Infrared bandpass filter manufacturing method and filter

Abstract

The present invention discloses a method for manufacturing an infrared bandpass filter and a filter. A magnetron sputtering coating technique is used to coat a front surface film and a rear surface film on the front and rear surfaces of a substrate, respectively. The front and rear surface films each comprise a multilayer film, layered using high- and low-refractive-index materials. The coating materials include a substrate, a target material, a sputtering gas, and a reactive gas. The high-refractive-index material comprises a silicon-hydrogen material. The front surface film utilizes a Fabry-Perot interference film system, while the rear surface film utilizes a long-wavelength-pass interference cutoff film system. By combining a high-refractive-index Si-H material and a low-refractive-index SiO2 material and coating them in layers on the substrate, excellent low-angle deviation, bandpass, and cutoff characteristics can be achieved, while also ensuring the overall performance stability and service life of the filter.

Description

Technical Field

[0001] The invention belongs to the technical field of optical filter design and manufacturing, and particularly relates to a manufacturing method of an infrared bandpass filter and the filter. Background Art

[0002] In recent years, facial recognition technology has been fully put into use in mobile phones and other communication devices. The basic requirement of its core optical component, the infrared bandpass filter, is to cut off in the visible band and transmit in the near-infrared band.

[0003] Since the near-infrared light in the 945nm band has strong anti-interference imaging capabilities, the passband position is designed to be within the range of 940-950nm. The ideal transmittance should be maintained above 95%, and the higher the better, so as not to reduce the recognition accuracy of the filter. At the same time, considering the difficulty of preparing the bandpass filter and the sensitivity of iris recognition, it is analyzed that the bandwidth range within 40nm is better.

[0004] Currently, the design and manufacture of 940nm infrared bandpass filters mostly rely on evaporation. Evaporation equipment uses Ta2O5 and SiO2 as a multilayer anti-reflection film with an incident angle of 0° to 30°, achieving a transmittance of up to 80% for p- and s-polarized light in the 600-700nm infrared band. Alternatively, MgF2, HFO2, and TiO2 are used as a multilayer anti-reflection film with an incident angle of 0° to 30°, achieving a transmittance of up to 90% for p- and s-polarized light in the 400-700nm band. This preparation method suffers from numerous film layers, excessive surface stress that can lead to film collapse, thick film thickness (all exceeding 5μm), insufficient passband transmittance, insufficient cutoff band transmittance (only reaching approximately 0.1%), and large offset. This results in unstable filter lifespan, poor filtering effectiveness, and suboptimal overall performance, which can easily lead to recognition failures and cause inconvenience in work and daily life. Summary of the Invention

[0005] In response to the above problems, the present invention designs a method for manufacturing an infrared bandpass filter and a filter, which can use a relatively common process method to realize the manufacture of a low-angle offset near-infrared bandpass filter within 10nm.

[0006] The present invention provides a method for manufacturing an infrared bandpass filter, wherein the filter comprises a substrate, a front surface film, and a rear surface film, and is characterized in that the front surface film and the rear surface film are respectively plated on the front and rear surfaces of the substrate using a magnetron sputtering coating process (technology), wherein the front surface film and the rear surface film both comprise multilayer films, and are layered and plated using high and low refractive index materials; the coating raw materials include a substrate, a target material, a sputtering gas, a reaction gas, etc.; the magnetron sputtering coating technology is implemented using a magnetron sputtering coating device, including a plasma-assisted deposition device (APS, anode), a rotating placement table, a reaction chamber, a target power supply (cathode), and other units; the substrate is also referred to as a substrate; the high refractive index generally refers to a refractive index greater than that of the substrate, and the low refractive index generally refers to a refractive index less than that of the substrate;

[0007] Due to the high refractive index and low absorption properties of silicon-hydrogen (Si-H) materials, as well as the good controllability of thin film preparation using magnetron sputtering technology, using this high-refractive-index material as a spacer layer in a bandpass filter can reduce the optical offset of the filter. Therefore, the present invention considers the use of this material. The high-refractive-index material includes silicon-hydrogen (Si-H) material, which is formed by compensating most of the dangling bonds in hydrogenated amorphous silicon (a-Si:H) material with hydrogen atoms to form Si-H bonds. The low-refractive-index material includes silicon dioxide (SiO2).

