Metal fluoride film and low-temperature ALD preparation method and application thereof

Abstract

The invention provides a method for preparing a metal fluoride film through low-temperature ALD, and the method comprises the steps: carrying out the plasma enhanced atomic layer deposition reaction of a metal precursor and oxygen plasma, and obtaining the metal fluoride film; the metal precursor is selected from hexafluoroacetylacetonate. According to the method, PEALD is utilized to prepare the metal fluoride film, fluorine-containing gas with extremely high corrosivity is not adopted, and the safety of film deposition is improved; and the preparation process is relatively low in temperature, environment-friendly, controllable in film thickness and easy to implement. The prepared metal fluoride film has the advantages of uniform film layer, compact surface and extremely low refractive index, can be uniformly deposited when being applied to an optical lens, and has shape retention. In addition, some high-refractive-index film layer structures can be matched to realize anti-reflection or anti-reflection performance in some specific spectral regions.

Description

Technical Field

[0001] The present invention belongs to the technical field of thin film preparation, and in particular relates to a metal fluoride thin film and a low-temperature ALD preparation method and application thereof. Background Art

[0002] Conventional methods for preparing magnesium fluoride thin films mainly include vacuum evaporation, sputtering deposition, and atomic layer deposition. Thin films deposited by vacuum evaporation and sputtering deposition methods cannot effectively guarantee the uniformity of the coating, while the atomic layer deposition method can ensure the uniformity of the coating. However, the deposition temperature of magnesium fluoride thin films prepared by Thermal ALD is relatively high and a fluorine source such as fluorine or hydrogen fluoride must be used. Most of these fluorine sources are extremely corrosive and are not suitable for thin film deposition of some products, such as optical lenses.

[0003] Therefore, how to prepare metal fluoride films without using highly corrosive fluorine sources and make them suitable for low-temperature deposition has become a problem that needs to be solved. Summary of the invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a method for preparing metal fluoride films by low-temperature ALD. The preparation method provided by the present invention does not use a highly corrosive fluorine source and is suitable for low-temperature deposition occasions.

[0005] The present invention provides a method for preparing a metal fluoride film by low-temperature ALD, wherein a metal precursor is subjected to plasma enhanced atomic layer deposition reaction with oxygen plasma to obtain a metal fluoride film;

[0006] The metal precursor is selected from hexafluoroacetylacetonate.

[0007] Preferably, the method comprises the following steps:

[0008] A) placing the coating sample in a reaction chamber device, introducing a metal precursor for a period of time, then introducing a protective atmosphere for purging, then introducing an oxygen source, turning on the radio frequency for plasma enhanced atomic layer deposition reaction, and then introducing a protective atmosphere for purging after the reaction to complete a sub-cycle deposition;

[0009] B) Repeat step A) to obtain a metal fluoride film.

[0010] Preferably, the metal precursor is selected from at least one of magnesium hexafluoroacetylacetonate, lithium hexafluoroacetylacetonate, aluminum hexafluoroacetylacetonate, chromium hexafluoroacetylacetonate or hafnium hexafluoroacetylacetonate.

[0011] Preferably, the temperature of the reaction chamber device is 10-400° C., and the pressure is 0.2-10 mbar.

[0012] Preferably, in the step A), the metal precursor enters the reaction chamber via a carrier gas;

[0013] The flow rate of the metal precursor is 100-500 sccm, the time of passing the metal precursor is 0.5-120 s, the heating temperature of the source bottle of the metal precursor is 80-150° C., and the heating temperature of the pipeline of the metal precursor is 90-200° C.;

[0014] The carrier gas is selected from an inert gas, and the flow rate of the inert gas is 500-3000 sccm.

[0015] Preferably, in step A), the protective atmosphere is selected from nitrogen or argon, and the purging time is 5 to 120 seconds.

[0016] Preferably, the flow rate of the oxygen source is 500 to 1500 sccm, and the introduction time is 0.5 to 120 s.

[0017] Preferably, the radio frequency power is 100W to 10000W.

[0018] Preferably, before step A), a preheating process is further included, wherein the preheating temperature is 50-400° C., the preheating pressure is 0.2-10 mbar, and the preheating time is 500-2000 s.

[0019] The present invention also provides a metal fluoride film prepared by the method.

