Optically transitioning thermal detector structures

• US 8,513,605 B2
• Filed: 04/28/2010
• Issued: 08/20/2013
• 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: Beratan, Howard
• Primary Examiner(s): Sung, Christine
• Application Number:
  US12/799,628
• Publication Number:
  US 20110266445A1
• Time in Patent Office: 1,210 Days
• Field of Search: 250/338.4, 250/338.1
• US Class Current: 250/338.4
• CPC Class Codes: G01J 1/02 Details
• CPC Class Codes: G01J 1/0204 Compact construction
• CPC Class Codes: G01J 1/04 Optical or mechanical part supplementary adjustable parts
• CPC Class Codes: G01J 1/0411 using focussing or collimating elements, i.e. lenses or mirrors; Aberration correction
• CPC Class Codes: G01J 1/0429 using polarisation elements
• CPC Class Codes: G01J 1/0488 with spectral filtering
• CPC Class Codes: G01J 2005/065 by shielding
• CPC Class Codes: G01J 4/04 Polarimeters using electric detection means G01J4/02 takes precedence
• CPC Class Codes: G01J 5/02 Constructional details
• CPC Class Codes: G01J 5/0215 Compact construction
• CPC Class Codes: G01J 5/023 Particular leg structure or construction or shape; Nanotubes
• CPC Class Codes: G01J 5/024 Special manufacturing steps or sacrificial layers or layer structures
• CPC Class Codes: G01J 5/06 Arrangements for eliminating effects of disturbing radiation; Arrangements for compensating changes in sensitivity for adjusting of solid angle of collected radiation G01J5/07; means for wavelength selection G01J5/0801
• CPC Class Codes: G01J 5/08 Optical arrangements
• CPC Class Codes: G01J 5/0802 Optical filters
• CPC Class Codes: G01J 5/0806 Focusing or collimating elements, e.g. lenses or concave mirrors
• CPC Class Codes: G01J 5/20 using resistors, thermistors or semiconductors sensitive to radiation, e.g. photoconductive devices
• CPC Class Codes: G01J 5/59 using polarisation; Details thereof
• CPC Class Codes: G01N 21/3581 using far infrared light; using Terahertz radiation
• CPC Class Codes: H01L 27/14621 Colour filter arrangements
• CPC Class Codes: H01L 27/14627 : Microlenses
• CPC Class Codes: H01L 27/14669 : Infrared imagers
• 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: H10N 15/00 : Thermoelectric devices without a junction of dissimilar materials; Thermomagnetic devices, e.g. using the Nernst-Ettingshausen effect integrated devices or assemblies of multiple devices H10N19/00

Abstract

A thermal absorption structure of a radiation thermal detector element may include an optically transitioning material configured such that optical conductivity of the thermal absorption structure is temperature sensitive and such that the detector element absorbs radiation less efficiently as its temperature increases, thus reducing its ultimate maximum temperature.

Claims

1. A thermal detector element comprising:

an optically transitioning thermal absorption structure, the thermal detector element being configured to sense radiation falling incident thereon by measuring at least one property of the thermal absorption structure that changes value with temperature, the thermal absorption structure being provided with one or more optically transitioning materials that are an integral part of the thermal absorption structure itself; and

a substrate;

where the thermal absorption structure is a microbolometer pixel membrane structure that provides a membrane suspended above the substrate that is configured to absorb radiation incident thereon, the microbolometer pixel membrane structure being disposed in spaced relationship above the substrate to define a cavity therebetween; and

where the one or more optically transitioning materials are an integral part of the membrane itself; and

where the microbolometer pixel membrane structure comprises an electrically conductive thermally-electrically active layer and an optically transitioning radiation absorbing layer comprising one or more optically transitioning materials and that is separate from the electrically conductive thermally-electrically active layer, each of the electrically conductive thermally-electrically active layer and optically transitioning radiation absorbing layer being an integral part of the membrane itself; and

where the substrate of the thermal detector element further comprises read out integrated circuitry (ROTC) electrically coupled to form a current path across at least a portion of the electrically conductive thermally-electrically active layer.

2. The thermal detector element of claim 1, where the electrically conductive thermally-electrically active layer is disposed in a position between the optically transitioning radiation absorbing layer and the substrate.

3. The thermal 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.

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

5. The thermal detector element of claim 1, where the optically transitioning material becomes increasingly reflective of incident radiation with increasing temperature such that the thermal absorption structure absorbs a greater amount of incident radiation at a first temperature than the thermal absorption structure absorbs at a second temperature when the second temperature is higher than the first temperature.

6. The thermal detector element of claim 5, where the optically transitioning material becomes increasingly reflective of incident radiation with increasing temperature such that the thermal absorption structure absorbs a greater portion of the total incident radiation at a first temperature than the thermal absorption structure absorbs at a second temperature that is higher than the first temperature.