[0008] The front surface film uses a Fabry-Perot (FP) interference film system, and the back surface film uses a long-wavelength-pass interference cutoff film system;

[0009] The film layer structure of the Fabry-Perot interference film system includes two reflective layers and one intermediate spacer layer: reflective layer|spacer layer|reflective layer; the front surface film structure includes: Sub|(HL)sH2L2(HL)sH|Air and / or Sub|(HL)sL2H(LH)s|Air,, where H and L are high and low refractive index materials respectively, Sub is the substrate, Air is air, s is the period number, (HL)s represents the superposition of s layers of (HL), and H2 represents the superposition of two layers of high refractive index material;

[0010] The structure of the long-wave-pass interference cutoff film system includes Sub|(0.5HL0.5H)s|Air.

[0011] The above-mentioned structural forms of the front and rear surface films are theoretical structural forms. The actual coating layer is plated based on the theoretical structural form. The actual coating structure can be obtained by performing simulation experiments using coating simulation software.

[0012] To minimize filter offset at a constant light incident angle, the refractive index n of the high-refractive-index material should be as large as possible, while the refractive index n of the low-refractive-index material should be as small as possible. Magnetron sputtering allows for large-area coating due to its high film-forming rate, low substrate temperature, and excellent film adhesion. Magnetron sputtering technology can control parameters such as film thickness, refractive index, and extinction coefficient by controlling the electric field and gas flow rate, facilitating testing and debugging. Therefore, the present invention utilizes magnetron sputtering technology for film coating and filter preparation.

[0013] Furthermore, the substrate includes D263T glass, and the thickness of the substrate is 0.2 to 2 mm.

[0014] Furthermore, the target material includes single crystal silicon, the sputtering gas includes argon, and the reaction gas includes hydrogen and oxygen; when depositing SiO2 film, the reaction gas is oxygen and the sputtering gas is argon; when depositing Si-H film, the reaction gas is hydrogen and the sputtering gas is argon.

[0015] Furthermore, considering the film's stability to the substrate, the film system uses Si-H as the first layer and SiO2 as the outermost layer. Since the stress in Si-H is tensile, using Si-H as the outermost layer would be more prone to film cracking. However, the stress in SiO2 is compressive, which can enhance the film's crack resistance. Therefore, it is preferable to use Si-H as the innermost layer and SiO2 as the outermost layer.

[0016] Furthermore, the optimized film structure of the front surface film includes: Sub|94.62H7.93L 45.03H63.66L 74.35H 51.50L 41.6H 30.09L 79.5H 102.14L136.81H 149.83L 56.15H 109.80L139.74H 156.89L 66.75H 144.88L135.21H 125.51L 76.79H 160.51L 129.50H 114.66L97.01H 194.53L118.27H 24.94L|Air, where the thickness is expressed in nanometers (nm) with an allowable error of ±1 nanometer. Among them, "94.62H" means the high refractive index film layer is 94.62nm thick, "7.93L" means the low refractive index film layer is 7.93nm thick, and the others are similar.

[0017] The above structure is mainly obtained based on optical coating theory and special simulation analysis tools.

[0018] Furthermore, the film structure of the rear surface film includes: Sub|89.25H 21.85L546.28H 179.16L96.30H 48.45L 538.72H 107.82L 25.40H 14.47L65.56H 133.13L 539.05H 40.58L101.72H 168.15L 537.42H 84.26L10.51H 58.00L 138.96H 32.44L|Air, with thickness in nanometers, with an allowable error of ±1 nanometer. The thickness of each film layer is expressed in the same way as the front surface film structure.

[0019] Furthermore, the silicon-hydrogen material film is prepared by magnetron sputtering technology, and hydrogen is filled in the process of sputtering the silicon target. The refractive index and absorptivity of the material are adjusted by adjusting the hydrogen flow rate. The hydrogen flow rate is greater than or equal to 55 sccm (standard milliliters per minute) and less than or equal to 65 sccm.

