Microbolometer for infrared detector or Terahertz detector and method for manufacturing the same

• US 20110315981A1
• Filed: 06/24/2011
• Published: 12/29/2011
• Est. Priority Date: 06/24/2010
• Status: Active Grant

• Current Assignee: University of Electronic Science and Technology of China
• Original Assignee: University of Electronic Science and Technology of China
• Inventors: Jiang, Yadong, Xu, Xiangdong
• Granted Patent: US 9,212,950 B2
• Time in Patent Office: Days
• US Class Current: 257/43
• CPC Class Codes: G01J 5/02 Constructional details
• CPC Class Codes: G01J 5/023 Particular leg structure or construction or shape; Nanotubes
• CPC Class Codes: G01J 5/04 Casings
• CPC Class Codes: G01J 5/046 Materials; Selection of thermal materials
• CPC Class Codes: G01J 5/20 using resistors, thermistors or semiconductors sensitive to radiation, e.g. photoconductive devices

Abstract

A microbolometer includes a micro-bridge structure for uncooling infrared or terahertz detectors. The thermistor and light absorbing materials of the micro-bridge structure are the vanadium oxide-carbon nanotube composite film formed by one-dimensional carbon nanotubes and two-dimensional vanadium oxide film. The micro-bridge is a three-layer sandwich structure consisting of a layer of amorphous silicon nitride base film as the supporting and insulating layer of the micro-bridge, a layer or multi-layer of vanadium oxide-carbon nanotube composite film in the middle of the micro-bridge as the heat sensitive and light absorbing layer of the microbolometer, and a layer of amorphous silicon nitride top film as the stress control layer and passivation of the heat sensitive film. The microbolometer and method for manufacturing the same can overcome the shortcomings of the prior art, improve the performance of the device, reduce the cost of raw materials and is suitable for large-scale industrial production.

Claims

1. A microbolometer, comprising a micro-bridge structure, wherein a thermistor material and a light absorbing material of said micro-bridge structure are vanadium oxide-carbon nanotube composite film formed by one-dimensional carbon nanotubes and two-dimensional vanadium oxide film.

2. The microbolometer, as recited in claim 1, wherein said micro-bridge structure is a three-layer sandwich structure consisting of a first layer of amorphous silicon nitride film as a supporting and insulating layer of said micro-bridge, a layer or multi-layer of vanadium oxide-carbon nanotube composite film provided on the first amorphous silicon nitride film as a heat sensitive and light absorbing layer of said microbolometer, and a second layer of amorphous silicon nitride film provided on the vanadium oxide-carbon nanotube composite film as a passivation layer of said heat sensitive film and a stress control layer.

3. A method for manufacturing a microbolometer, comprising the steps of:

(A) cleaning a silicon substrate, depositing a layer of amorphous silicon dioxide film as a passivation layer;

(B) depositing a layer of metal aluminum on a surface of the silicon dioxide passivation layer as a reflecting layer of a micro-bridge;

(C) photolithographing the patterns of the bridge piers of the suspended micro-bridge on a surface of the metal aluminum, and etching the metal aluminum to the silicon dioxide passivation layer, thus forming micro-bridge pier holes and metal aluminum islands;

(D) coating a layer of photosensitive polyimide film in a spin manner on the surfaces of the metal aluminum islands;

(E) photolithographing the polyimide film to form polyimide film islands and pier holes of the suspended micro-bridge, and then making the imine treatment;

(F) depositing a layer of amorphous silicon nitride film on the surfaces of the polyimide film islands and the pier holes as a supporting and insulating material of the micro-bridge, and then preparing a vanadium oxide-carbon nanotube composite film;

(G) depositing a layer of metal and patterning the metal, thus forming electrodes of the device;

(H) depositing a layer of amorphous silicon nitride film on the surfaces of the metal electrodes and the vanadium oxide-carbon nanotube composite film as a passivation layer of the electrodes and the heat sensitive film and a stress control layer of the device;

(I) photolithographing a pattern of the suspended micro-bridge on a surface of the composite film, etching the composite film to the polyimide layer, thus forming a bridge deck, bridge legs and bridge piers of the suspended micro-bridge; and

(J) removing the polyimide film at a bottom of the pattern of the bridge deck and the bridge legs to form the cavity, thus obtaining the microbolometer.

