Tunable and switchable resonator and filter structures in single crystal piezoelectric MEMS devices using bimorphs

• US 9,117,593 B2
• Filed: 11/04/2013
• Issued: 08/25/2015
• Est. Priority Date: 11/02/2012
• Status: Active Grant

• Current Assignee: Qorvo US, Inc. (Qorvo, Inc.)
• Original Assignee: RF Micro Devices Incorporated (Qorvo, Inc.)
• Inventors: Bhattacharjee, Kushal
• Primary Examiner(s): Summons, Barbara
• Application Number:
  US14/071,173
• Publication Number:
  US 20140125431A1
• Time in Patent Office: 659 Days
• Field of Search: 333/186, 310/332
• US Class Current: 1/1
• CPC Class Codes: B81B 2201/018 Switches not provided for in B81B2201/014 - B81B2201/016
• CPC Class Codes: B81B 2201/0271 Resonators; ultrasonic resonators
• CPC Class Codes: B81B 2201/032 Bimorph and unimorph actuators, e.g. piezo and thermo
• CPC Class Codes: B81B 3/0086 Electrical characteristics, e.g. reducing driving voltage, improving resistance to peak voltage
• CPC Class Codes: H01G 5/18 due to change in inclination, e.g. by flexing, by spiral wrapping
• CPC Class Codes: H03H 2009/241 Bulk-mode MEMS resonators
• CPC Class Codes: H03H 9/02275 Comb electrodes
• CPC Class Codes: H03H 9/02409 by application of a DC-bias voltage H03H9/02417 takes precedence
• CPC Class Codes: H03H 9/2405 of microelectro-mechanical resonators
• CPC Class Codes: H03H 9/2463 Clamped-clamped beam resonators
• CPC Class Codes: H03H 9/462 Microelectro-mechanical filters
• CPC Class Codes: H03H 9/467 Post-fabrication trimming of parameters, e.g. center frequency

Abstract

A MEMS device includes a substrate, one or more anchors formed on a first surface of the substrate, and a piezoelectric layer suspended over the first surface of the substrate by the one or more anchors. Notably, the piezoelectric layer is a bimorph including a first bimorph layer and a second bimorph layer. A first electrode may be provided on a first surface of the piezoelectric layer facing the first surface of the substrate, such that the first electrode is in contact with the first bimorph layer of the piezoelectric layer. A second electrode may be provided on a second surface of the piezoelectric layer opposite the substrate, such that the second electrode is in contact with the second bimorph layer of the piezoelectric layer. The second electrode may include a first conducting section and a second conducting section, which are inter-digitally dispersed on the second surface.

Claims

1. A micro-electrical-mechanical system (MEMS) device comprising:

a substrate;

one or more anchors formed on a first surface of the substrate;

a piezoelectric layer suspended over the first surface of the substrate by the one or more anchors, wherein the piezoelectric layer is a piezoelectric bimorph;

a first electrode on a first surface of the piezoelectric layer facing the first surface of the substrate; and

a second electrode on a second surface of the piezoelectric layer opposite the first surface, the second electrode including a first conducting section and a second conducting section, which are inter-digitally dispersed on the second surface.

2. The MEMS device of claim 1 wherein a DC voltage is applied between the first electrode and the second electrode in order to vary a capacitance between the first electrode and the second electrode.

3. The MEMS device of claim 1 wherein a DC voltage is applied between the first electrode and the second electrode in order to vary a resonant frequency of the piezoelectric layer.

4. The MEMS device of claim 3 wherein varying the resonant frequency of the piezoelectric layer changes a filter response between the first conducting section and the second conducting section of the second electrode.

5. The MEMS device of claim 1 wherein the piezoelectric bimorph comprises a first bimorph layer and a second bimorph layer.

6. The MEMS device of claim 5 wherein the first electrode is in contact with the first bimorph layer and the second electrode is in contact with the second bimorph layer.

7. The MEMS device of claim 6 wherein a DC voltage is applied between the first electrode and the second electrode in order to vary a capacitance between the first electrode and the second electrode.

8. The MEMS device of claim 6 wherein a DC voltage is applied between the first electrode and the second electrode in order to vary a resonant frequency of the piezoelectric layer.

9. The MEMS device of claim 8 wherein varying the resonant frequency of the piezoelectric layer changes a filter response between the first conducting section and the second conducting section of the second electrode.

