CN114107924A

CN114107924A - Thermosensitive film for uncooled infrared micro-bolometer

Info

Publication number: CN114107924A
Application number: CN202111333017.5A
Authority: CN
Inventors: 居勇峰; 庄立运; 朱铁柱; 付成芳; 王晓晖; 王马华; 王士湖
Original assignee: Jiangsu Sun Wukong Technology Co ltd; Huaiyin Institute of Technology
Current assignee: Jiangsu Sun Wukong Technology Co ltd; Huaiyin Institute of Technology
Priority date: 2021-11-11
Filing date: 2021-11-11
Publication date: 2022-03-01
Anticipated expiration: 2041-11-11
Also published as: CN114107924B

Abstract

The invention relates to the technical field of uncooled infrared detection, and discloses a thermosensitive film for an uncooled infrared microbolometer, which is characterized by comprising Sn_xZn_1‑xThe material is O, wherein the value range of x is 0.15-0.35; at 25 ℃, the sheet resistance of the thermosensitive film is 1-200K omega/□, and the resistance temperature coefficient is-1.8 to-3.8%/K; doping Sn in ZnO to obtain Sn_xZn_1‑xCompared with the non-doped Sn, the doped thermosensitive film can obtain a higher resistance temperature coefficient under the condition of lower sheet resistance; the heat-sensitive film has good long-term stability of electrical property, simple and easy preparation process, and is suitable for large-scale production.

Description

Thermosensitive film for uncooled infrared micro-bolometer

Technical Field

The invention relates to the technical field of uncooled infrared detection, in particular to a thermosensitive film for an uncooled infrared microbolometer.

Background

The infrared imaging technology is a technology for detecting and identifying a target by performing thermal imaging by using natural radiation infrared rays of a detection object. The infrared imaging technology is characterized in that an infrared detector is a key component of the infrared imaging technology, the infrared detector is divided into a photon detector and a heat detector, and although the photon detector such as a dysprosium cadmium mercury (HgCdTe) detector (working in a wave band of 8-14 mu m) and an indium antimonide (InSb) detector (working in a wave band of 3-5 mu m) has higher performances such as sensitivity, response speed, detection distance and the like, liquid nitrogen is required to be used for cooling (about 80K), and a mechanical scanning device is almost used for infrared imaging, so that the whole infrared imaging system is complex in structure and high in cost, and cannot be popularized and applied on a large scale. Driven by large-scale, very-large-scale integrated circuit technology, infrared detectors have rapidly evolved from unit-type to Focal Plane Array (FPA). The uncooled infrared focal plane array technology becomes the most mainstream direction of the infrared detection technology, compared with the refrigerated infrared detector, the uncooled infrared detector has the main advantages of low cost, small volume, light weight, low power consumption, wide response band and large-scale batch production, and has wide application in military fields such as night vision, accurate guidance and infrared tracking and civil fields such as fire fighting, public security, medical treatment and industrial control.

At present, the main product of the uncooled thermal imaging technology is a microbolometer array, and the microbolometer detects and images the change of the resistance of a sensitive film along with the temperature as the change of a voltage or current signal. The specific process is as follows: the target radiates a certain amount of infrared rays outwards at a certain temperature, the microbolometer absorbs the infrared radiation and generates heat to cause the temperature change of the microbolometer, the thermosensitive film converts the change into resistance change and transmits the resistance change to the reading circuit through an electrical channel in the microbridge, and the change of the resistance value is detected to finish the detection of the target. In this process, the thermosensitive film, one of the key components of the microbolometer, needs to satisfy three of the most important requirements: (1) the resistance is proper, and the circuit can be compatible with a reading circuit; (2) the temperature coefficient of resistance is high, preferably more than 2%/K (absolute value); (3) good process repeatability and long-term stable electrical property.

