Method for preparing thin film by utilizing ion beam sputtering and ion beam sputtering coating device

Abstract

The invention provides a method for preparing a thin film through ion beam sputtering and an ion beam sputtering coating device, and belongs to the technical field of ion beam sputtering. The method comprises the following steps: performing first coating treatment on the surface of a substrate in an ion beam sputtering manner, and alternately depositing a first film layer and a second film layer on the surface of the substrate to obtain a first laminated film; performing first in-situ annealing on the first laminated film to obtain a first laminated film after in-situ annealing; performing second coating treatment on the surface of the first laminated film subjected to in-situ annealing in an ion beam sputtering manner, and alternately depositing a third film layer and a fourth film layer on the surface of the first laminated film to obtain a second laminated film; and performing second in-situ annealing on the second laminated film to obtain the thin film. According to the method disclosed by the invention, the thermal noise in the laminated film can be reduced in the preparation process of the multi-laminated film. And meanwhile, through two times of in-situ annealing, the pollution to the thin film in the sampling, transferring and loading processes from the first lamination layer to the second lamination layer is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of ion beam sputtering, and in particular to a method for preparing a thin film by utilizing ion beam sputtering and an ion beam sputtering coating device. Background Art

[0002] Dielectric optical films (especially oxides and nitrides) are widely used in a wide range of applications. Physical vapor deposition is the main method for producing dielectric optical films, which usually includes electron beam evaporation, magnetron sputtering, ion beam sputtering, ion-assisted deposition and other methods. If the order is based on the energy of thin film atomic deposition during the coating process, it is usually ion beam sputtering>magnetron sputtering, which is similar to ion-assisted deposition>electron beam evaporation, and the density and surface roughness of the corresponding films are roughly the same. When the film density is poor, the refractive index of the film layer is easily changed due to the absorption of water vapor, and the larger surface roughness will also bring significant scattering loss. Therefore, most of the ultra-high reflectivity dielectric films are currently prepared by ion beam sputtering.

[0003] In adapting to different application scenarios, the requirements for the performance parameters of ultra-high reflectivity dielectric films prepared by ion beam sputtering are also different. For example, in the field of gravitational wave detection, the conversion of light absorbed by the film into heat may cause thermal distortion of the mirror, affecting the beam quality, thus leading to more stringent requirements for film absorption loss. Summary of the invention

[0004] In view of this, in order to at least partially solve at least one of the above-mentioned technical problems, the present invention provides a method for preparing a thin film by using ion beam sputtering and an ion beam sputtering coating device.

[0005] According to an embodiment of one aspect of the present invention, a method for preparing a thin film by using ion beam sputtering is provided, comprising: performing a first coating treatment on a substrate surface by means of ion beam sputtering, alternately depositing a first film layer and a second film layer on the substrate surface to obtain a first stacked film; performing a first in-situ annealing on the first stacked film to obtain the first stacked film after in-situ annealing; performing a second coating treatment on the surface of the first stacked film after in-situ annealing by means of ion beam sputtering, alternately depositing a third film layer and a fourth film layer on the surface of the first stacked film to obtain a second stacked film; performing a second in-situ annealing on the second stacked film to obtain a thin film; when alternately depositing the first film layer and the second film layer, bombarding the substrate surface with a microwave ion source or applying a bias to the substrate with a radio frequency bias; when alternately depositing the third film layer and the fourth film layer, bombarding the surface of the first stacked film with a microwave ion source; the materials of the film layers in the first stacked film and the second stacked film are different.

[0006] In some exemplary embodiments, the first film layer is amorphous silicon or hydrogenated amorphous silicon, the second film layer is silicon nitride, the third film layer is tantalum oxide, and the fourth film layer is silicon oxide.

[0007] In some exemplary embodiments, a first coating treatment is performed on the surface of a substrate by ion beam sputtering, and a first film layer and a second film layer are alternately deposited on the surface of the substrate to obtain a first stacked film, including: using a mixture of argon and hydrogen as a working gas, optionally with hydrogen as a reaction gas, and coating the surface of the substrate by ion beam sputtering using a silicon target to obtain a first film layer; using argon as a working gas and nitrogen as a reaction gas, and coating the surface of the first film layer by ion beam sputtering using a silicon target to obtain a second film layer; and alternately depositing the first film layer and the second film layer to obtain the first stacked film.

[0008] In some exemplary embodiments, a radio frequency bias is used to bias the substrate during the alternating deposition of the first film layer and the second film layer.

[0009] In some exemplary embodiments, during the preparation of the first film layer, the flow rate of the mixed gas is 10~100sccm, the volume percentage of hydrogen in the mixed gas is 5%, the power of ion beam sputtering is 200~600W, and the acceleration voltage is 200~1000V; during the preparation of the second film layer, the flow rate of argon gas is 10~100sccm, the power of ion beam sputtering is 200~600W, and the acceleration voltage is 200~1000V; the power of the RF bias is 50~200W.

[0010] In some exemplary embodiments, a second coating treatment is performed on the surface of the first stacked film after in-situ annealing by ion beam sputtering, and a third film layer and a fourth film layer are alternately deposited on the surface of the first stacked film to obtain the second stacked film, including: using argon as a working gas and oxygen as a reaction gas, and using a tantalum target to coat the surface of the first stacked film by ion beam sputtering to obtain a third film layer; using argon as a working gas and oxygen as a reaction gas, and using a silicon target to coat the surface of the third film layer by ion beam sputtering to obtain a fourth film layer; and alternately depositing the third film layer and the fourth film layer to obtain the second stacked film.

[0011] In some exemplary embodiments, before preparing the first stacked film, it also includes: performing atomic hydrogen cleaning on the substrate; during the atomic hydrogen cleaning, the hydrogen flow rate is 0.1~5sccm, the power of the atomic hydrogen source is 100~200W, the cleaning temperature is 150~300℃, and the cleaning time is 3~10min.

[0012] In some exemplary embodiments, the annealing temperature of the first in-situ annealing is 300-500° C., and the annealing time is 1-12 hours; the annealing temperature of the second in-situ annealing is 250-350° C., and the annealing time is 9-11 hours.

[0013] In some exemplary embodiments, the first stacked film has a period of 7, with one period consisting of an alternating layer of an amorphous silicon layer or a hydrogenated amorphous silicon layer and a silicon nitride layer; and the second stacked film has a period of 10.5, with one period consisting of an alternating layer of a tantalum oxide layer and a silicon oxide layer.

