Very-long-wave infrared detector and back antireflection film preparation method thereof

Abstract

The invention provides a very long wave infrared detector and a back anti-reflection film preparation method thereof, and the preparation method comprises the steps: placing a tellurium-cadmium-mercury detector to be plated and an accompanying sheet on a clamp based on coating equipment; zinc sulfide and ytterbium fluoride are used as thin film materials, process setting is carried out through coating equipment, and the back anti-reflection thin film of a multi-layer alternating structure is prepared through the set process; performing optical testing on the accompanying film to evaluate the quality of the film; and testing the performance of the mercury cadmium telluride detector. The very-long-wave tellurium-cadmium-mercury detector back anti-reflection film prepared from zinc sulfide and ytterbium fluoride materials not only can significantly improve the optical performance of the detector, but also can ensure the reliability and stability of the detector under various environmental conditions, so that the detector has higher practical value in the fields of remote sensing detection, space flight and aviation, environmental monitoring and the like.

Description

Technical Field

[0001] The invention relates to the technical field of infrared detectors, and in particular to a very long wave infrared detector and a method for preparing a backside anti-reflection film thereof. Background Art

[0002] Infrared detectors are essential components in modern remote sensing, aerospace and military applications. With the advancement of science and technology, especially in the field of spectral detection and space exploration, there is a growing demand for very long wave infrared (VLWIR) radiation with a wavelength greater than or equal to 12 microns. VLWIR detectors have attracted much attention due to their important role in meteorological monitoring, earth observation, environmental science research and other space infrared systems.

[0003] Among the many infrared detector materials, mercury cadmium telluride (HgCdTe, MCT) is an ideal choice for making infrared detectors due to its unique properties. By adjusting the component ratio of cadmium (Cd) in the material, full coverage of the infrared band from short wave to very long wave can be achieved. This makes mercury cadmium telluride detectors show excellent performance in many application fields.

[0004] However, in practical applications, the traditional n-on-p structured HgCdTe detectors have problems such as reduced electron lifetime and increased dark current caused by mercury vacancies, which limits the overall performance of the device. In order to overcome these limitations, in recent years, p-on-n structured HgCdTe detectors have gradually become a research hotspot due to their lower dark current, stable material lattice structure and less temperature dependence.

[0005] In the p-on-n structure HgCdTe detector, a key technical problem is how to effectively reduce the reflection loss of infrared radiation on the back of the detector, thereby improving the sensitivity of the detector. Backside Anti-Reflection Coating (AR coating) technology is one of the key technical means to address this problem. Appropriate backside anti-reflection coating design can not only reduce reflection, but also increase the effective amount of light entering the detector, thereby improving the absorption efficiency and responsiveness of the detector.

[0006] However, in the relevant technology for preparing anti-reflection films on the back side of very long wave infrared detectors, the currently available film materials are not sufficient to cover the optical properties required in the very long wave infrared band. Under certain preparation conditions, film delamination may occur due to poor adhesion between the film and the substrate. The film surface is prone to defects, such as particles, bubbles or unevenness, resulting in poor anti-reflection effect. Summary of the invention

[0007] The invention provides a very long wave infrared detector and a method for preparing a back anti-reflection film thereof, which solves the problem of how to improve the anti-reflection effect of the back anti-reflection film of the very long wave infrared detector.

[0008] In order to achieve the above objectives, this application adopts the following technical solutions:

[0009] In a first aspect, a method for preparing a back-side antireflection film for a very long wave infrared detector is provided, comprising:

[0010] Based on the coating equipment, the HgCdTe detector and accompanying film to be plated are placed on the fixture;

[0011] Using zinc sulfide and ytterbium fluoride as thin film materials, using the coating equipment to set the process, and preparing a multi-layer alternating structure of the back anti-reflection film by setting the process;

[0012] The companion film is subjected to an optical test to evaluate the quality of the film; and the HgCdTe detector is subjected to a performance test.

