Method for preparing thin film by ion beam sputtering, ion beam sputtering coating device

Abstract

The present invention provides a method for preparing a thin film by ion beam sputtering and an ion beam sputtering coating device, belonging to the technical field of ion beam sputtering. The method includes: performing a first coating treatment on the surface of a 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 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 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. The method of the present invention can reduce the thermal noise inside the stacked film during the preparation process of the multi-stacked film. At the same time, through two in-situ annealings, the contamination of the thin film caused during the sampling, transfer, and loading processes from the first stacked film to the second stacked film is reduced.

Description

Technical Field

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

[0002] Dielectric optical thin 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 thin films, which generally includes methods such as electron beam evaporation, magnetron sputtering, ion beam sputtering, and ion-assisted deposition. If sorted according to the energy of thin film atoms during deposition in the coating process, it is usually ion beam sputtering > magnetron sputtering approximately equal to ion-assisted deposition > electron beam evaporation, and the sorting of the density and surface roughness of the corresponding thin films is also generally the same. When the density of the thin film is poor, the refractive index of the film layer is likely to change due to water vapor absorption, and the large surface roughness will also cause significant scattering loss. Therefore, at present, most of the ultra-high reflectivity dielectric thin films are prepared by the ion beam sputtering method.

[0003] In adapting to different application scenarios, the requirements for the performance parameters of ultra-high reflectivity dielectric thin films prepared by ion beam sputtering are also different. For example, in the field of gravitational wave detection, the absorption of light by the thin film and the conversion into heat may cause thermal distortion of the mirror, affecting the beam quality, thus leading to more stringent requirements for the absorption loss of the thin film. 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 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 ion beam sputtering is provided, including: performing a first coating process on the surface of a 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 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 process on the surface of the first stacked film after in-situ annealing by 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 surface of the substrate with a microwave ion source or applying a bias voltage to the substrate using 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 each film layer in the first stacked film and the second stacked film are different.

[0006] In some illustrative 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 illustrative embodiments, the first coating process is performed on the surface of the substrate by ion beam sputtering. The first film layer and the second film layer are alternately deposited on the surface of the substrate to obtain a first stacked film, including: using a mixed gas of argon and hydrogen as the working gas, and optionally hydrogen as the 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 the working gas and nitrogen as the reaction gas, and using a silicon target to coat the surface of the first film layer by ion beam sputtering to obtain the second film layer; alternately depositing the first film layer and the second film layer to obtain the first stacked film.

[0008] In some illustrative embodiments, a radio frequency bias is used to apply a bias to the substrate when alternately depositing the first film layer and the second film layer.

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

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

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

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

[0013] In some illustrative embodiments, taking an alternating layer composed of a layer of amorphous silicon or hydrogenated amorphous silicon and a layer of silicon nitride as one period, the number of stacking periods of the first stacked film is 7; taking an alternating layer composed of a layer of tantalum oxide and a layer of silicon oxide as one period, the number of stacking periods of the second stacked film is 10.5.

[0014] According to an embodiment of another aspect of the present invention, there is provided an ion beam sputtering coating apparatus for implementing the method as described above. The ion beam sputtering coating apparatus includes: a sample introduction chamber adapted to transfer a substrate; a main chamber communicating with the sample introduction chamber, and the main chamber includes: a workpiece disk located at the central position of the top of the main chamber and adapted to fix the substrate; a target fixed on a target rotating shaft on the side wall of the main chamber; a sputtering ion source located on the side of the main chamber opposite to the target and adapted to sputter target particles from the target by ion beam sputtering to coat the substrate; a microwave ion source located inside the main chamber and on the opposite side of the workpiece disk, and the microwave ion source is adapted to bombard the surface of the substrate during the coating process when alternately depositing the film layer structure.

[0015] In some illustrative embodiments, the ion beam sputtering coating apparatus further includes: an atomic hydrogen source located at the side wall inside the main chamber, and the atomic hydrogen source is adapted to provide hydrogen atoms to clean the surface of the substrate.

