Infrared thin film device and method of manufacturing the same

Abstract

The application provides an infrared thin film device and a preparation method thereof, and belongs to the technical field of optical thin films, and specifically comprises an inert substrate; a long-wave pass film system deposited on one surface of the inert substrate, the long-wave pass film system being a non-equal-thickness periodic film system, and the structure of the periodic film system being expressed as x(0.8L1(H1L1) 3 H10.8L1) 3 wherein H1 is a high-refractive-index material ZnS, L1 is a low-refractive-index material Yb-B, Yb-B is a mixed thin film material of YbF3 and Ca, and x is a multiple of the film thickness λ / 4; and an anti-reflection film system deposited on the other surface of the inert substrate, the structure of the basic film system being Sub|(H2L2) 2 M2|Air, wherein H2 is a high-refractive-index material Ge, L2 is a medium-refractive-index material ZnS, M2 is a low-refractive-index material Yb-B, Yb-B is a mixed thin film material of YbF3 and Ca, and the long-wave pass film system, the anti-reflection film system and the surface topography of the inert substrate are similar. Through the processing scheme, the influence of stress on the film layer and the device is reduced, and the strength of the film layer is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical film technology, and particularly relates to an infrared film device and a preparation method thereof. BACKGROUND

[0002] The existence of stress not only causes direct damage such as wrinkling, breaking and peeling of the film of the optical device, but also affects the optical performance and imaging quality of the optical system through the interaction between the film layers and between the film layers and the substrate, especially the infrared film. Due to the relatively thick thickness of the infrared film and the poor strength of the film layer, the stress may cause the optical device to be cracked or peeled off.

[0003] However, the existing research on low-stress films mainly focuses on adjusting the process, but still cannot reduce the influence of stress on the film of the device. SUMMARY

[0004] Therefore, in order to overcome the shortcomings of the prior art, the present application provides an infrared film device and a preparation method thereof, which reflects in the micro-light wave band and transmits in the middle infrared wave band when the incident angle is greater than 50°, and has high surface accuracy and low stress film.

[0005] In order to achieve the above-mentioned purpose, the present application provides an infrared film device, comprising: an inert substrate; a long-wave pass film system deposited on one surface of the inert substrate, the long-wave pass film system being a non-equal-thickness periodic film system, the structure of the periodic film system being expressed as x(0.8L1(H1L1) 3 H10.8L1) 3 and a anti-reflection film system deposited on the other surface of the inert substrate, the structure of the base film system being Sub|(H2L2) 2 M2|Air, wherein H2 is a high-refractive-index material Ge, L2 is a medium-refractive-index material ZnS, M2 is a low-refractive-index material Yb-B, Yb-B is a mixed film material of YbF3 and Ca, the surface shape of the long-wave pass film system, the anti-reflection film system and the inert substrate is similar.

[0006] In one embodiment, the film thicknesses of the multiple periodic film systems in the long-wave pass film system form an arithmetic sequence or a geometric sequence.

[0007] In one embodiment, the number of periodic film systems in the long-wave pass film system is 3-8.

[0008] In one embodiment, the basic structure of the long-wave pass film system is Sub|1.4(0.8L1(H1L1) 3H10.8L1) 3 1.1(0.8L1(H1L1) 3 H10.8L1) 3 0.9(0.8L1(H1L1) 3 H10.8L1) 3 0.7(0.8L1(H1L1) 3 H10.8L1) 3 |Air.

[0009] In one embodiment, the inert substrate is any one of a ZnS substrate, a sapphire substrate, a Si substrate, a CaF2 substrate.

[0010] A method for preparing an infrared thin film device, comprising: obtaining design parameters of an infrared thin film device, determining a film structure of a long-wave pass film system according to the design parameters; detecting surface profiles of two surfaces of an inert substrate; calculating stress change values of single layers H1 and L1 in a periodic film system respectively by using Stoney formula, setting the stress values of H1 thin film with corresponding design thickness and the stress values of L1 thin film with corresponding design thickness to be proportional; depositing the film structure of the long-wave pass film system on one surface of the inert substrate according to the stress values of the H1 thin film and the L1 thin film; measuring a surface profile of the long-wave pass film system, and calculating an antireflection stress of an antireflection film according to the surface profile of the inert substrate before depositing the film system; optimizing a base film system according to the antireflection stress to obtain a film structure of the antireflection film; depositing the antireflection film on the other surface of the inert substrate according to the film structure of the antireflection film, and obtaining the infrared thin film device according to any one of the above.