[0014] According to an embodiment of another aspect of the present invention, an ion beam sputtering coating device is provided for implementing the method as described above, wherein the ion beam sputtering coating device comprises: an injection chamber, suitable for transmitting a substrate; a main chamber, connected to the injection chamber, the main chamber comprising: a workpiece disk, located at the center of the top of the main chamber, suitable for fixing the substrate; a target material, fixed on a target material rotating shaft on the side wall of the main chamber; a sputtering ion source, located on the side wall of the main chamber opposite to the target material, suitable for sputtering target material particles from the target material by ion beam sputtering to coat the substrate; and a microwave ion source, located in the main chamber, on the opposite side of the workpiece disk, the microwave ion source being suitable for bombarding the substrate surface when alternately depositing film layer structures during the coating process.

[0015] In some exemplary embodiments, the ion beam sputtering coating apparatus further includes: an atomic hydrogen source located at a side wall in the main chamber, wherein the atomic hydrogen source is suitable for providing hydrogen atoms to clean the surface of the substrate.

[0016] According to an embodiment of the present invention, by first preparing a first stacked film by ion beam sputtering, and then preparing a second stacked film on the first stacked film by ion beam sputtering, the probability of thermal distortion can be reduced. Since the materials of each film layer in the first stacked film and the second stacked film are different, the thermal vibration inside the stacked material can be reduced, thereby ensuring better measurement accuracy, thereby reducing the impact of the film on the beam quality when it is subsequently applied to a high-reflection film; and different stacked materials can take into account that the film has a higher reflectivity, which is helpful for subsequent application as an ultra-high reflectivity medium film. In addition, since the first stacked film and the second stacked film use different materials, by introducing in-situ annealing, the sampling, transfer annealing, and reloading process between the first stacked film and the second stacked film is avoided, which can reduce the contamination of the film by human operation and exposure to the atmosphere, and can effectively improve the yield of the film. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0018] Figure 1A flow chart of a method for preparing a thin film by ion beam sputtering according to an embodiment of the present invention is shown;

[0019] Figure 2 A schematic structural diagram of an ion beam sputtering coating device according to an embodiment of the present invention is shown;

[0020] Figure 3 A graph showing the variation of the refractive index of the amorphous silicon thin film prepared in Example 1 and Example 2 of the present invention with respect to wavelength;

[0021] Figure 4 An ion mass spectrum of a stacked film of amorphous silicon and silicon oxide according to Example 3 of the present invention is shown.

[0022] In the drawings, the meanings of the reference numerals are as follows:

[0023] 1- injection chamber;

[0024] 101-transmission robot;

[0025] 102-injection chamber vent hole;

[0026] 2-Main chamber;

[0027] 3. Workpiece tray;

[0028] 4- Target material;

[0029] 5-Sputtering ion source;

[0030] 501-Sputtering ion source vent;

[0031] 6- Microwave ion source;

[0032] 601-microwave ion source vent;

[0033] 7- atomic hydrogen source;

[0034] 8- Power supply and control unit;

[0035] 9-injection chamber vacuum pump group;

[0036] 10-Main chamber vacuum pump set;

[0037] 11-light control unit;

[0038] 12-Target rotating shaft. DETAILED DESCRIPTION

[0039] Below, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of embodiments of the present invention. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of concepts of the present invention.

[0040] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The term "comprising" used herein indicates the existence of features, steps, operations, but does not exclude the existence or addition of one or more other features.

[0041] In the process of coating by ion beam sputtering, the preparation of high-quality thin films is achieved by superimposing the sputtering ion source and the auxiliary ion source. Among them, the sputtering ion source is suitable for sputtering target atoms, and the auxiliary ion source is suitable for modifying the thin film and achieving the smoothness of the film surface. From the perspective of different structures, the auxiliary ion source can also be divided into a DC ion source (also called a Kaufman source), a capacitive radio frequency ion source, an inductive radio frequency ion source, and an electron cyclotron resonance ion source (also called a microwave ion source).

[0042] In the process of preparing thin films for subsequent applications, it was found that, for example, in the field of gravitational wave detection, the conversion of thin film absorption of light into heat will cause thermal distortion of the mirror (which can be understood as the mirror or other optical surface where the thin film is located, which may undergo thermal expansion or other forms of deformation) affecting the beam quality, which leads to more stringent requirements for thin film absorption loss. In addition, thermal fluctuations inside the material, which can be understood as the random motion and position changes of particles caused by thermal energy, will cause changes in cavity length and affect the measurement accuracy in the form of Brownian thermal noise. Among them, the change in cavity length can be understood as the distance between two opposing mirrors in an optical resonant cavity (a device consisting of two opposing mirrors), so high requirements are also placed on the mechanical loss angle of the material. Similar requirements also exist in the ultra-stable cavity of optical atomic clocks, especially the material loss angle is one of the main factors currently limiting the stability of atomic clocks. At present, the oxide medium high-reflectivity film prepared by ion beam sputtering is difficult to meet the current demand for low-noise and high-reflectivity coatings due to poor low-temperature loss angle characteristics or the presence of thermal noise (thermal vibration).

[0043] In the process of realizing the concept of the present invention, it is found that by introducing the first stacked film and the second stacked film with different film materials during the ion beam sputtering process, the thermal vibration caused by thermal noise can be reduced or the low-temperature loss angle can be increased, which is conducive to expanding the subsequent application space. In addition, due to the in-situ annealing of the first stacked film and the second stacked film, the pollution caused by the sampling, transfer and loading processes during the two stacking processes is reduced.

[0044] Specifically, according to an embodiment of one aspect of the present invention, a method for preparing a thin film by ion beam sputtering is provided. Figure 1 FIG. 4 shows a flow chart of a method for preparing a thin film by ion beam sputtering according to an embodiment of the present invention. Figure 1 As shown, operations S101 to S104 are included.

[0045] In operation S101 , a first film coating process is performed on the surface of the substrate by ion beam sputtering, and a first film layer and a second film layer are alternately deposited on the surface of the substrate to obtain a first stacked film.

[0046] In operation S102 , a first in-situ annealing is performed on the first stacked film to obtain a first stacked film after in-situ annealing.

[0047] In operation S103, a second coating treatment is performed on the surface of the first stacked film after in-situ annealing by ion beam sputtering, and a third film layer and a fourth film layer are alternately deposited on the surface of the first stacked film to obtain a second stacked film.

[0048] In operation S104, a second in-situ annealing is performed on the second stacked film to obtain a thin film.

[0049] According to an embodiment of the present invention, the materials of each film layer in the first stacked film and the second stacked film are different. Based on the use of different materials, the probability of thermal distortion can be reduced, thereby having better measurement accuracy, and at the same time, the film has a higher reflectivity, which is helpful for subsequent use as an ultra-high reflectivity dielectric film. Based on the different materials of each film layer in the first stacked film and the second stacked film, the minimum absorption loss and thermal noise performance of the first stacked film and the second stacked film are obtained under different annealing conditions. By performing a first in-situ annealing on the first stacked film and a second in-situ annealing on the second stacked film, the sampling, transfer annealing (which can be understood as the contamination of the film during the transfer to the annealing equipment), and reloading processes between the first stacked film and the second stacked film are avoided, reducing the contamination of the film by personnel operation and exposure to the atmosphere, which helps to improve the yield of the film.