[0016] According to an embodiment of the present invention, by first preparing the first stacked film by ion beam sputtering and then preparing the second stacked film by ion beam sputtering on the first stacked film, it helps to reduce the probability of thermal distortion. Since the materials of the respective film layers in the first stacked film and the second stacked film are different, it is possible to reduce the thermal vibration inside the stacked materials, thereby ensuring better measurement accuracy, and further reducing the influence of the film on the beam quality when the film is subsequently applied to a high-reflection film; and different stacked materials can be balanced to make the film have a high reflectivity, which helps the subsequent application as an ultra-high reflectivity dielectric film. In addition, since the first stacked film and the second stacked film use different materials, by introducing in-situ annealing, the processes of sampling, transfer annealing, and reloading between the first stacked film and the second stacked film are avoided, which can reduce the contamination of the film caused by human operation and exposure to the atmosphere, and can effectively improve the yield of the film. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Through the following description of the embodiments of the present invention with reference to the accompanying drawings, the above and other objects, features, and advantages of the present invention will become clearer. In the drawings:

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

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

[0020] Figure 3 The curve 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 the wavelength is shown;

[0021] Figure 4 The ion mass spectrum of the stacked film of amorphous silicon and silicon oxide in Example 3 of the present invention is shown.

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

[0023] 1 - Sampling chamber;

[0024] 101 - Transfer robotic arm;

[0025] 102 - Sampling chamber vent hole;

[0026] 2 - Main chamber;

[0027] 3 - Workpiece disk;

[0028] 4 - Target;

[0029] 5 - Sputtering ion source;

[0030] 501 - Sputtering ion source vent hole;

[0031] 6 - Microwave ion source;

[0032] 601 - Microwave ion source vent hole;

[0033] 7 - Atomic hydrogen source;

[0034] 8 - Power supply and control unit;

[0035] 9 - Sampling chamber vacuum pump group;

[0036] 10 - Main chamber vacuum pump group;

[0037] 11 - Light control unit;

[0038] 12 - Target rotating shaft. Detailed implementation manners

[0039] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present invention. In the following detailed description, for the sake of explanation, numerous specific details are set forth to provide a comprehensive understanding of the embodiments of the present invention. However, obviously, one or more embodiments can also be implemented without these specific details. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present invention.

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

[0041] During the process of film coating using ion beam sputtering, by superimposing the use of a sputtering ion source and an auxiliary ion source, the preparation of higher-quality thin films is achieved. 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 thin 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] During the process of preparing thin films for subsequent applications, it is found that, for example, in the field of gravitational wave detection, the absorption of light by the thin film and the conversion into heat will cause thermal distortion of the mirror surface (which can be understood as thermal expansion or other forms of deformation that may occur on the mirror surface or other optical surfaces where the thin film is located), affecting the beam quality. This leads to relatively strict requirements for the absorption loss of the thin film. In addition, internal thermal fluctuations in the material, which can be understood as random motion and position changes of particles caused by thermal energy, will also affect the measurement accuracy in the form of Brownian thermal noise due to the resulting cavity length change. Among them, the cavity length change can be understood as the distance between two opposite mirrors in an optical resonator (a device composed of two opposite mirrors), so relatively high requirements are also imposed on the mechanical loss angle of the material. Similar requirements also exist in the ultra-stable cavity of an optical atomic clock, especially the material loss angle is one of the main factors currently limiting the stability of the atomic clock. At present, due to the poor low-temperature loss angle characteristics or the presence of thermal noise (thermal vibration) of the oxide dielectric high-reflection film prepared by ion beam sputtering, it is difficult to meet the current requirements for low-noise and high-reflectivity coatings.

[0043] In the process of implementing the inventive concept, it is found that by introducing a first stacked film and a second stacked film with different film layer 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 beneficial to expanding the subsequent application space. Moreover, due to the in-situ annealing of the first stacked film and the second stacked film, the contamination brought about during the sampling, transfer, and loading processes in 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 The flowchart of the method for preparing a thin film by ion beam sputtering according to an embodiment of the present invention is shown, as Figure 1 shown, including operations S101 to S104.

[0045] In operation S101, a first 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 the first stacked film after in-situ annealing.

[0047] In operation S103, a second coating process 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 the embodiment of the present invention, the materials of the respective film layers 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, and thus better measurement accuracy can be obtained. At the same time, the thin film has a high reflectivity, which helps to be used as an ultra-high reflectivity dielectric thin film subsequently. Based on the different materials of the respective film layers 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 processes of sampling, transfer annealing (which can be understood as being contaminated during the process of transferring the thin film to the annealing equipment), and reloading between the first stacked film and the second stacked film are avoided, and the contamination of the thin film caused by manual operation and exposure to the atmosphere is reduced, which helps to improve the yield of the thin film.

