Film-forming resin of krf photoresist, preparation method therefor, and use thereof

Abstract

The present application relates to the technical field of preparation of film-forming resins of photoresists, and discloses a film-forming resin of a KrF photoresist, a preparation method therefor, and a use thereof. The preparation method comprises the following steps: filtering a 4-acetoxystyrene monomer or a 4-acetoxystyrene monomer and another comonomer, then adding same into a dispersant, and adding an organic photocatalyst and a chain transfer agent for mixing to obtain a mixed solution; introducing an inert gas into the mixed solution, irradiating the mixed solution under the condition of visible light, and reacting to obtain a polymerization solution; and precipitating a polymer from the polymerization solution, performing drying, then adding an ammonia solution or a hydrazine hydrate solution, and upon completion of the reaction, removing residual metal ions to obtain a film-forming resin of a KrF photoresist having a molecular weight distribution of less than 1.2. The present application uses a photo-initiation mode, such that, on one hand, energy consumption during polymerization can be reduced, and the reaction conditions are mild; and on the other hand, a preparation process of a polymer can be well controlled in time and space, thereby ensuring batch-to-batch stability.

Description

A KrF photoresist film-forming resin, its preparation method and application

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 202411894298.5, filed on December 20, 2024, entitled "A KrF photoresist film-forming resin and its preparation method and application", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of photoresist film-forming resin preparation technology, and more specifically to a KrF photoresist film-forming resin, its preparation method and application. Background Technology

[0004] Photoresist, also known as photoresist, is a polymer material highly sensitive to light and radiation. Under irradiation or radiation from ultraviolet light, electron beams, excimer lasers, ion beams, X-rays, etc., this material undergoes photochemical changes, leading to a transformation in the solubility properties of its film before and after exposure. Photoresist typically consists of a film-forming resin, photosensitizer, inhibitor, solvent, and some additives. Among these, the film-forming resin is the most crucial component; different resin properties will have varying effects on the performance of the photoresist. KrF photoresist is a deep ultraviolet (DUV) photoresist with an exposure wavelength of 248nm. This type of photoresist has important applications in semiconductor manufacturing processes, especially in 3D NAND stacked architectures, where the demand for KrF photoresist increases significantly due to the increasing number of stacked layers. The film-forming resin of KrF photoresist is mainly poly(p-hydroxystyrene) polymer (PHS). The resin's preparation stability, molecular weight distribution, and residual metal ions are the main factors affecting its performance. A wide molecular weight distribution leads to differences in solution rates in different regions during photolithography, resulting in reduced resolution. Simultaneously, the resin's preparation stability directly affects the molecular weight of different batches of resin, ultimately impacting the stability of the photolithography process. PHS-type resins prepared using traditional free radical polymerization techniques generally have a molecular weight dispersity index (PDI) greater than 1.4, and the molecular weight is uncontrollable, which currently cannot meet the requirements for high-performance photoresists.

[0005] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0006] One or more embodiments of this application provide a method for preparing a KrF photoresist film-forming resin, comprising the following steps:

[0007] The 4-acetoxystyrene monomer or 4-acetoxystyrene monomer and other comonomers are filtered through neutral alumina particles, then added to the first dispersant, and then mixed with an organic photocatalyst and a chain transfer agent to obtain a mixed solution.

[0008] The mixed solution is evacuated and an inert gas is introduced into it to remove oxygen, at a pressure of 4-40 mW / cm². 2 The mixed solution was irradiated under visible light and reacted at 25-60°C for 10-72 h to obtain a polymer solution.

[0009] The polymer solution is dropped into a first undesirable solvent to precipitate, dried, and then dispersed in an organic solvent. Ammonia or hydrazine hydrate solution is added and stirring is continued for 3-24 hours. After the reaction is completed, the precipitate is washed and dried again to obtain KrF photoresist film-forming resin with a molecular weight distribution <1.2 and a molecular weight of 3000-100000.

[0010] In one or more embodiments, the organic solvent is a second dispersant.

[0011] In one or more embodiments, the method for preparing the KrF photoresist film-forming resin further includes the steps of removing protective groups and removing residual metal ions.

[0012] In one or more embodiments, the steps of removing the protecting group and removing residual metal ions include:

[0013] The deacetylated poly(p-hydroxystyrene) resin obtained by adding ammonia or hydrazine hydrate solution and reacting is added to a first undesirable solvent to precipitate and filter. The filtered solid is then added to a second dispersant for dispersion, followed by the addition of ion exchange resin and stirring. After stirring, the filtrate is filtered. Subsequently, the filtrate is dripped into the second undesirable solvent to precipitate and dried to obtain the KrF photoresist film-forming resin with a molecular weight distribution <1.2 and a molecular weight of 3000-100000.

