Microelectromechanical devices including rotating plates and related methods

• US 5,914,801 A
• Filed: 09/27/1996
• Issued: 06/22/1999
• Est. Priority Date: 09/27/1996
• Status: Expired due to Term

• Current Assignee: Royal Bank Capital Partners
• Original Assignee: MCNC, Inc.
• Inventors: Koester, David A., Markus, Karen W., Walters, Mark D., Dhuler, Vijayakumar R.
• Primary Examiner(s): Phan, James
• Application Number:
  US08/719,711
• Time in Patent Office: 998 Days
• Field of Search: 359/198-199, 359/212-214, 359/223-224, 359/900, 359/230, 359/290-293, 310/36, 310/40 R, 310/40 MM
• US Class Current: 359/230
• CPC Class Codes: B81B 2201/042 Micromirrors, not used as optical switches
• CPC Class Codes: B81B 2203/058 Rotation out of a plane parallel to the substrate
• CPC Class Codes: B81B 3/0051 For defining the movement, i.e. structures that guide or limit the movement of an element mechanical arrangements for preventing or damping vibration or shock H01H3/60
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G02B 26/101 with both horizontal and vertical deflecting means, e.g. raster or XY scanners colour television using laser beams scanning a display screen H04N9/3129
• CPC Class Codes: Y10S 359/90 Methods
• CPC Class Codes: Y10T 428/24273 including aperture
• CPC Class Codes: Y10T 428/24322 Composite web or sheet
• CPC Class Codes: Y10T 428/24355 Continuous and nonuniform or irregular surface on layer or component [e.g., roofing, etc.]
• CPC Class Codes: Y10T 428/24479 including variation in thickness

Abstract

An electromechanical device includes a first frame having a first aperture therein, a second frame suspended in the first frame wherein the second frame has a second aperture therein, and a plate suspended in the second aperture. A first pair of beams support the second frame along a first axis relative to the first frame so that the second frame rotates about the first axis. A second pair of beams supports the plate along a second axis relative to the second frame so that the plate rotates about the second axis relative to the frame. The first and second axes preferably intersect at a 90° angle. A first actuator provides mechanical force for rotating the second frame relative to the first frame about the first axis. A second actuator provides mechanical force for rotating the plate relative to the second frame about the second axis. Accordingly, the plate can be independently rotated relative to the first axis and the second axis. Related methods are also disclosed.

Claims

1. An electromechanical device comprising:

a first frame having a first aperture therein;

a second frame suspended in said first aperture, said second frame having a second aperture therein;

a plate suspended in said second aperture;

a first pair of beams which support said second frame along a first axis relative to said first frame so that said second frame rotates about said first axis relative to said first frame and a second pair of beams which support said plate along a second axis relative to said second frame so that said plate rotates about said second axis relative to said second frame wherein said first axis and said second axis intersect, wherein at least one end of at least one of said beams comprises a rotational contact that minimizes torsional forces in said beam;

a first actuator which provides mechanical force for rotating said second frame relative to said first frame about said first axis; and

a second actuator which provides mechanical force for rotating said plate relative to said second frame about said second axis so that said plate can be independently rotated relative to said first axis and said second axis.

2. An electromechanical device according to claim 1 wherein said first and second frames respectively comprise first and second portions of a microelectronic substrate to provide a microelectromechanical actuator.

3. An electromechanical device according to claim 2 wherein said plate comprises a third portion of said microelectronic substrate.

4. An electromechanical device according to claim 2 wherein said microelectronic substrate comprises a silicon substrate and wherein said first and second pairs of beams comprise first and second polysilicon beams.

5. An electromechanical device according to claim 1 wherein each of said beams of said second pair extends from opposite sides of said plate to said second frame and wherein one end of each of said beams of said second pair is fixedly connected to one of said plate and said second frame and another end of each of said beams of said second pair is in rotational contact with the other of said plate and said second frame so that said plate rotates relative to said second frame about an axis defined by said beams of said second pair.

6. An electromechanical device according to claim 1 wherein each of said beams of said second pair is fixedly connected to said plate and wherein each of said beams of said second pair comprises an arched contact surface adjacent said second frame so that each of said beams of said second pair rolls on said second frame.