[0050] It should be noted that for the coating of different stacked thin 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, then return to the main chamber to complete the coating of the second stacked film, and then perform a second in-situ annealing.

[0051] According to an embodiment of the present invention, when alternately depositing the first film layer and the second film layer, a microwave ion source is used to bombard the surface of the substrate or a radio frequency bias is applied to the substrate. When forming the first stacked film, by bombarding the surface of the substrate with the microwave ion source, the mobility of sputtered silicon or silicon nitride on the surface of the substrate is improved, thereby reducing the roughness of the surface of the first stacked film and enhancing the flatness of the surface of the formed first stacked film, thus suppressing the loss caused by 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 film coating process, which helps to reduce the optical loss of the film layer. By means of the radio frequency bias, the surface of the substrate or the surface of the already deposited film layer can be cleaned 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 underlying film and reducing the absorption loss. The first stacked film, as the base layer, can reduce thermal noise or has good low-temperature loss angle. When alternately depositing the third film layer and the fourth film layer, the surface of the first stacked film is bombarded with a microwave ion source. Similarly to the foregoing, the microwave ion source promotes the atomic rearrangement in the thin film, which further helps to form a dense and flat film layer structure, increases the bonding strength between the newly deposited film layer and the underlying film, and further reduces the absorption loss.

[0052] In some embodiments, 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. During the process of conducting pre-experiments related to 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 the base layer to reduce thermal noise, so that the thin film has a good low-temperature loss angle; the second stacked film is used as the high-reflection film part, so that the thin film has both high reflectivity. When the thin film meets the high reflectivity requirement, it reduces thermal vibration, thereby improving the precision of precise measurement, and can be subsequently applied to technical fields with high precision requirements such as the field of 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 applied to the substrate. When bombarding the surface of the substrate with the microwave ion source, it is found that some thin film materials will be deposited on the grid of the microwave ion source. Since the ion beam sputtered thin film has high stress, during the long-term film coating process, the thin film on the surface of the microwave ion source grid will accumulate a large amount of stress and may disintegrate. The generated particles will reach and partially adsorb on the film layer structure along with the ion beam, and then be covered by subsequent film coating, forming pollution that is difficult to remove, resulting in an increase in the scattering loss of the thin film. With such a setting, since the radio frequency bias accelerates ions based on the bias of the substrate and does not require additional structures such as grids, it can effectively reduce particle contamination.

[0054] In addition, when preparing the first film layer, the substrate surface is bombarded with a microwave ion source. In order to separate the plasma from the radio frequency coil, structures such as quartz cups are used. However, under the bombardment of high-density plasma, the quartz cup will evaporate or sputter out oxygen elements, which will introduce oxygen contamination during the preparation process of the low thermal noise optical thin film material of the first film layer (amorphous silicon or hydrogenated amorphous silicon), resulting in a decrease in the refractive index of the obtained thin film and poor low-temperature thermal noise performance. Using a radio frequency bias does not involve structures such as quartz cups, which helps to avoid introducing 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, introducing a 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 thin film, reducing the impurity content, and helping to reduce the scattering loss and absorption loss of the thin film.

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

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

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

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

[0060] According to an embodiment of the present invention, in sub-operation S1011, when hydrogen is used as the reaction gas, hydrogenated amorphous silicon is prepared; when hydrogen is not used as the reaction gas, amorphous silicon is prepared. When hydrogenated amorphous silicon or amorphous silicon is subsequently applied in fields where thermal noise may exist, it can improve the resistance of the thin film to thermal noise and reduce the impact of thermal noise on the thin 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 resonators, it can reduce the impact of thermal noise on the thin film. In sub-operation S1013, by using silicon nitride in combination with amorphous silicon or hydrogenated amorphous silicon, the thermal noise is further reduced, and properties such as the low-temperature loss angle are strengthened.

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

[0062] It should be noted that during the process of preparing the film, it is found that if only the first stacked film is prepared, although the film has good resistance to thermal noise and is beneficial to strengthening the low-temperature loss angle of the film, due to the large light absorption of the above materials, the reflectivity of the film is low, and it is difficult to be used as a high-reflection film for subsequent applications.

