Infrared radiation imager having sub-pixelization and detector interdigitation

• US 20060038128A1
• Filed: 08/17/2005
• Published: 02/23/2006
• Est. Priority Date: 08/19/2004
• Status: Active Grant

• Current Assignee: DRS Network & Imaging Systems, LLC (Leonardo S.p.A.)
• Original Assignee: DRS Sensors & Targeting Systems, Inc. (Leonardo S.p.A.)
• Inventors: Molyneux, Dale E., Dawson, Larry C., D'Souza, Arvind I., Stapelbroek, Maryn G.
• Granted Patent: US 7,351,972 B2
• Time in Patent Office: Days
• US Class Current: 250/332
• CPC Class Codes: G01J 3/2803 using photoelectric array detector
• CPC Class Codes: G01J 5/20 using resistors, thermistors or semiconductors sensitive to radiation, e.g. photoconductive devices
• CPC Class Codes: G01J 5/22 Electrical features thereof
• CPC Class Codes: H01L 27/14603 Special geometry or disposition of pixel-elements, address-lines or gate-electrodes
• CPC Class Codes: H01L 27/14649 Infrared imagers
• CPC Class Codes: H01L 31/022408 for devices characterised by at least one potential jump barrier or surface barrier

Abstract

An infrared radiation (“IR”) focal plane array (“FPA”) imager includes a detector array chip containing pixels having substantially one-hundred percent operability. Each of the pixels contains a plurality of interdigitated sub-detectors, where the sub-detectors are selectively operable to provide for collection of photogenerated minority charges representative of all or substantially all of the IR radiation absorbed by the detector array chip of the FPA imager.

Claims

1. A pixel for use in a detector array of a focal plane array imager, the pixel comprising:

a plurality of interdigitated sub-detectors, wherein a first of the sub-detectors includes at least one minority charge collector electrically coupled to a first metal trace, wherein at least a second of the sub-detectors includes at least one minority charge collector electrically coupled to a second metal trace, wherein each of the minority charge collectors is included in no more than a single sub-detector, wherein each of the sub-detectors is selectively operable (i) in a selected mode to collect minority charges and (ii) in a deselected mode to act as an open circuit, and

wherein the first sub-detector and the at least second sub-detector are interdigitated in the pixel such that, if at least one of the first sub-detector and the at least second sub-detector is deselected, the selected sub-detector or sub-detectors in the pixel collect substantially all minority charges generated in the pixel resulting from absorption of optical energy in the pixel.

2. The pixel of claim 1, wherein the minority charge collectors are at least one of a p/n junction collection diode and a n/p junction collection diode.

3. The pixel of claim 1, wherein the optical energy is infrared energy.

4. The pixel of claim 1, wherein the sub-detectors are interdigitated according to at least one of expected optical spot distribution, expected diffusion length of minority charge carriers generated from the absorbed optical energy and probability of collection of the minority charges by the collectors based on locations of the collectors in the pixel in relation to locations of optical energy absorption in the pixel.

5. The pixel of claim 1, wherein each of the sub-detectors includes a plurality of collectors, wherein the collectors of each of the sub-detectors follow a substantially spiraling configuration starting from an origin point in the pixel to provide that the sub-detectors have a spiraling symmetry and are substantially circularly-shaped.

6. The pixel of claim 5, wherein the collectors constitute a plurality of sets of collectors, wherein each of the collectors in a collector set is spaced at a same radial distance from the origin point and wherein each of the collector sets is spaced at a different radial distance from the origin point.

7. The pixel of claim 5, wherein the pixel corresponds to a horizontal portion of a detector array chip having a width W and a length L, and wherein the radial distance of any of the collectors from the origin point of the pixel does not exceed about one quarter of W or L.

8. The pixel of claim 5, wherein the origin point is the center of the pixel.

9. The pixel of claim 8, wherein the collectors constitute a plurality of sets of collectors, wherein each of the collectors in a collector set is spaced at a same radial distance from the origin point and wherein each of the collector sets is spaced at a different radial distance from the origin point.

