Temperature controlled MEMS resonator and method for controlling resonator frequency

• US 7,268,646 B2
• Filed: 10/17/2005
• Issued: 09/11/2007
• Est. Priority Date: 03/04/2004
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Partridge, Aaron, Lutz, Markus
• Primary Examiner(s): Summons; Barbara
• Application Number:
  US11/252,349
• Publication Number:
  US 20060033594A1
• Time in Patent Office: 694 Days
• Field of Search: 333186-188
• US Class Current: 333/186
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48227 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/01019 Potassium [K]
• CPC Class Codes: H01L 2924/01057 Lanthanum [La]
• CPC Class Codes: H01L 2924/01078 Platinum [Pt]
• CPC Class Codes: H01L 2924/01079 Gold [Au]
• CPC Class Codes: H03H 2009/02496 Horizontal, i.e. parallel to the substrate plane
• CPC Class Codes: H03H 2009/02511 Vertical, i.e. perpendicular to the substrate plane
• CPC Class Codes: H03H 2009/02527 Combined
• CPC Class Codes: H03H 9/02338 Suspension means
• CPC Class Codes: H03H 9/02401 by annealing
• CPC Class Codes: H03H 9/02448 of temperature influence
• CPC Class Codes: H03H 9/2426 in combination with other electronic elements
• CPC Class Codes: H03H 9/2463 Clamped-clamped beam resonators
• CPC Class Codes: H03H 9/2473 Double-Ended Tuning Fork [DETF] resonators
• CPC Class Codes: H03H 9/2478 Single-Ended Tuning Fork resonators

Abstract

There are many inventions described and illustrated herein. In one aspect, the present invention is directed to a temperature compensated microelectromechanical resonator as well as fabricating, manufacturing, providing and/or controlling microelectromechanical resonators having mechanical structures that include integrated heating and/or temperature sensing elements. In another aspect, the present invention is directed to fabricate, manufacture, provide and/or control microelectromechanical resonators having mechanical structures that are encapsulated using thin film or wafer level encapsulation techniques in a chamber, and including heating and/or temperature sensing elements disposed in the chamber, on the chamber and/or integrated within the mechanical structures. Other aspects of the inventions will be apparent from the detailed description and claims herein.

Claims

1. A MEMS resonator having a resonant frequency defined in relation to an operating temperature, comprising:

a first substrate anchor;

a beam structure mechanically coupled to the first substrate anchor;

a first heating element which is thermally coupled to the first substrate anchor;

an electrical source, electrically coupled to the first heating element, to provide an electrical current to the first heating element; and

wherein, in response to the electrical current, the first heating element conductively transfers heat to the first substrate anchor to maintain the temperature of the beam structure at the operating temperature or within a predetermined range of temperatures while the MEMS resonator is in operation.

2. The MEMS resonator of claim 1 further including an insulator, disposed between the first substrate anchor and the first heating element.

3. The MEMS resonator of claim 1 further including a thin film encapsulation structure to enclose the beam structure.

4. The MEMS resonator of claim 1 further including:

temperature sensing means for sensing the temperature of the beam structure; and

control circuitry, coupled to the temperature sensing means, to generate control information and provide the control information to the electrical source to maintain the beam structure at the operating temperature or within a predetermined range of temperatures while the MEMS resonator is in operation.

5. The MEMS resonator of claim 4 wherein the control circuitry, in response to data sensed by the temperature sensing means, generates the control information using a mathematical relationship or data contained in a look-up table.

6. The MEMS resonator of claim 1 wherein the beam structure comprises a single oscillating beam.

7. The MEMS resonator of claim 1 wherein the beam structure comprises a plurality of moveable beams wherein at least one moveable beam of the plurality of moveable beams is coupled to the first substrate anchor.

8. The MEMS resonator of claim 1 wherein the first substrate anchor includes a composite structure formed from a plurality of materials, wherein at least two of the materials in the plurality of materials have different thermal expansion coefficients.

9. The MEMS resonator of claim 1 wherein the beam structure includes a composite structure formed from a plurality of materials, wherein at least two of the materials in the plurality of materials have different thermal expansion coefficients.

10. The MEMS resonator of claim 1 further including an insulator, wherein the first heating element is juxtaposed the first substrate anchor and separated therefrom by the insulator.

11. The MEMS resonator of claim 1 further including

a second substrate anchor, wherein the beam structure is mechanically coupled to the second substrate anchor;

a second heating element which is thermally coupled to the second substrate anchor, wherein the electrical source is electrically coupled to the second heating element to provide an electrical current to the second heating element; and

wherein, in response to the electrical current, the second heating element conductively transfers heat to the second substrate anchor to maintain the temperature of the beam structure at the operating temperature or within a predetermined range of temperatures while the MEMS resonator is in operation.

