Micromirror having reduced space between hinge and mirror plate of the micromirror

• US 7,002,726 B2
• Filed: 01/11/2005
• Issued: 02/21/2006
• Est. Priority Date: 07/24/2003
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Reflectivity, Inc. (Texas Instruments, Inc.)
• Inventors: Patel, Satyadev R., Huibers, Andrew G.
• Primary Examiner(s): Mack, Ricky L.
• Assistant Examiner(s): THOMAS, BRANDI N
• Application Number:
  US11/034,294
• Publication Number:
  US 20050213190A1
• Time in Patent Office: 406 Days
• Field of Search: 359/290, 359/291, 359/292, 359/293, 359/294, 359/295, 359/298
• US Class Current: 359/290
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: H04N 5/7458 the modulator being an array of deformable mirrors, e.g. digital micromirror device [DMD]

Abstract

A spatial light modulator is disclosed, along with a method for making such a modulator that comprises an array of micromirror devices. The center-to-center distance and the gap between adjacent micromirror devices are determined corresponding to the light source being used so as to optimize optical efficiency and performance quality. The micromirror device comprises a hinge support formed on a substrate and a hinge that is held by the hinge support. A mirror plate is connected to the hinge via a contact, and the distance between the mirror plate and the hinge is determined according to desired maximum rotation angle of the mirror plate, the optimum gap and pitch between the adjacent micromirrors. In a method of fabricating such spatial light modulator, one sacrificial layer is deposited on a substrate followed by forming the mirror plates, and another sacrificial layer is deposited on the mirror plates followed by forming the hinge supports. The two sacrificial layers are removed via the small gap between adjacent mirror devices with spontaneous vapor phase chemical etchant. Also disclosed is a projection system that comprises such a spatial light modulator, as well as a light source, condensing optics, wherein light from the light source is focused onto the array of micromirrors, projection optics for projecting light selectively reflected from the array of micromirrors onto a target, and a controller for selectively actuating the micromirrors in the array.

Claims

1. A spatial light modulator, comprising:

an array of movable mirror plates held on a substrate, each mirror plate being attached to a hinge that is supported by a hinge structure such that the minor plate can rotate relative to a substrate, on which the hinge structure is formed; and

wherein the hinge and the mirror plate are spaced apart from 0.15 to 0.45 micrometers in a direction perpendicular to the substrate and wherein each mirror plate has an area; and

wherein a ratio of a summation of all areas of the mirror plates to an area of the substrate is 90 percent or more.

2. The spatial light modulator of claim 1, wherein the adjacent mirror plates of the array of mirror plates have a center-to-center distance from 4.38 to 10.16 micrometers.

3. The spatial light modulator of claim 1, wherein the adjacent mirror plates of the array of mirror plates have a gap from 0.15 to 0.25 micrometers when the adjacent mirror plates are parallel to the substrate.

4. The spatial light modulator of claim 1, wherein the adjacent mirror plates have a gap from 0.25 to 0.45 micrometers.

5. The spatial light modulator of claim 1, wherein the adjacent mirror plates of the array of mirror plates have a gap of 0.45 micrometers or less when the adjacent mirror plates are parallel to the substrate.

6. The spatial light modulator of claim 1, wherein the array of minor plates comprises at least 1280 mirror plates along a length of the mirror plate array.

7. The spatial light modulator of claim 1, wherein the array of mirror plates comprises at least 1400 mirror plates along a length of the mirror plate array.

8. The spatial light modulator or claim 1, wherein the array of mirror plates comprises at least 1600 mirror plates along a length of the mirror plate array.

9. The spatial light modulator of claim 1, wherein the ray of mirror plates comprises at least 1920 minor plates along a length of the mirror plate array.

10. The spatial light modulator of claim 1, wherein the hinge and the mirror plate is spaced apart from 0.15 to 0.25 micrometers.

11. The spatial light modulator of claim 1, wherein the hinge and the mirror plate is spaced apart from 0.25 to 0.35 micrometers.

12. The spatial light modulator of claim 1, wherein the hinge and the mirror plate is spaced apart from 0.35 to 0.45 micrometers.

13. The spatial light modulator of claim 2, wherein the center-to-center distance of adjacent mirror plates is from 6.23 to 9.34 micrometers.

14. The spatial light modulator of claim 2, wherein the center-to-center distance of adjacent minor plates is from 4.38 to 6.57 micrometers.

15. The spatial light modulator of claim 2, wherein the center-to-center distance of adjacent mirror plates is from 4.38 to 9.34 micrometers.

