Contour-mode piezoelectric micromechanical resonators

• US 7,492,241 B2
• Filed: 06/02/2005
• Issued: 02/17/2009
• Est. Priority Date: 06/02/2005
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Stephanou, Philip J., Pisano, Albert P., Piazza, Gianluca
• Primary Examiner(s): Takaoka; Dean O
• Application Number:
  US11/145,552
• Publication Number:
  US 20060273867A1
• Time in Patent Office: 1,356 Days
• Field of Search: 333/186, 333/187, 333/189, 310/321
• US Class Current: 333/189
• CPC Class Codes: H03H 2003/027 the resonators or networks being of the microelectro-mechanical [MEMS] type
• 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 2009/02354 applied along the periphery, e.g. at nodal points of the ring
• CPC Class Codes: H03H 2009/241 Bulk-mode MEMS resonators
• CPC Class Codes: H03H 3/02 for the manufacture of piezoelectric or electrostrictive resonators or networks H03H3/08 takes precedence
• CPC Class Codes: H03H 9/132 characterized by a particular shape
• CPC Class Codes: H03H 9/171 implemented with thin-film techniques, i.e. of the film bulk acoustic resonator [FBAR] type
• 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
• CPC Class Codes: H03H 9/205 having multiple resonators crystal tuning forks H03H9/21
• CPC Class Codes: H03H 9/54 comprising resonators of piezoelectric or electrostrictive material H03H9/64 takes precedence
• CPC Class Codes: H03H 9/542 including passive elements H03H9/545 takes precedence
• CPC Class Codes: Y10T 29/42 Piezoelectric device making
• CPC Class Codes: Y10T 29/49005 Acoustic transducer

Abstract

A contour mode micromechanical piezoelectric resonator. The resonator has a bottom electrode; a top electrode; and a piezoelectric layer disposed between the bottom electrode and the top electrode. The piezoelectric resonator has a planar surface with a cantilevered periphery, dimensioned to undergo in-plane lateral displacement at the periphery. The resonator also includes means for applying an alternating electric field across the thickness of the piezoelectric resonator. The electric field is configured to cause the resonator to have a contour mode in-plane lateral displacement that is substantially in the plane of the planar surface of the resonator, wherein the fundamental frequency for the displacement of the piezoelectric resonator is set in part lithographically by the planar dimension of the bottom electrode, the top electrode or the piezoelectric layer.

Claims

1. A contour mode micromechanical piezoelectric resonator, comprising:

a bottom electrode;

a top electrode;

a piezoelectric layer disposed between said bottom electrode and said top electrode, said piezoelectric resonator having a planar surface having a cantilevered periphery, dimensioned to undergo in-plane lateral displacement at said periphery;

one or more tethers that anchor said piezoelectric resonator to a substrate or other resonators, wherein said tethers have width chosen from a group consisting of about one quarter-wavelength and an odd multiple of about one quarter-wavelength of said fundamental frequency of said resonator; and

means for applying an alternating electric field across the thickness of said piezoelectric resonator, said electric field configured to cause said resonator to have a contour mode in-plane lateral displacement that is substantially in the plane of said planar surface, wherein the fundamental frequency for the displacement of said piezoelectric resonator is set in part lithographically by the planar dimensions of one of said bottom electrode, said top electrode and said piezoelectric layer.

2. The resonator of claim 1 wherein said means for applying an alternating electric field comprise electrical interconnects to the top electrode and the bottom electrode.

3. The resonator of claim 1 wherein said bottom electrode is lithographically patterned to excite a specific region or regions of the piezoelectric resonator.

4. The resonator of claim 1 wherein said top electrode is lithographically patterned to excite a specific region or regions of the piezoelectric resonator.

5. The resonator of claim 1 wherein said piezoelectric layer is a layer selected from the group consisting of aluminum nitride, gallium nitride, aluminum gallium arsenide, zinc oxide, quartz, and combinations thereof.

6. The resonator of claim 1 wherein said bottom or said top electrode is made from a material selected from the group consisting of aluminum, platinum, tungsten, molybdenum, ruthenium, chrome, gold, titanium, doped polycrystalline silicon, and combinations thereof.

7. The resonator of claim 1 wherein said piezoelectric layer has a shape selected from the group consisting of a rectangle, a circle, a polygon, a circular annulus, a rectangular annulus, a polygonal annulus and combinations thereof.

8. The resonator of claim 1 being a part of an array of resonators formed by mechanically coupling the resonators in said array to one another using said tethers.

9. The resonator of claim 1 wherein said one or more tethers are configured for use as electrical connectors for exchanging electrical signals with the piezoelectric resonator.

10. The resonator of claim 9 being one of more than one resonator and wherein said more than one resonators are electrically cascaded to form a network of said resonators.

11. The resonator of claim 10 wherein said network is a Pi, T or L network.

12. The resonator of claim 11 being a part of a band pass filter circuit formed using a series of either of said Pi, T or L networks.

13. The resonator of claim 11 comprising 2 or more resonators that are electrically connected.

14. The resonator of claim 11 comprising electrical connectors used to route the signal from one resonator to the next.

15. The resonator of claim 1 being one of more than one resonator and wherein said more than one resonators are connected and arranged as a band-pass filter circuit.

16. The resonator of claim 1 comprising

means for applying a DC voltage across the thickness of the piezoelectric resonator, said DC voltage configured for tuning the center frequency of the resonator.

17. The resonator of claim 1 wherein said piezoelectric resonator is a part of a frequency reference in an oscillator circuit.

18. The resonator of claim 1 wherein said piezoelectric resonator is a part of a band pass filter circuit.