12. A MEMS resonator having a resonant frequency defined in relation to an operating temperature, comprising:

a first substrate anchor;

a beam structure mechanically coupled to the first substrate anchor;

a first heating element which is disposed in the beam structure and thermally coupled thereto;

an electrical source, electrically coupled to the first heating element, to provide an electrical current to the first heating element; and

wherein in response to the electrical current, the first heating element transfers heat to the beam structure to maintain the temperature of the beam structure at the operating temperature or within a predetermined range of temperatures while the MEMS resonator is in operation.

13. The MEMS resonator of claim 12 wherein the first heating element includes a vertical profile to provide a corresponding heating profile within the beam structure.

14. The MEMS resonator of claim 12 wherein the first heating element includes a lateral profile to provide a corresponding heating profile within the beam structure.

15. The MEMS resonator of claim 12 further including a thin film encapsulation structure to enclose the beam structure.

16. The MEMS resonator of claim 12 further including control circuitry, coupled to the electrical source, to generate control information and provide the control information to the electrical source to maintain the beam structure at the operating temperature or within a predetermined range of temperatures while the MEMS resonator is in operation.

17. The MEMS resonator of claim 12 wherein the beam structure comprises a single oscillating beam.

18. The MEMS resonator of claim 12 wherein the beam structure comprises a plurality of moveable beams wherein at least one of the moveable beams is coupled to the first substrate anchor.

19. The MEMS resonator of claim 12 wherein the beam structure includes a composite structure formed from a plurality of materials, wherein at least two of the materials in the plurality of materials have different thermal expansion coefficients.

20. The MEMS resonator of claim 12 further including:

a second heating element which is thermally coupled to the first substrate anchor, wherein the electrical source is electrically coupled to the second heating element to provide an electrical current to the second heating element; and

wherein, in response to the electrical current, the second heating element transfers heat to the first substrate anchor to maintain the temperature of the beam structure at the operating temperature or within the predetermined range of temperatures while the MEMS resonator is in operation.

21. The MEMS resonator of claim 12 wherein the first heating element includes a vertical and lateral profile to provide a corresponding heating profile within the beam structure.

22. A method of controlling the resonant frequency of a MEMS resonator having a resonant frequency defined in relation to an operating temperature, wherein the MEMS resonator comprises a first substrate anchor, a beam structure mechanically coupled to the first substrate anchor, a first heating element which is thermally coupled to the first substrate anchor, and an electrical source which is electrically coupled to the first heating element, the method comprising:

passing a heating current through the heating element to conductively heat the first substrate anchor; and

adjusting the heating current in relation to an actual operating temperature for the beam structure.

23. The method of claim 22 further including determining information which is representative of the actual operating temperature using at least one temperature sensor placed in proximity to the beam structure.

24. The method of claim 22 wherein the beam structure comprises a single oscillating beam or a plurality of oscillating beams.

25. The method of claim 22 further including encapsulating the beam structure using a thin film encapsulation technique.

26. The method of claim 22 further including adjusting the heating current to maintain the temperature of the beam structure at the operating temperature or within a predetermined range of temperatures while the MEMS resonator is in operation.

27. The method of claim 22 wherein the MEMS resonator further comprises a second substrate anchor, which is mechanically coupled to the beam structure, and a second heating element which is thermally coupled to the second substrate anchor and electrically coupled to the electrical source, and wherein the method further includes:

passing a heating current through the second heating element to conductively heat the second anchor element; and

adjusting the heating current applied to the second heating element in relation to the actual operating temperature for the beam structure.

28. A method of controlling the resonant frequency of a MEMS resonator having a resonant frequency which is defined in relation to an operating temperature, wherein the MEMS resonator comprises a first substrate anchor, a beam structure mechanically coupled to the first substrate anchor, a first heating element which is disposed in the beam structure and thermally coupled thereto, and an electrical source, which is electrically coupled to the first heating element, the method comprising:

passing a heating current through the first heating element to heat the beam structure; and

adjusting the heating current to maintain the temperature of the beam structure at the operating temperature or within a predetermined range of temperatures while the MEMS resonator is in operation.

29. The method of claim 28 further including determining information which is representative of the actual operating temperature and, in response thereto, to adjust the heating current to maintain the temperature of the beam structure at the operating temperature or within the predetermined range of temperatures while the MEMS resonator is in operation.

30. The method of claim 28 wherein the beam structure comprises a single oscillating beam or plurality of oscillating beams.

31. The method of claim 28 wherein the MEMS resonator further comprises a second heating element, which is thermally coupled to the first substrate anchor, and electrically coupled to the electrical source, the method further comprises:

passing a heating current through the second heating element to conductively heat the first substrate anchor; and

adjusting the heating current to maintain the temperature of the beam structure at the operating temperature or within the predetermined range of temperatures while the MEMS resonator is in operation.

32. The method of claim 28 further including encapsulating the beam structure using a thin film encapsulation technique.

33. A MEMS resonator having a resonant frequency defined in relation to an operating temperature, comprising:

a first substrate anchor;

a beam structure mechanically coupled to the first substrate anchor;

thin film encapsulation structure disposed over the beam structure to enclose the beam structure;

a first heating element which is disposed proximate the beam structure and thermally coupled thereto;

an electrical source, electrically coupled to the first heating element, to provide an electrical current to the first heating element; and

wherein, in response to the electrical current, the first heating element transfers heat to the beam structure to maintain the temperature of the beam structure at the operating temperature or within a predetermined range of temperatures while the MEMS resonator is in operation.

