Method of manufacturing MEMS devices providing air gap control

• US 20080003737A1
• Filed: 06/30/2006
• Published: 01/03/2008
• 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
• Granted Patent: US 7,527,998 B2
• Time in Patent Office: Days
• US Class Current: 438/202
• 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 microelecromechanical 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 when the sacrificial layer is removed;

the first sacrificial layer being removable to thereby release the MEMS devices and form cavities having at least two gap sizes 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 a cavity and release the MEMS devices.

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

6. The method of claim 5, 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.

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

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

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

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

11. The method of claim 8, 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.

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

forming a second electrically conductive layer over portions of the first sacrificial material; and

forming at least two types of flexure controllers over the substrate, the flexure controllers configured so as to operably support the second electrically conductive layer, wherein the at least two types of flexure controllers comprise different sized components, the different sized components configured to form cavities of different depths under the portions of the second electrically conductive layer after removal of the first sacrificial layer.

13. An unreleased interferometric modulator made by the method of claim 12.

14. The method of claim 12, further comprising removing substantially all of the first sacrificial layer.

15. A released interferometric modulator made by the method of claim 14.

16. An array of interferometric modulators comprising the released interferometric modulator of claim 15.

17. A display device, comprising:

an array of interferometric modulators as claimed in claim 16;

a processor that is configured to communicate with the array, the processor being configured to process image data; and

a memory device that is configured to communicate with the processor.

18. The display device of claim 17, further comprising a driver circuit configured to send at least one command to the array of interferometric modulators.

19. The display device of claim 17, further comprising a controller configured to send at least a portion of the image data to the driver circuit.

20. The display device of claim 17, further comprising an image source module configured to send the image data to the processor.

21. The display device of claim 20, wherein the image source module comprises at least one of a receiver, transceiver and transmitter.

22. The display device of claim 17, further comprising an input device configured to receive input data and to communicate the input data to the processor.

23. A microelecromechanical system (MEMS) device, comprising:

a substrate;

a plurality of moveable elements over the substrate, each moveable element separated from the substrate by a cavity; and

a plurality of flexure controllers over the substrate configured so as to operably support the moveable elements, wherein the plurality of flexure controllers comprise portions of different dimensions to control selected flexures;

wherein the selected flexures serve to form the cavities having at least two gap sizes between the substrate and the plurality of movable elements.

24. The MEMS device of claim 23, wherein the portions of different dimensions of the flexure controllers comprises different thicknesses of the plurality of flexure controllers.

25. 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 flexure controllers configured so as to operably support the first layer and to form a cavity between the substrate and the first layer, upon removal of the sacrificial layer, of a depth about 30 percent greater or more than the depth of the sacrificial layer, wherein depth is measured perpendicular to the substrate.

26. The method of claim 25, wherein the flexure controllers comprise at least one of post structures and rivet structures.

27. The method of claim 26, wherein the flexure controllers comprise one or more post structures and one or more rivet structures, wherein the post structure and the rivet structure comprise different sized wings, wherein the wings run substantially parallel to the substrate and the first layer.

28. The method of claim 25, wherein the first layer is a movable layer.

29. An unreleased microelecromechanical system (MEMS) device, comprising:

a substrate;

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

a moveable element over the first sacrificial layer; and

one or more flexure controllers over the substrate configured so as to operably support the moveable element and to form a cavity between the substrate and the movable element, upon removal of the sacrificial layer, of a depth about 30 percent greater or more than the depth of the sacrificial layer, wherein depth is measured perpendicular to the substrate;

the sacrificial layer being removable by etching.

30. The MEMS device of claim 29, wherein the one or more flexure controllers comprise one or more post structures and one or more rivet structures, wherein the post structure and the rivet structure comprise different sized members contacting the movable element.

31. The MEMS device of claim 29, wherein the one or more flexure controllers are formed with tensile or compressive stresses, wherein the combined stresses of the flexure controllers cause a deflection of the movable element upon removal of the sacrificial layer, thereby forming the cavity of the depth about 30 percent greater or more than the depth of the sacrificial layer.

32. An unreleased interferometric modulator, comprising:

first means for reflecting light;

second means for reflecting light;

first means for supporting the second reflecting means, wherein the first supporting means is removable by etching; and

second means for supporting the second reflecting means and for forming a cavity between the first reflecting means and the second reflecting means, upon removal of the first supporting means, of a depth about 30 percent greater or more than the depth of the first supporting means, wherein depth is measured perpendicular to the first reflecting means.

33. The unreleased interferometric modulator of claim 32, wherein the first reflecting means comprises a partially reflective layer.

34. The unreleased interferometric modulator of claim 32, wherein the second reflecting means comprises a movable reflective layer.

35. The unreleased interferometric modulator of claim 32, wherein the first supporting means comprises a sacrificial layer.

36. The unreleased interferometric modulator of claim 32, wherein the second supporting means comprises at least one of a post structure and a rivet structure.

37. 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 first film 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 first film layer and to displace the first film layer towards the substrate, upon removal of the sacrificial layer.

38. An unreleased microelecromechanical system (MEMS) device, comprising:

a substrate;

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

a moveable element over the first sacrificial layer; and

one or more flexure controllers over the substrate configured so as to operably support the moveable element and to displace the movable element towards the substrate, upon removal of the sacrificial layer;

the sacrificial layer being removable by etching.

39. An unreleased interferometric modulator, comprising:

first means for reflecting light;

second means for reflecting light;

first means for supporting the second reflecting means; and

second means for supporting the second reflecting means and for effecting a displacement of the second reflecting means towards the first reflecting means upon removal of the first supporting means;

wherein the first supporting means is removable by etching.

40. The unreleased interferometric modulator of claim 39, wherein the first reflecting means comprises a partially reflective layer.

41. The unreleased interferometric modulator of claim 39, wherein the second reflecting means comprises a movable reflective layer.

42. The unreleased interferometric modulator of claim 39, wherein the first supporting means comprises a sacrificial layer.

43. The unreleased interferometric modulator of claim 39, wherein the second supporting means comprises at least one of a post structure and a rivet structure.