Interferometric optical display system with broadband characteristics

• US 20070236774A1
• Filed: 04/10/2006
• Published: 10/11/2007
• Est. Priority Date: 04/10/2006
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Gousev, Evgeni, Mienko, Marek, Xu, Gang
• Granted Patent: US 7,643,203 B2
• Time in Patent Office: Days
• US Class Current: 359/291
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26
• CPC Class Codes: Y10T 29/49124 On flat or curved insulated base, e.g., printed circuit, etc.

Abstract

Broad band white color can be achieved in MEMS display devices by incorporating a material having an extinction coefficient (k) below a threshold value for wavelength of light within an operative optical range of the interferometric modulator. One embodiment provides a method of making the MEMS display device comprising depositing said material over at least a portion of a transparent substrate, depositing a dielectric layer over the layer of material, forming a sacrificial layer over the dielectric, depositing an electrically conductive layer on the sacrificial layer, and forming a cavity by removing at least a portion of the sacrificial layer. The suitable material may comprise germanium, germanium alloy of various compositions, doped germanium or doped germanium-containing alloys, and may be deposited over the transparent substrate, incorporated within the transparent substrate or the dielectric layer.

Claims

1. A method of making a MEMS display device, comprising:

providing a transparent substrate; and

forming an array of interferometric modulators on the transparent substrate, wherein the interferometric modulator comprises a material having an extinction coefficient (k) below a threshold value for wavelengths of light within an operative optical range of the interferometric modulator.

2. The method of claim 1, wherein said threshold value is about 2.5.

3. The method of claim 1, wherein said extinction coefficient (k) remains substantially constant for wavelengths of light within said operative optical range of the interferometric modulator.

4. The method of claim 1, wherein said extinction coefficient (k) decreases as the wavelength of light increases within said operative optical range of the interferometric modulator.

5. The method of claim 1, wherein said material has a refractive index (n) that increases as the wavelength of light increases within said operative optical range of the interferometric modulator.

6. The method of claim 5, wherein said material has an n to k ratio from about 2.5 to about 6.

7. The method of claim 5, wherein said material has an n to k ratio of about 3.

8. The method of claim 1, wherein forming an array of interferometric modulators comprises:

forming an optical stack on the transparent substrate;

depositing a sacrificial layer over the optical stack;

forming an electrically conductive layer over the sacrificial layer; and

removing at least a portion of sacrificial layer to thereby form a cavity between the substrate and the electrically conductive layer.

9. The method of claim 6, wherein said optical stack further comprises a transparent conductive material.

10. The method of claim 9, wherein said material is deposited over said transparent conductive material.

11. The method of claim 9, wherein said material is deposited under said transparent conductive material.

12. The method of claim 6, wherein said optical stack further comprises a dielectric layer.

13. The method of claim 12, wherein said material is integrated within said dielectric layer.

14. The method of claim 6, wherein the sacrificial layer comprises molybdenum, tungsten, amorphous silicon, or organic polymer.

15. The method of claim 1, further comprising depositing said material over said transparent substrate.

16. The method of claim 1, further comprising integrating the material within transparent substrate.

17. The method of claim 1, wherein said transparent substrate is glass or plastic.

18. The method of claim 1, wherein said material comprises germanium, germanium alloy, doped germanium or doped germanium-containing alloy.

19. The method of claim 18, wherein said material further comprises a metal layer.

20. The method of claim 19, wherein said metal layer comprises a material selected from the group consisting of chromium, molybdenum, refractive metals, and refractive alloys.

21. The method of claim 1, wherein said operative optical range is from about 400 nm to about 700 nm.

22. A MEMS display device made by the method of claim 1.

23. An interferometric display device, comprising:

means for transmitting light; and

means for interferometrically reflecting light through said transmitting means, wherein said reflecting means comprises a material having an extinction coefficient (k) below a threshold value for wavelengths of light within an operative optical range of the interferometric modulator.

24. The interferometric display device of claim 23, wherein said threshold value is about 2.5.

25. The interferometric display device of claim 23, wherein said extinction coefficient (k) that remains substantially constant for wavelengths of light within said operative optical range of the interferometric modulator.

26. The interferometric display device of claim 23, wherein said extinction coefficient (k) decreases as the wavelength of light increases within said operative optical range of the interferometric modulator.

27. The interferometric display device of claim 23, wherein the material has a refractive index (n) that increases as the wavelength of light increases within said operative optical range of the interferometric modulator.