[0063] In some embodiments, during the process of preparing the first film layer, the flow rate of the mixed gas is 10 - 100 sccm, for example, it can be 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 the ion beam sputtering is 200 - 600 W, for example, it can be 200 W, 300 W, 400 W, 500 W or 600 W, preferably 400 W. The acceleration voltage is 200 - 1000 V, for example, it can be 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 through radio frequency bias, and the power of the radio frequency bias is 50 - 200 W, for example, it can be 50 W, 100 W, 150 W or 200 W.

[0064] In some embodiments, during the process of preparing the second film layer, the flow rate of argon is 10 - 100 sccm, for example, it can be 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, it can be 200 W, 300 W, 400 W, 500 W or 600 W, preferably 400 W, and the acceleration voltage is 200 - 1000 V, for example, it can be 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 through radio frequency bias, and the power of the radio frequency bias is 50 - 200 W, for example, it can be 50 W, 100 W, 150 W or 200 W.

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

[0066] In sub-operation S1031, using argon as the working gas and oxygen as the reaction gas, 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, using argon as the working gas and oxygen as the reaction gas, 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, using argon as the working gas, in the state of ion beam sputtering, the deposited thin film can be etched, thereby optimizing the absorption loss and surface roughness of the thin film. Using oxygen as the reaction gas helps to form a tantalum oxide thin film, and the tantalum oxide thin film provides good reflectivity to light, which is beneficial to the subsequent preparation of a high-reflection film. In sub-operation S1032, the prepared silicon oxide helps to further improve the reflection effect of the thin film. In sub-operation S1033, by using tantalum oxide and silicon oxide in cooperation, the reflectivity is further improved to meet the higher requirements for reflectivity in technical fields such as optical resonators.

[0070] In some embodiments, during the preparation of the third film layer, the argon flow rate is 10~100 sccm, for example, it can be 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, it can be 200 W, 300 W, 400 W, 500 W or 600 W, preferably 500 W. The acceleration voltage is 200~1000 V, for example, it can be 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 introduced into the microwave ion source is 10~50 sccm, for example, it can be 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, it can be 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 10-100 sccm, for example, it can be 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, it can be 200 W, 300 W, 400 W, 500 W or 600 W, preferably 400 W, and the acceleration voltage is 200-1000 V, for example, it can be 200 V, 300 V, 400 V, 500 V, 600 V, 700 V, 800 V, 900 V or 1000 V, preferably 800 V. The flow rate of oxygen introduced into the microwave ion source is 10-50 sccm, for example, it can be 10 sccm, 20 sccm, 30 sccm, 40 sccm or 50 sccm, preferably 25 sccm. The power of bombardment 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, it can be 20 V, 50 V, 100 V, 200 V, 300 V or 400 V, preferably 150 V.

[0072] It should be noted that in this embodiment, by using the distributed Bragg reflector structure and based on the alternating stack structure formed by the third film layer and the fourth film layer (high refractive index oxide, low refractive index oxide), the scattering loss can be effectively reduced, so that the prepared thin film has a high reflectivity.

[0073] In some embodiments, before operation S101, it 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 substrate surface to form water and be pumped away by the pump. The substrate includes crystalline silicon. When crystalline silicon is stored in an atmospheric environment, a thin oxide layer will form on its surface, which will cause an increase in the surface roughness of the substrate and surface adsorption contamination, thereby further affecting the optical properties of the deposited thin film and resulting in poor adhesion at some positions of the thin film. By introducing atomic hydrogen cleaning, the oxide layer can be removed in a gentle manner before film coating.

[0074] Preferably, in atomic hydrogen cleaning, the flow rate of hydrogen gas is 0.1 - 5 sccm, for example, it can be 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, it can be 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, it can be 150 °C, 200 °C, 250 °C or 300 °C, and the cleaning time is 3 - 10 min, for example, it can be 3 min, 5 min, 7 min, 9 min or 10 min. Through atomic hydrogen cleaning, it 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, it can be 300 °C, 400 °C or 500 °C, preferably 400 °C. The annealing time is 1 - 12 h, for example, it can be 1 h, 4 h, 8 h or 12 h, preferably 1 h. The first in-situ annealing can be carried out, for example, by transferring the first stacked film from the main chamber to the sampling chamber through a transfer robotic arm for in-situ annealing. After the first stacked film is annealed and cooled to room temperature, it is then transferred back to the main chamber through the transfer robotic arm for the preparation of the second stacked film.