[0020] Furthermore, the silicon dioxide film is prepared by magnetron sputtering technology, and oxygen is filled in the process of sputtering the silicon target. The refractive index and absorptivity of the material are adjusted by adjusting the oxygen flow rate, and the oxygen flow rate is greater than or equal to 75 sccm and less than or equal to 90 sccm.

[0021] Relatively speaking, SiO2 is a low-refractive-index material, and is relatively balanced in terms of refractive index and extinction coefficient, which can achieve better cutoff characteristics.

[0022] Furthermore, the infrared bandpass filter manufacturing method includes the following steps:

[0023] S1. Install the substrate and target. The target is selected according to the coating requirements of each layer. Infrared bandpass filter coating generally uses single crystal silicon (Si) as the target;

[0024] The installation involves placing the target and the substrate to be plated (substrate) on the concentric axis of the rotating platform of the magnetron sputtering coating equipment, with the target at the bottom and the substrate to be plated at the top. The basic principle of film coating is to pass sputtering gas into a plasma-assisted deposition system (APS) for ionization. The ions bombard the surface of the target and then sputter onto the surface of the substrate to be plated, reacting with the reaction gas to form a thin film layer covering the substrate surface. The film thickness is monitored using a time control method;

[0025] The installation also includes first installing the substrate to be plated with a fixture and placing it in a loading chamber, then using a robotic arm to move the installed substrate from the loading chamber to the reaction chamber, and adjusting the target surface and the base surface to an appropriate distance; the distance depends on factors such as gas pressure, vacuum, APS power, target power supply power, etc., and can be obtained through experiments. The empirical parameter is generally 40 to 50 cm;

[0026] S2. Vacuum the reaction chamber. Turn on the mechanical pump and diffusion pump in turn to evacuate the reaction chamber so that the background vacuum of the reaction chamber is better than 4.0×10 -4 Pa;

[0027] S3, substrate cleaning, including high-velocity inert gas cleaning;

[0028] The high-speed inert gas cleaning includes, before the formal plating, increasing the speed of the rotating placement table to 50-80 rpm / min, turning on the inert gas and controlling its flow rate to be in the range of 100-150 sccm, and turning on the APS and setting the power to 1000-1500W to bombard the surface of the plated substrate for cleaning for 0.5-3 minutes;

[0029] The substrate can also be ultrasonically cleaned before installation, that is, the material is placed in an ultrasonic cleaning machine for cleaning and then dried.

[0030] S4. Layer by layer optical thin films are deposited according to the film structure design of the front surface film and the back surface film. There is no order in which the front and back surface films are deposited. Generally, the first layer of Si-H film is deposited first. The reaction gas is H2 and the sputtering gas is Ar. The target power supply is turned on and its power is set between 4.0 and 6.0 kW. The sputtering gas Ar and the reaction gas H2 are introduced into the APS at the same time. The Ar gas is ionized by the APS, and high-speed argon ions bombard the target to sputter out target particles (generally silicon atoms). The target particles and the reaction gas particles are affected by the electric field and the initial velocity, and a chemical vapor reaction occurs on the surface of the substrate and is deposited to form a Si-H film layer. The reaction gas particles include hydrogen molecules, hydrogen atoms, and hydrogen ions. Any of the sub-items; when SiO2 film is deposited adjacent to Si-H film, the reaction gas is O2 and the sputtering gas is Ar. The target power supply should be turned off first, the H2 gas in the APS should be turned off and the O2 gas should be turned on, the target power supply should be turned on, and the APS power should be set between 1.0 and 3.0 kW. Ar will be ionized to bombard the target, and the sputtered silicon atoms will chemically react with oxygen to form a SiO2 film on the surface of the substrate (covered with other thin film layers); when Si-H film is deposited adjacent to SiO2 film, the target power supply should also be turned off first, the O2 gas in the APS should be turned off and the H2 gas should be turned on, the target power supply should be turned on and its power should be set between 4.0 and 6.0 kW to deposit the Si-H thin film layer; in this way, layer-by-layer plating is carried out according to the film system structure design.

[0031] S5, annealing. Si-H and SiO2 prepared by conventional process have large internal stress. Therefore, after the preparation of the front and rear surface films of the filter is completed, the filter is annealed to prevent the film from collapsing due to excessive internal stress.

