MEMS structure having a stress-inducer temperature-compensated resonator member

• US 7,944,124 B1
• Filed: 08/29/2008
• Issued: 05/17/2011
• Est. Priority Date: 08/29/2008
• Status: Active Grant

• Current Assignee: Semiconductor Manufacturing International Corporation
• Original Assignee: Silicon Laboratories Incorporated
• Inventors: Bernstein, David H.
• Primary Examiner(s): Benson; Walter
• Assistant Examiner(s): Gordon; Bryan P
• Application Number:
  US12/201,819
• Time in Patent Office: 991 Days
• Field of Search: 310/370, 310/346, 310/351, 310/328, 310/367
• US Class Current: 310/346
• CPC Class Codes: H03H 2009/02496 Horizontal, i.e. parallel to the substrate plane
• CPC Class Codes: H03H 3/0076 for obtaining desired frequency or temperature coefficients
• CPC Class Codes: H03H 9/02338 Suspension means
• CPC Class Codes: H03H 9/2473 Double-Ended Tuning Fork [DETF] resonators

Abstract

A MEMS structure having a stress-inducer temperature-compensated resonator member is described. The MEMS structure includes a frame disposed above a substrate. The frame has an inner surface and an outer surface and is composed of a first material having a first coefficient of thermal expansion (CTE) and a second material having a second CTE, different from the first CTE. A resonator member is coupled to the inner surface of the frame.

Claims

1. A MEMS structure, comprising:

a frame having a shape and being disposed above a substrate, wherein said frame has an inner surface and an outer surface and comprises one or more regions of first material having a first coefficient of thermal expansion (CTE) and one or more regions of second material having a second CTE, different from said first CTE; and

a resonator member coupled to said inner surface of said frame;

where the regions of first material having the first CTE respond differently to a change in temperature than the regions of second material having the second CTE to cause the shape of the frame to deform, the deformation in shape of the frame resulting from the difference in CTE of the first material and the CTE of the second material and resulting in stress induced on the resonator member in response to the temperature change.

8. The MEMS structure of claim 1, wherein said frame has a shape selected from the group consisting of a ring shape, a square shape, an oval shape, and a rectangle shape.

15. The MEMS structure of claim 1, wherein said second material is exposed at said inner surface or said outer surface, or both, of said frame.

18. The MEMS structure of claim 1, wherein the frame comprises a stress inducer member;

and wherein said resonator member is, in one plane, completely surrounded by said stress inducer member.

19. The MEMS structure of claim 18, wherein said stress inducer member comprises a first material having a first coefficient of thermal expansion (CTE) and a second material having a second CTE, less than said first CTE, and wherein said resonator member comprises said first material.

20. The MEMS structure of claim 19, wherein said second material is contained within a plurality of trenches disposed in said first material of said stress inducer member.

21. The MEMS structure of claim 20, wherein said resonator member is coupled to and inner surface of said stress inducer member at a first point and a second point, forming an axis, and wherein said plurality of trenches is positioned approximately parallel with said axis.

22. The MEMS structure of claim 21, wherein said plurality of trenches is, in the same plane as said resonator member, proximate to said inner surface of said stress inducer member and distant from an outer surface of said stress inducer member.

23. The MEMS structure of claim 20, wherein said resonator member is coupled to an inner surface of said stress inducer member at a first point and a second point, forming an axis, and wherein said plurality of trenches is positioned approximately perpendicular to said axis.

24. The MEMS structure of claim 23, wherein said plurality of trenches is, in the same plane as said resonator member, distant from said inner surface of said stress inducer member and proximate to an outer surface of said stress inducer member.

25. The MEMS structure of claim 19, wherein said first material is a semiconductor and said second material is a dielectric.

26. The MEMS structure of claim 25, wherein said semiconductor comprises at least one of silicon and germanium and said dielectric comprises silicon dioxide.

27. The MEMS structure of claim 20, wherein at least one of said plurality of trenches is exposed at a surface of said stress inducer member, in the same plane as said resonator member.

28. The MEMS structure of claim 20, wherein none of said plurality of trenches is exposed at a surface of said stress inducer member, in the same plane as said resonator member.

29. The MEMS structure of claim 18, further comprising:

one or more anchors, each anchor coupled to said stress inducer member and to said substrate, wherein said resonator member is suspended above said substrate.

30. The MEMS structure of claim 18, further comprising:

one or more decoupling springs coupled to said stress inducer member and anchored to said substrate, wherein said resonator member is suspended above said substrate.

31. The MEMS structure of claim 18, further comprising:

an anchor coupled to said resonator member and to said substrate, wherein said resonator member has a mid-point and said anchor is located approximately at said mid-point, and wherein said stress inducer member is suspended above said substrate.

