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

• US 6,690,502 B2
• Filed: 05/20/2002
• Issued: 02/10/2004
• 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): Spector, David N.
• Application Number:
  US10/153,138
• Publication Number:
  US 20020176150A1
• Time in Patent Office: 631 Days
• Field of Search: 359/290, 359/291, 359/292, 359/295, 216/2, 216/24, 216/33, 427/162, 438/29
• 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 includes an upper optically transmissive substrate held above a lower substrate containing addressing circuitry. One or more electrostatically deflectable elements are suspended by hinges from the upper substrate. In operation, individual mirrors are selectively deflected and serve to spatially modulate light that is incident to, and then reflected back through, the upper substrate. Motion stops may be attached to the reflective deflectable elements so that the mirror does not snap to the bottom substrate. Instead, the motion stop rests against the upper substrate thus limiting the deflection angle of the reflective deflectable elements.

Claims

1. A method of making a spatial light modulator, comprising:

forming a plurality of deflectable elements by chemical vapor deposition on a light transmissive substrate;

forming a silicon substrate with addressing circuitry thereon using VLSI technology; and

joining the light transmissive substrate and the silicon substrate together.

2. The method of claim 1, wherein the chemical vapor deposition is low pressure chemical vapor deposition (LPCVD).

3. The method of claim 1, wherein the deflectable elements comprise a first portion and a second portion such that during deflection of the deflectable elements, the second portion moves towards the optically transmissive substrate as the first portion moves away from the optically transmissive substrate.

4. The method of claim 1, wherein the silicon substrate comprises electrodes disposed proximate to corresponding deflectable elements for deflecting the deflectable elements.

5. The method of claim 4, the deflectable elements are micromirrors comprising light reflecting layers.

6. The method of claim 5, wherein the micromirrors comprise deflectable plates attached to the light transmissive substrate via flexible hinges.

7. The method of claim 6, wherein each hinge extends across the deflectable element between the electrode and the deflectable element.

8. The method of claim 5, wherein the hinges are torsion hinges.

9. The method of claim 6, wherein the deflectable plates comprise silicon nitride.

10. The method of claim 1, comprising forming one or more passivation layers on the silicon substrate.

11. The method of claim 1, wherein the deflectable elements are formed to have a first portion and a second portion, the second portion constructed so as to be capable of moving towards the light transmissive substrate when the first portion moves away from the light transmissive substrate and towards the silicon substrate.

12. The method of claim 1, wherein the addressing circuitry includes a memory array.

13. The method of claim 12, wherein the memory array comprises DRAM circuits.

14. The method of claim 12, wherein the memory array comprises SRAM circuits.

15. The method of claim 1, wherein the deflectable elements are electrically coupled to the silicon substrate.

16. The method of claim 6, wherein the hinges are thinner than the deflectable plates.

17. A method of making a spatial light modulator, comprising:

forming a plurality of deflectable elements by chemical vapor deposition on a light transmissive substrate;

forming a silicon substrate with addressing circuitry thereon using CMOS technology; and

joining the light transmissive substrate and the silicon substrate together.

18. The method of claim 17, wherein the chemical vapor deposition is low pressure chemical vapor deposition (LPCVD).

19. The method of claim 17, wherein the deflectable elements comprise a first portion and a second portion such that during deflection of the deflectable elements, the second portion moves towards the optically transmissive substrate as the first portion moves away from the optically transmissive substrate.

20. The method of claim 17, wherein the silicon substrate comprises electrodes disposed proximate to corresponding deflectable elements for deflecting the deflectable elements.

21. The method of claim 20, wherein the deflectable elements are micromirrors comprising light reflecting layers.

22. The method of claim 21, wherein the micromirrors comprise deflectable plates attached to the light transmissive substrate via flexible hinges.

23. The method of claim 22, wherein each hinge extends across the deflectable element between the electrode and the deflectable element.

24. The method of claim 21, wherein the hinges are torsion hinges.

25. The method of claim 22, wherein the deflectable plates comprise silicon nitride.

26. The method of claim 17, comprising forming one or more passivation layers on the silicon substrate.

27. The method of claim 17, wherein the deflectable elements are formed to have a first portion and a second portion, the second portion constructed so as to be capable of moving towards the light transmissive substrate when the first portion moves away from the light transmissive substrate and towards the silicon substrate.

28. The method of claim 17, wherein the addressing circuitry includes a memory array.

29. The method of claim 28, wherein the memory array comprises DRAM circuits.

30. The method of claim 28, wherein the memory array comprises SRAM circuits.

31. The method of claim 17, wherein the deflectable elements are electrically coupled to the silicon substrate.

32. The method of claim 22, wherein the hinges are thinner than the deflectable plates.

33. A spatial light modulator, comprising:

a first substrate bonded to a second substrate with a gap therebetween;

the first substrate being a light transmissive substrate having a plurality of deflectable elements thereon;

the second substrate having CMOS circuitry and electrodes thereon for causing deflection of the deflectable elements on the first substrate.

34. The spatial light modulator of claim 33, wherein the silicon substrate comprises electrodes disposed proximate to corresponding deflectable elements for deflecting the deflectable elements.

35. The spatial light modulator of claim 34, wherein the deflectable elements are micromirrors comprising light reflecting layers.

36. The spatial light modulator of claim 35, wherein the micromirrors comprise deflectable plates attached to the light transmissive substrate via flexible hinges.

37. The spatial light modulator of claim 36, wherein each hinge extends across the deflectable element between the electrode and the deflectable element.

38. The spatial light modulator of claim 35 wherein the hinges are torsion hinges.

39. The spatial light modulator of claim 36, wherein the deflectable plates comprise silicon nitride.

40. The spatial light modulator of claim 33, comprising forming one or more passivation layers on the silicon substrate.

41. The spatial light modulator of claim 33, wherein the addressing circuitry includes a memory array.

42. The spatial light modulator of claim 41, wherein the memory array comprises DRAM circuits.

43. The spatial light modulator of claim 41, wherein the memory array comprises SRAM circuits.

44. The spatial light modulator of claim 33, wherein the deflectable elements are electrically coupled to the silicon substrate.

45. The spatial light modulator of claim 36, wherein the hinges are thinner than the deflectable plates.

46. A spatial light modulator, comprising:

a first substrate bonded to a second substrate with a gap therebetween;

the first substrate being a light transmissive substrate having a plurality of deflectable elements thereon;

the second substrate having circuitry and aluminum electrodes for causing deflection of the deflectable elements on the first substrate.