Masking plate protection film and method for manufacturing the same

Abstract

The application provides a mask protection film and a preparation method thereof, and the mask protection film comprises amino-modified silica nanoparticles and an epoxy group-containing fluorinated acrylate polymer; the amino-modified silica nanoparticles and the epoxy group-containing fluorinated acrylate polymer form a crosslinked polymer film through a crosslinking reaction between the amino groups and the epoxy groups, so as to serve as the mask protection film. The application not only can improve the mechanical properties such as the elastic modulus and the creep resistance of the mask protection film, and reduce the stress deformation in the photoetching process; moreover, after crosslinking, the silica nanoparticles can still effectively expose active sites, and the excellent photocatalytic activity is reserved, the organic pollutants attached to the surface of the film can be degraded, the self-cleaning function of the film is endowed, so that the light transmittance of the film can be improved; and the scattering problem caused by the traditional physical blending of easy agglomeration can be overcome, and the optical uniformity and the light transmittance of the film can be greatly improved.

Description

Technical Field

[0001] This invention relates to the field of photolithography, and in particular to a protective film for a photomask and its preparation method. Background Technology

[0002] In semiconductor photolithography, the protective film of the photomask is a key component to ensure the accuracy of pattern transfer. Its core function is to prevent particulate contamination and mechanical damage to the photomask surface. With the continuous miniaturization of semiconductor process nodes, especially the widespread application of extreme ultraviolet (EUV) lithography technology, more stringent requirements have been placed on the performance of the protective film. The protective film not only needs to possess extremely high optical transparency, but also must meet requirements for high strength, high abrasion resistance, and long-term environmental stability in terms of mechanical properties.

[0003] Traditional photomask protective films are mostly made of polymer-based materials (such as fluorinated polyimide). While they possess good light transmittance, their mechanical strength is relatively low, making them prone to deformation or microcracks during frequent exposure-cleaning cycles. This leads to shortened lifespan and deterioration of optical performance. Furthermore, organic contaminants adhering to the photomask surface (such as photoresist residue and hydrocarbons from the environment) significantly reduce the transmittance of the protective film, affecting exposure uniformity and pattern fidelity, thereby reducing product yield.

[0004] To improve the mechanical properties and antifouling properties of traditional polymer films, existing technologies have attempted to introduce silica (SiO2) nanoparticles. However, current technologies typically incorporate SiO2 nanoparticles into the polymer matrix through physical blending. Due to the high surface energy and large specific surface area of ​​SiO2 nanoparticles, existing physical blending processes struggle to achieve uniform dispersion within the polymer matrix, leading to easy particle aggregation. This results in reduced optical uniformity of the protective film, failing to meet the stringent optical performance requirements of advanced photolithography processes. Therefore, there is an urgent need to develop a novel photomask protective film that combines high optical uniformity, excellent mechanical properties, and self-cleaning capabilities. Summary of the Invention

[0005] The purpose of this invention is to provide a mask protective film and its preparation method, so as to solve one or more of the problems existing in the prior art, such as poor mechanical properties of mask protective films, easy decrease in light transmittance due to surface organic contaminants, and low optical uniformity caused by the easy agglomeration of SiO2 nanoparticles when incorporated into the polymer matrix by physical blending.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a mask protective film comprising amino-modified silica nanoparticles and an epoxy-containing fluorinated acrylate polymer; wherein the amino-modified silica nanoparticles and the epoxy-containing fluorinated acrylate polymer form a cross-linked network polymer film through a cross-linking reaction between the amino and epoxy groups, serving as the mask protective film.

[0007] Optionally, the molar ratio of the epoxy group in the fluorinated acrylate polymer containing epoxy groups to the amino group in the amino-modified silica nanoparticles is 1:(1~3).

[0008] Optionally, the epoxy-containing fluorinated acrylate polymer includes any one of the following: perfluoroalkyl epoxy fluorinated acrylate polymers containing epoxy groups, perfluoropolyether epoxy acrylate polymers containing epoxy groups, and waterborne epoxy fluorinated acrylate polymers containing epoxy groups.