10. The MEMS device of claim 5 wherein the first bimorph layer and the second bimorph layer comprise a single crystal piezoelectric material having a uniform crystalline orientation.

11. The MEMS device of claim 10 wherein the uniform crystalline orientation of the first bimorph layer is defined by a first set of Euler angles, and the uniform crystalline orientation of the second bimorph layer is defined by a second set of Euler angles.

12. The MEMS device of claim 11 wherein the first set of Euler angles is different from the second set of Euler angles.

13. A micro-electrical-mechanical system (MEMS) device comprising:

a substrate;

one or more anchors formed on a first surface of the substrate;

a piezoelectric layer suspended over the first surface of the substrate by the one or more anchors, wherein the piezoelectric layer is a piezoelectric bimorph;

a first electrode on a first surface of the piezoelectric layer facing the first surface of the substrate;

a second electrode on a second surface of the piezoelectric layer opposite the first surface, the second electrode including a first conducting section and a second conducting section, which are inter-digitally dispersed on the second surface; and

a third electrode on the first surface of the substrate below the first electrode.

14. The MEMS device of claim 13 wherein a DC voltage is applied between the first electrode and the second electrode in order to vary a capacitance between the first electrode and the third electrode.

15. The MEMS device of claim 14 wherein a DC voltage is applied between the first electrode and the second electrode in order to selectively place the first electrode in contact with the third electrode.

16. The MEMS device of claim 13 wherein a DC voltage is applied between the first electrode and the second electrode in order to vary a resonant frequency of the piezoelectric layer.

17. The MEMS device of claim 16 wherein varying the resonant frequency of the piezoelectric layer changes a filter response between the first conducting section and the second conducting section of the second electrode.

18. The MEMS device of claim 13 wherein the piezoelectric bimorph comprises a first bimorph layer and a second bimorph layer.

19. The MEMS device of claim 18 wherein the first electrode is in contact with the first bimorph layer and the second electrode is in contact with the second bimorph layer.

20. The MEMS device of claim 19 wherein a DC voltage is applied between the first electrode and the second electrode in order to vary a capacitance between the first electrode and the third electrode.

21. The MEMS device of claim 19 wherein a DC voltage is applied between the first electrode and the second electrode in order to selectively place the first electrode in contact with the third electrode.

22. The MEMS device of claim 19 wherein a DC voltage is applied between the first electrode and the second electrode in order to vary a resonant frequency of the piezoelectric layer.

23. The MEMS device of claim 22 wherein varying the resonant frequency of the piezoelectric layer changes a filter response between the first conducting section and the second conducting section of the second electrode.

24. The MEMS device of claim 18 wherein the first bimorph layer and the second bimorph layer comprise a single crystal piezoelectric material having a uniform crystalline orientation.

25. The MEMS device of claim 24 wherein the uniform crystalline orientation of the first bimorph layer is defined by a first set of Euler angles, and the uniform crystalline orientation of the second bimorph layer is defined by a second set of Euler angles.

26. The MEMS device of claim 25 wherein the first set of Euler angles is different from the second set of Euler angles.

27. A micro-electrical-mechanical system (MEMS) device comprising:

a substrate;

one or more anchors formed on a first surface of the substrate, each of the one or more anchors comprising at least one piezoelectric anchor layer, wherein the at least one piezoelectric anchor layer is a piezoelectric bimorph;

a piezoelectric layer suspended over the first surface of the substrate by the one or more anchors;

a first electrode on a first surface of the piezoelectric anchor layer facing the first surface of the substrate; and

a second electrode on a second surface of the piezoelectric anchor layer and the piezoelectric layer opposite the first surface, the second electrode including a first conducting section and a second conducting section, which are inter-digitally dispersed on the second surface.

28. The MEMS device of claim 27 wherein a DC voltage is applied between the first electrode and the second electrode in order to vary a capacitance between the first conducting section of the second electrode and the second conducting section of the second electrode.

29. The MEMS device of claim 27 wherein a DC voltage is applied between the first electrode and the second electrode in order to vary a resonant frequency of the piezoelectric layer.

30. The MEMS device of claim 29 wherein varying a resonant frequency of the piezoelectric layer changes a filter response between the first conducting section and the second conducting section of the second electrode.