Thin film bulk acoustic resonator filters with a piezoelectric layer of lead scandium tantalum oxide

• US 6,774,746 B2
• Filed: 04/02/2002
• Issued: 08/10/2004
• Est. Priority Date: 05/24/2000
• Status: Expired due to Term

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: TDK Corporation
• Inventors: Su, Qingxin, Komuro, Eiju, Whatmore, Roger W., Kirby, Paul B.
• Primary Examiner(s): Summons, Barbara
• Application Number:
  US10/031,240
• Publication Number:
  US 20020118079A1
• Time in Patent Office: 861 Days
• Field of Search: 333/186-192, 310/312
• US Class Current: 333/189
• CPC Class Codes: H03H 2003/0471 of a plurality of resonators at different frequencies
• CPC Class Codes: H03H 9/605 consisting of a ladder configuration

Abstract

An electric filter comprises a plurality of thin film bulk acoustic resonators arranged in series and in parallel which have different thicknesses of one or more non-piezoelectric layers, for example top electrode.

Claims

1. An electric filter comprising a plurality of thin film bulk acoustic resonators (FBARs) linked in a series/parallel arrangement wherein:

each resonator is made up of a thin piezoelectric layer made of a piezoelectric material and sandwiched between two metal electrodes, and other layers of materials;

the thicknesses of the non-piezoelectric layers in the FBARs in the filter are varied one-from another;

the filter has two close-in rejections, at least one of which is deeper as compared with a case where the thicknesses of respective layers in the FBARs are the same among all the FBARs; and

the piezoelectric material is substantially lead scandium tantalum oxide.

2. An electric filter as described in claim 1, wherein the piezoelectric sandwich structure is supported on a thin membrane layer.

3. An electric filter as described in claim 1, wherein the piezoelectric sandwiched structure is supported on an acoustic reflective stack.

4. An electric filter as described in claim 1, wherein the layer whose thickness is varied from one FBAR to another is the top electrode.

5. An electric filter as described in claim 1, wherein the layer whose thickness is varied from one FBAR to another is the bottom electrode.

6. An electric filter as described in claim 1, wherein the layer whose thickness is varied from one FBAR to another is an underlying membrane.

7. An electric filter as described in claim 6, wherein the underlying membrane is silicon nitride.

8. An electric filter as described in claim 6, wherein the underlying membrane is silicon oxide.

9. An electric filter as described in claim 1, wherein the layer whose thickness is varied from one FBAR to another is an overlying dielectric layer.

10. An electric filter as described in claim 9, wherein the overlying dielectric layer is silicon nitride.

11. An electric filter as described in claim 9, wherein the overlying dielectric layer is silicon oxide.

12. An electric filter as described in claim 1, wherein the layer whose thickness is varied from one FBAR to another is an overlying metal layer.

13. An electric filter according to claim 1 comprising a plurality of FBARs linked in series and a plurality of FBARs linked in parallel.

14. An electric filter as described in claim 1, wherein the metal electrodes are substantially gold.

15. An electric filter as described in claim 1, wherein the metal electrodes are substantially aluminium.

16. An electric filter as described in claim 1, wherein the metal electrodes are substantially platinum.

17. An electric filter as described in claim 1, wherein the variation in the thickness of one of the layers is produced by etching by excimer laser pulses.

18. An electric filter as described in claim 1, wherein the variation in the thickness of one of the layers is produced by wet etching.

19. An electric filter as described in claim 1, wherein the variation in the thickness of one of the layers is produced by ion milling.

20. An electric filter as described in claim 1, wherein the variation in the thickness of one of the layers is produced by reactive ion etching.

21. An electric filter comprising at least one FBAR in series and at least one FBAR in parallel, each FBAR having a piezoelectric layer made of a piezoelectric material and sandwiched between two electrodes, wherein:

the thicknesses of one or more non-piezoelectric layers in the series FBAR are different from those in the parallel FRAR;

the filter has a lower minimum insertion loss in a band pass area as compared with a case where the thicknesses of respective layers in the FBARs are the same among all the FBARs; and

the piezoelectric material is substantially lead scandium tantalum oxide.