There are many kinds of thermosensitive materials available for microbolometers, such as metallic titanium, metallic platinum, vanadium oxide, silicon germanium alloy, amorphous silicon, superconducting oxide, giant magnetoresistance material, etc. Among them, vanadium oxide and amorphous silicon are most used because of their appropriate resistance and high temperature coefficient of resistance. However, the two materials still have defects, such as metal-insulator phase transition of vanadium dioxide at about 68 ℃, which can cause thermal hysteresis loop in vanadium oxide compound, thereby affecting the stability and reliability of the device; in addition, the vanadium oxide which meets the heat-sensitive requirement of the microbolometer is relatively complex to prepare due to the fact that the vanadium element has more valence. For amorphous silicon materials, the greater resistance in the application leads to a 1 ^ or greater value of the componentfThe noise is large and thus affects the detection rate of the device.

The invention patent of the applicant's grant publication number of CN 109988997B, named as heat-sensitive film and the preparation method and application thereof discloses a heat-sensitive film used in an uncooled infrared microbolometer, which is made of ZnOx material, wherein the value range of x is 0.7-0.95; at 25 ℃, the sheet resistance of the thermosensitive film is 5-500K omega/□, and the resistance temperature coefficient is-1.5 to-3.5%/K. However, since the film has a large resistance when the TCR is satisfied when it is used in a detector, there is a gap from the ideal state. The device is required to have a proper square resistance, the larger the resistance temperature coefficient is, the better the resistance temperature coefficient is, and if the square resistance is too large, incompatibility with a reading circuit can be caused, and the reliability of the device is influenced. Therefore, in the field of uncooled infrared detection, the exploration and process improvement of the thermosensitive film are still hot spots and difficulties of current research. Researchers are constantly searching for new heat-sensitive materials, and at the same time, new processes are continuously researched to improve the performance of the existing heat-sensitive materials.

Disclosure of Invention

The purpose of the invention is as follows: aiming at the problems in the prior art, the invention provides a thermosensitive film for an uncooled infrared micro-bolometer, which is prepared by doping Sn in ZnO to obtain Sn_xZn_1-xCompared with the non-doped Sn, the doped thermosensitive film can obtain a higher resistance temperature coefficient under the condition of lower sheet resistance; the heat-sensitive film has good long-term stability of electrical property, simple and easy preparation process, and is suitable for large-scale production.

The technical scheme is as follows: the invention provides a thermosensitive film for an uncooled infrared microbolometer, which is prepared from Sn_xZn_1-xThe material is O, wherein the value range of x is 0.15-0.35; at 25 ℃, the sheet resistance of the thermosensitive film is 1-200K omega/□, and the resistance temperature coefficient is-1.8 to-3.8%/K; the preparation method comprises the following steps: s1: putting the dried and cleaned substrate into a direct-current reaction magnetron sputtering furnace, and vacuumizing the background to 1 x 10^-4Heating the substrate to 100-300 ℃ in Pa; s2: blocking the substrate by using a baffle plate, and carrying out pre-sputtering on a metal zinc target and a tin target; s3: moving away the baffle plate, controlling the sputtering power of the zinc target to be 80-120W and the sputtering power of the tin target to be 10-20W, and depositing Sn with the thickness of 50-350 nm on the substrate through reactive sputtering_xZn_1-xAn O film; the flow ratio of oxygen and argon during sputtering is 10-30%; s4: simultaneously shutting off oxygen flow, argon flow and sputteringCurrent flow; s5: when the DC reaction magnetron sputtering furnace is stable, the background vacuum is 1.0 multiplied by 10^-4 ~1.5×10^-4After Pa, for the Sn_xZn_1-xAnnealing the O film; s6: obtaining Sn through annealing treatment_xZn_1-xAnd (4) cooling the O film to room temperature under high vacuum or oxygen atmosphere to obtain the thermosensitive film, and taking out for later use.

Preferably, after S6, a passivation film of an insulating material is further deposited on the heat sensitive film. Because of Sn_xZn_1-xThe O film material has strong activity and is easily oxidized by air, so that the resistance and the stability and the reliability of the resistance temperature coefficient of the material are reduced. To insulate Sn_xZn_1-xThe O film material and air react with each other, and the invention also discloses Sn_xZn_1-xAnd depositing a layer of passivation film on the O film material. Because the passivation film and underlying Sn_xZn_1-xThe O thin film is in parallel with the read circuit, and therefore, the passivation film is required to have high insulation so as not to generate additional resistance.

