Film bulk acoustic resonator (FBAR) devices with temperature compensation

• US 7,561,009 B2
• Filed: 11/30/2005
• Issued: 07/14/2009
• Est. Priority Date: 11/30/2005
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Inventors: Grannen, Kevin J., Sridharan, Urupattur C., Lee, Donald E., Choy, John, Larson, John D. III, Feng, Hongjun, Rogers, Carrie A.
• Primary Examiner(s): Takaoka; Dean O
• Application Number:
  US11/291,674
• Publication Number:
  US 20070120625A1
• Time in Patent Office: 1,322 Days
• Field of Search: 333/189, 333/191, 333/187
• US Class Current: 333/187
• CPC Class Codes: H03H 2003/021 the resonators or networks being of the air-gap type
• CPC Class Codes: H03H 2003/0407 Temperature coefficient
• CPC Class Codes: H03H 3/04 for obtaining desired frequency or temperature coefficient
• CPC Class Codes: H03H 9/02102 of temperature influence cutting angles H03H9/02015
• CPC Class Codes: H03H 9/131 consisting of a multilayered structure
• CPC Class Codes: H03H 9/132 characterized by a particular shape
• CPC Class Codes: H03H 9/173 Air-gaps
• CPC Class Codes: H03H 9/584 Coupled Resonator Filters [CFR]
• CPC Class Codes: H03H 9/587 Air-gaps
• CPC Class Codes: H03H 9/605 consisting of a ladder configuration

Abstract

The temperature-compensated film bulk acoustic resonator (FBAR) device comprises an FBAR stack that comprises an FBAR characterized by a resonant frequency having a temperature coefficient and a temperature-compensating layer comprising doped silicon dioxide. The FBAR comprises opposed planar electrodes and a piezoelectric element between the electrodes. The piezoelectric element has a temperature coefficient on which the temperature coefficient of the resonant frequency of the FBAR depends at least in part.

Claims

1. A temperature-compensated film bulk acoustic resonator (FBAR) device, comprising:

an FBAR stack, comprising;

an FBAR characterized by a resonant frequency having a temperature coefficient, the FBAR comprising opposed planar electrodes and a piezoelectric element between the electrodes, the piezoelectric element having a temperature coefficient on which the temperature coefficient of the resonant frequency depends at least in part, and a temperature-compensating layer between the electrodes comprising doped silicon dioxide.

2. The FBAR device of claim 1, in which the temperature-compensating layer is juxtaposed with one of the electrodes.

3. The FBAR device of claim 2, in which the FBAR stack additionally comprises an additional temperature-compensating layer juxtaposed with the other of the electrodes, the additional temperature-compensating layer comprising doped silicon dioxide.

4. The FBAR device of claim 3, in which the additional temperature-compensating layer is located between the other of the electrodes and the piezoelectric element.

5. The FBAR device of claim 2, in which the temperature-compensating layer is located between the one of the electrodes and the piezoelectric element.

6. The FBAR device of claim 2, in which the one of the electrodes is located between the temperature-compensating layer and the piezoelectric element.

7. The FBAR device of claim 2, in which:

the FBAR is a lower FBAR; and

the FBAR stack additionally comprises;

an upper FBAR stacked on the lower FBAR, the upper FBAR comprising opposed planar electrodes and a piezoelectric element between the electrodes, and an acoustic decoupler between the FBARs.

8. The FBAR device of claim 7, in which the FBAR stack additionally comprises a temperature-compensating layer juxtaposed with one of the electrodes of each of the FBARs, the temperature-compensating layer comprising doped silicon dioxide.

9. The FBAR device of claim 8, in which, in each of the FBARs, the one of the electrodes is juxtaposed with the acoustic decoupler.

10. The FBAR device of claim 7, in which:

the first FBAR, the second FBAR and the acoustic decoupler constitute a first decoupled stacked bulk acoustic resonator (DSBAR);

the FBAR stack additionally comprises a second DSBAR, comprising a lower FBAR, an upper FBAR stacked on the lower FBAR, and an acoustic decoupler between the FBARs; and

the FBAR device additionally comprises;

a first electrical circuit interconnecting the lower FBARS, and a second electrieal circuit interconnecting the upper FBARs.

11. The FBAR device of claim 10, in which the FBAR stack additionally comprises a temperature-compensating layer juxtaposed with one of the electrodes of each of the FBARs, the temperature-compensating layer comprising doped silicon dioxide.

12. The FBAR device of claim 2, in which:

the FBAR is a first FBAR;

the FBAR stack additionally comprises one or more additional FBARs; and

the FBARs are interconnected as a ladder filter.

13. The FBAR device of claim 12, in which the FBAR stack additionally comprises a temperature-compensating layer juxtaposed with one of the electrodes of each of the FBARs, the temperature-compensating layer comprising doped silicon dioxide.

