Self assembled micro anti-stiction structure

• US 6,859,577 B2
• Filed: 06/25/2001
• Issued: 02/22/2005
• Est. Priority Date: 06/25/2001
• Status: Expired due to Term

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Lin, Chuang-Chia
• Primary Examiner(s): Prasad, Chandrika
• Application Number:
  US09/891,760
• Publication Number:
  US 20020197002A1
• Time in Patent Office: 1,338 Days
• Field of Search: 385/15, 385/18, 385/23, 385/24, 385/25, 385/83, 385/88, 385/94
• US Class Current: 385/18
• CPC Class Codes: B81B 2201/045 Optical switches
• CPC Class Codes: B81B 2203/058 Rotation out of a plane parallel to the substrate
• CPC Class Codes: B81B 3/0008 Structures for avoiding electrostatic attraction, e.g. avoiding charge accumulation
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means

Abstract

A method and apparatus are described for reducing stiction in a MEMS device having a movable element and a substrate. The method generally comprises providing the substrate with an anti-stiction member and interposing the anti-stiction member between the moveable element and the substrate. The apparatus generally comprises an anti-stiction member that is interposable between the moveable element and the substrate. Another embodiment of the invention of the invention is directed to a MEMS device, comprising: a substrate, a moveable element moveably coupled to the substrate, and an anti-stiction member that is interposable between the moveable element and the substrate. A further embodiment of the invention is directed to an optical switch having one or more moveable elements moveably coupled to a substrate, and an anti-stiction member that is interposable between at least one of the moveable elements and the substrate. The anti-stiction member may be in the form of a flexible cantilevered structure that overhangs the moveable element. Actuating the moveable element causes the anti-stiction member to flex and snap into place between the moveable element and the substrate. An additional embodiment of the invention is directed to a method of fabricating a MEMS device. The method proceeds by providing a silicon-on-insulator (SOI) substrate; defining a moveable element from a device layer of the SOI substrate; and depositing a flexible material over the device layer and the moveable element. One or more portions of the flexible material overhang the moveable element, whereby the flexible material forms one or more anti-stiction members.

Claims

1. A method for reducing suction in a MEMS device having a moveable element moveably coupled to a substrate, the method comprising:

a) providing the substrate with an anti-stiction member; and

b) interposing the anti-stiction member between the moveable element and the substrate,

wherein step b) includes actuating the moveable element to interpose the anti-stiction member between the moveable element and the substrate.

2. The method of claim 1 wherein step b) includes substantially immersing the moveable element in a liquid during actuation of the moveable element.

3. A method for reducing stiction in a MEMS device having a moveable element moveably coupled to a substrate, the method comprising:

a) providing the substrate with an anti-stiction member; and

b) interposing the anti-stiction member between the moveable element and the substrate,

wherein step a) includes providing an anti-stiction member that overhangs the moveable element.

4. The method of claim 3, wherein the anti-stiction member includes one or more flexible portions.

5. The method of claim 4, wherein the one or more flexible portions includes at least one double-serpentine portion.

6. The method of claim 3 wherein the anti-stiction member is made of a flexible material.

7. The method of claim 3 wherein step b) includes actuating the moveable element whereby the moveable element engages the anti-stiction member causing the anti-stiction member to flex.

8. The method of claim 7 wherein step b) includes flexing the anti-stiction member sufficiently to interpose the anti-stiction member between the moveable element and the substrate.

9. A method for reducing stiction in a MEMS device having a moveable element moveably coupled to a substrate, the method comprising:

a) providing the substrate with an anti-stiction member; and

b) interposing the anti-stiction member between the moveable element and the substrate,

wherein step a) includes;

providing a silicon-on-insulator (SOI) substrate;

forming the moveable element from a device layer of the SOI substrate; and

depositing a flexible material over the device layer and the moveable element such that the flexible material overhangs the moveable element.

10. An apparatus for reducing stiction in a MEMS device having a moveable element moveably coupled to a substrate, the apparatus comprising:

an anti-stiction member that is interposable between the moveable element and the substrate,

wherein the anti-stiction member is attached to the substrate, wherein the anti-stiction member is not attached to the moveable element, wherein the anti-stiction member is cantilevered such that the anti-stiction member overhangs the moveable element.

11. An apparatus for reducing stiction in a MEMS device having a moveable element moveably coupled to a substrate, the apparatus comprising:

an anti-stiction member that is interposable between the moveable element and the substrate,

wherein the anti-stiction member is attached to the substrate, wherein the anti-stiction member is not attached to the moveable element, wherein the anti-stiction member is made from a flexible material.

12. An apparatus for reducing stiction in a MEMS device having a moveable element moveably coupled to a substrate, the apparatus comprising:

an anti-stiction member that is interposable between the moveable element and the substrate,

wherein the anti-stiction member is attached to the substrate, wherein the anti-stiction member is not attached to the moveable element, wherein the anti-stiction member includes one or more flexible portions disposed between a fixed end and a free end of the anti-stiction member.

13. The apparatus of claim 12 wherein the one or more flexible portions include at least one serpentine portion.

14. The apparatus of claim 12 wherein the one or more flexible portions include at least one double serpentine portion.

15. An apparatus for reducing stiction in a MEMS device having a moveable element moveably coupled to a substrate, the apparatus comprising:

an anti-stiction member that is interposable between the moveable element and the substrate,

wherein the anti-stiction member is attached to the substrate, wherein the anti-stiction member is not attached to the moveable element, further comprising a standoff attached to a free end of the anti-stiction member.