[0050] It should be noted that, for the coating of different stacked films of the present invention, when the optimal annealing temperatures of the first stacked film and the second stacked film are different, for example, a first in-situ annealing can be performed after the coating of the first stacked film is completed, and then the second stacked film can be returned to the main chamber to complete the coating, and then a second in-situ annealing can be performed.

[0051] According to an embodiment of the present invention, when the first film layer and the second film layer are alternately deposited, a microwave ion source is used to bombard the substrate surface or a radio frequency bias is used to apply a bias to the substrate. When the first stacked film is formed, the substrate surface is bombarded by the microwave ion source, and the mobility of the sputtered silicon or silicon nitride on the substrate surface is improved, thereby reducing the roughness of the surface of the first stacked film, improving the flatness of the surface of the formed first stacked film, and suppressing the loss of scattering on the surface of the first stacked film. The microwave ion source has precisely adjustable ion energy and flux, and can finely control the process parameters during the coating process, thereby helping to reduce the optical loss of the film layer. The radio frequency bias can clean the substrate surface or the surface of the deposited film layer during the deposition process, which helps to remove impurities and oxides, thereby increasing the bonding strength between the newly deposited film layer and the substrate or the lower film, and reducing the absorption loss. The first stacked film as a base layer can reduce thermal noise or have a better low-temperature loss angle. When the third film layer and the fourth film layer are alternately deposited, a microwave ion source is used to bombard the surface of the first stacked film. Similar to the above, the microwave ion source is used to promote atomic rearrangement in the film, which helps to form a dense and flat film structure, increase the bonding strength between the newly deposited film and the underlying film, and further reduce absorption losses.

[0052] In some embodiments, the first film layer is amorphous silicon or hydrogenated amorphous silicon, the second film layer is silicon nitride; the third film layer is tantalum oxide, and the fourth film layer is silicon oxide. In the process of conducting relevant preliminary experiments of the present invention, it was found that when the first film layer, the second film layer, the third film layer, and the fourth film layer are arranged as described above, the first stacked film can be used as a base layer to reduce thermal noise, so that the film has a better low-temperature loss angle; the second stacked film is used as a high-reflection film part, so that the film has high reflectivity. The film reduces thermal vibration while meeting the high reflectivity, thereby improving the accuracy of precision measurement, and can be subsequently applied to technical fields with high precision requirements, such as gravitational wave detection or atomic clocks.

[0053] Preferably, when alternately depositing the first film layer and the second film layer, a radio frequency bias is used to bias the substrate. When using a microwave ion source to bombard the substrate surface, it is found that part of the thin film material will be deposited on the grid of the microwave ion source. Since the ion beam sputtered film has a high stress, during a long period of coating, the film on the surface of the microwave ion source grid will accumulate a large stress and may disintegrate. The generated particles will reach and partially adsorb on the film structure with the ion beam, and then be covered by the subsequent coating, forming pollution that is difficult to remove, resulting in an increase in the scattering loss of the film. In this arrangement, since the radio frequency bias is based on the bias of the substrate for ion acceleration, no additional structures such as grids are required, which can effectively reduce particle contamination.

[0054] In addition, when preparing the first film layer, a microwave ion source is used to bombard the substrate surface. In order to separate the plasma from the RF coil, a quartz cup and other structures are used. However, the quartz cup will evaporate or sputter oxygen elements under the bombardment of high-density plasma, which will introduce oxygen contamination during the preparation of the low thermal noise optical film material of the first film layer (amorphous silicon or hydrogenated amorphous silicon), resulting in a decrease in the refractive index of the obtained film and poor low-temperature thermal noise performance. The use of RF bias does not involve structures such as quartz cups, which helps to avoid the introduction of oxygen contamination during the coating process of the first film layer and further reduce particle contamination.

[0055] According to an embodiment of the present invention, during the preparation process of the first stacked film, the introduction of radio frequency bias can replace the microwave ion source, further avoiding particle contamination and impurity element doping generated during the operation of the microwave ion source, improving the cleanliness of the film, reducing the impurity content, and helping to reduce the scattering loss and absorption loss of the film.

[0056] Operation S101 specifically includes sub-operations S1011 to S1013.

[0057] In sub-operation S1011, a mixture of argon and hydrogen is used as a working gas, hydrogen is optionally used as a reaction gas, and a silicon target is used to coat the surface of the substrate by ion beam sputtering to obtain a first film layer.

[0058] In sub-operation S1012, argon gas is used as a working gas, nitrogen gas is used as a reaction gas, and a silicon target is used to coat the surface of the first film layer by ion beam sputtering to obtain a second film layer.

[0059] In sub-operation S1013, the first film layer and the second film layer are alternately deposited to obtain a first stacked film.

[0060] According to an embodiment of the present invention, in sub-operation S1011, hydrogenated amorphous silicon is prepared when hydrogen is used as a reaction gas; and amorphous silicon is prepared when hydrogen is not used as a reaction gas. When hydrogenated amorphous silicon or amorphous silicon is subsequently used in fields where thermal noise may exist, it is possible to improve the resistance of the film to thermal noise and reduce the impact of thermal noise on the film. In sub-operation S1012, the prepared silicon nitride helps to further improve the wear resistance and corrosion resistance of the first stacked film, and in subsequent applications in fields such as optical resonant cavities, it is possible to reduce the impact of thermal noise on the film. In sub-operation S1013, silicon nitride is used in conjunction with amorphous silicon or hydrogenated amorphous silicon to further reduce thermal noise and enhance performance such as low-temperature loss angle.

[0061] It can be understood that the absorption loss of amorphous silicon / hydrogenated amorphous silicon in the band tail region is mainly related to the impurities, defects, atomic structure, etc. in the above materials. The band tail region can be understood as the formation of a new energy level near the valence band or conduction band in the forbidden band. During the coating process, the background gas, substrate, impurities on the target surface, and the influence of the coating process on the atomic structure may cause the increase of the film absorption loss.

[0062] It should be noted that in the process of preparing the film, it was found that if only the first stacked film is prepared, although the film has better resistance to thermal noise and is beneficial to enhancing the low-temperature loss angle of the film, the above-mentioned material has a large absorption of light, making the reflectivity of the film low, and it is difficult to use it as a high-reflection film for subsequent applications.