[0013] In a first possible implementation manner of the first aspect, the thin film material is zinc sulfide having a transparent band of 1 micrometer to 20 micrometers and a refractive index of 2.26, and ytterbium fluoride having a transparent band of 0.6 micrometer to 16 micrometers.

[0014] Based on the first possible implementation of the first aspect, in a second possible implementation of the first aspect, the total thickness of the back anti-reflection film is

[0015] Based on the second possible implementation manner of the first aspect, in a third possible implementation manner of the first aspect, a film system structure of the back anti-reflection film is 1.468H0.523L0.739H1.309L.

[0016] In a fourth possible implementation manner of the first aspect, the process includes an evaporation method and a sputtering method.

[0017] Based on the fourth possible implementation manner of the first aspect, in a fifth possible implementation manner of the first aspect, the evaporation method includes thermal evaporation and / or electron beam evaporation.

[0018] Based on the fifth possible implementation manner of the first aspect, in a sixth possible implementation manner of the first aspect, zinc sulfide and ytterbium fluoride are evaporated by a thermal evaporation process to prepare the back anti-reflection film.

[0019] Based on the fifth possible implementation manner of the first aspect, in a seventh possible implementation manner of the first aspect, zinc sulfide and ytterbium fluoride are evaporated by an electron beam evaporation process to prepare the back anti-reflection film.

[0020] Based on the fifth possible implementation manner of the first aspect, in an eighth possible implementation manner of the first aspect, zinc sulfide is evaporated by an electron beam evaporation process, and ytterbium fluoride is evaporated by a thermal evaporation process to prepare the back anti-reflection film.

[0021] In a second aspect, a very long wave infrared detector is provided. 10. The anti-reflection film on the back side of the detector is prepared by the preparation method described in the first aspect.

[0022] The anti-reflection film on the back of the very long-wave HgCdTe detector made of zinc sulfide and ytterbium fluoride materials used in this application can not only significantly improve the optical performance of the detector, but also ensure its reliability and stability under various environmental conditions, making the detector more practical in the fields of remote sensing, aerospace, environmental monitoring, etc. Specifically:

[0023] The present application adopts a multi-layer thin film structure, and the transparent bands of the two materials are complementary, which can significantly improve the transmittance of incident light in a wider band range (very long wave infrared region above 12μm) and reduce reflection losses; by optimizing the stacked structure of materials with different refractive indices, efficient anti-reflection of light within a specific wavelength range can be achieved, and anti-reflection effects in a wider band range can be achieved, thereby improving the sensitivity and responsiveness of the detector.

[0024] The film prepared in the present application has a smooth surface, high uniformity, and good consistency. It is less likely to have defects than traditional methods under the same preparation conditions. The highly uniform film can ensure consistent optical performance on the entire detector surface and avoid the impact of local performance differences. Therefore, it helps to reduce scattering losses and improve the overall performance of the detector.

[0025] By optimizing the preparation process, the present application can ensure good adhesion between the film and the substrate, prevent the problem of film falling off during use, enhance the reliability of the detector, and reduce the risk of failure due to film defects. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic flow chart of a method for preparing an anti-reflection film on the back side of a very long wave infrared detector provided in an embodiment of the present application. DETAILED DESCRIPTION

[0027] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined purpose, the technical solutions in the embodiments of the present application are clearly described. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present application.

[0028] The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the terms used in this way are interchangeable where appropriate, so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second", etc. are generally of one type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0029] The description of the method flow in the specification of the present application and the steps of the flowchart in the drawings of the present specification do not have to be strictly executed according to the step numbers, and the method steps can be executed in a different order. Moreover, some steps can be omitted, multiple steps can be combined into one step, and / or one step can be decomposed into multiple steps.

[0030] The very long wave infrared detector and the method for preparing the back anti-reflection film thereof provided in the embodiment of the present application are described in detail below in combination with the accompanying drawings and preferred embodiments.

[0031] First, the application scenarios of the very long wave infrared detector and the method for preparing the back anti-reflection film thereof in the embodiment of the present application are described in detail.

