Metal fluoride thin film, preparation method therefor and use thereof

Abstract

The present invention provides a preparation method for a metal fluoride thin film. An atomic layer deposition reaction is performed between a metal precursor and an oxygen source to obtain the metal fluoride thin film, the metal precursor is selected from hexafluoroacetylacetonate. The preparation method provided by the present invention does not employ toxic fluorine-containing gases, thereby ensuring the safety of deposition of the metal fluoride thin film. By adopting an atomic layer deposition method to prepare the metal fluoride thin film, the resulting film layer is uniform and has a dense surface, and exhibits strong corrosion resistance.

Description

A metal fluoride thin film, its preparation method and application

[0001] This application claims priority to Chinese Patent Application No. 202411572047.5, filed on November 5, 2024, entitled "A Metal Fluoride Thin Film and Its Low-Temperature ALD Preparation Method and Application", the entire contents of which are incorporated herein by reference.

[0002] This application claims priority to Chinese Patent Application No. 202411572046.0, filed on November 5, 2024, entitled "Yttrium Fluoride Thin Film, Preparation Method Thereof and Application Thereof", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention belongs to the field of thin film preparation technology, specifically relating to a metal fluoride thin film, its preparation method, and its application. Background Technology

[0004] Yttrium fluoride thin films have a low refractive index of only about 1.4, are non-toxic, and exhibit low absorption over a wide spectral range. Yttrium fluoride films, when combined with high-refractive-index materials, form important materials for fabricating one-dimensional photonic crystals and infrared interference filters, among other optical components. Currently, common methods for preparing yttrium fluoride thin films include evaporation deposition, magnetron sputtering, and chemical methods.

[0005] Magnetron sputtering is a low-temperature, high-speed thin-film deposition technique widely used in industrial production and scientific research. However, when using yttrium fluoride targets for thin film preparation, magnetron sputtering can easily lead to the loss of anionic fluoride ions, increased absorption, refractive index distortion, and functional failure. Simultaneously, the internal stress of the film becomes unstable, making it highly susceptible to cracking, detachment, and breakage, resulting in structural failure. Therefore, in the process of preparing yttrium fluoride thin films by magnetron sputtering, a reactive gas is generally used to replenish fluoride ions. If fluorine gas is used, this fluoride source is often highly corrosive. If perfluorinated carbon is used, impurity ions such as carbon are introduced into the film, significantly reducing the protective effect. For structural samples, physical vapor deposition (PVD) cannot guarantee the uniformity of the deposited film.

[0006] Therefore, it is of great significance to provide a non-corrosive fluorine source and a method for preparing metal fluoride films that ensures uniformity and density. Summary of the Invention

[0007] In view of this, the technical problem to be solved by the present invention is to provide a method for preparing a metal fluoride thin film. The preparation method provided by the present invention does not use a highly corrosive fluorine source, and the prepared film layer is dense and uniform.

[0008] This invention provides a method for preparing metal fluoride thin films, wherein a metal precursor is subjected to an atomic layer deposition reaction with an oxygen source to obtain a metal fluoride thin film;

[0009] The metal precursor is selected from hexafluoroacetylacetonate.

[0010] Preferably, the preparation method includes the following steps:

[0011] a) The coated sample is placed in the reaction chamber device, and after a period of time, a protective atmosphere is introduced to purge it. Then, an oxygen source is introduced to carry out the atomic layer deposition reaction. After the reaction, a protective atmosphere is introduced to purge it to complete one sub-cycle deposition.

[0012] b) Repeat step a) to obtain a metal fluoride film.

[0013] Preferably, the metal precursor is selected from at least one of magnesium hexafluoroacetylacetonate, lithium hexafluoroacetylacetonate, aluminum hexafluoroacetylacetonate, chromium hexafluoroacetylacetonate, hafnium hexafluoroacetylacetonate, and yttrium hexafluoroacetylacetonate.

[0014] The oxygen source includes ozone or oxygen plasma.

[0015] Preferably, the temperature of the reaction chamber device is 10–500°C and the pressure is 0.2–10 mbar;

[0016] The flow rate of the metal precursor is 100–500 sccm, and the time for introducing the metal precursor is 0.5–120 s.

[0017] The oxygen source has a flow rate of 500–1500 sccm and an introduction time of 0.5–120 s.

[0018] Preferably, the deposition rate for the atomic layer deposition reaction is:

[0019] Preferably, the preparation method is a method for preparing metal fluoride thin films by low-temperature ALD, comprising the following steps:

[0020] Metal fluoride films were obtained by plasma-enhanced atomic layer deposition of metal precursors with oxygen plasma.

[0021] The metal precursor is selected from hexafluoroacetylacetone compounds.

[0022] Preferably, the method includes the following steps:

[0023] A) Place the coated sample in the reaction chamber device, introduce the metal precursor for a period of time, then introduce a protective atmosphere to purge, then introduce an oxygen source, turn on the radio frequency to perform plasma-enhanced atomic layer deposition reaction, and after the reaction, introduce a protective atmosphere to purge to complete one sub-cycle deposition.

[0024] B) Repeat step A) to obtain a metal fluoride film.

[0025] Preferably, the metal precursor is selected from at least one of magnesium hexafluoroacetylacetonate, lithium hexafluoroacetylacetonate, aluminum hexafluoroacetylacetonate, chromium hexafluoroacetylacetonate, or hafnium hexafluoroacetylacetonate.

[0026] Preferably, the temperature of the reaction chamber device is 10–400°C and the pressure is 0.2–10 mbar.

[0027] Preferably, in step A), the metal precursor enters the reaction chamber via a carrier gas;

[0028] The flow rate of the metal precursor is 100-500 sccm, the time for introducing the metal precursor is 0.5-120 s, the heating temperature of the source bottle of the metal precursor is 80-150℃, and the heating temperature of the pipeline of the metal precursor is 90-200℃.

[0029] The carrier gas is selected from inert gases, and the flow rate of the inert gas is 500 to 3000 sccm.

[0030] Preferably, in step A), the protective atmosphere is selected from nitrogen or argon, and the purging time is 5 to 120 seconds.

[0031] And / or, the flow rate of the oxygen source is 500–1500 sccm, and the inlet time is 0.5–120 s;

[0032] And / or, the power of the radio frequency is 100W to 10000W.

[0033] Preferably, before step A), a preheating process is 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.

[0034] Preferably, the preparation method is a method for preparing a yttrium fluoride thin film, comprising the following steps:

[0035] S1) The substrate is placed in an atomic layer deposition apparatus, and a precursor containing both yttrium and fluorine is introduced. After the reaction, a film layer is formed on the surface of the substrate; the film layer is then purged.

[0036] S2) An oxygen source is introduced into the atomic layer deposition apparatus to react with the film layer, and then the mixture is purged again to obtain a yttrium fluoride thin film.

[0037] Preferably, after step S2), the method further includes:

[0038] The preparation cycle is repeated n times, with step S1) and step S2) as one preparation cycle, where n≥1;

[0039] And / or, in step S1), before introducing the precursor containing both yttrium and fluorine, the method further includes: adjusting the temperature of the atomic layer deposition apparatus to 200–500°C and the pressure to 0.2–1.0 mbar;

[0040] And / or, in step S1), the flow rate of the yttrium- and fluorine-containing precursor into the atomic layer deposition apparatus is 100–500 sccm, and the inlet time is 1–15 s; the heating temperature of the source bottle of the yttrium- and fluorine-containing precursor is 80–120°C, and the heating temperature of the source pipeline is 90–160°C.

[0041] Preferably, the precursor containing both yttrium and fluorine comprises yttrium hexafluoroacetylacetonate, and the oxygen source comprises ozone or oxygen plasma.

[0042] Preferably, in step S2), the flow rate of the oxygen source into the atomic layer deposition apparatus is 500-1500 sccm, and the introduction time is 1-15 s;

[0043] And / or, in step S1), the gas used for purging is nitrogen or argon, and the purging time is 5 to 50 seconds; in step S2), the gas used for the second purging is nitrogen or argon, and the purging time is 5 to 50 seconds.

[0044] Preferably, the preparation method is a method for preparing a yttrium fluoride thin film, comprising the following steps:

[0045] S1) The substrate is placed in an atomic layer deposition apparatus, a first precursor is introduced, and a film is formed on the surface of the substrate after reaction; the film is then subjected to a first purging.

[0046] S2) An oxygen source is introduced into the atomic layer deposition apparatus to react with the film layer, and a second purging is performed after the reaction;

[0047] S3) A second precursor is introduced into the atomic layer deposition apparatus and reacted with the film obtained in step S2) before a third purging is performed.

[0048] S4) An oxygen source is introduced into the atomic layer deposition apparatus to react with the film obtained in step S3), and then a fourth purging is performed to obtain a yttrium fluoride thin film.

[0049] The first precursor is selected from yttrium-containing precursors or fluorine-containing precursors, and correspondingly, the second precursor is selected from fluorine-containing precursors or yttrium-containing precursors.

[0050] Preferably, after step S4), the method further includes:

[0051] The preparation cycle is repeated n times, with each step S1), S2), S3), and S4) as one preparation cycle, where n ≥ 1.

[0052] And / or, in step S1), before introducing the first precursor, the method further includes: adjusting the temperature of the atomic layer deposition apparatus to 200-400°C and the pressure to 0.2-10 mbar;

[0053] And / or, the flow rate of the fluorine-containing precursor or the yttrium-containing precursor into the atomic layer deposition apparatus is independently 100–500 sccm, and the introduction time is independently 1–15 s; the heating temperature of the source bottle of the yttrium-containing precursor is 120–170°C, and the heating temperature of the source pipeline is 150–200°C.

