Systems and methods for integrating focal plane arrays

• US 7,459,686 B2
• Filed: 11/30/2006
• Issued: 12/02/2008
• Est. Priority Date: 01/26/2006
• Status: Active Grant

• Current Assignee: L3 Technologies, Inc. (L3Harris Technologies, Inc.)
• Original Assignee: L-3 Communications Corporation (L3Harris Technologies, Inc.)
• Inventors: Brady, John F., Gooch, Roland W., Syllaios, Athanasios J., Schimert, Thomas R., McCardel, William L.
• Primary Examiner(s): Porta; David P
• Assistant Examiner(s): Taningco; Marcus H
• Application Number:
  US11/606,880
• Publication Number:
  US 20070170359A1
• Time in Patent Office: 733 Days
• Field of Search: 250/338.1
• US Class Current: 250/338.1
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0232 using shutters
• CPC Class Codes: G01J 3/2803 using photoelectric array detector
• CPC Class Codes: G01J 3/2823 Imaging spectrometer
• CPC Class Codes: G01J 3/36 Investigating two or more bands of a spectrum by separate detectors
• CPC Class Codes: G01J 5/024 Special manufacturing steps or sacrificial layers or layer structures
• CPC Class Codes: G01J 5/20 using resistors, thermistors or semiconductors sensitive to radiation, e.g. photoconductive devices
• CPC Class Codes: H01L 27/14621 Colour filter arrangements
• CPC Class Codes: H01L 27/14647 Multicolour imagers having a stacked pixel-element structure, e.g. npn, npnpn or MQW elements
• CPC Class Codes: H01L 27/1467 of the hybrid type
• CPC Class Codes: H01L 27/14685 Process for coatings or optical elements
• CPC Class Codes: H01L 27/14687 Wafer level processing
• CPC Class Codes: H01L 2924/381 Pitch distance
• CPC Class Codes: H04N 23/11 for generating image signals from visible and infrared light wavelengths
• CPC Class Codes: H04N 23/23 from thermal infrared radiation
• CPC Class Codes: H04N 5/33 Transforming infrared radiation cameras or camera modules for generating image signals from infrared radiation H04N23/20; circuitry of SSIS for transforming infrared radiation into image signals H04N25/20

Abstract

Systems and methods for providing multi-spectral image capability using an integrated multi-band focal plane array that, in one example, may be employed to simultaneously image in the visible spectrum and infrared spectrum using an integrated dual-band focal plane array, e.g., by including visible imaging circuitry within read out integrated circuitry (ROIC) used to readout infrared detector elements within the same pixel element/s.

Claims

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

a device wafer, said device wafer comprising a multi-band focal plane array; and

a lid wafer, said lid wafer being at least partially transparent to visible and infrared radiation and being assembled to said device wafer so that said lid wafer allows visible radiation to reach said multi-band focal plane array through said lid wafer;

wherein said multi-band focal plane array comprises a plurality of detector elements, each of said detector elements comprising;

a substrate,

read out integrated circuitry (ROIC) disposed on said substrate, said ROIC including visible imaging circuitry configured to detect visible radiation, and

an infrared radiation detector structure configured to absorb infrared radiation, said infrared detector structure comprising a membrane supported at a position spaced above said substrate, said membrane having at least one opening defined therein and configured to allow visible spectrum radiation to reach said visible imaging circuitry through said membrane.

2. The wafer-level packaged focal plane array assembly of claim 1, where said ROIC of each of said respective detector elements further comprises infrared detector read out circuitry coupled to said infrared detector structure.

3. The wafer-level packaged focal plane array assembly of claim 1, wherein each of said detector elements comprises a microbolometer structure;

and wherein said at least one opening of each of said respective detector elements comprises a plurality of openings configured as a grid of openings defined in said membrane of said respective detector element.