[0009] To achieve the above objectives, the present invention also provides a method for preparing a mask protective film as described in any of the preceding claims, comprising the following steps:

[0010] Provided are the amino-modified silica nanoparticles and the fluorinated acrylate polymer containing epoxy groups;

[0011] The amino-modified silica nanoparticles are mixed with the fluorinated acrylate polymer containing epoxy groups, and the amino and epoxy groups undergo a cross-linking reaction. After heating and curing, the protective film of the mask is obtained.

[0012] Optionally, the amino-modified silica nanoparticles are prepared by the following steps: preparing silica nanoparticles; and modifying the surface of the silica nanoparticles with an amino-containing silane coupling agent to obtain the amino-modified silica nanoparticles.

[0013] Optionally, the silica nanoparticles are prepared by the following steps: Ammonia solution, pure water, and tetraethoxysilane are mixed in a volume ratio of (14.4~20.8):(2.3~3.4):(0.9~1.3) to obtain a mixture; under magnetic stirring at 600 rpm~1000 rpm, tetraethoxysilane is added dropwise to the mixture at an injection rate of 2 mL / h~5 mL / h to carry out the reaction, resulting in a reaction solution; wherein the amount of tetraethoxysilane used is 1 to 3 times that of the amount of tetraethoxysilane used; the reaction solution is centrifuged, washed, and dried to obtain the silica nanoparticles.

[0014] Optionally, the surface modification of the silica nanoparticles using an amino-containing silane coupling agent to obtain the amino-modified silica nanoparticles includes: uniformly dispersing the silica nanoparticles in an ethanol solvent at a mass ratio of 1:(200~300), adding a second ammonia solution and an amino-containing silane coupling agent, and refluxing for 24 to 36 hours to obtain a reaction product; wherein the mass of the second ammonia solution added is 4 to 5 times the mass of the silica nanoparticles, and the mass of the amino-containing silane coupling agent added is 16 to 20 times the mass of the silica nanoparticles; and centrifuging and washing the reaction product with ethanol and pure water respectively to obtain the amino-modified silica nanoparticles.

[0015] Optionally, the amino-containing silane coupling agent includes any one of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and N-(β-aminoethyl)-γ-aminopropyltriethoxysilane.

[0016] Optionally, the epoxy-containing fluorinated acrylate polymer is prepared by the following steps: dissolving hexafluorobutyl methacrylate, glycidyl methacrylate, and an initiator fully in anhydrous tetrahydrofuran solvent, and after deoxygenation treatment, reacting at 70℃~80℃ for 12 hours~18 hours; wherein, the molar ratio of hexafluorobutyl methacrylate to glycidyl methacrylate is (6~7):(3~4); after the reaction is completed, hydroquinone is added to terminate the reaction, and the reaction solution is purified to obtain the epoxy-containing fluorinated acrylate polymer.

[0017] Optionally, the step of mixing the amino-modified silica nanoparticles with the epoxy-containing fluorinated acrylate polymer, utilizing the cross-linking reaction between the amino and epoxy groups, and then curing by heating to obtain the mask protective film includes: dissolving the epoxy-containing fluorinated acrylate polymer in tetrahydrofuran solvent; adding the amino-modified silica nanoparticles and adding triethylamine as a catalyst, utilizing the cross-linking reaction between the amino and epoxy groups to obtain a cross-linking reaction product; the molar ratio of the epoxy groups in the epoxy-containing fluorinated acrylate polymer, the amino groups in the amino-modified silica nanoparticles, and the triethylamine is 1:(1~3):0.1; spin-coating the cross-linking reaction product into a film, and then curing it by heating at 75℃~80℃ for 1 hour~1.5 hours to obtain the mask protective film.

