Method For Temperature Compensation In MEMS Resonators With Isolated Regions Of Distinct Material

• US 20110084781A1
• Filed: 11/19/2010
• Published: 04/14/2011
• Est. Priority Date: 03/09/2007
• Status: Active Grant

• Current Assignee: Semiconductor Manufacturing International Corporation
• Original Assignee: Silicon Labs Sc, Inc.
• Inventors: Bernstein, David H., Quevy, Emmanuel P.
• Granted Patent: US 8,669,831 B2
• Time in Patent Office: Days
• US Class Current: 333/200
• CPC Class Codes: B81C 1/00349 Creating layers of material on a substrate
• CPC Class Codes: B81C 1/00523 Etching material
• CPC Class Codes: B81C 1/0069 Thermal properties, e.g. improve thermal insulation
• CPC Class Codes: G02B 6/358 Latching of the moving element, i.e. maintaining or holding the moving element in place once operation has been performed; includes a mechanically bistable system
• CPC Class Codes: H03H 2009/02496 Horizontal, i.e. parallel to the substrate plane
• CPC Class Codes: H03H 2009/2442 Square resonators
• CPC Class Codes: H03H 3/0076 for obtaining desired frequency or temperature coefficients
• CPC Class Codes: H03H 9/2405 of microelectro-mechanical resonators
• CPC Class Codes: H03H 9/2457 Clamped-free beam resonators
• CPC Class Codes: Y10T 29/42 Piezoelectric device making
• CPC Class Codes: Y10T 29/49005 Acoustic transducer
• CPC Class Codes: Y10T 29/49165 by forming conductive walled aperture in base

Abstract

MEMS resonators containing a first material and a second material to tailor the resonator'"'"'s temperature coefficient of frequency (TCF). The first material has a different Young'"'"'s modulus temperature coefficient than the second material. In one embodiment, the first material has a negative Young'"'"'s modulus temperature coefficient and the second material has a positive Young'"'"'s modulus temperature coefficient. In one such embodiment, the first material is a semiconductor and the second material is a dielectric. In a further embodiment, the quantity and location of the second material in the resonator is tailored to meet the resonator TCF specifications for a particular application. In an embodiment, the second material is isolated to a region of the resonator proximate to a point of maximum stress within the resonator. In a particular embodiment, the resonator includes a first material with a trench containing the second material.

Claims

1. A microelectromechanical system (MEMS) resonator device, comprising:

at least one resonating member that includes a first material having one or more trenches defined therein, each of the trenches being at least partially filled with a second material that acts to modify the thermal coefficient of frequency (TCF) of the resonator device; and

wherein the second material has a Young'"'"'s modulus temperature coefficient that is different from the Young'"'"'s modulus temperature coefficient of the first material.

2. The device of claim 1, wherein the first material has a negative Young'"'"'s modulus temperature coefficient;

wherein the second material has a positive Young'"'"'s modulus temperature coefficient; and

wherein each of the trenches is at least partially filled with a second material that acts to lower the thermal coefficient of frequency (TCF) of the resonator device.

3. The device of claim 1, wherein the one or more trenches are located in one or more regions of the resonating member that include a point of maximum stress within the resonating member during operation of the resonator device.

4. The device of claim 3, wherein the one or more regions are located on opposite sidewalls of the resonating member.

5. The device of claim 1, wherein the one or more trenches are located in one or more regions of the resonating member that include a point of minimum displacement within the resonating member during operation of the resonator device.

6. The device of claim 1, wherein each of the one or more trenches is defined to extend entirely through the first material such that the second material filling each trench extends between opposing surfaces of the first material.

7. The device of claim 1, wherein each of the one or more trenches is defined to extend from a surface of the first material through only a portion of the first material to form a well having a bottom floor that comprises the first material.

8. The device of claim 1, wherein the one or more trenches comprise a plurality of spaced trenches defined in the first material.

9. The device of claim 1, wherein the one or more trenches comprise a plurality of trenches located in a plurality of spaced regions of the resonating member.

10. The device of claim 1, wherein each of the one or more trenches is defined with a dimension required to compensate the TCF of the resonator device.

11. The device of claim 1, wherein the resonating member comprises an elongated beam having a length;

and wherein each of the one or more trenches is defined in the first material as an elongated trench having a length oriented parallel to the length of the elongated beam.

12. The device of claim 1, wherein at least a portion of the at least one resonating member resonates via a flexural mode.

13. The device of claim 12, wherein the resonating member comprises at least one cantilevered beam that is anchored at a first end;

and wherein the one or more trenches are located in one or more regions of the resonating member proximate to the anchored first end.

