Pixel-level optically transitioning filter elements for detector devices

• US 8,227,755 B2
• Filed: 04/28/2010
• Issued: 07/24/2012
• Est. Priority Date: 04/28/2010
• Status: Active Grant

• Current Assignee: DRS Network & Imaging Systems, LLC (Leonardo S.p.A.)
• Original Assignee: L-3 Communications Corporation (L3Harris Technologies, Inc.)
• Inventors: Fagan, Thomas P. III, Brady, John F., Schimert, Thomas R., Syllaios, Athanasios J.
• Primary Examiner(s): Gaworecki, Mark R
• Application Number:
  US12/799,629
• Publication Number:
  US 20110266441A1
• Time in Patent Office: 818 Days
• Field of Search: 250/338.1, 250/338.4, 250/339.02, 257/E21.499, 438/54, 438/55
• US Class Current: 250/338.4
• CPC Class Codes: H01L 27/14618 Containers
• CPC Class Codes: H01L 27/14625 Optical elements or arrangements associated with the device
• CPC Class Codes: H01L 27/14627 Microlenses
• CPC Class Codes: H01L 27/14632 Wafer-level processed structures
• CPC Class Codes: H01L 27/14649 Infrared imagers
• CPC Class Codes: H01L 27/1465 of the hybrid type
• CPC Class Codes: H01L 27/14683 Processes or apparatus peculiar to the manufacture or treatment of these devices or parts thereof not peculiar thereto H01L21/00
• CPC Class Codes: H01L 27/14685 Process for coatings or optical elements
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 31/02325 the optical elements not being integrated nor being directly associated with the device

Abstract

Optically transitioning pixel-level filtering using a multi-level structure that includes an isolated optically transitioning filter element that is suspended over a corresponding radiation detector element in a one-to-one relationship to provide, for example, one or more features such as spectral detection and/or selective radiation immunity.

Claims

1. An individual radiation detector element, comprising:

a substrate;

radiation detector circuitry disposed in or on the substrate, the radiation detector circuitry configured to absorb radiation; and

a pixel-level optically transitioning filter element comprising at least one optically transitioning material and being suspended over and above the radiation detector circuitry of the individual detector element and not suspended over and above the radiation detection circuitry of another radiation detector element such that the pixel-level optically transitioning filter element only filters radiation destined for the individual radiation detector element.

2. The radiation detector element of claim 1, wherein the optically transitioning material comprises an undoped or doped thermochromic material, the thermochromic material including at least one of germanium-antimony-tellurium, vanadium oxide, niobium oxide, tantalum oxide, Ti₂O₃, Fe₃O₄, Mo₉O₂₆, or a combination thereof.

3. The radiation detector element of claim 1, wherein the optically transitioning material comprises thermochromic vanadium oxide or doped thermochromic vanadium oxide.

4. The radiation detector element of claim 1, wherein the radiation detector element is an uncooled infrared radiation detector element;

wherein the radiation detection circuitry comprises a microbolometer pixel membrane structure configured to absorb infrared radiation, the microbolometer pixel membrane structure comprising a membrane material supported at a position spaced above the substrate by at least two spaced electrically conductive interconnects;

wherein the pixel-level optically transitioning filter element is a monolithically fabricated optical element suspended over and above the membrane material of the microbolometer pixel membrane structure by at least two electrically and thermally insulating filter element support interconnects that are at least partially aligned to and supported by the at least two electrically conductive interconnects.

5. The radiation detector element of claim 4, where the substrate includes read out integrated circuitry (ROIC);

and wherein the at least two spaced electrically conductive interconnects are electrically coupled to the ROIC.

6. The radiation detector element of claim 5, further comprising a thermal isolation leg extending between each of the filter element support interconnects and the pixel-level optically transitioning filter element to increase thermal isolation of the pixel-level optically transitioning filter element, each of the thermal isolation legs being defined in the optically transitioning material of the pixel-level optically transitioning filter element.

7. The radiation detector element of claim 1, wherein the optically transitioning material of the pixel-level optically transitioning filter element is patterned into a linear diffraction grating to from a polarizing filter element.

8. The radiation detector element of claim 1, further comprising at least one additional pixel-level optical element suspended in the radiation path between the pixel-level optically transitioning filter element and the radiation detector circuitry.

9. The radiation detector element of claim 1, further comprising at least one additional pixel-level optical element suspended over and above the pixel-level optically transitioning filter element.

10. A focal plane array assembly, comprising:

a plurality of individual detector elements arranged as an array, each of the plurality of individual detector elements comprising;

a substrate, and

radiation detector circuitry disposed in or on the substrate, the detector circuitry configured to absorb radiation;

where at least a portion of the plurality of individual detector elements of the focal plane array each further comprises a pixel-level optically transitioning filter element comprising at least one optically transitioning material and being suspended over and above the radiation detector circuitry of the individual detector element and not suspended over and above the radiation detection circuitry of any other radiation detector element of the focal plane array such that the pixel-level optically transitioning filter element only filters radiation destined for the individual radiation detector element.

11. The focal plane array assembly of claim 10, wherein the optically transitioning material comprises an undoped or doped thermochromic material, the thermochromic material including at least one of germanium-antimony-tellurium, vanadium oxide, niobium oxide, tantalum oxide, Ti₂O₃, Fe₃O₄, Mo₉O₂₆, or a combination thereof.

12. The focal plane array assembly of claim 10, wherein the optically transitioning material comprises thermochromic vanadium oxide or doped thermochromic vanadium oxide.