[0063] In some embodiments, during the preparation of the first film layer, the flow rate of the mixed gas is 10-100 sccm, for example, 10 sccm, 20 sccm, 30 sccm, 40 sccm, 50 sccm, 60 sccm, 70 sccm, 80 sccm, 90 sccm or 100 sccm, preferably 50 sccm; the volume percentage of hydrogen in the mixed gas is 5%. The power of ion beam sputtering is 200-600 W, for example, 200 W, 300 W, 400 W, 500 W or 600 W, preferably 400 W. The acceleration voltage is 200-1000 V, for example, 200 V, 300 V, 400 V, 500 V, 600 V, 700 V, 800 V, 900 V or 1000 V, preferably 800 V. A bias voltage is applied to the substrate by radio frequency bias, and the power of the radio frequency bias voltage is 50-200W, for example, 50W, 100W, 150W or 200W.

[0064] In some embodiments, during the preparation of the second film layer, the flow rate of argon gas is 10-100 sccm, for example, 10 sccm, 20 sccm, 30 sccm, 40 sccm, 50 sccm, 60 sccm, 70 sccm, 80 sccm, 90 sccm or 100 sccm, preferably 50 sccm; the power of ion beam sputtering is 200-600 W, for example, 200 W, 300 W, 400 W, 500 W or 600 W, preferably 400 W, and the acceleration voltage is 200-1000 V, for example, 200 V, 300 V, 400 V, 500 V, 600 V, 700 V, 800 V, 900 V or 1000 V, preferably 800 V. A bias is applied to the substrate by a radio frequency bias, and the power of the radio frequency bias is 50-200 W, for example, 50 W, 100 W, 150 W or 200 W.

[0065] Operation S103 includes sub-operations S1031 to S1033.

[0066] In sub-operation S1031, argon gas is used as a working gas, oxygen is used as a reaction gas, and a tantalum target is used to coat the surface of the first stacked film by ion beam sputtering to obtain a third film layer.

[0067] In sub-operation S1032, argon gas is used as a working gas, oxygen is used as a reaction gas, and a silicon target is used to coat the surface of the third film layer by ion beam sputtering to obtain a fourth film layer.

[0068] In sub-operation S1033, the third film layer and the fourth film layer are alternately deposited to obtain a second stacked film.

[0069] According to an embodiment of the present invention, in sub-operation S1031, argon gas is used as the working gas, and the deposited film can be etched in the ion beam sputtering state, so as to optimize the absorption loss and surface roughness of the film. Using oxygen as a reaction gas helps to form a tantalum oxide film, and the tantalum oxide film provides better reflectivity to light, which is conducive to the subsequent preparation of a high-reflective film. In sub-operation S1032, the prepared silicon oxide helps to further enhance the reflective effect of the film. In sub-operation S1033, the reflectivity is further improved by the coordinated use of tantalum oxide and silicon oxide to meet the higher requirements for reflectivity in technical fields such as optical resonant cavities.

[0070] In some embodiments, during the preparation of the third film layer, the argon flow rate is 10-100 sccm, for example, 10 sccm, 20 sccm, 30 sccm, 40 sccm, 50 sccm, 60 sccm, 70 sccm, 80 sccm, 90 sccm or 100 sccm, preferably 50 sccm. The power of the ion beam sputtering is 200-600 W, for example, 200 W, 300 W, 400 W, 500 W or 600 W, preferably 500 W. The acceleration voltage is 200-1000 V, for example, 200 V, 300 V, 400 V, 500 V, 600 V, 700 V, 800 V, 900 V or 1000 V, preferably 800 V. The oxygen flow rate of the microwave ion source is 10-50 sccm, for example, 10 sccm, 20 sccm, 30 sccm, 40 sccm or 50 sccm, preferably 50 sccm. The power of the microwave ion source is 200-400 W, for example, 200 W, 300 W or 400 W, preferably 300 W. The acceleration voltage is 20-400 V, for example, 20 V, 50 V, 100 V, 200 V, 300 V or 400 V, preferably 50 V.

[0071] In some embodiments, during the preparation of the fourth film layer, the flow rate of argon gas is 10~100sccm, for example, it can be 10sccm, 20sccm, 30sccm, 40sccm, 50sccm, 60sccm, 70sccm, 80sccm, 90sccm or 100sccm, and is preferably 50sccm; the power of ion beam sputtering is 200~600W, for example, it can be 200W, 300W, 400W, 500W or 600W, and is preferably 400W; the acceleration voltage is 200~1000V, for example, it can be 200V, 300V, 400V, 500V, 600V, 700V, 800V, 900V or 1000V, and is preferably 800V. The flow rate of oxygen introduced into the microwave ion source is 10-50 sccm, for example, 10 sccm, 20 sccm, 30 sccm, 40 sccm or 50 sccm, preferably 25 sccm. The bombardment power is 200-400 W, for example, 200 W, 300 W or 400 W, preferably 300 W. The acceleration voltage is 20-400 V, for example, 20 V, 50 V, 100 V, 200 V, 300 V or 400 V, preferably 150 V.

[0072] It should be noted that this embodiment utilizes a distributed Bragg reflector structure based on an alternating stacked structure formed by the third film layer and the fourth film layer (high refractive index oxide, low refractive index oxide), which can effectively reduce scattering losses and make the prepared thin film have a higher reflectivity.

[0073] In some embodiments, before operation S101, the process further includes: performing atomic hydrogen cleaning on the substrate. Atomic hydrogen cleaning can be understood as converting the introduced hydrogen gas into hydrogen atoms, which combine with the oxygen on the surface of the substrate to form water that is pumped away. The substrate includes crystalline silicon. When crystalline silicon is stored in an atmospheric environment, a thin oxide layer will form on the surface, which will increase the surface roughness of the substrate and cause surface adsorption contamination, thereby further affecting the optical properties of the deposited film and causing poor adhesion in some parts of the film. By introducing atomic hydrogen cleaning, the oxide layer can be removed in a gentle manner before the coating begins.

[0074] Preferably, in atomic hydrogen cleaning, the flow rate of hydrogen is 0.1-5 sccm, for example, 0.1 sccm, 1 sccm, 2 sccm, 3 sccm, 4 sccm or 5 sccm, preferably 1 sccm; the power of the atomic hydrogen source is 100-200 W, for example, 100 W, 150 W or 200 W, preferably 160 W. The cleaning temperature (which can be understood as the substrate heating temperature) is 150-300 ° C, for example, 150 ° C, 200 ° C, 250 ° C or 300 ° C, and the cleaning time is 3-10 min, for example, 3 min, 5 min, 7 min, 9 min or 10 min. Atomic hydrogen cleaning helps to remove residual contaminants on the substrate surface and optimize the surface roughness of the substrate.

