Method and a device for reducing hysteresis or imprinting in a movable micro-element

• US 6,885,493 B2
• Filed: 01/28/2002
• Issued: 04/26/2005
• Est. Priority Date: 02/05/2001
• Status: Expired due to Term

• Current Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V., Micronic Laser Systems AB (Mycronic AB)
• Original Assignee: Micronic Laser Systems AB (Mycronic AB)
• Inventors: Lakner, Hubert Karl, Ljungblad, Ulric, Dürr, Peter
• Primary Examiner(s): Dang, Hung Xuan
• Assistant Examiner(s): TRA, TUYEN Q
• Application Number:
  US10/467,184
• Publication Number:
  US 20040150868A1
• Time in Patent Office: 1,184 Days
• Field of Search: 359/290, 359/291, 359/292, 359/295, 359/298, 438/469
• US Class Current: 359/290
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means

Abstract

The present invention relates to a movable micro-element with reduced imprinting or hysteresis effect arranged spaced apart from a surface comprising at least one electrode. At least one restoring element is connected to said movable micro-element. An address electrode is arranged on said surface and capable to electrostatically attract said movable micro-element. Said address electrode is addressed to a first potential. Said movable micro-element is first set to a second potential defining a non addressed state and at a time period Δt before a predetermined pulsed signal is emitted said movable micro-element is switched from said second potential to a third potential defining an addressed state. Said movable micro-element is kept in said addressed state for a time period of Δt+Δt′. The invention also relates to a Spatial Light Modulator (SLM), an apparatus for patterning a workpiece and a method of reducing an imprinting or hysteresis effect of a movable micro-element.

Claims

1. A movable micro-element (10) with reduced imprinting effect arranged spaced apart from a surface (20) including:

at least one restoring element (60, 70) connected to said movable micro-element (10),

at least one address electrode (40) arranged on said surface (20) and operable to electrostatically attract said movable micro-element (10) wherein said address electrode (40) begins at a first potential, is set to a second potential defining a non addressed state before a predetermined pulsed signal is emitted onto said movable micro-element (10), and is switched from said second potential to a third potential defining an addressed state prior to and holding it there during the predetermined pulsed signal.

2. The movable micro-element (10) according to claim 1, wherein said movable micro-element (10) is switched back into said non addressed state after being in said addressed state by switching said third potential back to said second potential.

3. The movable micro-element (10) according to claim 2, wherein said movable microelement is kept at said addressed state for a time period which is shorter than 10 ms.

4. The movable micro-element (10) according to claim 1, wherein said movable micro-element (10) is switched into an electrostatically unattracted state after being in said second potential.

5. The movable micro-element (10) according to claim 4, wherein said predetermined pulsed signal is operable to clear out a potential difference between said address electrode (40) and said movable micro-element (10) and thereby restoring said movable micro-element (10) to said electrostatically unattracted state.

6. The movable micro-element (10) according to claim 1, wherein said predetermined pulsed signal is electromagnetic radiation directed onto said movable micro-element (10).

7. The movable micro-element (10) according to claim 1, wherein said predetermined pulsed signal is an electric signal operable to initiate a discharging of a capacitor connected to said address electrode (40) and loaded with said first potential.

8. The movable micro-element (10) according to claim 1, wherein said movable microelement is kept at said addressed state for a time period which is shorter than 10 ms.

9. The movable micro-element (10) according to claim 8, wherein said predetermined pulsed signal is synchronized with a time period Dt+Dt′

so that the time Dt′

is essentially equal to the pulse length of said predetermined pulsed signal.

10. The spatial light modulator according to claim 9, further including at least one counter electrode (30) arranged on said surface (20) and operable to electrostatically attract said movable micro-element (10) wherein said counter electrodes (30) are set to a potential via a common counter pin.

11. The spatial light modulator according to claim 9, wherein all reflecting elements are in an addressed state for essentially the same period of time.

12. The movable micro-element (10) according to claim 1, wherein a value of said second potential is essentially equal to half a maximum potential addressed to said address electrode (40) and said third potential is essentially equal to said minimum potential addressed to said address electrode (40).