4. The method, as recited in claim 3, wherein in step (F), the preparation of the vanadium oxide-carbon nanotube composite film comprises:

(F1) cleaning the substrate, and drying the cleaned substrate;

(F2) firstly putting a prepared carbon nanotubes into a beaker, mixing the carbon nanotubes with an organic solvent and ultrasonically dispersing, and then moving a dispersion liquid onto a surface of the cleaned substrate, evaporating the solvent, thus forming a reticular interconnected carbon nanotube film;

(F3) putting the substrate with the dispersed carbon nanotubes into a vacuum reactor, growing a layer of vanadium oxide film, and annealing, thus forming the vanadium oxide-carbon nanotube composite film, wherein the grown vanadium oxide film is dispersed on the surfaces of the carbon nanotubes and at the gaps among the carbon nanotubes;

(F4) cooling the sample to a room temperature, and then taking the sample out of the reactor; and

(F5) as required, repeating the steps of dispersing the carbon nanotubes, depositing the vanadium oxide and annealing in turn, thus forming the multi-layer vanadium oxide-carbon nanotube composite film.

5. The method, as recited in claim 4, wherein in step (F2), the carbon nanotubes are dispersed by a method selected from the group consisting of spin coating, electrophoresis and printing transplantation, wherein during the spin coating, the dispersion liquid is selected from the group consisting of ethanol, isopropanol, isobutanol, isoamyl alcohol and isohexanol.

6. The method, as recited in claim 4, wherein the carbon nanotubes obtained in step (F2) are provided transversely on the surface of the substrate, have the reticular interconnected structure, are single-walled or multi-walled, have a diameter of 1-50 nm and a length of 50-30000 nm.

7. The method, as recited in claim 4, wherein in step (F2), the functional treatment of the carbon nanotubes is introducing —

COOH, —

COH, —

CNH₂ functional groups by a method selected from the group consisting of a mixture of concentrated H₂SO₄ and HNO₃, concentrated nitric acid, potassium permanganate and Fenton method.

8. The method, as recited in claim 4, in the step (F3), the vanadium oxide can be prepared by a method selected from the group consisting of magnetron sputtering, electron beam evaporation, metal organic compound chemical vapor deposition and atomic layer deposition, wherein while using the magnetron sputtering, a target material can be metal vanadium, or VOx (wherein 1.0≦

x≦

2.5), a reaction gas is a mixture of argon and oxygen, wherein a percentage of oxygen in the mixture is 0.2-20%, a deposition temperature is 20-500°

C.

9. The method, as recited in claim 3, wherein in step (F), the preparation of the vanadium oxide-carbon nanotube composite film comprises:

(F1) cleaning the substrate, and drying the cleaned substrate;

(F2) directly growing a reticular interconnected carbon nanotube film, induced by metal catalyst, on a surface of the cleaned substrate using a chemical vapor deposition system, or an arc discharge system, a laser deposition reactor;

(F3) putting the substrate with the grown carbon nanotubes obtained in step (F2) into a vacuum reactor, growing a layer of vanadium oxide film, and annealing, thus forming a vanadium oxide-carbon nanotube composite film, wherein the grown vanadium oxide is dispersed on the surfaces of the carbon nanotubes and the gaps among the carbon nanotubes;

(F4) cooling the sample to a room temperature, and then taking the sample out of the reactor; and

(F5) as required, repeating the steps of growing the carbon nanotubes, depositing the vanadium oxide and annealing in turn, thus forming a multi-layer vanadium oxide-carbon nanotube composite film.

10. The method, as recited in claim 9, wherein in step (F2), when the chemical vapor deposition system acts as the reactor for growing the one-dimensional carbon nanotubes of the composite film, the reaction gas can be selected from the group consisting of methane, ethylene, acetylene and benzene, the catalyst is simultaneously selected from the group consisting of Fe, Co and Ni for inducing the carbon nanotube to directly grow on the surface of the substrate, a grow temperature of the carbon nanotube is 300°

C.-1100°

C.

11. The method, as recited in claim 9, wherein the carbon nanotubes obtained in step (F2) are provided transversely on the surface of the substrate, have the reticular interconnected structure, are single-walled or multi-walled, have a diameter of 1-50 nm and a length of 50-30000 nm.

