Temperature-compensated film bulk acoustic resonator (FBAR) devices

• US 20050110598A1
• Filed: 10/29/2004
• Published: 05/26/2005
• Est. Priority Date: 10/30/2003
• 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: Larson, John D. III
• Granted Patent: US 7,408,428 B2
• Time in Patent Office: Days
• US Class Current: 333/191
• CPC Class Codes: H03H 9/02102 of temperature influence cutting angles H03H9/02015
• CPC Class Codes: H03H 9/132 characterized by a particular shape
• CPC Class Codes: H03H 9/175 Acoustic mirrors
• CPC Class Codes: H03H 9/584 Coupled Resonator Filters [CFR]
• CPC Class Codes: H03H 9/587 Air-gaps
• CPC Class Codes: H03H 9/589 Acoustic mirrors
• 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. The FBAR stack comprises an FBAR and a temperature-compensating element. The FBAR is characterized by a resonant frequency having a temperature coefficient, and 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 depends at least in part. The temperature-compensating element has a temperature coefficient opposite in sign to the temperature coefficient of the piezoelectric element.

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 element having a temperature coefficient opposite in sign to the temperature coefficient of the piezoelectric element.

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

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

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

5. The FBAR device of claim 2, 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.

6. The FBAR device of claim 5, in which the temperature-compensating element comprises a temperature-compensating layer juxtaposed with one of the electrodes of each of the FBARs.

7. The FBAR device of claim 6, in which in each of the FBARs, the temperature-compensating layer is between the one of the electrodes and the piezoelectric element thereof.

8. The FBAR device of claim 6, in which in each of the FBARs, the one of the electrodes is juxtaposed with the acoustic decoupler.

9. The FBAR device of claim 5, in which in each of the FBARs, the one of the electrodes is juxtaposed with the acoustic decoupler.

10. The FBAR device of claim 5, 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 electrical circuit interconnecting the upper FBARs.

11. The FBAR device of claim 10, in which the temperature-compensating element comprises a temperature-compensating layer juxtaposed with one of the electrodes of each of the FBARs.

12. The FBAR device of claim 11, in which in each of the FBARs, the temperature-compensating layer is between the one of the electrodes and the piezoelectric element thereof.

13. The FBAR device of claim 11, in which in each of the FBARs, the one of the electrodes is juxtaposed with the acoustic decoupler.

14. The FBAR device of claim 10, in which in each of the FBARs, the one of the electrodes is juxtaposed with the acoustic decoupler.

15. 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.

16. The FBAR device of claim 15, in which the temperature-compensating element comprises a temperature-compensating layer juxtaposed with one of the electrodes of each of the FBARs.

17. The FBAR device of claim 1, in which the temperature-compensating element comprises a temperature-compensating layer embedded in the piezoelectric element.

18. The FBAR device of claim 17, 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.

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

20. The FBAR device of claim 18, in which:

the lower FBAR, the upper 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, an acoustic decoupler 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.

21. The FBAR device of claim 20 in which the temperature-compensating element comprises a temperature-compensating layer embedded in the piezoelectric element of each of the FBARs.

22. The FBAR device of claim 17, 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.

23. The FBAR device of claim 22, in which the temperature-compensating element comprises a temperature-compensating layer embedded in the piezoelectric element of each of the FBARs.

24. The FBAR device of claim 1, in which the temperature-compensating element comprises one of the electrodes.

25. The FBAR device of claim 24, in which:

the FBAR is a lower FBAR;

the FBAR device additionally comprises;

an upper FBAR stacked on the lower FBAR, the upper FBAR comprising a piezoelectric element, and

an acoustic decoupler between the FBARs; and

the temperature-compensating element additionally comprises opposed temperature-compensating layers between which the piezoelectric element of the upper FBAR is located.

26. The FBAR device of claim 25, in which the temperature-compensating element comprises one of the electrodes of each of the FBARs.

27. The FBAR device of claim 25, in which:

the lower FBAR, the upper 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, an acoustic decoupler 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.

28. The FBAR device of claim 27, in which the temperature-compensating element comprises one of the electrodes of each of the FBARs.

29. The FBAR device of claim 24, 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.

30. The FBAR device of claim 29, in which the temperature-compensating element comprises one of the electrodes of each of the FBARs.

31. The FBAR device of claim 1, in which the temperature-compensating element comprises a niobium-molybdenum (Nb—

Mo) alloy.

32. The FBAR device of claim 31, in which the niobium-molybdenum alloy has a molybdenum fraction in the range from about 17% to about 51%.

33. The FBAR device of claim 31, in which the niobium-molybdenum alloy has a molybdenum fraction in the range from about 32% to about 36%.

34. The FBAR device of claim 1, in which the temperature-compensating element comprises a cobalt-palladium (Co-Pd) alloy.

35. The FBAR device of claim 34, in which the cobalt-palladium alloy has a palladium fraction in the range from about 92% to about 96%.

36. The FBAR device of claim 34, in which the cobalt-palladium alloy has a palladium fraction in the range from about 93% to about 95%.

37. The FBAR device of claim 1, in which the temperature-compensating element comprises a ferroelectric material.

38. The FBAR device of claim 37, in which the ferroelectric material comprises lead nickel niobate (Pb(Ni_xNb_1-x)O₃ in which the nickel fraction x is about one third.

39. The FBAR device of claim 37, in which the ferroelectric material comprises nepheline (KAISiO₄)(NaAlSiO₄)₃.

40. The FBAR device of claim 37, in which the ferroelectric material comprises zirconium tungstate (ZrW₂O₈).

41. 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 element having a temperature coefficient opposite in sign to the temperature coefficient of the acoustic propagation element.

42. The FBAR device of claim 41, in which the temperature-compensating element comprises a niobium-molybdenum (Nb—

Mo) alloy.

43. The FBAR device of claim 41, in which the temperature-compensating element comprises a cobalt-palladium (Co—

Pd) alloy.

44. The FBAR device of claim 41, in which the temperature-compensating element comprises a ferroelectric material.

45. The FBAR device of claim 44, in which the ferroelectric material comprises lead nickel niobate (Pb(Ni_x Nb_1-x)O₃ in which the nickel fraction x is about one third.

46. The FBAR device of claim 44, in which the ferroelectric material comprises nepheline (KAISiO₄)(NaAlSiO₄)₃.

47. The FBAR device of claim 44, in which the ferroelectric material comprises zirconium tungstate (ZrW₂O₈).