 22 wherein the piezoelectric layer comprises Aluminum Nitride (AIN), Zinc Oxide (ZnO), or lead titanate zirconate (PZT).

24. A system, comprising:

a film bulk acoustic resonator (FBAR) filter, comprising;

a bottom electrode including a tapered end; and

a piezoelectric material layered on the bottom electrode; and

a transmitter electrically coupled to the FBAR filter.

25. The system of claim 24 wherein the piezoelectric material comprises Aluminum Nitride (AIN), Zinc Oxide (ZnO), or lead titanate zirconate (PZT).

26. The system of claim 24 wherein the system is a wireless device.