4. The wafer-level packaged focal plane array assembly of claim 3, wherein said infrared detector structure of each of said respective detector elements comprises a diffractive resonant cavity (DRC) microbolometer structure and further comprises a lead metal reflector disposed between said substrate and said membrane of each of said respective detector elements and having an upper surface configured to reflect infrared radiation;

wherein said at least one opening of each of said respective detector elements comprises a plurality of openings configured as a grid of openings defined in said membrane of said respective detector element; and

wherein said lead metal reflector of each of said respective detector elements is patterned to have openings configured to allow said visible radiation to reach said visible imaging circuitry of said respective detector element through said lead metal reflector of said respective detector element.

5. The wafer-level packaged focal plane array assembly of claim 3, wherein said ROIC of each of said respective detector elements comprises CMOS circuitry;

wherein said infrared detector structure of each of said respective detector elements comprises a diffractive resonant cavity (DRC) microbolometer structure;

wherein a top metal layer of said CMOS circuitry of each of said respective detector elements is configured as a lead metal reflector for said DRC microbolometer structure of said respective detector element and has an upper surface configured to reflect infrared radiation;

wherein said at least one opening of each of said respective detector elements comprises a plurality of openings configured as a grid of openings defined in said membrane of said respective detector element; and

wherein said lead metal reflector of each of said respective detector elements is patterned to have openings configured to allow said visible radiation to reach said visible imaging circuitry of said respective detector element through said lead metal reflector of said respective detector element.

6. The wafer-level packaged focal plane array assembly of claim 1, wherein said infrared detector structure of each of said respective detector elements comprises a diffractive resonant cavity (DRC) microbolometer structure having a time constant of less than about 5 milliseconds.

7. The wafer-level packaged focal plane array assembly of claim 1, wherein said infrared detector structure of each of said respective detector elements comprises a diffractive resonant cavity (DRC) microbolometer structure;

and wherein said at least one opening of each of said respective detector elements comprises a single opening defined in said membrane of said respective detector element over said visible imaging circuitry of said respective detector element.

8. The wafer-level packaged focal plane array assembly of claim 1, wherein said visible imaging circuitry of each of said respective detector elements comprises an array of visible pixel detector elements and an array of color filter elements, said array of color filter elements being disposed between said at least one opening in said membrane of said respective detector element and said array of visible pixel detector elements;

wherein each of said visible pixel detector elements of said visible pixel detector element array of each of said respective detector elements is overlain by a respective color filter element of said color filter element array that lies in a path of said visible spectrum radiation between said at least one opening of said respective detector element and said pixel element.

9. A multi-band radiation detection system comprising the wafer-level packaged focal plane array assembly of claim 1, and further comprising a periodic chopper positioned between said multi-band focal plane array and a source of visible spectrum radiation and infrared spectrum radiation.

10. The multi-band radiation detection, system of claim 9, wherein said periodic chopper comprises a color-correcting chopper having a first portion and a second portion, said first portion being configured to allow said visible spectrum radiation to be focused on said multi-band focal plane array and said second portion being configured to focus said infrared spectrum radiation on said multi-band focal plane array.

11. A multi-band radiation detection system comprising the wafer-level packaged focal plane array assembly of claim 1, and further comprising an aperiodic shutter positioned between a source of radiation and said focal plane array.

12. A multi-band radiation detection system comprising the wafer-level packaged focal plane array assembly of claim 1, and further comprising no periodic chopper or aperiodic shutter positioned between a source of radiation and said focal plane array.

13. The wafer-level packaged focal plane array assembly of claim 1, 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.

14. A detector element, comprising:

a substrate;

read out integrated circuitry (ROIC) disposed on said substrate, said ROIC including visible imaging circuitry configured to detect visible spectrum radiation;

a substantially planar infrared detector membrane, said membrane having a pianar upper surface, said membrane having at least one opening defined therein that is configured to allow visible radiation to reach said visible imaging circuitry through said membrane; and

at least one thermal isolation leg supporting said infrared detector membrane in a position that is spaced above said substrate, said thermal isolation leg having a first end positioned proximal to said membrane and a second end positioned distal to said membrane, an upper surface of said first end of said thermal isolation leg being configured to lie in the same plane as the upper surface of said second end of said thermal isolation leg;

wherein a substantial entirety of the upper surface of said at least one thermal isolation leg is substantially planar and is oriented in substantially parallel and substantially coplanar relationship with said planar upper surface of said substantially planar infrared detector membrane.