[0075] In some embodiments, the annealing temperature of the first in-situ annealing is 300-500°C, for example, 300°C, 400°C or 500°C, preferably 400°C. The annealing time is 1-12h, for example, 1h, 4h, 8h or 12h, preferably 1h. The first in-situ annealing can be performed by, for example, transferring the first stacked film from the main chamber to the injection chamber through a transfer robot arm for in-situ annealing, and after the first stacked film is annealed and cooled to room temperature, it is then transferred to the main chamber through a transfer robot arm to prepare the second stacked film.

[0076] In some embodiments, the annealing temperature of the second in-situ annealing is 250-350°C, for example, 250°C, 300°C or 350°C, preferably 300°C. The annealing time is 9-11h, for example, 9h, 10h or 11h, preferably 10h. For the different materials of the first stacked film and the second stacked film, the minimum absorption loss and thermal noise performance of the two stacked films are obtained under different annealing conditions. After the first in-situ annealing is completed, the second in-situ annealing is performed. Since the annealing temperature of the second in-situ annealing is lower than that of the first in-situ annealing, it is possible to reduce damage to the first stacked film while forming the second stacked film, so that the prepared film has good reflectivity while reducing thermal vibration, further improving the accuracy of precise measurement of the film.

[0077] It should be noted that the in-situ annealing process can be performed in a vacuum, or in an atmosphere of nitrogen, oxygen, hydrogen, etc.

[0078] In some embodiments, the first stacked film has a stacking period of 7, with a layer of amorphous silicon or hydrogenated amorphous silicon and a layer of silicon nitride forming an alternating layer as one period; the second stacked film has a stacking period of 10.5, with a layer of tantalum oxide and a layer of silicon oxide forming an alternating layer as one period. It was found during the preliminary experiments related to the present invention that when the stacking period numbers are the above values, the prepared thin film is relatively smoother, has a higher reflectivity, and has a better resistance to thermal vibration.

[0079] According to another embodiment of the present invention, the present invention provides an ion beam sputtering coating device for implementing the above method. Figure 2 FIG. 4 shows a schematic structural diagram of an ion beam sputtering coating device according to an embodiment of the present invention. Figure 2 As shown, the ion beam sputtering coating device includes: a sample injection chamber 1, a main chamber 2, a workpiece disk 3, a target material 4, a sputtering ion source 5, and a microwave ion source 6.

[0080] The injection chamber 1 is suitable for transmitting and receiving substrates, for example, the substrate is placed through the injection chamber 1, or the substrate is transferred back to the injection chamber 1 for the first in-situ annealing after the first laminated film is prepared, or the substrate is transferred back to the injection chamber 1 for the second in-situ annealing after the second laminated film is prepared, so as to avoid the film from contacting with the atmospheric environment and reduce the contamination of the film surface. The main chamber 2 is made of stainless steel, and the main chamber 2 is connected to the injection chamber 1 to facilitate the mutual transmission of the substrate between the two. The main chamber 2 includes a workpiece disk 3, a radio frequency power supply (not shown in the figure), a target material 4, a sputtering ion source 5, a microwave ion source 6 and other components, and the main chamber and each component can be connected by a flange as needed. The workpiece disk 3 is located at the center of the top of the main chamber 2 and is suitable for fixing the substrate. The workpiece disk 3 has a workpiece disk support (not shown in the figure), which is compatible with workpiece disks 3 larger than 12 inches. The workpiece disk 3 can be heated during the coating process, and the temperature can be adjusted in the range of room temperature to 300°C, and the temperature control accuracy is better than ±0.1°C. In addition, the workpiece disk 3 can be driven to rotate to improve the uniformity of the coating, and the maximum number of revolutions can reach 1000rpm. The RF power supply is electrically connected to the workpiece disk 3, and is suitable for providing RF bias to the substrate when alternately depositing the film layer structure. The workpiece disk 3 is electrically connected to the RF power supply, so that an RF bias is applied to the substrate during the coating process to generate plasma, which can be used for substrate cleaning and auxiliary coating, and can have a similar effect to the microwave ion source 6, while avoiding particle contamination and material contamination generated by the ion source.

[0081] The target material 4 is fixed on the target material rotating shaft 12 on the side wall of the main chamber 2. The target material rotating shaft 12 can be a polyhedral structure, and targets 4 of different materials can be fixed separately as needed. When different targets are needed, they can be directly used by rotating the target material rotating shaft 12, avoiding the complicated operation caused by repeated replacement. The target material rotating shaft 12 can be, for example, Figure 2 The sputtering ion source 5 is located on the side of the side wall of the main chamber 2 opposite to the target material 4. It should be noted that the side wall of the main chamber 2 can be understood as the side wall on the left and right sides of the main chamber 2, for example, Figure 2As shown, the target material 4 is located on the right side of the main chamber 2, and the sputtering ion source 5 is located on the left side of the main chamber 2; alternatively, the target material 4 is located on the left side of the main chamber 2, and the sputtering ion source 5 is located on the right side of the main chamber 2. The sputtering ion source 5 provides a main ion source, which is suitable for sputtering target material particles from the target material 4 by ion beam sputtering to perform film coating on the substrate. The diameter of the sputtering ion source 5 is ≥16 cm, and the maximum power can reach 600 W; the microwave ion source 6 is located in the main chamber 2, the diameter of the microwave ion source 6 is greater than or equal to 12 cm, and the maximum power can reach 400 W. The microwave ion source 6 is located on the opposite side of the workpiece disk 3, for example, it can be as follows Figure 2 As shown, it is located at the center of the bottom of the main chamber 2 and is suitable for bombarding the substrate surface when alternately depositing film layer structures to increase the migration length of the sputtered material on the substrate surface, thereby reducing the roughness of the substrate surface, improving the flatness of the formed film surface, and suppressing the loss of scattering on the film surface.

[0082] It can be understood that the main structure of the ion beam sputtering coating device mainly includes a sputtering ion source 5, a target material 4, a substrate and a microwave ion source 6. The sputtering ion source 5 is directly fixed in the main chamber 2 by a flange, the target material 4 is first fixed on the target material rotating shaft 12, and the target material rotating shaft 12 is further fixed in the main chamber 2. During the sputtering process, the base (not shown in the figure) of the target material 4 can also swing to improve the utilization rate of the target material. The microwave ion source 6 is fixed in the main chamber 2 by a flange, and the substrate is fixed on the workpiece disk 3, and the workpiece disk 3 is further fixed in the main chamber 2. The sputtering ion source 5 is tilted toward the target material 4 at a certain angle (the specific angle is related to the ion type and the target material), and the generated ion beam sputters the target material particles from the target material 4. There is also a certain angle between the target material 4 and the substrate to maximize the utilization rate of the target material 4. In addition, the microwave ion source 6 is also tilted toward the substrate and the workpiece disk 3 at a certain angle, and the angle selection is mainly to prevent the microwave ion beam from hitting the substrate and the workpiece disk 3. The RF power supply is connected to the workpiece disk 3 via a capacitor (not shown in the figure) to generate a RF bias voltage for cleaning the substrate before coating or assisting the coating process.

