MEMS display devices and methods of fabricating the same

• US 7,903,316 B2
• Filed: 07/24/2008
• Issued: 03/08/2011
• Est. Priority Date: 07/25/2007
• Status: Expired due to Fees

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Ganti, Surya Prakash, Bos, Jan, Chang, Hung-Ta, Kothari, Manish
• Primary Examiner(s): Thompson; Timothy J
• Application Number:
  US12/179,337
• Publication Number:
  US 20090086306A1
• Time in Patent Office: 957 Days
• Field of Search: 359/223, 359/224, 359/290, 359/291, 359/292, 359/238
• 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

Abstract

MEMS devices include materials which are used in LCD or OLED fabrication to facilitate fabrication on the same manufacturing systems. Where possible, the same or similar materials are used for multiple layers in the MEMS device, and use of transparent conductors for partially transparent electrodes can be avoided to minimize the number of materials needed and minimize fabrication costs. Certain layers comprise alloys selected to achieve desired properties. Intermediate treatment of deposited layers during the manufacturing process can be used to provide layers having desired properties.

Claims

1. An optical MEMS device, comprising:

a conductive optical absorber formed over a substrate and patterned to form strip electrodes, wherein the optical absorber serves as the primary conductor in said strip electrodes within optically active areas of the MEMS device;

at least one support structure formed over the optical absorber; and

a conductive deformable layer formed over the at least one support structure and spaced apart from the conductive optical absorber, wherein the deformable layer is electrostatically deflectable towards the optical absorber, and wherein the MEMS device functions as an interferometric modulator.

2. The MEMS device of claim 1, wherein the optical absorber comprises a molybdenum-chromium alloy comprising about 2 atomic % chromium.

3. The MEMS device of claim 2, wherein the optical absorber has a thickness of about 70-75 angstroms.

4. The MEMS device of claim 1, wherein the optical absorber reflects between about 28.5% and 34.5% of incident visible light.

5. The MEMS device of claim 1, additionally comprising a blackmask absorber layer underlying at least a portion of the optical absorber, wherein the blackmask absorber comprises the same material as the optical absorber.

6. The MEMS device of claim 5, wherein the MEMS device comprises a sacrificial layer between the deformable layer and the optical absorber, wherein the sacrificial layer comprises the same material as the optical absorber and blackmask absorber.

7. The MEMS device of claim 6, wherein each of the sacrificial layer, optical absorber, and blackmask absorber comprise a layer of molybdenum.

8. The MEMS device of claim 5, wherein at least the blackmask absorber and the optical absorber form an interferometric black mask that absorbs a portion of incident light.

9. The MEMS device of claim 5, wherein the blackmask absorber is located in optically inactive areas of the display.

10. The MEMS device of claim 5, wherein at least a portion of the blackmask absorber layer underlies a portion of said at least one support structure.

11. The MEMS device of claim 1, wherein the deformable layer comprises a reflective sublayer facing the optical absorber and a mechanical sublayer overlying the reflective sublayer, wherein the reflective sublayer comprises aluminum and the mechanical sublayer comprises nickel.

12. The MEMS device of claim 11, wherein the reflective sublayer comprises an aluminum-neodymium alloy.

13. The MEMS device of claim 12, wherein the aluminum-neodymium allow comprises about 2 atomic % neodymium.

14. The MEMS device of claim 11, wherein the mechanical sublayer comprises a nickel-boron alloy.

15. The MEMS device of claim 14, wherein the nickel-boron alloy comprises about 0.5 atomic % boron.

16. The MEMS device of claim 11, additionally comprising a conductive bussing structure in electrical communication with the optical absorber layer.

17. The MEMS device of claim 16, wherein the bussing structure comprises a first sublayer and a second sublayer, wherein the first sublayer comprises the same material as the reflective sublayer of the deformable layer, and wherein the second sublayer comprises the same material as the mechanical sublayer of the deformable layer.

