Mechanical resonating structures including a temperature compensation structure

• US 8,362,675 B2
• Filed: 11/07/2011
• Issued: 01/29/2013
• Est. Priority Date: 12/17/2008
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Sand 9, Inc. (Analog Devices, Inc.)
• Inventors: Chen, David M., Kuypers, Jan H., Gaidarzhy, Alexei, Zolfagharkhani, Guiti
• Primary Examiner(s): ROSENAU, DEREK JOHN
• Application Number:
  US13/290,405
• Publication Number:
  US 20120049980A1
• Time in Patent Office: 449 Days
• Field of Search: 310/313.R, 310/313.A, 310/313.B, 310/313.C, 310/313.D, 310/346
• US Class Current: 310/346
• CPC Class Codes: H03H 9/02102 of temperature influence cutting angles H03H9/02015
• CPC Class Codes: H03H 9/02228 Guided bulk acoustic wave devices or Lamb wave devices having interdigital transducers situated in parallel planes on either side of a piezoelectric layer
• CPC Class Codes: H03H 9/02448 of temperature influence
• CPC Class Codes: H03H 9/02574 of combined substrates, multilayered substrates, piezoelectrical layers on not-piezoelectrical substrate
• CPC Class Codes: H03H 9/02834 of temperature influence cut angles H03H9/02543

Abstract

Mechanical resonating structures are described, as well as related devices and methods. The mechanical resonating structures may have a compensating structure for compensating temperature variations.

Claims

1. A device comprising:

a mechanical resonating structure configured to support Lamb waves, the mechanical resonating structure including;

an active layer; and

a multi-layer compensating structure coupled to the active layer, the multi-layer compensating structure comprising;

first and second layers each having a stiffness that increases with increasing temperature over at least a first temperature range; and

a third layer between the first layer and the second layer, the third layer being formed of a material different than a material of which at least one of the first and second layers is formed.

2. The device of claim 1, wherein the active layer comprises a piezoelectric material.

3. The device of claim 1, wherein the multi-layer compensating structure is configured to provide the mechanical resonating structure with a temperature coefficient of frequency (TCF) having an absolute value of less than 10 ppm/K over a second temperature range from approximately −

40°

C. to approximately 85°

C.

4. The device of claim 3, wherein the TCF is approximately 0 ppm/K over a range of at least 5°

C. within the second temperature range.

5. The device of claim 1, wherein the multi-layer compensating structure is configured to provide the mechanical resonating structure with a TCF having an absolute value of less than 4 ppm/K over a second temperature range spanning at least 40°

C. and centered approximately at 25°

C.

6. The device of claim 5, wherein the absolute value of the TCF is less than 0.5 ppm/K.

7. The device of claim 1, wherein the active layer comprises aluminum nitride.

8. The device of claim 1, wherein the first layer and the second layer of the multi-layer compensating structure are formed of a first material.

9. The device of claim 1, wherein the first layer and the second layer of the multi-layer compensating structure have approximately the same thickness as each other.

10. The device of claim 1, wherein the first layer is formed of silicon dioxide.

11. The device of claim 1, wherein the third layer is formed of a material selected from the group consisting of silicon, silicon carbide, sapphire, quartz, germanium, gallium arsenide, aluminum nitride and diamond.

12. The device of claim 1, wherein the first temperature range spans at least 100°

C.

13. The device of claim 1, wherein the first temperature range is between −

40°

C. and 85°

C.

14. The device of claim 1, wherein the active layer is formed of silicon.

15. The device of claim 1, wherein the active layer is formed on the compensating structure.

16. A device comprising:

a resonating structure configured to support Lamb waves and including;

an active layer; and

a multi-layer compensating structure coupled to the active layer, the multi-layer compensating structure comprising

first and second layers each having a stiffness that increases with increasing temperature over at least a first temperature range, and

a third layer between the first and second layers,

wherein the first layer of the multi-layer compensating structure is formed of a first material and wherein the third layer is formed of a second material different than the first material, and

wherein the first material is silicon dioxide and the second material is silicon, and wherein a ratio of a total thickness of one or more layers of the resonating structure comprising the first material to a total thickness of one or more layers of the resonating structure comprising the second material is between 1;

0.75 and 1;

2.

17. The device of claim 16, wherein the active layer comprises a piezoelectric material.

18. The device of claim 17, wherein the multi-layer compensating structure is configured to provide the resonating structure with a temperature coefficient of frequency (TCF) having an absolute value of less than 10 ppm/K over a second temperature range from approximately −

40°

C. to approximately 85°

C.

19. The device of claim 18, wherein the active layer is formed of aluminum nitride.

20. A device comprising:

a multi-layer resonating structure including;

an active layer configured to support Lamb waves; and

a multi-layer compensating structure coupled to the active layer, the multi-layer compensating structure comprising;

first and second layers each having a stiffness that increases with increasing temperature over at least a first temperature range, and

a third layer formed of silicon, wherein the third layer is between the first and second layers, and wherein the first layer and/or the second layer is not formed of silicon.

21. The device of claim 20, wherein the active layer comprises a piezoelectric material.

22. The device of claim 20, wherein the first temperature range spans at least 100°

C.