MICROELECTROMECHANICAL DEVICE PROVIDED WITH AN ANTI-STICTION STRUCTURE, AND CORRESPONDING ANTI-STICTION METHOD

• US 20100078740A1
• Filed: 09/30/2009
• Published: 04/01/2010
• Est. Priority Date: 09/30/2008
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: CAZZANIGA, Gabriele, CORONATO, Luca
• Granted Patent: US 8,354,900 B2
• Time in Patent Office: Days
• US Class Current: 257/415
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 2201/0242 Gyroscopes
• CPC Class Codes: B81B 3/0013 Structures dimensioned for mechanical prevention of stiction, e.g. spring with increased stiffness
• CPC Class Codes: B81B 3/0018 Structures acting upon the moving or flexible element for transforming energy into mechanical movement or vice versa, i.e. actuators, sensors, generators

Abstract

An embodiment of a microelectromechanical device having a first structural element, a second structural element, which is mobile with respect to the first structural element, and an elastic supporting structure, which extends between the first and second structural elements to enable a relative movement between the first and second structural elements. The microelectromechanical device moreover possesses an anti-stiction structure, which includes at least one flexible element, which is fixed only with respect to the first structural element and, in a condition of rest, is set at a first distance from the second structural element. The anti-stiction structure is designed to generate a repulsive force between the first and second structural elements in the case of relative movement by an amount greater than the first distance.

Claims

1. A microelectromechanical device comprising:

a first structural element;

a second structural element, movable with respect to said first structural element;

an elastic supporting structure extending between said first and second structural elements and configured to enable a relative movement between said first and second structural elements;

an anti-stiction structure including at least one flexible element fixed to only the first structural element and, in a rest condition thereof, arranged at a first distance from the second structural element, said anti-stiction structure being configured to generate a repulsive force between the first and the second structural elements in the case of a relative movement of an amount greater than said first distance.

2. The microelectromechanical device according to claim 1, wherein the first structural element comprises a mobile mass, and the second structural element comprises a load-bearing structure, or vice versa.

3. The microelectromechanical device according to claim 1, further comprising a stop element, of a substantially rigid type, fixed only to one between said first and second structural elements wherein, in a rest condition of said device, said stop element is arranged at a second distance from another structural element between said first and second structural elements, said second distance being greater than said first distance, and being configured to limit the relative movement between said first and second structural elements.

4. The microelectromechanical device according to claim 3, wherein said stop element is distinct from said flexible element and directly faces an abutment portion of said another structural element between said first and second structural elements.

5. The microelectromechanical device according to claim 2, wherein said load-bearing structure comprises a substrate, said movable mass being suspended above a surface of said substrate and moving in a direction parallel to said surface of said substrate, wherein said flexible element has an elongated shape extending transversely to said direction and is provided with an end forming an abutment surface facing a portion of said first structural element.

6. The microelectromechanical device according to claim 2, wherein said load-bearing structure comprises a substrate, said movable mass being suspended above a surface of said substrate and being mobile in a direction perpendicular to said surface of said substrate or being rotatably movable with respect to said surface, said flexible element having an elongated shape with a, first end fixed to said movable mass and a second end provided with a protruding portion facing and arranged at said first distance from said surface.

7. The microelectromechanical device according to claim 6, wherein said mobile mass has a trench facing a side of the mobile mass and said flexible element extends within said trench.

8. The microelectromechanical device according to claim 6, wherein said protruding portion comprises a bump extending transversely to said surface.

9. The microelectromechanical device according to claim 7, wherein said protruding portion extends as a prolongation of the flexible element, beyond said side of the mobile mass.

10. A method for actuation of a microelectromechanical device comprising:

a first structural element;

a second structural element, movable with respect to said first structural element;

an elastic supporting structure, extending between said first and second structural elements and configured to enable a relative movement between said first and second structural elements; and

at least one flexible element, fixed only to the first structural element;

the method comprising;

arranging the flexible element in a rest condition thereof at a first distance from the second structural element;

generating, through the flexible element, a repulsive force between the first and the second structural elements in case of a relative movement of an amount greater than said first distance.

11. The method according to claim 10, wherein, during said step of generating a repulsive force, said flexible element undergoes elastic bending caused by a contact with said second structural element.

12. The method according to claim 10, wherein the microelectromechanical device further comprises a stop element, of a substantially rigid type, fixed only to one structural element between said first and second structural elements, the method comprising the steps of:

arranging, in the rest condition of said device, said stop element at a second distance from the another structural element between said first and second structural elements, said second distance being greater than said first distance;

limiting the relative movement between said first and second structural elements through the stop element when the first structural element is displaced by an amount equal to said second distance.

13. An apparatus, comprising:

a substrate;

a mass;

a first elastic member having a first end coupled to the substrate and having a second end coupled to the mass; and

a damping assembly disposed between the mass and the substrate.

14. The apparatus of claim 13 wherein the substrate comprises a semiconductor substrate.

15. The apparatus of claim 13 wherein:

the substrate has a surface;

the first end of the first elastic member is coupled to the surface; and

the damping assembly is disposed between the mass and the surface.

