Spatial light modulator

• US 20080297874A1
• Filed: 04/25/2008
• Published: 12/04/2008
• Est. Priority Date: 10/27/2003
• Status: Active Grant

• Current Assignee: Spatial Photonics Incorporated (Himax Technologies Incorporated)
• Original Assignee: Spatial Photonics Incorporated (Himax Technologies Incorporated)
• Inventors: Pan, Shaoher X.
• Granted Patent: US 7,667,885 B2
• Time in Patent Office: Days
• US Class Current: 359/224.1
• CPC Class Codes: G02B 26/0833 the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD G02B26/0825 takes precedence; micromechanical devices in general B81B
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means

Abstract

A high contrast spatial light modulator for display and printing is fabricated by coupling a high active reflection area fill-ratio and non-diffractive micro-mirror array with a high electrostatic efficiency and low surface adhesion control substrate.

Claims

1. A spatial light modulator, comprising:

a substrate having a plurality of electrodes;

a mirror plate suspended over the plurality of electrodes, the mirror plate having an upper reflective surface and a lower surface, the mirror plate having an upper layer and a lower layer, the upper layer formed of a first material and the lower layer formed of a different second material, the upper layer having the upper reflective surface, and a recess in the lower surface that extends partially but not entirely through the lower layer;

a support post on the substrate; and

a torsion hinge connecting the support post to the mirror plate, the torsion hinge positioned in the recess of the mirror plate and permitting the mirror plate to rotate about an axis of the torsion hinge.

2. The spatial light modulator of claim 1, wherein the upper layer directly contacts the lower layer.

3. The spatial light modulator of claim 2, wherein a bottom surface of the torsion hinge is coplanar with the lower surface of the mirror plate.

4. The spatial light modulator of claim 1, wherein a bottom surface of the torsion hinge is coplanar with the lower surface of the mirror plate.

5. The spatial light modulator of claim 1, wherein the torsion hinge is formed of the second material.

6. The spatial light modulator of claim 1, wherein the first material includes one or more of aluminum or gold.

7. The spatial light modulator of claim 6, wherein the first material is aluminum.

8. The spatial light modulator of claim 1, wherein the second material includes one or more of silicon, aluminum, titanium, tungsten, molybdenum or an alloy thereof.

9. The spatial light modulator of claim 8, wherein the second material includes aluminum and titanium.

10. The spatial light modulator of claim 1, wherein the lower layer is conductive.

11. The spatial light modulator of claim 1, further comprising a lubricant film forming the lower surface of the mirror plate.

12. The spatial light modulator of claim 11, wherein the lubricant film comprises perflouropolyether.

13. The spatial light modulator of claim 1, wherein the mirror plate consists of the upper layer and the lower layer.

14. The spatial light modulator of claim 13, wherein the lower surface of the mirror plate is defined by a bottom surface of the lower layer.

15. The spatial light modulator of claim 1, wherein a thickness of the lower layer is between 0.3 and 0.5 microns.

16. The spatial light modulator of claim 15, wherein a thickness of the upper layer is approximately 400 Angstroms.

17. The spatial light modulator of claim 15, wherein a gap between a top surface of the torsion hinge and a bottom surface of the recess is more than 0.13 microns.

18. The spatial light modulator of claim 1, further comprising functional circuitry formed on the substrate including a series of memory cells and word-line/bit-line interconnection structures.

19. The spatial light modulator of claim 1, wherein each electrode of the plurality of electrodes is a step electrode with a first portion at a first height above a surface of the substrate and a second portion at a different second height above the surface of the substrate.

20. The spatial light modulator of claim 1, further comprising a plurality of landing tips extending perpendicularly from a surface of the substrate to limit motion of the mirror plate.

21. A spatial light modulator, comprising:

a substrate having a plurality of electrodes;

a mirror plate suspended over the plurality of electrodes, the mirror plate having an upper reflective surface and a lower surface;

a support post on the substrate;

a torsion hinge connecting the support post to the mirror plate, the torsion hinge permitting the mirror plate to rotate about an axis of the torsion hinge; and

a landing tip on the substrate, the landing tip projecting above at least some of the plurality of electrodes and configured to contact the lower surface of the mirror plate to limit the rotation of the mirror plate.

22. The spatial light modulator of claim 21, wherein the landing tip extends vertically from the substrate.

23. The spatial light modulator of claim 21, further comprising a plurality of landing tips, the landing tip being one of the plurality of landing tips.

24. The spatial light modulator of claim 23, wherein there are exactly two landing tips for each mirror plate.

25. The spatial light modulator of claim 23, wherein the plurality of landing tips are disposed on opposing sides of the axis of the torsion hinge.

26. The spatial light modulator of claim 25, wherein the plurality of landing tips are disposed at equal distances from the axis of the torsion hinge.