[0014] In one or more embodiments, after the polymer solution is dropped into a first undesirable solvent to precipitate, the process further includes filtration and washing.

[0015] In one or more embodiments, the other comonomer is one or more of styrene, 2-acetoxystyrene, tert-butoxycarbonylstyrene, tert-butyl acrylate, tert-butyl methacrylate, and tert-butoxystyrene.

[0016] In one or more embodiments, the molar ratio of the other comonomer to the 4-acetoxystyrene monomer is 0.1-1:1.

[0017] In one or more embodiments, when the other comonomer is tert-butyl acrylate, the molar ratio of tert-butyl acrylate to 4-acetoxystyrene monomer is 0.3-1:1.

[0018] In one or more embodiments, the organic photocatalyst is one or more of eosin, fluorescein, phenothiazine, phenazine, cyanoaromatic hydrocarbons, 1,3-propanedithiol, 1,2-ethanedithiol, trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetramercaptoacetate, and pentaerythritol tetra-3-mercaptopropionate.

[0019] In one or more embodiments, the organic photocatalyst is eosin and 1,3-propanedithiol.

[0020] In one or more embodiments, the chain transfer agent is one or more of 4-cyano-4-[(dodecylthiocarbonyl)-thio]valerate, 2-(dodecyltrithiocarbonyl)-2-methylpropionic acid, 4-cyano-4-(thiobenzoyl)valerate, O-phenyl S-(1-phenylethyl)dithiocarbonate, O-ethyl S-(1-phenylethyl)dithiocarbonate, and methyl cyanomethyl (phenyl)aminodithiocarbamate.

[0021] In one or more embodiments, the molar ratio of the chain transfer agent to 4-acetoxystyrene monomer or 4-acetoxystyrene monomer and other comonomers is 1:20-600.

[0022] In one or more embodiments, the chain transfer agent is 4-cyano-4-[(dodecylthiocarbonyl)-thio]valeric acid and 2-(dodecyltrithiocarbonate)-2-methylpropionic acid.

[0023] In one or more embodiments, the first dispersant is one or more of tetrahydrofuran, toluene, xylene, ethylene diether, N,N-dimethylformamide, N,N-dimethylacetamide, ethyl acetate, anisole, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol methyl ether acetate, methyl ethyl ketone, methyl pentyl ketone, methyl isobutyl ketone, cyclohexanone, 1,4-dioxane, and dimethyl sulfoxide.

[0024] In one or more embodiments, the second dispersant is different from the first dispersant, and the second dispersant is one or more of 2-methyltetrahydrofuran, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, ethyl acetate, ethylene glycol monomethyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol methyl ether acetate, methyl ethyl ketone, methyl pentyl ketone, cyclohexanone, 1,4-dioxane, dimethyl sulfoxide, acetonitrile, acetone, and methanol.

[0025] In one or more embodiments, the first undesirable solvent is one of diethyl ether, petroleum ether, n-hexane, n-pentane, n-heptane, cyclohexane, methanol, ethanol, water, and isopropanol.

[0026] In one or more embodiments, the second undesirable solvent is different from the said undesirable solvent, and the second undesirable solvent is one or more of petroleum ether, n-hexane, n-pentane, n-heptane, cyclohexane, methyl tert-butyl ether, toluene, xylene, dichloromethane, methanol and isopropanol.

[0027] One or more embodiments of this application also claim protection for a KrF photoresist film-forming resin, which is prepared by any of the above-described methods for preparing KrF photoresist film-forming resins.

[0028] One or more embodiments of this application also claim protection for the application of a KrF photoresist film-forming resin, including using the above-described KrF photoresist film-forming resin to prepare KrF photoresist. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0030] Figure 1 is a flowchart of a method for preparing a KrF photoresist film-forming resin according to one or more embodiments of this application.

[0031] Figure 2 shows the results of number-average molecular weight and PDI tests on the KrF photoresist film-forming resin prepared in Example 2.

[0032] Figure 3 is a comparison of the number-average molecular weight and molecular weight distribution (PDI) test results of three batches of KrF photoresist film-forming resins produced using the method in Example 1. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0034] The use of the words “comprising” or “having” and any variations thereof in the specification, claims, and accompanying drawings of this application is intended to cover a non-exclusive inclusion, for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices.