[0020] The present invention also provides an anti-reflection film, comprising the above-mentioned metal fluoride film.

[0021] The present invention also provides an anti-reflection film, comprising the above-mentioned metal fluoride film.

[0022] The present invention also provides an application of the metal fluoride film in the optical field.

[0023] Compared with the prior art, the present invention provides a method for preparing metal fluoride thin films by low-temperature ALD, wherein a metal precursor is subjected to plasma enhanced atomic layer deposition reaction with oxygen plasma to obtain a metal fluoride thin film; the metal precursor is selected from hexafluoroacetylacetonate. The present invention utilizes PEALD to prepare metal fluoride thin films, and does not use highly corrosive fluorine-containing gases, thereby improving the safety of thin film deposition; and the preparation process has a low temperature, is environmentally friendly, has controllable film thickness, and is easy to implement. The prepared metal fluoride thin film has a uniform film layer, a dense surface, and an extremely low refractive index. It can be applied to optical lenses, can be deposited uniformly, and has shape retention. In addition, it can also be combined with some high-refractive index film structures to achieve anti-reflection or anti-reflection properties in some specific spectral regions. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The XPS test results of the metal fluoride film prepared in Example 1;

[0025] Figure 2 The refractive index test results of the metal fluoride film prepared in Example 1. DETAILED DESCRIPTION

[0026] The present invention provides a method for preparing a metal fluoride film by low-temperature ALD, wherein a metal precursor is subjected to plasma enhanced atomic layer deposition reaction with oxygen plasma to obtain a metal fluoride film;

[0027] The metal precursor is selected from hexafluoroacetylacetonate, and preferably, the metal precursor is selected from at least one of magnesium hexafluoroacetylacetonate, lithium hexafluoroacetylacetonate, aluminum hexafluoroacetylacetonate, chromium hexafluoroacetylacetonate or hafnium hexafluoroacetylacetonate.

[0028] Specifically, the method for preparing a metal fluoride thin film by low-temperature ALD comprises the following steps:

[0029] A) placing the coating sample in a reaction chamber device, introducing a metal precursor for a period of time, then introducing a protective atmosphere for purging, then introducing an oxygen source gas, turning on the radio frequency for plasma enhanced atomic layer deposition reaction, and then introducing a protective atmosphere for purging after the reaction to complete a sub-cycle deposition;

[0030] B) Repeat step A) to obtain a metal fluoride film.

[0031] The present invention first places the coated sample in a reaction chamber device. The present invention has no special restrictions on the type of the coated sample, which can be selected as needed. The coated sample whose temperature tolerance meets the process temperature can be used as the coated sample of the method provided by the present invention, for example, it can be a silicon substrate, a wafer, an optical lens, PET, PVC, metal, and glass.

[0032] The present invention can be used for coating on a plane or non-plane surface, and can ensure that the film layer has good uniformity. The non-plane surface can be any uneven surface such as a spherical surface, a partial spherical surface, a concave surface, a groove, etc. Preferably, the present invention can be used for coating on a sample with a large radius of curvature, and the obtained film layer has good uniformity.

[0033] Before placing the coated sample in the reaction chamber device, the reaction chamber is preheated, the preheating temperature is 50-400°C, which can be 50, 70, 90, 100, 150, 200, 250, 300, 350, 400, or any value between 150 and 400°C, the preheating pressure is 0.2-10 mbar, which can be 0.2, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or any value between 0.2 and 10 mbar, and the preheating time is 500-2000s, which can be 500, 700, 1000, 1500, 2000, or any value between 500 and 2000s.

[0034] After the reaction chamber is preheated, the coated sample is placed in the reaction chamber device, and the temperature of the reaction chamber device is controlled to be 10-400°C during the reaction process, which can be 10, 20, 25, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 200, 250, 300, 350, 400, or any value between 10 and 400°C; preferably any value between 10 and 200°C. In the present invention, since oxygen plasma is used, the process temperature can be lowered compared to the case where plasma is not used, and the film layer can even be prepared at room temperature or below room temperature. In the present invention, the room temperature condition is defined as 25±5°C.

[0035] The pressure of the reaction chamber is 0.2 to 10 mbar, and can be 0.2, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or any value between 0.2 and 10 mbar.