16. The apparatus of claim 13 wherein:

the substrate has first and second surfaces;

the first end of the first elastic member is coupled to the first surface; and

the damping assembly is disposed between the mass and the second surface.

17. The apparatus of claim 13 wherein the first elastic member comprises a spring.

18. The apparatus of claim 13 wherein the damping assembly comprises a second elastic member having a first end coupled to the mass and having a second end facing the substrate.

19. The apparatus of claim 18 wherein the second elastic member comprises a spring.

20. The apparatus of claim 13 wherein the damping assembly comprises a second elastic member having a first end coupled to the substrate and having a second end facing the substrate.

21. The apparatus of claim 13 wherein the damping assembly comprises a second elastic member coupled to the mass, extending toward the substrate, and spaced from the substrate.

22. The apparatus of claim 13 wherein the damping assembly comprises a second elastic member coupled to the substrate, extending toward the mass, and spaced from the mass.

23. The apparatus of claim 13, further comprising a mass stop disposed between the mass and the substrate.

24. The apparatus of claim 13, further comprising:

wherein the substrate comprises a surface that faces the mass; and

a mass stop extending from the surface of the substrate and spaced from the mass.

25. The apparatus of claim 13, further comprising:

wherein the mass comprises a surface that faces the substrate; and

a mass stop extending from the surface of the mass and spaced from the substrate.

26. The apparatus of claim 13 wherein:

the mass includes a plate that is operable to rotate about an axis of the first elastic member and that has a surface that faces a portion of the substrate; and

the damping assembly includes a second elastic member that is coupled to the plate and that protrudes beyond the surface.

27. The apparatus of claim 13 wherein:

the mass includes a plate that is operable to rotate about an axis of the first elastic member and that has an edge that is operable to rotate toward the substrate; and

the damping assembly includes a second elastic member that is coupled to the plate and that protrudes beyond the edge.

28. The apparatus of claim 13 wherein the mass includes a plate that is substantially parallel to a portion of the substrate.

29. The apparatus of claim 13 wherein:

the substrate has first and second substantially perpendicular surfaces;

the second end of the first elastic member is coupled to the first surface; and

the damping assembly includes a second elastic member that protrudes from the second surface and is disposed between the mass and the first surface.

30. The apparatus of claim 29 wherein the second elastic member comprises a beam.

31. An integrated circuit, comprising:

a substrate;

a mass;

a first elastic member having a first end coupled to the substrate and having a second end coupled to the mass; and

a damping assembly disposed between the mass and the substrate.

32. A system, comprising:

a first integrated circuit, comprising

a substrate,

a mass,

a first elastic member having a first end coupled to the substrate and having a second end coupled to the mass, and

a damping assembly disposed between the mass and the substrate; and

a second integrated circuit coupled to the first integrated circuit.

33. The system of claim 32 wherein the first and second integrated circuits are disposed on a same die.

34. The system of claim 32 wherein the first and second integrated circuits are disposed on different dies.

35. The system of claim 32 wherein the second integrated circuit comprises a controller.

36. A method, comprising:

applying to a mass in a semiconductor structure a first force that is a first function of a displacement of the mass from a home position while the displacement is within a first range; and

applying to the mass a second force that is a second function of the displacement of the mass while the displacement is beyond the first range.

37. The method of claim 36 wherein the home position comprises a position in which the mass experiences substantially zero net force.

38. The method of claim 36 wherein the second force is greater than the first force.

39. The method of claim 36 wherein:

applying the first force comprises applying the first force in a direction; and

applying the second force comprises applying the second force in substantially the direction.

40. The method of claim 36 wherein:

applying the first force comprises applying the first force with a first elastic member; and

applying the second force comprises applying the second force with the first elastic member and a second elastic member.

41. The method of claim 36, further comprising:

wherein applying the second force comprises applying the second force while the displacement of the mass is within a second range that is beyond the first range; and

applying a stopping force to the mass while the displacement of the mass is beyond the second range.

42. The method of claim 36 wherein:

the first force is a first function of a rotational displacement of the mass from a home position while the rotational displacement is within a first range; and

the second force is a second function of the rotational displacement of the mass while the rotational displacement is beyond the first range.

43. The method of claim 36 wherein:

applying the first force comprises pulling the mass with an extended first elastic member; and

applying the second force comprises pulling the mass with the extended first elastic member and pushing the mass with a compressed second elastic member.

44. The method of claim 36 wherein:

applying the first force comprises pushing the mass with a compressed first elastic member; and

applying the second force comprises pushing the mass with the compressed first elastic member and with a bent second elastic member.

45. The method of claim 36 wherein:

applying the first force comprises applying a torque to the mass with a twisted first elastic member; and

applying the second force comprises applying a torque to the mass with the twisted first elastic member and with a bent second elastic member.

46. The method of claim 36 wherein:

applying the first force comprises pushing the mass with a compressed first elastic member; and

applying the second force comprises pushing the mass with the compressed first elastic member and with a compressed second elastic member.

47. The method of claim 36 wherein:

applying the first force comprises pulling the mass with an extended first elastic member; and

applying the second force comprises pulling the mass with the extended first elastic member and with an extended second elastic member.