Non-planar surface structures and process for microelectromechanical systems

• US 20070249079A1
• Filed: 04/19/2006
• Published: 10/25/2007
• Est. Priority Date: 04/19/2006
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Kogut, Lior, Sasagawa, Teruo, Tung, Ming-Hau
• Granted Patent: US 7,623,287 B2
• Time in Patent Office: Days
• US Class Current: 438/48
• CPC Class Codes: B81B 3/0008 Structures for avoiding electrostatic attraction, e.g. avoiding charge accumulation
• 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 of making MEMS devices including interferometric modulators involve depositing various layers, including stationary layers, movable layers and sacrificial layers, on a substrate. A non-planar surface is formed on one or more layers by flowing an etchant through a permeable layer. In one embodiment the non-planar surface is formed on a sacrificial layer. A movable layer formed over the non-planar surface of the sacrificial layer results in a non-planar interface between the sacrificial and movable layers. Removal of the sacrificial layer results in a released MEMS device having reduced contact area between the movable and stationary layers when the MEMS device is actuated. The reduced contact area results in lower adhesion forces and reduced stiction during actuation of the MEMS device. These methods may be used to manufacture released and unreleased interferometric modulators.

Claims

1. A method of making a microelectromechanical system (MEMS) device, comprising:

forming a permeable layer over an underlying layer material, wherein the permeable layer comprises a masking material more resistant to removal by an etchant than the underlying layer material;

removing a portion of the underlying layer material by flowing the etchant through the permeable layer, thereby forming a non-planar surface on the remaining lower layer material; and

depositing an overlying layer over the non-planer surface formed on the underlying layer to form a non-planar interface between the underlying layer and the overlying layer.

2. The method of claim 1, wherein the underlying layer material comprises at least one of glass and plastic.

3. The method of claim 1, further comprising removing substantially all of the permeable layer after removing the portion of the underlying layer.

4. The method of claim 1, wherein the underlying layer material comprises a metal.

5. The method of claim 1, wherein the underlying layer comprises a dielectric material.

6. The method of claim 1, wherein the permeable layer comprises aluminum.

7. A method of making a microelectromechanical system (MEMS) device, comprising:

providing a substrate;

depositing a sacrificial material over at least a portion of the substrate, the sacrificial material being removable by a first etchant;

forming a permeable layer over the sacrificial material, wherein the permeable layer comprises a masking material more resistant to removal by the first etchant than the sacrificial material;

removing a portion of the sacrificial material by flowing the first etchant through the permeable layer, thereby forming a non-planar surface on the remaining sacrificial material; and

forming an electrically conductive layer over at least a portion of the non-planar surface.

8. The method of claim 7, wherein forming the permeable layer comprises flash depositing the masking material.

9. The method of claim 8, wherein the masking material comprises at least one of aluminum and aluminum oxide.

10. The method of claim 7, wherein forming the permeable layer comprises:

depositing a layer of aluminum over the sacrificial material; and

anodizing the layer of aluminum.

11. The method of claim 7, further comprising removing substantially all of the permeable layer after removing the portion of the sacrificial material.

12. The method of claim 11, wherein removing the permeable layer comprises:

selectively etching the permeable layer with a second etchant, the second etchant being more effective at removing the masking material than removing the sacrificial material.

13. The method of claim 7, further comprising forming a dielectric layer over the substrate, wherein the sacrificial material comprises a dielectric material of the dielectric layer.

14. The method of claim 7, further comprising removing substantially all of the remaining sacrificial material, thereby forming a cavity between the substrate and the electrically conductive layer.

15. The method of claim 7, wherein the substrate comprises a second electrically conductive layer.

16. The method of claim 15, wherein the second electrically conductive layer comprises indium tin oxide.

17. The method of claim 7, wherein forming the permeable layer comprises:

forming a continuous mask layer over the sacrificial material, the continuous mask layer comprising a plurality of regions configured to be removable at different relative rates; and

removing a portion of the continuous mask layer.

18. The method of claim 17, wherein removing the portion of the continuous mask layer comprises exposing the continuous mask layer to the first etchant.

19. The method of claim 17, wherein removing the portion of the continuous mask layer comprises exposing the continuous mask layer to a second etchant.

20. The method of claim 7, wherein the electrically conductive layer comprises a movable layer.

21. The method of claim 7, wherein the substrate comprises a partially reflective layer.

22. A method of making an interferometric modulator, comprising:

providing a substrate;

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

depositing a sacrificial material over at least a portion of the first electrically conductive layer, the sacrificial material being removable by an etchant;

forming a permeable layer over the sacrificial material, wherein the permeable layer comprises a masking material;

removing a portion of the sacrificial material by flowing the etchant through the permeable layer, thereby forming a non-planar surface on the sacrificial material; and

forming a second electrically conductive layer over at least a portion of the non-planar surface.