[0054] Preferably, the yttrium-containing precursor includes yttrium triketoate, the fluorine-containing precursor includes hexafluoroacetylacetone, and the oxygen source includes ozone or oxygen plasma.

[0055] Preferably, in step S2), the flow rate of the oxygen source into the atomic layer deposition apparatus is 500-1500 sccm, and the introduction time is 1-15 s; in step S4), the flow rate of the oxygen source into the atomic layer deposition apparatus is 500-1500 sccm, and the introduction time is 1-15 s.

[0056] And / or, in step S1), the gas used for the first purging is argon or nitrogen, and the first purging time is 5 to 50 seconds; in step S2), the gas used for the second purging is argon or nitrogen, and the second purging time is 5 to 50 seconds; in step S3), the gas used for the third purging is argon or nitrogen, and the third purging time is 5 to 50 seconds; in step S4), the gas used for the fourth purging is argon or nitrogen, and the fourth purging time is 5 to 50 seconds.

[0057] Preferably, the substrate is a substrate that has undergone hydroxylation treatment.

[0058] The present invention also provides a metal fluoride thin film, which is prepared by the above preparation method.

[0059] The present invention also provides an antireflection membrane, comprising a metal fluoride film prepared by the above preparation method.

[0060] The present invention also provides an antireflective film, comprising a metal fluoride film prepared by the above preparation method.

[0061] The present invention also provides an application of the metal fluoride thin film prepared by the above preparation method in the field of optics.

[0062] The present invention also provides the application of yttrium fluoride film as an anti-corrosion coating on the surface of structural components, wherein the yttrium fluoride film is the yttrium fluoride film prepared by the above preparation method.

[0063] The present invention also provides a reaction chamber, including a structural component, wherein a yttrium fluoride film is formed on the surface of the structural component, and the yttrium fluoride film is the yttrium fluoride film prepared by the above preparation method.

[0064] The present invention also provides that the structural component is a spray structure.

[0065] Compared with existing technologies, this invention provides a method for preparing metal fluoride thin films, which involves atomic layer deposition of a metal precursor with an oxygen source to obtain a metal fluoride thin film; the metal precursor is selected from hexafluoroacetylacetonate. The preparation method provided by this invention does not use toxic fluorine-containing gases, ensuring the safety of metal fluoride thin film deposition; the use of atomic layer deposition to prepare the metal fluoride thin film results in a uniform film layer, a dense surface, and strong corrosion resistance. Attached Figure Description

[0066] Figure 1 shows the XPS test results of the metal fluoride thin film prepared in Example 1;

[0067] Figure 2 shows the refractive index test results of the metal fluoride thin film prepared in Example 1;

[0068] Figure 3 is a schematic diagram of the reaction route of the first method for producing yttrium fluoride thin films according to the present invention;

[0069] Figure 4 is a schematic diagram of the reaction route of the second method for producing yttrium fluoride thin films according to the present invention;

[0070] Figure 5 shows the XPS spectrum of the yttrium fluoride thin film prepared in Example 9 of this invention. Detailed Implementation

[0071] This invention provides a method for preparing metal fluoride thin films, wherein a metal precursor is subjected to an atomic layer deposition reaction with an oxygen source to obtain a metal fluoride thin film;

[0072] The metal precursor is selected from hexafluoroacetylacetone compounds.

[0073] In some specific embodiments of the present invention, the following steps are included:

[0074] a) The coated sample is placed in the reaction chamber device, and after a period of time, a protective atmosphere is introduced to purge it. Then, an oxygen source is introduced to carry out the atomic layer deposition reaction. After the reaction, a protective atmosphere is introduced to purge it to complete one sub-cycle deposition.

[0075] b) Repeat step a) to obtain a metal fluoride film.

[0076] Specifically, the present invention first places the coating sample in the reaction chamber device. The present invention does not have any special restrictions on the type of coating sample, and can select it as needed. The coating sample can be used as the coating sample of the method provided by the present invention as long as its temperature tolerance meets the process temperature. For example, it can be silicon substrate, wafer, optical lens, PET, PVC, metal, or glass.

[0077] This invention can deposit films on both planar and non-planar surfaces, ensuring good film uniformity. The non-planar surface can be a sphere, a partially spherical surface, a concave surface, a groove, or any other uneven surface. Preferably, this invention can deposit films on samples with large radii of curvature, resulting in films with excellent uniformity.

[0078] Before placing the coated sample into the reaction chamber device, the process includes a preheating step of the reaction chamber. The preheating temperature is 50–500°C, which can be any value between 50, 70, 90, 100, 150, 200, 250, 300, 350, 400, 450, 500°C, or 500°C. The preheating pressure is 0.2–10 mbar, which can be any value between 0.2, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 mbar, or 0.2–10 mbar. The preheating time is 500–2000 s, which can be any value between 500, 700, 1000, 1500, 2000 s, or 500–2000 s.

[0079] After preheating the reaction chamber, the coated sample is placed inside the reaction chamber apparatus. During the reaction process, the temperature of the reaction chamber apparatus is controlled to be between 10 and 500℃, and can be any value between 10, 20, 25, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 200, 250, 300, 350, 400, 450, and 500℃. The pressure in the reaction chamber is between 0.2 and 10 mbar, and can be any value between 0.2, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 mbar.

[0080] Then, a metal precursor is introduced for a period of time, and the metal precursor enters the reaction chamber through a carrier gas. The metal precursor is selected from at least one of magnesium hexafluoroacetylacetonate, lithium hexafluoroacetylacetonate, aluminum hexafluoroacetylacetonate, chromium hexafluoroacetylacetonate, hafnium hexafluoroacetylacetonate, and yttrium hexafluoroacetylacetonate; the flow rate of the metal precursor is 100–500 sccm, and can be any value between 100, 150, 200, 250, 300, 350, 400, 450, 500, or 100–500 sccm; the introduction time of the metal precursor is 0.5–120 s, and can be 0.5, 1, or 5 seconds. The heating temperature of the source bottle of the metal precursor is 80-150℃, and can be any value between 80, 90, 100, 120, 130, 140, 150, or 80-150℃; the heating temperature of the pipeline of the metal precursor is 90-200℃, and can be any value between 90, 100, 120, 140, 150, 160, 180, 200, or 90-200℃.

[0081] The carrier gas is selected from inert gases, and the flow rate of the inert gas is 500 to 3000 sccm, which can be any value between 500, 1000, 1500, 2000, 2500, 3000, or 500 to 3000 sccm.

[0082] Next, a protective atmosphere is introduced for purging, the protective atmosphere being selected from nitrogen or argon. The purging time is 5 to 120 seconds, and can be any value between 0.5, 1, 5, 10, 30, 50, 70, 90, 100, 120 seconds, or 5 to 120 seconds.

[0083] After purging, an oxygen source gas is introduced to carry out the atomic layer deposition reaction. The oxygen source includes ozone or oxygen plasma. The oxygen plasma can be obtained by ionizing an oxygen-containing gas. The oxygen-containing gas is selected from oxygen gas.

[0084] The oxygen source is introduced for a duration of 0.5 to 120 seconds, and can be any value between 0.5, 1, 5, 10, 30, 50, 70, 90, 100, 120 seconds, or 0.5 to 120 seconds; the oxygen source flow rate is 500 to 1500 sccm, and can be any value between 500, 700, 900, 1000, 1200, 1400, 1500 sccm, or 500 to 1500 sccm.

[0085] The plasma-enhanced atomic layer deposition reaction, during a sub-cycle deposition process, 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, 0.9, 1.0, or Any value between.

[0086] After deposition is complete, a protective atmosphere is introduced for purging, completing one sub-cycle deposition. The protective atmosphere is selected from nitrogen or argon. The purging time is 5–120 s, and can be any value between 0.5, 1, 5, 10, 30, 50, 70, 90, 100, 120, or 5–120 s.

[0087] Next, repeat the above steps until the metal fluoride film reaches the target thickness.

[0088] In some specific embodiments of the present invention, a method for preparing metal fluoride thin films by low-temperature ALD is provided, wherein a metal precursor is subjected to plasma-enhanced atomic layer deposition reaction with oxygen plasma to obtain a metal fluoride thin film.

[0089] The metal precursor is selected from hexafluoroacetylacetonate, preferably, the metal precursor is selected from at least one of magnesium hexafluoroacetylacetonate, lithium hexafluoroacetylacetonate, aluminum hexafluoroacetylacetonate, chromium hexafluoroacetylacetonate, or hafnium hexafluoroacetylacetonate.

[0090] Specifically, the method for preparing metal fluoride thin films by low-temperature ALD includes the following steps:

[0091] A) Place the coated sample in the reaction chamber device, introduce the metal precursor for a period of time, then introduce a protective atmosphere to purge, then introduce oxygen source gas, turn on the radio frequency to perform plasma-enhanced atomic layer deposition reaction, and after the reaction, introduce a protective atmosphere to purge to complete one sub-cycle deposition.

[0092] B) Repeat step A) to obtain a metal fluoride film.

[0093] The present invention first places the coating sample in the reaction chamber device. The present invention does not have any special restrictions on the type of coating sample, and can select it as needed. The coating sample can be used as the coating sample of the method provided by the present invention as long as its temperature resistance meets the process temperature. For example, it can be silicon substrate, wafer, optical lens, PET, PVC, metal, or glass.

[0094] This invention can deposit films on both planar and non-planar surfaces, ensuring good film uniformity. The non-planar surface can be a sphere, a partially spherical surface, a concave surface, a groove, or any other uneven surface. Preferably, this invention can deposit films on samples with large radii of curvature, resulting in films with excellent uniformity.