22. An electric filter according to claim 21, wherein the thickness of at least one electrode is different between the FBAR in series and the FBAR in parallel.

23. An electric filter according to claim 21, wherein at least one additional layer is provided over the top electrode or under the bottom electrode.

24. An electric filter according to claim 23 wherein the thickness of the additional layer is different between the FBAR in series and the FBAR in parallel.

25. An electric filter comprising at least one FBAR in series and at least one FBAR in parallel, each FBAR having a piezoelectric layer made of a piezoelectric material and sandwiched between two electrodes wherein:

the thicknesses of one or more non-piezoelectric layers in the series FBAR are different from those in the parallel FBAR;

the filter has two close-in rejections, at least one of which is deeper as compared with a case where the thicknesses of respective layers in the FBARs are the same among all the FBARs; and

the piezoelectric material is substantially lead scandium tantalum oxide.

26. An electric filter according to claim 25, wherein the thickness of at least one electrode is different between the FBAR in series and the FBAR in parallel.

27. An electric filter according to claim 25, wherein at least one additional layer is provided over the top electrode or under the bottom electrode.

28. An electric filter according to claim 27 wherein the thickness of the additional layer is different between the FBAR in series and the FBAR in parallel.

29. An electric filter comprising a plurality of thin film bulk acoustic resonators (FBARs) linked in a series/parallel arrangement wherein:

each resonator is made up of a thin piezoelectric layer made of a piezoelectric material and sandwiched between two metal electrodes, and other layers of materials;

the thicknesses of the non-piezoelectric layers in the FBARs in the filter are varied one from another;

the filter has a lower minimum insertion loss in a band pass area as compared with a case where the thicknesses of respective layers in the FBARs are the same among all the FBARs; and

the piezoelectric material is substantially lead scandium tantalum oxide.

30. An electric filter according to claim 29, comprising a plurality of FBARs linked in series and a plurality of FBARs linked in parallel.

31. An electric filter as described in claim 29, wherein the piezoelectric sandwich structure is supported on a thin membrane layer.

32. An electric filter as described in claim 29, wherein the piezoelectric sandwiched structure is supported on an acoustic reflective stack.

33. An electric filter as described in claim 29, wherein the layer whose thickness is varied from one FBAR to another is the top electrode.

34. An electric filter as described in claim 29, wherein the layer whose thickness is varied from one FBAR to another is the bottom electrode.

35. An electric filter as described in claim 29, wherein the layer whose thickness is varied from one FBAR to another is an underlying membrane.

36. An electric filter as described in claim 35, wherein the underlying membrane is silicon nitride.

37. An electric filter as described in claim 35, wherein the underlying membrane is silicon oxide.

38. An electric filter as described in claim 29, wherein the layer whose thickness is varied from one FBAR to another is an overlying dielectric layer.

39. An electric filter as described in claim 38, wherein the overlying dielectric layer is silicon nitride.

40. An electric filter as described in claim 38, wherein the overlying dielectric layer is silicon nitride.

41. An electric filter as described in claim 29, wherein the layer whose thickness is varied from one FBAR to another is an overlying metal layer.

42. An electric filter as described in claim 29, wherein the metal electrodes are substantially gold.

43. An electric filter as described in claim 29, wherein the metal electrodes are substantially aluminum.

44. An electric filter as described in claim 29, wherein the metal electrodes are substantially platinum.

45. An electric filter as described in claim 29, wherein the variation in the thickness of one of the layers is produced by etching by excimer laser pulses.

46. An electric filter as described in claim 29, wherein the variation in the thickness of one of the layers is produced by wet etching.

47. An electric filter as described in claim 29, wherein the variation in the thickness of one of the layers is produced by ion milling.

48. An electric filter as described in claim 29, wherein the variation in the thickness of one of the layers is produced by reactive ion etching.