Double substrate reflective spatial light modulator with self-limiting micro-mechanical elements

• US 7,023,607 B2
• Filed: 12/01/2004
• Issued: 04/04/2006
• Est. Priority Date: 06/19/1995
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Reflectivity, Inc. (Texas Instruments, Inc.)
• Inventors: Huibers, Andrew G.
• Primary Examiner(s): THOMPSON, TIMOTHY J
• Application Number:
  US11/001,806
• Publication Number:
  US 20050105160A1
• Time in Patent Office: 489 Days
• Field of Search: 359/291, 359/290, 359/223, 359/224, 359/238, 359/578, 359/579, 359/846, 359/847, 359/849, 359/295, 359/298
• US Class Current: 359/291
• CPC Class Codes: G02B 26/08 for controlling the direction of light in light guides G02B6/35
• 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
• CPC Class Codes: Y10S 359/904 Micromirror

Abstract

A spatial light modulator including first and second substrate, and an array of deflectable elements disposed within a gap between the first and second substrates is disclosed herein. For electrostatically actuating the deflectable elements, an array of electrodes and circuitry is provided and positioned proximate to the deflectable elements.

Claims

1. A spatial light modulator device, comprising:

an array of deflectable reflective elements held on a first substrate for reflecting an incident light so as to produce an image, wherein the adjacent elements in the array have a distance of 0.5 micron or less;

wherein the deflectable reflective elements are microelectromechanical mirror plates with each mirror plate comprising a light reflection layer;

a second substrate; and

a gap between the first and second substrate, wherein the deflectable elements are enclosed in the gap.

2. The device of claim 1, further comprising an array of electrodes and circuitry disposed:

proximate to the deflectable reflective elements for electrostatically actuating the deflectable reflective elements.

3. The device of claim 2, wherein the first substrate is light transmissive;

and the second substrate is a semiconductor substrate having thereon the array of electrodes and circuitry.

4. The device of claim 1, wherein the first and second substrates are bonded together.

5. The device of claim 4, wherein the distance between the first and second substrates is from 1 to 5 microns.

6. The device of claim 1, wherein the first substrate further comprises:

a dielectric layer.

7. The device of claim 4, wherein the substrates are bonded together with a spacer therebetween using an adhesive.

8. The device of claim 7, wherein the adhesive is epoxy.

9. The device of claim 4, wherein the substrates are aligned together such that each deflectable element of the array is aligned with an electrode.

10. The device of claim 7, wherein the spacer is positioned outside the plurality of deflectable elements.

11. The device of claim 1, where in the deflectable element comprises a ceramic material.

12. The device of claim 11, wherein the ceramic material is silicon dioxide or silicon nitride.

13. The device of claim 1, wherein each mirror plate is attached to a hinge such that the mirror plate is operable to rotate.

14. The device of claim 13, wherein the hinge is a torsion hinge.

15. The device of claim 14, wherein the mirror plate comprise a first and second portions such that during the rotation of the mirror plate, the second portion moves towards the first substrate and the first portion moves away from the first substrate;

and wherein the hinge and the mirror plate are positioned in different planes.

16. A projector, comprising:

a light source providing an illumination light;

the spatial light modulator of claim 1 for modulating the illumination light; and

a display target on which the modulated light is projected so as to produce a desired image.

17. A spatial light modulator device, comprising:

an array of deflectable reflective micromirrors fabricated on a light transmissive substrate;

an array of electrode associated with the deflectable elements for deflecting the elements, wherein each deflectable element is associated with and deflected by one electrode; and

wherein each micromirror is attached to a hinge that is in the same plane of the micromirror at a non-deflected state such that the micromirror is operable to rotate relative to the light transmissive substrate; and

wherein the hinge is a torsion hinge.

18. A spatial light modulator device, comprising:

an array of deflectable reflective micromirrors fabricated on a light transmissive substrate;

an array of electrodes associated with the deflectable elements for deflecting the elements, wherein each deflectable element is associated with and deflected by one electrode;

wherein each micromirror is attached to a hinge that is in the same plane of the micromirror at a non-deflected state such that the micromirror is operable to rotate relative to the light transmissive substrate; and

wherein electrodes are on a silicon substrate that is coupled with the light transmissive substrate.

19. The device of claim 18, wherein the light transmissive substrate arid the silicon substrate are bonded together, leaving a gap therebetween, in which gap the deflectable elements are enclosed.

20. The device of claim 18, wherein the each micromirror is operable to be switched between an ON and OFF state in operation.

