Microelectromechanical device provided with an anti-stiction structure, and corresponding anti-stiction method

• US 8,736,405 B2
• Filed: 12/18/2012
• Issued: 05/27/2014
• 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
• Primary Examiner(s): Rojas, Bernard
• Application Number:
  US13/718,964
• Publication Number:
  US 20130106241A1
• Time in Patent Office: 525 Days
• Field of Search: 335/78, 200/181
• US Class Current: 335/78
• 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, the second structural element including a trench facing a side of the second 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

an anti-stiction structure including a flexible element fixed to the second structural element and, in a rest condition thereof, arranged at a first distance from the first structural element, said anti-stiction structure being configured to generate a repulsive force between the first and the second structural elements prior to the first and the second structural elements contacting each other and after a relative movement of an amount greater than said first distance, said flexible element extending within the trench and having an elongated shape with a first end portion fixed to said second structural element and a second end portion provided with a protruding portion facing and arranged at said first distance from said first structural element.

2. The microelectromechanical device according to claim 1, wherein the elastic supporting structure includes a torsional spring coupled to and extending between the first structural element and the second structural element.

3. The microelectromechanical device according to claim 2, wherein said first structural element comprises a substrate, said second structural element is suspended above a surface of said first structural element, and said flexible element has an elongated shape extending transversely to a direction of movement of the second structural element and is provided with an end forming an abutment surface facing a portion of said first structural element.

4. The microelectromechanical device according to claim 2, wherein said first structural element comprises a substrate, said second structural element is suspended above a surface of said substrate and is rotatably movable with respect to said surface.

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

6. The microelectromechanical device according to claim 5, wherein said stop element is distinct from said flexible element and directly faces an abutment portion of said third structural element.

7. The microelectromechanical device according to claim 1, wherein said protruding portion extends as a prolongation of the flexible element, beyond said side of the second structural element.

8. The system of claim 1, wherein:

the first structural element has substantially perpendicular first and second surfaces;

the elastic supporting structure includes a first member coupled between the first surface of the first structural element and the second structural element; and

the elastic supporting structure includes a second member that protrudes from the second surface of the first structural element and couples the first and the second structural elements.

9. An apparatus, comprising:

a substrate;

a mobile mass having a trench facing a side of the mobile mass;

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

an anti-stiction structure including an anti-stiction element coupled to the mass and, in a rest condition thereof, arranged at a first distance from the substrate, said anti-stiction structure being configured to generate a repulsive force between the mass and substrate prior to the mobile mass and the substrate contacting each other and after a relative movement of an amount greater than said first distance, said anti-stiction element having an elongated shape extending in the trench of the mass and having a first end coupled to said movable mass.

10. The apparatus of claim 9 wherein the substrate comprises a semiconductor substrate.

11. The apparatus of claim 9 wherein:

the substrate has first and second surfaces;

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

the anti-stiction element is arranged at the first distance from the second surface in the rest condition and is configured to generate the repulsive force between the mass and second surface in the case of the relative movement of the amount greater than said first distance.

12. The apparatus of claim 9 wherein the first elastic member includes a torsional spring coupled to and extending between the mass and substrate.

13. The apparatus of claim 9 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, further comprising:

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

14. The apparatus of claim 9 wherein:

the substrate has substantially perpendicular first and second surfaces; and

the second end of the first elastic member is coupled to the first surface, the apparatus further comprising;

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

15. A system, comprising:

a first integrated circuit that includes;

a first structural element;

a second structural element movable with respect to said first structural element, the second structural element including a trench facing a side of the second 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

an anti-stiction structure including a flexible element fixed to the second structural element and, in a rest condition thereof, arranged at a first distance from the first structural element, said anti-stiction structure being configured to generate a repulsive force between the first and the second structural elements prior to the first and second structural elements contacting each other and after a relative movement of an amount greater than said first distance, said flexible element extending within the trench and having an elongated shape with a first end portion fixed to said second structural element and a second end portion provided with a protruding portion facing and arranged at said first distance from said first structural element, and

a second integrated circuit coupled to the first integrated circuit.

16. The system of claim 15, wherein the first and second integrated circuits are disposed on a same die.

17. The system of claim 15, wherein the first and second integrated circuits are disposed on different dies.

18. The system of claim 15, wherein the second integrated circuit comprises a controller.

19. The system of claim 15, wherein the first elastic element includes a torsional spring coupled to and extending between the mass and substrate.

20. The microelectromechanical device of claim 15, wherein:

the first structural element has substantially perpendicular first and second surfaces;

the elastic supporting structure includes a first member coupled between the first surface of the first structural element and the second structural element; and

the elastic supporting structure includes a second member that protrudes from the second surface of the first structural element and couples the first and the second structural elements.

21. An apparatus, comprising:

a substrate;

a mobile mass having a trench facing a side of the mobile mass;

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

an anti-stiction structure including an anti-stiction element coupled to the mass and, in a rest condition thereof, arranged at a first distance from the substrate, said anti-stiction structure being configured to generate a repulsive force between the mass and substrate in the case of a relative movement of an amount greater than said first distance, said anti-stiction element having an elongated shape extending in the trench of the mass and having a first end coupled to said movable mass;

wherein;

the substrate has substantially perpendicular first and second surfaces; and

the second end of the first elastic member is coupled to the first surface, the apparatus further comprising;

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

22. The apparatus of claim 21 wherein the first elastic member includes a torsional spring coupled to and extending between the mass and substrate.

23. The apparatus of claim 21 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, further comprising:

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