METHOD FOR ASSEMBLING A TILED, FLAT- PANEL MICRODISPLAY ARRAY

• US 20020001051A1
• Filed: 02/15/1999
• Published: 01/03/2002
• Est. Priority Date: 02/15/1999
• Status: Active Grant

• Current Assignee: Hanger Solutions, LLC (IP Investments Group LLC)
• Original Assignee: Rainbow Displays, Inc.
• Inventors: KRUSIUS, J. PETER, SERAPHIM, DONALD P.
• Granted Patent: US 6,476,886 B2
• Time in Patent Office: Days
• US Class Current: 349/73
• CPC Class Codes: G02F 1/13336 Combining plural substrates to produce large-area displays, e.g. tiled displays
• CPC Class Codes: G02F 1/136277 formed on a semiconductor substrate, e.g. of silicon

Abstract

This invention describes fabrication techniques for producing microdisplays suitable for combining into tiled, flat-panel displays having visually imperceptible seams. Assembly techniques to overcome flatness requirements imposed by tiled, flat-panel display assemblies are also described. Edge treatment techniques for individual microdisplays while still part of the silicon die or wafer are also described. The use of these inventive techniques allows the assembly microdisplays into tiled, flat-panel that are appear visually seamless and optically uniform.

Claims

1. A method for assembling a plurality of microdisplay tiles into a tiled, flat-panel display, the projected image of which display having visually imperceptible seams, the steps comprising;

a) providing a plurality of monolithic microdisplay tiles, each microdisplay having a front, active face and a rear, mounting face;

b) arranging said plurality of microdisplay tiles with respect to one another;

c) bonding said plurality of microdisplay tiles to an optically flat carrier;

d) applying a filling material to said rear faces of said plurality of tiles; and

e) attaching a common substrate to said rear faces of said plurality of tiles.

2. The method for assembling a plurality of microdisplay tiles as recited in claim 1, wherein said optically flat carrier is a temporary substrate.

3. The method for assembling a plurality of microdisplay tiles as recited in claim 2, wherein said common substrate is a permanent substrate.

4. The method for assembling a plurality of microdisplay tiles as recited in claim 1, the steps further comprising:

releasing said tile carrier.

5. The method for assembling a plurality of microdisplay tiles as recited in claim 3, wherein said arranging step (b) comprises aligning said plurality of microdisplay tiles relative to at least one alignment mark.

6. The method for assembling a plurality of microdisplay tiles as recited in claim 5, wherein at least one of said plurality of tiles comprises a tile alignment mark, said tile alignment mark being compatible with said at least one alignment mark on said tile carrier.

7. The method for assembling a plurality of microdisplay tiles as recited in claim 5, the steps further comprising:

polishing a front face of said tiles and said filling material to a predetermined degree of flatness.

8. The method for assembling a plurality of microdisplay tiles as recited in claim 5, wherein said bonding step (c) comprises a vacuum technology.

9. The method for assembling a plurality of microdisplay tiles as recited in claim 5, wherein said bonding step (c) comprises using an adhesive technology.

10. The method for assembling a plurality of microdisplay tiles as recited in claim 9, wherein said bonding step (c) comprises curing media with one or more of the set of heat, infrared energy, ultraviolet light, pressure, chemical reaction and time.

11. The method for assembling a plurality of microdisplay tiles as recited in claim 5, further comprising the step of bonding said tiles to a common substrate.

12. The method for assembling a plurality of microdisplay tiles as recited in claim 7, wherein said polishing step comprises chemical/mechanical polishing (CMP).

13. The method for assembling a plurality of microdisplay tiles as recited in claim 12, wherein said predetermined degree of flatness of said front face is within a dimension less than the wavelength of visible light.

14. The method for assembling a plurality of microdisplay tiles as recited in claim 3, wherein said arranging step (b) comprises aligning said plurality of microdisplay tiles relative to at least one mechanical stop.

15. The method for assembling a plurality of microdisplay tiles as recited in claim 14, wherein said mechanical stop is constructed from one from the group of polymers, ceramics, glass and metals.

16. The method for assembling a plurality of microdisplay tiles as recited in claim 15, wherein said mechanical stop comprises precision spacer balls.

17. The method for assembling a plurality of microdisplay tiles as recited in claim 15, wherein said mechanical stop comprises precision cylinders.

