Microbolometer infrared detector elements and methods for forming same

• US 7,718,965 B1
• Filed: 08/03/2006
• Issued: 05/18/2010
• Est. Priority Date: 08/03/2006
• Status: Active Grant

• Current Assignee: DRS Network & Imaging Systems, LLC (Leonardo S.p.A.)
• Original Assignee: L-3 Communications Corporation (L3Harris Technologies, Inc.)
• Inventors: Taylor, Michael F., Syllaios, Athanasios J., Schimert, Thomas R.
• Primary Examiner(s): Porta; David P
• Assistant Examiner(s): Malevic; Djura
• Application Number:
  US11/498,939
• Publication Number:
  US 20100133536A1
• Time in Patent Office: 1,384 Days
• Field of Search: 250/338.1, 250/338.4
• US Class Current: 250/338.1
• CPC Class Codes: G01J 5/02 Constructional details
• CPC Class Codes: G01J 5/023 Particular leg structure or construction or shape; Nanotubes
• CPC Class Codes: G01J 5/04 Casings
• CPC Class Codes: G01J 5/046 Materials; Selection of thermal materials
• CPC Class Codes: G01J 5/20 using resistors, thermistors or semiconductors sensitive to radiation, e.g. photoconductive devices

Abstract

Microbolometer infrared detector elements that may be formed and implemented by varying type/s of precursors used to form amorphous silicon-based microbolometer membrane material/s and/or by varying composition of the final amorphous silicon-based microbolometer membrane material/s (e.g., by adjusting alloy composition) to vary the material properties such as activation energy and carrier mobility. The amorphous silicon-based microbolometer membrane material/s materials may include varying amounts of one or more additional and optional materials, including hydrogen, fluorine, germanium, n-type dopants and p-type dopants.

Claims

1. An infrared detector element comprising:

a substrate; and

an infrared detector membrane disposed in spaced relationship above said substrate;

wherein said infrared detector membrane comprises an amorphous silicon-based material, said amorphous silicon-based material comprising at least one of a fluorinated amorphous silicon-based material, an amorphous silicon germanium-based material, an amorphous germanium-based material, a hydrogenated amorphous silicon-based material having a hydrogen content of greater than about 4 atomic percent, or a combination thereof; and

wherein a material structure of said amorphous silicon-based material comprises microcrystallites.

2. The infrared detector element of claim 1, wherein said amorphous silicon-based material comprises at least one of fluorinated amorphous silicon, hydrogenated fluorinated amorphous silicon, amorphous silicon germanium, hydrogenated amorphous silicon germanium, fluorinated amorphous silicon germanium, hydrogenated fluorinated amorphous silicon germanium, hydrogenated amorphous silicon-based material having a hydrogen content of greater than about 4 atomic percent, or a combination thereof.

3. The infrared detector element of claim 1, wherein said amorphous silicon-based material comprises at least one of a fluorinated amorphous silicon-based material, an amorphous silicon germanium-based material, or a combination thereof.

4. The infrared detector element of claim 3, wherein said amorphous silicon-based material comprises at least one of fluorinated amorphous silicon, hydrogenated fluorinated amorphous silicon, amorphous silicon germanium, hydrogenated amorphous silicon germanium, fluorinated amorphous silicon germanium, hydrogenated fluorinated amorphous silicon germanium, or a combination thereof.

5. The infrared detector element of claim 1, wherein said amorphous silicon-based material comprises fluorinated amorphous silicon-based material.

6. The infrared detector element of claim 1, wherein said amorphous silicon-based material comprises amorphous silicon germanium-based material.

7. The infrared detector element of claim 1, wherein said amorphous silicon-based material comprises a fluorinated amorphous silicon-based material doped with a p-type dopant, said p-doped fluorinated amorphous silicon-based material comprising at least one of p-doped fluorinated amorphous silicon, p-doped hydrogenated fluorinated amorphous silicon, p-doped fluorinated amorphous silicon germanium, p-doped hydrogenated fluorinated amorphous silicon germanium, or a combination thereof;

and wherein said p-type dopant comprises boron.

8. The infrared detector element of claim 1, wherein an amount of said microcrystallites in said material structure of said amorphous silicon-based material is less than or equal to about 10% by volume of the amorphous silicon-based material, said microcrystallines being from about 1 nanometers to about 10 nanometers in size.