[0032] The magnetron sputtering coating equipment is also called a magnetron sputtering machine or a magnetron sputtering coating machine, which can be purchased on the market or self-developed. An example of the magnetron sputtering coating machine purchased on the market is the BRY-450 magnetron sputtering coating machine from Shenyang Boruiyuan Vacuum Technology Co., Ltd.

[0033] Furthermore, the annealing temperature is greater than or equal to 250° C. and less than or equal to 300° C.

[0034] An infrared bandpass filter, characterized in that the filter is manufactured by any of the aforementioned infrared bandpass filter manufacturing methods, and comprises a substrate, a front surface film, and a rear surface film.

[0035] The advantages and beneficial effects of the present invention are as follows: the infrared bandpass filter manufacturing method designed by the present invention utilizes magnetron sputtering technology and silicon-hydrogen materials, and the infrared bandpass filter prepared is thin in thickness, high in bandpass transmittance, low in cutoff band transmittance, small in offset, and is not prone to problems such as film collapse. The filter has a long service life, good filtering effect, and stable overall filter performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is the theoretical spectrum curve of the front surface film;

[0037] Figure 2 is the theoretical spectrum curve of the rear surface film;

[0038] Figure 3 This is a flow chart of a method for manufacturing an infrared bandpass filter;

[0039] Figure 4 It is the surface spectrum test curve of the prepared optical filter. DETAILED DESCRIPTION

[0040] The following embodiments are further described in conjunction with the accompanying drawings and examples. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0041] Example 1. A method for manufacturing an infrared bandpass filter designed by the present invention, wherein the filter comprises a substrate, a front surface film, and a rear surface film. The front surface film and the rear surface film are respectively deposited on the front and rear surfaces of the substrate using magnetron sputtering coating technology. The front surface film and the rear surface film each comprise a multilayer film, deposited in layers using high and low refractive index materials. The coating raw materials include a substrate, a target material, a sputtering gas, a reaction gas, etc. The magnetron sputtering coating technology is implemented using a magnetron sputtering coating device, including a plasma-assisted deposition device (APS, anode), a rotating placement table, a reaction chamber, a target material power supply (cathode), and other units. The substrate is also called a substrate.

[0042] The high-refractive-index material includes silicon-hydrogen (Si-H) and the low-refractive-index material includes silicon dioxide (SiO2). The substrate is 0.5mm-thick D263T glass, the target is single-crystal silicon, the sputtering gas is argon, and the reaction gases are hydrogen and oxygen. When depositing a SiO2 film, the reaction gas is oxygen and the sputtering gas is argon, while when depositing a Si-H film, the reaction gas is hydrogen and the sputtering gas is argon.

[0043] The front surface film uses a Fabry-Perot (FP) interference film system, and the back surface film uses a long-wavelength-pass interference cutoff film system;

[0044] The film layer structure of the Fabry-Perot interference film system includes two reflective layers and one intermediate spacer layer: reflective layer|spacer layer|reflective layer; the front surface film structure includes: Sub|(HL)sH2L2(HL)sH|Air and / or Sub|(HL)sL2H(LH)s|Air,, where H and L are high and low refractive index materials respectively, Sub is the substrate, Air is air, s is the period number, (HL)s represents the superposition of s layers of (HL), and H2 represents the superposition of two layers of high refractive index material;

[0045] The structure of the long-wave-pass interference cutoff film system includes Sub|(0.5HL0.5H)s|Air.

[0046] According to the theoretical structure of the front surface film above, a multi-cavity bandpass structure is used for film system design and analysis. According to the detailed technical index requirements, the initial parameter of the number of cycles is 4. The front surface film is optimized simultaneously using the Sub|(HL)sH2L2(HL)sH|Air and Sub|(HL)sL2H(LH)s|Air structures. The simulation test is carried out by the coating simulation software Macleod to obtain the actual coating structure: Sub|94.62H 7.93L 45.03H 63.66L 74.35H51.50L 41.6H30.09L 79.5H 102.14L 136.81H 149.83L 56.15H109.80L 139.74H 156.89L 66.75H144.88L 135.21H 125.51L 76.79H160.51L 129.50H 114.66L 97.01H 194.53L 118.27H24.94L|Air. Among them, "94.62H" means the high refractive index film thickness is 94.62nm, "7.93L" means the low refractive index film thickness is 7.93nm, and the others are similar. Its theoretical design spectral transmittance is as follows Figure 1The figure shows the design curve without considering back reflection. It can be seen that when the incident angle of light is 0°, the average transmittance in the 920-960nm band is 99.59%, and the average transmittance in the 1000-1100nm band is 0.16%. When the incident angle of light is 38°, the average transmittance in the 915-955nm band is 98.20%, and the average transmittance in the 980-1100nm band is 0.16%. The spectral offset is 11.2nm, and the film thickness is 2.7μm, meeting the design requirements of a spectral offset of less than 20nm and a film thickness of less than 5μm.