[0076] In some embodiments, the annealing temperature of the second in-situ annealing is 250 - 350 °C, for example, it can be 250 °C, 300 °C or 350 °C, preferably 300 °C. The annealing time is 9 - 11 h, for example, it can be 9 h, 10 h or 11 h, preferably 10 h. 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 carried out. Since the annealing temperature of the second in-situ annealing is lower than that of the first in-situ annealing, it can reduce the damage to the first stacked film while forming the second stacked film, enabling the prepared thin film to have better reflectivity while reducing thermal vibration and further improving the precision of thin film precision measurement.

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

[0078] In some embodiments, taking an alternating layer composed of one layer of amorphous silicon or hydrogenated amorphous silicon and one layer of silicon nitride as one cycle, the stacking cycle number of the first stacked film is 7; taking an alternating layer composed of one layer of tantalum oxide and one layer of silicon oxide as one cycle, the stacking cycle number of the second stacked film is 10.5. During the pre-experiment related to the present invention, it was found that when the stacking cycle numbers are the above values, the prepared thin film is relatively flatter, has a higher reflectivity, and has a better resistance effect on thermal vibration.

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

[0080] The sample introduction chamber 1 is suitable for transporting and receiving substrates. For example, the substrate can be placed through the sample introduction chamber 1, or the substrate can be transported back to the sample introduction chamber 1 for the first in-situ annealing after the first stacked film is prepared, or the substrate can be transported back to the sample introduction chamber 1 for the second in-situ annealing after the second stacked film is prepared, so as to avoid the contact of the film with the atmospheric environment and reduce the pollution on the film surface. The main chamber 2 is made of stainless steel and is connected to the sample introduction chamber 1 to facilitate the mutual transfer of the substrate between the two. The main chamber 2 includes components such as a workpiece disk 3, a radio frequency power supply (not shown in the figure), a target 4, a sputtering ion source 5, and a microwave ion source 6. The main chamber can be connected to each component by a flange as needed. The workpiece disk 3 is located at the central position of the top of the main chamber 2 and is suitable for fixing the substrate. The workpiece disk 3 has a workpiece disk handle (not shown in the figure) and can be compatible with workpiece disks 3 larger than 12 inches. During the coating process, the workpiece disk 3 can be heated, and the temperature can be regulated in the range from room temperature to 300 °C, and the temperature control accuracy is better than ±0.1 °C. In addition, it can drive the workpiece disk 3 to rotate to improve the coating uniformity, and the maximum rotation speed can reach 1000 rpm. The radio frequency power supply is electrically connected to the workpiece disk 3 and is suitable for providing a radio frequency bias voltage to the substrate when alternately depositing the film layer structure. The workpiece disk 3 is electrically connected to the radio frequency power supply, so that a radio frequency bias voltage is applied to the substrate during the coating process to generate plasma, which can be used for substrate cleaning and auxiliary coating, and can achieve an effect similar to that of the microwave ion source 6, while avoiding particle contamination and material contamination generated by the ion source.

[0081] The target 4 is fixed on the target shaft 12 on the side wall of the main chamber 2. The target shaft 12 can be a polyhedral structure, and different materials of the target 4 can be fixed respectively as needed, so that when different targets need to be used, they can be directly used by rotating through the rotation of the target shaft 12, avoiding the complex operations brought by repeated replacement. The target shaft 12 can be, for example, Figure 2 the tetrahedral structure shown in Figure 2As shown, the target 4 is located on the right side inside the main chamber 2, and the sputtering ion source 5 is located on the left side inside the main chamber 2; alternatively, the target 4 can be located on the left side inside the main chamber 2, and the sputtering ion source 5 is located on the right side inside the main chamber 2. The sputtering ion source 5 provides the main ion source and is suitable for sputtering target particles from the target 4 by means of ion beam sputtering to coat the substrate. The diameter of the sputtering ion source 5 ≥ 16 cm, and the maximum power can reach 600 W; the microwave ion source 6 is located inside 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, and the microwave ion source 6 is located on the opposite side of the workpiece disk 3. For example, it can be as Figure 2 shown, at the central position of the bottom inside the main chamber 2, and is suitable for bombarding the substrate surface during the alternate deposition of 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 thin film surface, and suppressing the loss of surface scattering of the thin film.