Preferably, the thickness of the passivation film is 10-50 nm. The passivation film with the thickness within the range can effectively isolate the interaction between air and the heat sensitive layer, and prevent the heat sensitive layer from being oxidized. Preferably, the insulating material is SiC or Si₃N₄、SiO₂TiN or TiO₂. According to the action of the passivation film, the passivation film is prevented from being contacted with Sn_xZn_1-xSince the passivation film is required to have a weak oxidizing ability due to the interaction of O thin film materials, SiC and Si, which are insulating materials having a weak oxidizing ability, are preferably used as the material of the passivation film₃N₄、SiO₂TiN or TiO₂。

Preferably, in the step S2, the pre-sputtering is performed at an argon flow rate of 50 to 100 sccm, a sputtering current of 0.1 to 0.6A, and a pre-sputtering time of 10 to 20 min.

Preferably, in the step S3, the working pressure during sputtering is 1-2.5 Pa, the sputtering temperature is 100-300 ℃, the sputtering current is 0.1-0.6A, and the sputtering time is 10-50 min.

Preferably, in the step S5, the annealing atmosphere during the annealing process is true1.0X 10 in the air^-4~1.5×10^-4Pa or 0.1-1.5 Pa in an oxygen atmosphere, annealing temperature of 200-400 ℃, and heat preservation time of 20-60 min.

Preferably, in the S6, the high vacuum is 1.0 × 10^-4 ~1.5×10^-4Pa, and the oxygen atmosphere is 0.1-1.5 Pa.

Has the advantages that: in the present invention, Sn is used as the heat-sensitive film_xZn_1-xThe resistance of the thermosensitive film is 1-200K omega/□, the resistance is appropriate, the thermosensitive film can be well compatible with a reading circuit, the Temperature Coefficient of Resistance (TCR) is higher, and the voltage response rate of the device can be improved within-1.8-3.8%/K, so that the detection rate of the device is improved. The thermosensitive film has no phase change in the application range of the device, and the size of the resistor is easy to control, so that the defects in the prior art can be overcome, the long-term stability of the electrical property is good, the preparation process is simple and feasible, and the thermosensitive film is suitable for large-scale production.

The most important point is that compared with ZnO film material, the doping of Sn can effectively reduce the sheet resistance of the film without reducing or increasing the temperature coefficient of resistance of the film, and the film has long-term stable electrical property, and the sheet resistance and the temperature coefficient of resistance are comparable to vanadium oxide.

Sn_xZn_1-xThe preparation method of the O film material is the combination of direct current magnetron reactive sputtering and in-situ annealing, and the parameters of sputtering power, sputtering pressure, oxygen-argon ratio, sputtering temperature, sputtering current, sputtering time, annealing atmosphere, annealing pressure, annealing temperature, annealing time and the like in the sputtering process are adjusted to control Sn_xZn_1-xOxygen vacancy concentration in O film material, thereby achieving effective control of Sn_xZn_1-xThe resistance and temperature coefficient of resistance of the O film material.

Drawings

FIG. 1 is a side view of a heat-sensitive film of the present invention;

fig. 2 is a sheet resistance-temperature curve of the thermosensitive film obtained in embodiment 2.

Detailed Description

The present invention will be described in detail with reference to the accompanying drawings.

Embodiment 1:

sequentially placing a K9 glass substrate into acetone, alcohol and deionized water solution for ultrasonic cleaning, drying the substrate by blowing with nitrogen, placing the substrate into a direct-current reaction magnetron sputtering furnace, and vacuumizing the background to 1 x 10^-4Pa. During this time, the substrate was heated to 200 ℃. The substrate was blocked with a shutter, and the metallic zinc target and the tin target were simultaneously subjected to pre-sputtering for 10 min with an argon flow of 100 sccm and a sputtering current of 0.4A. After the pre-sputtering, keeping the argon flow of 100 sccm and the zinc target sputtering current unchanged, reducing the tin target sputtering current to 0.1A, adding oxygen flow of 10sccm and working pressure of 1.5 Pa, removing the baffle, sputtering on the substrate for 20 min, and keeping the substrate holder rotating at a constant speed in the sputtering process. After sputtering is completed, the oxygen flow, the argon flow and the sputtering current are simultaneously closed. When the sputtering furnace is stable, the background vacuum reaches 1 multiplied by 10^-4And after Pa, heating the substrate to 300 ℃, adding oxygen to keep the air pressure of the chamber at 1.5 Pa, annealing the film for 20 min, naturally cooling, and taking out the sample after the temperature is reduced to the normal room temperature. Obtaining Sn with the thickness of about 120 nm, the sheet resistance of 5K omega/□ at 25 ℃ and the temperature coefficient of resistance of-1.8%/K_0.15Zn_0.85And (3) O film. Finally, TO with the thickness of 20nm is deposited on the prepared film₂A passivation layer of material.

FIG. 1 is a side view of a thermosensitive film covered with a passivation film according to the present invention.

As shown in fig. 2, the resistance-temperature curve of the thermosensitive film obtained in the present embodiment (sample R1 in the figure, the curves at the time of temperature increase and temperature decrease overlap). It can be seen that the resistance changes exponentially with temperature, and no thermal hysteresis loop is found in the processes of temperature rise and temperature fall.

Embodiment 2:

sequentially placing a K9 glass substrate into acetone, alcohol and deionized water solution for ultrasonic cleaning, drying the substrate by blowing with nitrogen, placing the substrate into a direct-current reaction magnetron sputtering furnace, and vacuumizing the background to 1 x 10^-4Pa. During this time, the substrate was heated to 200 ℃. Using bafflesThe substrate was pre-sputtered with a zinc metal target and a tin target simultaneously for 10 min using an argon flow of 100 sccm and a sputtering current of 0.4A. After the pre-sputtering, keeping the argon flow of 100 sccm and the zinc target sputtering current unchanged, reducing the tin target sputtering current to 0.15A, adding oxygen flow of 10sccm and working pressure of 1.5 Pa, removing the baffle, sputtering on the substrate for 20 min, and keeping the substrate holder rotating at a constant speed in the sputtering process. After sputtering is completed, the oxygen flow, the argon flow and the sputtering current are simultaneously closed. When the sputtering furnace is stable, the background vacuum reaches 1.5 multiplied by 10^-4And after Pa, heating the substrate to 300 ℃, adding oxygen to keep the air pressure of the chamber at 1.5 Pa, annealing the film for 20 min, naturally cooling, and taking out the sample after the temperature is reduced to the normal room temperature. Obtaining Sn with the thickness of about 115 nm, the sheet resistance of 90K omega/□ at 25 ℃ and the temperature coefficient of resistance of-2.3%/K_0.2Zn_0.8And (3) O film. Finally, TO with the thickness of 20nm is deposited on the prepared film₂A passivation layer of material.

As shown in fig. 2, the sheet resistance-temperature curve of the thermosensitive film obtained in the present embodiment (sample R2 in the figure, the curves at the time of temperature increase and temperature decrease overlap). It can be seen that the resistance changes exponentially with temperature, and no thermal hysteresis loop is found in the processes of temperature rise and temperature fall.

Embodiment 3:

sequentially placing a K9 glass substrate into acetone, alcohol and deionized water solution for ultrasonic cleaning, drying the substrate by blowing with nitrogen, placing the substrate into a direct-current reaction magnetron sputtering furnace, and vacuumizing the background to 1 x 10^-4Pa. During this time, the substrate was heated to 200 ℃. The substrate was blocked with a shutter, and the metallic zinc target and the tin target were simultaneously subjected to pre-sputtering for 10 min with an argon flow of 100 sccm and a sputtering current of 0.4A. After the pre-sputtering, keeping the argon flow of 100 sccm and the zinc target sputtering current unchanged, reducing the tin target sputtering current to 0.2A, adding oxygen flow of 10sccm and working pressure of 1.5 Pa, removing the baffle, sputtering on the substrate for 20 min, and keeping the substrate holder rotating at a constant speed in the sputtering process. After sputtering is completed, the oxygen flow, the argon flow and the sputtering current are simultaneously closed. When the sputtering furnace is stable, the background vacuum reaches 1.5 multiplied by 10^-4After Pa, the substrate was heated to 300 ℃ and oxygen was addedKeeping the air pressure of the chamber at 1.5 Pa, annealing the film for 20 min by oxygen, naturally cooling, and taking out the sample when the temperature is reduced to the normal room temperature. Obtaining Sn with the thickness of about 118 nm, the sheet resistance of 200K omega/□ at 25 ℃ and the temperature coefficient of resistance of-3.8%/K_0.25Zn_0.75And (3) O film. Finally, TO with the thickness of 20nm is deposited on the prepared film₂A passivation layer of material.