[0035] For ease of understanding, the process of the embodiments of this application is described below. Please refer to Figure 1. The preparation method of KrF photoresist film-forming resin in the embodiments of this application includes:

[0036] S10. 4-Acetoxystyrene monomer or 4-acetoxystyrene monomer and other comonomers are filtered through neutral alumina particles to remove the polymerization inhibitor, and then added to the first dispersant. Organic photocatalyst and chain transfer agent are added and mixed to obtain a mixed solution.

[0037] In one or more embodiments, the 4-acetoxystyrene monomer, as the main building block of the polymer chain, can be formed into a long-chain polymer by covalent bonding alone, or it can be copolymerized with other comonomers to form a long-chain polymer. The monomer structure of the 4-acetoxystyrene is as follows: The neutral alumina particles, acting as a filter medium, primarily remove polymerization inhibitors from the monomer solution, ensuring the smooth progress of the polymerization reaction. The first dispersant helps monomers and other additives disperse better in the solution, preventing aggregation and precipitation. The organic photocatalyst is excited under light, transitioning from the ground state to an excited state, and then interacts with the chain transfer agent to control the RAFT (Reversible Addition-Fragmentation Chain Transfer) equilibrium. The chain transfer agent protects free radicals through chain transfer, keeping most free radicals in the polymerization system in a dormant state. Through a dynamic and reversible reaction, it switches between activation and dormancy, ensuring equal growth probabilities for each polymer chain segment, thereby controlling the polymer molecular weight and molecular weight distribution. In one or more embodiments, the main steps involve mixing monomers and adding catalysts and chain transfer agents, preparing for the subsequent polymerization reaction.

[0038] S20. Vacuum the mixed solution and introduce inert gas to remove oxygen from the mixed solution, at 4-40 mW / cm². 2 The mixed solution was irradiated under visible light and reacted at 25-60°C for 10-72 h to obtain a polymer solution.

[0039] In one or more embodiments, a vacuum is drawn and oxygen is removed from the mixed solution by introducing an inert gas to prevent oxygen from interfering with the polymerization reaction as a free radical scavenger. Visible light irradiation provides the light energy required for the polymerization reaction, activating the organic photocatalyst to generate free radicals and initiate the polymerization reaction. The reaction temperature is controlled at 25-60°C to promote collisions and reactions between monomers at a suitable temperature. In this step, the organic photocatalyst is activated under visible light irradiation, initiating the polymerization reaction between monomers. By selecting different chain transfer agents, the molecular weight and molecular weight distribution of the polymer can be precisely controlled, ensuring the resin performance meets requirements. In one or more embodiments, the wavelength of the visible light is related to the selection of the photoinitiator and the chain transfer agent. In some embodiments, visible light with a wavelength of 340-540 nm is used. In one or more embodiments, the inert gas can be nitrogen, argon, etc.

[0040] S30. The polymer solution is dropped into the first undesirable solvent to precipitate, dried, and then dispersed in an organic solvent. Ammonia or hydrazine hydrate solution is added and stirring is continued for 3-24 hours. After the reaction is completed, the polymer precipitate is washed and dried again to obtain KrF photoresist film-forming resin with a molecular weight distribution <1.2 and a molecular weight of 3000-100000.

[0041] In one or more embodiments, the polymer solution is dropwise into a first undesirable solvent, causing the polymer to precipitate from the solution, thus separating the polymer from the solvent. Residual solvent in the polymer is then removed by drying. Next, an organic solvent is used to help redisperse the polymer, facilitating subsequent reactions. Then, ammonia or hydrazine hydrate solution is added, and the acetoxy groups in the polymer are hydrolyzed under alkaline conditions to generate hydroxyl and acetate ions. After acidification, the polymer is precipitated again, filtered, washed, and dried to obtain a purified KrF photoresist film-forming resin with a molecular weight distribution <1.2. In one or more embodiments, by hydrolyzing acetoxy groups to hydroxyl groups, hydroxyl functional groups can be introduced, providing additional reactivity and functionality to the photoresist film-forming resin.

[0042] In one or more embodiments, the polymerization reaction is carried out using an organic photocatalyst and visible light irradiation, which has the advantages of mild reaction conditions and easy control; the use of chain transfer agents can effectively control the molecular weight and molecular weight distribution of the polymer, thereby stabilizing the performance of the resin.