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

[0083] To avoid the need to frequently disrupt the vacuum atmosphere during manual lofting, which may also affect the cleanliness of the equipment, the loading chamber 1 is further provided with a transfer robotic arm 101 and a loading chamber vent hole 102. The transfer robotic arm 101 is suitable for transferring substrates, and the loading chamber vent hole 102 is suitable for removing the vacuum state of the loading chamber 1. The loading chamber vacuum pump group 9 is connected to the loading chamber 1 and is suitable for evacuating the loading chamber 1. During normal use, the substrate is first fixed to the workpiece plate 3 and then placed into the loading chamber 1. After the loading chamber vacuum pump group 9 initially evacuates, the workpiece plate 3 together with the substrate can be sent to the main chamber 2 through the transfer robotic arm 101. The loading 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 loading chamber vacuum pump group 9 includes a dry pump and a molecular pump, enabling the vacuum degree of the loading chamber 1 to reach below 5E-6 Torr.

[0084] In some embodiments, the ion beam sputtering coating device further includes a main chamber vacuum pump group 10, which includes a dry pump, a molecular pump, and a cryopump, capable of achieving a vacuum degree of below 2E-8 Torr in the main chamber 2. 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 Torr. The sputtering ion source 5 also has a sputtering ion source vent hole 501, 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 hole 601, 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, suitable for providing electrical energy to each component and separately regulating each component to achieve control of water, electricity, and gas in the ion beam sputtering coating device, as well as setting and recording the coating process. The main chamber 2 also includes an optical control unit 11 for detecting the coating thickness through the optical control unit 11. When the film thickness reaches the set value (in the case of a wavelength of 1397 nm, the film thickness is equal to , where n is the refractive index of the film layer calibrated by an ellipsometer at 1397 nm), the sputtering ion source 5 and the microwave ion source 6 are stopped to complete the preparation process of the film layer. The optical control unit 11 monitors the film thickness through spectroscopy, thereby assisting the ion beam sputtering coating device to accurately coat according to the designed film structure.

[0086] It should be noted that Figure 2 is mainly used to illustrate the relative positional relationship between each component. For example, the workpiece plate 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 apparatus further includes an atomic hydrogen source 7 located at the side wall within the main chamber 2. The atomic hydrogen source 7 is adapted to convert the introduced hydrogen gas into hydrogen atoms to clean the substrate surface (by combining with oxygen on the substrate surface), remove the native oxide layer on the substrate surface, and form water which is pumped away by the pump.

[0088] According to an embodiment of the present invention, the ion beam sputtering coating apparatus of the present invention can achieve ultra-high vacuum, pre-cleaning of the target and the substrate before coating, has highly adjustable ion beam parameters, can minimize material contamination during the coating process as much as possible, and can more precisely optimize the coating process parameters, so as to be able to achieve a low-noise high-reflectivity mirror coating with atomic-level flatness and ultra-low absorption loss.

[0089] Furthermore, the ion beam sputtering coating apparatus of the present invention can achieve functions such as ultra-high base vacuum (the base represents the non-operating state, that is, the ultra-high vacuum state that the equipment can reach before coating), pre-cleaning of the target and the substrate, real-time monitoring of the coating rate, microwave ion source-assisted deposition, in-situ annealing, etc., thereby reducing the absorption loss of the high-reflectivity thin film and being applicable to the coating of low-noise materials such as amorphous silicon and silicon nitride.

[0090] Hereinafter, taking the coating of a high-reflection film of an amorphous silicon, silicon nitride, tantalum oxide, and silicon oxide mixed system with a central wavelength of 1397 nm as an example, a detailed description will be given.

[0091] Sample introduction: The ultra-precision polished silicon substrate is cleaned by a cleaning machine, dried, clamped on the workpiece tray, and placed in the sample introduction chamber; the sample introduction chamber is evacuated to a vacuum degree less than 1E-4 Torr. At this time, the baffle valve between the sample introduction chamber and the main chamber is opened, and the workpiece tray is sent to the tray in the main chamber by the robotic arm. The baffle valve is closed, and the main chamber is evacuated to a vacuum degree less than 2E-8 Torr.

[0092] Substrate pre-cleaning: Use the atomic hydrogen source to perform hydrogen atom cleaning on the substrate. The hydrogen gas flow rate can be selected from 0 to 5 sccm, preferably 1 sccm; the power of the atomic hydrogen source 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 min. It mainly serves to remove residual contaminants on the substrate surface and optimize the surface roughness of the substrate.

