Integrated released beam layer structure fabricated in trenches and manufacturing method thereof

• US 20050110110A1
• Filed: 11/25/2003
• Published: 05/26/2005
• Est. Priority Date: 11/25/2003
• Status: Active Grant

• Current Assignee: STMicroelectronics Incorporated (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Incorporated (STMicroelectronics NV)
• Inventors: Blanchard, Richard A., McAlexander, Joseph C.
• Granted Patent: US 7,397,097 B2
• Time in Patent Office: Days
• US Class Current: 257/522
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 2203/0118 Cantilevers
• CPC Class Codes: B81B 2203/033 Trenches
• CPC Class Codes: B81C 1/00626 Processes for achieving a desired geometry not provided for in groups B81C1/00563 - B81C1/00619
• CPC Class Codes: B81C 2201/0109 Sacrificial layers not provided for in B81C2201/0107 - B81C2201/0108
• CPC Class Codes: B81C 2201/014 by depositing an etch stop layer, e.g. silicon nitride, silicon oxide, metal

Abstract

A released beam structure fabricated in trench and manufacturing method thereof are provided herein. One embodiment of a released beam structure according to the present invention comprises a semiconductor substrate, a trench, a first conducting layer, and a beam. The trench extends into the semiconductor substrate and has walls. The first conducting layer is positioned over the walls of the trench at selected locations. The beam is positioned with the trench and is connected at a first portion thereof to the semiconductor substrate and movable at a second portion thereof. The second portion of the beam is spaced from the walls of the trench by a selected distance. Therefore, the second portion of the beam is free to move in a plane that is perpendicular or parallel to the surface of the substrate, and could be deflected to electrically contact with the walls of the trench in response to a predetermined acceleration force or a predetermined temperature variation applied on the beam structure. Other beam structures such as a beam held at both ends, or a beam held in the middle are also possible. Several beam structures at different angles can be fabricated simultaneously and mechanical etching stops are automatically formed to prevent unwanted overstress conditions when manufacturing several beam structures at the same time. Beam structures can also be manufactured in three orthogonal directions, providing information on acceleration in any direction.

Claims

1. A beam structure comprising:

a semiconductor substrate;

a trench extending into the semiconductor substrate, the trench having walls;

a first conducting layer positioned over the walls of the trench at selected locations;

a beam positioned within the trench, the beam being connected at a first portion thereof to the substrate and being movable at a second portion thereof, the second portion being spaced from the walls of the trench by a selected distance; and

a remaining sacrificial layer between the first portion of the beam and the substrate.

2. The beam structure of claim 1, wherein the remaining sacrificial layer is between the first portion of the beam and the first conducting layer.

3. The beam structure of claim 2 wherein the remaining sacrificial layer comprises an oxide layer.

4. The beam structure of claim 1 wherein the beam is a cantilever beam.

5. The beam structure of claim 1, further comprising a first dielectric layer between the trench and the first conducting layer.

6. The beam structure of claim 5 wherein the first dielectric layer comprises a dual layer of a nitride layer formed on an oxide layer.

7. The beam structure of claim 1, further comprising a second dielectric layer on the beam.

8. The beam structure of claim 1 wherein the beam comprises a second conducting layer and a beam material layer.

9. The beam structure of claim 8 wherein the beam material layer comprises a doped polysilicon layer.

10. The beam structure of claim 8 wherein the second conducting layer comprises a metal layer selected from the group of tungsten, titanium, tantalum, and aluminum.

11. The beam structure of claim 1 wherein the first conducting layer comprises a metal layer selected from the group of tungsten, titanium, tantalum, and aluminum.

12. The beam structure of claim 11 wherein the first conducting layer further comprises a doped polysilicon layer.

47. The beam structure of claim 1 further comprising:

a circuit configured to detect electrical contact between the second portion of the beam and the first conducting layer.

13. A semiconductor structure comprising:

a semiconductor substrate;

a first trench extending in a first direction, the first trench having walls;

a second trench extending in a second direction, the second trench having walls;

a first conducting layer positioned over the walls of the first and the second trenches at selected locations;

a first beam positioned within the first trench, the first beam being rigidly connected at a first portion thereof to the substrate and being movable at a second portion thereof, the second portion being spaced from the walls of the first trench by a selected distance; and

a second beam positioned within the second trench, the second beam being rigidly connected at a first portion thereof to the substrate and being movable at a second portion thereof, the second portion being spaced from the walls of the second trench by a selected distance.

14. The semiconductor structure of claim 13 wherein the length of the first beam is different from the length of the second beam.

15. The semiconductor structure of claim 13 wherein the width of the first beam is different from the width of the second beam.

16. The semiconductor structure of claim 13 wherein the width of the first trench is different from the width of the second trench.

17. The semiconductor structure of claim 13 wherein the thickness of the first beam is different from the thickness of the second beam.