[0018] Compared with the prior art, the mask protective film and its preparation method provided by the present invention have the following beneficial effects:

[0019] The photomask protective film provided by this invention comprises amino-modified silica nanoparticles and an epoxy-containing fluorinated acrylate polymer. The amino-modified silica nanoparticles and the epoxy-containing fluorinated acrylate polymer undergo a crosslinking reaction between the amino and epoxy groups to form a crosslinked network polymer film, which serves as the photomask protective film. Therefore, the photomask protective film provided by this invention utilizes amino-modified silica nanoparticles as crosslinking reaction sites to crosslink the epoxy-containing fluorinated acrylate polymer, forming a crosslinked network polymer film as the photomask protective film. This not only improves the elastic modulus and creep resistance of the photomask protective film and reduces stress deformation during photolithography, but also ensures that the crosslinked silica nanoparticles still effectively expose active sites, retaining excellent photocatalytic activity. This allows the film to degrade organic pollutants adhering to the film surface, endowing the film with self-cleaning function, thereby improving the film's transmittance. Furthermore, due to the cross-linking structure formed between amino-modified silica nanoparticles and epoxy-containing fluorinated acrylate polymers, the strong chemical bonding interaction enables the amino-modified silica nanoparticles to achieve molecular-level uniform dispersion within the epoxy-containing fluorinated acrylate polymers. This overcomes the scattering problem caused by easy agglomeration in traditional physical blending, thereby significantly improving the optical uniformity and transmittance of the film. Simultaneously, the cross-linking structure restricts the thermal motion of the polymer chains, reducing refractive index drift over long-term use and enhancing the optical stability of the film. Moreover, the mask protective film provided by this invention, by achieving synergy between mechanical reinforcement and self-cleaning function at the molecular level, helps extend the service life of the protective film and reduce maintenance costs.

[0020] Furthermore, the molar ratio of the epoxy groups in the fluorinated acrylate polymer containing epoxy groups to the amino groups in the amino-modified silica nanoparticles is 1:(1~3). Therefore, the mask protective film provided by this invention can control the crosslinking density by adjusting the molar ratio of the epoxy groups in the fluorinated acrylate polymer containing epoxy groups to the amino groups in the amino-modified silica nanoparticles, thereby adjusting the mechanical strength of the protective film.

[0021] Since the method for preparing the protective film of the mask provided by this invention and the protective film of the mask provided by this invention belong to the same inventive concept, the method for preparing the protective film of the mask provided by this invention has at least all the advantages of the protective film of the mask provided by this invention. For the advantages of the method for preparing the protective film of the mask provided by this invention, please refer to the relevant description of the beneficial effects of the protective film of the mask provided by this invention, which will not be repeated here. Attached Figure Description

[0022] Figure 1This is a schematic diagram of the crosslinking mechanism between amino-modified silica nanoparticles and fluorinated acrylate polymers containing epoxy groups, as provided in Embodiment 1 of the present invention.

[0023] Figure 2 This is a schematic diagram of the overall steps of a method for preparing a protective film for a photomask according to Embodiment 2 of the present invention;

[0024] Figure 3 This is a schematic diagram of the structure of amino-modified silica nanoparticles provided in Embodiment 2 of the present invention. Detailed Implementation

[0025] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, further illustrates the protective film for the photomask and its preparation method proposed in this invention. The advantages and features of this invention will become clearer from the following description. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, used only to facilitate and clarify the illustration of the embodiments of this invention. Please refer to the drawings to make the objectives, features, and advantages of this invention more apparent and understandable. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the implementation conditions of this invention. Any modifications to the structure, changes in proportions, or adjustments to the size, provided that the effects and objectives achieved by this invention are the same or similar, should still fall within the scope of the technical content disclosed in this invention. Specific design features of the invention disclosed herein, including, for example, specific dimensions, orientations, positions, and shapes, will be determined in part by the specific application and usage environment. Furthermore, in the embodiments described below, the same reference numerals are sometimes used across different drawings to denote the same parts or parts having the same function, omitting repeated descriptions.