16. The spatial light modulator of claim 1, wherein the hinge is attached to the mirror plate such that the mirror plate can rotate relative to the substrate along a rotation axis that is parallel to but offset from a diagonal of the mirror plate when viewed from the top of the mirror plate;

wherein the mirror plate can rotate to an angle at least 14 degrees relative to the substrate; and

wherein the adjacent mirror plates has a center-to-center distance from 4.38 to 10.16 micrometers; and

wherein the hinge and the mirror plate is spaced apart from 0.15 to 0.25 micrometers.

17. The spatial light modulator of claim 1, further comprising:

an electrode proximate to each mirror plate for electrostatically deflecting the mirror plate.

18. The spatial light modulator of claim 1, wherein the substrate is glass or quartz that is visible light transmissive.

19. The spatial light modulator of claim 18, wherein the substrate comprises an anti-reflection film on a surface of the substrate.

20. The spatial light modulator of claim 19, wherein the substrate comprises a light absorption frame around an edge of the substrate.

21. The spatial light modulator of claim 1, wherein each mirror plate rotate relative to the substrate in response to an electrostatic field.

22. The spatial light modulator of claim 1, further comprising:

a first electrode that drives the mirror plate rotate in a first rotation direction relative to the substrate; and

a second electrode that drives the minor plate rotate in a second rotation direction opposite to the first rotation direction relative to the substrate.

23. The spatial light modulator of claim 22, wherein the first electrode and the second electrode are on the same side relative to the rotation axis of the mirror plate.

24. The spatial light modulator of claim 22, wherein the first electrode and the second electrode are on the opposite sides relative to the rotation axis of the mirror plate.

25. The spatial light modulator of claim 1, wherein the substrate is semiconductor.

26. The spatial light modulator of claim 1, wherein the mirror plate is attached to the hinge such that the mirror plate rotates in a first direction to an angle from 15°

degrees to 27°

degrees relative to the substrate.

27. The spatial light modulator of claim 26, wherein the mirror plate is attached to the hinge such that the mirror plate rotates in a second direction to an angle from 2°

degrees to 9°

degrees relative to the substrate.

28. The spatial light modulator of claim 1, wherein the mirror plate is attached to the hinge such that the mirror plate rotates in a first direction to an angle from 17.5°

degrees to 22.5°

degrees relative to the substrate.

29. The spatial light modulator of claim 26, wherein the mirror plate is attached to the hinge such that the mirror plate rotates in a second direction to an angle from 2°

degrees to 9°

degrees relative to the substrate.

30. The spatial light modulator of claim 1, wherein the mirror plate is attached to the hinge such that the mirror plate rotates in a first direction to an angle around 20°

degrees relative to the substrate.

31. The spatial light modulator of claim 29, wherein the mirror plate is attached to the hinge such that the mirror plate rotates in a second direction to an angle from 2°

degrees to 9°

degrees relative to the substrate.

32. The spatial light modulator of claim 1, wherein the minor plate is attached to the hinge such that the mirror plate rotates in a first direction to an angle around 30°

degrees relative to the substrate.

33. The spatial light modulator of claim 32, wherein the mirror plate is attached to the hinge such that the mirror plate rotates in a second direction to an angle from 2°

degrees to 9°

degrees relative to the substrate.

34. The spatial light modulator of claim 32, wherein a center-to-center distance between adjacent mirror plates is from 4.38 to 10.16 micrometers.

35. The spatial light modulator of claim 2, wherein the mirror plate is attached to the hinge such that the mirror plate rotates in a first direction to an angle from 12°

degrees to 20°

degrees relative to the substrate.

36. The spatial light modulator of claim 35, wherein the mirror plate is attached to the hinge such that the mirror plate rotates in a second direction to an angle from 2°

degrees to 9°

degrees relative to the substrate.

37. The spatial light modulator of claim 34, wherein the mirror plate is attached to the hinge such that the mirror plate rotates in a first direction to an angle from 12°

degrees to 20°

degrees relative to the substrate.

38. The spatial light modulator of claim 34, wherein the mirror plate is attached to the hinge such that the mirror plate rotates in a second direction to an angle from 2°

degrees to 9°

degrees relative to the substrate.

39. A projection system, comprising:

a light source;

a spatial light modulator that further comprises;

an array of mirror devices formed on a substrate for selectively reflecting light incident on the mirror devices, wherein each mirror device comprises;

a mirror plate for reflecting light;

a hinge attached to the mirror plate such that the mirror plate can rotate

relative to the substrate, wherein the hinge and the mirror plate are spaced apart from 0.15 to 0.45 micrometers; and

a hinge support on the substrate for holding the hinge on the substrate;

wherein each mirror plate has an area; and

wherein a ratio of a summation of all areas of the mirror plates to an area of the substrate is 90 percent or more,

a condensing lens for directing light from the light source onto the spatial light modulator; and

a projecting lens for collecting and directing light reflected from the spatial light modulator onto a display target.