[0083] To avoid frequent destruction of the vacuum atmosphere during manual placement, which will affect the cleanliness of the equipment. The injection chamber 1 is also provided with a conveying robot 101 and an injection chamber vent 102, wherein the conveying robot 101 is suitable for conveying substrates, and the injection chamber vent 102 is suitable for removing the vacuum state of the injection chamber 1. The injection chamber vacuum pump group 9 is connected to the injection chamber 1, and the injection chamber vacuum pump group 9 is suitable for vacuuming the injection chamber 1. During normal use, the substrate is first fixed to the workpiece disk 3, and then placed in the injection chamber 1. After the injection chamber vacuum pump group 9 is initially vacuumed, the workpiece disk 3 can be sent to the main chamber 2 together with the substrate through the conveying robot 101. The injection chamber 1 is also equipped with a heating unit (not shown in the figure) as needed for in-situ annealing of the laminated film. The injection chamber vacuum pump group 9 includes a dry pump and a molecular pump, so that the vacuum degree of the injection chamber 1 can reach below 5E-6Torr.

[0084] In some embodiments, the ion beam sputtering coating device further comprises a main chamber vacuum pump group 10, which comprises a dry pump, a molecular pump and a cold pump, and can make the main chamber 2 reach a vacuum degree below 2E-8Torr. During the coating process, due to the introduction of working gas and reaction gas, the vacuum degree of the main chamber 2 is maintained at 10 -5 ~10 -4 The sputtering ion source 5 also has a sputtering ion source vent 501, which is suitable for providing working gas and / or reaction gas to the main chamber 2. The microwave ion source 6 also has a microwave ion source vent 601, which is suitable for providing reaction gas and / or working gas to the main chamber 2.

[0085] In some embodiments, the ion beam sputtering coating device further includes a power supply and control unit 8, which is suitable for providing power to each component and regulating each component separately to achieve the control of water, electricity, and gas of the ion beam sputtering coating device, as well as the setting and recording of the coating process. The main chamber 2 also includes a light control unit 11, which detects the coating thickness through the light control unit 11. When the film thickness reaches the set value (when the wavelength is 1397nm, the film thickness is equal to , n is the refractive index of the film at 1397nm pre-calibrated by the ellipsometer), the sputtering ion source 5 and the microwave ion source 6 are stopped, and the preparation process of the film is completed. The light control unit 11 monitors the film thickness through the spectrum, thereby assisting the ion beam sputtering coating device to accurately coat the film according to the designed film structure.

[0086] It should be noted that Figure 2 It is mainly used to illustrate the relative positional relationship between various components. For example, the workpiece disk 3 can also be arranged on the side wall of the main chamber 2, and other components can be adjusted accordingly as needed.

[0087] In some embodiments, the ion beam sputtering coating device also includes an atomic hydrogen source 7, which is located at the side wall of the main chamber 2. The atomic hydrogen source 7 is suitable for converting the introduced hydrogen gas into hydrogen atoms to clean the substrate surface (combine with oxygen on the substrate surface), remove the native oxide layer on the substrate surface, and form water to be pumped away.

[0088] According to the embodiments of the present invention, the ion beam sputtering coating device of the present invention can achieve ultra-high vacuum, pre-coating cleaning of the target material and the substrate, has highly adjustable ion beam parameters, can minimize the material contamination caused by the coating process, and more finely optimize the coating process parameters, thereby achieving low-noise and high-reflectivity mirror coating with atomic-level flatness and ultra-low absorption loss.

[0089] Furthermore, the ion beam sputtering coating device of the present invention can achieve ultra-high background vacuum (the background represents the non-working state, that is, the ultra-high vacuum state that the equipment can reach before coating), pre-cleaning of the target material and the substrate, real-time monitoring of the coating rate, microwave ion source assisted deposition, in-situ annealing and other functions, thereby reducing the absorption loss of high-reflectivity films, and is suitable for the coating of low thermal noise materials such as amorphous silicon and silicon nitride.

[0090] The following is an explanation of the high-reflective film coating of amorphous silicon, silicon nitride, tantalum oxide, and silicon oxide mixed system with a central wavelength of 1397nm.

[0091] Sampling: After the ultra-fine polished silicon substrate is cleaned and dried by a cleaning machine, it is clamped on the workpiece tray and placed in the sampling chamber; the sampling chamber is evacuated to a vacuum degree less than 1E-4Torr, at this time, the baffle valve between the sampling chamber and the main chamber is opened, and the workpiece tray is sent to the tray of the main chamber by the robot arm, the baffle valve is closed, and the main chamber is evacuated to a vacuum degree less than 2E-8Torr.

[0092] Substrate pre-cleaning: Use an atomic hydrogen source to clean the substrate with hydrogen atoms. The hydrogen flow rate can be selected from 0 to 5 sccm, preferably 1 sccm; the atomic hydrogen source power can be selected from 100 to 200 W, preferably 160 W; the substrate temperature is heated to 150 to 300 ° C, preferably 250 ° C; the cleaning time is 3 to 10 minutes. It mainly plays the role of removing residual contaminants on the substrate surface and optimizing the surface roughness of the substrate.

[0093] Amorphous silicon coating: Turn the target shaft and rotate the silicon target (the first silicon target) to a position suitable for sputtering. Start the sputtering ion source to ionize and accelerate the argon gas to sputter the target atoms. At this time, start the microwave ion source synchronously, and use an argon-hydrogen mixed gas as the microwave ion source gas source to hydrogenate and etch the deposited film, thereby optimizing the absorption loss and surface roughness of the film; the flow rate of the argon-hydrogen mixed gas introduced into the sputtering ion source can be selected from 10 to 100 sccm, the hydrogen ratio is 5%, preferably 50 sccm, the power can be selected from 200 to 600 W, preferably 400 W, and the acceleration voltage can be selected from 200 to 1000 V, preferably 800 V; do not use an auxiliary ion source, but bias the workpiece disk through a radio frequency bias, which can be selected from 50 to 200 W, preferably 100 W. Use the light control module to monitor the film thickness. When the film thickness reaches the set value (the film thickness is equal to , is the refractive index of the amorphous silicon film at 1397 nm calibrated in advance by the ellipsometer), the sputtering ion source and the microwave ion source were stopped, and the vacuum was evacuated to 2E-8 Torr.