28. The interferometric display device of claim 27, wherein said material has an n to k ratio from about 2.5 to about 6.

29. The interferometric display device of claim 27, wherein said material has an n to k ratio of about 3.

30. The interferometric display device of claim 23, wherein said transmitting means comprises a transparent substrate.

31. The interferometric display device of claim 23, wherein said reflecting means comprises an interferometric modulator comprising a layer of material having an extinction coefficient (k) below a threshold value for wavelength of light within an operative optical range of the interferometric modulator.

32. The interferometric display device of claim 31, wherein said threshold value is about 2.5.

33. The interferometric display device of claim 31, wherein the extinction coefficient (k) remains substantially constant for wavelength of light within said operative optical range of the interferometric modulator.

34. The interferometric display device of claim 31, wherein the extinction coefficient (k) decreases as the wavelength of light increases within said operative optical range of the interferometric modulator.

35. The interferometric display device of claim 31, wherein said material has a refractive index (n) that increases as the wavelength of light increases within said operative optical range of the interferometric modulator.

36. The interferometric display device of claim 35, wherein said material has an n to k ratio from about 2.5 to about 6.

37. The interferometric display device of claim 35, wherein said material has an n to k ratio of about 3.

38. The interferometric display device of claim 23, wherein said layer of material is deposited over said transmitting means.

39. The interferometric display device of claim 23, wherein said layer of material is integrated into said transmitting means.

40. The interferometric display device of claim 39, wherein said transmitting means comprises a transparent substrate and said material is integrated into said transparent substrate.

41. The interferometric display device of claim 23, wherein said material comprises germanium, germanium alloy, doped germanium or doped germanium-containing alloy.

42. The interferometric display device of claim 41, wherein said material further comprises a metal layer.

43. The interferometric display device of claim 42, wherein said metal layer comprises a material selected from the group consisting of chromium, molybdenum, refractive metals, and refractive alloys.

44. A MEMS display device comprising:

a substrate; and

an array of interferometric modulators deposited on said substrate, wherein said array comprises a material having an extinction coefficient (k) below a threshold value for wavelengths of light within an operative optical range of the interferometric modulator.

45. The MEMS display device of claim 44, wherein said threshold value is about 2.5.

46. The MEMS display device of claim 44, wherein said extinction coefficient (k) that remains substantially constant for wavelengths of light within said operative optical range of the interferometric modulator.

47. The MEMS display device of claim 44, wherein said extinction coefficient (k) decreases as the wavelength of light increases within said operative optical range of the interferometric modulator.

48. The MEMS display device of claim 44, wherein said material has a refractive index (n) that increases as the wavelength of light increases within said operative optical range of the interferometric modulator.

49. The MEMS display device of claim 48, wherein said material has an n to k ratio from about 2.5 to about 6.

50. The MEMS display device of claim 48, wherein said material has an n to k ratio of about 3.

51. The MEMS display device of claim 44, wherein said substrate is a transparent substrate.

52. The MEMS display device of claim 49, wherein said transparent substrate comprises glass or plastic.

53. The MEMS display device of claim 44, wherein said material comprises germanium, a germanium alloy, doped germanium or doped germanium-containing alloy.

54. The MEMS display device of claim 53, wherein said material further comprises a metal layer.

55. The MEMS display device of claim 54, wherein said metal layer comprises a material selected from the group consisting of chromium, molybdenum, refractive metals, and refractive alloys.

56. The MEMS display device of claim 44, wherein said material is deposited over said transparent substrate.

57. The MEMS display device of claim 44, wherein said material is integrated into the transparent substrate.

58. The MEMS display device of claim 44, wherein said operative optical range is from about 400 nm to about 700 nm.

59. The MEMS display device of claim 44, wherein said MEMS device comprises a cellular telephone.

60. The MEMS display device of claim 44, comprising:

a processor that is in electrical communication with the array, the processor being configured to process image data; and

a memory device in electrical communication with the processor.

61. The MEMS display device of claim 60, further comprising a driver circuit configured to send at least one signal to the array.

62. The MEMS display device of claim 61, further comprising a controller configured to send at least a portion of the image data to the driver circuit.

63. The MEMS display device of claim 60, further comprising an image source module configured to send the image data to the processor.

64. The MEMS display device of claim 63, wherein the image source module comprises at least one of a receiver, transceiver, and transmitter.

65. The MEMS display device of claim 60, further comprising an input device configured to receive input data and to communicate the input data to the processor.