Method of manufacturing MEMS devices providing air gap control

• US 7,527,998 B2
• Filed: 06/30/2006
• Issued: 05/05/2009
• Est. Priority Date: 06/30/2006
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Kogut, Lior, Tung, Ming-Hau
• Primary Examiner(s): Nguyen; Ha Tran T
• Assistant Examiner(s): WHALEN, DANIEL B
• Application Number:
  US11/478,702
• Publication Number:
  US 20080003737A1
• Time in Patent Office: 1,040 Days
• Field of Search: 345 84- 86, 353/94, 353/99, 353/122, 359/223, 359/224, 359290-292, 359/295, 359/298, 438 48- 53, 257/414, 257/415
• US Class Current: 438/53
• CPC Class Codes: B81B 2201/042 Micromirrors, not used as optical switches
• 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 1/00047 Cavities
• CPC Class Codes: B81C 2201/0167 by adding further layers of materials having complementary strains, i.e. compressive or tensile strain

Abstract

Methods and apparatus are provided for controlling a depth of a cavity between two layers of a light modulating device. A method of making a light modulating device includes providing a substrate, forming a sacrificial layer over at least a portion of the substrate, forming a reflective layer over at least a portion of the sacrificial layer, and forming one or more flexure controllers over the substrate, the flexure controllers configured so as to operably support the reflective layer and to form cavities, upon removal of the sacrificial layer, of a depth measurably different than the thickness of the sacrificial layer, wherein the depth is measured perpendicular to the substrate.

Claims

1. A method of making at least two types of microelectromechanical systems (MEMS) devices, the at least two types of MEMS devices having different release states after removal of sacrificial material, the method comprising:

providing a substrate;

forming a first electrically conductive layer over at least a portion of the substrate;

forming a first sacrificial layer over at least a portion of the first conductive layer;

forming a plurality of electrically conductive moveable elements over the first sacrificial layer; and

forming a plurality of flexure controllers over the substrate configured so as to operably support the electrically conductive moveable elements after the sacrificial layer is removed, wherein at least a portion of at least one flexure controller of the plurality of flexure controllers is overlying and operably supporting at least one movable element of the plurality of electrically conductive movable elements;

the first sacrificial layer being removable to thereby release the MEMS devices and form a plurality of cavities of different depths between the first electrically conductive layer and the movable elements.

2. The method of claim 1, further comprising forming a dielectric layer over the first conductive layer.

3. The method of claim 1, wherein the thickness of the first sacrificial layer is substantially the same under the plurality of electrically conductive moveable elements.

4. The method of claim 1, further comprising:

forming a second sacrificial layer over the moveable elements; and

forming a mechanical layer over at least a portion of the second sacrificial layer, wherein the mechanical layer is attached to the moveable elements and is operably supported by the plurality of flexure controllers;

the second sacrificial layer being removable to thereby form the plurality of cavities and release the MEMS devices.

5. The method of claim 4, wherein the flexure controllers comprise at least one of post structures and rivet structures.

6. The method of claim 4, wherein forming the flexure controllers further comprises forming at least two types of flexure controllers with different sized members contacting the mechanical layer.

7. The method of claim 6, wherein the different sized members comprise different sized wings of post structures or rivet structures, wherein the wings run substantially parallel to the substrate and the electrically conductive movable elements.

8. The method of claim 1, further comprising removing substantially all of the first sacrificial layer thereby releasing the MEMS devices.

9. The method of claim 8, wherein the first sacrificial layer comprises one of molybdenum and amorphous silicon and removing the first sacrificial layer comprises exposing the first sacrificial layer to vapors derived from solid xenon difluoride.

10. The method of claim 1, wherein the flexure controllers comprise at least one of post structures and rivet structures.

11. The method of claim 1, wherein forming the flexure controllers further comprises forming at least two types of flexure controllers with different sized members contacting the moveable elements.

12. The method of claim 11, wherein the different sized members comprise different sized wings of post structures or rivet structures, wherein the wings run substantially parallel to the substrate and the electrically conductive movable elements.

13. A method of making at least two types of interferometric modulators, the at least two types of interferometric modulators having different cavity depths after removal of a sacrificial material, the method comprising:

providing a substrate;

forming an optical stack over at least a portion of the substrate;

forming a sacrificial material over at least a portion of the optical stack, wherein the sacrificial material is removable to thereby form a plurality of cavities;

forming an electrically conductive layer over portions of the sacrificial material; and

forming at least two types of flexure controllers over the substrate, the flexure controllers configured so as to operably support the electrically conductive layer, wherein the at least two types of flexure controllers comprise different sized components, the different sized components configured to form the plurality of cavities of different depths under the portions of the electrically conductive layer after removal of the sacrificial layer, wherein at least a portion of at least one of the flexure controllers is overlying and operably supporting at least a portion of the electrically conductive layer.

14. The method of claim 13, further comprising removing substantially all of the sacrificial material.

15. A method of controlling a depth of a cavity between two layers of a device comprising one or more film layers, the method comprising:

providing a substrate;

forming a sacrificial layer over at least a portion of the substrate;

forming a first layer over at least a portion of the sacrificial layer; and

forming one or more flexure controllers over the substrate, the one or more flexure controllers having one or more wing portions extending substantially parallel to the substrate and the first layer, the flexure controllers configured so as to operably support the first layer and to form a cavity between the substrate and the first layer, wherein the wing portions are dimensioned such that, after removal of the sacrificial layer, the cavity has a depth of about 30 percent greater or more than the depth of the sacrificial layer, wherein depth is measured perpendicular to the substrate, wherein at least a portion of at least one of the flexure controllers is overlying and operably supporting at least a portion of the first layer.

16. The method of claim 15, wherein the flexure controllers comprise at least one of post structures and rivet structures.

17. The method of claim 16, wherein the flexure controllers comprise one or more post structures and one or more rivet structures, wherein the one or more post structures and the one or more rivet structures comprise different sized wings.

18. The method of claim 15, wherein the first layer is a movable layer.

19. A method of controlling a depth of a cavity between two layers of a device comprising one or more film layers, the method comprising:

providing a substrate;

forming a sacrificial layer over at least a portion of the substrate, the sacrificial layer being removable by etching;

forming a film layer over at least a portion of the sacrificial layer; and

forming one or more flexure controllers over the substrate, the one or more flexure controllers having one or more wings extending substantially parallel to the substrate, the flexure controllers configured so as to operably support the film layer and wherein the wings are dimensioned so as to displace the film layer towards the substrate, after removal of the sacrificial layer, wherein at least a portion of at least one of the flexure controllers is overlying and operably supporting at least a portion of the film layer.