[0036] Then, a metal precursor is introduced for a period of time, and the metal precursor enters the reaction chamber through the carrier gas. The flow rate of the metal precursor is 100 to 500 sccm, which can be 100, 150, 200, 250, 300, 350, 400, 450, 500, or any value between 100 and 500 sccm; the time for introducing the metal precursor is 0.5 to 120 seconds, which can be 0.5, 1, 5, 10, 30, 50, 70, 90, 100, 120, or any value between 0.5 and 120 seconds. The heating temperature of the source bottle of the metal precursor is 80-150°C, which can be 80, 90, 100, 110, 120, 130, 140, 150, or any value between 80 and 150°C; the heating temperature of the pipeline of the metal precursor is 90-200°C, which can be 90, 100, 120, 140, 150, 160, 180, 200, or any value between 90 and 200°C;

[0037] The carrier gas is selected from an inert gas, and the flow rate of the inert gas is 500-3000 sccm, and can be 500, 1000, 1500, 2000, 2500, 3000, or any value between 500 and 3000 sccm.

[0038] Then, a protective atmosphere is introduced for purging, wherein the protective atmosphere is selected from nitrogen or argon. The purging time is 5 to 120 seconds, and can be 0.5, 1, 5, 10, 30, 50, 70, 90, 100, 120, or any value between 5 and 120 seconds.

[0039] After the purge is completed, an oxygen source gas is introduced, and the radio frequency is turned on at the same time to perform a plasma enhanced atomic layer deposition reaction. The oxygen source is selected from a gas containing oxygen, preferably oxygen. The time for the oxygen source to be introduced is 0.5 to 120 seconds, which can be 0.5, 1, 5, 10, 30, 50, 70, 90, 100, 120, or any value between 0.5 and 120 seconds; the flow rate of the oxygen source is 500 to 1500 sccm, which can be 500, 700, 900, 1000, 1200, 1400, 1500, or any value between 500 and 1500 sccm. The power of the radio frequency is 100 W to 10000 W, and can be 100, 500, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, or any value between 100 W and 10000 W. During the plasma enhanced atomic layer deposition reaction, the oxygen source and its delivery pipeline do not need to be heated, thereby reducing the preparation cost.

[0040] The plasma enhanced atomic layer deposition reaction has a deposition rate of It can be 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or Any value in between.

[0041] After the deposition is completed, a protective atmosphere is introduced for purging to complete a sub-cycle of deposition. The protective atmosphere is selected from nitrogen or argon. The purging time is 5 to 120 seconds, and can be 0.5, 1, 5, 10, 30, 50, 70, 90, 100, 120, or any value between 5 and 120 seconds.

[0042] Then, the above steps are repeated until the metal fluoride film reaches a target thickness.

[0043] In the present invention, taking the coating sample as wafer, the precursor as magnesium hexafluoroacetylacetonate, and the oxygen source as oxygen as an example, the preparation mechanism of the magnesium fluoride film is specifically as follows:

[0044] The first step: magnesium hexafluoroacetylacetonate is brought into the reaction chamber of low-temperature ALD for preparing metal fluoride films by inert gas through a delivery pipeline, and adsorbed on the coating sample to form a surface containing hfac - The film layer;

[0045] After purging with inert gas, the excess and unreacted precursors are purged away;

[0046] Step 2: Introduce O2, turn on the radio frequency, and the oxygen forms oxygen plasma and interacts with the hfac in the film layer. - Reaction to form Mg-CO3 2- and some free F - , F - Further replacement of CO3 2- With Mg 2+ Combined to form MgF2, which is deposited on the substrate;

[0047] After purging with inert gas, the by-products after the reaction are purged to obtain a stable MgF2 film.

[0048] In some specific embodiments of the present invention, when the metal precursor is selected from magnesium hexafluoroacetylacetonate, the chemical reaction formula is as follows:

[0049] Mg(hfac)2+O2 plasma→MgF2.

[0050] Similarly, when the metal precursor is selected from lithium hexafluoroacetylacetonate, aluminum hexafluoroacetylacetonate, chromium hexafluoroacetylacetonate or hafnium hexafluoroacetylacetonate, the corresponding lithium fluoride film, aluminum fluoride film, chromium fluoride film or hafnium fluoride film is prepared according to the above mechanism.