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

16. The detector element of claim 14, wherein said at least one opening comprises a single opening defined in said membrane over said visible imaging circuitry.

17. The detector element of claim 14, wherein said infrared detector structure comprises a diffractive resonant cavity (DRC) microbolometer structure and further comprises a lead metal reflector disposed between said substrate and said membrane and having an upper surface configured to reflect infrared radiation;

wherein said at least one opening comprises a plurality of openings configured as a grid of openings defined in said membrane; and

wherein said lead metal reflector is patterned to have openings configured to allow said visible radiation to reach said visible imaging circuitry through said lead metal reflector.

18. The detector element of claim 14, wherein said detector element comprises a diffractive resonant cavity (DRC) microbolometer structure and further comprises a lead metal reflector disposed between said substrate and said membrane and having an upper surface configured to reflect infrared radiation;

wherein said at least one opening comprises a single opening defined in said membrane over said visible imaging circuitry; and

wherein said lead metal reflector is patterned with a single opening configured to allow said visible radiation to reach said visible imaging circuitry through said lead metal reflector.

19. The detector element of claim 14, wherein said membrane comprises no opening therein.

20. A multi-band focal plane array, comprising a plurality of detector elements of claim 14.

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

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

a lid wafer, said lid wafer being at least partially transparent to infrared radiation and being assembled to said device wafer so that said lid wafer allows infrared radiation to reach said focal plane array assembly through said lid wafer;

wherein said focal plane array assembly comprises;

a substrate, and

a plurality of multi-band detector elements, each of said plurality of multi-band detector elements comprising a membrane suspended over said substrate and read out integrated circuitry (ROIC) disposed on said substrate, said ROIC including visible imaging circuitry,

wherein said membrane of each of said multi-band detector elements has at least one opening defined therein and is configured to allow visible spectrum radiation to reach said visible imaging circuitry through said membrane.

22. The wafer-level packaged focal plane array assembly of claim 21, wherein each respective one of said plurality of multi-band detector elements comprises a microbolometer infrared detector structure that includes said membrane of said respective multi-band detector element;

and wherein said at least one opening comprises a plurality of openings configured as a grid of openings defined in said membrane of said respective multi-band detector element.

23. The wafer-level packaged focal plane array assembly of claim 22, wherein said microbolometer infrared detector structure of each of said respective multi-band detector elements comprises a diffractive resonant cavity (DRC) microbolometer structure having a time constant of less than about 5 milliseconds.

24. The wafer-level packaged focal plane array assembly of claim 21, wherein each respective one of said plurality of multi-band detector elements comprises a diffractive resonant cavity (DRC) microbolometer structure and further comprises a lead metal reflector disposed between said substrate and said membrane of said respective multi-band detector element and having an upper surface configured to reflect infrared radiation;

wherein said at least one opening of each of said respective multi-band detector elements comprises a plurality of openings configured as a grid of openings defined in said membrane of said respective multi-band detector element; and

wherein said. lead metal reflector of each of said respective multi-band detector elements is patterned to have openings configured to allow said visible radiation to reach said visible imaging circuitry of said respective multi-band detector element through said lead metal reflector of said respective multi-band detector element.

25. The wafer-level packaged focal plane array assembly of claim 21, wherein each respective one of said plurality of multi-band detector elements comprises a diffractive resonant cavity (DRC) microbolometer structure;

wherein said ROIC of each respective one of said plurality of multi-band detector elements comprises CMOS circuitry;

wherein a top metal layer of said CMOS circuitry of each of said respective multi-band detector elements is configured as a lead metal reflector for said DRC microbolometer structure of said respective multi-band detector element and has an upper surface configured to reflect infrared radiation;

wherein said at least one opening of each of said respective multi-band detector elements comprises a plurality of openings configured as a grid of openings defined in said membrane of said respective multi-band detector element; and

wherein said lead metal reflector of each of said respective multi-band detector elements is patterned to have openings configured to allow said visible radiation to reach said visible imaging circuitry of said respective multi-band detector element through said lead metal reflector of said respective multi-band detector element.