[0095] Before placing the coated sample into the reaction chamber device, the process includes a preheating step of the reaction chamber. The preheating temperature is 50–400°C, which can be any value between 50, 70, 90, 100, 150, 200, 250, 300, 350, 400°C, or 150–400°C. The preheating pressure is 0.2–10 mbar, which can be any value between 0.2, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 mbar, or 0.2–10 mbar. The preheating time is 500–2000 s, which can be any value between 500, 700, 1000, 1500, 2000 s, or 500–2000 s.

[0096] After preheating the reaction chamber, the coated sample is placed inside the reaction chamber device, and the temperature of the reaction chamber device is controlled during the reaction process to be between 10 and 400°C. The temperature can be any value between 10, 20, 25, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 200, 250, 300, 350, and 400°C; preferably, it is any value between 10 and 200°C. In this invention, because oxygen plasma is used, the process temperature can be lowered compared to the case without plasma, and the film can even be prepared at room temperature or below. In this invention, the room temperature condition is defined as 25 ± 5°C.

[0097] The pressure in the reaction chamber is 0.2 to 10 mbar, and can be any value between 0.2, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 0.2 to 10 mbar.

[0098] Then, a metal precursor is introduced for a period of time, and the metal precursor enters the reaction chamber through a carrier gas. The flow rate of the metal precursor is 100–500 sccm, and can be any value between 100, 150, 200, 250, 300, 350, 400, 450, 500, or 100–500 sccm; the introduction time of the metal precursor is 0.5–120 s, and can be between 0.5, 1, 5, 10, 30, 50, 70, 90, 100, 120, or 0.5–120 s. The heating temperature of the source bottle of the metal precursor is 80-150℃, and can be 80, 90, 100, 110, 120, 130, 140, 150, or any value between 80 and 150℃; the heating temperature of the pipeline of the metal precursor is 90-200℃, and can be 90, 100, 120, 140, 150, 160, 180, 200, or any value between 90 and 200℃;

[0099] The carrier gas is selected from inert gases, and the flow rate of the inert gas is 500 to 3000 sccm, which can be any value between 500, 1000, 1500, 2000, 2500, 3000, or 500 to 3000 sccm.

[0100] Next, a protective atmosphere is introduced for purging, the protective atmosphere being selected from nitrogen or argon. The purging time is 5 to 120 seconds, and can be any value between 0.5, 1, 5, 10, 30, 50, 70, 90, 100, 120 seconds, or 5 to 120 seconds.

[0101] After purging, oxygen source gas is introduced, and radio frequency is simultaneously activated to perform plasma-enhanced atomic layer deposition (PEALD). The oxygen source is selected from oxygen-containing gases, preferably oxygen gas. The oxygen source introduction time is 0.5–120 s, and can be any value between 0.5, 1, 5, 10, 30, 50, 70, 90, 100, 120, or 0.5–120 s; the oxygen source flow rate is 500–1500 sccm, and can be any value between 500, 700, 900, 1000, 1200, 1400, 1500, or 500–1500 sccm. The power of the radio frequency is 100W to 10000W, and can be any value between 100, 500, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, or 100W to 10000W. During the plasma-enhanced atomic layer deposition reaction, the oxygen source and its delivery pipeline do not require heating, thus reducing preparation costs.

[0102] The plasma-enhanced atomic layer deposition reaction, during a sub-cycle deposition process, 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 between.

[0103] After deposition is complete, a protective atmosphere is introduced for purging, completing one sub-cycle deposition. The protective atmosphere is selected from nitrogen or argon. The purging time is 5–120 s, and can be any value between 0.5, 1, 5, 10, 30, 50, 70, 90, 100, 120, or 5–120 s.

[0104] Next, repeat the above steps until the metal fluoride film reaches the target thickness.

[0105] In this invention, taking the coated sample as a wafer, the precursor as magnesium hexafluoroacetylacetonate, and oxygen as the oxygen source as an example, the preparation mechanism of the magnesium fluoride thin film is as follows:

[0106] Step 1: Magnesium hexafluoroacetylacetonate is introduced into the reaction chamber for low-temperature ALD (Alternating Current Deposition) of metal fluoride thin films via an inert gas conveying pipeline, where it adsorbs onto the coated sample, forming a surface containing HFAC. - The membrane layer;

[0107] After purging with inert gas, excess and unreacted precursors are removed;

[0108] Step 2: Introduce O2, turn on the radio frequency, and the oxygen forms oxygen plasma that reacts with the HFAC in the membrane. - The reaction forms Mg-CO3 2- and some free F - F - Further replace CO3 2- With Mg 2+ They combine to form MgF2, which is then deposited on the substrate.

[0109] After purging with inert gas to remove the byproducts of the reaction, a stable MgF2 film is obtained.

[0110] In some specific embodiments of the present invention, when the metal precursor is selected from magnesium hexafluoroacetylacetonate, the chemical reaction formula is as follows: Mg(hfac)2 + O2plasma → MgF2.

[0111] 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 can be prepared according to the above mechanism.

[0112] This invention employs plasma-enhanced atomic layer deposition (PEALD) to prepare metal fluoride thin films. By utilizing surface-controlled vapor phase precursor deposition, it achieves ultrathin, uniform, and pinhole-free dense metal fluoride films, significantly reducing reaction temperatures and eliminating the need for additional fluorine sources such as elemental fluorine or hydrogen fluoride. Compared to vacuum evaporation and magnetron sputtering, this method offers better and more controllable film uniformity for samples with large radii of curvature. Compared to thermal ALD, it ensures uniform film preparation without the use of corrosive materials such as elemental fluorine or hydrogen fluoride, while significantly reducing the process temperature during film preparation.

[0113] 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.

[0114] The thickness of the metal fluoride film can be as low as less than 1 nm, and it can uniformly cover the surface of the coated sample.

[0115] The refractive index of the metal fluoride film is 1.32 to 1.40, preferably 1.32 to 1.35.

[0116] The metal fluoride film has a uniform thickness and a dense surface.

[0117] The present invention also provides an antireflective coating comprising the aforementioned metal fluoride film. The antireflective coating structure comprises: a lens or glass, and alternatingly stacked low-refractive-index layers and high-refractive-index layers laminated on the surface of the lens or glass, wherein the high-refractive-index layer is made of a high-refractive-index material selected from one or more of TiO2, Ta2O5, and Nb2O5, and the low-refractive-index layer is selected from the aforementioned metal fluoride film, preferably the aforementioned magnesium fluoride film.

[0118] The present invention also provides an antireflective coating comprising the aforementioned metal fluoride film. The antireflective coating comprises a lens or glass and a low-refractive-index layer laminated to the surface of the lens or glass, wherein the low-refractive-index layer is selected from the aforementioned metal fluoride film, preferably the aforementioned magnesium fluoride film.

[0119] In some specific embodiments of the present invention, a method for preparing yttrium fluoride thin films is provided, comprising the following steps:

[0120] S1) The substrate is placed in an atomic layer deposition apparatus, and a precursor containing both yttrium and fluorine is introduced. After the reaction, a film layer is formed on the surface of the substrate; the film layer is then purged.

[0121] S2) An oxygen source is introduced into the atomic layer deposition apparatus to react with the film layer, and then the mixture is purged again to obtain a yttrium fluoride thin film.

[0122] In this invention, the preparation of the yttrium fluoride thin film includes two technical routes based on the differences in the precursor. The above-described preparation method is one such route. In this route, the precursor containing both yttrium and fluorine includes yttrium hexafluoroacetylacetonate (Y(hfac)3) and the oxygen source includes ozone or oxygen plasma. In a specific embodiment, the precursor is selected from yttrium hexafluoroacetylacetonate (Y(hfac)3) and the oxygen source is selected from ozone. Based on this, the method for preparing the yttrium fluoride thin film includes alternately and sequentially exposing the substrate to yttrium hexafluoroacetylacetonate (Y(hfac)3) and ozone, thereby preparing the yttrium fluoride thin film. The chemical reaction formula is as follows: Y(hfac)3 + O3 → YF3.

[0123] Specifically, in the preparation process of yttrium fluoride thin films, the present invention first places the substrate in an atomic layer deposition apparatus, introduces yttrium hexafluoroacetylacetonate (YTA), and after the reaction, forms a film layer on the substrate surface, which is then purged. During this process, before introducing YTA, the temperature and pressure of the atomic layer deposition apparatus are adjusted. The temperature is 200–500°C, and the pressure is 0.2–10 mbar; specifically, the temperature is 250–450°C, and the pressure is 1–8 mbar; more specifically, the temperature is 300–400°C, and the pressure is 3–6 mbar. The substrate is a substrate capable of film deposition using atomic layer deposition technology, and is a substrate well-known to those skilled in the art. Specifically, the substrate can be a semiconductor substrate, including silicon wafers, stainless steel substrates, PVC substrates, aluminum alloy substrates, etc. To further improve the adhesion between the film layer and the substrate, the substrate is a hydroxylated substrate. The hydroxylation treatment is a process well-known to those skilled in the art, and the present invention does not impose any particular limitations on it. The flow rate of yttrium hexafluoroacetylacetonate introduced is 100–500 sccm, and the introduction time is 1–15 s. Specifically, the flow rate of yttrium hexafluoroacetylacetonate introduced is 300–400 sccm, and the introduction time is 5–10 s. The purging is specifically performed using inert gas nitrogen or argon to purge residual chemical sources. The purging time is 5–50 s, specifically 15–45 s, and more specifically, 20–40 s.