7. The thermal detector element of claim 5, further comprising a reflective layer disposed on the surface of the substrate between the thermal absorption structure and the substrate;

where the thermal detector element is configured to receive incident radiation on a first side of the microbolometer pixel membrane structure that faces away from the cavity; and

where the optically transitioning material allows a greater portion of the total received incident radiation to be transmitted through the microbolometer pixel membrane structure to the reflective layer of the substrate at a first temperature than the optically transitioning material allows to be transmitted through the microbolometer pixel membrane structure at a second temperature that is higher than the first temperature.

8. The thermal detector element of claim 1, where the thermal detector element is an uncooled infrared detector element.

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

a device wafer, the device wafer comprising the focal plane array assembly of claim 8; 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.

10. The wafer-level packaged focal plane array assembly of claim 9, 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.

11. The thermal detector element of claim 1, where the microbolometer pixel membrane structure is electrically connected to the ROTC by electrically conductive interconnects that are electrically coupled to pass current through at least a portion of the integral electrically conductive thermally-electrically active layer of the membrane;

and where a discontinuity is defined in the integral optically transitioning radiation absorbing layer of the membrane to prevent electrical conductivity through the integral optically transitioning radiation absorbing layer between the electrically conductive interconnects.

12. The thermal detector element of claim 11, where the discontinuity is defined as a slit in position between the electrically conductive interconnects that acts to prevent electrical conductivity through the integral optically transitioning radiation absorbing layer between the electrically conductive interconnects.

13. A focal plane array assembly, comprising:

a plurality of individual thermal detector elements arranged as an array, at least a portion of the plurality of individual thermal detector elements comprising an optically transitioning thermal absorption structure and being configured to sense radiation falling incident thereon by measuring at least one property of the thermal absorption structure that changes value with temperature, the thermal absorption structure being provided with one or more optically transitioning materials that are an integral part of the thermal absorption structure itself;

where each of the portion of individual thermal detector elements further comprises a substrate;

where the thermal absorption structure of each of the portion of individual thermal detector elements is a microbolometer pixel membrane structure that provides a membrane suspended above the substrate that is configured to absorb radiation incident thereon, the microbolometer pixel membrane structure of each of the microbolometer pixel membrane structures being disposed in spaced relationship above the substrate to define a cavity therebetween with the one or more optically transitioning materials being an integral part of the membrane itself; and

where the microbolometer pixel membrane structure of each of the portion of individual thermal detector elements comprises an electrically conductive thermally-electrically active layer and an optically transitioning radiation absorbing layer comprising one or more optically transitioning materials and that is separate from the electrically conductive thermally-electrically active layer, each of the electrically conductive thermally-electrically active layer and optically transitioning radiation absorbing layer being an integral part of the membrane itself; and

where the substrate of each of the portion of individual thermal detector elements further comprises read out integrated circuitry (ROTC) electrically coupled to form a current path across at least a portion of the electrically conductive thermally-electrically active layer.

14. The focal plane array assembly of claim 13, where the electrically conductive thermally-electrically active layer of each of the portion of individual thermal detector elements is disposed in a position between the radiation absorbing layer and the substrate.

15. The focal plane array assembly of claim 13, 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.

16. The focal plane array assembly of claim 13, wherein the optically transitioning material comprises thermochromic vanadium oxide or doped thermochromic vanadium oxide.

17. The focal plane array assembly of claim 13, where the optically transitioning material becomes increasingly reflective of incident radiation with increasing temperature such that the thermal absorption structure of each of the portion of individual thermal detector elements absorbs a greater amount of incident radiation at a first temperature than the thermal absorption structure absorbs at a second temperature when the second temperature is higher than the first temperature.

18. The focal plane array assembly of claim 17, where the optically transitioning material becomes increasingly reflective of incident radiation with increasing temperature such that the thermal absorption structure of each of the portion of individual thermal detector elements absorbs a greater portion of the total incident radiation at a first temperature than the thermal absorption structure absorbs at a second temperature that is higher than the first temperature.

19. The focal plane array assembly of claim 17, where of each of the portion of individual thermal detector elements further comprises a reflective layer disposed on the surface of the substrate between the thermal absorption structure and the substrate;

where the thermal detector element is configured to receive incident radiation on a first side of the microbolometer pixel membrane structure that faces away from the cavity; and

where the optically transitioning material allows a greater portion of the total received incident radiation to be transmitted through the microbolometer pixel membrane structure to the reflective layer of the substrate at a first temperature than the optically transitioning material allows to be transmitted through the microbolometer pixel membrane structure at a second temperature that is higher than the first temperature.