[0043] In one or more embodiments, the photoresist film-forming resin has a PDI (molecular weight distribution) < 1.2, meaning that the molecular weight distribution of the resin is very narrow, i.e., the lengths of the individual molecular chains in the resin are very similar. This narrow molecular weight distribution photoresist film-forming resin has several significant advantages: First, resins with a narrow molecular weight distribution can form more uniform and smooth films during film formation because molecular chains with similar molecular weights are more likely to align neatly during film formation, reducing the generation of defects and porosity; second, a uniform and dense film can more accurately transfer the lithographic pattern, improving the resolution and precision of the lithography, which is crucial for fabricating patterns of microstructures, such as micron-level patterns in chip manufacturing; third, resins with a narrow molecular weight distribution generally have better chemical stability, resisting various chemical corrosions and reactions during the lithography process, thereby extending the lifespan and stability of the photoresist.

[0044] In one or more embodiments, the organic solvent is a second dispersant.

[0045] In one or more embodiments, the method for preparing the KrF photoresist film-forming resin of this application further includes the steps of removing protective groups and removing residual metal ions.

[0046] In one or more embodiments, the steps of removing the protecting group and removing residual metal ions include:

[0047] The deacetylated poly(p-hydroxystyrene) resin obtained by adding ammonia or hydrazine hydrate solution and reacting is added to a first undesirable solvent to precipitate and filter. The filtered solid is then added to a second dispersant for dispersion, followed by the addition of ion exchange resin and stirring. After stirring, the filtrate is filtered. Subsequently, the filtrate is dripped into the second undesirable solvent to precipitate and dried to obtain the KrF photoresist film-forming resin with a molecular weight distribution <1.2 and a molecular weight of 3000-100000.

[0048] In one or more embodiments, after the polymer solution is dropped into a first undesirable solvent to precipitate, the method for preparing the KrF photoresist film-forming resin of this application further includes the steps of filtration and washing.

[0049] In one or more embodiments, the other comonomers are one or more selected from styrene, 2-acetoxystyrene, tert-butoxycarbonylstyrene, tert-butyl acrylate, tert-butyl methacrylate, and tert-butoxystyrene. In one or more embodiments, styrene, as a basic chemical raw material, has a low deep ultraviolet light absorption rate. As a comonomer for preparing KrF photoresist film-forming resin, it helps improve certain specific properties of the resin, such as hardness and abrasion resistance. The tert-butoxycarbonylstyrene has high purity and low metal ion content, which can reduce the generation of by-products during polymerization and improve the yield of the target product. Simultaneously, its special structure helps improve the resolution of the photoresist and the quality of the lithographic pattern. The tert-butyl acrylate has good hydrophobicity and hydrolytic stability. Introducing tert-butyl acrylate into the photoresist resin can improve the resin's water resistance and durability. Furthermore, its good color development and weather resistance also help improve the overall performance of the photoresist. In addition, the addition of tert-butyl acrylate can also increase the cohesive energy density of the resin, thereby improving the durability of the polymer film and its protection of the substrate. In one or more embodiments, different types of comonomers can be selected to copolymerize with 4-acetoxystyrene monomers to generate KrF photoresist film-forming resin, depending on specific needs.

[0050] In one or more embodiments, the molar ratio of the other comonomers to the 4-acetoxystyrene monomer is 0.1-1:1. Specifically, the photoresist film-forming resin is a key material in photolithography, requiring good optical transparency, resistance to dry etching, high resolution, and suitable processability. An appropriate molar ratio between the other comonomers and the 4-acetoxystyrene monomer should ensure that the copolymer contains a sufficient number of p-hydroxystyrene units, which provide good optical transparency during photolithography, enabling the photoresist to accurately transmit light signals. In one or more embodiments, tert-butyl acrylate (TBBacrylate) is used as the comonomer, and the molar ratio of TBBacrylate to 4-acetoxystyrene monomer is 0.3-1:1. Since TBBacrylate can only provide p-hydroxystyrene units from 4-acetoxystyrene monomer during copolymerization, if the molar ratio of TBBacrylate to 4-acetoxystyrene monomer is too high, the number of p-hydroxystyrene units in the final copolymer may be insufficient, affecting optical transparency. If the molar ratio is too low, the copolymer may be too complex, also affecting the photolithography effect. Within this molar ratio range, the copolymer molecular chains can more easily form clear patterns during photolithography, thereby improving resolution. It also allows the copolymer to have good processing properties, such as appropriate melting point and flowability, facilitating the coating and processing of photoresist. In one or more embodiments, by precisely controlling the molar ratio of the comonomer to 4-acetoxystyrene monomer, the properties of the KrF photoresist film-forming resin can be finely controlled to meet the needs of different photolithography processes.