[0026] Example 1

[0027] This embodiment provides a protective film for a photomask. For details, please refer to... Figure 1 , Figure 1 This is a schematic diagram illustrating the crosslinking mechanism between amino-modified silica nanoparticles and fluorinated acrylate polymers containing epoxy groups, as provided in this embodiment. From... Figure 1 It can be seen that the protective film of the mask includes amino-modified silica nanoparticles (i.e., Figure 1 The spheres in the text represent NH2-SiO2 nanoparticles and fluorinated acrylate polymers containing epoxy groups (i.e., Figure 1 (The lines in the image); the amino-modified silica nanoparticles and the epoxy-containing fluorinated acrylate polymer form a cross-linked network polymer film through a cross-linking reaction between the amino and epoxy groups, which serves as a protective film for the mask.

[0028] Therefore, the mask protective film provided in this embodiment utilizes amino-modified silica nanoparticles as crosslinking reaction sites to crosslink fluorinated acrylate polymers containing epoxy groups, forming a crosslinked network polymer film as a mask protective film. This not only improves the mechanical properties of the mask protective film, such as elastic modulus and creep resistance, and reduces stress deformation during photolithography, but also ensures that the crosslinked silica nanoparticles can still effectively expose active sites, retaining excellent photocatalytic activity. This allows them to degrade organic pollutants adhering to the film surface, endowing the film with self-cleaning function and thus improving the film's transmittance. Furthermore, because the amino-modified silica nanoparticles and the fluorinated acrylate polymers containing epoxy groups form a crosslinked structure, the strong chemical bonding interaction enables the amino-modified silica nanoparticles to achieve molecular-level uniform dispersion in the fluorinated acrylate polymers containing epoxy groups. This overcomes the scattering problem caused by easy agglomeration in traditional physical blending, thereby significantly improving the film's optical uniformity and transmittance. At the same time, the crosslinked structure restricts the thermal motion of the polymer chains, reducing refractive index drift under long-term use and improving the film's optical stability. Furthermore, the mask protective film provided in this embodiment achieves synergy between mechanical reinforcement and self-cleaning function at the molecular level, which helps to extend the service life of the protective film and reduce maintenance costs.

[0029] Preferably, in some embodiments, the molar ratio of the epoxy groups in the epoxy-containing fluorinated acrylate polymer to the amino groups in the amino-modified silica nanoparticles is 1:(1~3). Therefore, the crosslinking density can be controlled by adjusting the molar ratio of the epoxy groups in the epoxy-containing fluorinated acrylate polymer to the amino groups in the amino-modified silica nanoparticles, thereby adjusting the mechanical strength of the protective film.

[0030] Exemplary examples include, in some embodiments, the molar ratio of the epoxy groups in the epoxy-containing fluorinated acrylate polymer to the amino groups in the amino-modified silica nanoparticles may be 1:1; in other embodiments, the molar ratio may be 1:3; and in still other embodiments, the molar ratio may be 1:2.

[0031] It should be noted that the present invention does not impose excessive limitations on the specific type of the epoxy-containing fluorinated acrylate polymer. Exemplarily, in some embodiments, the epoxy-containing fluorinated acrylate polymer includes any one of the following: perfluoroalkyl epoxy fluorinated acrylate polymers containing epoxy groups, perfluoropolyether epoxy acrylate polymers containing epoxy groups, and aqueous epoxy fluorinated acrylate polymers containing epoxy groups.

[0032] Example 2

[0033] This embodiment provides a method for preparing a mask protective film as described in any of the above embodiments. Specifically, please refer to... Figure 2 , Figure 2 This is a schematic diagram illustrating the overall steps of the method for preparing the protective film for the mask provided in this embodiment. From... Figure 2 As can be seen, the preparation method includes the following steps:

[0034] S1000: Provides the amino-modified silica nanoparticles and the fluorinated acrylate polymer containing epoxy groups;

[0035] S2000: The amino-modified silica nanoparticles are mixed with the fluorinated acrylate polymer containing epoxy groups, and the amino and epoxy groups undergo a cross-linking reaction. After heating and curing, the protective film of the mask is obtained.

[0036] Since the method for preparing the protective film of the mask provided in this embodiment belongs to the same inventive concept as the protective film of the mask provided in any of the above embodiments, the method for preparing the protective film of the mask provided in this embodiment has at least all the advantages of the protective film of the mask provided in the above embodiments. For the advantages of the method for preparing the protective film of the mask provided in this embodiment, please refer to the relevant description of the beneficial effects of the protective film of the mask provided in the above embodiments, which will not be repeated here.