[0093] Amorphous silicon coating: Rotate the target shaft to rotate the silicon target (the first silicon target) to a position suitable for sputtering. Start the sputtering ion source, ionize and accelerate argon gas to perform target atom sputtering. At this time, synchronously start the microwave ion source, use the argon-hydrogen mixed gas as the gas source of the microwave ion source, and hydrogenate and etch the deposited film to optimize 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 apply a bias voltage to the workpiece disk through a radio frequency bias, which can be selected from 50 to 200 W, preferably 100 W. Use an optical control module to monitor the film thickness. When the film thickness reaches the set value (the film thickness is equal to , , which is the refractive index of the amorphous silicon thin film calibrated by an ellipsometer at 1397 nm), stop the sputtering ion source and the microwave ion source, and evacuate to 2E-8 Torr.

[0094] Silicon nitride coating: Rotate the target shaft to rotate the silicon target (the second silicon target) to a position suitable for sputtering. Start the sputtering ion source, ionize and accelerate argon gas to perform target atom sputtering. At this time, synchronously start the microwave ion source, use nitrogen gas as the gas source of the ion source, and nitride and etch the deposited film to optimize the absorption loss and surface roughness of the film; the flow rate of argon gas introduced into 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 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 apply a bias voltage to the workpiece disk through a radio frequency bias, which can be selected from 50 to 200 W, preferably 100 W. Use an optical control module to monitor the film thickness. When the film thickness reaches the set value (the film thickness is equal to , , which is the refractive index of the silicon nitride thin film calibrated by an ellipsometer at 1397 nm), stop the sputtering ion source and the microwave ion source, and evacuate to 2E-8 Torr.

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

[0096] First in-situ annealing: After the coating is completed, open the baffle valve between the sample introduction chamber and the main chamber, take out the workpiece disk to the sample introduction chamber through the robotic arm, close the baffle valve, and perform in-situ annealing in the sample introduction chamber. The annealing temperature is 400 °C and the time is 1 h. 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 to position the tantalum target for sputtering. Start the sputtering ion source, ionize and accelerate argon gas to sputter target atoms. At the same time, start the microwave ion source, use a mixture of argon and hydrogen as the ion source gas, oxidize and etch the deposited film to optimize the absorption loss and surface roughness of the film. The flow rate of argon gas introduced into 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 flow rate of oxygen gas introduced into 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 optical 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 calibrated by the ellipsometer at 1397 nm), stop the sputtering ion source and the microwave ion source, and evacuate to 2E-8 Torr.

[0098] Silicon Oxide Coating: Rotate the target shaft to position the silicon target (the third silicon target) for sputtering. Start the sputtering ion source, ionize and accelerate argon gas to sputter target atoms. At the same time, start the microwave ion source, use nitrogen as the ion source gas, oxidize and etch the deposited film to optimize the absorption loss and surface roughness of the film. The flow rate of argon gas introduced into 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 400 W, and the acceleration voltage can be selected from 200 to 1000 V, preferably 800 V. The flow rate of oxygen gas introduced into the microwave ion source can be selected from 10 to 50 sccm, preferably 25 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 150 V. Use the optical 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 silicon oxide film calibrated by the ellipsometer at 1397 nm), stop the sputtering ion source and the microwave ion source, and evacuate to 2E-8 Torr.

[0099] Preparation of the Second Stacked Film: Taking the 1397 nm high-reflection mirror coating as an example, the steps of preparing tantalum oxide coating and silicon oxide coating can be alternately carried out, a total of 10.5 pairs.

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

[0101] Based on this, in the process of depositing a low thermal noise film layer in an ion beam sputtering coating device, the present invention introduces a substrate radio frequency bias voltage, which can replace the auxiliary ion source during the coating process of the low thermal noise film layer, avoid particle contamination and impurity element doping generated during the operation of the auxiliary ion source, improve the cleanliness of the thin film, reduce the impurity content, and help reduce the scattering loss and absorption loss of the thin film.

[0102] In addition, introducing an in-situ annealing function in the ion beam sputtering coating device can avoid contamination during the transfer of the thin film to the annealing equipment, especially suitable for 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 carried out after the bottom film system coating is completed, then return to the main chamber to complete the top film system coating, and then the second annealing is carried out.

