INTERFEROMETRIC OPTICAL DISPLAY SYSTEM WITH BROADBAND CHARACTERISTICS

• US 20100128339A1
• Filed: 12/09/2009
• Published: 05/27/2010
• 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 8,077,379 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 display device, comprising:

providing a transparent substrate;

forming an absorber layer on the substrate; and

forming an array of interferometric modulators, wherein the interferometric modulators comprise a movable reflective layer over the absorber layer, the absorber layer having an extinction coefficient (k) below a threshold value for wavelengths of light within an operative optical range of the interferometric modulators.

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

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

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

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

6. The method of claim 5, wherein the absorber layer has an n to k ratio from about 2.5 to about 6.

7. The method of claim 5, wherein the absorber layer has an n to k ratio of about 3.

8. The method of claim 1, wherein forming the 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 the sacrificial layer to thereby form a cavity between the substrate and the electrically conductive layer.

9. The method of claim 8, wherein the optical stack further comprises a transparent conductive material.

10. The method of claim 9, wherein the absorber layer is deposited over the transparent conductive material.

11. The method of claim 9, wherein the absorber layer is deposited under the transparent conductive material.

12. The method of claim 8, wherein the optical stack further comprises a dielectric layer.

13. The method of claim 12, wherein the absorber layer is integrated within the dielectric layer.

14. The method of claim 8, wherein the sacrificial layer comprises molybdenum, tungsten, amorphous silicon, or organic polymer.

15. The method of claim 1, further comprising depositing the absorber layer in contact with the transparent substrate.

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

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

18. The method of claim 1, wherein the absorber layer comprises germanium, germanium alloy, doped germanium, or doped germanium-containing alloy.

19. The method of claim 18, wherein the absorber layer further comprises a metal layer.

20. The method of claim 19, wherein the 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 display device made by the method of claim 1.

23. A method of using a display device, comprising:

transmitting light through a substrate; and

interferometrically reflecting light with an interferometric modulator comprising an absorber over a portion of the substrate and a movable reflective layer over the absorber, wherein the absorber has an extinction coefficient (k) below a threshold value for wavelengths of light within an operative optical range of the interferometric modulator.

24. The method of claim 23, wherein the threshold value is about 2.5.

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

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

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

28. The method of claim 27, wherein the absorber has an n to k ratio from about 2.5 to about 6.

29. The method of claim 27, wherein the absorber has an n to k ratio of about 3.