[0124] The present invention then introduces ozone into the atomic layer deposition apparatus to react with the pre-reacted film layer, followed by purging to obtain a yttrium fluoride thin film. During this process, the ozone flow rate into the atomic layer deposition apparatus is 500–1500 sccm, and the flow time is 1–15 s. Specifically, the ozone flow rate is 800–1200 sccm, and the flow time is 5–12 s; more specifically, the ozone flow rate is 900–1000 sccm, and the flow time is 8–10 s. The purging is specifically performed using inert gases such as nitrogen or argon to remove residual chemical sources, and the purging time is 5–50 s. Specifically, the purging time is 15–45 s, and more specifically, the purging time is 20–40 s.

[0125] The above process completes one atomic layer deposition of yttrium fluoride thin film, at a deposition rate of [missing information]. Specifically, the deposition rate is During the deposition process, the source bottle of yttrium hexafluoroacetylacetonate is heated to 80-120°C, and the source pipeline is heated to 90-160°C. Specifically, the source bottle of yttrium hexafluoroacetylacetonate is heated to 90-100°C, and the source pipeline is heated to 105-150°C; the oxygen source and the delivery pipeline are at room temperature and do not need to be heated.

[0126] The technical route of the above process of the present invention is shown in Figure 3. Taking a silicon substrate as the substrate, yttrium-containing and fluorine-containing precursor yttrium hexafluoroacetylacetonate (Y(hfac)3) as the precursor, and ozone as the oxygen source, the specific preparation mechanism of the yttrium fluoride thin film is as follows:

[0127] Step 1: Y(hfac)3 is introduced into the reaction chamber of the atomic layer deposition apparatus by an inert gas through a delivery pipe, where it is adsorbed onto the substrate, forming a surface containing hfac. - The membrane layer;

[0128] After purging with inert gas, excess and unreacted precursor Y(hfac)3 is removed;

[0129] Step 2: Introduce O3 to react with HFAC in the membrane layer. - The reaction forms Y-CO3 - and some free F - F - Further replace CO3 - With Y + YF3 is formed by bonding and deposited on the substrate;

[0130] After purging with inert gas to remove the byproducts from the reaction, a stable YF3 film is obtained.

[0131] In this invention, the atomic layer deposition process described above can be repeated multiple times depending on the thickness of the yttrium fluoride film. The number of repetitions can be ≥1 time, ≥10 times, or ≥100 times. The number of repetitions can be adjusted according to the thickness requirements of the yttrium fluoride film. In a specific embodiment, the atomic layer deposition process is repeated 600 times, thereby obtaining a 30 nm yttrium fluoride film.

[0132] This invention also provides a method for preparing yttrium fluoride thin films, comprising the following steps:

[0133] S1) The substrate is placed in an atomic layer deposition apparatus, a first precursor is introduced, and a film is formed on the surface of the substrate after reaction; the film is then subjected to a first purging.

[0134] S2) An oxygen source is introduced into the atomic layer deposition apparatus to react with the film layer, and a second purging is performed after the reaction;

[0135] S3) A second precursor is introduced into the atomic layer deposition apparatus and reacted with the film obtained in step S2) before a third purging is performed.

[0136] S4) An oxygen source is introduced into the atomic layer deposition apparatus to react with the film obtained in step S3), and then a fourth purging is performed to obtain a yttrium fluoride thin film.

[0137] The first precursor is selected from yttrium-containing precursors or fluorine-containing precursors, and correspondingly, the second precursor is selected from fluorine-containing precursors or yttrium-containing precursors.

[0138] The above-described preparation method is another technical route for yttrium fluoride thin films, which also achieves the preparation of yttrium fluoride thin films through atomic layer deposition. In the above method, the yttrium-containing precursor includes yttrium triketoate (Y(thd)3), the fluorine-containing precursor includes hexafluoroacetylacetone (Hhfac), and the oxygen source includes ozone or oxygen plasma. In a specific embodiment, the yttrium-containing precursor is selected from yttrium triketoate (Y(thd)3), the fluorine-containing precursor is selected from hexafluoroacetylacetone (Hhfac), and the oxygen source is selected from ozone. The fluorine-containing precursor used in this invention does not use toxic fluorine sources well known to those skilled in the art, such as TiF4 or HF. Based on this, the method for preparing yttrium fluoride thin films includes alternating and sequentially exposing the substrate to a reactant of yttrium precursor yttrium triketoate Y(thd)3 (or fluorine precursor hexafluoroacetylacetone (Hhfac)), ozone, fluorine precursor hexafluoroacetylacetone (Hhfac) (or yttrium precursor yttrium triketoate Y(thd)3), and ozone. The specific chemical reaction formula is: Y(thd)3 + O3 + Hhfac + O3 → YF3 or Hhfac + O3 + Y(thd)3 + O3 → YF3.

[0139] Specifically, in the preparation process of yttrium fluoride thin films, taking the reaction of yttrium triketoate (Y(Thd)3), ozone, hexafluoroacetylacetone (Hhfac), and ozone sequentially introduced into an atomic layer deposition apparatus as an example, the present invention first places the substrate in the atomic layer deposition apparatus, introduces yttrium triketoate, and after the reaction, a film layer is formed on the surface of the substrate, and then the film layer is subjected to a first purging; in this process, before introducing yttrium triketoate, the temperature and pressure of the atomic layer deposition apparatus are adjusted, the temperature is 200-400°C, and the pressure is 0.2-10 mbar, specifically, the temperature is 250-350°C, and the pressure is 1-8 mbar. The substrate is a substrate capable of film deposition using atomic layer deposition technology, and is a substrate well-known to those skilled in the art. Specifically, the substrate can be a semiconductor substrate, including silicon wafers, stainless steel substrates, PVC substrates, aluminum alloy substrates, etc. To further improve the adhesion between the film layer and the substrate, the substrate is a substrate that has undergone hydroxylation treatment. The hydroxylation treatment is a process well-known to those skilled in the art, and this invention does not impose any particular limitation on it. The flow rate of yttrium triketoate introduced is 100–500 sccm, and the introduction time is 1–15 s. Specifically, the flow rate of yttrium triketoate introduced is 300–400 sccm, and the introduction time is 5–10 s. The first purging is specifically performed using inert gas nitrogen or argon to purge residual chemical sources. The first purging time is 5–50 s, specifically 15–45 s, and more specifically, 20–40 s.

[0140] In this invention, ozone is then introduced into the atomic layer deposition apparatus to react with the pre-reacted film layer. A second purging process is then performed. During this process, the ozone flow rate into the atomic layer deposition apparatus is 500–1500 sccm, and the introduction time is 1–15 s. Specifically, the ozone flow rate is 800–1200 sccm, and the introduction time is 5–12 s. More specifically, the ozone flow rate is 900–1000 sccm, and the introduction time is 8–10 s. The second purging is specifically performed using inert gases such as nitrogen or argon to remove residual chemical sources. The second purging time is 5–50 s, specifically 15–45 s, and more specifically, 20–40 s.

[0141] According to the present invention, hexafluoroacetylacetone is then introduced into the atomic layer deposition apparatus to react with the film obtained by the above reaction, followed by a third purging. During this process, the flow rate of the introduced hexafluoroacetylacetone is 100–500 sccm, and the introduction time is 1–20 s. Specifically, the flow rate of the introduced hexafluoroacetylacetone is 300–400 sccm, and the introduction time is 5–15 s. The hexafluoroacetylacetone is introduced to react with the film. The third purging is specifically performed using an inert gas, nitrogen or argon, to purge residual chemical sources. The third purging time is 5–50 s, specifically 15–45 s, and more specifically, 20–40 s.

[0142] Finally, ozone is introduced into the atomic layer deposition apparatus to react with the pre-reacted film layer. A fourth purging is then performed. During this process, the ozone flow rate into the atomic layer deposition apparatus is 500–1500 sccm, and the introduction time is 1–15 s. Specifically, the ozone flow rate is 800–1200 sccm, and the introduction time is 5–12 s. More specifically, the ozone flow rate is 900–1000 sccm, and the introduction time is 8–10 s. The fourth purging is specifically performed using inert gases such as nitrogen or argon to purge residual chemical sources. The fourth purging time is 5–50 s, specifically 15–45 s, and more specifically, 20–40 s.

[0143] The above process completes one atomic layer deposition of yttrium fluoride thin film, at a deposition rate of [missing information]. Specifically, the deposition rate is During the deposition process, the source bottle for the yttrium precursor is heated to 120–170°C, and the source pipeline is heated to 150–200°C. The source bottle and source pipeline for the fluorine precursor are not heated. Specifically, the source bottle for the yttrium precursor is heated to 140–150°C, and the source pipeline is heated to 155–180°C. The oxygen source and delivery pipeline are at room temperature and do not require heating.

[0144] The technical route of the above process of the present invention is shown in Figure 4. Taking silicon substrate as the substrate, yttrium tridiketate yttrium (Thd)3 as the yttrium precursor, ozone as the oxygen source, and hexafluoroacetylacetone (Hhfac) as the fluorine precursor as an example, the preparation mechanism of the yttrium fluoride thin film is as follows:

[0145] Step 1: Y(thd)3 is introduced into the reaction chamber of the atomic layer deposition apparatus by an inert gas through a delivery pipe, where it is adsorbed onto the substrate to form a surface containing thd. - The membrane layer;

[0146] After purging with inert gas, excess and unreacted precursor Y(thd)3 is removed;

[0147] Step 2: Introduce O3 to react with the thd in the membrane layer. - The reaction forms Y-CO3 - ;

[0148] Excess reaction byproducts are removed by purging with inert gas.