[0032] The working mechanism of infrared detectors is based on the photoelectric effect produced after the device absorbs infrared radiation. Infrared radiation can be divided into short wave, medium wave, long wave and very long wave according to the wavelength. Infrared detectors can be classified accordingly for different bands. Very long wave generally refers to the band with a wavelength greater than 14μm. This band is rich in a lot of information, including the humidity and CO2 content in the atmosphere, as well as the structure and temperature profile of the cloud layer, which are necessary for atmospheric remote sensing. At the same time, the peak wavelength is in the very long wave infrared band, which can realize the detection of weak cold targets under the low temperature background of aerospace, and can be used in space infrared systems such as meteorological monitoring. The very long wave infrared focal plane is one of the important directions for the development of the third generation of infrared detection technology, and is currently a hot topic of research in countries around the world.

[0033] Mercury cadmium telluride infrared detectors are widely used in aerospace and civil fields due to their high quantum efficiency and adjustable wavelength. In recent years, there has been a strong demand for very long-wave mercury cadmium telluride detectors with a wavelength ≥ 12μm in research directions such as spectral detection and space detection. Mercury cadmium telluride (Hg1-xCdxTe, x is the Cd component of the material, abbreviated as MCT) is by far the most important semiconductor material for making infrared detectors. By adjusting the material component x, MCT can be used in the very long-wave infrared band.

[0034] Different wavelengths of infrared radiation correspond to different semiconductor bandgap widths. The longer the wavelength, the narrower the bandgap. By adjusting the composition of HgCdTe materials, the bandgap width of HgCdTe materials can be continuously changed from negative bandgap HgTe to 1.65eV CdTe. In theory, HgCdTe infrared detectors can achieve radiation detection covering the entire infrared band. Based on the application needs of remote sensing, aerospace, industry and other fields, as well as the special properties of HgCdTe materials, the development and application of very long-wave HgCdTe infrared focal plane devices are becoming more and more extensive, and more and more research is being conducted on very long-wave infrared detectors. The presence of mercury vacancies in the traditional n-on-p structure reduces the electron lifetime, increases the dark current of the device, and the device uniformity and effective pixel rate also need to be improved. The p-on-n structure is realized by external injection or doping, mainly based on interband recombination, and uses an n-type absorption region with a low doping concentration, which increases the lifetime and diffusion length of minority carriers (holes), which is beneficial to suppress the diffusion current introduced by Auger recombination. Therefore, the dark current of p-on-n structure devices is low. Compared with the n-on-p structure, the dark current of p-on-n structure devices can be reduced by about 2 orders of magnitude. In addition, the mobility of majority carriers (electrons) in the absorption layer (n region) of the p-on-n structure is high, which is beneficial to reducing the serial resistance; the p-on-n structure uses external doping, the material lattice structure is stable, and is less affected by temperature. That is, the long minority carrier lifetime of the p-on-n structure is conducive to achieving low dark current, improving R0A, reducing serial resistance, and further improving the performance of the detector.

[0035] In the p-on-n structure HgCdTe detector, a key technical challenge is how to effectively reduce the reflection loss of infrared radiation on the back of the detector, thereby improving the sensitivity of the detector. Backside Anti-Reflection Coating (AR coating) technology is one of the key technologies developed to address this challenge. Appropriate backside anti-reflection coating design can not only reduce reflection, but also increase the effective amount of light entering the detector, thereby improving the absorption efficiency and responsiveness of the detector.

[0036] The present application aims to provide a very long wave infrared detector and a method for preparing an anti-reflection film on the back thereof, which reduces the reflection of infrared light of a specific band on the back of the detector by optimizing the selection of film materials and the configuration of the number of layers, thereby significantly improving the performance of the detector and meeting the high-precision detection needs in modern remote sensing, aerospace, industrial detection and other fields.