18. The MEMS device of claim 1, additionally comprising an optical dielectric layer located over at least a portion of the optical absorber, wherein the optical absorber comprises the only conductive material located between the optical dielectric layer and the substrate in the optically active areas of the display.

19. The MEMS device of claim 1, where the MEMS device does not comprise ITO in an optically active area of the display.

20. A method of fabricating an optical MEMS device, comprising:

forming a blackmask absorber layer over a substrate;

forming a conductive optical absorber over the substrate after forming the blackmask absorber layer , wherein the blackmask absorber layer comprises the same material as the optical absorber;

patterning the conductive optical absorber to form strip electrodes, wherein the optical absorber functions as the primary conductor in said strip electrodes in optically active regions of the MEMS device;

forming a sacrificial layer over the optical absorber;

forming at least one support structure over the optical absorber;

forming a conductive deformable layer over the sacrificial layer and the at least one support structure; and

performing a release etch to remove the sacrificial layer, forming a cavity between the deformable layer and the optical absorber.

21. The method of claim 20, wherein the optical absorber comprises a molybdenum-chromium alloy comprising about 2 atomic % chromium.

22. The method of claim 20, wherein the optical absorber has a thickness of about 70-75 angstroms.

23. The method of claim 20, wherein the optical absorber reflects between about 28.5% and 34.5% of incident visible light.

24. The method of claim 20, additionally comprising patterning the blackmask absorber layer to remove the blackmask absorber layer in optically active areas of the MEMS device.

25. The method of claim 20, wherein the sacrificial layer comprises the same material as the optical absorber and blackmask absorber.

26. The method of claim 20, wherein each of the sacrificial layer, the optical absorber, and the blackmask absorber comprise a layer of molybdenum.

27. The method of claim 20, additionally exposing the sacrificial layer to a plasma environment comprising N₂O prior to formation of the deformable layer.

28. The method of claim 27, wherein exposing the sacrificial layer to a plasma environment comprising N₂O is done after formation of the at least one support structure.

29. The method of claim 20, additionally comprising forming a bussing structure in electrical communication with the optical absorber.

30. The method of claim 29, wherein forming the bussing structure comprises:

forming a first bussing sublayer;

exposing the first bussing sublayer to vacuum for a period of time; and

forming a second bussing sublayer over the first layer after exposing the first bussing sublayer to vacuum.

31. The method of claim 30, wherein the first bussing layer comprises an aluminum-neodymium alloy comprising about 2 atomic % neodymium, and wherein the second bussing layer comprises a nickel-boron alloy comprising about 0.5 atomic % boron.

32. The method of claim 20, wherein forming the deformable layer comprises:

forming a reflective sublayer over the sacrificial layer, the reflective sublayer comprising aluminum; and

forming a mechanical sublayer over the first sublayer, the mechanical sublayer comprising nickel.

33. The method of claim 32, wherein the reflective sublayer comprises an aluminum-neodymium alloy comprising about 2% neodymium.

34. The method of claim 32, wherein the mechanical sublayer comprises a nickel-boron alloy comprising about 0.5% boron.

35. An optical MEMS device, comprising:

a conductive optical absorber formed over a substrate and patterned to form strip electrodes, wherein the optical absorber serves as the primary conductor in said strip electrodes within optically active areas of the MEMS device;

a blackmask absorber layer, wherein the blackmask absorber comprises the same material as the optical absorber;

at least one support structure formed over the black mask absorber layer; and

a conductive deformable layer formed over the at least one support structure and spaced apart from the conductive optical absorber, wherein the deformable layer is electrostatically deflectable towards the optical absorber.

36. The device of claim 35, wherein the blackmask absorber is located in optically inactive areas of the display.

37. The device of claim 35, wherein the deformable layer comprises a reflective sublayer facing the optical absorber and a mechanical sublayer overlying the reflective sublayer.

38. The device of claim 36, wherein the reflective sublayer comprises aluminum.