[0149] Step 3: Introduce Hhfac, which is physically adsorbed onto the membrane surface;

[0150] After purging with inert gas, excess precursor Hhfac is removed;

[0151] Step 4: Introduce O3 to form Y-CO3 - and F - F - Further replace CO3 - A YF3 thin film is formed and deposited on the substrate surface;

[0152] After purging with inert gas to remove excess reaction byproducts, a stable YF3 film is obtained.

[0153] In this invention, the atomic layer deposition process described above can be repeated multiple times depending on the thickness of the yttrium fluoride film, up to 1 time, 10 times, or 100 times, depending on the required thickness of the yttrium fluoride film. In a specific embodiment, the atomic layer deposition process is repeated 600 times, thereby obtaining a 30 nm yttrium fluoride film.

[0154] In the above technical route, the reactants are sequentially introduced into an atomic layer deposition apparatus in the order of yttrium triketoate-ozone-hexafluoroacetylacetone-ozone to prepare yttrium fluoride thin films. Similarly, the reactants can also be sequentially introduced into an atomic layer deposition apparatus in the order of hexafluoroacetylacetone-ozone-yttrium triketoate-ozone to prepare yttrium fluoride thin films, as detailed below:

[0155] This invention first places a substrate in an atomic layer deposition apparatus, introduces hexafluoroacetylacetone, and after the reaction, forms a film on the substrate surface. The film is then subjected to a first purging. During this process, before introducing hexafluoroacetylacetone, the temperature and pressure of the atomic layer deposition apparatus are adjusted. The temperature is 200–400°C, and the pressure is 0.2–10 mbar; specifically, the temperature is 250–350°C, and the pressure is 1–8 mbar. The substrate is a substrate capable of film deposition using atomic layer deposition technology, and is a substrate well-known to those skilled in the art. Specifically, the substrate can be a semiconductor substrate, including silicon wafers, stainless steel substrates, PVC substrates, aluminum alloy substrates, etc. To further improve the adhesion between the film and the substrate, the substrate is a hydroxylated substrate. The hydroxylation treatment is a process well-known to those skilled in the art, and this invention does not impose any particular limitations on it. The flow rate of hexafluoroacetylacetone introduced is 100–500 sccm, and the introduction time is 1–15 s. Specifically, the flow rate of hexafluoroacetylacetone introduced is 300–400 sccm, and the introduction time is 5–10 s. The first purging is specifically performed using inert gas nitrogen or argon to purge residual chemical sources. The first purging time is 5–50 s, specifically 15–45 s, and more specifically, 20–40 s.

[0156] In this invention, ozone is then introduced into the atomic layer deposition apparatus to react with the pre-reacted film layer. A second purging process is then performed. During this process, the ozone flow rate into the atomic layer deposition apparatus is 500–1500 sccm, and the introduction time is 1–15 s. Specifically, the ozone flow rate is 800–1200 sccm, and the introduction time is 5–12 s. More specifically, the ozone flow rate is 900–1000 sccm, and the introduction time is 8–10 s. The second purging is specifically performed using inert gases such as nitrogen or argon to remove residual chemical sources. The second purging time is 5–50 s, specifically 15–45 s, and more specifically, 20–40 s.

[0157] According to the present invention, yttrium triketoate is then introduced into the atomic layer deposition apparatus to react with the film obtained by the above reaction, followed by a third purging. During this process, the flow rate of yttrium triketoate is 100–500 sccm, and the introduction time is 1–20 s. Specifically, the flow rate of yttrium triketoate is 300–400 sccm, and the introduction time is 5–15 s. The yttrium triketoate is introduced and reacts with the film. The third purging is specifically performed using an inert gas, nitrogen or argon, to purge residual chemical sources. The third purging time is 5–50 s, specifically 15–45 s, and more specifically, 20–40 s.

[0158] Finally, ozone is introduced into the atomic layer deposition apparatus to react with the pre-reacted film layer. A fourth purging is then performed. During this process, the ozone flow rate into the atomic layer deposition apparatus is 500–1500 sccm, and the introduction time is 1–15 s. Specifically, the ozone flow rate is 800–1200 sccm, and the introduction time is 5–12 s. More specifically, the ozone flow rate is 900–1000 sccm, and the introduction time is 8–10 s. The fourth purging is specifically performed using inert gases such as nitrogen or argon to purge residual chemical sources. The fourth purging time is 5–50 s, specifically 15–45 s, and more specifically, 20–40 s.

[0159] The above process completes one atomic layer deposition of yttrium fluoride thin film, at a deposition rate of [missing information]. Specifically, the deposition rate is During the deposition process, the source bottle for the yttrium precursor is heated to 120–170°C, and the source pipeline is heated to 150–200°C. The source bottle and source pipeline for the fluorine precursor are not heated. Specifically, the source bottle for the yttrium precursor is heated to 140–150°C, and the source pipeline is heated to 155–180°C. The oxygen source and delivery pipeline are at room temperature and do not require heating.

[0160] In the above process of the present invention, taking silicon substrate as the substrate, yttrium tridiketate yttrium (Thd)3 as the yttrium precursor, ozone as the oxygen source, and hexafluoroacetylacetone (Hhfac) as the fluorine precursor as an example, the preparation mechanism of the yttrium fluoride thin film is as follows:

[0161] Step 1: Hhfac is carried into the reaction chamber of the atomic layer deposition apparatus by an inert gas through a delivery pipe, where it is adsorbed on the substrate, forming a surface containing hfac. - The membrane layer;

[0162] After purging with inert gas, excess and unreacted precursor Hhfac is removed;

[0163] Step 2: Introduce O3 to react with HFAC in the membrane layer. - The reaction forms Y-CO3 - ;

[0164] Excess reaction byproducts are removed by purging with inert gas.

[0165] Step 3: Introduce Y(thd)3, which is physically adsorbed onto the film surface;

[0166] After purging with inert gas, excess precursor Y(thd)3 is removed;

[0167] Step 4: Introduce O3 to form Y-CO3 - and F - F - Further replace CO3 - A YF3 thin film is formed and deposited on the substrate surface;

[0168] After purging with inert gas to remove excess reaction byproducts, a stable YF3 film is obtained.

[0169] In this invention, the atomic layer deposition process described above can be repeated multiple times depending on the thickness of the yttrium fluoride film, up to 1 time, 10 times, or 100 times, depending on the required thickness of the yttrium fluoride film. In a specific embodiment, the atomic layer deposition process is repeated 600 times, thereby obtaining a 30 nm yttrium fluoride film.

[0170] In this invention, the atomic layer deposition apparatus is an atomic layer deposition apparatus well known to those skilled in the art, that is, the atomic layer deposition apparatus only needs to be able to achieve atomic layer deposition, and the present invention does not impose any special restrictions on its specific structure.

[0171] The present invention also provides a yttrium fluoride thin film, which is prepared by the above method.

[0172] The yttrium fluoride thin film prepared by this invention has a dense and uniform surface with a thickness uniformity of less than 3%. Thickness uniformity is the characteristic of a film maintaining a relatively consistent thickness. The lower the value, the better the thickness uniformity. Thickness uniformity is a thin film characteristic that cannot be ignored. The yttrium fluoride thin film prepared by this invention using atomic layer deposition has good thickness uniformity, which also makes the film structurally stable.

[0173] The present invention also provides a reaction chamber, including a structural component, the surface of which is formed with a yttrium fluoride film, wherein the yttrium fluoride film is the yttrium fluoride film prepared by the above-described scheme.

[0174] In this invention, the structural components in the reaction chamber are not particularly limited. Any structural component requiring corrosion protection can have a yttrium fluoride film formed on its surface. For example, the structural component can be a spray device, specifically a spray plate. The yttrium fluoride film can be uniformly deposited on the surface of the showerhead and in the spray holes. The yttrium fluoride film has high thickness uniformity and good density, and will not affect the spraying effect of the spray head's spray holes, further achieving environmental protection and effectively protecting against the corrosion of halogen-containing plasma and fluorine-containing gases.

[0175] Furthermore, the present invention also provides the application of yttrium fluoride film as an anti-corrosion coating on the surface of structural components.

[0176] The yttrium fluoride thin film prepared by this invention has good anti-corrosion effect and can be applied to the surface of various structural components in the cavity of semiconductor manufacturing process. The structural components can be made of stainless steel, pure metal, aluminum alloy, etc. The yttrium fluoride thin film is formed on the surface of all or part of the above structural components using atomic layer deposition method to achieve corrosion resistance.

[0177] This invention provides a method for preparing yttrium fluoride thin films. Essentially, it utilizes atomic layer deposition (ALD) to prepare yttrium fluoride thin films, employing two pathways of metal-organic source precursors and oxygen source as reaction sources. It avoids the use of toxic fluorine-containing gases, ensuring the safety of the film deposition process. Furthermore, the preparation process involves low temperature, is environmentally friendly, allows for controllable film thickness, and is easy to implement. The yttrium fluoride thin films prepared by ALD are uniform, have a dense surface, and exhibit strong corrosion resistance. Especially for structured samples, ALD technology can ensure uniform coverage of the yttrium fluoride thin film at the required protected locations.

[0178] To further understand the present invention, the following embodiments illustrate the metal fluoride thin film, its preparation method, and its application. The scope of protection of the present invention is not limited by the following embodiments.

