Thermal protection mechanisms for uncooled microbolometers

Patent metadata

Field	Value
Publication number	US-10520364-B2
Application number	US-201816205693-A
Country	US
Kind code	B2
Filing date	Nov 30, 2018
Priority date	Apr 12, 2017
Publication date	Dec 31, 2019
Grant date	Dec 31, 2019

Abstract

Methods and apparatus for preventing solar damage, and other heat-related damage, to uncooled microbolometer pixels. In certain examples, a thermochroic membrane that becomes highly reflective at temperatures above a certain threshold is applied over at least some of the microbolometer pixels to prevent the pixels from being damaged by excessive heat.

First claim

What is claimed is:

1. An uncooled microbolometer comprising:
a base substrate;
a plurality of pixels arranged in an array on the base substrate;
a cap layer coupled to and disposed over the base substrate, the cap layer being configured to provide a cavity between the base substrate and the cap layer, the plurality of pixels being disposed within the cavity; and
a thermally sensitive protective membrane disposed on the cap layer over a sub-array of at least some of the plurality of pixels, the thermally sensitive protective membrane including a thermochroic switch material configured to transition from a transmissive state into a reflective state in response to a temperature of thermochroic material reaching a predetermined threshold, the thermochroic material being transmissive to infrared radiation in the transmissive state and reflective to the infrared radiation in the reflective state.

2. The uncooled microbolometer of claim 1 wherein the thermochroic switch material is vanadium oxide.

3. The uncooled microbolometer of claim 2 wherein a phase of the vanadium oxide is VO 2 that undergoes a metal-insulator phase change at a temperature of approximately 67 degrees Celsius.

4. The uncooled microbolometer of claim 1 further comprising a cover layer disposed over the thermally sensitive protective membrane.

5. The uncooled microbolometer of claim 4 wherein the cap layer and the cover layer are made of silicon nitride.

6. The uncooled microbolometer of claim 1 wherein the thermally sensitive protective membrane is a continuous film disposed over all the plurality of pixels.

7. The uncooled microbolometer of claim 1 wherein the sub-array of at least some of the plurality of pixels includes a 5×5 sub-array of pixels.

8. The uncooled microbolometer of claim 1 wherein the sub-array of at least some of the plurality of pixels includes a 3×3 sub-array of pixels.

9. The uncooled microbolometer array of claim 1 wherein each pixel includes a sensor layer supported above the base substrate by at least two first supports, and an infrared absorbing layer supported above and thermally isolated from the sensor layer by at least one second support.

10. The uncooled microbolometer array of claim 9 further comprising:
a read-out integrated circuit formed in the base substrate and coupled to at least one of the at least two first supports of each pixel, the read-out integrated circuit being configured to receive and process signals from the plurality of pixels to provide output data for constructing an image.

11. The uncooled microbolometer array of claim 9 wherein the infrared absorbing layer is one of amorphous silicon and vanadium oxide.

12. The uncooled microbolometer array of claim 1 wherein the cavity is maintained under vacuum conditions.

13. An uncooled microbolometer comprising:
a base substrate;
a plurality of pixels arranged in a plurality of two-dimensional sub-arrays on the base substrate;
a cap layer coupled to and disposed over the base substrate, the cap layer being configured to provide a cavity between the base substrate and the cap layer, the plurality of pixels being disposed within the cavity; and
a thermally sensitive protective membrane disposed on the cap layer, the thermally sensitive protective membrane including a plurality of discrete portions, each portion being disposed over a corresponding one of the plurality of sub-arrays of the plurality of pixels, the thermally sensitive protective membrane including a thermochroic switch material configured to transition from a transmissive state into a reflective state in response to a temperature of thermochroic material reaching a predetermined threshold, the thermochroic material being transmissive to infrared radiation in the transmissive state and reflective to the infrared radiation in the reflective state.

14. The uncooled microbolometer of claim 13 wherein the thermochroic switch material is vanadium oxide.

15. The uncooled microbolometer of claim 13 further comprising a cover layer disposed over the thermally sensitive protective membrane.

16. The uncooled microbolometer of claim 15 wherein the cap layer and the cover layer are made of silicon nitride.

17. The uncooled microbolometer of claim 13 wherein each sub-array is a 5×5 sub-array of pixels.

18. The uncooled microbolometer of claim 13 each sub-array is a 3×3 sub-array of pixels.

19. The uncooled microbolometer array of claim 13 wherein each pixel includes a sensor layer supported above the base substrate by at least two first supports, and an infrared absorbing layer supported above and thermally isolated from the sensor layer by at least one second support.

20. The uncooled microbolometer array of claim 19 wherein the infrared absorbing layer is one of amorphous silicon and vanadium oxide.

Assignees

• Raytheon Co

Inventors

• Masini Paolo
• Devitt John William

Classifications

• B81B7/0019 Primary

  Protection against thermal alteration or destruction (B81B7/0083 takes precedence) · CPC title

• B81B3/0081

  Thermal properties · CPC title

• G01J5/06

  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 title

• G01J5/045

  Sealings; Vacuum enclosures; Encapsulated packages; Wafer bonding structures; Getter arrangements (getter arrangements per se H10W76/48, H10P36/03) · CPC title

• G01J5/0245

  for performing thermal shunt · CPC title