[0037] In order to ensure the stability of the detector performance, the present application uses zinc sulfide and ytterbium fluoride with high mechanical adhesion, hardness, stress, and chemical stability as the film material of the multi-layer composite film layer of the very long wave mercury cadmium telluride detector back anti-reflection film. Compared with a single film of a traditional single film material, the very long wave mercury cadmium telluride detector back anti-reflection film of this multi-layer composite film material has improved detector performance, and the film has higher firmness under the same preparation conditions, which can avoid the occurrence of film peeling.

[0038] See also Figure 1 The present application embodiment provides a method for preparing a back-side antireflection film of a very long wave infrared detector, such as Figure 1 As shown, the preparation method of the embodiment of the present application includes:

[0039] Step S1, placing the HgCdTe detector and its companion film to be plated on a fixture based on a coating device.

[0040] The coating equipment has a vacuum system with high vacuum. The companion film is a blank sample used to test the quality of the film. The fixture is a special fixture that is used to ensure that the designated area (back side) of the detector faces downward, and the polished surface of the companion film is also placed downward on the same fixture.

[0041] Step S2, using zinc sulfide and ytterbium fluoride as thin film materials, using coating equipment to set the process, and preparing a back anti-reflection film with a multi-layer alternating structure through the set process.

[0042] Step S3, performing optical testing on the companion film to evaluate the quality of the film; and performing performance testing on the mercury cadmium telluride detector.

[0043] Furthermore, the thin film materials are zinc sulfide with a transparent band of 1 micron to 20 microns and a refractive index of 2.26 and ytterbium fluoride with a transparent band of 0.6 microns to 16 microns.

[0044] Furthermore, the total thickness of the back antireflection film is

[0045] Furthermore, the film structure of the back anti-reflection film is 1.468H0.523L0.739H1.309L.

[0046] Furthermore, the process includes an evaporation method and a sputtering method.

[0047] Further, the evaporation method includes thermal evaporation and / or electron beam evaporation.

[0048] Specifically, in some possible implementations, zinc sulfide and ytterbium fluoride can be evaporated by thermal evaporation process to prepare the back anti-reflection film; in some possible implementations, zinc sulfide and ytterbium fluoride can be evaporated by electron beam evaporation process to prepare the back anti-reflection film; in some possible implementations, zinc sulfide can be evaporated by electron beam evaporation process, and ytterbium fluoride can be evaporated by thermal evaporation process to prepare the back anti-reflection film.

[0049] For example, in a specific implementation process:

[0050] The HgCdTe detector and companion film to be plated are placed with the polished surface facing downward on a special fixture and installed on a workpiece rotating system of a vacuum chamber of a high vacuum system coating equipment.

[0051] Close the chamber door, press the vacuum button to start the vacuum process in the chamber, set the workpiece speed, workpiece plate heating temperature, heating time, and the rate and thickness of the material to be plated.

[0052] When the vacuum degree, temperature and heating time reach the set values, click the start button to perform thermal evaporation, electron beam evaporation or sputtering process to prepare the back anti-reflection film on the chip.

[0053] After the plating is completed, when the chamber cools down to room temperature, the companion film and the detector are taken out, and the companion film is optically tested and the detector is performance tested.

[0054] The present application adopts a multi-layer thin film structure, and the transparent bands of the two materials are complementary, which can significantly improve the transmittance of incident light in a wider band range (very long wave infrared region above 12μm) and reduce reflection losses; by optimizing the stacked structure of materials with different refractive indices, efficient anti-reflection of light within a specific wavelength range can be achieved, and anti-reflection effects in a wider band range can be achieved, thereby improving the sensitivity and responsiveness of the detector.

[0055] The film prepared in the present application has a smooth surface, high uniformity, and good consistency. It is less likely to have defects than traditional methods under the same preparation conditions. The highly uniform film can ensure consistent optical performance on the entire detector surface and avoid the impact of local performance differences. Therefore, it helps to reduce scattering losses and improve the overall performance of the detector.