[0011] In one embodiment, the depositing the film structure of the long-wave pass film system on one surface of the inert substrate comprises: adjusting evaporation mode, evaporation rate, ion source assisted deposition energy size, and proportioning of mixed film material Yb-B, so that the stress values of ZnS thin film with corresponding design thickness and the stress values of Yb-B thin film with corresponding design thickness are proportional.

[0012] Compared with the prior art, the present application has the advantages that: by adjusting the stress of the long-wave pass film system in the film layer deposition process, the stress of the film system is reduced, and the stress is compensated by the antireflection film on the other surface of the substrate, so that the influence of the stress on the film layer and the device is reduced without changing the surface profile accuracy of the original device, and the strength of the film layer is improved. BRIEF DESCRIPTION OF DRAWINGS

[0013] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and all other drawings obtained by those of ordinary skill in the art based on the drawings without creative effort should fall within the scope of the present application.

[0014] Figure 1 is a flowchart of a preparation method of an infrared thin film device in an embodiment of the present application;

[0015] Figure 2 is a design curve of a long-wave pass film system of an infrared thin film device in an embodiment of the present application;

[0016] Figure 3 is a design curve of an antireflection film system of an infrared thin film device in an embodiment of the present application;

[0017] Figure 4 is a design curve of a double-sided film of an infrared thin film device in an embodiment of the present application;

[0018] Figure 5 is a measured spectrum curve of an infrared thin film device in an embodiment of the present application;

[0019] Figure 6 is a measured spectrum curve of an infrared thin film device in an embodiment of the present application. DETAILED DESCRIPTION

[0020] The embodiments of the present application will be described in detail below with reference to the drawings.

[0021] The embodiments of the present application will be described in detail below with reference to the drawings.

[0022] It is to be appreciated that various aspects described herein are described in the context of examples that are within the scope of the claims. It is to be understood that the aspects described herein can be implemented in a wide variety of forms and that any particular structure and / or function described herein is merely illustrative. An aspect described herein can be implemented alone or in combination with any other aspect or aspects. Further, any aspect described herein can be implemented with respect to any other structure and / or function, not necessarily the ones described specifically herein. For example, an apparatus can be implemented to practice a method or realize a structure in any number of ways.

[0023] It is also to be understood that the drawings are not necessarily drawn to scale and that the dimensions of the various features can have been exaggerated or minimized for the sake of clarity.

[0024] In addition, in the following description, numerous specific details are provided for a thorough understanding. One skilled in the relevant art will recognize, however, that the aspects described herein can be practiced without one or more of these specific details.

[0025] Embodiments of the present application provide an infrared thin film device, including an inert substrate, a long-wave pass film system, and an anti-reflection film system.

[0026] In one embodiment, the inert substrate is any one of a ZnS substrate, a sapphire substrate, a Si substrate, and a CaF2 substrate. The inert substrate has two surfaces, an upper surface and a lower surface, and the surface profiles of the two surfaces are close to each other. The surface profile for a spherical surface refers to N, which describes the deviation between the theoretical profile and the actual profile. For example, if the radius is required to be 10 mm, and the profile after processing is 9.8 mm, then N is 0.2 mm. ΔN represents the local profile error. The surface profile deviation refers to the deviation of the surface of the optical element from the ideal standard surface, which is indicated by the aperture or the surface flatness. In one embodiment, the deviation of the surface profiles of the two surfaces is no more than 2% of the curvature parameter.

[0027] The long-wave pass film system is deposited on one surface of the inert substrate. The long-wave pass film system is a non-equal-thickness periodic film system, and the structure of the periodic film system is expressed as x(0.8L1(H1L1 3 H10.8L1) 3Wherein, H1 is high refractive index material ZnS, L1 is low refractive index material Yb-B, Yb-B is YbF3 and Ca mixed thin film material, and x is multiple of film thickness of λ / 4. The basic film system structure is optimized, and the reflectivity in the 0.6-0.9 μm wave band is more than 90%, and the transmittance in the 3.7-4.8 μm wave band is more than 80%.

[0028] The long wave pass film system comprises a plurality of period film systems, and in an embodiment, the number of the period film systems can be 3-8.

