Alignment methods in fluid-filled MEMS displays

• US 20080037104A1
• Filed: 10/19/2007
• Published: 02/14/2008
• Est. Priority Date: 02/23/2005
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Pixtronix, Incorporated (Qualcomm, Inc.)
• Inventors: Fijol, John, Steyn, Jasper, Hagood, Nesbitt, Payne, Richard, Gandhi, Jignesh
• Granted Patent: US 9,229,222 B2
• Time in Patent Office: Days
• US Class Current: 359/292
• CPC Class Codes: B81B 2201/047 Optical MEMS not provided for in B81B2201/042 - B81B2201/045
• CPC Class Codes: B81B 2203/0315 Cavities
• CPC Class Codes: B81C 2203/0118 Bonding a wafer on the substrate, i.e. where the cap consists of another wafer
• CPC Class Codes: B81C 2203/019 characterised by the material or arrangement of seals between parts
• CPC Class Codes: B81C 2203/051 Active alignment, e.g. using internal or external actuators, magnets, sensors, marks or marks detectors
• CPC Class Codes: B81C 3/004 Active alignment, i.e. moving the elements in response to the detected position of the elements using internal or external actuators
• CPC Class Codes: G02B 26/00 Optical devices or arrangements for the control of light using movable or deformable optical elements control of light by modification of the optical properties of the media of the elements involved therein G02F1/00
• CPC Class Codes: G02B 26/023 comprising movable attenuating elements, e.g. neutral density filters
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G09G 2300/023 Display panel composed of stacked panels
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2300/0443 with several sub-pixels for the same colour in a pixel, not specifically used to display gradations G09G3/364 takes precedence
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 3/3433 using light modulating elements actuated by an electric field and being other than liquid crystal devices and electrochromic devices using liquid crystal devices G09G3/36; using electrochromic devices G09G3/38
• CPC Class Codes: G09G 3/3473 based on light coupled out of a light guide, e.g. due to scattering, by contracting the light guide with external means
• CPC Class Codes: H01L 2924/1461 MEMS

Abstract

This invention relates to MEMS display apparatus and methods for assembly thereof that include a plurality of light modulators having components substantially surrounded in a liquid that reduces the effects of stiction and improves the optical and electromechanical performance of the display apparatus. The invention also relates to methods for aligning components of a MEMS display to establish a correspondence between the plurality of light modulators and a plurality of apertures to regulate the transmission of light through the apparatus.

Claims

1. A method of manufacturing a display assembly comprising:

providing a first substrate on which a plurality of MEMS light modulators has been fabricated, wherein each MEMS light modulator has a light state and a dark state;

providing a second transparent substrate including a layer formed thereon that includes a plurality of apertures; and

aligning the first substrate with the second transparent substrate to establish a correspondence between respective MEMS light modulators and apertures.

2. The method of claim 1 wherein each MEMS light modulator includes a modulation element having an edge and each aperture includes at least one edge;

and

wherein aligning the first and second substrates comprises aligning the first substrate with the second substrate such that in the dark state, the edge of a modulation element of a MEMS light modulator overlaps the edge of a corresponding aperture by more than 0 microns and by less than about 20 microns.

3. The method of claim 2 wherein the first substrate is substantially transparent.

4. The method of claim 2 comprising maintaining the alignment by bonding the first substrate to the second substrate with an adhesive.

5. The method of claim 2 comprising maintaining alignment by coupling the first substrate to the second substrate with a mechanically interlocking feature.

6. The method of claim 2 comprising maintaining the alignment by coupling the first substrate to the second substrate with a heat reflowable material.

7. The method of claim 2 wherein the plurality of MEMS light modulators on the first substrate includes a plurality of arrays of light modulators, and the plurality of apertures on the second substrates includes a plurality of arrays of apertures, the method comprising singulating the first and second substrates.

8. The method of claim 7 wherein the first and second substrates are singulated prior to their alignment.

9. The method of claim 7 wherein the first and second substrates are singulated subsequent to their alignment.

10. The method of claim 2 comprising forming alignment marks on the first and second substrates.

11. The method of claim 10 wherein aligning the first and second substrates comprises loading the first and second substrates into an alignment apparatus that includes a vision system for monitoring a degree of misalignment between alignment marks.

12. The method of claim 11 wherein the alignment apparatus comprises motors for adjusting the relative positions of the two substrates.

13. The method of claim 11 wherein the alignment apparatus comprises UV lamps for the curing of an adhesive material.

14. The method of claim 2 comprising applying spacers for establishing a fixed separation distance between the first and second substrates.

15. The method of claim 1 wherein in the light state, a light modulator locally frustrates total internal reflection of light reflecting in one of the first and second substrates.

16. The method of claim 1 wherein the light modulators are electrowetting modulators.

17. The method of claim 1 wherein the layer formed on the second substrate comprises a reflective material.

18. The method of claim 1 wherein the layer formed on the second substrate comprises a light absorbing material.

19. The method of claim 2 wherein in the dark state the edge of a modulation element of a MEMS light modulator overlaps the edges of a corresponding apertures by more than 0 microns and by less than about 5 microns.

20. The method of claim 1 comprising applying a conductive material which bridges the gap between the first and second transparent substrates.

21. A display assembly comprising:

an array of MEMS light modulators formed on a first substrate;

a second, transparent substrate separated from the first substrate by a gap;

a liquid disposed between the first and second substrates substantially surrounding a movable portion of the MEMS light modulators; and

an adhesive seal surrounding the array of MEMS modulators to contain the liquid between the two substrates and to restrict relative motion between the two substrates.

22. The display assembly of claim 21 wherein the liquid comprises a lubricant.

23. The display assembly of claim 21 comprising a reflective aperture layer disposed on one of the first and second substrates.

24. The display apparatus of claim 23 wherein the liquid has a first index of refraction and the substrate on which the reflective aperture layer is disposed has a second index of refraction, and wherein the first index of refraction is greater than or substantially equal to that of the second index of refraction.

25. The display assembly of claim 21, wherein the liquid is non-conductive.

26. The display assembly of claim 21 wherein the liquid has a dielectric constant greater than 2.0.

27. The display assembly of claim 21 wherein the liquid wets the surface of the MEMS modulators in the array of MEMS modulators.

28. The display assembly of claim 27 wherein each of the MEMS light modulators includes a front side and a rear side, and wherein the liquid wets both the front and rear sides of the MEMS light modulators.

29. The display assembly of claim 21 wherein the adhesive seal comprises a polymer material.

30. The display assembly of claim 21 wherein each of the MEMS light modulators includes a component that is controllably moved through the liquid.

31. The display assembly of claim 21 wherein the liquid consists of a single liquid.