Mechanical resonating structures including a temperature compensation structure

• US 8,629,599 B2
• Filed: 11/07/2011
• Issued: 01/14/2014
• 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:
  US13/290,385
• Publication Number:
  US 20120049965A1
• Time in Patent Office: 799 Days
• Field of Search: 310/313.R, 310/313.A, 310/313.B, 310/313.C, 310/313.D, 310/346
• US Class Current: 310/313.R
• 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 compensating structure coupled to the active layer, the compensating structure comprising

a first layer having a stiffness that increases with increasing temperature over at least a first temperature range,

a third layer having a stiffness that increases with increasing temperature over at least the first temperature range, and

a second layer between the first layer and the third layer.

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

3. The device of claim 2, wherein the piezoelectric material is aluminum nitride.

4. The device of claim 1, wherein the 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.

5. The device of claim 4, wherein the TCF has an absolute value of less than 3 ppm/K over the second temperature range.

6. The device of claim 4, wherein the TCF has an absolute value of less than 1 ppm/K over the second temperature range.

7. The device of claim 1, wherein the 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.

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

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

10. The device of claim 1, wherein the first layer of the compensating structure is formed of a first material and wherein the second layer is formed of a second material different than the first material.

11. The device of claim 10, wherein a ratio of a total thickness of one or more layers of the mechanical resonating structure comprising the first material to a thickness of the active layer is between 1:

0.1 and 1;

1.25.

12. The device of claim 10, wherein a ratio of a total thickness of one or more layers of the mechanical resonating structure comprising the first material to a thickness of the active layer is between 1:

0.2 and 1;

0.75.

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

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

15. The device of claim 1, wherein the first temperature range spans at least 200°

C.

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

55°

C. and 150°

C.

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

40°

C. and 85°

C.

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

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

20. The device of claim 1, wherein each of the first and third layers includes silicon dioxide, and wherein the second layer includes single crystal silicon.

21. The device of claim 20, wherein the silicon dioxide comprises thermal silicon dioxide.

22. The device of claim 1, wherein the first and third layers include silicon dioxide, and wherein the second layer includes a single crystal material.

23. The device of claim 22, wherein the silicon dioxide comprises thermal silicon dioxide.

24. The device of claim 1, wherein:

the mechanical resonating structure further includes at least one patterned electrode;

each of the first and third layers of the compensating structure includes thermal silicon dioxide;

the second layer of the compensating structure includes single crystal silicon; and

the device further comprises first and second anchors coupled to the mechanical resonating structure and substantially in plane with the mechanical resonating structure.

25. A device comprising:

a mechanical resonating structure configured to support Lamb waves, the mechanical resonating structure comprising an active layer and a compensation structure coupled to the active layer and configured to compensate temperature-induced variations in stiffness of at least the active layer, the compensation structure comprising a first layer, a second layer, and a third layer, wherein the first and third layers are formed of a first material and wherein the second layer is formed of a second material different than the first material, and wherein the second layer is disposed between the first layer and the third layer.