9. The infrared detector element of claim 1, wherein said amorphous silicon-based material comprises a hydrogenated amorphous silicon-based material having a hydrogen content of greater than about 4 atomic percent.

10. The infrared detector element of claim 1, wherein said substrate comprises read out integrated circuitry (ROIC);

and wherein said infrared detector membrane is suspended in spaced relationship above said substrate and electrically coupled to said ROIC by two thermal isolation legs.

11. The infrared detector element of claim 1, further comprising an anti-reflective structure disposed between said substrate and said infrared detector membrane.

12. The infrared detector element of claim 11, wherein said anti-reflective structure comprises a reflector;

and wherein said infrared detector membrane is disposed above said reflector at a height of one-quarter wavelength of the infrared radiation to be detected.

13. The infrared detector element of claim 1, wherein said infrared detector membrane has at least one opening defined therein.

14. The infrared detector element of claim 13, wherein said at least one opening comprises a plurality of openings configured as a grid of openings defined in said infrared detector membrane;

and wherein said infrared detector element comprises a diffractive resonant cavity (DRC) microbolometer structure and further comprises a reflector disposed between said substrate and said infrared detector membrane and having an upper surface configured to reflect infrared radiation.

15. A focal plane array, comprising a plurality of infrared detector elements of claim 1.

16. A focal plane array assembly, comprising:

a substrate; and

a plurality of infrared detector elements, each of said plurality of infrared detector elements comprising an infrared detector membrane disposed in spaced relationship above said substrate, and read out integrated circuitry (ROIC) electrically coupled to said infrared detector membrane;

wherein said infrared detector membrane of each of said plurality of infrared detector elements comprises an amorphous silicon-based material, said amorphous silicon-based material comprising at least one of a fluorinated amorphous silicon-based material, an amorphous silicon germanium-based material, an amorphous germanium-based material, a hydrogenated amorphous silicon-based material having a hydrogen content of greater than about 4 atomic percent, or a combination thereof; and

wherein a material structure of said amorphous silicon-based material comprises microcrystallites.

17. The focal plane array assembly of claim 16, wherein said amorphous silicon-based material of each of said plurality of infrared detector elements comprises at least one of fluorinated amorphous silicon, hydrogenated fluorinated amorphous silicon, amorphous silicon germanium, hydrogenated amorphous silicon germanium, fluorinated amorphous silicon germanium, hydrogenated fluorinated amorphous silicon germanium, hydrogenated amorphous silicon-based material having a hydrogen content of greater than about 4 atomic percent, or a combination thereof.

18. The focal plane array assembly of claim 16, wherein said amorphous silicon-based material of each of said plurality of infrared detector elements comprises at least one of a fluorinated amorphous silicon-based material, an amorphous silicon germanium-based material, or a combination thereof.

19. The focal plane array assembly of claim 18, wherein said amorphous silicon-based material of each of said plurality of infrared detector elements comprises at least one of fluorinated amorphous silicon, hydrogenated fluorinated amorphous silicon, amorphous silicon germanium, hydrogenated amorphous silicon germanium, fluorinated amorphous silicon germanium, hydrogenated fluorinated amorphous silicon germanium, or a combination thereof.

20. The focal plane array assembly of claim 16, wherein said amorphous silicon-based material of each of said plurality of infrared detector elements comprises fluorinated amorphous silicon-based material.

21. The focal plane array assembly of claim 16, wherein said amorphous silicon-based material of each of said plurality of infrared detector elements comprises amorphous silicon germanium-based material.

22. The focal plane array assembly of claim 16, wherein said amorphous silicon-based material of each of said plurality of infrared detector elements comprises a fluorinated amorphous silicon-based material doped with a p-type dopant, said p-doped fluorinated amorphous silicon-based material comprising at least one of p-doped fluorinated amorphous silicon, p-doped hydrogenated fluorinated amorphous silicon, p-doped fluorinated amorphous silicon germanium, p-doped hydrogenated fluorinated amorphous silicon germanium, or a combination thereof;

and wherein said p-type dopant comprises boron.

23. The focal plane array assembly of claim 16, wherein an amount of said microcrystallites in said material structure of said amorphous silicon-based material is less than or equal to about 10% by volume of the amorphous silicon-based material, said microcrystallines being from about 1 nanometers to about 10 nanometers in size.

24. The focal plane array assembly of claim 16, wherein said amorphous silicon-based material of each of said plurality of infrared detector elements comprises a hydrogenated amorphous silicon-based material having a hydrogen content of greater than about 4 atomic percent.