10. The pixel of claim 8, where at least four of the collectors are at the same radial distance from the center of the pixel.

11. The pixel of claim 1, wherein the collectors of the first and second sub-detectors are arranged in a 3×

3 array, and wherein the first sub-detector includes the collectors (1,1), (3,1), (1,3), (3,1) and (2,2) of the array and the second sub-detector includes the collectors (2,1), (1,2), (3,2) and (2,3) of the array.

12. The pixel of claim 1, wherein the plurality of interdigitated sub-detectors includes at least first, second, third and fourth sub-detectors, wherein the first, second, third and fourth sub-detectors are formed using first, second, third and fourth metal traces, wherein each of the first, second, third and fourth metal traces includes portions of at least a first metal layer and a second metal layer.

13. The pixel of claim 1 further comprising a plurality of minority charge collectors arranged in a 4×

4 array, wherein the plurality of the interdigitated sub-detectors includes at least first, second, third and fourth sub-detectors, and

wherein the first sub-detector includes the collectors (1,1), (1,3), (3,1) and (3,3) of the array, the second sub-detector includes the collectors (1,2), (3,2), (1,4) and (3,4) of the array, the third sub-detector includes the collectors (2,1), (4,1), (2,3) and (4,3) of the array and the fourth sub-detector includes the collectors (2,2), (4,2), (2,4) and (4,4) of the array.

14. The pixel of claim 13, wherein the first, second, third and fourth sub-detectors include first, second, third and fourth metal traces, respectively, wherein each of the metal traces includes at least a first metal layer and a second metal layer.

15. A focal plane array (“

FPA”

) in an infrared imager, wherein the FPA contains a plurality of pixels, wherein each of the pixels comprises;

a plurality of interdigitated sub-detectors, wherein a first of the sub-detectors includes at least one minority charge collector electrically coupled to a first metal trace, wherein at least a second of the sub-detectors includes at least one minority charge collector electrically coupled to a second metal trace, wherein each of the minority charge collectors is included in no more than a single sub-detector, wherein each of the sub-detectors is selectively operable (i) in a selected mode to collect minority charges and (ii) in a deselected mode to act as an open circuit, and

wherein the first sub-detector and the at least second sub-detector are interdigitated in each of the pixels such that, if at least one of the first sub-detector and the at least second sub-detector is deselected, the selected sub-detector or sub-detectors in the pixel collect substantially all minority charges generated in the pixel resulting from absorption of optical energy in the pixel.

16. The imager of claim 15, wherein the sub-detectors in each of the pixels are interdigitated according to at least one of expected optical spot distribution, expected diffusion length of minority charge carriers generated from the absorbed optical energy and probability of collection of the minority charges by the collectors based on locations of the collectors in the pixel in relation to locations of optical energy absorption in the pixel.

17. A method of imaging a scene comprising:

providing a focal plane array (“

FPA”

) including a plurality of pixels, wherein each of the pixels in the FPA includes;

a plurality of interdigitated sub-detectors, wherein a first of the sub-detectors includes at least one minority charge collector electrically coupled to a first metal trace, wherein at least a second of the sub-detectors includes at least one minority charge collector electrically coupled to a second metal trace, wherein each of the minority charge collectors is included in no more than a single sub-detector, wherein each of the sub-detectors is selectively operable (i) in a selected mode to collect minority charges and (ii) in a deselected mode to act as an open circuit;

operating any sub-detector in the FPA having an inoperable minority charge collector in the deselected mode and operating all other sub-detectors in the selected mode; and

for each of the pixels in the FPA, collecting at the sub-detectors operating in selected mode all or substantially all minority charges generated resulting from absorption of optical energy in the pixel.

18. The method of claim 17 further comprising:

for each of the pixels in the FPA, after an integration interval summing the minority charges collected at the sub-detectors operating in selected mode.

19. The method of claim 17, wherein the minority charge collectors are at least one of a p/n junction collection diode and a n/p junction collection diode.

20. The method of claim 17, wherein the optical energy is infrared energy.