[0094] Silicon nitride coating: Turn the target shaft and rotate the silicon target (the second silicon target) to a position suitable for sputtering. Start the sputtering ion source, and sputter the target atoms by ionizing and accelerating the argon gas. At this time, start the microwave ion source synchronously, and use nitrogen as the ion source gas source to nitride and etch the deposited film, thereby optimizing the absorption loss and surface roughness of the film; the argon flow rate of the sputtering ion source can be selected from 10~100sccm, preferably 50sccm, the power can be selected from 200~600W, preferably 400W, and the acceleration voltage can be selected from 200~1000V, preferably 800V; do not use an auxiliary ion source, but bias the workpiece disk through a radio frequency bias, which can be selected from 50~200W, preferably 100W. Use the light control module to monitor the film thickness. When the film thickness reaches the set value (the film thickness is equal to , The sputtering ion source and the microwave ion source were stopped and the vacuum was evacuated to 2E-8 Torr.

[0095] Preparation of the first stacked film: Taking the 1397nm high-reflection mirror coating as an example, the steps of preparing amorphous silicon coating and silicon nitride coating can be performed alternately, and a total of 7 pairs are prepared.

[0096] First in-situ annealing: After the coating is completed, open the flapper valve between the injection chamber and the main chamber, take the workpiece plate to the injection chamber through the robot arm, close the flapper valve, and perform in-situ annealing in the injection chamber at a temperature of 400°C for 1 hour. After the sample annealing is completed and cooled to room temperature, it is transferred to the main chamber for the second stack film coating.

[0097] Tantalum oxide coating: Rotate the target shaft and rotate the tantalum target to a position suitable for sputtering. Start the sputtering ion source, ionize and accelerate the argon gas to sputter the target atoms. At this time, start the microwave ion source synchronously, and use an argon-hydrogen mixed gas as the ion source gas source to oxidize and etch the deposited film, thereby optimizing the absorption loss and surface roughness of the film; the argon flow rate of the sputtering ion source can be selected from 10 to 100 sccm, preferably 50 sccm, the power can be selected from 200 to 600 W, preferably 500 W, and the acceleration voltage can be selected from 200 to 1000 V, preferably 800 V; the oxygen flow rate of the microwave ion source can be selected from 10 to 50 sccm, preferably 45 sccm, the power can be selected from 200 to 400 W, preferably 300 W, and the acceleration voltage can be selected from 20 to 400 V, preferably 50 V. Use the light control module to monitor the film thickness. When the film thickness reaches the set value (the film thickness is equal to , is the refractive index of the tantalum oxide film at 1397 nm calibrated in advance by the ellipsometer), the sputtering ion source and the microwave ion source were stopped, and the vacuum was evacuated to 2E-8 Torr.

[0098] Silicon oxide coating: Turn the target shaft and rotate the silicon target (the third silicon target) to a position suitable for sputtering. Start the sputtering ion source, and sputter the target atoms by ionizing and accelerating the argon gas. At this time, start the microwave ion source synchronously, and use nitrogen as the ion source gas source to oxidize and etch the deposited film, thereby optimizing the absorption loss and surface roughness of the film; the argon flow rate of the sputtering ion source can be selected from 10~100sccm, preferably 50sccm, the power can be selected from 200~600W, preferably 400W, and the acceleration voltage can be selected from 200~1000V, preferably 800V; the oxygen flow rate of the microwave ion source can be selected from 10~50sccm, preferably 25sccm, the power can be selected from 200~400W, preferably 300W, and the acceleration voltage can be selected from 20~400V, preferably 150V. Use the light control module to monitor the film thickness. When the film thickness reaches the set value (the film thickness is equal to , The sputtering ion source and the microwave ion source were stopped and the vacuum was evacuated to 2E-8 Torr.

[0099] Preparation of the second stacked film: Taking the 1397nm high-reflection mirror coating as an example, the steps of preparing tantalum oxide coating and silicon oxide coating can be performed alternately, for a total of 10.5 pairs.

[0100] Second in-situ annealing: After the coating is completed, open the flapper valve between the injection chamber and the main chamber, take the workpiece plate to the injection chamber through the robotic arm, close the flapper valve, and perform in-situ annealing in the injection chamber at a temperature of 300°C for 10 hours. After the sample annealing is completed and cooled to room temperature, nitrogen can be introduced into the injection chamber to break the vacuum, and then the sample can be taken out to obtain a thin film.

[0101] Based on this, the present invention introduces a substrate RF bias during the process of coating a low thermal noise film layer in an ion beam sputtering coating device, which can replace the auxiliary ion source during the coating process of the low thermal noise film layer, and can avoid particle contamination and impurity element doping generated during the operation of the auxiliary ion source, thereby improving the cleanliness of the film, reducing the impurity content, and helping to reduce the film scattering loss and absorption loss.

[0102] In addition, the introduction of in-situ annealing function in the ion beam sputtering coating device can avoid contamination of the film during the transfer to the annealing equipment. It is especially suitable for the coating of mixed systems. When the optimal annealing temperatures of the bottom film system (the first stacked film) and the top film system (the second stacked film) are different, the first annealing can be performed after the bottom film system is coated, and then return to the main chamber to complete the top film system coating, and then perform the second annealing.

[0103] The present invention introduces an atomic hydrogen source into an ion beam sputtering coating device to treat the silicon substrate before coating, removes the native oxide layer on the substrate surface without destroying the surface roughness of the substrate, and helps to reduce the optical loss of the mirror. The present invention uses a microwave ion source as an auxiliary source, has a precisely adjustable ion energy and flux, and can achieve fine control of process parameters during the coating process, thereby reducing the optical loss of the mirror.

[0104] The present invention tests the influence of using an auxiliary ion source and substrate RF bias on thin films based on different examples, wherein Example 1 is an amorphous silicon thin film prepared by using RF bias on an ion beam sputtering coating device, and Example 2 is an amorphous silicon thin film prepared by using an auxiliary ion source under the same parameter conditions as Example 1. The refractive index of the amorphous silicon thin films of Examples 1 and 2 is tested. Figure 3 The graphs showing the variation of the refractive index of the amorphous silicon thin films prepared in Examples 1 and 2 of the present invention with respect to wavelength are shown. Figure 3 As shown, it can be seen that the auxiliary ion source ( Figure 3 ion source) and RF bias ( Figure 3The refractive index of amorphous silicon films prepared by the auxiliary ion source method (with substrate bias in the method) has a large difference. The refractive index of amorphous silicon films prepared by the auxiliary ion source method is significantly lower than that of the substrate bias method. When the amorphous silicon film obtained by the auxiliary ion source method is used to prepare a high-reflective film, due to the reduction in the refractive index difference between the amorphous silicon layer and silicon oxide (or other low-refractive index materials), more film layer pairs are required to achieve the same refractive index as the substrate bias method, and the increase in film thickness will increase the thermal noise of the film accordingly, limiting the sensitivity of the corresponding precision measurement device.