18. The method for assembling a plurality of microdisplay tiles as recited in claim 15, wherein said at least one mechanical stop has been previously fabricated on said optically flat carrier.

19. The method for assembling a plurality of microdisplay tiles as recited in claim 14, the steps further comprising:

polishing said front face and said filling material to a predetermined degree of flatness.

20. The method for assembling a plurality of microdisplay tiles as recited in claim 14, wherein said bonding step (c) comprises a vacuum technology.

21. The method for assembling a plurality of microdisplay tiles as recited in claim 14, wherein said bonding step (c) comprises using an adhesive technology.

22. The method for assembling a plurality of microdisplay tiles as recited in claim 21, wherein said bonding step (c) comprises curing media with one or more of the set of heat, infrared energy, ultraviolet light, pressure, chemical reaction and time.

23. The method for assembling a plurality of microdisplay tiles as recited in claim 14, further comprising the step of bonding to said common substrate.

24. The method for assembling a plurality of microdisplay tiles as recited in claim 19, wherein said polishing step comprises chemical/mechanical polishing (CMP).

25. The method for assembling a plurality of microdisplay tiles as recited in claim 19, wherein said predetermined degree of flatness of said front face is within a dimension less than the wavelength of light.

26. The method for assembling a plurality of microdisplay tiles as recited in claim 1, wherein said plurality of microdisplay tiles comprises a mirror array.

27. The method for assembling a plurality of microdisplay tiles as recited in claim 26, further comprising the step of:

polishing said mirror array to a predetermined optical precision.

28. The method for assembling a plurality of microdisplay tiles as recited in claim 23, the steps further comprising:

repolishing said mirror array to a predetermined optical precision, if required.

29. The method for assembling a plurality of microdisplay tiles as recited in claim 1, wherein said arranging step (b) results in at least one gap between at least two of said plurality of microdisplay tiles.

30. The method for assembling a plurality of microdisplay tiles as recited in claim 29, wherein said filling material applying step (d) results in substantially filling said at least one gap between at least two of said plurality of microdisplay tiles.

31. The method for assembling a plurality of microdisplay tiles as recited in claim 30, wherein said filling material comprises at least one from the group of epoxies, acrylics, silicones, and other polymeric materials.

32. The method for assembling a plurality of microdisplay tiles as recited in claim 31, wherein said filling material is filled with at least one from the group of diamond, boron nitride, silicon carbide, aluminum nitride, other ceramic materials, and glasses.

33. A method for fabricating microdisplay tiles for use in a tiled, flat-panel display, the projected image of which display having visually imperceptible seams, the steps comprising:

a) fabricating a plurality of microdisplays on a silicon wafer, said plurality of microdisplays having a seam region therebetween;

b) conforming said seam regions between said microdisplays to predetermined geometries to facilitate assembly of said microdisplays into said tiled, flat panel display; and

c) microseparating said microdisplays at predetermined points in said seam regions.

34. The method for fabricating microdisplay tiles for use in a tiled, flat-panel display as recited in claim 33, wherein said microseparating step (c) comprises etching.

35. The method for fabricating microdisplay tiles for use in a tiled, flat-panel display as recited in claim 34, wherein said etching step comprises the sub-step of one of the set of:

applying an etch mask to said silicon wafer, surface lithography, etching by anisotropic plasma, anisotropic wet etching, etching by reactive ion etching, and deep silicon etching.

36. The method for fabricating microdisplay tiles for use in a tiled, flat-panel display as recited in claim 35, wherein said deep silicon etch results in a etch substantially through said silicon wafer, resulting in said microseparating step (c) whereby said microdisplay tiles are separated one from another.

37. The method for fabricating microdisplay tiles for use in a tiled, flat-panel display as recited in claim 34, wherein said etching comprises a partial depth silicon etch.

38. The method for fabricating microdisplay tiles for use in a tiled, flat-panel display as recited in claim 37, wherein said microseparating step (c) comprises severing said microdisplays from one another in the region of said partial depth silicon etch.

39. The method for fabricating microdisplay tiles for use in a tiled, flat-panel display as recited in claim 34, wherein said silicon wafer comprises a crystalline silicon wafer having at least [1 0 0] and [1 1 1] crystalline planes, said planes determining the anisotropic wet etch rate.