[0037] For example, please see Figure 3 , Figure 3 This is a schematic diagram of the structure of amino-modified silica nanoparticles provided in this embodiment. Figure 3 As shown, the sphere represents a silica nanoparticle with extended chemical bonds connecting amino groups. In some embodiments, the amino-modified silica nanoparticles can be prepared by the following steps: S1110: preparing silica nanoparticles; S1120: surface-modifying the silica nanoparticles with an amino-containing silane coupling agent to obtain the amino-modified silica nanoparticles.

[0038] For example, in step S1110, the silica nanoparticles can be synthesized using a modified Stobel method. Specifically, in some embodiments, the silica nanoparticles are prepared by the following steps: S1111: Ammonia water, pure water, and tetraethoxysilane are mixed in a volume ratio of (14.4~20.8):(2.3~3.4):(0.9~1.3) to obtain a mixture; S1112: Under magnetic stirring at 600 rpm~1000 rpm, tetraethoxysilane is added dropwise to the mixture at an injection rate of 2 ml / h~5 ml / h to react, and a reaction solution is obtained after the reaction; wherein the amount of tetraethoxysilane is 1 to 3 times that of the amount of tetraethoxysilane; S1113: The reaction solution is centrifuged, washed, and dried to obtain the silica nanoparticles.

[0039] It should be noted that in step S1113, the specific operation can be as follows: centrifuge and wash the reaction solution 3 to 5 times with ethanol solvent, and then dry it with a freeze dryer for 24 to 30 hours to obtain white powdered silica nanoparticles.

[0040] Further, in some embodiments, step S1120, which involves surface modification of the silica nanoparticles using an amino-containing silane coupling agent to obtain the amino-modified silica nanoparticles, includes: S1121: uniformly dispersing the silica nanoparticles in an ethanol solvent at a mass ratio of 1:(200~300), adding a second ammonia solution and an amino-containing silane coupling agent, and refluxing for 24 to 36 hours to obtain a reaction product; wherein the mass of the second ammonia solution added is 4 to 5 times the mass of the silica nanoparticles, and the mass of the amino-containing silane coupling agent added is 16 to 20 times the mass of the silica nanoparticles; S1122: centrifuging and washing the reaction product 3 to 5 times with ethanol and pure water respectively to obtain the amino-modified silica nanoparticles.

[0041] It should be noted that the first ammonia solution and the second ammonia solution have the same mass fraction. For example, in some embodiments, both the first ammonia solution and the second ammonia solution are ammonia solutions with a mass fraction of 28%.

[0042] Additionally, it should be noted that the first tetraethoxysilane and the second tetraethoxysilane refer to TEOS, and both have the same concentration.

[0043] Preferably, in step S1120, the amino-containing silane coupling agent used includes any one of 3-aminopropyltriethoxysilane (APTES), 3-aminopropyltrimethoxysilane (APTMS), and N-(β-aminoethyl)-γ-aminopropyltriethoxysilane (AEAPTES).

[0044] Exemplary, in some embodiments, in step S1000, the fluorinated acrylate polymer containing epoxy groups is prepared by the following steps: S1210: Hexafluorobutyl methacrylate (HFMA), glycidyl methacrylate (GMA), and an initiator (such as AIBN) are fully dissolved in anhydrous tetrahydrofuran solvent, and after deoxygenation treatment, the mixture is reacted at 70°C to 80°C for 12 to 18 hours; wherein, the molar ratio of hexafluorobutyl methacrylate to glycidyl methacrylate is (6 to 7): (3 to 4); S1220: After the reaction is completed, a small amount of hydroquinone is added to terminate the reaction, and the reaction solution is purified to obtain the fluorinated acrylate polymer containing epoxy groups.

