Method for forming uncooled infrared detector

• US 5,288,649 A
• Filed: 09/25/1992
• Issued: 02/22/1994
• Est. Priority Date: 09/30/1991
• Status: Expired due to Term

• Current Assignee: L-3 Communications Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Texas Instruments, Inc.
• Inventors: Keenan, William F.
• Primary Examiner(s): Chaudhuri, Olik
• Assistant Examiner(s): TSAI, H JEY
• Application Number:
  US07/951,928
• Time in Patent Office: 515 Days
• Field of Search: 437/3, 437/903, 437/4, 437/921, 148/DIG. 159, 257/53-56, 257/440, 257/446
• US Class Current: 438/54
• CPC Class Codes: G01J 5/20 using resistors, thermistors or semiconductors sensitive to radiation, e.g. photoconductive devices
• CPC Class Codes: H01L 27/1467 of the hybrid type
• 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

A bolometer for detecting radiation in a spectral range is described herein. The bolometer includes an integrated circuit substrate 122 and a pixel body 120 spaced from the substrate 122 by at least one pillar 124. The pixel body 120 comprises an absorber material 132, such as titanium for example, for absorbing radiation in the spectral range, which may be 7 to 12 microns for example. The absorber material 132 heats the pixel body 120 to a temperature which is proportional to the absorbed radiation. An insulating material 134 is formed over the absorber material 132. In addition, a variable resistor material 136, possible amorphous silicon for example, with an electrical resistance corresponding to the temperature of the pixel body 120 is formed over said insulating layer 134. A current flows through the variable resistor material 136 substantially parallel to the integrated circuit substrate 122 for detection. Other systems and methods are also disclosed.

Claims

1. A method of forming a bolometer cell on a semiconductor substrate comprising the steps of:

forming a temporary layer on said substrate;

forming a layer of absorber material on said temporary layer;

patterning and etching said layer of absorber material;

forming an insulating layer over said layer of absorber material;

patterning and etching said insulating layer;

forming a layer of variable resistor material over said insulating layer;

patterning and etching at least one pillar hole in said layer of variable resistor material and the underlying portion of said temporary layer;

patterning and etching said variable resistor material to form a temperature variable resistor;

forming a pillar in each of said at least one pillar holes;

forming at least two contacts from said at least two pillars to said temperature variable resistor; and

removing said temporary layer.

2. The method of claim 1 and further comprising the step of depositing a mirror material on said substrate prior to forming said temporary layer;

3. The method of claim 2 wherein said mirror material is aluminum.

4. The method of claim 1 wherein said temporary layer is polyimide.

5. The method of claim 1 and further comprising the step of at least partially sawing said substrate prior to removing said temporary layer.

6. The method of claim 1 and further comprising the step of forming a passivation layer prior to forming said layer of absorber material.

7. The method of claim 1 wherein said step of forming a layer of absorber material comprises depositing a metal.

8. The method of claim 1 wherein said step of forming a layer of variable resistor material comprises depositing amorphous silicon.

9. The method of claim 6 wherein said amorphous silicon is doped to between about 10^-6 Ω

^-1 cm^-2 and 10^-2 Ω

^-1 cm^-2.

10. A method of forming a bolometer on an integrated circuit substrate, comprising the steps of:

forming at least one pillar on said substrate;

forming a pixel body such that said pixel body is spaced from said substrate by said at least one pillar, said step of forming a pixel body comprising the steps of;

forming a region of absorber material, said absorber material comprising characteristics for absorbing radiation in a selected spectral range;

forming an insulating layer over said region of absorber material; and

forming a variable resistor region over said insulating layer, said variable resistor region with an electrical resistance corresponding to the temperature of said pixel body such that current flows through said variable resistor material and substantially parallel to said integrated circuit substrate.

11. The method of claim 10 wherein said selected spectral range is between 7 and 12 microns.

12. The method of claim 10 wherein said pixel body is spaced between about 2 and 3 microns from said substrate.

13. The method of claim 10 and further comprising the step of forming a passivation layer beneath said absorber material.

14. The method of claim 10 wherein said absorber material comprises titanium.

15. The method of claim 10 wherein said variable resistor material comprises amorphous silicon.

16. The method of claim 10 wherein said absorber material comprises characteristics for absorbing radiation in a second spectral range in addition to said selected spectral range.

17. The method of claim 16 wherein said second spectral range is visible light.

18. The method of claim 10 wherein said method comprises the steps of simultaneously forming an array of like pixel bodies.

19. A method for forming a bolometer array comprising the steps of:

providing a semiconductor substrate;

forming an array of pixel bodies, each said pixel bodies spaced from said substrate by at least one associated pillar, each said pixel body comprising;

an absorber material for absorbing radiation in said spectral range, said absorber material heating said pixel body to a temperature in proportion to said absorbed radiation;

an insulating material formed over said absorber material; and

a variable resistor material with an electrical resistance corresponding to the temperature of said pixel body such that a current flows through said variable resistor material and substantially parallel to said integrated circuit substrate, said variable resistor material formed over said insulating layer; and

forming integrated circuitry in said semiconductor substrate, said integrated circuitry coupled to said array of pixel bodies to monitor changes in resistance in said variable resistor material.

20. The method of claim 19 wherein said absorber material comprises titanium.

21. The method of claim 19 wherein said variable resistor material comprises amorphous silicon.