Diffusion barrier layer for MEMS devices

• US 20070096300A1
• Filed: 10/28/2005
• Published: 05/03/2007
• Est. Priority Date: 10/28/2005
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Zee, Stephen, Tung, Ming-Hau, Wang, Hsin-Fu
• Granted Patent: US 7,630,114 B2
• Time in Patent Office: Days
• US Class Current: 257/709
• CPC Class Codes: B81B 2201/047 Optical MEMS not provided for in B81B2201/042 - B81B2201/045
• 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 1/00793 Avoid contamination, e.g. absorption of impurities or oxidation
• CPC Class Codes: B81C 2201/0167 by adding further layers of materials having complementary strains, i.e. compressive or tensile strain
• 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

Described herein is the use of a diffusion barrier layer between metallic layers in MEMS devices. The diffusion barrier layer prevents mixing of the two metals, which can alter desired physical characteristics and complicate processing. In one example, the diffusion barrier layer may be used as part of a movable reflective structure in interferometric modulators.

Claims

1. A MEMS device, comprising a mechanical membrane, wherein the membrane includes:

a first metallic layer;

a second metallic layer; and

a diffusion barrier layer positioned between the first metallic layer and the second metallic layer, wherein the diffusion barrier layer is adapted to substantially inhibit any portion of the first metallic layer from mixing with any portion of the second metallic layer.

2. The device of claim 1, wherein the first metallic layer comprises aluminum.

3. The device of claim 1, wherein the second metallic layer comprises chromium.

4. The device of claim 1, wherein the second metallic layer comprises one or more metal(s) selected from the group consisting of titanium, copper, iron, silicon, manganese, magnesium, lithium, silver, gold, nickel, tantalum, and tungsten.

5. The device of claim 1, wherein the diffusion barrier layer comprises an oxide, nitride, or carbide.

6. The device of claim 1, wherein the diffusion barrier layer comprises silicon dioxide.

7. The device of claim 1, wherein the diffusion barrier layer comprises one or more compounds selected from the group consisting of an aluminum oxide, Si₃N₄, titanium nitride, tantalum nitride, silicon carbide, titanium carbide, alumino silicate, and TiB₂.

8. The device of claim 1, wherein the diffusion barrier layer comprises one or more metals selected from the group consisting of titanium, tungsten, titanium-tungsten alloy, silicon, and tantalum.

9. The device of claim 1, wherein the MEMS device is an interferometric modulator and the first metallic layer acts as a mirror in the mechanical membrane.

10. The device of claim 1, wherein the diffusion barrier layer is adapted to also act as an etch stop by being resistant to an etchant capable of etching the second metallic layer.

11. The device of claim 1, wherein the diffusion barrier layer has a thickness of at least about 15 angstroms.

12. The device of claim 1, wherein the thickness of the first metallic layer is between about 200 angstroms and about 2000 angstroms.

13. The device of claim 1, wherein the thickness of the second metallic layer is between about 80 angstroms and about 1000 angstroms.

14. The device of claim 1, wherein the thickness of the first metallic layer is between about 800 angstroms and about 1200 angstroms, the thickness of the second metallic layer is between about 100 angstroms and about 500 angstroms, and the thickness of the diffusion barrier layer is between about 20 angstroms and about 60 angstroms.

15. The device of claim 14, wherein the first metallic layer is aluminum, the second metallic layer is chromium, and the diffusion barrier layer is silicon dioxide.

16. A method of substantially inhibiting any portion of a first metallic layer from mixing with any portion of a second metallic layer in a MEMS device mechanical membrane, comprising positioning a diffusion barrier layer between the first and second metallic layers.

17. The method of claim 16, wherein the first metallic layer comprises aluminum.

18. The method of claim 16, wherein the second metallic layer comprises chromium.

19. The method of claim 16, wherein the diffusion barrier layer comprises an oxide, nitride, or carbide.

20. The method of claim 16, wherein the diffusion barrier layer comprises silicon dioxide.

21. The method of claim 16, wherein the MEMS device is an interferometric modulator and the first metallic layer acts as a mirror in the mechanical membrane.

22. The method of claim 16, wherein the positioning of the diffusion barrier layer comprises:

depositing the diffusion barrier layer onto the first metallic layer; and

depositing the second metallic layer onto the diffusion barrier layer.

23. The method of claim 22, wherein the deposition of the diffusion barrier layer is conducted using physical vapor deposition, chemical vapor deposition, or sol gel processing.

24. A method of manufacturing a MEMS device, comprising:

depositing a first metallic layer;

depositing a diffusion barrier layer onto the first metallic layer;

depositing a second metallic layer onto the diffusion barrier layer, wherein the diffusion barrier layer is adapted to substantially inhibit any portion of the first metallic layer from mixing with any portion of the second metallic layer; and

etching a same pattern in the first metallic layer, diffusion barrier layer, and second metallic layer.