12. The method, as recited in claim 9, wherein in the step (F3), the vanadium oxide can be prepared by a method selected from the group consisting of magnetron sputtering, electron beam evaporation, metal organic compound chemical vapor deposition, and atomic layer deposition, wherein while using the magnetron sputtering, a target material can be metal vanadium, or VOx (wherein 1.0≦

x≦

2.5), a reaction gas is a mixture of argon and oxygen, wherein a percentage of oxygen in the mixture is 0.2-20%, a deposition temperature is 20-500°

C.

13. The method, as recited in claim 3, wherein in step (F), the preparation of the vanadium oxide-carbon nanotube composite film comprises:

(F1) cleaning the substrate, and drying the cleaned substrate;

(F2) mixing a certain amount of vanadium oxide powder with an organic solvent, heating, removing insoluble matters by once or repeatedly centrifugal separation, extracting a supernatant fluid, and quietly placing, thus obtaining a vanadium oxide organic sol;

(F3) adding a certain amount of carbon nanotubes into the vanadium oxide organic sol obtained in step (F2), dispersing by ultrasound or stirring, thus forming the new sol mixing the vanadium oxide with the carbon nanotubes;

(F4) coating the new sol mixing the vanadium oxide with the carbon nanotubes obtained in step (F3) on the surface of the cleaned substrate in a spinning manner, and then annealing, thus forming the vanadium oxide-carbon nanotube composite film; and

(F5) as required, repeating the steps of preparing the organic sol, mixing the vanadium oxide with the carbon nanotubes, coating the sol in the spinning manner and annealing in turn, thus forming the multi-layer vanadium oxide-carbon nanotube composite film.

14. The method, as recited in claim 13, wherein in step (F2), the solvent for preparing the vanadium oxide sol is a mixture of an organic solvent A and an organic solvent B, wherein the organic solvent A is benzyl alcohol, the organic solvent B is isopropyl alcohol, or isobutyl alcohol, isoamyl alcohol, isohexanol.

15. The method, as recited in claim 13, wherein in step (F3), the functional treatment of the carbon nanotubes is introducing —

COOH, —

COH, —

CNH₂ functional groups by a method selected from the group consisting of a mixture of concentrated H₂SO₄ and HNO₃, concentrated nitric acid, potassium permanganate and Fenton method.

16. The method, as recited in claim 13, wherein in the step (F3), the added carbon nanotubes are the carbon nanotube solid substances without mixing with any solvents, or the carbon nanotube suspension liquid mixing with the organic solvent in advance.

17. The method, as recited in claim 3, wherein in step (A), the passivation layer has a thickness of 300-1500 nm;

in step (B), the reflecting layer of the micro-bridge has a thickness of 100-1000 nm;

in steps (F) and (H) the layer of photosensitive polyimide film has a thickness of 1-4 μ

m, a thickness of the amorphous silicon nitride film is 10-1500 nm;

in step (G), the layer of metal has a thickness of 10-500 nm.

18. The method, as recited in claim 4, wherein in step (A), the passivation layer has a thickness of 300-1500 nm;

in step (B), the reflecting layer of the micro-bridge has a thickness of 100-1000 nm;

in steps (F) and (H) the layer of photosensitive polyimide film has a thickness of 1-4 μ

m, a thickness of the amorphous silicon nitride film is 10-1500 nm;

in step (G), the layer of metal has a thickness of 10-500 nm.

19. The method, as recited in claim 9, wherein in step (A), the passivation layer has a thickness of 300-1500 nm;

in step (B), the reflecting layer of the micro-bridge has a thickness of 100-1000 nm;

in steps (F) and (H) the layer of photosensitive polyimide film has a thickness of 1-4 μ

m, a thickness of the amorphous silicon nitride film is 10-1500 nm;

in step (G), the layer of metal has a thickness of 10-500 nm.

20. The method, as recited in claim 13, wherein in step (A), the passivation layer has a thickness of 300-1500 nm;

in step (B), the reflecting layer of the micro-bridge has a thickness of 100-1000 nm;

in steps (F) and (H) the layer of photosensitive polyimide film has a thickness of 1-4 μ

m, a thickness of the amorphous silicon nitride film is 10-1500 nm;

in step (G), the layer of metal has a thickness of 10-500 nm.