Methods of fabricating interferometric modulators by selectively removing a material

• US 20060077502A1
• Filed: 03/25/2005
• Published: 04/13/2006
• Est. Priority Date: 09/27/2004
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: IDC, LLC
• Inventors: Cummings, William J., Kothari, Manish, Tung, Ming-Hau
• Granted Patent: US 7,429,334 B2
• Time in Patent Office: Days
• US Class Current: 359/237
• CPC Class Codes: B81B 2201/047 Optical MEMS not provided for in B81B2201/042 - B81B2201/045
• CPC Class Codes: B81B 2203/0181 See-saws
• CPC Class Codes: B81C 1/00174 See-saws
• CPC Class Codes: B81C 1/00182 Arrangements of deformable or non-deformable structures, e.g. membrane and cavity for use in a transducer
• CPC Class Codes: B81C 2201/0109 Sacrificial layers not provided for in B81C2201/0107 - B81C2201/0108
• 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

Methods for making MEMS devices such as interferometric modulators involve selectively removing a sacrificial portion of a material to form an internal cavity, leaving behind a remaining portion of the material to form a post structure. The material may be blanket deposited and selectively altered to define sacrificial portions that are selectively removable relative to the remaining portions. Alternatively, a material layer can be laterally recessed away from openings in a covering layer. These methods may be used to make unreleased and released interferometric modulators.

Claims

1. A method for making a MEMS device comprising:

depositing a material over a first electrode layer;

depositing a second layer over the material, the second layer comprising an opening formed therethrough, the opening being configured to expose the material;

flowing an etchant through the opening; and

etching the material to remove a sacrificial portion of the material to thereby form a cavity and a support structure of the MEMS device, the support structure comprising a remaining portion of the material, the etching being non-selective between the sacrificial portion and the remaining portion of the material.

2. The method of claim 1 in which the MEMS device comprises an interferometric modulator.

3. The method of claim 1 in which the material is selected from the group consisting of molybdenum and silicon.

4. The method of claim 1 in which the etching of the material is selective against the second layer.

5. The method of claim 1 in which the etching comprises laterally recessing the material away from the opening.

6. The method of claim 1 in which the etching is isotropic etching.

7. The method of claim 1 in which the etchant comprises XeF₂.

8. The method of claim 1 further comprising etching the second layer to form the opening.

9. The method of claim 1 in which the first electrode layer comprises a first mirror.

10. The method of claim 9 in which the second layer comprises a second electrode.

11. The method of claim 10 in which the second layer further comprises a second mirror.

12. The method of claim 1 in which the second layer comprises a mechanical layer.

13. The method of claim 12 further comprising depositing a mirror layer, at least a portion of which is suspended from the mechanical layer after etching to remove the sacrificial portion of the material.

14. The method of claim 13 in which the etching to remove the sacrificial portion is selective against the mirror layer.

15. The method of claim 13 in which the support structure has a re-entrant profile.

42. The method of claim 1 in which the etching comprises a timed etch.

43. The method of claim 1 in which the support structure comprises a post.

16. An unreleased MEMS substrate comprising an underlying material and an overlying layer,

the overlying layer being configured so that a sacrificial portion of the underlying material is removable to form a cavity;

and

the overlying layer being further configured so that a remaining portion of the underlying material forms a post structure of an interferometric modulator upon removal of the sacrificial portion, the remaining portion and the sacrificial portion having substantially uniform properties.

17. The unreleased MEMS substrate of claim 16 in which the material is selected from the group consisting of molybdenum and silicon.

18. The unreleased MEMS substrate of claim 16 in which the overlying layer comprises an aperture configured to expose the underlying material.

19. The unreleased MEMS substrate of claim 16 in which the overlying layer comprises a plurality of apertures configured in an array.

20. The unreleased MEMS substrate of claim 19 in which the apertures are selected from the group consisting of vias, trenches and channels.

21. The unreleased MEMS substrate of claim 16 in which the underlying material overlies a substrate, the substrate comprising an aperture configured to expose the underlying material.

22. The unreleased MEMS substrate of claim 16 in which the overlying layer comprises a mirror layer.

23. The unreleased MEMS substrate of claim 16 in which the overlying layer comprises an electrode.

24. The unreleased MEMS substrate of claim 16 in which the overlying layer comprises a mechanical layer.

25. The unreleased MEMS substrate of claim 16 further comprising a first mirror layer and a second mirror layer, at least a portion of the material being positioned between the first mirror layer and the second mirror layer.

26. The unreleased MEMS substrate of claim 25 in which the overlying layer comprises the second mirror layer.

27. The unreleased MEMS substrate of claim 25 in which at least a portion of the second mirror layer is suspended from the overlying layer upon removal of the sacrificial portion.

28. The unreleased MEMS substrate of claim 16 in which the post structure has a re-entrant profile.

29. A method for making an interferometric modulator, the interferometric modulator comprising at least a first mirror, a second mirror separated from the first mirror by a cavity, and a support structure positioned at a side of the cavity and configured to support the second mirror spaced from the first mirror, the method comprising:

providing a substrate, the substrate having a first area configured to underlie the first mirror and a second area configured to underlie the support structure;

depositing a first mirror layer over at least the first area;

depositing a material over the first area and over the second area;

depositing a second mirror layer over at least the material over the first area; and

forming a plurality of openings configured to facilitate flow of an etchant to the material over the first area;

the material over the first area being removable by the etchant to thereby form the cavity and the support structure, where the support structure comprises the material over the second area, the material having substantially uniform properties.

30. The method of claim 29 in which the material is selected from the group consisting of molybdenum and silicon.

31. The method of claim 30 further comprising removing at least a part of the material over the first area to thereby form the cavity.

32. The method of claim 31 wherein removing at least a part of the material over the first area to thereby form the cavity comprises a timed etch.

33. The method of claim 31 wherein removing at least a part of the material over the first area to thereby form the cavity comprises laterally recessing the material away from the plurality of openings.

34. The method of claim 32 in which the etchant comprises XeF₂.

35. The method of claim 29 in which the plurality of openings is formed through the second mirror layer.

36. The method of claim 29 further comprising forming a mechanical layer over at least the material over the first area.

37. The method of claim 29 in which the plurality of openings comprises a via.

38. The method of claim 29 in which the plurality of openings comprises a plurality of intersecting channels.

39. An interferometric modulator comprising a post structure, the post structure having a re-entrant profile.

40. The interferometric modulator of claim 39 in which the post structure has a generally concave cross-section.

41. The interferometric modulator of claim 39 in which the post structure has a generally convex cross-section.