16. An apparatus for reducing stiction in a MEMS device having a moveable element moveably coupled to a substrate, the apparatus comprising:

an anti-stiction member that is interposable between the moveable element and the substrate,

wherein the anti-stiction member is attached to the substrate, wherein the anti-stiction member is not attached to the moveable element,

further comprising means for electrically isolating the moveable element from a portion of the substrate, wherein the means for electrically isolating includes an electrically insulating standoff attached to a free end of the anti-stiction member.

17. An apparatus for reducing stiction in a MEMS device having a moveable element moveably coupled to a substrate, the apparatus comprising:

an anti-stiction member that is interposable between the moveable element and the substrate,

wherein the anti-stiction member is attached to the substrate, wherein the anti-stiction member is not attached to the moveable element,

further comprising means for electrically isolating the moveable element from a portion of the substrate, wherein the anti-stiction member includes a serpentine shaped portion that is disposed between a free end and a fixed end of the anti-stiction member.

18. An apparatus for reducing stiction in a MEMS device having a moveable element moveably coupled to a substrate, the apparatus comprising:

an anti-stiction member that is interposable between the moveable element and the substrate,

wherein the anti-stiction member is attached to the substrate, wherein the anti-stiction member is not attached to the moveable element,

further comprising means for electrically isolating the moveable element from a portion of the substrate, wherein the anti-stiction member includes one or more double-serpentine shaped portions that are disposed between a free end and a fixed end of the anti-stiction member.

19. A MEMS device, comprising:

a substrate;

a moveable element moveably coupled to the substrate, and

an anti-stiction member that is interposable between the moveable element and the substrate,

wherein the anti-stiction member is cantilevered such that the anti-stiction member overhangs the moveable element.

20. A MEMS device, comprising:

a substrate;

a moveable element moveably coupled to the substrate, and

an anti-stiction member that is interposable between the moveable element and the substrate,

wherein the anti-stiction member is made from a flexible material.

21. A MEMS device, comprising:

a substrate;

a moveable element moveably coupled to the substrate, and

an anti-stiction member that is interposable between the moveable element and the substrate,

wherein the anti-stiction member includes one or more flexible portions disposed between a fixed end and a free end of the anti-stiction member.

22. The MEMS device of claim 21, wherein the one or more flexible portions include a serpentine portion.

23. The MEMS device of claim 21, wherein the one or more flexible portions include at least one double-serpentine portion.

24. A MEMS device, comprising:

a substrate;

a moveable element moveably coupled to the substrate, and

an anti-stiction member that is interposable between the moveable element and the substrate,

further comprising a standoff attached to a free end of the anti-stiction member.

25. A MEMS device, comprising:

a substrate;

a moveable element moveably coupled to the substrate, and

an anti-stiction member that is interposable between the moveable element and the substrate, further comprising means for electrically isolating the moveable element from a portion of the substrate, wherein the means for electrically isolating includes an electrically insulating standoff attached to a free end of the anti-stiction member.

26. The MEMS device of claim 25, wherein the means for electrically isolating includes an electrically insulating portion of the moveable element.

27. A method for fabricating a MEMS device, comprising:

providing a silicon-on-insulator (SOI) substrate;

forming a moveable element from a device layer of the SOI substrate;

forming a sacrificial layer over the moveable element and a portion of the device layer and

depositing a flexible material over the sacrificial layer, the device layer and the moveable element such that one or more portions of the flexible material overhang the moveable element to form an anti-stiction member,

wherein the flexible material is deposited such that the anti-stiction member is attached to one end to a portion of the device layer,

wherein the flexible material is deposited such that the anti-stiction member is not attached to the moveable element; and

etching the sacrificial layer to release the moveable element,

whereby the flexible material forms one or more anti-stiction members.

28. The method of claim 27, wherein the flexible material is resistant to an etchant that is used to remove the sacrificial layer.

29. An optical switch, comprising:

a substrate;

one or more moveable elements moveably coupled to the substrate, and

an anti-stiction member that is interposable between at least one of the moveable elements and the substrate, wherein the anti-stiction member is cantilevered such that the anti-stiction member overhangs the moveable element.

30. An optical switch, comprising:

a substrate;

one or more moveable elements moveably coupled to the substrate, and

an anti-stiction member that is interposable between at least one of the moveable elements and the substrate, wherein the anti-stiction member is made from a flexible material.

31. An optical switch, comprising:

a substrate;

one or more moveable elements moveably coupled to the substrate, and

an anti-stiction member that is interposable between at least one of the moveable elements and the substrate, wherein the anti-stiction member includes one or more flexible portions disposed between a fixed end and a free end of the anti-stiction member.

32. The optical switch of claim 31, wherein the flexible portion includes a serpentine portion.

33. The optical switch of claim 31, wherein the flexible portion includes at least one double serpentine portion.

34. An optical switch, comprising:

a substrate;

one or more moveable elements moveably coupled to the substrate, and

an anti-stiction member that is interposable between at least one of the moveable elements and the substrate, further comprising a standoff attached to a free end of the anti-stiction member.