37. The MEMS structure of claim 1, where the regions of first material having the first CTE expand less in response to an increase in temperature than do the regions of second material having the second CTE to cause the shape of the frame to deform, the deformation in shape of the frame resulting in stress induced on the resonator member in response to the temperature increase.

2. A MEMS structure, comprising:

a frame disposed above a substrate, wherein said frame has an inner surface and an outer surface and comprises a first material having a first coefficient of thermal expansion (CTE) and a second material having a second CTE, different from said first CTE; and

a resonator member coupled to said inner surface of said frame;

wherein said second material is contained within a plurality of trenches disposed in said first material of said frame.

3. The MEMS structure of claim 2, wherein said resonator member is coupled to said frame at a first point and a second point, forming an axis, and wherein said plurality of trenches is positioned approximately parallel with said axis.

4. The MEMS structure of claim 3, wherein said plurality of trenches is proximate to said inner surface of said frame and distant from said outer surface of said frame.

5. The MEMS structure of claim 2, wherein said resonator member is coupled to said frame at a first point and a second point, forming an axis, and wherein said plurality of trenches is positioned approximately perpendicular to said axis.

6. The MEMS structure of claim 5, wherein said plurality of trenches is distant from said inner surface of said frame and proximate to said outer surface of said frame.

7. The MEMS structure of claim 6, wherein said second material is contained within a second plurality of trenches disposed in said first material of said frame, wherein said second plurality of trenches is positioned approximately parallel with said axis, and wherein said second plurality of trenches is proximate to said inner surface of said frame and distant from said outer surface of said frame.

9. The MEMS structure of claim 2, wherein said second CTE is less than said first CTE.

10. The MEMS structure of claim 9, wherein said first material is a semiconductor and said second material is a dielectric.

11. The MEMS structure of claim 10, wherein said semiconductor comprises at least one of silicon and germanium and said dielectric comprises silicon dioxide.

17. The MEMS structure of claim 3, wherein said plurality of trenches is distant from said inner surface of said frame and proximate to said outer surface of said frame.

12. A MEMS structure, comprising:

a frame disposed above a substrate, wherein said frame has an inner surface and an outer surface and comprises a first material having a first coefficient of thermal expansion (CTE) and a second material having a second CTE, different from said first CTE;

a resonator member coupled to said inner surface of said frame; and

one or more anchors, each anchor coupled to said frame and to said substrate, wherein said resonator member is suspended above said substrate.

13. A MEMS structure, comprising:

a frame disposed above a substrate, wherein said frame has an inner surface and an outer surface and comprises a first material having a first coefficient of thermal expansion (CTE) and a second material having a second CTE, different from said first CTE;

a resonator member coupled to said inner surface of said frame; and

one or more decoupling springs coupled to said frame and anchored to said substrate, wherein said resonator member is suspended above said substrate.

14. A MEMS structure, comprising:

a frame disposed above a substrate, wherein said frame has an inner surface and an outer surface and comprises a first material having a first coefficient of thermal expansion (CTE) and a second material having a second CTE, different from said first CTE;

a resonator member coupled to said inner surface of said frame; and

an anchor coupled to said resonator member and to said substrate, wherein said resonator member has a mid-point and said anchor is located approximately at said mid-point, and wherein said frame is suspended above said substrate.

16. A MEMS structure, comprising:

a frame disposed above a substrate, wherein said frame has an inner surface and an outer surface and comprises a first material having a first coefficient of thermal expansion CTE and a second material having a second CTE different from said first CTE; and

a resonator member coupled to said inner surface of said frame;

wherein said second material is not exposed at said inner surface of said frame and is not exposed at said outer surface of said frame.

32. A method for altering the thermal coefficient of frequency of a MEMS structure, comprising:

providing a resonator member housed in a stress inducer member disposed above a substrate, wherein said stress inducer member has a shape and comprises one or more regions of first material having a first coefficient of thermal expansion (CTE) and one or more regions of second material having a second CTE, different from said first CTE, and wherein said resonator member comprises said first material; and

inducing a stress on said resonator member with said stress inducer member in response to a change in temperature by deforming the shape of the stress inducer, where the regions of first material having the first CTE respond differently to the change in temperature than the regions of second material having the second CTE to cause the shape of the stress inducer member to deform, the deformation in shape of the stress inducer member resulting from the difference in CTE of the first material and the CTE of the second material and resulting in the stress induced on the resonator member in response to the temperature change.

33. The method of claim 32, wherein inducing said stress comprises inducing a tensile stress on said resonator member in response to an increase in temperature.

34. The method of claim 32, wherein inducing said stress comprises inducing a compressive stress on said resonator member in response to a decrease in temperature.

35. The method of claim 32, wherein inducing said stress comprises inducing a compressive stress on said resonator member in response to an increase in temperature.

36. The method of claim 32, wherein inducing said stress comprises inducing a tensile stress on said resonator member in response to a decrease in temperature.