23. The method of claim 22, wherein forming the permeable layer comprises flash depositing the masking material.

24. The method of claim 23, wherein the masking material comprises at least one of aluminum and aluminum oxide.

25. The method of claim 22, wherein forming the permeable layer comprises:

depositing a layer of aluminum over the sacrificial material; and

anodizing the layer of aluminum.

26. The method of claim 22, further comprising removing substantially all of the permeable layer after removing the portion of the sacrificial material.

27. The method of claim 22, further comprising forming a dielectric layer over the first electrically conductive layer.

28. The method of claim 27, wherein the sacrificial material comprises a dielectric material of the dielectric layer.

29. The method of claim 27, further comprising depositing the sacrificial material over the dielectric layer.

30. The method of claim 22, wherein the first electrically conductive layer comprises indium tin oxide.

31. The method of claim 22, wherein the second electrically conductive layer comprises a movable layer.

32. The method of claim 22, wherein forming the permeable layer comprises:

forming a continuous mask layer over the sacrificial material, the continuous mask layer comprising a plurality of regions configured to be removable at different relative rates; and

removing a portion of the continuous mask layer.

33. The method of claim 32, wherein removing the portion of the continuous mask layer comprises exposing the continuous mask layer to the etchant.

34. The method of claim 32, wherein removing the portion of the continuous mask layer comprises exposing the continuous mask layer to a second etchant.

35. The method of claim 22, further comprising removing a substantial portion of the permeable layer while removing the portion of the sacrificial material.

36. The method of claim 22, further comprising:

forming a support structure aperture in a portion of the deposited sacrificial material; and

depositing an insulator into the support structure aperture.

37. An unreleased interferometric modulator made by the method of claim 22.

38. The method of claim 22, further comprising removing substantially all of the remaining sacrificial material, thereby forming a cavity between the substrate and the electrically conductive layer.

39. A released interferometric modulator made by the method of claim 38.

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

a substrate;

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

a sacrificial layer over at least a portion of the first electrically conductive layer, the sacrificial layer comprising a material removable by an etchant, wherein the sacrificial layer comprises a non-planar surface;

a permeable layer over the non-planar surface of the sacrificial layer, wherein the permeable layer comprises a masking material more resistant to removal by the etchant than the sacrificial layer material; and

a second electrically conductive layer over at least a portion of the permeable layer.

41. The unreleased MEMS device of claim 40, wherein the MEMS device is an interferometric modulator.

42. The unreleased MEMS device of claim 41, further comprising a dielectric layer between the first electrically conductive layer and the sacrificial layer.

43. The unreleased MEMS device of claim 40, wherein the sacrificial layer comprises molybdenum.

44. The unreleased MEMS device of claim 40, wherein the permeable layer comprises anodized aluminum.

45. An interferometric modulator, comprising:

a substrate;

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

a second electrically conductive layer separated from the first electrically conductive layer by a cavity, wherein the second electrically conductive layer comprises a non-planar surface layer facing the substrate, and wherein surface asperities on the non-planar surface exhibit a skewness greater than about zero; and

a support structure arranged over the substrate and configured to support the second electrically conductive layer.

46. The interferometric modulator of claim 45, wherein the non-planar surface layer comprises a permeable layer comprising aluminum.

48. The interferometric modulator of claim 46, wherein the permeable layer comprises anodized aluminum.

49. The interferometric modulator of claim 45, wherein the surface asperities on the non-planar surface exhibit a kurtosis greater than about three.

50. An array of interferometric modulators, comprising the interferometric modulator of claim 45.

51. A display device comprising:

an array of interferometric modulators as claimed in claim 50;

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.

52. The display device of claim 51, further comprising a driver circuit configured to send at least one signal to the array.

53. The apparatus as recited in claim 52, further comprising a controller configured to send at least a portion of the image data to the driver circuit.

54. The apparatus as recited in claim 51, further comprising an image source module configured to send the image data to the processor.

55. The apparatus as recited in claim 54, wherein the image source module comprises at least one of a receiver, transceiver, and transmitter.

56. The apparatus as recited in claim 51, further comprising an input device configured to receive input data and to communicate the input data to the processor.

47. The interferometric modulator of 46, wherein the permeable layer comprises an oxide of aluminum.