MEMS DEVICES WITH MULTI-COMPONENT SACRIFICIAL LAYERS

• US 20100165442A1
• Filed: 03/08/2010
• Published: 07/01/2010
• Est. Priority Date: 03/02/2006
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Kogut, Lior, Tung, Ming-Hau
• Granted Patent: US 7,952,789 B2
• Time in Patent Office: Days
• US Class Current: 359/290
• CPC Class Codes: B81B 2201/042 Micromirrors, not used as optical switches
• CPC Class Codes: B81B 3/001 Structures having a reduced contact area, e.g. with bumps or with a textured surface
• CPC Class Codes: B81B 3/0072 For controlling internal stress or strain in moving or flexible elements, e.g. stress compensating layers
• CPC Class Codes: B81C 1/00801 Avoid alteration of functional structures by etching, e.g. using a passivation layer or an etch stop layer B81C1/00595, B81C1/00468 take precedence
• CPC Class Codes: B81C 2201/0109 Sacrificial layers not provided for in B81C2201/0107 - B81C2201/0108
• CPC Class Codes: B81C 2201/017 Methods for controlling internal stress of deposited layers not provided for in B81C2201/0164 - B81C2201/0169
• CPC Class Codes: B81C 2201/112 Depositing an anti-stiction or passivation coating, e.g. on the elastic or moving parts
• CPC Class Codes: B81C 2201/115 Roughening a surface
• 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 428/30 Self-sustaining carbon mass or layer with impregnant or other layer
• CPC Class Codes: Y10T 428/31678 Of metal
• CPC Class Codes: Y10T 428/31935 Ester, halide or nitrile of addition polymer

Abstract

Methods of forming a protective coating on one or more surfaces of a microelectromechanical device are disclosed comprising the steps of forming a composite layer of a sacrificial material and a protective material, and selectively etching the sacrificial material to form a protective coating. The protective coatings of the invention preferably improve one or more aspects of the performance of the microelectromechanical devices in which they are incorporated. Also disclosed are microelectromechanical devices formed by methods of the invention, and visual display devices incorporating such devices.

Claims

1. A pre-release structure for forming an electromechanical device, the pre-release structure comprising:

a substrate;

a mirror layer positioned over the substrate;

a partially transparent layer positioned over the substrate and spaced from the mirror layer; and

a composite layer disposed between the mirror and the partially transparent layer, the composite layer comprising a mixture of a sacrificial material and a protective material, the sacrificial material being selectively removable relative to the protective material.

2. The pre-release structure of claim 1, wherein the electromechanical device is an interferometric modulator.

3. The pre-release structure of claim 1, wherein the mirror layer is at least partially reflective to incident light upon removal of the sacrificial material.

4. The pre-release structure of claim 1, wherein the partially transparent layer is at least partially transmissive to incident light upon removal of the sacrificial material.

5. The pre-release structure of claim 2, wherein the protective material is configured to affect an optical property of an optically active surface of the interferometric modulator upon removal of the sacrificial material.

6. The pre-release structure of claim 5, wherein the partially transparent layer comprises the optically active surface.

7. The pre-release structure of claim 5, wherein the mirror layer comprises the optically active surface.

8. The pre-release structure of claim 5, wherein the optical property being affected comprises an ability of the optically active surface to reflect, absorb, scatter, and/or transmit a particular wavelength of light.

9. The pre-release structure of claim 5, wherein the protective material comprises a composition selected from the group consisting of Al₂O₃, Si₃N₄, SiO₂, ZrO₂, PbO₂, tantalum pentoxide, diamond, and a diamond-like material.

10. The pre-release structure of claim 9, wherein the protective material comprises the diamond-like material, wherein the diamond-like material is selected from the group consisting of diamond-like carbon (DLC), amorphous carbon (α

-C), cubic boron nitride (CBN), and combinations thereof.

11. The pre-release structure of claim 1, wherein the protective material is configured to form a metal film upon removal of the sacrificial material.

12. The pre-release structure of claim 11, wherein the protective material comprises a composition selected from the group consisting of Cr, W, and Au.

13. The pre-release structure of claim 1, wherein the protective material is configured to reduce stiction between two or more components of the electromechanical device upon removal of the sacrificial material.

14. The pre-release structure of claim 13, wherein the protective material comprises a composition selected from the group consisting of a polymer, diamond, a diamond-like material, and polymethylmethacrylate (PMMA).

15. The pre-release structure of claim 14, wherein the protective material comprises the diamond-like material, wherein the diamond-like material is selected from the group consisting of diamond-like carbon (DLC), amorphous carbon (α

-C), cubic boron nitride (CBN), and combinations thereof.

16. The pre-release structure of claim 14, wherein the protective material comprises the polymer, wherein the polymer is a hydrophobic polymer.

17. The pre-release structure of claim 2, wherein a surface energy of the protective material is lower than a surface energy of at least one surface of the interferometric modulator upon removal of the sacrificial material.

18. The pre-release structure of claim 1, wherein the protective material is configured to dissipate an electrical charge between two or more components of the electromechanical device upon removal of the sacrificial material.

19. The pre-release structure of claim 18, wherein the protective material comprises a composition selected from the group consisting of Si₃N₄, Al₂O₃, and SiO₂.

20. The pre-release structure of claim 1, wherein the protective material is configured to electrically insulate one or more surfaces of the electromechanical device upon removal of the sacrificial material.

21. The pre-release structure of claim 1, wherein the protective material is configured to thermally insulate one or more surfaces of the electromechanical device upon removal of the sacrificial material.

22. The pre-release structure of claim 1, wherein the protective material is configured to protect one or more surfaces of the electromechanical device against corrosion, erosion, and wear upon removal of the sacrificial material.

23. The pre-release structure of claim 1, wherein the protective material is substantially hydrophobic.

24. An apparatus comprising a plurality of the pre-release structures of claim 1.

25. A pre-release structure for forming an electromechanical device, the pre-release structure comprising:

a substrate;

a mirror layer positioned over the substrate;

a partially transparent layer positioned over the substrate and spaced from the mirror layer;

a first sacrificial layer positioned over the partially transparent layer; and

a second sacrificial layer positioned over the first sacrificial layer, at least one of the first and second sacrificial layers comprising a composite layer, the composite layer comprising a mixture of a sacrificial material and a protective material, the sacrificial material being selectively removable relative to the protective material.

26. The pre-release structure of claim 25, wherein at least a portion of the second sacrificial layer is positioned on the first sacrificial layer.

27. The pre-release structure of claim 25, wherein at least a portion of the second sacrificial layer is positioned over the mirror layer.

28. The pre-release structure of claim 25, wherein the mirror layer is configured to be movable relative to the partially transparent layer upon removal of the first and second sacrificial layers.

29. The pre-release structure of claim 25, further comprising a support member configured to support the minor layer over the substrate upon removal of the first and second sacrificial layers.

30. The pre-release structure of claim 25, wherein the protective material is configured to inhibit stiction between a surface of the minor layer and a surface of the partially transmissive layer upon removal of the first and second sacrificial layers.

31. The pre-release structure of claim 25, wherein the protective material comprises a composition selected from the group consisting of a polymer, diamond, a diamond-like material, and polymethylmethacrylate (PMMA).