13. The movable micro-element (10) according to claim 1, wherein said movable micro-element (10) is supported along a mid section by a pair of torsion hinges (60) defining a torsional axis.

14. The movable micro-element according to claim 13, further comprising at least one flexure hinge operable to restore said movable micro-element in an undeflected state but at the same time permitting said movable micro-element (10) to tilt around said tilting or torsional axis.

15. The movable micro-element (10) according to claim 13, wherein at least one of said flexure hinges (70) and/or at least one of said torsional axis is meander shaped.

16. The movable micro-element (10) according to claim 1, wherein said movable micro-element (10) is supported along a mid section by a pair of pivot elements (65) defining a tilting axis and where said restoring element is at least one flexure hinge (70) operable to restore said movable micro-element (10) in an undeflected state but at the same time permitting said movable micro-element (10) to tilt around said tilting axis.

17. The movable micro-element (10) according to claim 1, wherein said movable micro-element (10) is supported along one of its mid sections by a pair of flexure hinges (70) operable to restore said movable micro-element (10) to a relaxed state but at the same time permitting said movable micro-element (10) to make an orthogonal movement with respect to said surface (20).

18. The movable micro-element (10) according to claim 17, wherein said flexure hinges (70) are attached to the corners of a polygon-shaped movable micro-element (10).

19. The movable micro-element according to claim 17, wherein said flexure hinges (70) are attached to the sides of a polygon-shaped movable micro-element (10).

20. The movable micro-element (10) according to claim 1, wherein said movable micro-element (10) is supported along two mid sections by two pairs of flexure hinges (70) operable to restore said movable micro-element (10) to a relaxed state but at the same time permitting said movable micro-element (10) to make an orthogonal movement with respect to said surface (20).

21. The movable micro-element (10) according to claim 1, wherein said surface (20) further comprising a counter electrode (30) laterally spaced apart from said address electrode (40) where said address electrode (40) and said counter electrode (30) are operable to electrostatically attract said micro-element (10).

22. The movable micro-element (10) according to claim 21, wherein said predetermined pulsed signal is operable to clear out a potential difference between said address electrode (40) and said counter electrode (30), thereby restoring said movable micro-element (10) to said non addressed state.

23. The movable micro-element (10) according to claim 22, wherein said predetermined pulsed signal is electromagnetic radiation directed onto said movable element (10).

24. The movable micro-element (10) according to claim 22, wherein said predetermined pulsed signal is an electric signal adapted to discharge a capacitor connected to said address electrode (40) and loaded with said first potential.

25. The movable micro-element (10) according to claim 21, wherein said predetermined pulsed signal is operable to clear out a potential difference between said address electrode (40) and a counter electrode (30) and thereby restoring said movable element (10) to an electrostatically unattracted state.

26. A spatial light modulator having a plurality of reflecting elements, wherein said reflecting elements are movable micro-elements (10) according to claim 1.

27. The spatial light modulator according to claim 26, wherein said reflecting elements are set to a potential via a common element pin.

28. An apparatus for patterning a workpiece (60) arranged at an image plane and sensitive to electromagnetic radiation, comprising:

a source (11) emitting electromagnetic radiation directed onto an object plane,

a computer controlled reticle (30) comprising a plurality of reflecting elements, adapted to receive said electromagnetic radiation at said object plane and to relay said electromagnetic radiation toward said work piece (60) arranged at said image plane, where said computer controlled reticle (30) comprising a plurality of reflecting elements wherein said reflecting elements are movable micro-elements according to claim 1.

29. A method of reducing an imprinting effect of a movable micro-element arranged spaced apart from a surface, wherein said surface comprises at least one electrode and the movable micro-element begins at a first potential, including:

setting said movable micro-element to a second potential defining a non addressed state,

switching said movable micro-element from said second potential to a third potential, defining an addressed state, before a predetermined pulsed signal is emitted,

releasing the moveable micro-element from the addressed state after the predetermined pulsed signal.

30. The method according to claim 29, wherein the releasing step includes:

switching said micro-element from said third potential back to said second potential.

31. The method according to claim 29, wherein the releasing step includes:

switching said movable micro-element into an electrostatically unattracted state after being in said addressed state.