14. The device of claim 13, wherein the resonating member comprises at least one cantilevered beam that is anchored at a first end;

and wherein the one or more trenches are located in regions of the resonating member on opposite sidewalls of the resonating member and proximate to the anchored first end.

15. The device of claim 14, wherein the resonating member comprises a tuning fork.

16. The device of claim 1, wherein the resonating member comprises one of a beam anchored at two ends, a plate resonator, a ring resonator, or a disk resonator.

17. The device of claim 1, wherein the resonating member comprises a beam anchored at two ends.

18. The device of claim 1, wherein the resonating member comprises a plate resonator, disk resonator or ring resonator;

and wherein the one or more trenches are arranged as a radial array defined in the resonating member.

19. The device of claim 1, wherein at least some of the sides of the at least one resonating member extend to cause resonation.

20. The device of claim 1, wherein each of the one or more trenches is completely filled with the second material.

21. The device of claim 1, wherein each of the one or more trenches is only partially filled with the second material.

22. The device of claim 21, wherein the second material partially fills each of the one or more trenches to form an annular spacer structure of the second material along the inner edge of each trench.

23. The device of claim 1, further comprising at least one layer above or below the first material that encapsulates the second material.

24. The device of claim 1, wherein the second material comprises silicon dioxide.

25. The device of claim 24, wherein the first material comprises at least one of silicon, germanium, or a silicon/germanium alloy.

26. A method for forming a microelectromechanical system (MEMS) resonator device, the method comprising:

providing a resonating member comprised of a first material;

forming one or more trenches within the first material of the resonating member; and

at least partially filling the one or more trenches with a second material that acts to modify the thermal coefficient of frequency (TCF) of the resonator device;

wherein the second material has a Young'"'"'s modulus temperature coefficient that is different from the Young'"'"'s modulus temperature coefficient of the first material.

27. The method of claim 26, wherein the first material has a negative Young'"'"'s modulus temperature coefficient;

wherein the second material has a positive Young'"'"'s modulus temperature coefficient; and

wherein the method further comprises at least partially filling each of the trenches with the second material to lower the thermal coefficient of frequency (TCF) of the resonator device.

28. The method of claim 26, further comprising forming each of the one or more trenches to extend entirely through the first material;

and filling each of the one or more trenches with a second material that extends between opposing surfaces of the first material.

29. The method of claim 26, further comprising forming each of the one or more trenches to extend from a surface of the first material through only a portion of the first material to form a well having a bottom floor that comprises the first material.

30. The method of claim 26, wherein the resonating member comprises at least one beam;

wherein the method comprises anchoring a first end of the resonating member to provide a cantilevered beam; and

wherein the method further comprises forming the one or more trenches in one or more regions of the resonating member located proximate to the anchored first end.

31. The method of claim 30, wherein the resonating member comprises at least one beam;

wherein the method comprises anchoring a first end of the resonating member to provide a cantilevered beam; and

wherein the method further comprises forming the one or more trenches in one or more regions of the resonating member located on opposite sidewalls of the resonating member and proximate to the anchored first end.

32. The method of claim 31, wherein the resonating member comprises a tuning fork.

33. The device of claim 26, wherein the resonating member comprises a beam anchored at two ends.

34. The method of claim 26, wherein the resonating member comprises a plate resonator, disk resonator or ring resonator;

and wherein the method further comprises forming the one or more trenches within the resonating member as a radial array defined in the resonating member.

35. The method of claim 26, further comprising completely filling each of the one or more trenches with the second material.

36. The method of claim 26, further comprising only partially filling each of the one or more trenches with the second material.

37. The method of claim 36, further comprising partially filling each of the one or more trenches with the second material to form an annular spacer structure of the second material along the inner edge of each trench.

38. The method of claim 26, further forming at least one layer above or below the first material to encapsulate the second material.

39. The method of claim 26, wherein the second material comprises silicon dioxide.

40. The method of claim 39, wherein the first material comprises at least one of silicon, germanium, or a silicon/germanium alloy.

41. The method of claim 39, wherein the first material comprises silicon;

and wherein the step of at least partially filling the one or more trenches with the second material comprises at least one of depositing the silicon dioxide within each trench, oxidizing the first material to form the silicon dioxide within each trench, or a combination thereof.

42. The method of claim 26, wherein an artifact of second material is formed during the step of at least partially filling the one or more trenches with the second material;

and wherein the method further comprises removing the artifact of second material after the step of at least partially filling the one or more trenches with the second material.

43. The method of claim 26, further comprising lithographically defining the one or more trenches in the first material.