26. The wafer-level packaged focal plane array assembly of claim 21, wherein each respective one of said plurality of multi-band detector elements comprises a diffractive resonant cavity (DRC) microbolometer structure;

and wherein said at least one opening of each of said respective multi-band detector elements comprises a single opening defined in said membrane of said respective multi-band detector element over said visible imaging circuitry of said respective multi-band detector element.

27. The wafer-level packaged focal plane array assembly of claim 21, wherein said visible imaging circuitry of each respective one of said plurality of multi-band detector elements comprises an array of visible pixel detector elements and an array of color filter elements, said array of color filter elements being disposed between said at least one opening in said membrane of said respective multi-band detector element and said array of visible pixel detector elements of said respective multi-band detector element;

wherein each of said visible pixel detector elements of said visible pixel detector element array of each of said respective multi-band detector elements is overlain by a respective color filter element of said color filter element array that lies in a path of said visible spectrum radiation between said at least one opening of said respective multi-band detector element and said respective visible pixel element of said respective multi-band detector element.

28. A multi-band radiation detection system comprising the wafer-level packaged focal plane array assembly of claim 21, and further comprising a periodic chopper positioned between said focal plane array assembly and a source of visible spectrum radiation and infrared spectrum radiation.

29. The multi-band radiation detection system of claim 28, wherein said periodic chopper comprises a color-correcting chopper having a first portion and a second portion, said first portion being configured to allow said visible spectrum radiation to be focused on said focal plane array assembly and said second portion being configured to focus said infrared spectrum radiation on said focal plane array assembly.

30. A multi-band radiation detection system comprising the wafer-level packaged focal plane array assembly of claim 21, and further comprising an aperiodic shutter positioned between a source of radiation and said focal plane array assembly.

31. A multi-band radiation detection system comprising the wafer-level packaged focal plane array assembly of claim 21, and further comprising no periodic chopper or aperiodic shutter positioned between a source of radiation and said focal plane array assembly.

32. The wafer-level packaged focal plane array assembly of claim 21, 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.

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

providing a device wafer, said device wafer comprising a substrate;

providing a focal plane array assembly of multi-band detector elements on said device wafer by;

forming read out integrated circuitry (ROIC) on said first side of said substrate for said multi-band detector elements of said focal plane array assembly, said ROIC including visible imaging circuitry,

forming a plurality of membrane structures on said substrate so that each of said membrane structures corresponds to a respective multi-band detector element and is suspended over said substrate with said ROIC disposed on said substrate, and

forming at least one opening in each of said plurality of membrane structures corresponding to a respective multi-band detector element, said opening being configured to allow visible spectrum radiation to reach said visible imaging circuitry of said respective multi-band detector element through said membrane of said respective multi-band detector element;

providing a lid wafer, said lid wafer being at least partially transparent to infrared radiation; and

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

34. The method of claim 33, wherein each respective one of said plurality of multi-band detector elements comprises a microbolometer infrared detector structure that includes said membrane of said respective multi-band detector element;

and wherein said method comprises forming a plurality of openings configured as a grid in said membrane of each of said respective multi-band detector elements.

35. The method of claim 33, wherein each respective one of said plurality of multi-band detector elements comprises a diffractive resonant cavity (DRC) microbolometer structure and wherein said method further comprises:

providing a lead metal reflector between said substrate and said membrane of each of said respective multi-band detector elements, said lead metal reflector having an upper surface configured to reflect infrared radiation;

forming a plurality of openings configured as a grid in said membrane of each of said respective multi-band detector elements; and

forming a plurality of openings in said lead metal reflector of each of said respective multi-band detector elements, said plurality of openings in said lead metal reflector of said respective multi-band detector element being configured to allow said visible radiation to reach said visible imaging circuitry of said respective multi-band detector element through said lead metal reflector of said respective multi-band detector element.