[0051] In one or more embodiments, the organic photocatalyst is one or more selected from eosin, fluorescein, phenothiazine, phenazine, cyanoaromatics, 1,3-propanedithiol, 1,2-ethanedithiol, trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetramercaptoacetate, and pentaerythritol tetra-3-mercaptopropionate. When using one or more of the above organic photocatalysts to catalyze the preparation of KrF photoresist film-forming resin, a suitable catalyst can be selected according to requirements and reaction conditions. These catalysts each have their own characteristics and advantages, and can work together to promote the polymerization reaction, improve reaction efficiency, and enhance resin performance. For example, in this embodiment, eosin and 1,3-propanedithiol are used together as organic photocatalysts. Eosin has high photosensitivity and can rapidly respond to light and initiate the polymerization reaction; while the other catalyst, 1,3-propanedithiol, has strong chemical stability and can exist stably during the reaction and play a catalytic role. When these two catalysts are used together, they can cooperate to promote the polymerization reaction, thereby improving reaction efficiency and resin performance.

[0052] In one or more embodiments, the chain transfer agent is one or more of 4-cyano-4-[(dodecylthiocarbonyl)-thio]valerate, 2-(dodecyltrithiocarbonyl)-2-methylpropionic acid, 4-cyano-4-(thiobenzoyl)valerate, O-phenyl S-(1-phenylethyl)dithiocarbonate, O-ethyl S-(1-phenylethyl)dithiocarbonate, and methyl cyanomethyl (phenyl)aminodithiocarbamate. In one or more embodiments, the 4-cyano-4-[(dodecylthiocarbonyl)-thio]pentanoic acid contains cyano and thiocarbonyl functional groups, exhibiting strong reactivity and chemical stability. During polymerization, it can effectively control the length and distribution of molecular chains, improving the precision of controlling the molecular weight and molecular weight distribution of the resin, thereby optimizing the resin's performance. The 2-(dodecyltrithiocarbonate)-2-methylpropionic acid contains trithiocarbonate and methylpropionic acid groups, possessing unique chain transfer capabilities and good thermal stability. During polymerization, it can efficiently transfer chain radicals while maintaining the resin's thermal stability. These chain transfer agents each have their own characteristics and advantages in catalyzing the preparation of KrF photoresist film-forming resins. By rationally selecting and combining these chain transfer agents, the molecular structure and properties of the resin can be precisely controlled, thereby meeting the specific requirements of different fields for photoresist film-forming resins. In one or more embodiments, the molar ratio of the chain transfer agent to the polymerizing monomer (i.e., 4-acetoxystyrene monomer or 4-acetoxystyrene monomer and other comonomers) is 1:20-600, but is not limited to this.

[0053] In one or more embodiments, 4-acetoxystyrene monomer and tert-butyl acrylate are filtered through neutral alumina particles, then added to a first dispersant, and mixed with an organic photocatalyst and a chain transfer agent to obtain a mixed solution. The organic photocatalyst is composed of eosin and 1,3-propanedithiol; the chain transfer agent is composed of 4-cyano-4-[(dodecylthiocarbonyl)-thio]valeric acid and 2-(dodecyltrithiocarbonate)-2-methylpropionic acid.