[0105] The performance of the amorphous silicon film prepared in Example 1 is similar to that of the amorphous silicon film prepared by magnetron sputtering, indicating that amorphous silicon or hydrogenated amorphous silicon prepared using substrate bias has a better refractive index than that prepared using an auxiliary ion source.

[0106] In order to further understand the reason why the refractive index of amorphous silicon thin films prepared by the auxiliary ion source method decreases, a test was conducted, in which Example 3 was to first deposit an amorphous silicon thin film of about 100 nm on a silicon substrate, and then deposit an about 100 nm silicon oxide thin film. The elements in the film layer of Example 3 were characterized using secondary ion mass spectrometry. Figure 4 FIG. 4 shows an ion mass spectrum of a stacked film of amorphous silicon and silicon oxide of Example 3 of the present invention. Figure 4 As shown in the figure, the oxygen signal in the amorphous silicon film (a-Si film layer in the figure) is still significantly higher than that in the substrate, which indicates that when the amorphous silicon film is deposited in the auxiliary ion source, oxygen will be doped in the film, resulting in a decrease in the refractive index. According to the analysis of the ion source structure, the main source of oxygen is the quartz cup in the ion source. When the ion source is working, higher energy ions will bombard the quartz cup, sputtering oxygen from it, resulting in oxygen contamination in the amorphous silicon film.

[0107] In the process of conducting relevant example experiments, it was found that as the temperature decreases, the loss angle of the silicon oxide film will show a trend of first rising and then falling. Therefore, although its loss angle at room temperature can reach 5E-5, the material loss angle at 10K (-263℃) is as high as 8E-4, which will have a relatively adverse effect on the thermal noise of the film at low temperatures. Theoretically, oxygen contamination in amorphous silicon will also have a similar effect, worsening the low-temperature loss angle of amorphous silicon. Therefore, RF bias, atomic hydrogen source and other components are integrated in the ion beam sputtering coating device to reduce oxygen contamination during the deposition of amorphous silicon films and improve the low-temperature noise performance of the film.

[0108] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a thin film by ion beam sputtering, characterized in that: include: Performing a first coating treatment on the surface of the substrate by ion beam sputtering, alternately depositing a first film layer and a second film layer on the surface of the substrate to obtain a first laminated film; Performing a first in-situ annealing on the first stacked film to obtain a first stacked film after in-situ annealing; Performing a second coating treatment on the surface of the first stacked film after in-situ annealing by ion beam sputtering, and alternately depositing a third film layer and a fourth film layer on the surface of the first stacked film to obtain a second stacked film; performing a second in-situ annealing on the second stacked film to obtain a thin film; When alternately depositing the first film layer and the second film layer, a microwave ion source is used to bombard the substrate surface or a radio frequency bias is used to apply a bias to the substrate; when alternately depositing the third film layer and the fourth film layer, a microwave ion source is used to bombard the surface of the first stacked film; the materials of each film layer in the first stacked film and the second stacked film are different.

2. The method according to claim 1, characterized in that The first film layer is amorphous silicon or hydrogenated amorphous silicon, and the second film layer is silicon nitride; The third film layer is tantalum oxide, and the fourth film layer is silicon oxide.

3. The method according to claim 2, characterized in that The first coating treatment is performed on the substrate surface by ion beam sputtering, and the first film layer and the second film layer are alternately deposited on the substrate surface to obtain the first laminated film, which includes: Using a mixture of argon and hydrogen as a working gas, optionally using hydrogen as a reaction gas, and using a silicon target to coat the surface of the substrate by ion beam sputtering to obtain the first film layer; Using argon as working gas and nitrogen as reaction gas, using silicon target material to coat the surface of the first film layer by ion beam sputtering to obtain the second film layer; The first film layer and the second film layer are alternately deposited to obtain the first stacked film.

4. The method according to claim 2, characterized in that: A radio frequency bias is used to bias the substrate during the alternating deposition of the first film layer and the second film layer.

5. The method according to claim 2, characterized in that: The second coating treatment is performed on the surface of the first stacked film after in-situ annealing by ion beam sputtering, and the third film layer and the fourth film layer are alternately deposited on the surface of the first stacked film to obtain the second stacked film, comprising: Using argon as working gas and oxygen as reaction gas, a tantalum target is used to plate the surface of the first stacked film by ion beam sputtering to obtain the third film layer; Using argon as working gas and oxygen as reaction gas, the surface of the third film layer is coated by ion beam sputtering using a silicon target to obtain the fourth film layer; The third film layer and the fourth film layer are deposited alternately to obtain the second stacked film.

6. The method according to claim 1, characterized in that Before preparing the first laminated film, the method further comprises: The substrate is cleaned with atomic hydrogen.

7. The method according to claim 1, characterized in that The annealing temperature of the first in-situ annealing is 300-500° C., and the annealing time is 1-12 hours; The annealing temperature of the second in-situ annealing is 250-350° C., and the annealing time is 9-11 hours.

8. The method according to claim 2, characterized in that: A layer of amorphous silicon or hydrogenated amorphous silicon and a layer of silicon nitride are alternately layered as one period, and the number of the stacking periods of the first stacked film is 7; One period is composed of an alternating layer of a tantalum oxide layer and a silicon oxide layer. The number of the stacking periods of the second stacked film is 10.

5.

9. An ion beam sputtering coating device, used to implement the method according to any one of claims 1 to 8, characterized in that: The ion beam sputtering coating device comprises: An injection chamber, suitable for transferring a substrate; A main chamber is connected to the injection chamber, and the main chamber includes: a workpiece plate, located at the center of the top of the main chamber, suitable for fixing the substrate; A radio frequency power supply, electrically connected to the workpiece disk, adapted to provide a radio frequency bias voltage to the substrate when alternately depositing a film layer structure; A target material is fixed on a target material rotating shaft on a side wall of the main chamber; A sputtering ion source, located on a side of the side wall of the main chamber opposite to the target material, is suitable for sputtering target material particles from the target material by ion beam sputtering to perform film coating on the substrate; A microwave ion source is located in the main chamber and on the opposite side of the workpiece disk. The microwave ion source is suitable for bombarding the substrate surface during the alternate deposition of film layer structures.

10. The ion beam sputtering coating device according to claim 9, characterized in that: The ion beam sputtering coating device also includes: An atomic hydrogen source is located at a side wall of the main chamber, and the atomic hydrogen source is suitable for providing hydrogen atoms to clean the surface of the substrate.

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