Electrode design and positioning for controlled movement of a moveable electrode and associated support structure

• US 20030202735A1
• Filed: 04/30/2002
• Published: 10/30/2003
• Est. Priority Date: 04/30/2002
• Status: Active Grant

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Peeters, Eric, Volkel, Armin R., Hantschel, Thomas, Rosa, Michel A., DeBruyker, Dirk, Dunec, John L.
• Granted Patent: US 6,891,240 B2
• Time in Patent Office: Days
• US Class Current: 385/16
• CPC Class Codes: B81B 2201/042 Micromirrors, not used as optical switches
• CPC Class Codes: B81B 2201/045 Optical switches
• CPC Class Codes: B81B 2203/0118 Cantilevers
• CPC Class Codes: B81B 2203/058 Rotation out of a plane parallel to the substrate
• CPC Class Codes: B81B 3/0008 Structures for avoiding electrostatic attraction, e.g. avoiding charge accumulation
• CPC Class Codes: B81B 3/0021 Transducers for transforming electrical into mechanical energy or vice versa dynamo-electric machines H02K99/00; electrostatic machines H02N1/00; piezoelectric devices H10N30/00
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: H02N 1/002 Electrostatic motors

Abstract

A MEMS system including a fixed electrode and a suspended moveable electrode that is controllable over a wide range of motion. In traditional systems where an fixed electrode is positioned under the moveable electrode, the range of motion is limited because the support structure supporting the moveable electrode becomes unstable when the moveable electrode moves too close to the fixed electrode. By repositioning the fixed electrode from being directly underneath the moving electrode, a much wider range of controllable motion is achievable. Wide ranges of controllable motion are particularly important in optical switching applications.

Claims

1. A MicroElectroMechanicalSystem comprising:

a substrate having a substrate surface in a lateral plane;

a moveable electrode, the moveable electrode moving in a trajectory in a motion plane, the motion plane oriented approximately perpendicular to the substrate surface;

at least one fixed electrode to control movement of the moveable electrode, at ninety percent of an electrode surface of said fixed electrode extending beyond a surface covered by said moving electrode when said moving electrode moves in the motion plane to maximize contact with the substrate.

2. The MEMS system of claim 1 wherein the moveable electrode is suspended by at least one cantilever.

3. The MEMS system of claim 2 wherein the moveable electrode is the at least one cantilever.

4. The MEMS structure of claim 3 wherein the moveable electrode is a conductive coating over a less conductive material.

5. The MEMS system of claim 2 wherein the cantilever is a metal cantilever.

6. The MEMS system of claim 2 wherein the cantilever is made from a stressed metal.

7. The MEMS system of claim 6 wherein the cantilever curls away from the surface of the substrate.

8. The MEMS system of claim 2 wherein the cantilever is a single-crystal silicon.

9. The MEMS system of claim 2 wherein the cantilever is a polysilicon cantilever.

10. The MEMS system of claim 2 wherein the cantilever is fixed at a first end, the cantilever to rotate around said first end.

11. The MEMS system of claim 1 wherein the entire fixed electrode remains uncovered by the moving electrode when the moving electrode is pressed against the substrate.

12. The MEMS system of claim 11 wherein when the moving electrode moves in its trajectory such that the moving electrode is in the lateral plane of the substrate surface, the moving electrode and the fixed electrode are still separated by at least one micrometer.

13. The MEMS system of claim 2 wherein the cantilever includes a refractory metal.

14. The MEMS system of claim 13 wherein the cantilever includes molybdenum

15. The MEMS system of claim 13 wherein the cantilever includes Zirconium

16. The MEMS system of claim 13 wherein the cantilever includes Tungsten

17. The MEMS system of claim 2 wherein the cantilever has a length less than 400 micro-meters.

18. The MEMS system of claim 2 wherein the cantilever has a width of less than 100 micro-meters.

19. The apparatus of claim 1 wherein the movement of the moveable electrode in said motion plane involves the flexing of a flexible cantilever.

20. The apparatus of claim 1 wherein the spacing between the movable electrode and the fixed electrode remains controllable for at least two thirds of the mechanically allowed trajectory of the moveable electrode.

21. The apparatus of claim 2 further comprising:

a reflective surface affixed to an end of the cantilever, the reflective surface to deflect light from an optical source.

22. The apparatus of claim 1 wherein the fixed electrode has a triangular shape.

23. The apparatus of claim 1 wherein the moving electrode has a triangular shape.

24. The apparatus of claim 1 wherein the moving electrode includes a nonconducting central region, the fixed electrode positioned underneath said nonconducting central region such that when the fixed electrode moves into the lateral plane of the substrate, the nonconducting central region is positioned over the fixed electrode.

25. The apparatus of claim 24 wherein the nonconducting central region is an opening in the moving electrode.

26. The apparatus of claim 24 wherein the moving electrode is a cantilever.

27. The apparatus of claim 24 wherein the fixed electrode is triangular in shape.

28. The apparatus of claim 1 wherein the moving electrode and fixed electrode are arranged such that the distance between the closest point on the fixed electrode and the closest point on the moving electrode increases with distance from the point at which the support structure supporting the moving electrode is coupled to the substrate

29. A MicroElectroMechanicalSystem comprising:

a substrate having a substrate surface in a lateral plane;

a moveable electrode, the moveable electrode moving in a trajectory in a motion plane; and

a fixed electrode to control movement of the moveable electrode, the fixed electrode positioned laterally adjacent to the moveable electrode.

30. The MEMS system of claim 29 wherein the moveable electrode is mounted on a cantilever.

31. The MEMS system of claim 29 wherein the moveable electrode is a cantilever.

32. A MicroElectroMechanicalSystem comprising:

a substrate having a substrate surface in a lateral plane;

a moveable electrode; and

a fixed electrode to control movement of the moveable electrode, at least half of an electrode surface of said fixed electrode extending beyond a surface covered by said moving electrode when said moveable electrode is translated to the substrate surface, said translation along a line perpendicular to the substrate surface.

33. The MEMS apparatus of claim 32 wherein the moveable electrode does not cover any of the fixed electrode when said moveable electrode is translated to the substrate surface, said translation along a line perpendicular to the substrate surface.

34. A method of moving a moving electrode using electrostatic forces comprising:

applying a voltage such that a voltage difference is formed between a suspended moving electrode and a fixed electrode positioned laterally adjacent to the moving electrode, the applied voltage causing the moving electrode to move toward a point on a substrate underneath the moving electrode, the point adjacent to said fixed electrode.

35. The method of claim 34 wherein each electric field that electrostatically moves the moving electrode is a fringe electric field from the fixed electrode.