[0054] In one or more embodiments, tert-butyl acrylate (TBBacrylate) is selected as a comonomer to copolymerize with 4-acetoxystyrene monomer to prepare KrF photoresist film-forming resin. TBBacrylate exhibits good hydrophobicity and hydrolytic stability. Introducing TBBacrylate into the photoresist resin can improve its water resistance and durability. Simultaneously, its good color development and weather resistance also contribute to improving the overall performance of the photoresist. Furthermore, the addition of TBBacrylate can increase the cohesive energy density of the resin, thereby improving the durability of the polymer film and its protection of the substrate. In one or more embodiments, the molar ratio of TBBacrylate to 4-acetoxystyrene monomer is 0.1-1:1. Within this molar ratio range, the copolymer contains a sufficient number of p-hydroxystyrene units, enabling the photoresist to accurately transmit light signals. Furthermore, within this molar ratio range, the copolymer molecular chains can more easily form clear patterns during photolithography, thereby improving resolution. The copolymer also possesses good processing properties, such as an appropriate melting point and flowability, facilitating the coating and processing of the photoresist. In one or more embodiments, eosin and 1,3-propanedithiol are used together as organic photocatalysts. Eosin has high photosensitivity, enabling it to respond rapidly to light and initiate polymerization, while 1,3-propanedithiol exhibits strong chemical stability, remaining stable and catalytically active during the reaction. When these two catalysts are used together, they synergistically promote the polymerization reaction, thereby improving reaction efficiency and resin performance. In one or more embodiments, 4-cyano-4-[(dodecylthiocarbonyl)-thio]valeric acid and 2-(dodecyltrithiocarbonate)-2-methylpropionic acid are selected together as chain transfer agents. This enables efficient transfer of chain radicals during polymerization, reducing the degree of polymerization and effectively controlling the length and distribution of molecular chains. It also optimizes resin performance, maintains resin thermal stability, and helps improve the resolution and heat resistance of the photoresist.

[0055] In one or more embodiments, the first dispersant is one or more of tetrahydrofuran, toluene, xylene, ethylene diether, N,N-dimethylformamide, N,N-dimethylacetamide, ethyl acetate, anisole, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol methyl ether acetate, methyl ethyl ketone, methyl pentyl ketone, methyl isobutyl ketone, cyclohexanone, 1,4-dioxane, and dimethyl sulfoxide, but is not limited thereto.

[0056] In one or more embodiments, the second dispersant is different from the first dispersant, and the second dispersant is one or more of 2-methyltetrahydrofuran, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, ethyl acetate, ethylene glycol monomethyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol methyl ether acetate, methyl ethyl ketone, methyl pentyl ketone, cyclohexanone, 1,4-dioxane, dimethyl sulfoxide, acetonitrile, acetone, and methanol.

[0057] In one or more embodiments, the first undesirable solvent is one of, but not limited to, diethyl ether, petroleum ether, n-hexane, n-pentane, n-heptane, cyclohexane, methanol, ethanol, water, and isopropanol.

[0058] In one or more embodiments, the second undesirable solvent is different from the first undesirable solvent, and the second undesirable solvent is one or more of petroleum ether, n-hexane, n-pentane, n-heptane, cyclohexane, methyl tert-butyl ether, toluene, xylene, dichloromethane, methanol, and isopropanol.

[0059] In one or more embodiments, a KrF photoresist film-forming resin is also provided, which is prepared by the preparation method of the KrF photoresist film-forming resin described in this application.

[0060] In one or more embodiments, an application of a KrF photoresist film-forming resin is also provided, wherein the KrF photoresist film-forming resin described in this application is used to prepare KrF photoresist. In one or more embodiments, KrF photoresist is a photosensitive mixed liquid, mainly used in the photolithography process in semiconductor manufacturing. It can transfer the image on the photomask to the silicon chip, playing the role of sensing light and etching patterns. During the photolithography process, KrF photoresist is very sensitive to 248 nm ultraviolet light, thus accurately replicating the pattern on the photomask. The KrF photoresist film-forming resin prepared in this application has excellent optical properties and chemical stability, and can be widely used in 248 nm photoresist systems. Moreover, the KrF photoresist film-forming resin prepared in this application has a narrow molecular weight distribution <1.2, meaning that the molecular weight distribution of the resin is very narrow, that is, the length difference of each molecular chain in the resin is very small. This type of photoresist with a narrow molecular weight distribution offers several significant advantages: First, it allows for the formation of more uniform and smooth films because molecular chains with similar molecular weights are more likely to align themselves neatly during film formation, reducing defects and porosity. Furthermore, a uniform and dense film can more accurately transfer the lithographic pattern, improving resolution and precision, which is crucial for creating patterns of microstructures, such as micron-level patterns in chip manufacturing. Finally, resins with a narrow molecular weight distribution typically exhibit better chemical stability, resisting various chemical corrosions and reactions during the lithography process, thereby extending the photoresist's lifespan and stability.

[0061] Traditional free radical polymerization techniques produce PHS-type resin polymers with a molecular weight distribution (PDI) generally greater than 1.4, and the molecular weight is uncontrollable. As can be seen from the technical solution of this application, compared with existing technologies, the beneficial effects of this application are as follows:

[0062] This addresses the problem that existing technologies for preparing PHS-type resin polymers generally have a molecular weight distribution greater than 1.4 and an uncontrollable molecular weight, which fails to meet the requirements of high-performance photoresists.