[0045] It should be noted that in step S1210, the specific operation of deoxygenation can be: cooling with liquid nitrogen, evacuating, and circulating nitrogen gas 3 to 5 times; in step S1220, the specific operation of purifying the reaction solution can be: precipitating the reaction solution in a 50 ml mixed solvent of methanol and water for purification.

[0046] Exemplarily, in some embodiments, step S2000 specifically includes: S2100: dissolving the epoxy-containing fluorinated acrylate polymer in tetrahydrofuran solvent; S2200: adding the amino-modified silica nanoparticles and adding triethylamine as a catalyst, utilizing the crosslinking reaction between the amino and epoxy groups to obtain a crosslinking reaction product; the molar ratio of the epoxy groups in the epoxy-containing fluorinated acrylate polymer, the amino groups in the amino-modified silica nanoparticles, and the triethylamine is 1:(1~3):0.1; S2300: spin-coating the crosslinking reaction product into a film and then curing it at 75℃~80℃ for 1 hour~1.5 hours to obtain the mask protective film.

[0047] It should be noted that in step S2000, the crosslinking reaction between the epoxy-containing fluorinated acrylate polymer and the amino groups in the amino-modified silica nanoparticles is achieved through the ring-opening reaction of the epoxy groups.

[0048] In addition, it should be noted that during the preparation of the amino-modified silica nanoparticles, the epoxy-containing fluorinated acrylate polymer, and the mask protective film: the amino-modified silica nanoparticles were characterized using a nanoparticle size analyzer and a Zeta potential analyzer. By observing the increase in particle size and the change in Zeta potential, it was confirmed that the amino group had been successfully modified onto the surface of the silica nanoparticles. The structure of the epoxy-containing fluorinated acrylate polymer was characterized using proton nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy, confirming the presence and integrity of the main chain backbone, fluorinated side chains, and epoxy groups. The mechanical properties and crosslinking density of the mask protective film were characterized using a nanoindentation tester and dynamic mechanical analysis, confirming that the mask protective film has excellent mechanical strength.

[0049] To better understand the present invention, the preparation process of the mask protective film provided by the present invention will be described by way of example below.

[0050] First, amino-modified silica nanoparticles were prepared. Specifically, silica nanoparticles were first synthesized: 250 mL of ammonia (28% by mass), 40 mL of pure water, and 15.5 mL of TEOS were uniformly mixed in a 500 mL beaker to obtain a mixture; under magnetic stirring at 600 rpm, 31 mL of TEOS was added dropwise to the mixture at an injection rate of 2 mL / h to carry out the reaction, and the reaction solution was obtained after the reaction; the reaction solution was centrifuged and washed three times with ethanol solvent, and then dried using a freeze dryer for 24 hours to obtain white powdered silica nanoparticles. The surface of the silica nanoparticles was then modified: 0.1 g of silica nanoparticles were uniformly dispersed in 20 g of ethanol solvent, and 0.5 g of ammonia (28% by mass) and 2 g of amino-containing silane coupling agent APTES were added. After reflux for 24 hours, the reaction product was obtained; the reaction product was centrifuged and washed three times with ethanol and pure water respectively to obtain amino-modified silica nanoparticles.

[0051] Then, a fluorinated acrylate polymer containing epoxy groups was prepared. Specifically, in a Schlenk reaction tube, hexafluorobutyl methacrylate, glycidyl methacrylate, and initiator AIBN were fully dissolved in anhydrous tetrahydrofuran solvent, wherein the molar ratio of hexafluorobutyl methacrylate to glycidyl methacrylate was 7:3; after three cycles of "liquid nitrogen cooling-vacuuming-nitrogen purging", the reaction was stirred at 75°C for 12 hours; then, a small amount of hydroquinone was added to terminate the reaction, and the reaction solution was purified by precipitating in 50 mL of a mixed solvent of methanol and water to obtain the fluorinated acrylate polymer containing epoxy groups.

