Acoustic resonator

• US 20050146401A1
• Filed: 12/27/2004
• Published: 07/07/2005
• Est. Priority Date: 12/24/2003
• Status: Active Grant

• Current Assignee: Interuniversatair Micro-Elektronica Centrum (Imecvzw), Belgium Corporation
• Original Assignee: Interuniversitair Micro-Electronica Centrum VZW (IMEC International)
• Inventors: Tilmans, Hendrikus A.C., Pan, Wanling
• Granted Patent: US 7,372,346 B2
• Time in Patent Office: Days
• US Class Current: 333/187
• CPC Class Codes: H03H 2009/02196 operating on the FBAR element, e.g. by direct application of a tuning DC voltage
• CPC Class Codes: H03H 9/02102 of temperature influence cutting angles H03H9/02015
• CPC Class Codes: H03H 9/172 Means for mounting on a substrate, i.e. means constituting the material interface confining the waves to a volume

Abstract

A tuneable film bulk acoustic resonator (FBAR) device. The FBAR device includes a bottom electrode, a top electrode and a piezoelectric layer in between the bottom electrode and the top electrode. The piezoelectric layer has a first overlap with the bottom electrode, where the first overlap is defined by a projection of the piezoelectric layer onto the bottom electrode in a direction substantially perpendicular to a plane of the bottom electrode. The FBAR device also includes a first dielectric layer in between the piezoelectric layer and the bottom electrode and a mechanism for reversibly varying an internal impedance of the device, so as to tune a resonant frequency of the FBAR device.

Claims

1. An FBAR device comprising:

a bottom electrode;

a top electrode;

a piezoelectric layer in between the bottom electrode and the top electrode, the piezoelectric layer having a first overlap with the bottom electrode, the first overlap being defined by a projection of the piezoelectric layer onto the bottom electrode in a direction substantially perpendicular to a plane of the bottom electrode;

a first dielectric layer in between the piezoelectric layer and the bottom electrode, the first dielectric layer having a first thickness; and

a mechanism for reversibly varying an internal impedance of the device, so as to tune a resonant frequency of the FBAR device.

2. The FBAR device of claim 1, wherein the piezoelectric layer is suspended on a single side and is part of a cantilever structure.

3. The FBAR device of claim 1, wherein the mechanism for reversibly varying the internal impedance of the FBAR device comprises one of a mechanism for altering relative positions of components of the FBAR device and a mechanism for moving a constituting element in the form of a solid piece or block of material having a dielectric constant greater than 1 into or out of a part of the FBAR device in which there is an electric field during operation.

4. The FBAR device of claim 1, wherein the mechanism for reversibly varying the internal impedance of the device is a mechanism for varying the first thickness of the first dielectric layer.

5. The FBAR device of claim 1, further comprising a second dielectric layer having a second thickness, the second dielectric layer being in between the piezoelectric layer and the top electrode, the piezoelectric layer having a second overlap with the top electrode, the second overlap being defined by a projection of the piezoelectric layer onto the top electrode in a direction substantially perpendicular to a plane of the top electrode.

6. The FBAR device of claim 5, wherein the mechanism for varying the internal impedance of the FBAR device comprises a mechanism for varying the second thickness of the second dielectric layer.

7. The FBAR device of claim 1, wherein the first dielectric layer comprises a gas.

8. The FBAR device of claim 1, wherein the first dielectric layer comprises a space under vacuum.

9. The FBAR device of claim 1, wherein the bottom electrode comprises a first material and the top electrode comprises a second material, the first material and the second material being different from each other.

10. The FBAR device of claim 9, wherein the first material is a first metal and the second material is a second metal.

11. The FBAR device of claim 1, wherein the FBAR device has a Quality factor greater than three hundred.

12. The FBAR device of claim 1, wherein the FBAR device has a tuning range between 1% and 3%.

13. An FBAR device comprising:

a bottom electrode;

a top electrode;

a piezoelectric layer in between the bottom electrode and the top electrode, the piezoelectric layer having a first overlap with the bottom electrode, the first overlap being defined by a projection of the piezoelectric layer onto the bottom electrode in a direction substantially perpendicular to a plane of the bottom electrode, and the piezoelectric layer having a second overlap with the top electrode, the second overlap being defined by a projection of the piezoelectric layer onto the top electrode in a direction substantially perpendicular to a plane of the top electrode;

a first dielectric layer in between the piezoelectric layer and the bottom electrode, the first dielectric layer having a first thickness;

a second dielectric in between the piezoelectric layer and the top electrode, the second dielectric layer having a second thickness; and

a mechanism for reversibly varying an internal impedance of the FBAR device, so as to tune the resonant frequency of the device.

14. The FBAR device of claim 13, wherein the piezoelectric layer is suspended on a single side and is part of a cantilever structure.

15. The FBAR device of claim 13, wherein the mechanism for varying the internal impedance of the FBAR device is one of a mechanism for altering relative positions of components of the FBAR device and a mechanism for moving a constituting element in the form of a solid piece or block of material having a dielectric constant greater than 1 into or out of a part of the FBAR device in which there is an electric field in operation.

16. The FBAR device of claim 13, wherein the mechanism for varying the internal impedance of the FBAR device is a mechanism for varying at least one of the first thickness of the first dielectric layer and the second thickness of the second dielectric layer.

17. A method for tuning a resonant frequency of an FBAR device comprising a bottom electrode, a top electrode, a piezoelectric layer in between the bottom electrode and the top electrode, the piezoelectric layer having a first overlap with the bottom electrode, the first overlap being defined by a projection of the piezoelectric layer onto the bottom electrode in a direction substantially perpendicular to a plane of the bottom electrode, and a first dielectric layer in between the piezoelectric layer and the bottom electrode, the method comprising:

varying an internal impedance of the FBAR device to tune the resonant frequency, wherein the tuning is reversible.

18. The method of claim 17, wherein varying the internal impedance of the FBAR device comprises one of altering relative positions of components of the device and moving a constituting element in the form of a solid piece or block of material having a dielectric constant greater than 1 into or out of a part of the device in which there is an electric field in operation.

19. The method of claim 17, wherein varying the internal impedance of the FBAR device to tune the resonant frequency comprises at least one of varying a thickness of the first dielectric layer and varying the first overlap.

20. The method of claim 19, wherein varying the first overlap comprises moving the piezoelectric layer in a direction substantially parallel with a plane of the bottom electrode.

21. The method of claim 19, wherein varying the thickness of the first dielectric layer comprises moving the top electrode in a direction substantially perpendicular to a plane of the bottom electrode.

22. The method of claim 17, wherein the FBAR device further comprises a second dielectric layer in between the piezoelectric layer and the top electrode, the piezoelectric layer having a second overlap with the top electrode, the second overlap being defined by a projection of the piezoelectric layer onto the top electrode in a direction substantially perpendicular to a plane of the top electrode,

wherein varying the internal impedance of the FBAR device comprises at least one of varying the second overlap and varying a thickness of the second dielectric layer.