[0063] Compared to traditional free radical polymerization, photo-controlled RAFT polymerization technology can better prepare KrF photoresist film-forming resins with a narrow molecular weight distribution (<1.2). Furthermore, due to the photoinitiation method, energy consumption during polymerization is reduced, and reaction conditions are milder. On the other hand, the polymer preparation process allows for excellent temporal and spatial control, enabling precise control of polymer molecular weight and ensuring batch-to-batch stability. Moreover, compared to anionic polymerization and ATRP, this application does not use metal ion catalysts, reducing the complexity of metal ion removal processes and ensuring low metal ion residues in the samples.

[0064] This application is more environmentally friendly, reducing pollution; improves the fidelity of lithographic patterns; simplifies process control, such as reducing sensitivity to fluctuations in process parameters; enhances storage stability; is more compatible with existing production line equipment; and facilitates multifunctional design.

[0065] The present application will be further explained and illustrated below through specific embodiments:

[0066] Example 1

[0067] A method for preparing a KrF photoresist film-forming resin, comprising the following steps:

[0068] 16.22 g of 4-acetoxystyrene monomer was filtered through neutral alumina particles, then added to 48.52 mL of cyclohexane, along with 0.058 g of eosin as a catalyst and 0.36 g of 4-cyano-4-[(dodecylthiocarbonyl)-thio]valerate as a chain transfer agent to obtain a mixed solution.

[0069] The mixed solution is evacuated and nitrogen gas is introduced into it to remove oxygen, at a pressure of 20 mW / cm². 2 The mixed solution was irradiated under visible light and reacted at 40°C for 24 hours to obtain a polymer solution.

[0070] The polymer solution was dropped into methanol to precipitate, dried, and then dispersed in methanol. Hydrazine hydrate solution was added and stirring was continued for 10 hours. After the reaction was completed, water was added to precipitate the polymer again, and the mixture was filtered. The obtained solid was added to N,N-dimethylformamide for dispersion, and then ion exchange resin was added and stirred. After stirring, the mixture was filtered to obtain a filtrate. Subsequently, the filtrate was dropped into n-hexane to precipitate, filtered, and dried to obtain a KrF photoresist film-forming resin with a molecular weight distribution of 1.10 and a molecular weight of 13480.

[0071] Example 2

[0072] A method for preparing a KrF photoresist film-forming resin, comprising the following steps:

[0073] Weigh 8.11 g of 4-acetoxystyrene monomer and 5.21 g of styrene monomer, filter through neutral alumina particles, add to 27.78 mL of tetrahydrofuran, then add 0.012 g of fluorescein as a catalyst and 0.26 g of 2-(dodecyltrithiocarbonate)-2-methylpropionic acid as a chain transfer agent to obtain a mixed solution;

[0074] The mixed solution is evacuated and nitrogen gas is introduced into it to remove oxygen, at a pressure of 5 mW / cm². 2 The mixed solution was irradiated under visible light and reacted at 25°C for 12 hours to obtain a polymer solution.

[0075] The polymer solution was dropped into petroleum ether to precipitate, filtered, dried, and then dispersed in propylene glycol methyl ether acetate. Ammonia was added and stirring was continued for 10 hours. After the reaction was completed, water was added to precipitate the polymer again, and the precipitate was filtered. The obtained solid was dispersed in 2-methyltetrahydrofuran, and then ion exchange resin was added and stirred. After stirring, the filtrate was obtained. Subsequently, the filtrate was dropped into n-heptane to precipitate, filtered, and dried to obtain KrF photoresist film-forming resin with a molecular weight distribution of 1.12 and a molecular weight of 15334.

[0076] Example 3

[0077] A method for preparing a KrF photoresist film-forming resin, comprising the following steps:

[0078] 16.22 g of 4-acetoxystyrene monomer and 7.69 g of tert-butyl acrylate monomer were filtered through neutral alumina particles and then added to 105 mL of tetrahydrofuran. 0.029 g of eosin and 0.004 g of 1,3-propanedithiol were added as catalysts, and 0.18 g of 4-cyano-4-[(dodecylthiocarbonyl)-thio]valeric acid and 0.08 g of 2-(dodecyltrithiocarbonate)-2-methylpropionic acid were added as chain transfer agents to obtain a mixed solution.