13. The focal plane array assembly of claim 10, wherein at least a portion of the individual detector elements of the focal plane array are uncooled infrared detector elements;

wherein the radiation detection circuitry of each uncooled infrared detector element comprises a microbolometer pixel membrane structure configured to absorb infrared radiation, the microbolometer pixel membrane structure comprising a membrane material supported at a position spaced above the substrate by at least two spaced electrically conductive interconnects;

wherein the pixel-level optically transitioning filter element of each uncooled infrared detector element is a. monolithically fabricated optical element suspended over and above the membrane material of the microbolometer pixel membrane structure by at least two electrically and thermally insulating filter element support interconnects that are at least partially aligned to and supported by the at least two electrically conductive interconnects.

14. The focal plane array assembly of claim 13, wherein the substrate of each uncooled detector element includes read out integrated circuitry (ROIC);

and wherein the at least two spaced electrically conductive interconnects of each uncooled infrared detector element are electrically coupled to the ROIC of the infrared detector element.

15. The focal plane array assembly of claim 14, further comprising a thermal isolation leg extending between each of the filter element support interconnects and the pixel-level optically transitioning filter element of each uncooled infrared detector element to increase thermal isolation of the pixel-level optically transitioning filter element, each of the thermal isolation legs being defined in the optically transitioning material of the pixel-level optically transitioning filter element.

16. The focal plane array assembly of claim 10, wherein the optically transitioning material of each pixel-level optically transitioning filter element is patterned into a linear diffraction grating to from a polarizing filter element.

17. The focal plane array assembly of claim 10, wherein the optically transitioning material of at least one pixel-level optically transitioning filter element of the array is patterned into a first linear diffraction grating to from first type of polarizing filter element;

and wherein the optically transitioning material of at least one other pixel-level optically transitioning filter element of the array is patterned into a second and different linear diffraction grating to from second and different type of polarizing filter element.

18. The focal plane array assembly of claim 10, further comprising at least one additional pixel-level optical element suspended in the radiation path between the pixel-level optically transitioning filter element and the radiation detector circuitry of each of the plurality of individual detector elements.

19. The focal plane array assembly of claim 10, further comprising at least one additional pixel-level optical element suspended over and above the pixel-level optically transitioning filter element focal plane array assembly of each of the plurality of individual detector elements.

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

a device wafer, the device wafer comprising the focal plane array assembly of claim 10; and

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

21. The wafer-level packaged focal plane array assembly of claim 20, wherein the lid wafer is sealingly assembled to the device wafer and contains a vacuum therebetween to form a wafer-level packaged focal plane array assembly.

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

providing a substrate;

forming a plurality of individual detector elements arranged as an array, each of the plurality of individual detector elements comprising;

a substrate, and

radiation detector circuitry disposed in or on the substrate, the detector circuitry configured to absorb radiation; and

forming a pixel-level optically transitioning filter element comprising at least one optically transitioning material suspended over and above the radiation detector circuitry of each of at least a portion of the plurality of individual detector elements of the focal plane array such that each of the pixel-level optically transitioning filter elements is suspended over and above the radiation detector circuitry of the individual detector element and not suspended over and above the radiation detection circuitry of any other radiation detector element of the focal plane array, and such that the pixel-level optically transitioning filter element only filters radiation destined for the individual radiation detector element.

23. The method of claim 22, wherein the optically transitioning material comprises an undoped or doped thermochromic material, the thermochromic material including at least one of germanium-antimony-tellurium, vanadium oxide, niobium oxide, tantalum oxide, Ti₂O₃, Fe₃O₄, Mo₉O₂₆, or a combination thereof.

24. The method of claim 22, wherein the optically transitioning material comprises thermochromic vanadium oxide or doped thermochromic vanadium oxide.

25. The method of claim 22, wherein at least a portion of the individual detector elements of the focal plane array are uncooled infrared detector elements;

wherein the radiation detection circuitry of each uncooled infrared detector element comprises a microbolometer pixel membrane structure configured to absorb infrared radiation, the microbolometer pixel membrane structure comprising a membrane material supported at a position spaced above the substrate by at least two spaced electrically conductive interconnects; and

wherein the method further comprises monolithically fabricating the pixel-level optically transitioning filter element of each uncooled infrared detector element suspended over and above the membrane material of the microbolometer pixel membrane structure by at least two electrically and thermally insulating filter element support interconnects that are at least partially aligned to and supported by the at least two electrically conductive interconnects.

26. The method of claim 22, further comprising fabricating a thermal isolation leg extending between each of the filter element support interconnects and the pixel-level optically transitioning filter element of each uncooled infrared detector element to increase thermal isolation of the pixel-level optically transitioning filter element, each of the thermal isolation legs being defined in the optically transitioning material of the pixel-level optically transitioning filter element.

27. The method of claim 22, further comprising patterning the optically transitioning material of each pixel-level optically transitioning filter element into a linear diffraction grating to from a polarizing filter element.

28. The method of claim 22, further comprising forming at least one additional pixel-level optical element suspended in the radiation path between the pixel-level optically transitioning filter element and the radiation detector circuitry of each of the plurality of individual detector elements.

29. The method of claim 22, further comprising forming at least one additional pixel-level optical element suspended over and above the pixel-level optically transitioning filter element focal plane array assembly of each of the plurality of individual detector elements.

30. The method of claim 22, further comprising:

providing a device wafer and forming the forming the plurality of individual detector elements arranged as an array on the device wafer;

providing a lid wafer, the lid wafer being at least partially transmissive of the incident radiation; and

assembling the lid wafer to the device wafer such that the lid wafer allows the incident radiation to reach the focal plane array assembly through the lid wafer.

31. The method of claim 30, further comprising sealingly assembling the lid wafer to the device wafer with a vacuum therebetween to form a wafer-level packaged focal plane array assembly.