21. A spatial light modulator device, comprising:

an array of deflectable reflective micromirrors held on a substrate, wherein each micromirror is attached to a deformable hinge that is disposed in a separate plane of the micromirror such that the micromirror is operable to be rotated to an ON state and an OFF state, wherein the OFF state is a state where the micromirror is parallel to the substrate;

an array of electrodes and circuitry disposed proximate to the deflectable micromirrors for deflecting the micromirrors;

wherein the substrate on which the micromirrors are held is a light transmissive substrate; and

wherein the electrodes and circuitry are formed on a silicon substrate bonded to the light transmissive substrate.

22. The device of claim 21, wherein the hinge is a torsion hinge.

23. The device of claim 22, wherein the hinge is disposed between the micromirror and a substrate on which the micromirror is connected to.

24. The device of claim 21, wherein the two substrates are bonded with epoxy.

25. A method of modulating an illumination light so as to produce a desired image, the method comprising:

providing a deflectable reflective micromirror array having a set of array edges and a plurality of micromirrors on a substrate, wherein each micromirror is operable to be rotated to an ON and OFF state, and wherein each micromirror comprises a hinge such that the micromirror is operable to move, wherein the hinge is a torsion hinge, and wherein the micromirror comprises a mirror plate with first and second portions such that during the rotation of the mirror plate, the second portion moves towards the substrate and the first portion moves away from the substrate; and

wherein the hinge and the mirror plate are positioned in different planes, and wherein the micromirrors are operated in a digital manner, and wherein a SRAM type memory cell is located at each micromirror location;

directing the illumination light to the micromirrors along a direction whose projection on the micromirror array is perpendicular to the edge of the micromirror array;

individually deflecting the micromirrors of the micromirror array to the ON state and the OFF state; and

projecting the reflected illumination light from the micromirror at the ON state to a display target; and

the reflected illumination light form from the micromirror at the OFF state away from the display target.

26. The method of claim 25, wherein the step of individually deflecting the micromirrors further comprises:

associating the micromirror to an electrode; and

establishing an electrostatic field between the micromirror and the electrode associated thereto.

27. The method of claim 26, further comprising:

maintaining the micromirrors of the micromirror array at one electrical potential.

34. The method of claim 25, wherein adjacent micromirrors in the array have a distance of 0.5 microns or less.

35. The method of claim 25, wherein the micromirrors are provided on a first substrate with a gap formed between the first substrate and a second substrate, wherein the micromirrors are enclosed in the gap.

36. The method of claim 35, wherein the first and second substrates are bonded together.

37. The method of claim 36, wherein the first and second substrates are bonded together via an adhesive with a spacer therebetween.

38. The method of claim 37, wherein the adhesive is an epoxy.

39. The method of claim 25, wherein the micromirrors are operated in a digital manner using active addressing.

40. The method of claim 25, wherein the micromirrors are operated in a digital manner using passive addressing.

41. The method of claim 25, wherein the micromirror comprises a conductive and reflective layer.

42. The method of claim 41, wherein the conductive and reflective layer comprises aluminum.

43. The method of claim 42, wherein a layer of silicon dioxide or silicon nitride is provided on the layer comprising aluminum.

44. The method of claim 42, wherein an electrode is located at each micromirror location for attracting an adjacent mirror plate of the micromirror, wherein the electrode is located higher than other circuit components.

45. The method of claim 42, wherein the micromirror comprises a motion stop.

46. The method of claim 42, wherein the micromirror is a square mirror.

28. A spatial light modulator device, comprising:

an array of deflectable reflective micromirrors, each of which is attached to a deformable hinge;

an array of electrodes and circuitry on a silicon substrate disposed proximate to the micromirrors for deflecting the micromirrors, wherein each micromirror is associated with and deflected by one electrode; and

wherein the hinge is disposed between the micromirror and the electrode associated therewith.

29. The device of claim 28, wherein the micromirrors are formed on a light transmissive substrate.

30. A method of making a micromirror device, the method comprising:

depositing one or more sacrificial layers that are amorphous silicon layers on a substrate;

forming a hinge and a micromirror on the deposited sacrificial layers such that after removal of the sacrificial layers, the micromirror is attached to the hinge; and

removing the sacrificial layers using a vapor phase etchant comprising xenon difluoride.

31. The method of claim 30, wherein the etchant comprises a diluent gas comprising an inert gas.

32. A spatial light modulator device, comprising:

an array of deflectable reflective elements held on a first substrate for reflecting an incident light so as to produce an image, wherein the adjacent elements in the array have a distance of 0.5 micron or less;

a second substrate; and

a gap between the first and second substrate, wherein the deflectable elements are enclosed in the gap.

33. A spatial light modulator device, comprising:

an array of deflectable reflective elements held on a first substrate for reflecting an incident light so as to produce an image, wherein the adjacent elements in the array have a distance of 0.5 micron or less;

wherein the first substrate further comprises;

a dielectric layer.