32. The method according to claim 31, wherein the releasing step includes:

clearing out a potential difference between said address electrode and said movable micromirror by means of said predetermined pulsed signal and thereby restoring said movable element to said electrostatically unattracted state.

33. The method according to claim 29, wherein said predetermined pulsed signal is an electromagnetic radiation signal directed onto said movable micro-element.

34. The method according to claim 29, wherein said predetermined pulsed signal is an electric signal adapted to initiate a discharging of a capacitor connected to said address electrode and loaded with said first potential.

35. The method according to claim 29, wherein said movable microelement is kept at said addressed state for less than 10 ms.

36. The method according to claim 35 further comprising the action of:

synchronizing said predetermined pulsed signal with said time period Dt+Dt′

so that the time Dt′

is essentially equal to the pulse length of said predetermined signal.

37. The method according to claim 29, wherein a value of said second potential is essentially equal to half a maximum potential addressed to said address electrode defining an undeflected state at both the maximum and a minimum potential addressed to said address electrode and said third potential is essentially equal to said minimum potential addressed to said address electrode.

38. The method according to claim 29, further comprising the action of:

supporting said movable micro-element along a mid section by a pair of torsion hinges defining a torsional axis.

39. The method according to claim 29, further comprising the action of:

supporting said movable micro-element along its mid section by a pair of pivot element defining a tilting axis and where said restoring element is at least one flexure hinge operable to restore said movable micro-element in an undeflected state but at the same time permitting said movable micro-element to tilt around said tilting axis.

40. The method according to claim 39, further comprising the action of:

restoring said movable micro-element with at least one flexure hinge.

41. The method according to claim 39, wherein at least one of said flexure hinges and/or at least one of said torsional axis is meander shaped.

42. The method according to claim 29, further comprising the action of:

supporting said movable micro-element along one of its mid sections by a pair of flexure hinges which are operable to restore said movable micro-element to a relaxed state but at the same time permitting said movable micro-element to make an orthogonal movement with respect to said surface comprising said at least one electrode.

43. The method according to claim 29, further comprising the action of:

supporting said movable micro-element along two mid sections by a pair of flexure hinges operable to restore said movable micro-element to a relaxed state but at the same time permitting said movable micro-element to make an orthogonal movement with respect to said surface comprising said at least one electrode.

44. The method according to claim 43, wherein said flexure hinges are attached to the corners of a polygon.

45. The method according to claim 43, wherein said flexure hinges are attached to the sides of a polygon.

46. The method according to claim 29, where said movable micro-element is a movable micro-element.

47. The method according to claim 29, further comprising the action of:

neutralizing cumulated imprinting effects.

48. The method according to claim 47, wherein said neutralizing action is performed by deflecting individual movable micro element in a reverse direction compared to the way they are deflected during intended operation.

49. The method according to claim 47, wherein individual movable micro elements are deflected in a first direction a given time and a given degree of deflection depending on the cumulated time and degree of deflection in a second deflection direction.

50. The method according to claim 47, wherein said neutralizing of said cumulated imprinting effects are performed between different strips building up a complete pattern on a workpiece.

51. The method according to claim 47, wherein said neutralizing of said cumulated imprinting effects is performed after at least one movable micro element has been deflected a predetermined cumulated time period.

52. The method according to claim 29, wherein said movable microelement is kept at said addressed state for less than 10 ms.

53. A method of reducing an imprinting effect of a movable micro-element arranged spaced apart from a surface, wherein said surface includes at least one address electrode operable to electrostatically attract said movable microelement, the method including:

addressing said address electrode to a first potential,

setting said movable microelement to a second potential defining a non-addressed state,

switching said movable micro-element from said second potential to a third potential, defining an addressed state, before a predetermined pulsed signal is emitted, thereby reducing an addressed state duty cycle of said movable element.

54. The method according to claim 53, further including:

switching said micro-element from said third potential back to said second potential after the predetermined pulse is emitted.

55. The method according to claim 53, further including:

switching said movable micro-element into an electrostatically unattracted state after being in said addressed state.

56. The method according to claim 55, further including:

clearing out a potential difference between said address electrode and said movable micromirror by applying said predetermined pulsed signal and thereby restoring said movable element to said electrostatically unattracted state.