34. The MEMS resonator of claim 33 further including an insulator, disposed between the beam structure and the first heating element.

35. The MEMS resonator of claim 34 wherein the first heating element is juxtaposed the beam structure and separated therefrom by the insulator.

36. The MEMS resonator of claim 33 further including control circuitry, coupled to the electrical source, to generate control information and provide the control information to the electrical source to maintain the beam structure at the operating temperature or within a predetermined range of temperatures while the MEMS resonator is in operation.

37. The MEMS resonator of claim 33 wherein the beam structure comprises a single oscillating beam.

38. The MEMS resonator of claim 33 wherein the beam structure comprises a plurality of moveable beams wherein at least one of the moveable beams is coupled to the first substrate anchor.

39. The MEMS resonator of claim 33 wherein the beam structure includes a composite structure formed from a plurality of materials, wherein at least two of the materials in the plurality of materials have different thermal expansion coefficients.

40. The MEMS resonator of claim 33 further including:

a second heating element which is thermally coupled to the first substrate anchor, wherein the electrical source is electrically coupled to the second heating element to provide an electrical current to the second heating element, and wherein, in response to the electrical current, the second heating element transfers heat to the first substrate anchor to maintain the temperature of the beam structure at the operating temperature or within a predetermined range of temperatures while the MEMS resonator is in operation.

41. A MEMS resonator having a resonant frequency defined in relation to an operating temperature, comprising:

a first electrical contact;

a second electrical contact;

a beam structure electrically coupled to the first and second electrical contacts;

a temperature sensor, placed in proximity to the beam structure, to measure temperature;

an electrical source, coupled to the first and second electrical contacts, to provide an electrical current to the beam structure to heat the beam structure to maintain the temperature of the beam structure at an operating temperature or within a predetermined range of temperatures while the MEMS resonator is in operation; and

control circuitry, coupled to the temperature sensor, to generate control information and provide the control information to the electrical source to maintain the beam structure at the operating temperature or within a predetermined range of temperatures while the MEMS resonator is in operation, and wherein the control circuitry, in response to temperature data measured by the temperature sensor, generates the control information using a mathematical relationship or data contained in a look-up table.

42. The MEMS resonator of claim 41 wherein the electrical source is adapted to provide an electrical current to either the first electrical contact or the second electrical contact and wherein the beam structure includes a conducting or semi-conducting material.

43. The MEMS resonator of claim 41 further including a thin film encapsulation structure to enclose the beam structure.

44. The MEMS resonator of claim 41 wherein the beam structure comprises a single oscillating beam or a plurality of moveable beams.

45. The MEMS resonator of claim 41 wherein the beam structure is fixed to a substrate anchor.

46. The MEMS resonator of claim 45 wherein the substrate anchor includes a composite structure formed from a plurality of materials, wherein at least two of the materials in the plurality of materials have different thermal expansion coefficients.

47. The MEMS resonator of claim 46 wherein the beam structure includes a composite structure formed from a plurality of materials, wherein at least two of the materials in the plurality of materials have different thermal expansion coefficients.

48. The MEMS resonator of claim 45 wherein:

the beam structure includes a composite structure formed from a plurality of materials, wherein at least two of the materials in the plurality of materials have different thermal expansion coefficients; and

the substrate anchor includes a composite structure formed from a plurality of materials, wherein at least two of the materials in the plurality of materials have different thermal expansion coefficients.

49. The MEMS resonator of claim 45 wherein the beam structure includes a composite structure formed from a plurality of materials, wherein at least two of the materials in the plurality of materials have different thermal expansion coefficients.

50. A method of controlling the resonant frequency of a MEMS resonator having a resonant frequency which is defined in relation to an operating temperature, wherein the MEMS resonator comprises (i) a first substrate anchor, (ii) a beam structure mechanically coupled to the first substrate anchor, (iii) a heating element, which is coupled to the first substrate anchor, and (iv) an electrical source, which is electrically coupled to the beam structure and the heating element, the method comprising:

passing a first heating current through the heating element to heat the first substrate anchor,

passing a second heating current through the beam structure to heat the beam structure; and

adjusting the first heating current and/or the second heating current to maintain the temperature of the beam structure at the operating temperature or within a predetermined range of temperatures while the MEMS resonator is in operation.

51. The method of claim 50 further including determining information which is representative of the actual operating temperature and, in response thereto, adjusting the first and/or second heating current to maintain the temperature of the beam structure at the operating temperature or within the predetermined range of temperatures while the MEMS resonator is in operation.

52. The method of claim 50 wherein the beam structure comprises a single oscillating beam or plurality of oscillating beams.

53. The method of claim 50 further including encapsulating the beam structure using a thin film encapsulation technique.