20. The focal plane array assembly of claim 13, where each of the portion of individual thermal detector elements is an uncooled infrared detector element.

21. The focal plane array assembly of claim 13, where the microbolometer pixel membrane structure of each of the portion of individual thermal detector elements is electrically connected to the ROIC by electrically conductive interconnects that are electrically coupled to pass current through at least a portion of the integral electrically conductive thermally-electrically active layer of the membrane;

and where a discontinuity is defined in the integral optically transitioning radiation absorbing layer of the membrane to prevent electrical conductivity through the integral optically transitioning radiation absorbing layer between the electrically conductive interconnects.

22. The focal plane array assembly of claim 21, where the discontinuity is defined as a slit in position between the electrically conductive interconnects that acts to prevent electrical conductivity through the integral optically transitioning radiation absorbing layer between the electrically conductive interconnects.

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

forming a plurality of individual thermal detector elements arranged as an array, each of the plurality of individual detector elements comprising an optically transitioning thermal absorption structure and being configured to sense radiation falling incident thereon by measuring at least one property of the thermal absorption structure that changes value with temperature, the thermal absorption structure being provided with one or more optically transitioning materials that are formed as an integral part of the thermal absorption structure itself; and

providing a substrate;

where the thermal absorption structure of each of the portion of individual thermal detector elements is a microbolometer pixel membrane structure that provides a membrane suspended above the substrate that is configured to absorb radiation incident thereon, the microbolometer pixel membrane structure of each of the microbolometer pixel membrane structures being disposed in spaced relationship above the substrate to define a cavity therebetween with the one or more optically transitioning material components being formed as an integral part of the membrane itself; and

wherein forming the plurality of individual thermal detector elements comprises;

forming an electrically conductive thermally-electrically active layer and an optically transitioning radiation absorbing layer comprising one or more optically transitioning materials and that is separate from the active layer, and such that each of the electrically conductive thermally-electrically active layer and optically transitioning radiation absorbing layer are formed as an integral part of the membrane itself for the microbolometer pixel membrane structure of each of the individual thermal detector elements,

providing the substrate with read out integrated circuitry (ROIC), and

electrically coupling the ROIC to form a current path across at least a portion of the electrically conductive thermally-electrically active layer.

24. The method of claim 23, further comprising forming the electrically conductive thermally-electrically active layer of each of the portion of individual thermal detector elements in a position between the radiation absorbing layer and the substrate.

25. The method of claim 23, 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.

26. The method of claim 23, wherein the optically transitioning material comprises thermochromic vanadium oxide or doped thermochromic vanadium oxide.

27. The method of claim 23, where the optically transitioning material becomes increasingly reflective of incident radiation with increasing temperature such that the thermal absorption structure of each of the portion of individual thermal detector elements absorbs a greater amount of incident radiation at a first temperature than the thermal absorption structure absorbs at a second temperature when the second temperature is higher than the first temperature.

28. The method of claim 27, where the optically transitioning material becomes increasingly reflective of incident radiation with increasing temperature such that the thermal absorption structure of each of the portion of individual thermal detector elements absorbs a greater portion of the total incident radiation at a first temperature than the thermal absorption structure absorbs at a second temperature that is higher than the first temperature.

29. The method of claim 27, where the method further comprises:

forming each of the portion of individual thermal detector elements with a configuration to receive incident radiation on a first side of the microbolometer pixel membrane structure that faces away from the cavity; and

forming a reflective layer on the surface of the substrate of each of the portion of individual thermal detector elements between the microbolometer pixel membrane structure and the substrate such that the optically transitioning material allows a greater portion of the total received incident radiation to be transmitted through the microbolometer pixel membrane structure to the reflective layer of the substrate at a first temperature than the optically transitioning material allows to be transmitted through the microbolometer pixel membrane structure at a second temperature that is higher than the first temperature.

30. The method of claim 23, further comprising:

forming each of the portion of individual thermal detector elements as an uncooled infrared detector.

31. The method of claim 23, further comprising:

providing a device wafer and forming the forming the plurality of individual thermal 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.

32. The method of claim 31, 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.

33. The method of claim 23, further comprising electrically connecting the microbolometer pixel membrane structure of each of the portion of individual thermal detector elements to the ROIC by electrically conductive interconnects that are electrically coupled to pass current through at least a portion of the integral electrically conductive thermally-electrically active layer of the membrane;

and forming a discontinuity in the integral optically transitioning radiation absorbing layer of the membrane to prevent electrical conductivity through the integral optically transitioning radiation absorbing layer between the electrically conductive interconnects.

34. The method of claim 33, further comprising forming the discontinuity as a slit in position between the electrically conductive interconnects to prevent electrical conductivity through the integral optically transitioning radiation absorbing layer between the electrically conductive interconnects.