25. The focal plane array assembly of claim 24, wherein said hydrogenated amorphous silicon-based material of each of said plurality of infrared detector elements comprises at least one of hydrogenated amorphous silicon, hydrogenated fluorinated amorphous silicon, hydrogenated amorphous silicon germanium, hydrogenated fluorinated amorphous silicon germanium, or a combination thereof.

26. A wafer-level packaged focal plane array assembly, comprising:

a device wafer, said device wafer comprising said focal plane array assembly of claim 16; and

a lid wafer, said lid wafer being at least partially transmissive of infrared radiation and being assembled to said device wafer such that said lid wafer allows infrared radiation to reach said focal plane array assembly through said lid wafer.

27. The wafer-level packaged focal plane array assembly of claim 26, wherein said lid wafer is sealingly assembled to said device wafer and contains a vacuum therebetween to form a wafer-level packaged focal plane array assembly.

28. A method for making an infrared detector element comprising:

providing a substrate; and

forming an infrared detector membrane in spaced relationship above a surface of said substrate;

wherein said infrared detector membrane comprises an amorphous silicon-based material, said amorphous silicon-based material comprising at least one of a fluorinated amorphous silicon-based material, an amorphous silicon germanium-based material, an amorphous germanium-based material, a hydrogenated amorphous silicon-based material having a hydrogen content of greater than about 4 atomic percent, or a combination thereof;

wherein said method comprises forming said amorphous silicon-based material from at least one silicon source that is diluted with hydrogen gas; and

wherein a material structure of said amorphous silicon-based material comprises microcrystallites.

29. The method of claim 28, wherein said amorphous silicon-based material comprises at least one of fluorinated amorphous silicon, hydrogenated fluorinated amorphous silicon, amorphous silicon germanium, hydrogenated amorphous silicon germanium, fluorinated amorphous silicon germanium, hydrogenated fluorinated amorphous silicon germanium, hydrogenated amorphous silicon-based material having a hydrogen content of greater than about 4 atomic percent, or a combination thereof.

30. The method of claim 28, wherein said amorphous silicon-based material comprises at least one of a fluorinated amorphous silicon-based material, an amorphous silicon germanium-based material, or a combination thereof.

31. The method of claim 28, wherein said amorphous silicon-based material comprises at least one of fluorinated amorphous silicon, hydrogenated fluorinated amorphous silicon, amorphous silicon germanium, hydrogenated amorphous silicon germanium, fluorinated amorphous silicon germanium, hydrogenated fluorinated amorphous silicon germanium, or a combination thereof.

32. The method of claim 28, wherein said amorphous silicon-based material comprises fluorinated amorphous silicon-based material.

33. The method of claim 28, wherein said amorphous silicon-based material comprises amorphous silicon germanium-based material.

34. The method of claim 28, further comprising doping said amorphous silicon-based material by forming said amorphous silicon-based material with precursors that comprise boron trifluoride (BF₃).

35. The method of claim 28, further comprising forming said amorphous silicon-based material such that an amount of said microcrystallites in said material structure of said amorphous silicon-based material is less than or equal to about 10% by volume of the amorphous silicon-based material, said microcrystallites being from about 1 nanometers to about 10 nanometers in size.

36. The method of claim 28, wherein said amorphous silicon-based material comprises at least one of hydrogenated amorphous silicon, hydrogenated fluorinated amorphous silicon, hydrogenated amorphous silicon germanium, hydrogenated fluorinated amorphous silicon germanium, or a combination thereof.

37. The method of claim 28, further comprising:

forming read out integrated circuitry (ROIC) within said substrate;

forming two thermal isolation legs between said substrate and said infrared detector membrane to suspend said infrared detector membrane in spaced relationship above said substrate; and

electrically coupling said infrared detector membrane to said ROIC.

38. The method of claim 28, further comprising forming an anti-reflective structure between said substrate and said infrared detector membrane.

39. The method of claim 38, wherein said anti-reflective structure comprises a reflector;

and wherein said method further comprises forming said infrared detector membrane in spaced relationship above said reflector at a height of one-quarter wavelength of the infrared radiation to be detected.

40. The method of claim 28, further comprising forming at least one opening within said infrared detector membrane.

41. The method of claim 40, further comprising:

forming a plurality of openings configured as a grid of openings in said infrared detector membrane; and

forming a reflector between said substrate and said infrared detector membrane, said reflector having an upper surface configured to reflect infrared radiation.