[0029] In an embodiment, for example, the number of the period film systems is 4, and the basic structure of the long wave pass film system film system can be Sub|1.4(0.8L1(H1L1) 3 H10.8L1) 3 1.1(0.8L1(H1L1) 3 H10.8L1) 3 0.9(0.8L1(H1L1) 3 H10.8L1) 3 0.7(0.8L1(H1L1) 3 H10.8L1) 3 |Air。Sub represents the substrate, and Air represents air.

[0030] In an embodiment, the film thicknesses of the plurality of period film systems in the long wave pass film system form an arithmetic sequence or a geometric sequence. For example, the number of the period film systems is 4, and the basic structure of the long wave pass film system film system can be Sub|1.3(0.8L1(H1L1) 3 H10.8L1) 3 1.1(0.8L1(H1L1) 3 H10.8L1) 3 0.9(0.8L1(H1L1) 3 H10.8L1) 3 0.7(0.8L1(H1L1) 3 H10.8L1) 3 |Air。

[0031] The antireflection film system is deposited on the other surface of the inert substrate, and the structure of the basic film system is Sub|(H2L2) 2 M2|Air is designed, wherein H2 is high refractive index material Ge, L2 is medium refractive index material ZnS, and M2 is low refractive index material Yb-B, and Yb-B is YbF3 and Ca mixed thin film material. The thickness of the antireflection film system can be 3.7-4.8 μm. The film thickness of each film is λ / 4 optical thickness. The basic film system structure is optimized, and the single-side transmittance in this wave band can reach 98%.

[0032] The surface profile of the long-wave pass film system, the antireflection film system, and the surface profile of the inert substrate are similar. When the long-wave pass film system is coated on the upper surface of the inert substrate, the surface profile of the upper surface of the long-wave pass film system is similar to the surface profile of the upper surface of the inert substrate, and the deviation of the surface profiles of the two surfaces is not greater than 2% of the curvature parameter. When the antireflection film system is coated on the lower surface of the inert substrate, the surface profile of the lower surface of the antireflection film system is similar to the surface profile of the lower surface of the inert substrate, and the deviation of the surface profiles of the two surfaces is not greater than 2% of the curvature parameter.

[0033] As shown in Figure 1 The application also provides a preparation method of an infrared thin film device, which comprises the following steps:

[0034] In step 101, the design parameters of the infrared thin film device are obtained, and the film system structure of the long-wave pass film system is determined according to the design parameters. The design parameters can be the requirements of the incident angle, the micro-light waveband reflection, the mid-infrared waveband transmission, and the like. The refractive indexes of the high-refractive-index material and the low-refractive-index material are obtained, for example, the refractive indexes of ZnS or Yb-B are selected, and the film system structure of the long-wave pass film system is determined according to the design parameters. The design parameters and the refractive indexes of the film layers can be input into the film system design software, and the number of film layers is allowed to be increased, and the film layer thickness is taken as an adjustable variable to determine the film system structure of the long-wave pass film system; or the design parameters are input into the film system design software, and the film layer thickness and the refractive indexes of the film layers are taken as adjustable variables to determine the film system structure of the long-wave pass film system. Specifically, the Variable metric optimization function in the TFC film system design software can be used to optimize the basic film system.

[0035] In step 102, the surface profiles of the two surfaces of the inert substrate are detected. For example, the inert substrate is a circular ZnS substrate with a diameter of 30 mm, and the surface profiles are measured by using a reflection interferometer, the first surface Power=0.038λ, and the second surface Power=0.072λ, wherein λ=632.8 nm, and power represents the vertical distance from the center point of the curved surface to the edge plane.

[0036] In step 103, the stress change values of the single layers H1 and L1 in the periodic film system are calculated by using the Stoney formula, and the stress values of the H1 thin film with the corresponding design thickness and the stress values of the L1 thin film with the corresponding design thickness are set to be proportional.