[0051] The present invention adopts plasma enhanced atomic layer deposition technology (PEALD) to prepare metal fluoride thin films, and utilizes surface controlled gas phase precursor to deposit ultra-thin, uniform, pinhole-free dense layer of metal fluoride thin film, which can greatly reduce the reaction temperature and does not use additional fluorine sources such as fluorine element or hydrogen fluoride. Compared with vacuum evaporation and magnetron sputtering technology, this method has better and more controllable coating uniformity for samples with large curvature radius. Compared with Thermal ALD technology, it can ensure the uniformity of film preparation without using fluorine sources such as fluorine element or hydrogen fluoride and other corrosive materials, while greatly reducing the process temperature of the film preparation process.

[0052] The present invention also provides a metal fluoride film obtained by the above method, which can be a magnesium fluoride film, a lithium fluoride film, an aluminum fluoride film, a chromium fluoride film or a hafnium fluoride film.

[0053] The thickness of the metal fluoride film can be as low as less than 1 nm, and can evenly cover the surface of the coating sample.

[0054] The refractive index of the metal fluoride film is 1.32 to 1.40, preferably 1.32 to 1.35.

[0055] The metal fluoride thin film has a uniform film layer and a dense surface.

[0056] The present invention also provides an anti-reflection film, comprising the above-mentioned metal fluoride film. The anti-reflection film structure comprises: a lens or glass and alternately stacked low refractive index layers and high refractive index layers compounded on the surface of the lens or glass, wherein the high refractive index layer is made of a high refractive index material, the high refractive index material is selected from one or more of TiO2, Ta2O5, and Nb2O5, and the low refractive index layer is selected from the above-mentioned metal fluoride film, preferably the above-mentioned magnesium fluoride film.

[0057] The present invention also provides an anti-reflection film, comprising the metal fluoride film. The anti-reflection film comprises: a lens or glass and a low refractive index layer composited on the surface of the lens or glass, the low refractive index layer is selected from the metal fluoride film, preferably the magnesium fluoride film.

[0058] In order to further understand the present invention, the low-temperature ALD preparation of metal fluoride thin films and the method and application thereof provided by the present invention are described below in conjunction with embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0059] Example 1

[0060] The goal is to deposit MgF2 film on the wafer surface:

[0061] First, the wafer is sent into the reaction chamber, and the reaction chamber is vacuumed and preheated. The temperature of the reaction chamber is set to 150°C, and the vacuum pressure is adjusted at 1 mbar by a butterfly valve. After reaching the temperature and pressure, it is preheated for 1000 seconds. Then the atomic layer deposition process is carried out. Magnesium hexafluoroacetylacetonate is introduced into the chamber through a carrier gas. The carrier gas flow rate is set to 300 sccm, and the introduction time is 5 seconds. Then, an inert gas argon is introduced for purging. The purge time is 15 seconds. After the purge is completed, oxygen is introduced. The oxygen introduction time is 2 seconds and the flow rate is 1000 sccm. While introducing oxygen, the RF power supply is turned on and the RF power is set to 1000 W to complete the oxygen deposition process. Finally, an inert gas argon is introduced for purging. The purge time is 10 seconds to complete a sub-cycle of atomic layer deposition of magnesium fluoride film. The deposition rate of magnesium fluoride Repeat this cycle for 1000 cycles to obtain a film material with a target thickness of 5nm; the refractive index and XPS tests of the deposited material are then performed. Figure 1 and Figure 2 . Figure 1 The XPS test results of the metal fluoride film prepared in Example 1 are as follows: Figure 2 The refractive index test results of the metal fluoride film prepared in Example 1.

[0062] Depend on Figure 1 It can be seen that the MgF2 film prepared by the low-temperature PEALD method, XPS film characterization shows Mg:F=1:1.8, and the C impurity content in the film layer is less than 2%; thus, it can be seen that the prepared film is a MgF2 film with low impurity content and high purity.

[0063] Depend on Figure 2 It can be seen that the refractive index of the film prepared by ellipsometer testing is 1.337, which has an extremely low refractive index and meets the requirements of optical applications.

[0064] The uniformity of the film was tested and the ratio of the thickness deviation of the film to the average thickness of the film was calculated. The results are shown in Table 1.

[0065] The density of the film was tested and the results are shown in Table 1.