[0052] Next, a mask protective film was prepared using the amino-modified silica nanoparticles and epoxy-containing fluorinated acrylate polymers obtained above. Specifically: the epoxy-containing fluorinated acrylate polymers obtained above were dissolved in tetrahydrofuran solvent; the amino-modified silica nanoparticles obtained above were added according to the molar ratio of epoxy group:amino group:triethylamine 1:1:0.1, and triethylamine was added dropwise as a catalyst to utilize the crosslinking reaction between amino and epoxy groups to obtain a crosslinking reaction product; the crosslinking reaction product was spin-coated into a film and cured at 80°C for 1 hour to obtain a crosslinked network polymer film, which was used as a mask protective film.

[0053] In summary, the photomask protective film and its preparation method provided by the present invention have the following advantages: The photomask protective film provided by the present invention comprises amino-modified silica nanoparticles and fluorinated acrylate polymers containing epoxy groups; the amino-modified silica nanoparticles and the fluorinated acrylate polymers containing epoxy groups form a cross-linked network polymer film through a cross-linking reaction between the amino and epoxy groups, which serves as the photomask protective film. Therefore, the photomask protective film provided by the present invention utilizes amino-modified silica nanoparticles as cross-linking reaction sites to cross-link the fluorinated acrylate polymers containing epoxy groups, forming a cross-linked network polymer film as the photomask protective film. This not only improves the elastic modulus and creep resistance of the photomask protective film and reduces stress deformation during photolithography, but also, after cross-linking, the silica nanoparticles can still effectively expose active sites, retaining excellent photocatalytic activity, degrading organic pollutants attached to the film surface, endowing the film with self-cleaning function, thereby improving the film transmittance. Furthermore, due to the cross-linking structure formed between amino-modified silica nanoparticles and epoxy-containing fluorinated acrylate polymers, the strong chemical bonding interaction enables the amino-modified silica nanoparticles to achieve molecular-level uniform dispersion within the epoxy-containing fluorinated acrylate polymers. This overcomes the scattering problem caused by easy agglomeration in traditional physical blending, thereby significantly improving the optical uniformity and transmittance of the film. Simultaneously, the cross-linking structure restricts the thermal motion of the polymer chains, reducing refractive index drift over long-term use and enhancing the optical stability of the film. Moreover, the mask protective film provided by this invention, by achieving synergy between mechanical reinforcement and self-cleaning function at the molecular level, helps extend the service life of the protective film and reduce maintenance costs.

[0054] Furthermore, the molar ratio of the epoxy groups in the fluorinated acrylate polymer containing epoxy groups to the amino groups in the amino-modified silica nanoparticles is 1:(1~3). Therefore, the mask protective film provided by this invention can control the crosslinking density by adjusting the molar ratio of the epoxy groups in the fluorinated acrylate polymer containing epoxy groups to the amino groups in the amino-modified silica nanoparticles, thereby adjusting the mechanical strength of the protective film.

[0055] Since the method for preparing the protective film of the mask provided by this invention and the protective film of the mask provided by this invention belong to the same inventive concept, the method for preparing the protective film of the mask provided by this invention has at least all the advantages of the protective film of the mask provided by this invention. For the advantages of the method for preparing the protective film of the mask provided by this invention, please refer to the relevant description of the beneficial effects of the protective film of the mask provided by this invention, which will not be repeated here.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A protective film for a photomask, characterized in that, It includes amino-modified silica nanoparticles and fluorinated acrylate polymers containing epoxy groups; the amino-modified silica nanoparticles and the fluorinated acrylate polymers containing epoxy groups form a cross-linked network polymer film through a cross-linking reaction between the amino and epoxy groups, which serves as a protective film for the mask.

2. The protective film for the photomask according to claim 1, characterized in that, The molar ratio of the epoxy groups in the fluorinated acrylate polymer containing epoxy groups to the amino groups in the amino-modified silica nanoparticles is 1:(1~3).

3. The protective film for the photomask according to claim 1, characterized in that, The epoxy-containing fluorinated acrylate polymer includes any one of the following: perfluoroalkyl epoxy fluorinated acrylate polymers containing epoxy groups, perfluoropolyether epoxy acrylate polymers containing epoxy groups, and waterborne epoxy fluorinated acrylate polymers containing epoxy groups.