42. A method of forming a focal plane array, comprising forming a plurality of infrared detector elements of claim 28.

43. A method of making a focal plane array assembly, comprising:

providing a substrate; and

forming a plurality of infrared detector elements, each of said plurality of infrared detector elements comprising an infrared detector membrane disposed in spaced relationship above said substrate, and read out integrated circuitry (ROIC) electrically coupled to said infrared detector membrane;

wherein said infrared detector membrane comprises an amorphous silicon-based material, said amorphous silicon-based material comprising at least one of a fluorinated amorphous silicon-based material, an amorphous silicon germanium-based material, an amorphous germanium-based material, a hydrogenated amorphous silicon-based material having a hydrogen content of greater than about 4 atomic percent, or a combination thereof;

wherein said method comprises forming said amorphous silicon-based material from at least one silicon source that is diluted with hydrogen gas; and

wherein a material structure of said amorphous silicon-based material comprises microcrystallites.

44. The method of claim 43, wherein said amorphous silicon-based material comprises at least one of fluorinated amorphous silicon, hydrogenated fluorinated amorphous silicon, amorphous silicon germanium, hydrogenated amorphous silicon germanium, fluorinated amorphous silicon germanium, hydrogenated fluorinated amorphous silicon germanium, hydrogenated amorphous silicon-based material having a hydrogen content of greater than about 4 atomic percent, or a combination thereof.

45. The method of claim 43, wherein said amorphous silicon-based material comprises at least one of a fluorinated amorphous silicon-based material, an amorphous silicon germanium-based material, or a combination thereof.

46. The method of claim 45, wherein said amorphous silicon-based material of each of said plurality of infrared detector elements comprises at least one of fluorinated amorphous silicon, hydrogenated fluorinated amorphous silicon, amorphous silicon germanium, hydrogenated amorphous silicon germanium, fluorinated amorphous silicon germanium, hydrogenated fluorinated amorphous silicon germanium, or a combination thereof.

47. The method of claim 43, wherein said amorphous silicon-based material of each of said plurality of infrared detector elements comprises fluorinated amorphous silicon-based material.

48. The method of claim 43, wherein said amorphous silicon-based material of each of said plurality of infrared detector elements comprises amorphous silicon germanium-based material.

49. The method of claim 43, further comprising doping said amorphous silicon-based material by forming said amorphous silicon-based material with precursors that comprise boron trifluoride (BF₃).

50. The method of claim 43, further comprising forming said amorphous silicon-based material such that an amount of said microcrystallites in said material structure of said amorphous silicon-based material is less than or equal to about 10% by volume of the amorphous silicon-based material, said microcrystallites being from about 1 nanometers to about 10 nanometers in size.

51. The method of claim 43, wherein said amorphous silicon-based material of each of said plurality of infrared detector elements comprises at least one of hydrogenated amorphous silicon, hydrogenated fluorinated amorphous silicon, hydrogenated amorphous silicon germanium, hydrogenated fluorinated amorphous silicon germanium, or a combination thereof.

52. A method of making a wafer-level packaged focal plane array assembly, comprising:

providing a device wafer, said device wafer comprising said focal plane array assembly of claim 43;

providing a lid wafer, said lid wafer being at least partially transmissive of infrared radiation; and

assembling said lid wafer to said device wafer to form said wafer-level packaged focal plane array assembly, and such that said lid wafer allows infrared radiation to reach said focal plane array assembly through said lid wafer.

53. The method of claim 52, further comprising assembling and sealing said lid wafer to said device wafer in the presence of a vacuum such that a vacuum is sealingly contained between said lid wafer and said device wafer to form a wafer-level vacuum packaged focal plane array assembly.

54. A method for making an infrared detector element comprising:

providing a substrate;

forming an infrared detector membrane in spaced relationship above a surface of said substrate, said infrared detector membrane comprising amorphous silicon-based material;

forming said amorphous silicon-based material from precursors comprising at least one source of silicon and boron trifluoride (BF₃);

wherein said method comprises forming said amorphous silicon-based material from at least one silicon source that is diluted with hydrogen gas; and

wherein a material structure of said amorphous silicon-based material comprises microcrystallites.

55. A method of forming a focal plane array, comprising forming a plurality of infrared detector elements of claim 54.