[0066] Example 2

[0067] On the basis of Example 1, the type of precursor was changed to lithium hexafluoroacetylacetonate.

[0068] Example 3

[0069] On the basis of Example 1, the type of precursor was changed to aluminum hexafluoroacetylacetonate.

[0070] Example 4

[0071] On the basis of Example 1, the type of precursor was changed to chromium hexafluoroacetylacetonate.

[0072] Example 5

[0073] On the basis of Example 1, the type of precursor was changed to hafnium hexafluoroacetylacetonate.

[0074] Example 6

[0075] On the basis of Example 1, the reaction chamber temperature was changed to 200°C, the pressure was 3 mbar, the metal precursor flow rate was 200 sccm, the introduction time was 10 s, and then the inert gas argon was introduced for 15 s to purge, and then oxygen was introduced for 2 s with a flow rate of 1000 sccm. At the same time, the radio frequency was turned on, the radio frequency power was set to 3000 W, and then the inert gas argon was introduced for 10 s to purge, and the deposition of a sub-cycle of magnesium fluoride film was completed. The deposition rate The cycle was repeated for 300 cycles to obtain a film material with a target thickness of 6 nm.

[0076] Example 7

[0077] On the basis of Example 1, the reaction chamber temperature was changed to 300°C, the pressure was 5 mbar, the metal precursor flow rate was 400 sccm, the introduction time was 5 s, and then the inert gas argon was introduced for 15 s to purge, and then oxygen was introduced for 2 s with a flow rate of 1000 sccm. At the same time, the radio frequency was turned on, the radio frequency power was set to 5000 W, and then the inert gas argon was introduced for 10 s to purge, and the deposition of a sub-cycle of magnesium fluoride film was completed. The deposition rate The cycle was repeated 133 times to obtain a film material with a target thickness of 4 nm.

[0078] Example 8

[0079] On the basis of Example 1, the reaction chamber temperature was changed to 400°C, the pressure was 8 mbar, the metal precursor flow rate was 500 sccm, the introduction time was 3 s, and then the inert gas argon was introduced for 15 s to purge, and then oxygen was introduced for 2 s with a flow rate of 1000 sccm. At the same time, the radio frequency was turned on, and the radio frequency power was set to 8000 W. Then, the inert gas argon was introduced for 10 s to purge, and the deposition of a sub-cycle of magnesium fluoride film was completed. The deposition rate The cycle was repeated for 50 cycles to obtain a film material with a target thickness of 4 nm.

[0080] Comparative Example 1

[0081] S100: transferring the substrate to an atomic layer deposition reaction chamber, where the substrate can be used as a deposition carrier for the magnesium fluoride film.

[0082] S200: introducing a magnesium source into the atomic layer deposition reaction chamber through a carrier gas, wherein the magnesium source is bisethylcyclopentadienyl magnesium, and the heating temperature of the bisethylcyclopentadienyl magnesium is 60-100° C.; and then introducing a protective gas for purging.

[0083] S300: introducing fluorine source hydrogen fluoride into the atomic layer deposition reaction chamber, the fluorine source is at room temperature, and then the atomic layer deposition reaction chamber is gas purged.

[0084] Among them, the preparation conditions of the atomic layer deposition reaction chamber are: the substrate is heated to 200°C, the temperature of the atomic layer deposition reaction chamber is 200°C, the pipeline connected to the atomic layer deposition reaction chamber is heated to 100°C, the temperature range of the magnesium source is 60-100°C, and the temperature of the fluorine source is 25°C.

[0085] The first pulse is a bis(ethylcyclopentadienylmagnesium) pulse with a pulse time of 5 seconds; the nitrogen purge cleaning pulse time is 30 seconds; the hydrogen fluoride pulse time is 5 seconds; and the nitrogen cleaning pulse time is 30 seconds. The flow rates of bis(ethylcyclopentadienylmagnesium) and hydrogen fluoride carrier gases are 45 sccm, and the flow rates of nitrogen in other source pipelines are all set to 30 sccm. 800 cycles of the above steps are performed.

[0086] After the preparation is completed, some areas inside the atomic layer deposition reaction chamber are corroded by the precursor source, and the pipeline for transporting the precursor source needs to be treated with anti-corrosion. Even after the anti-corrosion treatment, after a certain period of deposition, the pipeline for transporting the precursor source is still corroded and needs to be replaced.

