Microelectromechanical apparatus for elevating and tilting a platform

• US 20010048265A1
• Filed: 04/05/2001
• Published: 12/06/2001
• Est. Priority Date: 04/11/2000
• Status: Active Grant

• Current Assignee: National Technology & Engineering Solutions Of Sandia LLC (Honeywell International Inc.)
• Original Assignee: Sandia National Laboratories (Government of the United States of America)
• Inventors: Sniegowski, Jeffry J., Barnes, Stephen M., Rodgers, Murray Steven, Miller, Samuel Lee, McWhorter, Paul Jackson
• Granted Patent: US 6,545,385 B2
• Time in Patent Office: Days
• US Class Current: 310/309
• CPC Class Codes: B81B 2201/038 Microengines and actuators not provided for in B81B2201/031 - B81B2201/037
• CPC Class Codes: B81B 2201/045 Optical switches
• CPC Class Codes: B81B 2203/0136 Comb structures
• CPC Class Codes: B81B 2203/0307 Anchors
• CPC Class Codes: B81B 2203/053 Translation according to an axis perpendicular to the substrate
• CPC Class Codes: B81B 2203/058 Rotation out of a plane parallel to the substrate
• CPC Class Codes: B81B 3/004 Angular deflection
• CPC Class Codes: B81B 3/0062 Devices moving in two or more dimensions, i.e. having special features which allow movement in more than one dimension
• CPC Class Codes: G02B 2006/12104 Mirror; Reflectors or the like
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G02B 6/122 Basic optical elements, e.g. light-guiding paths
• CPC Class Codes: G02B 6/3518 the reflective optical element being an intrinsic part of a MEMS device, i.e. fabricated together with the MEMS device MEMS devices in general B81B; manufacture of MEM devices in general B81C; micromechanical devices controlling the direction of light G02B26/0833
• CPC Class Codes: G02B 6/357 Electrostatic force electrostatic forces controlling reflecting elements in general G02B26/0841
• 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: G02B 6/3584 constructional details of an associated actuator having a MEMS construction, i.e. constructed using semiconductor technology such as etching MEMS per se B81B, B81C
• CPC Class Codes: G11B 7/0927 for focusing only G11B7/0937 takes precedence
• CPC Class Codes: H02N 1/006 of the gap-closing type H02N1/004 takes precedence
• CPC Class Codes: H02N 1/008 Laterally driven motors, e.g. of the comb-drive type

Abstract

A microelectromechanical (MEM) apparatus is disclosed which has a platform that can be elevated above a substrate and tilted at an arbitrary angle using a plurality of flexible members which support the platform and control its movement. Each flexible member is further controlled by one or more MEM actuators which act to bend the flexible member. The MEM actuators can be electrostatic comb actuators or vertical zip actuators, or a combination thereof. The MEM apparatus can include a mirror coating to form a programmable mirror for redirecting or switching one or more light beams for use in a projection display. The MEM apparatus with the mirror coating also has applications for switching light beams between optical fibers for use in a local area fiber optic network, or for use in fiber optic telecommunications or data communications systems.

Claims

1. A microelectromechanical apparatus, comprising:

(a) a substrate;

(b) a platform supported above the substrate by a trio of flexible members; and

(c) means for bending each flexible member, thereby changing the elevation or tilt of the platform.

2. The apparatus of

claim 1

wherein the substrate comprises silicon.

3. The apparatus of

claim 1

wherein the platform comprises monocrystalline or polycrystalline silicon.

4. The apparatus of

claim 1

wherein each flexible member is equidistantly spaced about the platform.

5. The apparatus of

claim 1

wherein one end of each flexible member is anchored to the substrate.

6. The apparatus of

claim 1

further including a compliant member for connecting each flexible member to the platform.

7. The apparatus of

claim 6

wherein each compliant member is connected at one end thereof near a midpoint of one of the flexible members, and is connected at the other end thereof to an outer edge of the platform.

