Systems and methods for enhanced bolometer response

Patent metadata

Field	Value
Publication number	US-9945729-B2
Application number	US-201514730116-A
Country	US
Kind code	B2
Filing date	Jun 3, 2015
Priority date	Jun 4, 2014
Publication date	Apr 17, 2018
Grant date	Apr 17, 2018

Abstract

Systems and methods may be provided for forming enhanced infrared absorption microbolometers. An enhanced infrared absorption microbolometer may include a metal cap formed from a thin layer of oxidizing metal such as titanium and/or a titanium oxide. The metal cap may be formed within a bridge portion of the microbolometer. The bridge portion may include other layers such as first and second absorber layers disposed on opposing sides of a layer of temperature sensitive resistive material. The layer of temperature sensitive resistive material may be located between the metal cap and a reflecting metal layer formed on a readout integrated circuit for the microbolometer.

First claim

What is claimed is:

1. A microbolometer, comprising:
a bridge, comprising:
a temperature sensitive resistive layer;
one or more first absorbing dielectric layers above the temperature sensitive resistive layer;
one or more second absorbing dielectric layers below the temperature sensitive resistive layer;
one or more metal layers electrically isolated from the temperature sensitive resistive layer and above the one or more first absorber dielectric layers and/or below the one or more second absorber dielectric layers; and
a dielectric layer disposed on each of the one or more metal layers, wherein each of the metal layers is between the dielectric layer and one of the first absorbing dielectric layers or one of the second absorbing dielectric layers.

2. The microbolometer of claim 1 , wherein the one or more metal layers comprise a metal that is disposed at or near a top surface of the bridge and/or at or near a bottom surface of the bridge.

3. The microbolometer of claim 1 , wherein the one or more metal layers comprise one or more transition metals.

4. The microbolometer of claim 1 , wherein the one or more metal layers comprise titanium.

5. The microbolometer of claim 1 , wherein the one or more metal layers include a stack of a transition metal and an oxide of the transition metal.

6. The microbolometer of claim 5 , wherein the one or more metal layers includes a stack of titanium and titanium oxide.

7. The microbolometer of claim 1 , wherein the one or more metal layers have a thickness of between 10 Angstroms and 1500 Angstroms, and wherein the one or more metal layers comprise a first plurality of metal layers below the temperature sensitive resistive layer.

8. The microbolometer of claim 7 , wherein:
the temperature sensitive resistive layer comprises a vanadium oxide, nickel oxide, alpha-silicon, alpha-SiGe, titanium oxide, molybdenum oxide, and/or a diode element;
the microbolometer is one of a plurality of microbolometers that form a focal plane array; and
the one or more metal layers further comprise a second plurality of metal layers above the temperature sensitive resistive layer.

9. An infrared camera, comprising:,
a focal plane array comprising the microbolometer of claim 1 ; and
a readout integrated circuit, wherein the bridge is coupled to and suspended above the readout integrated circuit by at least one leg, and wherein the temperature sensitive resistive layer is interposed between the metal layer and the readout integrated circuit.

10. A microbolometer, comprising:
a bridge, comprising:
a first dielectric layer;
a first metal layer formed over the first dielectric layer;
a second dielectric layer formed over the first metal layer, wherein the second dielectric layer fully or partially encapsulates the first metal layer;
a temperature sensitive resistive layer; and
one or more absorbing dielectric layers above the temperature sensitive resistive layer.

11. The microbolometer of claim 10 , further comprising:
a second metal layer formed over a top absorbing dielectric layer; and
a third dielectric layer that fully or partially encapsulates the second metal layer.

12. The microbolometer of claim 10 , further comprising:
one or more absorbing dielectric layers below the temperature sensitive resistive layer.

13. A method, comprising:
forming a first metal layer on a readout integrated circuit substrate;
forming a sacrificial layer on the first metal layer;
forming one or more first absorber layers over the sacrificial layer;
forming a temperature sensitive resistive layer on the one or more first absorber layers;
forming one or more second absorber layers over the temperature sensitive resistive layer;
forming a second metal layer between the sacrificial layer and the first absorber layers and/or over the second absorber layers;
forming a dielectric layer between the second metal layer and the sacrificial layer and/or over the second absorber layers; and
removing the sacrificial layer to form a microbolometer.

14. The method of claim 13 , further comprising removing portions of the second metal layer.

15. The method of claim 14 , wherein the removing comprises etching the second metal layer.

16. The method of claim 14 , wherein the removing comprises lifting off the portions of the second metal layer.

17. The method of claim 13 , further comprising etching and/or lift off of the temperature sensitive resistive layer.

18. The method of claim 17 , further comprising:
depositing a leg metal layer on the one or more first absorber layers; and
etching and/or lift off of the leg metal layer.

19. The method of claim 13 , wherein the temperature sensitive resistive layer comprises a vanadium oxide and wherein the second metal layer comprises a titanium layer having a thickness of between 10 Angstroms and 1500 Angstroms.

20. The method of claim 13 , further comprising:
prior to depositing the second metal layer, performing etching operations to define bridge portions and leg portions of an array of microbolometers.

21. An imaging device, comprising:
an array of microbolometers; and
a readout integrated circuit, wherein each of the microbolometers is suspended over associated processing circuitry in the readout integrated circuit by at least one metal leg and wherein each microbolometer includes:
a first absorber layer,
a second absorber layer,
a temperature sensitive resistive layer disposed between the first absorber layer and the second absorber layer,
an infrared spectral absorption enhancing metal layer formed on the first absorber layer, wherein the second absorber layer is disposed closer to the readout integrated circuit than the first absorber layer; and
a dielectric layer formed on the infrared spectral absorption enhancing metal layer, wherein the dielectric layer fully or partially encapsulates the infrared spectral absorption enhancing metal layer.

22. The imaging device of claim 21 , wherein the infrared spectral absorption enhancing metal layer comprises a titanium layer having a thickness of between 10 Angstroms and 1500 Angstroms.

23. A method of using the imaging device of claim 21 , comprising:
providing a bias voltage to each of the microbolometers from the readout integrated circuit; and
receiving a signal from each of the microbolometers at the readout integrated circuit, wherein the signal from each microbolometer corresponds to an amount of infrared light absorbed by that microbolometer.

Assignees

• Flir Systems

Inventors

• Cannata Robert F
• Peters Kevin
• Franklin Patrick
• Kurth Eric A
• Dale James L
• Marx Tommy
• Shott Craig
• Salafian Reza
• Bornfreund Richard E
• Kothari Saumya

Classifications

• G01J2005/0077

  Imaging · CPC title

• G01J5/24 Primary

  Use of specially adapted circuits, e.g. bridge circuits · CPC title

• G01J5/024

  Special manufacturing steps or sacrificial layers or layer structures · CPC title

• G01J5/046 Primary

  Materials; Selection of thermal materials · CPC title

• G01J5/0853

  having infrared absorbers other than the usual absorber layers deposited on infrared detectors like bolometers, wherein the heat propagation between the absorber and the detecting element occurs within a solid · CPC title