[0087] Table 1

[0088]

[0089]

[0090] As can be seen from Table 1, in Comparative Example 1, since hydrogen fluoride is used as a fluorine source, which is highly corrosive, the interior of the device for preparing the metal fluoride film needs to be treated with corrosion protection. However, after a period of deposition reaction, the corrosion resistance of the anti-corrosion film will also decrease, thereby affecting the reliability of the device. In addition, when the surface of some coated samples is a material that is not resistant to corrosion by fluorine sources such as hydrogen fluoride, the method of Comparative Example 1 cannot be applied. It can be seen from the data of Comparative Example 1 that due to the corrosiveness of hydrogen fluoride, the uniformity of the film (the uniformity of the film is as high as 1.2%, and the larger the uniformity parameter index, the worse the uniformity) and density (the film has a number of pinholes) will be affected, thereby affecting the further application of the film.

[0091] However, it can be seen from the test results of Examples 1 to 8 that when hexafluoroacetylacetonate is selected as the fluorine source and the metal precursor, the device and the coated sample will not be corroded, and the uniformity of the obtained film is ≤0.7%, which is significantly better than that of Comparative Example 1, and the prepared films are all dense films without pinholes. Therefore, the present invention uses plasma enhanced atomic layer deposition technology (PEALD) to prepare metal fluoride films, and uses surface controlled gas phase precursors to deposit ultra-thin, uniform, pinhole-free dense layers of metal fluoride films, which can greatly reduce the reaction temperature and do not use additional fluorine sources such as fluorine or hydrogen fluoride; compared with Thermal ALD technology, this method can ensure uniformity while greatly reducing the process temperature of the film preparation process and does not use additional fluorine sources such as fluorine or hydrogen fluoride and other corrosive materials.

[0092] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a metal fluoride thin film by low temperature ALD, characterized in that: Plasma-enhanced atomic layer deposition is performed on a metal precursor and oxygen plasma to obtain a metal fluoride film; The metal precursor is selected from hexafluoroacetylacetonate.

2. The method according to claim 1, characterized in that The following steps are involved: A) placing the coating sample in a reaction chamber device, introducing a metal precursor for a period of time, then introducing a protective atmosphere for purging, then introducing an oxygen source, turning on the radio frequency for plasma enhanced atomic layer deposition reaction, and then introducing a protective atmosphere for purging after the reaction to complete a sub-cycle deposition; B) Repeat step A) to obtain a metal fluoride film.

3. The method according to claim 1 or 2, characterized in that: The metal precursor is selected from at least one of magnesium hexafluoroacetylacetonate, lithium hexafluoroacetylacetonate, aluminum hexafluoroacetylacetonate, chromium hexafluoroacetylacetonate or hafnium hexafluoroacetylacetonate.

4. The method according to claim 2, characterized in that: The temperature of the reaction chamber device is 10-400° C., and the pressure is 0.2-10 mbar.

5. The method according to claim 2, characterized in that: In the step A), the metal precursor enters the reaction chamber via a carrier gas; The flow rate of the metal precursor is 100-500 sccm, the time of passing the metal precursor is 0.5-120 s, the heating temperature of the source bottle of the metal precursor is 80-150° C., and the heating temperature of the pipeline of the metal precursor is 90-200° C.; The carrier gas is selected from an inert gas, and the flow rate of the inert gas is 500-3000 sccm.

6. The method according to claim 2, characterized in that In the step A), the protective atmosphere is selected from nitrogen or argon, and the purging time is 5 to 120 seconds; And / or, the flow rate of the oxygen source is 500 to 1500 sccm, and the introduction time is 0.5 to 120 s; And / or, the radio frequency power is 100W to 10000W.

7. The method according to claim 2, characterized in that Before step A), a preheating process is also included, wherein the preheating temperature is 50-400° C., the preheating pressure is 0.2-10 mbar, and the preheating time is 500-2000 s.

8. A metal fluoride film prepared by the method according to any one of claims 1 to 7.

9. An antireflection film, characterized in that: Comprising the metal fluoride film as described in claim 8.

10. An anti-reflection film, characterized in that: Comprising the metal fluoride film as described in claim 8.

11. Use of the metal fluoride film according to claim 8 in the optical field.

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