7. An electromechanical device according to claim 1 further comprising a biasing support which supports said plate relative to said second frame so that said plate and said second frame are coplanar when no mechanical force is provided by said second actuator and so that said plate rotates about said second axis when mechanical force is provided by said second actuator.

8. An electromechanical device according to claim 1 wherein said second actuator comprises an electrode spaced apart from said second frame and an arm extending from said electrode to a portion of said plate off said second axis wherein a potential difference between said electrode and said second frame results in an electrostatic force which is transmitted via said arm to said plate thus rotating said plate relative to said second frame.

9. An electromechanical device according to claim 8 wherein said electrode is fixedly connected to said second frame along a portion thereof spaced from said plate.

10. An electromechanical device according to claim 9 wherein said arm is fixedly connected to said plate so that said plate and said second frame are maintained in a common plane when there is no potential difference between said electrode and said second frame.

11. An electromechanical device according to claim 8 further comprising an insulating layer between said second frame and said electrode to prevent electrical shorts therebetween.

12. An electromechanical device according to claim 8 wherein said second actuator further comprises a second electrode spaced apart from said second frame and a second arm extending from said second electrode to a second portion of said plate opposite said second axis from said first arm wherein a potential difference between said second electrode and said second frame results in an electrostatic force which is transmitted via said second arm to said plate thus rotating said plate in a direction opposite rotation generated by said first actuator.

13. An electromechanical device according to claim 8 wherein said arm extends to a portion of said plate closely spaced from said second axis.

14. An electromechanical device comprising:

a frame having an aperture therein;

a plate suspended in said aperture;

a pair of beams on opposite sides of said plate which define an axis of rotation through said plate about which said plate rotates relative to said frame, wherein each of said beams extends from said plate to said frame and wherein a first end of one of said beams is fixedly connected to one of said plate and said frame and a second end of one of said beams is in rotational contact with the other of said plate and said frame and minimizes torsional forces in said beam so that said plate rotates relative to said frame.

15. An electromechanical device according to claim 14 wherein each of said beams is fixedly connected to said plate.

16. An electromechanical device according to claim 14 wherein each of said beams comprises an arched contact surface on said beam adjacent said frame so that said beam rotates on said frame.

17. An electromechanical device according to claim 14 further comprising a biasing support which supports said plate relative to said frame so that said plate and said frame are generally coplanar when no mechanical force is provided to said plate and so that said plate rotates about said axis when mechanical force is provided to said plate.

18. An electromechanical device according to claim 14 wherein said frame comprises a portion of a microelectronic substrate.

19. An electromechanical device according to claim 18 wherein said plate comprises a second portion of said microelectronic substrate.

20. An electromechanical device according to claim 18 wherein said microelectronic substrate comprises a silicon substrate and wherein each of said beams comprises a polysilicon beam.

21. An electromechanical device according to claim 14 further including an actuator which provides mechanical force to rotate said plate relative to said frame about said axis.

22. An electromechanical device according to claim 21 wherein said actuator comprises an electrostatic actuator.

23. An electromechanical device according to claim 22 wherein said actuator comprises an electrode spaced apart from said frame and an arm extending from said electrode to a portion of said plate off said axis wherein a potential difference between said electrode and said frame results in an electrostatic force which is transmitted via said arm to said plate thus rotating said plate relative to said frame.

24. An electromechanical device according to claim 23 wherein said electrode is fixedly connected to said frame.

25. An electromechanical device according to claim 24 wherein said arm is fixedly connected to said plate so that said plate and said frame are maintained in a generally common plane when there is no potential difference between said electrode and said frame.

26. An electromechanical device according to claim 22 further comprising an insulating layer between said frame and said electrode to prevent electrical shorts therebetween.

27. An electromechanical device according to claim 22 wherein said arm extends to a portion of said plate closely spaced from said axis.

28. An electromechanical device comprising:

a frame having an aperture therein;

a plate suspended in said aperture;

a structure which supports said plate along an axis relative to said frame so that said plate rotates about said axis relative to said frame; and

an electrostatic actuator comprising an electrode spaced apart from said frame and an arm extending from said electrode to a portion of said plate off said axis wherein a potential difference between said electrode and said frame results in an electrostatic force which is transmitted via said arm to said plate thus rotating said plate relative to said frame.