27. The spatial light modulator of claim 21, wherein each electrode of the plurality of electrodes is a step electrode with a first portion at a first height above a surface of the substrate and a second portion at a different second height above the surface of the substrate.

28. The spatial light modulator of claim 27, wherein the landing tip projects above the first portion of the electrode.

29. The spatial light modulator of claim 28, wherein a top of the landing tip is coplanar with the second portion of the electrode.

30. The spatial light modulator of claim 21, wherein landing tip is formed of one or more of silicon, aluminum, titanium, tungsten, molybdenum or an alloy thereof.

31. The spatial light modulator of claim 30, wherein landing tip is formed of aluminum and titanium.

32. The spatial light modulator of claim 21, further comprising circuitry formed on the substrate to connect the landing tip to a first bias voltage source, to connect a first of the plurality of electrodes to a second bias voltage source and to connect a second of the plurality of electrodes to a third bias voltage source.

33. The spatial light modulator of claim 32, further comprising a first landing tip and a second landing tip, the landing tip being one of the first landing tip or the second landing tips, the first landing tip and the second landing tip electrically connected to the mirror plate.

34. The spatial light modulator of claim 32, wherein the first landing tip and the second landing tip are disposed on opposing sides of the axis of the torsion hinge.

35. The spatial light modulator of claim 32, wherein the first of the plurality of electrodes and the second of the plurality of electrodes are disposed on opposing sides of the axis of the torsion hinge.

36. The spatial light modulator of claim 21, wherein the landing tip is electrically connected to the mirror plate.

37. The spatial light modulator of claim 36, further comprising circuitry formed on the substrate to apply a bipolar pulse voltage to the landing tip and the mirror plate.

38. The spatial light modulator of claim 21, further comprising circuitry formed on the substrate to apply a voltage waveform configured to move the mirror plate and deform the landing tip to generate an elastic strain in the landing tip.

39. The spatial light modulator of claim 38, wherein the waveform is configured such that the elastic strain is converted to kinetic energy to move the mirror plate away from the landing tip.

40. The spatial light modulator of claim 38, wherein the waveform comprises a bipolar pulse voltage.

41. A spatial light modulator, comprising:

a substrate;

a plurality of electrodes formed on the substrate, at least one of the plurality of electrodes having a first region and a second region;

a mirror plate suspended over the plurality of electrodes, the mirror plate having an upper reflective surface and a lower surface, wherein there is a first gap of a first distance between the first region and the lower surface of the mirror plate and a second gap of second distance greater than the first distance between the second region and the lower surface of the mirror plate;

a support post on the substrate; and

a torsion hinge connecting the support post to the mirror plate, the torsion hinge permitting the mirror plate to rotate about an axis of the torsion hinge.

42. The spatial light modulator of claim 41, wherein the first portion of the at least one electrode is at a first height above a surface of the substrate and the second portion of the at least one electrode is at a different second height above the surface of the substrate.

43. The spatial light modulator of claim 41, wherein the first region is about one micron above the second region.

44. The spatial light modulator of claim 41, wherein the first region is closer to the axis than the second region.

45. The spatial light modulator of claim 41, wherein the plurality of electrodes includes a first electrode and a second electrode disposed on opposing sides of the axis of the torsion hinge.

46. The spatial light modulator of claim 45, wherein each of the first electrode and second electrode have the first portion at the first height above the surface of the substrate and the second portion at the different second height above the surface of the substrate.

47. The spatial light modulator of claim 45, wherein the first electrode and second electrode are symmetric across the axis of the torsion hinge.

48. The spatial light modulator of claim 41, wherein the at least one of the plurality of electrodes has a third region and wherein there is a third gap of a third distance different from the first distance and second distance between the third region and the lower surface of the mirror plate.

49. The spatial light modulator of claim 41, wherein the at least one of the plurality of electrodes has N regions and wherein there are N gaps of a N different distances between the respective regions and the lower surface of the mirror plate, wherein N is ten or less.

50. The spatial light modulator of claim 49, wherein N is two or three.

51. The spatial light modulator of claim 41, wherein each electrode includes one or more of silicon, aluminum, titanium, tungsten, molybdenum or an alloy thereof.

52. The spatial light modulator of claim 51, wherein each electrode is formed of titanium and aluminum.

53. The spatial light modulator of claim 41, further comprising a landing tip on the substrate, the landing tip projecting above the second region and configured to contact the lower surface of the mirror plate to limit the rotation of the mirror plate.

54. The spatial light modulator of claim 53, wherein a top of the landing tip is coplanar with the first region of the electrode.

55. The spatial light modulator of claim 53, wherein the landing tip is further from the axis of the torsion hinge than the first region.

56. The spatial light modulator of claim 41, further comprising circuitry formed on the substrate to connect a first of the plurality of electrodes to a first bias voltage source and to connect a second of the plurality of electrodes to a second bias voltage source.