[0047] Similarly, the initial parameter of the number of cycles is 4. According to the theoretical structure of the rear surface film, the design is carried out using Macleod software to obtain the actual structure of the rear surface film: Sub|89.25H 21.85L546.28H 179.16L 96.30H 48.45L538.72H 107.82L 25.40H 14.47L65.56H 133.13L 539.05H 40.58L 101.72H 168.15L537.42H 84.26L10.51H 58.00L 138.96H 32.44L|Air, the thickness unit is nanometer, and the allowable error is ±1 nanometer. The thickness of each film layer is expressed in the same way as the front surface film structure. Its theoretical spectrum curve is as follows Figure 2 The following is the spectral curve when back reflection is not considered. It can be seen that the spectra at 0° and 45° incident angles ensure high transmission at (940±20) nm while achieving a cutoff in the 300-650 nm band. Furthermore, the spectrum at 45° incident angle also meets the technical requirements.

[0048] Preferably, during the coating process for both the front and rear surface films, Si-H is used as the first layer and SiO2 is used as the outermost layer. Since the stress in Si-H is tensile, Si-H as the outermost layer is more prone to film cracking; whereas the stress in SiO2 is compressive, which can enhance the film's crack resistance. This embodiment was simulated using film system design software, using Si-H as the innermost layer and SiO2 as the outermost layer. Comparing the coated film with Si-H as the outermost layer, the former showed no film peeling after boiling, while the latter did. Actual preparation results show that when Si-H is used as the innermost layer and SiO2 as the outermost layer, no film peeling was observed, and the SiO2 in the outermost layer also serves to protect the film.

[0049] Preferably, the silicon-hydrogen material film is prepared using magnetron sputtering technology. Hydrogen gas is introduced during the sputtering process of the silicon target. The refractive index and absorptivity of the material are adjusted by adjusting the hydrogen flow rate. The hydrogen flow rate is greater than or equal to 55 sccm (standard milliliters per minute) and less than or equal to 65 sccm. In this embodiment, the hydrogen flow rate is 60 sccm.

[0050] While maintaining the target power, reducing the reaction gas flow rate can increase the material's refractive index. However, as the refractive index increases, the material's absorptivity also changes. This change in absorptivity can significantly affect the transmittance of the film's passband. Therefore, achieving films with both high refractive index and low absorptivity requires further research and experimentation with process parameters. Based on the design principles of thin films, using high-refractive-index materials as spacer layers in bandpass filters can minimize offset, so Si-H materials were selected as the spacer layer. When conducting single-layer film experiments, the primary goal is to improve the refractive index and absorptivity of Si-H materials. However, in magnetron sputtering technology, the material's refractive index is highly sensitive to changes in the ratio of reaction gas flow rate to target material. In this example, a series of gradient experiments on Si-H thin films were designed by varying the hydrogen flow rate (set to 50, 60, 70, and 80 sccm, respectively), while maintaining constant process parameters such as target power and plasma-assisted deposition (APS) power. The experimental results show that with the increase of hydrogen flow rate, the refractive index n and extinction coefficient k of Si-H material decrease. When the hydrogen flow rate is about 60 sccm, the prepared Si-H material has both high refractive index and low absorption rate characteristics. When the hydrogen flow rate is too large, the refractive index of Si-H film decreases significantly, while the extinction coefficient (absorption rate) decreases but the amplitude is very small, still within 10 -5 The hydrogen flow rate is too low. Although the refractive index of the Si-H film is larger, its extinction coefficient is also larger. Therefore, a design with a hydrogen flow rate of 60 sccm is selected.