[0179] Example 1

[0180] The goal is to deposit a MgF2 thin film on the wafer surface:

[0181] First, the wafer is fed into the reaction chamber, which undergoes vacuuming and preheating. The chamber temperature is set to 150°C, and the vacuum pressure is controlled at 1 mbar via a butterfly valve. After reaching the desired temperature and pressure, preheating is performed for 1000 seconds. Next, atomic layer deposition (ALD) is carried out. Magnesium hexafluoroacetylacetonate (Mg6F) is introduced into the chamber using a carrier gas at a flow rate of 300 sccm for 5 seconds. Then, inert argon gas is introduced for purging for 15 seconds. After purging, oxygen is introduced for 2 seconds at a flow rate of 1000 sccm. Simultaneously, the RF power supply is turned on at 1000 W to complete the oxygen deposition process. Finally, inert argon gas is introduced for purging for 10 seconds, completing one sub-cycle of atomic layer deposition for the magnesium fluoride film. The deposition rate of magnesium fluoride is... The cycle was repeated 1000 times to obtain a film material with a target thickness of 5 nm. The refractive index and XPS values ​​of the deposited material were then tested. The results are shown in Figures 1 and 2. Figure 1 shows the XPS test results of the metal fluoride film prepared in Example 1, and Figure 2 shows the refractive index test results of the metal fluoride film prepared in Example 1.

[0182] As shown in Figure 1, the MgF2 thin film prepared by the low-temperature PEALD method was characterized by XPS film characterization, which showed that the Mg:F ratio was 1:1.8 and the C impurity content in the film was <2%. Therefore, it can be concluded that the prepared film is a MgF2 thin film with low impurity content and high purity.

[0183] As shown in Figure 2, the refractive index of the prepared thin film, measured by ellipsometer, is 1.337, which is extremely low and meets the requirements of optical applications.

[0184] The uniformity of the film was tested, and the ratio of the film thickness deviation to the average film thickness was calculated. The results are shown in Table 1.

[0185] The compactness of the thin film was tested, and the results are shown in Table 1.

[0186] Example 2

[0187] Based on Example 1, the precursor was changed to lithium hexafluoroacetylacetonate.

[0188] Example 3

[0189] Based on Example 1, the precursor was changed to aluminum hexafluoroacetylacetonate.

[0190] Example 4

[0191] Based on Example 1, the precursor was changed to chromium hexafluoroacetylacetonate.

[0192] Example 5

[0193] Based on Example 1, the precursor was changed to hafnium hexafluoroacetylacetonate.

[0194] Example 6

[0195] Based on Example 1, the reaction chamber temperature was changed to 200°C, the pressure to 3 mbar, the metal precursor flow rate to 200 sccm, and the induction time to 10 s. Then, inert argon gas was introduced for 15 s to purge, followed by oxygen introduction for 2 s at a flow rate of 1000 sccm. Simultaneously, the radio frequency (RF) was activated with a power setting of 3000 W. Then, inert argon gas was introduced for 10 s to purge, completing one sub-cycle of magnesium fluoride film deposition. The deposition rate was... Repeat this cycle 300 times to obtain a film material with a target thickness of 6 nm.

[0196] Example 7

[0197] Based on Example 1, the reaction chamber temperature was changed to 300℃, the pressure to 5 mbar, the metal precursor flow rate to 400 sccm, and the induction time to 5 s. Then, inert argon gas was introduced for 15 s purging, followed by oxygen introduction for 2 s at a flow rate of 1000 sccm. Simultaneously, the radio frequency (RF) was activated with a power setting of 5000 W. Then, inert argon gas was introduced for 10 s purging, completing one sub-cycle deposition of the magnesium fluoride thin film. The deposition rate was... Repeat this cycle 133 times to obtain a film material with a target thickness of 4 nm.

[0198] Example 8

[0199] Based on Example 1, the reaction chamber temperature was changed to 400℃, the pressure to 8 mbar, the metal precursor flow rate to 500 sccm, and the induction time to 3 s. Then, inert argon gas was introduced for 15 s to purge, followed by oxygen introduction for 2 s at a flow rate of 1000 sccm. Simultaneously, the radio frequency (RF) was activated with a power setting of 8000 W. Then, inert argon gas was introduced for 10 s to purge, completing one sub-cycle of magnesium fluoride film deposition. The deposition rate was... Repeat this cycle 50 times to obtain a film material with a target thickness of 4 nm.

[0200] Comparative Example 1

[0201] S100: The substrate is transferred to the atomic layer deposition reaction chamber. The substrate can serve as a deposition carrier for magnesium fluoride thin films.

[0202] S200: The magnesium source is introduced into the atomic layer deposition reaction chamber by the carrier gas. The magnesium source is diethylcyclopentadienyl magnesium, and the heating temperature of diethylcyclopentadienyl magnesium is 60-100℃. Then, a protective gas is introduced for purging.

[0203] S300: A fluorine source, hydrogen fluoride, is introduced into the atomic layer reaction chamber at room temperature, and then the atomic layer deposition reaction chamber is purged with gas.

[0204] The preparation conditions for the atomic layer deposition reaction chamber are as follows: 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.

[0205] The first pulse is a diethylcyclopentadienyl magnesium pulse with a pulse duration of 5 seconds; the nitrogen purging pulse duration is 30 seconds; the hydrogen fluoride pulse duration is 5 seconds; and the nitrogen purging pulse duration is 30 seconds. The carrier gas flow rates for diethylcyclopentadienyl magnesium and hydrogen fluoride are 45 sccm, and the nitrogen flow rates for other source lines are all set to 30 sccm. Perform 800 cycles of the above steps.

[0206] After preparation, 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 anti-corrosion treatment, the pipeline for transporting the precursor source will still be corroded after a certain period of deposition and needs to be replaced.

[0207] Table 1

[0208] As shown in Table 1, in Comparative Example 1, because hydrogen fluoride is used as the fluorine source, it is highly corrosive. Therefore, the internal components of the apparatus for preparing metal fluoride thin films require corrosion protection. However, after a period of deposition reaction, the corrosion resistance of the anti-corrosion film will decrease, thus affecting the reliability of the apparatus. Furthermore, when the surface of some coated samples is a substance that is not resistant to corrosion from fluorine sources such as hydrogen fluoride, the method in Comparative Example 1 is not applicable. The data from Comparative Example 1 show that the corrosiveness of hydrogen fluoride affects the uniformity (the film uniformity is as high as 1.2%, with a higher uniformity parameter indicating poorer uniformity) and density (the film has several pinholes), thus affecting the further application of the film.

[0209] However, the test results from Examples 1-8 show that when hexafluoroacetylacetone is used as the fluorine source and metal precursor, it does not corrode the device or the coated sample. 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, this invention uses plasma-enhanced atomic layer deposition (PEALD) technology to prepare metal fluoride films. By using surface-controlled vapor phase precursor deposition, an ultrathin, uniform, pinhole-free dense metal fluoride film can be obtained, which can significantly reduce the reaction temperature and eliminate the need for additional fluorine sources such as elemental fluorine or hydrogen fluoride. Compared with Thermal ALD technology, this method can ensure uniformity while significantly reducing the process temperature of film preparation and eliminating the need for additional corrosive materials such as elemental fluorine or hydrogen fluoride.

[0210] Example 9

[0211] A 30 nm thick YF3 thin film was deposited on the surface of a silicon wafer. The specific preparation method is as follows:

[0212] The wafer was fed into the reaction chamber, which was then evacuated. The pressure was controlled at 1 mbar via a butterfly valve, and the temperature was maintained at 300°C. Yttrium hexafluoroacetylacetonate was introduced, with a carrier gas flow rate of 300 sccm for 5 seconds, followed by nitrogen purging for 15 seconds. Ozone was then introduced for 2 seconds at a flow rate of 1000 sccm, and finally, nitrogen purging was performed for 10 seconds. This completed one sub-cycle of yttrium fluoride deposition, with a deposition rate of [missing information]. During the deposition process, the source bottle of the yttrium hexafluoroacetylacetonate precursor was heated to 100°C and the source pipeline was heated to 120°C; the oxygen source and the delivery pipeline were at room temperature and did not require heating.

[0213] Repeat the above steps 600 times to obtain a 30nm YF3 thin film.

[0214] Experimental results show that the thickness uniformity of the YF3 film prepared in this embodiment is 2%.

[0215] The YF3 film prepared in this embodiment was characterized by XPS, as shown in Figure 5. As can be seen from the figure, the Y:F ratio of the YF3 film prepared in this embodiment is 1:2.8, and there are no C impurities in the film layer.

[0216] The YF3 film prepared in this embodiment was subjected to a WER (wet etch rate) test. Specifically, the thickness of the film was first measured, then the film was placed in a prepared etching solution, and the etching time was started. After a certain period of etching, the film was removed from the etching solution, cleaned, and dried. Finally, the thickness of the film at this point was measured. The corrosion rate was calculated by the ratio of the difference between the two thicknesses to the time. Following the above method, the film prepared in this embodiment was divided into five portions, and each portion was etched for 0.5h, 1h, 1.5h, 2h, and 2.5h respectively. The corrosion rate of each portion was calculated, and then the average value was calculated. The WER test results showed that the average corrosion rate of the YF3 film prepared in this embodiment was [value missing].

[0217] Example 10

[0218] A 30 nm thick YF3 thin film was deposited on the surface of a silicon wafer. The specific preparation method is as follows:

[0219] The wafer was fed into the reaction chamber, which was then evacuated. The pressure was controlled at 0.5 mbar via a butterfly valve, and the temperature was maintained at 200°C. Yttrium hexafluoroacetylacetonate was introduced, with a carrier gas flow rate of 200 sccm for 10 seconds, followed by nitrogen purging for 30 seconds. Ozone was then introduced for 8 seconds at a flow rate of 1500 sccm, and finally, nitrogen purging was repeated for 20 seconds. This completed one sub-cycle of yttrium fluoride deposition, with a deposition rate of [missing information]. During the deposition process, the source bottle of the yttrium hexafluoroacetylacetonate precursor was heated to 120°C and the source pipeline was heated to 160°C; the oxygen source and the delivery pipeline were at room temperature and did not require heating.