18. The semiconductor structure of claim 13 wherein the first direction is parallel to the second direction.

19. The semiconductor structure of claim 13 wherein the first direction is perpendicular to the second direction.

20. The semiconductor structure of claim 13 wherein the first direction and the second direction are in an arrangement so that the first trench and the second trench have a common radius from a common point.

21. The semiconductor structure of claim 20 wherein the first beam is perpendicular to a first line extending from the center of a circle and the second beam is perpendicular to a second line extending from the center of the same circle.

22. The semiconductor structure of claim 20 wherein the first beam is parallel to and on a first line extending from the center of a circle and the second beam is parallel to and on a second line extending from the center of the same circle.

23. The semiconductor structure of claim 13, further comprising a first dielectric layer between the first trench and the first conducting layer, and between the second trench and the first conducting layer.

24. The semiconductor structure of claim 13, further comprising a first remaining sacrificial layer between the first portion of the first beam and the first conducting layer, and between the first portion of the second beam and the first conducting layer.

26. The integrated circuit of claim 23 wherein the sensor further comprises a first dielectric layer between the trench and the first conducting layer.

27. The integrated circuit of claim 23 wherein the sensor further comprises a remaining sacrificial layer between the first portion of the beam and the first conducting layer.

45. The structure of claim 13 further comprising:

a circuit configured to detect an electrical connection between the first beam and the first conducting layer and between the second beam and the first conducting layer.

46. The structure of claim 45 wherein the circuit is formed in the semiconductor substrate.

25. An integrated circuit on a semiconductor substrate comprising:

a sensor including;

a trench extending from a first surface into the substrate, the trench having walls,

a first conducting layer positioned over the walls of the trench at selected locations, and

a beam positioned within the trench, the beam being connected at a first portion thereof to the substrate and being movable at a second portion thereof, the second portion being spaced from the walls by a selected distance; and

a semiconductor circuit on the substrate having a first node coupled to the first conducting layer and a second node coupled to the beam layer, the semiconductor circuit configured to detect electrical contact between the beam and the trench.

28-31. -31. (canceled)

34. A semiconductor structure comprising:

a semiconductor substrate;

a first trench extending in a first direction, the first trench having walls;

a second trench extending in a second direction, perpendicular to the first direction, the second trench having walls;

a first conducting layer positioned over the walls of the first and the second trenches at selected locations;

a first beam positioned within the first trench, the first beam being connected at a first portion thereof to the substrate and being movable at a second portion thereof, the second portion being spaced from the walls of the first trench by a selected distance;

a second beam positioned within the second trench, the second beam being connected at a first portion thereof to the substrate and being movable at a second portion thereof, the second portion being spaced from the walls of the second trench by a selected distance; and

a third beam that is parallel to the surface of the semiconductor substrate having its primary axis of motion perpendicular to the surface of the substrate.

35. The semiconductor structure of claim 34 wherein the length of the first beam is the same as the length of the second beam.

36. The semiconductor structure of claim 34 wherein the width of the first beam is the same as the width of the second beam.

37. The semiconductor structure of claim 34 wherein the width of the first trench is the same as the width of the second trench.

38. The semiconductor structure of claim 34 wherein the thickness of the first beam is the same as the thickness of the second beam.

39. The semiconductor structure of claim 34 wherein the length of the first beam is the different from the length of the third beam.

40. The semiconductor structure of claim 34 wherein the width of the first beam is the different from the width of the third beam.

41. The semiconductor structure of claim 34 wherein the thickness of the first beam is the different from the thickness of the third beam.

42. The semiconductor structure of claim 34 wherein the third beam is built in a third trench.

43. The semiconductor structure of claim 42 wherein the width of the first trench is different from the width of the third trench.

44. The semiconductor structure of claim 42 wherein the depth of the first trench is different from the depth of the third trench.

48. A method, comprising:

deflecting a beam positioned within a trench formed in a semiconductor substrate, a first portion of the beam fixed to the substrate and a second portion movable with respect to the substrate; and

detecting contact between the second portion of the beam and a wall of the trench.

32. The method of claim 48 wherein the deflecting step comprises:

applying an acceleration force to the substrate so as to deflect the beam to contact the wall of the trench.

33. The method of claim 48 wherein the deflecting step comprises:

applying a temperature variation from a first temperature to a second temperature to the substrate so as to deflect the beam to contact the wall of the trench.

49. The method of claim 48 wherein the detecting step comprises detecting an electrical contact between the beam and the wall of the trench.

50. A beam structure comprising:

a semiconductor substrate;

a trench extending in the semiconductor substrate;

a beam positioned within the trench, coupled at a first portion thereof to the substrate and movable at a second portion thereof, with respect to the substrate; and

means for detecting contact between the second portion of the beam and a wall of the trench.

51. The structure of claim 50 wherein the detecting means comprises an electrical circuit having a first input coupled to the beam and a second input coupled to the wall of the trench, the electrical circuit configured to detect electrical continuity between the first and second inputs.

52. The structure of claim 50 wherein the beam is coupled at a third portion to the substrate, and wherein the second portion is between the first and third portions.