8. The apparatus of

claim 6

wherein each compliant member is connected at one end thereof proximate to an end of one of the flexible members, with the other end of each compliant member being connected to the platform at a point equidistant from a central axis of the platform.

9. The apparatus of

claim 1

wherein the platform is circular or polygonal.

10. The apparatus of

claim 1

wherein the platform is planar.

11. The apparatus of

claim 1

wherein the platform has a curved surface.

12. The apparatus of

claim 1

wherein a surface of the platform includes a mirror coating.

13. The apparatus of

claim 12

wherein the other surface of the platform includes a stress-compensation coating formed thereon.

14. The apparatus of

claim 1

wherein the means for bending each flexible member comprises a microelectromechanical actuator operatively connected to the flexible member.

15. The apparatus of

claim 14

wherein the microelectromechanical actuator comprises an electrostatic actuator.

16. The apparatus of

claim 15

wherein the electrostatic actuator comprises an electrostatic comb actuator further comprising a plurality of stationary electrostatic combs attached to the substrate and a plurality of moveable electrostatic combs attached to a frame supported above the substrate, with the moveable electrostatic combs being moveable towards the stationary electrostatic combs in response to an actuation voltage provided therebetween.

17. The apparatus of

claim 15

wherein each electrostatic actuator comprises a vertical zip actuator which further comprises at least one first electrode supported on the substrate and a second electrode superposed above the first electrode with a spacing between the first and second electrodes being variable along the length of the superposed first and second electrodes, and with the second electrode being moveable towards the first electrode in response to an actuation voltage provided therebetween.

18. The apparatus of

claim 17

wherein one end of the second electrode is connected to the flexible member, and the other end of the second electrode is anchored to the substrate.

19. The apparatus of

claim 6

wherein an end of each flexible member connected to the compliant member is further connected to a pair of elongate elevation members juxtaposed on both sides of the flexible member, with the elevation members being anchored to the substrate.

20. The apparatus of

claim 19

wherein the pair of elevation members are anchored to the substrate by a flexible joint.

21. The apparatus of

claim 1

further comprising a plurality of pre-stressed members underlying the platform, with each pre-stressed member being anchored at one end thereof to the substrate, and with the other end of each pre-stressed member providing a force on the platform to urge the platform upward from the substrate.

22. The apparatus of

claim 21

wherein each pre-stressed member comprises an oxide material encased within a polysilicon body for producing a stress gradient in the prestressed member.

23. The apparatus of

claim 1

further comprising a plurality of restraining clips for holding the platform in place during fabrication thereof, with the restraining clips being moveable away from the platform to release the platform for movement thereof.

24. The apparatus of

claim 1

further comprising a plurality of fuses anchoring the platform to the substrate during fabrication thereof, with each fuse being electrically severable to release the platform for movement.

25. The apparatus of

claim 24

wherein each fuse comprises polycrystalline silicon.

26. A microelectromechanical apparatus, comprising:

(a) a substrate;

(b) a platform supported above the substrate by a plurality of flexible members, with each flexible member being connected to the platform at a point between a central axis of the platform and the periphery of the platform; and

(c) a plurality of electrostatic actuators providing movement in a direction substantially in the plane of the substrate, with each electrostatic actuator being operatively connected to one of the flexible members to bend the flexible member out of the plane of the substrate, thereby elevating or tilting the platform.

27. The apparatus of

claim 26

further including a mirror coating on the platform for reflecting an incident light beam.

28. A microelectromechanical apparatus, comprising:

(a) a substrate;

(b) a platform formed on the substrate and having a central axis oriented at an angle to the plane of the substrate;

(c) a plurality of compliant members, each connected at a first end thereof to an underside of the platform, with the plurality of compliant members further being arranged symmetrically about the central axis;

(d) a plurality of elongate flexible members, each connected at an inner end thereof to a second end of one of the compliant members, with an outer end of each elongate flexible member being operatively connected to an electrostatic actuator; and

(e) at least one elongate elevation member connecting each flexible member to the substrate, with each elevation member acting in combination with the flexible member to which the elevation member is connected to elevate or tilt the platform in response to a force provided on the outer end of the flexible member by the electrostatic actuator.