[0051] Preferably, the silicon dioxide film is prepared using magnetron sputtering technology, and oxygen is added during the sputtering process of the silicon target. The refractive index and absorptivity of the material are adjusted by adjusting the oxygen flow rate. The oxygen flow rate is greater than or equal to 75 sccm and less than or equal to 90 sccm. In this embodiment, the oxygen flow rate is 80 sccm.

[0052] Relatively speaking, SiO2 is a low-refractive-index material, and is relatively balanced in terms of refractive index and extinction coefficient, which can achieve better cutoff characteristics.

[0053] Preferably, Figure 3 As shown, the infrared bandpass filter manufacturing method includes the following steps:

[0054] S1. Install the substrate and target. The target is selected according to the coating requirements of each layer. Infrared bandpass filter coating generally uses single crystal silicon (Si) as the target;

[0055] The installation involves placing the target and the substrate (substrate) to be plated on the concentric axis of the rotating platform of the magnetron sputtering coating equipment, with the target at the bottom and the substrate to be plated at the top. The basic principle of film coating is to pass gas into the plasma-assisted deposition equipment (APS) for ionization. The ions bombard the surface of the target and then sputter onto the surface of the substrate to be plated, reacting with the reaction gas to form a thin film layer covering the surface of the substrate. The film thickness is monitored using a time control method. The preparation work before the preparation of this embodiment includes: a high-purity Si target with a diameter of φ305mm and a thickness of 9.3mm, the substrate material to be plated is D263T, the substrate has a diameter of φ200mm and a thickness of 0.4mm, a set of substrate fixtures, and one bottle each of industrial argon (Ar), oxygen (O2), and hydrogen (H2) gas.

[0056] The installation also includes first installing the plated substrate with a fixture and placing it in the loading chamber, then using a robotic arm to move the installed substrate from the loading chamber to the reaction chamber, and adjusting the target surface and the base surface to an appropriate distance; the distance depends on factors such as gas pressure, vacuum degree, APS power, target power supply power, etc., and can be obtained through experiments. Empirical parameters are generally 40 to 50 cm, and in this embodiment, it is 43 cm.

[0057] S2. Vacuum the reaction chamber. Turn on the mechanical pump and diffusion pump in turn to evacuate the reaction chamber so that the background vacuum of the reaction chamber is better than 4.0×10 -4 Pa, the vacuum degree of this embodiment is better than 10 -4 Pa;

[0058] S3, substrate cleaning, including high-velocity inert gas cleaning;

[0059] In this embodiment, argon is selected as the inert gas, the rotation speed of the rotating table is 60 rpm / min, the control flow rate is 120 sccm, the APS power is set to 1200 W, and the cleaning time is 1 min;

[0060] S4, coating the optical thin film layer by layer, coating the optical thin film layer by layer according to the film system structure design of the front surface film and the back surface film;

[0061] According to the front surface film structure: Sub|1.044540H 0.093396L 0.922645H0.654574L 0.565879H0.501420L 0.747677H 0.176005L 0.920630H0.645771L 2.166552H 0.899623L0.800797H 0.735488L 2.175355H0.858398L 1.141885H 0.867564L 2.141545H0.754413L 0.854296H1.145678L 2.118987H 0.497954L 1.215847H 1.473075L1.713247H0.367144L|Air, first deposit the first layer of Si-H film, with H2 as the reaction gas and Ar as the sputtering gas. Turn on the target power supply and set its power to 5.4KW. Simultaneously introduce Ar and H2 gases into the APS. The system automatically calculates the deposition time based on the input coefficient 1.044540. After completing the Si-H thin film deposition, turn off the target power supply, turn off the H2 gas in the APS and turn on the O2 gas. Turn on the target power supply, set the APS power to 1.85KW, and continue to deposit the second layer of SiO2 film (the coefficient of this layer is 0.093396). Repeat this process until the front surface film deposition is completed.