36. The method of claim 33, wherein each respective one of said plurality of multi-band detector elements comprises a diffractive resonant cavity (DRC) microbolometer structure;

wherein said ROIC of each respective one of said plurality of multi-band detector elements comprises CMOS circuitry; and

wherein said method further comprises;

forming a top metal layer of said CMOS circuitry as a lead metal reflector for said DRC microbolometer of each of said respective multi-band detector elements that is reflective of infrared radiation;

forming a plurality of openings configured as a grid in said membrane of each of said respective multi-band detector elements; and

forming a plurality of openings in said lead metal reflector of each of said respective multi-band detector elements, said plurality of openings in said lead metal reflector being configured to allow said visible radiation to reach said visible imaging circuitry of said respective multi-band detector element through said lead metal reflector of said respective multi-band detector element.

37. The method of claim 33, wherein each respective one of said plurality of multi-band detector elements comprises a diffractive resonant cavity (DRC) microbolometer structure;

and wherein said method comprises forming said at least one opening as a single opening in said membrane of each of said respective multi-band detector elements over said visible imaging circuitry of said respective multi-band detector element.

38. The method of claim 33, further comprising:

forming an array of visible pixel detector elements; and

forming an array of color filter elements between said at least one opening in said membrane of each of said respective multi-band detector elements and said array of visible pixel detector elements so that each of said visible pixel detector elements of said visible pixel element array is overlain by a respective color filter element of said color filter element array that lies in a path of said visible spectrum radiation between said at least one opening of said respective multi-band detector element and said respective visible pixel detector element.

39. The method of claim 33, further comprising assembling and sealing said lid wafer to said device wafer in the presence of a vacuum so 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.

40. A multi-band detector element, comprising:

a substrate;

a first radiation detector structure disposed on said substrate, said first radiation detector structure configured to detect a radiation having a first wavelength;

a second radiation detector structure configured to absorb radiation having a second wavelength; and

a third radiation detector structure configured to absorb radiation having a third wavelength.

41. The detector element of claim 40, wherein said second radiation detector structure is supported at a position spaced above said substrate and positioned over said first radiation detector structure, said second radiation detector structure being configured to allow radiation of said first wavelength to reach said first radiation structure.

42. The detector element of claim 40, wherein said radiation having a first wavelength comprises visible radiation;

and wherein said second radiation comprises infrared radiation.

43. The detector element of claim 40, where said first radiation detector structure comprises circuitry on said substrate configured to detect visible and near infrared radiation;

and wherein said second radiation detector structure comprises a bolometer structure configured to detect infrared radiation.

44. A multi-band radiation detection system, comprising:

a multi-band focal plane array comprising a plurality of multi-band detector elements, each of said multi-band detector elements comprising;

a substrate,

read out integrated circuitry (ROIC) disposed on said substrate, said ROIC including visible imaging circuitry configured to detect visible radiation, and

an infrared radiation detector structure configured to absorb infrared radiation, said infrared detector structure comprising a membrane supported at a position spaced above said substrate, said membrane having at least one opening defined therein and configured to allow visible spectrum radiation to reach said visible imaging circuitry through said membrane; and

a periodic chopper positioned between said focal plane array and a source of visible spectrum radiation and infrared spectrum radiation;

wherein said periodic chopper comprises a color-correcting chopper having a first portion and a second portion, said first portion being configured to allow said visible spectrum radiation to be focused on said focal plane array and said second portion being configured to focus said infrared spectrum radiation on said focal plane array.

45. A multi-band radiation detection system, comprising:

a focal plane array assembly, said focal plane array assembly comprising;

a substrate, and

a plurality of multi-band detector elements, each of said plurality of multi-band detector elements comprising a membrane suspended over said substrate and read out integrated circuitry (ROIC) disposed on said substrate, said ROIC including visible imaging circuitry.