[0103] The present invention introduces an atomic hydrogen source in the ion beam sputtering coating device to treat the silicon substrate before coating. Without damaging the surface roughness of the substrate, the native oxide layer on the substrate surface is removed, which helps reduce the optical loss of the mirror surface. The present invention uses a microwave ion source as an auxiliary source, which has 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 surface.

[0104] The present invention tests the effects of using an auxiliary ion source and a substrate radio frequency bias voltage on the thin film based on different examples. Among them, Example 1 is an amorphous silicon thin film prepared using a radio frequency bias voltage on an ion beam sputtering coating device, and Example 2 is an amorphous silicon thin film prepared using an auxiliary ion source under the same parameter conditions as Example 1. The refractive indices of the amorphous silicon thin films in Example 1 and Example 2 are detected. Figure 3 Shows the refractive index change curve of the amorphous silicon thin films prepared in Example 1 and Example 2 of the present invention with respect to wavelength. As Figure 3 shown, it can be seen that using an auxiliary ion source ( Figure 3 the ion source in Figure 3There are significant differences in the refractive indices of amorphous silicon thin films prepared by (substrate bias in it). The refractive index of the amorphous silicon thin film prepared by the auxiliary ion source method is significantly lower than that of the substrate bias method. When using the amorphous silicon thin film obtained by the auxiliary ion source method to prepare a high-reflection film, since the refractive index difference between the amorphous silicon layer and silicon oxide (or other low-refractive-index materials) decreases, more film layer pairs are required to achieve the same refractive index as the substrate bias method, and the increase in film thickness will correspondingly increase the thermal noise of the thin film, limiting the sensitivity of the corresponding precision measurement device.

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

[0106] To further understand the reason for the decrease in the refractive index of the amorphous silicon thin film prepared by the auxiliary ion source method, tests were carried out. Among them, Example 3 was to first deposit about 100 nm of amorphous silicon thin film on a silicon substrate, and then deposit about 100 nm of silicon oxide thin film. Secondary ion mass spectrometry was used to characterize the elements in the thin film of Example 3. Figure 4 The ion mass spectrometry diagram of the stacked film of amorphous silicon and silicon oxide in Example 3 of the present invention is shown. As Figure 4 shown, there is still a significantly higher oxygen element signal in the amorphous silicon thin film (the a-Si film layer in the figure) than the substrate, indicating that doping oxygen in the thin film will occur during the deposition of the amorphous silicon thin film by the auxiliary ion source, resulting in a decrease in the refractive index. According to the analysis of the ion source structure, the main source of oxygen elements is the quartz cup in the ion source. When the ion source works, higher-energy ions will bombard the quartz cup, sputtering out oxygen elements from it, resulting in oxygen contamination in the amorphous silicon thin film.

[0107] During the process of carrying out relevant example experiments, it was found that as the temperature decreases, the loss angle of the silicon oxide film layer 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 a temperature of 10 K (-263 °C) is as high as 8E-4, which will have an adverse effect on the thermal noise of the thin film at low temperatures. Theoretical speculation is that oxygen contamination in amorphous silicon will also have a similar effect, deteriorating the low-temperature loss angle of amorphous silicon. Therefore, components such as radio frequency bias and atomic hydrogen source are integrated in the ion beam sputtering coating device to reduce oxygen contamination during the deposition of amorphous silicon thin films and improve the low-temperature noise performance of the thin films.

[0108] The specific embodiments described above have further detailed the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included within the protection scope 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 the first film layer and the second film layer are alternately deposited, a radio frequency bias is used to apply a bias voltage to the substrate; 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; the materials of each film layer in the first stacked film and the second stacked film are different; The first film layer is amorphous silicon or hydrogenated amorphous silicon, and the second film layer is silicon nitride; Before preparing the first stacked film, the method further includes: performing atomic hydrogen cleaning on the substrate; the substrate is crystalline silicon.

2. The method according to claim 1, characterized in that: The third film layer is tantalum oxide, and the fourth film layer is silicon oxide.

3. The method according to claim 1, 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: 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.

5. 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.

6. 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.

7. An ion beam sputtering coating device, used to implement the method according to any one of claims 1 to 6, 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.

8. The ion beam sputtering coating device according to claim 7, 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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