25. The method of claim 24, wherein the first metallic layer comprises aluminum.

26. The method of claim 24, wherein the second metallic layer comprises chromium.

27. The method of claim 24, wherein the diffusion barrier layer comprises an oxide, nitride, or carbide.

28. The method of claim 24, wherein the diffusion barrier layer comprises silicon dioxide.

29. The method of claim 24, wherein etching a same pattern comprises employing different etchants for each of the first metallic layer, diffusion barrier layer, and second metallic layer.

30. A MEMS device, comprising a mechanical membrane produced by the process of claim 24.

31. An interferometric modulator, comprising a movable reflective layer that includes:

a mirror;

a mechanical layer adjacent to the mirror, the mechanical layer adapted to provide mechanical support for the mirror; and

a diffusion barrier between the mirror and the mechanical layer, wherein the diffusion barrier is adapted to substantially inhibit mixing of any portion of the mirror with any portion of the mechanical layer.

32. The interferometric modulator of claim 31, wherein the mirror comprises aluminum.

33. The interferometric modulator of claim 31, wherein the diffusion barrier comprises an oxide, nitride, or carbide.

34. The interferometric modulator of claim 31, wherein the diffusion barrier comprises silicon dioxide.

35. The interferometric modulator of claim 31, wherein the mechanical layer comprises chromium.

36. The interferometric modulator of claim 31, further comprising:

a display;

a processor that is configured to communicate with said display, said processor being configured to process image data; and

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

37. The apparatus of claim 36, further comprising a driver circuit configured to send at least one signal to said display.

38. The apparatus of claim 37, further comprising a controller configured to send at least a portion of said image data to said driver circuit.

39. The apparatus of claim 36, further comprising an image source module configured to send said image data to said processor.

40. The apparatus of claim 39, wherein said image source module comprises at least one of a receiver, transceiver, and transmitter.

41. The apparatus of claim 36, further comprising an input device configured to receive input data and to communicate said input data to said processor.

42. An interferometric modulator, comprising a movable reflective layer that includes:

reflecting means for reflecting light;

mechanical support means for providing mechanical support to the reflecting means; and

diffusion barrier means for preventing diffusion between the reflecting means and the mechanical support means.

43. The interferometric modulator of claim 42, wherein the reflecting means is a mirror.

44. The interferometric modulator of claim 42, wherein the mechanical support means is a metallic mechanical layer.

45. The interferometric modulator of claim 44, wherein the metallic mechanical layer comprises one or more metals selected from the group consisting of chromium, titanium, copper, iron, silicon, manganese, magnesium, lithium, silver, gold, nickel tantalum, and tungsten.

46. The interferometric modulator of claim 42, 43, 44, or 45, wherein the diffusion barrier means comprises one or more compounds selected from the group consisting of silicon dioxide, an aluminum oxide, Si₃N₄, titanium nitride, tantalum nitride, silicon carbide, titanium carbide, alumino silicate, and TiB₂.

47. A method of manufacturing an interferometric modulator, comprising:

depositing a first metallic layer;

depositing a diffusion barrier layer onto the first metallic layer;

depositing a second metallic layer onto the diffusion barrier layer, wherein the diffusion barrier layer is adapted to substantially inhibit any portion of the first metallic layer from mixing with any portion of the second metallic layer; and

etching a same pattern in the second metallic layer, the diffusion barrier, and the first metallic layer.

48. The method of claim 47, wherein etching the pattern in the second metallic layer comprises using a first etchant, etching the pattern in the diffusion barrier comprises using a second etchant, and etching the pattern in the first metallic layer comprises using a third etchant.

49. The method of claim 47, wherein the diffusion barrier layer comprises an oxide, nitride, or carbide.

50. The method of claim 47, wherein the diffusion barrier layer comprises silicon dioxide.

51. The method of claim 48, wherein the diffusion barrier layer and the first metallic layer is substantially resistant to the first etchant.

52. The method of claim 48, wherein the first metallic layer the second metallic layer is substantially resistant to the second etchant.

53. The method of claim 48, wherein the diffusion barrier layer and the second metallic layer is substantially resistant to the third etchant.

54. The method of claim 48, wherein the first etchant is CR14.

55. The method of claim 48, wherein the second etchant is PAD.

56. The method of claim 48, wherein the third etchant is PAN.

57. An interferometric modulator produced by the process of claim 47.

58. A method of manufacturing a movable electrode in a MEMS device having a desired tensile stress, comprising:

determining a desired tensile stress or range of tensile stress for the movable electrode;

forming one or more layers comprising a material having tensile stress; and

forming one or more layers comprising a material having compressive stress adjacent to the tensile stress materials, whereby combination of the tensile stress of the compressive stress provide the desired tensile stress or range of tensile stress for the movable electrode.

59. The method of claim 58, wherein the material of the tensile stress layers is one or more metal(s).

60. The method of claim 59, wherein the metal is selected from the group consisting of aluminum, chromium, titanium, copper, iron, silicon, manganese, magnesium, lithium, silver, gold, nickel, tantalum, and tungsten.

61. The method of claim 58, wherein the compressive stress layers is one or more oxide, nitride, or carbide.

62. The method of claim 58, wherein at least one compressive stress layer comprises silicon dioxide.

63. A MEMS device movable electrode produced by the process of claim 58.