The above embodiments are merely illustrative of the technical concepts and features of the present invention, and the purpose of the embodiments is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. A thermosensitive film for non-refrigerating infrared microbolometer is prepared from Sn_xZn_1-xThe material is O, wherein the value range of x is 0.15-0.35; at 25 ℃, the sheet resistance of the thermosensitive film is 1-200K omega/□, and the resistance temperature coefficient is-1.8 to-3.8%/K; the preparation method comprises the following steps:

s1: putting the dried and cleaned substrate into a direct-current reaction magnetron sputtering furnace, and vacuumizing the background to 1 x 10^-4Heating the substrate to 100-300 ℃ in Pa;

s2: blocking the substrate by using a baffle plate, and carrying out pre-sputtering on a metal zinc target and a tin target;

s3: moving away the baffle plate, controlling the sputtering power of the zinc target to be 80-120W and the sputtering power of the tin target to be 10-30W, and depositing Sn with the thickness of 50-350 nm on the substrate through reactive sputtering_xZn_1-xAn O film; the flow ratio of oxygen and argon during sputtering is 10-30%;

s4: simultaneously closing the oxygen flow, the argon flow and the sputtering current;

s5: when the DC reaction magnetron sputtering furnace is stable, the background vacuum is 1.0 multiplied by 10^-4 ~1.5×10^-4After Pa, for the Sn_xZn_1-xAnnealing the O film;

s6: obtaining Sn through annealing treatment_xZn_1-xAnd (4) cooling the O film to room temperature under high vacuum or oxygen atmosphere to obtain the thermosensitive film, and taking out for later use.

2. The thermosensitive film for uncooled infrared microbolometer according to claim 1, wherein a passivation film of an insulating material is further deposited on the thermosensitive film after S6.

3. The thermosensitive thin film for an uncooled infrared microbolometer according to claim 2, wherein the thickness of the passivation film is 10 to 50 nm.

4. The thermosensitive film for uncooled infrared microbolometer according to claim 2, wherein the insulating material is SiC, Si₃N₄、SiO₂TiN or TiO₂And the like.

5. The thermosensitive film for uncooled infrared microbolometer according to any one of claims 1 to 4, wherein in the S2, in the preliminary sputtering, an argon flow rate is 50 to 100 sccm, a sputtering current is 0.1 to 0.6A, and a preliminary sputtering time is 10 to 20 min.

6. The thermosensitive film for uncooled infrared microbolometer according to any one of claims 1 to 4, wherein in S3, the working pressure at the time of sputtering is 1.0 to 2.5 Pa, the sputtering temperature is 100 to 300 ℃, the sputtering current is 0.1 to 0.6A, and the sputtering time is 10 to 50 min.

7. The thermosensitive film for uncooled infrared microbolometer according to any one of claims 1 to 4, wherein in the S5The annealing atmosphere during annealing treatment was 1.0X 10 in vacuum^-4~1.5×10^-4Pa or 0.1-1.5 Pa in an oxygen atmosphere, annealing temperature of 200-400 ℃, and heat preservation time of 20-60 min.

8. The thermosensitive film for uncooled infrared microbolometer according to claim 7, wherein the high vacuum is 1.0 x 10 in the S6^-4 ~1.5×10^-4Pa, and the oxygen atmosphere is 0.1-1.5 Pa.