[0220] Repeat the above steps 600 times to obtain a 30nm YF3 thin film.

[0221] Example 11

[0222] A 30 nm thick YF3 thin film was deposited on the surface of a silicon wafer. The specific preparation method is as follows:

[0223] The wafer substrate was fed into the reaction chamber, which was then evacuated. The pressure was controlled to 1 mbar via a butterfly valve, and the temperature was maintained at 250°C. Yttrium triketoate (Y(THD)3) was introduced for 10 s at a carrier gas flow rate of 100 sccm, followed by argon gas for 30 s to purge residual chemical sources. Ozone was then introduced for 10 s at a carrier gas flow rate of 600 sccm, followed by argon gas for 30 s to purge residual chemical sources. Next, hexafluoroacetylacetone (Hhfac) was introduced for 10 s at a carrier gas flow rate of 200 sccm, followed by argon gas for 30 s to purge. Finally, ozone was introduced for 10 s at a carrier gas flow rate of 600 sccm, followed by argon gas for 30 s to purge. This completed one sub-cycle of yttrium fluoride deposition. During deposition, the Y(THD)3 source bottle was heated to 150°C, and the source pipeline was heated to 160°C. The fluorine source, oxygen source, and delivery pipeline were at room temperature and did not require heating.

[0224] Repeat the above steps 600 times to obtain a 30nm YF3 thin film.

[0225] Example 12

[0226] A 30 nm thick YF3 thin film was deposited on the surface of a silicon wafer. The specific preparation method is as follows:

[0227] The wafer substrate was fed into the reaction chamber, which was then evacuated. The pressure was controlled to 6 mbar via a butterfly valve, and the temperature was maintained at 400°C. Yttrium triketoate (Y(THD)3) was introduced for 15 s at a carrier gas flow rate of 300 sccm, followed by 50 s of argon to purge residual chemical sources. Ozone was then introduced for 10 s at a carrier gas flow rate of 500 sccm, followed by 20 s of argon to purge residual chemical sources. Next, hexafluoroacetylacetone (Hhfac) was introduced for 15 s at a carrier gas flow rate of 300 sccm, followed by 30 s of argon to purge. Finally, ozone was introduced for 10 s at a carrier gas flow rate of 600 sccm, followed by 20 s of argon to purge, thus completing one sub-cycle of yttrium fluoride deposition. During the deposition process, the Y(THD)3 source bottle was heated to 170°C, and the source pipeline was heated to 200°C. The fluorine source, oxygen source, and delivery pipeline were kept at room temperature and did not require heating.

[0228] Repeat the above steps 600 times to obtain a 30nm YF3 thin film.

[0229] Example 13

[0230] A 30 nm thick YF3 thin film was deposited on the surface of a silicon wafer. The specific preparation method is as follows:

[0231] The wafer substrate was fed into the reaction chamber, which was then evacuated. The pressure was controlled to 1 mbar via a butterfly valve, and the temperature was maintained at 250°C. Hexafluoroacetylacetone (Hhfac) was introduced for 10 seconds at a carrier gas flow rate of 100 sccm, followed by argon gas for 30 seconds to purge any remaining chemical sources. Ozone was then introduced for 10 seconds at a carrier gas flow rate of 600 sccm, followed by argon gas for 30 seconds to purge any remaining chemical sources. Next, yttrium triketoate (Y(Thd)3) ​​was introduced for 10 seconds at a carrier gas flow rate of 200 sccm, followed by argon gas for 30 seconds to purge. Finally, ozone was introduced for 10 seconds at a carrier gas flow rate of 600 sccm, followed by argon gas for 30 seconds to purge. This completed one sub-cycle of yttrium fluoride deposition. During the deposition process, the Y(Thd)3 source bottle was heated to 150°C, and the source pipeline was heated to 160°C. The fluorine source, oxygen source, and delivery pipeline were kept at room temperature and did not require heating.

[0232] Repeat the above steps 600 times to obtain a 30nm YF3 thin film.

[0233] Example 14

[0234] A 30 nm thick YF3 thin film was deposited on the surface of a silicon wafer. The specific preparation method is as follows:

[0235] The wafer substrate was fed into the reaction chamber, which was then evacuated. The pressure was controlled to 6 mbar via a butterfly valve, and the temperature was maintained at 400°C. Hexafluoroacetylacetone (Hhfac) was introduced for 15 seconds at a carrier gas flow rate of 300 sccm, followed by argon gas for 50 seconds to purge residual chemical sources. Ozone was then introduced for 10 seconds at a carrier gas flow rate of 500 sccm, followed by argon gas for 20 seconds to purge residual chemical sources. Next, yttrium triketoate (Y(Thd)3) ​​was introduced for 15 seconds at a carrier gas flow rate of 300 sccm, followed by argon gas for 30 seconds to purge. Finally, ozone was introduced for 10 seconds at a carrier gas flow rate of 600 sccm, followed by argon gas for 20 seconds to purge, thus completing one sub-cycle of yttrium fluoride deposition. During the deposition process, the Y(Thd)3 source bottle was heated to 170°C, and the source pipeline was heated to 200°C. The fluorine source, oxygen source, and delivery pipeline were kept at room temperature and did not require heating.

[0236] Repeat the above steps 600 times to obtain a 30nm YF3 thin film.

[0237] Comparative Example 2

[0238] The wafer was fed into the reaction chamber, which was then evacuated. The pressure was controlled at 1 mbar via a butterfly valve, and the temperature was maintained at 300°C. Yttrium triketoate (Y(THD)3) was introduced, with a carrier gas flow rate of 300 sccm for 5 seconds, followed by nitrogen purging for 15 seconds. Titanium tetrafluoride (TiF4) was then introduced for 2 seconds at a flow rate of 1000 sccm, and finally, nitrogen purging was performed for 10 seconds. This completed one sub-cycle of yttrium fluoride deposition, with a deposition rate of [missing value]. During the deposition process, the source bottle for yttrium triketoate was heated to 150°C and the source pipeline to 160°C; the source bottle for titanium tetrafluoride was heated to 170°C and the source pipeline to 180°C.

[0239] Repeat the above steps 600 times to obtain a 30nm YF3 thin film.

[0240] The comparison shows that in the process of preparing YF3 thin films, titanium tetrafluoride is corrosive, so the reaction chamber and pipeline need to be treated with anti-corrosion measures during deposition. However, corrosion still occurs in the poorly protected areas and on the substrate, affecting the uniformity of the film layer. In addition, the source bottle of titanium tetrafluoride is also heated, which increases the requirements and cost of the preparation equipment.

[0241] Comparative Example 3

[0242] A 30 nm thick YF3 thin film was deposited on the surface of a silicon wafer. The specific preparation method is as follows:

[0243] The wafer was fed into the reaction chamber, which was then evacuated. The pressure was controlled at 1 mbar via a butterfly valve, and the temperature was maintained at 300°C. Yttrium hexafluoroacetylacetonate was introduced, with a carrier gas flow rate of 50 sccm and an introduction time of 5 seconds. This was followed by nitrogen purging for 2 seconds, then ozone purging for 2 seconds at a flow rate of 1000 sccm, and finally nitrogen purging for 10 seconds. This completed one sub-cycle of yttrium fluoride deposition, with a deposition rate of [missing information]. During the deposition process, the source bottle of the yttrium hexafluoroacetylacetonate precursor was heated to 100°C and the source pipeline was heated to 120°C; the oxygen source and the delivery pipeline were at room temperature and did not require heating.

[0244] Repeat the above steps 600 times to obtain a 30nm YF3 thin film.

[0245] Experimental results show that the thickness uniformity of the YF3 film prepared in this comparative example is 6%.

[0246] Compared with the examples, in the preparation process of this comparative example, the amount of yttrium hexafluoroacetylacetonate introduced was too small and the purging time was too short. In some areas, the atomic layer of yttrium hexafluoroacetylacetonate was not uniformly adsorbed or deposited before the growth of the next layer, which affected the uniformity of the YF3 film and resulted in a lower uniformity of the YF3 film.

[0247] Comparative Example 4

[0248] A 30 nm thick YF3 thin film was deposited on the surface of a silicon wafer. The specific preparation method is as follows:

[0249] The wafer was fed into the reaction chamber, which was then evacuated. The pressure was controlled at 1 mbar via a butterfly valve, and the temperature was maintained at 300°C. Yttrium hexafluoroacetylacetonate was introduced, with a carrier gas flow rate of 800 sccm for 5 seconds, followed by nitrogen purging for 15 seconds. Ozone was then introduced for 2 seconds at a flow rate of 1000 sccm, and finally, nitrogen purging was repeated for 10 seconds. This completed one sub-cycle of yttrium fluoride deposition, with a deposition rate of [missing information]. During the deposition process, the source bottle of the yttrium hexafluoroacetylacetonate precursor was heated to 100°C and the source pipeline was heated to 120°C; the oxygen source and the delivery pipeline were at room temperature and did not require heating.

[0250] Repeat the above steps 600 times to obtain a 30nm YF3 thin film.

[0251] Experimental results show that the thickness uniformity of the YF3 film prepared in this comparative example is 9%.

[0252] Compared with the examples, in the preparation process of this comparative example, the amount of yttrium hexafluoroacetylacetonate introduced was too large and the purging time was too short. Some atomic layers of yttrium hexafluoroacetylacetonate were not fully purged before the deposition of the next atomic layer, which affected the uniformity of the YF3 film and resulted in lower uniformity of the YF3 film.