[0037] The Stoney formula is as follows:

[0038]

[0039]

[0040] For example, the designed physical thickness of ZnS is 4000-4500 nm, and the designed physical thickness of Yb-B is 6000-6300 nm. The ZnS and Yb-B are plated in a ratio of 400 nm and 600 nm, respectively. According to the long-wave pass optimization curve shown in FIG. 6, the calculated result of the Yb-B single layer is 805.7 MPa, and the calculated result of the ZnS single layer is 609.8 MPa. The Yb-B is a mixed thin film material of YbF3 and Ca. Generally, YbF3 is in tensile stress, and the YbF3 with moderate Ca doping can be in compressive stress. The stress variation direction can be adjusted by adjusting the mixing ratio. Figure 2

[0041] In step 104, the film structure of the long-wave pass film system is plated on one surface of the inert substrate according to the H1 film stress and the L1 film stress.

[0042] In step 105, the surface profile of the long-wave pass film system is measured, and the antireflection stress of the antireflection film is calculated according to the surface profile of the inert substrate before the film system is plated. After the long-wave pass is plated, PV=0.42λ, which has a large difference compared with the surface profile before the film is plated. Therefore, the antireflection surface needs to be compensated for stress. The stress of the long-wave pass film system is calculated to be -308 MPa. According to the antireflection film optimization curve shown in FIG. 7, the antireflection film system stress is determined to be close to -308 MPa. Figure 3

[0043] In step 106, the base film system is optimized according to the antireflection stress, and the film structure of the antireflection film is obtained. The antireflection stress is substituted into the double-sided film design curve shown in FIG. 8 to optimize the base film system, and the film structure of the antireflection film is obtained. Specifically, the base film system can be optimized by using the Variable metric optimization function in the TFC film system design software. Figure 4

[0044] In step 107, the antireflection film is plated on the other surface of the inert substrate according to the film structure of the antireflection film, and the infrared thin film device is obtained. The double-sided film system is plated on the inert substrate. Before plating, PV=0.182λ, and after plating, PV=0.138λ. The surface profile changes little before and after plating. The spectral curve after plating is shown in FIG. 9, and the spectral curve before plating is shown in FIG. 10. Therefore, the purpose of reducing the film stress is achieved. Figure 5 Figure 6

[0045] The above method and device can effectively reduce the film stress by adjusting the stress of the fixed single layer of the two materials and adjusting the stress by adjusting the mixing ratio of the mixed film material, and plating the film system by a specific process. Moreover, the stress of the long-wave pass film system is adjusted during the film layer deposition process, so as to reduce the stress of the film system. The stress is compensated by the antireflection film arranged on the other surface of the substrate. The influence of the stress on the film layer and the device is reduced without changing the surface profile accuracy of the original device, and the strength of the film layer is improved.​​​​​

[0046] In one embodiment, the YbF3doped with Ca in an appropriate amount can be 1wt% Ca-doped YbF3 8wt% YbF3mixed at a volume ratio of 1:1 5:1. The method for controlling single-layer stress and antireflection film stress compensation, and further controlling the stress of the film system, obtains a filter film layer with small stress variation, maintains the surface shape of the film layer after film formation to be the original surface shape of the substrate itself, effectively solves the problems of large stress between film layers and small adhesion of the film layers, and makes the obtained film layer have good spectral performance and good mechanical stability.

[0047] In one embodiment, the film system structure of the long-wave pass film system plated on one surface of an inert substrate comprises:

[0048] By adjusting the evaporation method, evaporation rate, ion source assisted deposition energy size, and the proportion of the mixed film material Yb-B, the stress of the ZnS thin film with the corresponding designed thickness and the stress of the Yb-B thin film with the corresponding designed thickness are proportional. Among them, the thin film accumulation density of the electron gun evaporation is larger than that of the resistance evaporation, and the thin film stress is large; the higher the evaporation rate, the lower the accumulation density, and the smaller the thin film stress; the higher the ion source energy, the higher the accumulation density, and the higher the thin film stress, so that the stress of the ZnS thin film with the corresponding designed thickness and the stress of the Yb-B thin film with the corresponding designed thickness are proportional by adjusting the evaporation method, evaporation rate, ion source assisted deposition energy size, and the proportion of the mixed film material Yb-B.