4. A method for preparing a mask protective film as described in any one of claims 1 to 3, characterized in that, Includes the following steps: Provided are the amino-modified silica nanoparticles and the fluorinated acrylate polymer containing epoxy groups; The amino-modified silica nanoparticles are mixed with the fluorinated acrylate polymer containing epoxy groups, and the amino and epoxy groups undergo a cross-linking reaction. After heating and curing, the protective film of the mask is obtained.

5. The method for preparing the protective film for the photomask according to claim 4, characterized in that, The amino-modified silica nanoparticles were prepared by the following steps: Preparation of silica nanoparticles; The surface of the silica nanoparticles was modified using an amino-containing silane coupling agent to obtain the amino-modified silica nanoparticles.

6. The method for preparing the protective film for a photomask according to claim 5, characterized in that, The silica nanoparticles were prepared by the following steps: A mixture of first ammonia water, pure water and first tetraethoxysilane was prepared according to a volume ratio of (14.4~20.8):(2.3~3.4):(0.9~1.3) to obtain a mixed solution. Under magnetic stirring conditions of 600 rpm to 1000 rpm, tetraethoxysilane was added dropwise to the mixture at an injection rate of 2 ml / h to 5 ml / h to carry out the reaction, and a reaction solution was obtained after the reaction; wherein the amount of tetraethoxysilane used was 1 to 3 times that of the amount of first tetraethoxysilane. The reaction solution was centrifuged, washed, and dried to obtain the silica nanoparticles.

7. The method for preparing the protective film for a photomask according to claim 5, characterized in that, The method of surface modification of the silica nanoparticles using an amino-containing silane coupling agent to obtain the amino-modified silica nanoparticles includes: The silica nanoparticles were uniformly dispersed in an ethanol solvent at a mass ratio of 1:(200~300), and a second ammonia solution and an amino-containing silane coupling agent were added and refluxed for 24 to 36 hours to obtain the reaction product; wherein the mass of the second ammonia solution added was 4 to 5 times the mass of the silica nanoparticles, and the mass of the amino-containing silane coupling agent added was 16 to 20 times the mass of the silica nanoparticles. The reaction product was centrifuged and washed with ethanol and pure water, respectively, to obtain the amino-modified silica nanoparticles.

8. The method for preparing the protective film for a photomask according to claim 5, characterized in that, The amino-containing silane coupling agent includes any one of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and N-(β-aminoethyl)-γ-aminopropyltriethoxysilane.

9. The method for preparing the protective film for a photomask according to claim 4, characterized in that, The fluorinated acrylate polymer containing epoxy groups is prepared by the following steps: Hexafluorobutyl methacrylate, glycidyl methacrylate, and an initiator are fully dissolved in anhydrous tetrahydrofuran solvent and, after deoxygenation treatment, reacted at 70℃~80℃ for 12 to 18 hours; wherein, the molar ratio of hexafluorobutyl methacrylate to glycidyl methacrylate is (6~7):(3~4). After the reaction was completed, hydroquinone was added to terminate the reaction, and the reaction solution was purified to obtain the fluorinated acrylate polymer containing epoxy groups.

10. The method for preparing the protective film for a photomask according to claim 4, characterized in that, The process involves mixing the amino-modified silica nanoparticles with the epoxy-containing fluorinated acrylate polymer, utilizing the crosslinking reaction between the amino and epoxy groups, and then subjecting the mixture to heat curing to obtain the protective film for the photomask, comprising: The fluorinated acrylate polymer containing epoxy groups was dissolved in tetrahydrofuran solvent; The amino-modified silica nanoparticles are added, and triethylamine is added dropwise as a catalyst to utilize the cross-linking reaction between the amino group and the epoxy group to obtain the cross-linking reaction product; the molar ratio of the epoxy group in the fluorinated acrylate polymer containing epoxy group, the amino group in the amino-modified silica nanoparticles, and the triethylamine is 1:(1~3):0.

1. After spin-coating the crosslinking reaction product into a film, it is cured by heating at 75℃~80℃ for 1 hour~1.5 hours to obtain the mask protective film.

Images