[0062] According to the rear surface film structure: Sub|2H L 8H LHL 8H LHL 8H LHL 8HL HL|Air, the first layer of Si-H film is deposited first, the reaction gas is H2, the sputtering gas is Ar, the target power is turned on and its power is set to 5.4KW, and Ar and H2 gases are introduced into the APS at the same time. The system automatically calculates the plating time according to the input coefficient 2; after completing the Si-H thin film layer deposition, the target power is turned off, the H2 gas in the APS is turned off and the O2 gas is turned on, the target power is turned on, the APS power is set to 1.85KW, and the second layer of SiO2 film is deposited (the coefficient of this layer is 1), and this is repeated until the rear surface film deposition is completed;

[0063] S5, annealing. After the preparation of the front and rear surface films of the filter is completed, the annealing temperature is set to 280°C and the filter is annealed.

[0064] The magnetron sputtering coating equipment is also called a magnetron sputtering machine or a magnetron sputtering coating machine, which can be purchased on the market or self-developed. An example of the magnetron sputtering coating machine purchased on the market is the BRY-450 magnetron sputtering coating machine from Shenyang Boruiyuan Vacuum Technology Co., Ltd.

[0065] This example uses the company's self-developed magnetron sputtering coating machine. In the experiment, only one circular silicon target is used. The cathode target is at the bottom, and the substrate is loaded on the top of the rotating table. The revolution speed is set to 60 rpm and the rotation speed is 300 rpm. The distance between the target and the substrate is 43 cm, and the background vacuum is less than 1.0×10 -4 The coating machine is equipped with an APS. Before the actual coating process, the rotating platform is accelerated to its proper position, the APS is turned on, and the substrate surface is cleaned. After 60 seconds of cleaning, the coating process begins. Plasma-assisted deposition technology is used throughout the entire coating deposition process to assist in the deposition of thin films, which helps to improve the density of the film.

[0066] The difference between Example 2 and Example 1 is that, in Example 1, the front surface film is plated first and then the rear surface film is plated, while in this example, the rear surface film is plated first and then the front surface film is plated.

[0067] Example 3, an infrared bandpass filter, a filter manufactured according to any of the above-mentioned infrared bandpass filter manufacturing methods, comprising a substrate, a front surface film, and a rear surface film, wherein the front surface film is a Fabry-Perot interference film system of Si-H material, the rear surface film is a long-wave pass interference cutoff film system of SiO2 material, and the substrate is D263T glass with a thickness of 0.5 mm.

[0068] The center wavelength of the filter plated in this embodiment is 940nm, the thickness of the front surface film is 2.7μm, and the thickness of the back surface film is 3.6μm. The refractive index of Si-H in the design is 3.592, and the extinction coefficient is 8.93×10 -5 The refractive index of SiO2 is 1.452, the extinction coefficient is 0, the measured light incident angle is 30 degrees, the offset is 11.2nm, the transmittance is 97.3%, the transmittance is 98.3% at an incident angle of 0 degrees, and the average extinction coefficient is better than 0.006%. The surface spectrum test curve of the filter is as follows Figure 4 shown.

[0069] The basic principle of the present invention is to use magnetron sputtering coating technology to combine high-refractive-index Si-H material and low-refractive-index SiO2 material for layered coating in the film system design. By optimally controlling the hydrogen flow rate during magnetron sputtering coating, the high refractive index and low extinction coefficient of the Si-H film are optimized, and the filter can obtain good low-angle deviation, bandpass and cutoff characteristics. In addition, because the stress of Si-H is tensile stress, it is not easy to peel off the film as the innermost layer; while the stress of SiO2 is compressive stress, it can enhance the crack resistance of the entire film as the outermost layer, thereby ensuring the overall performance stability and service life of the filter.

[0070] The above is only a preferred embodiment of the infrared bandpass filter manufacturing method and filter of the present invention. Although only a typical example is given for the specific design and manufacturing parameters such as gas flow rate, power supply power, annealing temperature, etc., any setting within the preferred range can produce an infrared bandpass filter with better performance. However, the actual performance measurement results may be slightly different from the embodiment of this case. These differences do not exceed the scope of the method described in the present invention and should also be regarded as the scope of protection of the present invention. They will not be listed one by one here.