[0049] For example, the film plating temperature is 160°C, the background vacuum is between 5.0E-4 and 8.0E-4 Pa, ZnS is deposited by electron beam heating evaporation ion source assisted deposition, the evaporation rate is 1.5-2 nm / s, the Hall source assisted deposition voltage and current are 150-200 V, 0.5-1.5 A, Yb-B is deposited by resistance heating evaporation ion source assisted, the evaporation rate is 0.4-0.6 nm / s, the Hall source assisted deposition voltage and current are 150-200 V, 4-5 A. When Yb-B is divided into three layers: the first layer has a thickness of 100 nm, the second layer has a thickness of 400 nm, and the third layer has a thickness of 100 nm, the ion source assisted energy of the first layer or the third layer is 200 V, 5 A; the ion source assisted energy of the second layer is 200 V, 2 A; the result shows that the total stress of the Yb-B layer is reduced to 603 MPa, and the film system can be deposited by using this process.

[0050] In the same temperature and the same vacuum environment, the single layer film of ZnS and Yb-B is plated, the thickness of the single layer film depends on the thickness of the designed film system, by changing the deposition mode, the ion source energy and the size of the ion source energy in different film layers, the stress of the single layer ZnS and the single layer Yb-B can be controlled to a certain ratio, so that the stress of the plated film system is small, and the effect of reducing the stress is achieved.

[0051] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An infrared thin-film device, characterized in that, include: Inert base; A long-wavelength pass film system is deposited on one surface of the inert substrate. The long-wavelength pass film system is a non-uniform thickness periodic film system, and the structure of the periodic film system is expressed as x(0.8L1 (H1 L1)). 3 H10.8L1) 3 Wherein, H1 is the high-refractive-index material ZnS, L1 is the low-refractive-index material Yb-B, Yb-B is a mixed thin film material of YbF3 and Ca, and x is a multiple of λ / 4 of the film thickness; and An antireflection membrane system is deposited on the other surface of the inert substrate, and the basic membrane system has the structure Sub|(H2L2). 2 The design is based on M2|Air, where H2 is the high refractive index material Ge, L2 is the medium refractive index material ZnS, M2 is the low refractive index material Yb-B, Yb-B is a mixed thin film material of YbF3 and Ca, and Sub represents the substrate and Air represents air. The surface profiles of the long-wavelength membrane system, the antireflective membrane system, and the air-contacting surface profiles are similar to those of the inert substrate.

2. The infrared thin-film device according to claim 1, characterized in that, The film thicknesses of multiple periodic film systems in the long-wavelength film system form an arithmetic or geometric sequence.

3. The infrared thin-film device according to claim 1, characterized in that, The period number of the periodic membrane system in the long-wavelength membrane system is 3 to 8.

4. The infrared thin-film device according to claim 1, characterized in that, The basic structure of the long-wavelength membrane system is Sub|1.4(0.8L1 (H1 L1)). 3 H10.8L1) 3 1.1(0.8L1 (H1 L1) 3 H10.8L1) 3 0.9(0.8L1 (H1 L1) 3 H10.8L1) 3 0.7(0.8L1 (H1 L1) 3 H10.8L1) 3 Air.

5. The infrared thin-film device according to claim 1, characterized in that, The inert substrate is any one of ZnS substrate, sapphire substrate, Si substrate, or CaF2 substrate.

6. A method for fabricating an infrared thin-film device, characterized in that, include: Obtain the design parameters of the infrared thin-film device, and determine the film structure of the long-wavelength pass film system based on the design parameters; Detect the surface profile of two surfaces of an inert substrate; The stress variation values ​​of single layers H1 and L1 in the periodic film system were calculated using the Stoney formula, and the stress values ​​of the H1 film with the corresponding design thickness and the L1 film with the corresponding design thickness were set to be proportional. Based on the values ​​of H1 thin film stress and L1 thin film stress, the long wavepass film system structure is deposited on one surface of the inert substrate. The surface profile of the long-wavelength film system is measured, and the anti-reflection stress of the anti-reflection film is calculated based on the surface profile of the inert substrate before the film system is deposited. The basic membrane system is optimized based on the antireflection stress to obtain the membrane system structure of the antireflection membrane; An antireflection film is deposited on another surface of the inert substrate according to the film system structure of the antireflection film to obtain the infrared thin film device according to any one of claims 1 to 5.

7. The preparation method according to claim 6, characterized in that, The film structure in which the long-wavelength film system is deposited on one surface of the inert substrate includes: By adjusting the evaporation method, evaporation rate, ion source-assisted deposition energy, and the ratio of Yb-B in the mixed film material, the stress of the ZnS film of the corresponding design thickness and the stress of the Yb-B film of the corresponding design thickness are made proportional.

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