29. An electromechanical device according to claim 28 wherein said electrode is fixedly connected to said frame along a portion thereof spaced from said plate.

30. An electromechanical device according to claim 28 wherein said arm is fixedly connected to said plate so that said plate and said frame are maintained in a common plane when there is no potential difference between said electrode and said frame.

31. An electromechanical device according to claim 28 further comprising an insulating layer between said frame and said electrode to prevent electrical shorts therebetween.

32. An electromechanical device according to claim 28 further comprising a second electrostatic actuator comprising a second electrode spaced apart from said frame and a second arm extending from said second electrode to a second portion of said plate opposite said axis from said first arm wherein a potential difference between said second electrode and said frame results in an electrostatic force which is transmitted via said second arm to said plate thus rotating said plate in a direction opposite rotation generated by said first actuator.

33. An electromechanical device according to claim 28 wherein said arm extends to a portion of said plate closely spaced from said axis.

34. An electromechanical device according to claim 28 wherein said frame comprises a portion of a microelectronic substrate to provide a microelectromechanical actuator.

35. An electromechanical device according to claim 34 wherein said plate comprises a second portion of said microelectronic substrate.

36. An electromechanical device according to claim 34 wherein said microelectronic substrate comprises a silicon substrate and wherein said electrode comprises a polysilicon layer.

37. An electromechanical device according to claim 28 wherein said structure comprises a pair of beams extending from opposite sides of said plate to said frame along said axis and wherein a first end of each of said beams is fixedly connected to one of said plate and said frame and a second end of each of said beams is in rotational contact with the other of said plate and said frame so that said plate rotates relative to said frame about an axis defined by said beams.

38. An electromechanical device according to claim 37 wherein each of said beams is fixedly connected to said plate and wherein each of said beams comprises an arched contact surface adjacent said frame so that said beam rolls on said frame.

39. A method for fabricating an electromechanical device on a substrate, said method comprising the steps of:

defining a plate region on a face of said substrate;

defining a frame region on said face of said substrate, wherein said frame region surrounds said plate region and wherein said plate region and said frame region are separated by a sacrificial substrate region;

forming a structure which supports said plate region and provides rotational connections with minimized torsional forces between said plate region and said frame region, allowing rotation of said plate region along an axis relative to said frame region;

forming an actuator on said face of said substrate which provides mechanical force to said plate region; and

removing said sacrificial substrate region so that said plate region rotates about said axis relative to said frame region responsive to mechanical force provided by said actuator.

40. A method according to claim 39 wherein said steps of defining said plate region and defining said frame region each comprise doping said respective regions, and wherein said step of removing said sacrificial substrate region comprises etching undoped portions of said substrate.

41. A method according to claim 39 wherein said step of forming a structure which supports said plate region comprises the step of forming a pair of beams on opposite sides of said plate region which define an axis of rotation through said plate region, wherein each of said beams extends from said plate region to said frame region and wherein each of said beams is fixedly connected to one of said plate region and said frame region and a second end of each of said beams is in rotational contact with the other of said plate region and said frame region so that said plate rotates relative to said frame.

42. A method according to claim 41 wherein said step of forming said pair of beams comprises the steps of:

forming a sacrificial layer on said substrate;

forming first and second holes in said sacrificial layer exposing portions of said plate region along said axis;

forming said first and second beams on said sacrificial layer wherein each of said beams is fixedly connected to said plate region through a respective one of said holes in said sacrificial layer; and

removing said sacrificial layer.

43. A method according to claim 41 wherein said step of forming said first and second beams is preceded by the step of forming first and second partial holes in said sacrificial layer opposite said frame region without exposing said frame region, wherein said partial holes are formed along said axis, and wherein each of said first and second beams extends from a respective exposed portion of said plate region to a respective partial hole opposite said frame region.

44. A method according to claim 43 wherein said step of forming said partial holes comprises isotropically etching said sacrificial layer.

45. A method according to claim 43 wherein each of said partial holes has an arched surface so that each of said beams extending into said respective partial hole forms an arched contact surface.