40. The method for fabricating microdisplay tiles for use in a tiled, flat-panel display as recited in claim 34, wherein said etching results in a V-groove geometry in said seam region.

41. The method for fabricating microdisplay tiles for use in a tiled, flat-panel display as recited in claim 34, wherein said etching comprises a combination of back side and front side etches.

42. The method for fabricating microdisplay tiles for use in a tiled, flat-panel display as recited in claim 33, wherein said microseparating step (c) comprises a t least one from the group of cleaving, severing, edge finishing, sawing, scribing and breaking.

43. The method for fabricating microdisplay tiles for use in a tiled, flat-panel display as recited in claim 33, further comprising the step of:

placing a mask proximate one of the major surfaces of said LCD glass cover plate.

44. The method for fabricating microdisplay tiles for use in a tiled, flat-panel display as recited in claim 33, further comprising the step of:

placing a mask on said seam between said microdisplay tiles.

45. A method for assembling a plurality of microdisplay tiles into a tiled, flat-panel display, the projected image of said display having visually imperceptible seams, the steps comprising:

a) providing a plurality of monolithic microdisplay tiles, each microdisplay having a front, active face and a rear, mounting face;

b) arranging said plurality of microdisplay tiles with respect to one another;

c) bonding said plurality of microdisplay tiles to an optically flat carrier;

d) applying a filling material to said rear faces of said plurality of tiles; and

e) attaching a thermally-conductive, common substrate to said rear faces of said plurality of tiles.

46. The method for assembling a plurality of microdisplay tiles into a tiled, flat-panel display as recited in claim 45, wherein said attaching step (e) comprises the sub-step:

i) applying a thermally-conductive adhesive to at least one of said rear faces of said plurality of tiles and said substrate.

47. The method for assembling a plurality of microdisplay tiles into a tiled, flat-panel display as recited in claim 46, wherein said thermally-conductive adhesive comprises an adhesive material having thermally-conductive particles dispersed therein.

48. The method for assembling a plurality of microdisplay tiles into a tiled, flat-panel display as recited in claim 47, wherein said thermally-conductive particles comprise particles of at least one from the group of diamond, boron nitride, silicon carbide, aluminum nitride, other thermally-conductive ceramics, silver, copper, gold, tin, and solder.

49. The method for assembling a plurality of microdisplay tiles into a tiled, flat-panel display as recited in claim 48, wherein said thermally-conductive particles are spherically shaped.

50. The method for assembling a plurality of microdisplay tiles into a tiled, flat-panel display as recited in claim 45, wherein said attaching step (e) further comprises the sub-step:

ii) applying a conductive, metallic coating to at least one of said rear faces of said plurality of tiles and said substrate.

51. The method for assembling a plurality of microdisplay tiles into a tiled, flat-panel display as recited in claim 50, wherein said conductive, metallic coating comprises a thin coating of a least one metal from the group of silver, copper, indium, tin and solder.

52. The method for assembling a plurality of microdisplay tiles into a tiled, flat-panel display as recited in claim 51, wherein said applying sub-step (ii) comprises plating.

53. The method for assembling a plurality of microdisplay tiles into a tiled, flat-panel display as recited in claim 51, wherein said applying sub-step (ii) comprises sputtering.

54. The method for assembling a plurality of microdisplay tiles into a tiled, flat-panel display as recited in claim 51, wherein said applying sub-step (ii) comprises evaporation.

55. The method for assembling a plurality of microdisplay tiles into a tiled, flat-panel display as recited in claim 46, wherein said thermally-conductive, common substrate comprises a cooling structure.

56. The method for assembling a plurality of microdisplay tiles into a tiled, flat-panel display as recited in claim 55, wherein said cooling structure comprises a heat sink.

57. The method for assembling a plurality of microdisplay tiles into a tiled, flat-panel display as recited in claim 56, wherein said heat sink comprises fins.

58. The method for assembling a plurality of microdisplay tiles into a tiled, flat-panel display as recited in claim 55, wherein said cooling structure comprises channels for circulating a cooling fluid within said substrate.

59. The method for assembling a plurality of microdisplay tiles into a tiled, flat-panel display as recited in claim 55, wherein said cooling structure comprises thermoelectric cooling means.

60. The method for assembling a plurality of microdisplay tiles into a tiled, flat-panel display as recited in claim 55, wherein said cooling structure comprises a heat pipe.