29. The apparatus of

claim 28

wherein the substrate comprises silicon.

30. The apparatus of

claim 28

wherein the platform is circular or polygonal.

31. The apparatus of

claim 28

wherein the platform includes a stress compensation coating formed thereon.

32. The apparatus of

claim 28

wherein the platform includes a mirror coating on a surface thereof.

33. The apparatus of

claim 32

wherein the other surface of the platform includes a stress-compensation coating formed thereon.

34. The apparatus of

claim 28

wherein the plurality of flexible members comprises a trio of flexible members.

35. The apparatus of

claim 28

further including a plurality of pre-stressed members located beneath the platform, with each pre-stressed member being anchored at one end thereof to the substrate, and with the other end of each pre-stressed member providing an upward-directed force on the underside of the platform to urge the platform upward from the substrate.

36. The apparatus of

claim 35

wherein each pre-stressed member is elongate and is oriented radially outward along a line from the central axis.

37. The apparatus of

claim 28

further including a plurality of polysilicon fuses for securing the platform to the substrate, with each fuse being electrically severable to release the platform for movement.

38. The apparatus of

claim 28

further including a plurality of restraining clips for securing the platform to the substrate, with each restraining clip being removable to release the platform for movement.

39. A microelectromechanical apparatus, comprising:

(a) a substrate;

(b) a platform supported above the substrate by a plurality of elongate flexible members;

(c) at least one elevation member connected at one end thereof to each flexible member, with the other end of the elevation member being anchored to the substrate through a flexible joint; and

(d) an electrostatic actuator operatively connected to the other end of each flexible member to provide a force to the flexible member, thereby bending the flexible member and elevatating or tilting the platform.

40. The apparatus of

claim 39

wherein the flexible members are spaced by an angle of 120 degrees about a central axis of the platform.

41. The apparatus of

claim 39

wherein each flexible member supports the platform by a compliant member which connects the flexible member to the platform.

42. The apparatus of

claim 39

wherein the plurality of elongate flexible members comprises two or three flexible members.

43. The apparatus of

claim 39

wherein one side of the platform is anchored to the substrate by a flexible hinge.

44. The apparatus of

claim 39

wherein the platform includes a mirror coating on a topside thereof.

45. An apparatus for redirecting an incident light beam, comprising:

(a) a mirror supported above a substrate for reflecting the incident light; and

(b) a trio of electrostatic actuators spaced about a central axis of the mirror and operatively connected to tilt the mirror in response to an actuation voltage provided to at least one of the trio of electrostatic actuators, thereby redirecting the incident light beam.

46. The apparatus of

claim 45

wherein the substrate comprises silicon.

47. The apparatus of

claim 46

wherein the mirror comprises polycrystalline silicon.

48. The apparatus of

claim 45

wherein the mirror comprises a platform with a lightreflective coating thereon.

49. The apparatus of

claim 45

wherein the mirror is planar.

50. The apparatus of

claim 45

wherein the mirror is curved.

51. The apparatus of

claim 45

wherein each electrostatic actuator is operatively connected to the mirror through a flexible member which is bendable out of the plane of the substrate to support the mirror above the substrate.

52. The apparatus of

claim 51

wherein the flexible member is attached to the mirror by a compliant member.

53. The apparatus of

claim 51

wherein the flexible member is connected to the mirror at the periphery of the mirror.

54. The apparatus of

claim 51

wherein the flexible member is connected to the mirror at a point which is between the periphery and the central axis of the mirror.

55. The apparatus of

claim 51

further including a displacement multiplier disposed between the electrostatic actuator and the flexible member.