Claims

1. A method for manufacturing an infrared bandpass filter, wherein the filter comprises a substrate, a front surface film, and a rear surface film, characterized in that: A magnetron sputtering coating process is used to coat the front surface film and the back surface film on the front and back surfaces of the substrate respectively. The front surface film and the back surface film both include multilayer films, which are layered with high and low refractive index materials. The coating raw materials include substrate, target material, sputtering gas, and reaction gas. The high refractive index material includes a silicon-hydrogen material, and the silicon-hydrogen material film is prepared using magnetron sputtering technology. Hydrogen is added during the sputtering process of the silicon target, and the refractive index and absorptivity of the material are adjusted by adjusting the hydrogen flow rate. The hydrogen flow rate is greater than or equal to 55 sccm and less than or equal to 65 sccm. The low refractive index material includes silicon dioxide. The silicon dioxide film is prepared using magnetron sputtering technology. Oxygen is added during the sputtering process of the silicon target, and the refractive index and absorptivity of the material are adjusted by adjusting the oxygen flow rate. The oxygen flow rate is greater than or equal to 75 sccm and less than or equal to 90 sccm. The front surface film uses a Fabry-Perot interference film system, and the rear surface film uses a long-wavelength-pass interference cutoff film system; The front surface film structure includes: Sub|1.044540H 0.093396L 0.922645H 0.654574L0.565879H 0.501420L 0.747677H 0.176005L 0.920630H 0.645771L 2.166552H0.899623L 0.800797H 0.735488L 2.175355H 0.858398L 1.141885H 0.867564L2.141545H 0.754413L 0.854296H 1.145678L 2.118987H 0.497954L 1.215847H1.473075L 1.713247H 0.367144L |Air, the rear surface film structure includes: Sub|2H L 8H LH L8H LHL 8H LHL 8H LHL |Air, where H and L are high and low refractive index materials, respectively, Sub is the substrate, Air is air, s is the period number, (HL)s represents a total of s layers (HL) stacked, and H2 represents two layers of high refractive index material stacked.

2. The method for manufacturing an infrared bandpass filter according to claim 1, wherein: The substrate comprises D263T glass, and the thickness of the substrate is 0.2 to 2 mm; the target material comprises single crystal silicon, the sputtering gas comprises argon, and the reaction gas comprises hydrogen and oxygen.

3. The method for manufacturing an infrared bandpass filter according to claim 1, wherein: The film system has Si-H as the first layer and SiO2 as the outermost layer.

4. The method for manufacturing an infrared bandpass filter according to claim 1, wherein: The optimized film system structure of the front surface film includes: Sub| 94.62H 7.93L 45.03H 63.66L 74.35H 51.50L 41.6H 30.09L79.5H 102.14L 136.81H 149.83L 56.15H 109.80L 139.74H 156.89L 66.75H 144.88L135.21H 125.51L 76.79H 160.51L 129.50H 114.66L 97.01H 194.53L 118.27H 24.94L|Air, the thickness unit is nanometer, and the allowable error is ±1 nanometer.

5. The method for manufacturing an infrared bandpass filter according to claim 1, wherein: The film system structure of the rear surface film includes: Sub| 89.25H 21.85L 546.28H 179.16L 96.30H 48.45L 538.72H 107.82L25.40H 14.47L 65.56H 133.13L 539.05H 40.58L 101.72H 168.15L 537.42H 84.26L10.51H 58.00L 138.96H 32.44L |Air, the thickness unit is nanometer, and the allowable error is ±1 nanometer.

6. The method for manufacturing an infrared bandpass filter according to claim 1, wherein: The following steps are involved: S1. Installation of substrate and target; S2, vacuuming the reaction chamber; S3, substrate cleaning, including high-velocity inert gas cleaning; S4. Layer-by-layer optical thin film coating. According to the film structure design of the front surface film and the back surface film, the optical thin film is coated layer by layer. There is no order in which the front and back surface films are coated. S5, annealing. After the preparation of the front and rear surface films of the filter is completed, the filter is annealed.

7. The method for manufacturing an infrared bandpass filter according to claim 6, wherein: The annealing temperature is greater than or equal to 250° C. and less than or equal to 300° C.

8. An infrared bandpass filter, characterized in that: The optical filter is manufactured according to the infrared bandpass filter manufacturing method according to any one of claims 1 to 7, and includes a substrate, a front surface film, and a rear surface film.

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