[0056] By optimizing the preparation process, the present application can ensure good adhesion between the film and the substrate, prevent the problem of film falling off during use, enhance the reliability of the detector, and reduce the risk of failure due to film defects.

[0057] In summary, the back-side anti-reflection film of the very long-wave mercury cadmium telluride detector made of zinc sulfide and ytterbium fluoride materials used in this application can not only significantly improve the optical performance of the detector, but also ensure its reliability and stability under various environmental conditions, making the detector have higher practical value in the fields of remote sensing, aerospace, environmental monitoring, etc.

[0058] The embodiment of the present application also provides a very long wave infrared detector. The back anti-reflection film of the detector of the embodiment of the present application is prepared by the preparation method as described above.

[0059] The above-mentioned back anti-reflection film of the very long wave infrared detector implements the steps and various processes of the above-mentioned embodiment of the method for preparing the back anti-reflection film of the very long wave infrared detector, and can achieve the same technical effect. To avoid repetition, they are not repeated here.

[0060] Compared with traditional detectors, the detector in the embodiment of the present application reduces back reflection, allowing more infrared radiation to reach the absorption layer of the detector, thereby improving the detector's absorption efficiency of infrared radiation and enhancing the detector's sensitivity; the signal-to-noise ratio (SNR) is improved, allowing the detector to detect weak signals more accurately; it can operate in a wider wavelength range, has higher reliability, and broadens the application scenarios of the detector.

[0061] It should be noted that, in this article, the terms "comprise", "include" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise one..." do not exclude the presence of other identical elements in the process, method, article or device including the element. In addition, it should be pointed out that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in reverse order according to the functions involved, for example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0062] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present application, ordinary technicians in this field can also make many forms without departing from the purpose of the present application and the scope of protection of the claims, all of which are within the protection of the present application.

Claims

1. A method for preparing a back-side antireflection film for a very long wave infrared detector, characterized in that: include: Based on the coating equipment, the HgCdTe detector and accompanying film to be plated are placed on the fixture; Using zinc sulfide and ytterbium fluoride as thin film materials, using the coating equipment to set the process, and preparing a multi-layer alternating structure of the back anti-reflection film by setting the process; The companion film is subjected to an optical test to evaluate the quality of the film; and the HgCdTe detector is subjected to a performance test.

2. The method for preparing a back antireflection film for a very long wave infrared detector according to claim 1, characterized in that: The thin film materials are zinc sulfide with a transparent band of 1 micron to 20 microns and a refractive index of 2.26 and ytterbium fluoride with a transparent band of 0.6 microns to 16 microns.

3. The method for preparing a back antireflection film for a very long wave infrared detector according to claim 2, characterized in that: The total thickness of the back antireflection film is 4. The method for preparing a back antireflection film for a very long wave infrared detector according to claim 3, characterized in that: The film structure of the back anti-reflection film is 1.468H0.523L0.739H1.309L.

5. The method for preparing a back antireflection film for a very long wave infrared detector according to claim 1, characterized in that: The process includes evaporation and sputtering.

6. The method for preparing a back antireflection film for a very long wave infrared detector according to claim 5, characterized in that: The evaporation method includes thermal evaporation and / or electron beam evaporation.

7. The method for preparing a back antireflection film for a very long wave infrared detector according to claim 6, characterized in that: The back antireflection film is prepared by evaporating zinc sulfide and ytterbium fluoride using a thermal evaporation process.

8. The method for preparing a back antireflection film for a very long wave infrared detector according to claim 6, characterized in that: The electron beam evaporation process is used to evaporate zinc sulfide and ytterbium fluoride to prepare the back anti-reflection film.

9. The method for preparing a back antireflection film for a very long wave infrared detector according to claim 6, characterized in that: The electron beam evaporation process is used to evaporate zinc sulfide, and the thermal evaporation process is used to evaporate ytterbium fluoride to prepare the back anti-reflection film.

10. Very long wave infrared detector, characterized in that: The back antireflection film of the detector is prepared by the preparation method according to any one of claims 1 to 9.

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