METHODS AND APPARATUS FOR TEMPERATURE CONTROL OF DEVICES AND MECHANICAL RESONATING STRUCTURES

• US 20100315179A1
• Filed: 05/17/2010
• Published: 12/16/2010
• Est. Priority Date: 06/04/2009
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Sand9, Inc.
• Inventors: Rebel, Reimund, Schoepf, Klaus Juergen
• Granted Patent: US 8,410,868 B2
• Time in Patent Office: Days
• US Class Current: 333/186
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H03H 2009/241 Bulk-mode MEMS resonators
• CPC Class Codes: H03H 9/02448 of temperature influence
• CPC Class Codes: H03H 9/08 Holders with means for regulating temperature
• CPC Class Codes: H03H 9/1057 for microelectro-mechanical devices
• CPC Class Codes: H03H 9/2405 of microelectro-mechanical resonators

Abstract

Methods and apparatus for temperature control of devices and mechanical resonating structures are described. A mechanical resonating structure may include a heating element and a temperature sensor. The temperature sensor may sense the temperature of the mechanical resonating structure, and the heating element may be adjusted to provide a desired level of heating. Optionally, additional heating elements and/or temperature sensors may be included.

Claims

1. A temperature compensated microelectromechanical systems (MEMS) resonating device, comprising:

a semiconductor substrate;

a suspended micromechanical resonating structure coupled to the semiconductor substrate by two or more flexible anchors;

at least one first electrode mechanically coupled to the suspended micromechanical resonating structure and configured to provide an electrical drive signal to the suspended micromechanical resonating structure to excite vibration of the suspended micromechanical resonating structure;

at least one second electrode mechanically coupled to the suspended micromechanical resonating structure and configured to sense the vibration of the suspended micromechanical resonating structure and produce an output signal indicative of the vibration;

a heating element formed on the suspended micromechanical resonating structure and coupled to control circuitry configured to control an amount of electrical current passing through the heating element; and

a temperature sensor formed on the suspended micromechanical resonating structure and configured to provide a temperature output signal indicative of a temperature of the suspended micromechanical resonating structure,

wherein the temperature sensor and heating element are coupled together in a feedback loop comprising the control circuitry.

2. The temperature compensated MEMS resonating device of claim 1, wherein the heating element and temperature sensor are formed on a same side of the suspended micromechanical resonating structure.

3. The temperature compensated MEMS resonating device of claim 1, wherein the suspended micromechanical resonating structure is substantially planar and has a top surface and a bottom surface, and wherein the heating element is formed on one of the top surface and the bottom surface, and wherein the temperature sensor is formed on the other of the top surface and the bottom surface.

4. A device, comprising:

a mechanical resonating structure including

a heating element configured to control a temperature of the mechanical resonating structure, and

a temperature sensor configured to detect the temperature of the mechanical resonating structure,

wherein the mechanical resonating structure is formed at least partially of a piezoelectric material.

5. The device of claim 4, wherein the mechanical resonating structure has a largest dimension of less than approximately 1000 microns.

6. The device of claim 4, wherein the heating element comprises a conductive trace.

7. The device of claim 6, wherein at least part of the conductive trace is formed of a metal.

8. The device of claim 6, wherein at least part of the conductive trace is formed of a conductive semiconductor material.

9. The device of claim 4, wherein the heating element comprises an electrode of the mechanical resonating structure.

10. The device of claim 4, wherein the heating element comprises a region of doped material.

11. The device of claim 10, wherein the doped material comprises a doped piezoelectric material.

12. The device of claim 10, wherein the doped material comprises a doped semiconductor material.

13. The device of claim 4, wherein the temperature sensor comprises a conductive trace.

14. The device of claim 13, wherein at least part of the conductive trace is formed of a metal.

15. The device of claim 13, wherein at least part of the conductive trace is formed of a conductive semiconductor material.

16. The device of claim 4, wherein the temperature sensor comprises an electrode of the mechanical resonating structure.

17. The device of claim 4, wherein the temperature sensor comprises a region of doped material.

18. The device of claim 17, wherein the doped material comprises a doped piezoelectric material.

19. The device of claim 17, wherein the doped material comprises a doped semiconductor material.

20. The device of claim 4, wherein the heating element and temperature sensor are configured in a feedback loop.

21. The device of claim 4, further comprising temperature control circuitry coupled to the temperature sensor and the heating element, and configured to receive an output signal of the temperature sensor indicative of the temperature of the mechanical resonating structure and to provide a control signal to the heating element to adjust an amount of heat produced by the heating element to set the temperature of the mechanical resonating structure to a target value.

22. The device of claim 4, wherein the mechanical resonating structure is coupled to a substrate having a front surface and a back surface, and wherein the heating element is a first heating element, and wherein the device further comprises a second heating element formed on the back surface of the substrate.

23. The device of claim 22, further comprising a cap wafer bonded to the substrate, and wherein the device further comprises a third heating element formed on a backside of the cap wafer.

24. The device of claim 23, wherein the cap wafer comprises integrated circuitry formed on a front side of the cap wafer.

25. The device of claim 24, wherein the temperature sensor is a first temperature sensor, and wherein the device further comprises a second temperature sensor formed on the front side of the cap wafer.

26. The device of claim 25, wherein the third heating element and the second temperature sensor are configured as at least part of a temperature control feedback loop.

27. The device of claim 4, further comprising a substrate to which the mechanical resonating structure is coupled, and further comprising a cap wafer bonded to the substrate.

28. The device of claim 27, wherein the heating element is a first heating element, and wherein the device further comprises a second heating element formed on a back side of the cap wafer.

29. The device of claim 28, wherein the cap wafer comprises integrated circuitry formed on a front side of the cap wafer.

30. The device of claim 28, wherein the temperature sensor is a first temperature sensor, and wherein the device further comprises a second temperature sensor formed on a front side of the cap wafer.

31. A device, comprising:

a substrate having a front surface and a back surface;

a mechanical resonating structure formed on the front surface of the substrate; and

a heating element formed on or within the substrate.

32. The device of claim 31, wherein the mechanical resonating structure has a largest dimension of less than approximately 100 microns.

33. The device of claim 32, wherein the substrate is a first substrate and the heating element is a first heating element, and wherein the apparatus further comprises a second substrate having a front surface and a back surface, the front surface of the second substrate being bonded to the front surface of the first substrate, and wherein the apparatus further comprises a second heating element formed on the back surface of the second substrate.

34. The device of claim 33, wherein the mechanical resonating structure comprises a third heating element.

35. The device of claim 34, wherein the mechanical resonating structure further comprises a temperature sensor.