[0253] In the above embodiments of the present invention, two different precursor and oxygen source pathways are used as reactants in the preparation of yttrium fluoride thin films, and no toxic fluorine-containing gases are used, ensuring the safety of yttrium fluoride thin film deposition. The atomic layer deposition method is used to prepare the yttrium fluoride thin film, resulting in good film thickness uniformity and strong corrosion resistance. Furthermore, the yttrium fluoride thin film prepared by the present invention exhibits good structural stability as the film thickness decreases or the rate of reduction is slow under corrosive environments. Experimental results show that the thickness reduction of the yttrium fluoride thin film after 1 hour in a corrosive environment is only [missing information]. In Comparative Example 2, the preparation of yttrium fluoride thin films involved the use of toxic titanium tetrafluoride as a fluorine source, which required heating and corrosion protection of the pipes and reaction chambers. Even so, the risk of corrosion remained, thus increasing the requirements and costs of the preparation equipment. In Comparative Examples 3 and 4, the excessive or insufficient amount of precursor introduced, as well as the excessively short or long inert gas purging time, all affected the uniformity of the yttrium fluoride thin film thickness.

[0254] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a metal fluoride thin film, characterized in that, Metal precursors are subjected to atomic layer deposition with oxygen source to obtain metal fluoride films; The metal precursor is selected from hexafluoroacetylacetonate.

2. The preparation method according to claim 1, characterized in that, Includes the following steps: a) The coated sample is placed in the reaction chamber device, and after a period of time, a protective atmosphere is introduced to purge it. Then, an oxygen source is introduced to carry out the atomic layer deposition reaction. After the reaction, a protective atmosphere is introduced to purge it to complete one sub-cycle deposition. b) Repeat step a) to obtain a metal fluoride film.

3. The preparation 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, hafnium hexafluoroacetylacetonate, and yttrium hexafluoroacetylacetonate. The oxygen source includes ozone or oxygen plasma.

4. The method according to claim 2, characterized in that, The temperature of the reaction chamber device is 10–500°C, and the pressure is 0.2–10 mbar; The flow rate of the metal precursor is 100–500 sccm, and the time for introducing the metal precursor is 0.5–120 s. The oxygen source has a flow rate of 500–1500 sccm and an introduction time of 0.5–120 s.

5. The method according to claim 1 or 2, characterized in that, The deposition rate for atomic layer deposition reactions is 6. The preparation method according to claim 1, characterized in that, The preparation method is a method for preparing metal fluoride thin films by low-temperature ALD, including the following steps: Metal fluoride films were obtained by plasma-enhanced atomic layer deposition of metal precursors with oxygen plasma. The metal precursor is selected from hexafluoroacetylacetonate.

7. The method according to claim 6, characterized in that, Includes the following steps: A) Place the coated sample in the reaction chamber device, introduce the metal precursor for a period of time, then introduce a protective atmosphere to purge, then introduce an oxygen source, turn on the radio frequency to perform plasma-enhanced atomic layer deposition reaction, and after the reaction, introduce a protective atmosphere to purge to complete one sub-cycle deposition. B) Repeat step A) to obtain a metal fluoride film.

8. The method according to claim 6 or 7, characterized in that, The metal precursor is selected from at least one of magnesium hexafluoroacetylacetonate, lithium hexafluoroacetylacetonate, aluminum hexafluoroacetylacetonate, chromium hexafluoroacetylacetonate, or hafnium hexafluoroacetylacetonate.

9. The method according to claim 7, characterized in that, The temperature of the reaction chamber device is 10–400°C, and the pressure is 0.2–10 mbar.

10. The method according to claim 7, characterized in that, In 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 for introducing the metal precursor is 0.5-120 s, the heating temperature of the source bottle of the metal precursor is 80-150℃, and the heating temperature of the pipeline of the metal precursor is 90-200℃. The carrier gas is selected from inert gases, and the flow rate of the inert gas is 500 to 3000 sccm.

11. The method according to claim 7, characterized in that, In 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 500–1500 sccm, and the inlet time is 0.5–120 s; And / or, the power of the radio frequency is 100W to 10000W.

12. The method according to claim 7, 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.

13. The preparation method according to claim 1, characterized in that, The preparation method is a method for preparing yttrium fluoride thin films, comprising the following steps: S1) The substrate is placed in an atomic layer deposition apparatus, and a precursor containing both yttrium and fluorine is introduced. After the reaction, a film layer is formed on the surface of the substrate; the film layer is then purged. S2) An oxygen source is introduced into the atomic layer deposition apparatus to react with the film layer, and then the mixture is purged again to obtain a yttrium fluoride thin film.

14. The preparation method according to claim 13, characterized in that, Step S2) is followed by: The preparation cycle is repeated n times, with step S1) and step S2) as one preparation cycle, where n≥1; And / or, in step S1), before introducing the precursor containing both yttrium and fluorine, the method further includes: adjusting the temperature of the atomic layer deposition apparatus to 200–500°C and the pressure to 0.2–1.0 mbar; And / or, in step S1), the flow rate of the yttrium- and fluorine-containing precursor into the atomic layer deposition apparatus is 100–500 sccm, and the inlet time is 1–15 s; the heating temperature of the source bottle of the yttrium- and fluorine-containing precursor is 80–120°C, and the heating temperature of the source pipeline is 90–160°C.

15. The preparation method according to claim 13, characterized in that, The precursor containing both yttrium and fluorine includes yttrium hexafluoroacetylacetonate, and the oxygen source includes ozone or oxygen plasma.

16. The preparation method according to claim 13, characterized in that, In step S2), the flow rate of the oxygen source into the atomic layer deposition apparatus is 500-1500 sccm, and the introduction time is 1-15 s; And / or, in step S1), the gas used for purging is nitrogen or argon, and the purging time is 5 to 50 seconds; in step S2), the gas used for the second purging is nitrogen or argon, and the purging time is 5 to 50 seconds.

17. The preparation method according to claim 1, characterized in that, The preparation method is a method for preparing yttrium fluoride thin films, comprising the following steps: S1) The substrate is placed in an atomic layer deposition apparatus, a first precursor is introduced, and a film is formed on the surface of the substrate after reaction; the film is then subjected to a first purging. S2) An oxygen source is introduced into the atomic layer deposition apparatus to react with the film layer, and a second purging is performed after the reaction; S3) A second precursor is introduced into the atomic layer deposition apparatus and reacted with the film obtained in step S2) before a third purging is performed. S4) An oxygen source is introduced into the atomic layer deposition apparatus to react with the film obtained in step S3), and then a fourth purging is performed to obtain a yttrium fluoride thin film. The first precursor is selected from yttrium-containing precursors or fluorine-containing precursors, and correspondingly, the second precursor is selected from fluorine-containing precursors or yttrium-containing precursors.

18. The preparation method according to claim 17, characterized in that, Step S4) is followed by: The preparation cycle is repeated n times, with each step S1), S2), S3), and S4) as one preparation cycle, where n ≥ 1. And / or, in step S1), before introducing the first precursor, the method further includes: adjusting the temperature of the atomic layer deposition apparatus to 200-400°C and the pressure to 0.2-10 mbar; And / or, the flow rate of the fluorine-containing precursor or the yttrium-containing precursor into the atomic layer deposition apparatus is independently 100–500 sccm, and the introduction time is independently 1–15 s; the heating temperature of the source bottle of the yttrium-containing precursor is 120–170°C, and the heating temperature of the source pipeline is 150–200°C.

19. The preparation method according to claim 17, characterized in that, The yttrium-containing precursor includes yttrium triketoate, the fluorine-containing precursor includes hexafluoroacetylacetone, and the oxygen source includes ozone or oxygen plasma.

20. The preparation method according to claim 17, characterized in that, In step S2), the flow rate of the oxygen source into the atomic layer deposition apparatus is 500-1500 sccm, and the introduction time is 1-15 s; in step S4), the flow rate of the oxygen source into the atomic layer deposition apparatus is 500-1500 sccm, and the introduction time is 1-15 s. And / or, in step S1), the gas used for the first purging is argon or nitrogen, and the first purging time is 5 to 50 seconds; in step S2), the gas used for the second purging is argon or nitrogen, and the second purging time is 5 to 50 seconds; in step S3), the gas used for the third purging is argon or nitrogen, and the third purging time is 5 to 50 seconds; in step S4), the gas used for the fourth purging is argon or nitrogen, and the fourth purging time is 5 to 50 seconds.

21. The preparation method according to any one of claims 13 to 20, characterized in that, The substrate is a substrate that has undergone hydroxylation treatment.

22. A metal fluoride thin film, prepared by the preparation method according to any one of claims 1 to 20.

23. An antireflective membrane, characterized in that, The metal fluoride film prepared by the preparation method according to any one of claims 1 to 12.

24. An antireflective coating, characterized in that, The metal fluoride film prepared by the preparation method according to any one of claims 1 to 12.

25. The application of a metal fluoride thin film prepared by the preparation method according to any one of claims 1 to 12 in the field of optics.

26. The application of yttrium fluoride film as an anti-corrosion coating on the surface of structural components, wherein the yttrium fluoride film is the yttrium fluoride film prepared by the preparation method according to any one of claims 13 to 20.

27. A reaction chamber, comprising structural components, characterized in that, A yttrium fluoride film is formed on the surface of the structural component, wherein the yttrium fluoride film is a yttrium fluoride film prepared by the preparation method according to any one of claims 13 to 20.

28. The reaction chamber according to claim 27, characterized in that, The structural component is a spray structure.

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