46. A method according to claim 43 wherein said step of forming said sacrificial layer comprises the steps of forming a first sacrificial sublayer having a first etch rate on said substrate and forming a second sacrificial sublayer having a second etch rate which is high relative to said first etch rate on said first sacrificial sublayer opposite said substrate, and wherein said step of forming said partial holes comprises etching said second sacrificial sublayer.

47. A method according to claim 39 further comprising the step of forming a biasing support which supports said plate region relative to said frame region so that said plate region and said frame region are coplanar when no mechanical force is provided by said actuator and so that said plate region rotates about said axis when mechanical force is provided by said actuator.

48. A method according to claim 39 wherein said step of forming said actuator comprises forming an electrode spaced apart from said frame region and an arm extending from said electrode to a portion of said plate region off said axis wherein a potential difference between said electrode and said frame region results in an electrostatic force which is transmitted via said arm to said plate region thus rotating said plate region relative to said frame region.

49. A method for fabricating an electromechanical device, said method comprising the steps of:

forming a frame having an aperture therein;

forming a plate suspended in said aperture;

forming a pair of beams on opposite sides of said plate which define an axis of rotation through said plate about which said plate rotates relative to said frame, wherein each of said beams extends from said plate to said frame and wherein a first end of each of said beams is fixedly connected to one of said plate and said frame and a second end of each of said beams is in rotational contact with the other of said plate and said frame so that said plate rotates relative to said frame; and

forming an actuator which provides mechanical force for rotating said plate relative to said frame about said axis.

50. A method according to claim 49 further comprising the step of forming a biasing support which supports said plate relative to said frame so that said plate and said frame are coplanar when no mechanical force is provided by said actuator and so that said plate rotates about said axis when mechanical force is provided by said actuator.

51. A method according to claim 49 wherein said step of forming said frame comprises forming said frame from a microelectronic substrate to provide a microelectromechanical actuator.

52. A method according to claim 51 wherein said plate is formed from said microelectronic substrate.

53. A method according to claim 51 wherein said microelectronic substrate comprises a silicon substrate and wherein each of said beams comprises a polysilicon beam.

54. A method according to claim 49 wherein said step of forming said actuator comprises forming an electrode spaced apart from said frame and an arm extending from said electrode to a portion of said plate off said axis wherein a potential difference between said electrode and said frame results in an electrostatic force which is transmitted via said arm to said plate thus rotating said plate relative to said frame.

55. A method according to claim 54 further comprising the step of forming an insulating layer between said frame and said electrode to prevent electrical shorts therebetween.

56. A method for fabricating a microelectromechanical device, said method comprising the steps of:

forming a frame having an aperture therein;

forming a plate suspended in said aperture;

forming a structure which supports said plate along an axis relative to said frame so that said plate rotates about said axis relative to said frame; and

forming an electrostatic actuator comprising an electrode spaced apart from said frame and an arm extending from said electrode to a portion of said plate off said axis wherein a potential difference between said electrode and said frame results in an electrostatic force which is transmitted via said arm to said plate thus rotating said plate relative to said frame.

57. A method according to claim 56 wherein said arm is fixedly connected to said plate so that said plate and said frame are maintained in a common plane when there is no potential difference between said electrode and said frame.

58. A method according to claim 56 further comprising the step of forming an insulating layer between said frame and said electrode to prevent electrical shorts therebetween.

59. A method according to claim 56 further comprising the step of forming a second electrode spaced apart from said frame and a second arm extending from said second electrode to a second portion of said plate opposite said axis from said first arm wherein a potential difference between said second electrode and said frame results in an electrostatic force which is transmitted via said second arm to said plate thus rotating said plate in a direction opposite rotation generated by said first actuator.

60. A method according to claim 56 wherein said step of forming said frame comprises forming said frame from a microelectronic substrate to provide a microelectromechanical actuator.

61. A method according to claim 60 wherein said plate and said frame are formed from said microelectronic substrate.

62. A method according to claim 60 wherein said microelectronic substrate comprises a silicon substrate and wherein said electrode comprises a polysilicon layer.

63. A method according to claim 56 wherein said step of forming said structure comprises forming a pair of beams extending from opposite sides of said plate to said frame along said axis and wherein a first end of each of said beams is fixedly connected to one of said plate and said frame and a second end of each of said beams is in rotational contact with the other of said plate and said frame so that said plate rotates relative to said frame about an axis defined by said beams.