14. The FBAR device of claim 1, in which the temperature-compensating layer is embedded in the piezoelectric element.

15. The FBAR device of claim 14, in which:

the FBAR is a lower FBAR; and

the FBAR device additionally comprises;

an upper FBAR stacked on the lower FBAR, the upper FBAR comprising opposed planar electrodes and a piezoelectric element between the electrodes, and an acoustic decoupler between the FBARs.

16. The FBAR device of claim 15, in which the FBAR stack additionally comprises a temperature-compensating layer embedded in the piezoelectric element of each of the FBARs, the temperature-compensating layer comprising doped silicon dioxide.

17. The FBAR device of claim 15, in which:

the lower FBAR, the upper FBAR and the acoustic decoupled constitute a first decoupled stacked bulk acoustic resonator (DSBAR);

the FBAR stack additionally comprises a second DSBAR, comprising a lower FBAR, an upper FBAR, an acoustic decoupled between the FBARs; and

the FBAR device additionally comprises;

a first electrical circuit interconnecting the lower FBARs, and a second electrical circuit interconnecting the upper FBARs.

18. The FBAR device of claim 17, in which the FBAR stack additionally comprises a temperature-compensating layer embedded in the piezoelectric element of each of the FBARs.

19. The FBAR device of claim 15, in which:

the FBAR is a first FBAR;

the FBAR stack additionally comprises one or more additional FBARs; and

the FBARs are interconnected as a ladder filter.

20. The FBAR device of claim 19, in which the FBAR stack additionally comprises a temperature-compensating layer embedded in the piezoelectric element of each of the FBARs, the temperature-compensating layer comprising doped silicon dioxide.

21. The FBAR device of claim 1, in which:

the FBAR is a lower FBAR;

the FBAR stack additionally comprises;

an upper FBAR stacked on the lower FBAR, and an acoustic decoupler between the FBARs, the acoustic decoupler comprising a Bragg structure; and

the temperature-compensating layer constitutes a layer of the Bragg structure.

22. A temperature-compensated film bulk acoustic resonator (FBAR) device, comprising:

an FBAR stack, comprising;

an FBAR characterized by a resonant frequency having a temperature coefficient, the FBAR comprising opposed planar electrodes and a piezoelectric element between the electrodes, the piezoelectric element having a temperature coefficient on which the temperature coefficient of the resonant frequency depends at least in part, and a temperature-compensating layer between the electrodes comprising silicon dioxide doped with a group III element.

23. The FBAR device of claim 22, in which the group III element is boron.

24. The FBAR device of claim 22, in which the group III element is one of aluminum, gallium and indium.

25. The FBAR device of claim 22, in which the silicon dioxide is doped by implanting ions of the group III element.

26. The FBAR device of claim 22, in which the temperature-compensating layer is fabricated by depositing silicon dioxide by chemical vapor deposition (CVD).

27. The FBAR device of claim 26, in which the group III element is additionally deposited by CVD.

28. A temperature-compensated film bulk acoustic resonator (FBAR) device, comprising:

a substrate defining a cavity;

an FBAR stack suspended over the cavity, the FBAR stack comprising;

an FBAR characterized by a resonant frequency having a temperature coefficient, the FBAR comprising opposed planar electrodes and a piezoelectric element between the electrodes, the piezoelectric element having a temperature coefficient on which the temperature coefficient of the resonant frequency depends at least in pad, and a temperature-compensating layer between the electrodes comprising silicon dioxide implanted with ions of a group III element.

29. The FBAR device of claim 28, in which the group III element is boron.

30. The FBAR device of claim 28, in which the group III element is one of aluminum, gallium and indium.

31. A method of making an FBAR device, the method comprising:

providing a substrate having a cavity defined therein, the cavity filled with sacrificial material;

forming an FBAR stack over the sacrificial material, the forming comprising depositing between opposed electrodes a temperature-compensating layer comprising a doped temperature-compensating material; and

removing the sacrificial material from the cavity using an etchant that is incompatible with the temperature-compensating material in its undoped form.

32. The method of claim 31, in which the doped temperature-compensating material is doped silicon dioxide, the sacrificial material is phosphosilicate glass and the etchant is dilute hydrofluoric acid.

33. The method of claim 32, in which the silicon dioxide is doped with a group III element.

34. The method of claim 33, in which the group III element is boron.

35. The method of claim 31, in which depositing the temperature-compensating layer comprises depositing a layer of silicon dioxide and implanting ions of the group III element into the silicon dioxide.

36. The method of claim 35, in which the group III element is boron.

37. An acoustic device, comprising an acoustic propagation path having a propagation time-related property, the propagation time-related property having a temperature coefficient, the acoustic propagation path comprising:

an acoustic propagation element having a temperature coefficient on which the propagation time-related property of the acoustic propagation path depends at least in part; and

a temperature-compensating layer comprising doped silicon dioxide between opposed electrodes, the doped silicon dioxide having a temperature coefficient opposite in sign to the temperature coefficient of the acoustic propagation element.

38. The acoustic device of claim 37, in which the silicon dioxide is doped with a group III element.