[0079] The mixed solution was evacuated and argon gas was introduced into it to remove oxygen, at a pressure of 30 mW / cm². 2 The mixed solution was irradiated with blue light (460 nm) and reacted at 25°C for 48 h to obtain a polymer solution;

[0080] The polymer solution was dropped into n-hexane to precipitate, filtered, dried, and then dispersed in 1,4-dioxane. Hydrazine hydrate was added and stirring was continued for 12 hours. After the reaction was completed, water was added again to precipitate the polymer, which was then filtered. The obtained solid was dispersed in tetrahydrofuran, and then ion exchange resin was added and stirred. After stirring, the filtrate was obtained. Subsequently, the filtrate was dropped into petroleum ether to precipitate, filtered, and dried to obtain a KrF photoresist film-forming resin with a molecular weight distribution of 1.04 and a molecular weight of 14050.

[0081] Test case

[0082] The number-average molecular weight and PDI of the KrF photoresist film-forming resins prepared in Examples 1-3 were measured, and the results are shown in Table 1 and Figures 2-3.

[0083] Table 1. Number-average molecular weight and PDI test results of KrF photoresist film-forming resin

[0084] As can be seen from the data in Table 1, the PDI of the KrF photoresist film-forming resins prepared in Examples 1-3 is all less than 1.2. This indicates that the resin prepared by the method of this application has a very narrow molecular weight distribution, that is, the lengths of the molecular chains in the resin are very similar. This narrow molecular weight distribution photoresist film-forming resin has several significant advantages: First, the narrow molecular weight distribution resin can form a more uniform and smooth film during film formation. This is because molecular chains with similar molecular weights are more likely to align themselves neatly during film formation, reducing the generation of defects and pores. Second, a uniform and dense film can more accurately transfer the photolithography pattern, improving the resolution and precision of the photolithography. This is crucial for manufacturing patterns of microstructures, such as micron-level patterns in chip manufacturing. Third, the narrow molecular weight distribution resin usually has better chemical stability and can resist various chemical corrosions and reactions during the photolithography process, thereby extending the service life and stability of the photoresist.

[0085] The data above also shows that in Example 3, tert-butyl acrylate was used as a comonomer, eosin and 1,3-propanedithiol were used as catalysts, and 4-cyano-4-[(dodecylthiocarbonyl)-thio]valeric acid and 2-(dodecyltrithiocarbonate)-2-methylpropionic acid were used as chain transfer agents. The final KrF photoresist film-forming resin had the lowest PDI, only 1.04, indicating that the length difference of each molecular chain in the resin in this example was the smallest, which enabled it to form a more uniform and smooth film during film formation, and thus had better performance as a photoresist film-forming resin.

[0086] Figure 2 shows the results of number-average molecular weight and PDI tests on the KrF photoresist film-forming resin prepared in Example 2. Figure 3 is a comparison of the number-average molecular weight and PDI tests on three batches of KrF photoresist film-forming resin prepared using the method in Example 1. As can be seen from the figures, the molecular weights of the three batches of KrF photoresist film-forming resin are relatively similar, and the PDI values ​​are all around 1.1. This indicates that by effectively controlling the time and space of the polymer preparation process, this application can ensure the batch-to-batch stability of the prepared KrF photoresist film-forming resin.

[0087] It should be understood that the application of this application is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims. Industrial applicability

[0088] The KrF photoresist film-forming resin prepared in this application has a very narrow molecular weight distribution, meaning that the lengths of the molecular chains in the resin are very similar. This narrow molecular weight distribution photoresist film-forming resin has several significant advantages: First, the narrow molecular weight distribution resin can form a more uniform and smooth film during film formation because molecular chains with similar molecular weights are more likely to align neatly during film formation, reducing the generation of defects and porosity; second, a uniform and dense film can more accurately transfer the photolithographic pattern, improving the resolution and precision of the photolithography, which is crucial for manufacturing microstructure patterns, such as micron-level patterns in chip manufacturing; third, resins with a narrow molecular weight distribution generally have better chemical stability, resisting various chemical corrosions and reactions during the photolithography process, thereby extending the lifespan and stability of the photoresist. This application uses photoinitiation, which on the one hand reduces energy consumption in the polymerization process and provides mild reaction conditions; on the other hand, it allows for excellent time and space control of the polymer preparation process, ensuring batch-to-batch stability.

Claims

1. A method for preparing a KrF photoresist film-forming resin, characterized in that, Including the following steps: The 4-acetoxystyrene monomer or 4-acetoxystyrene monomer and other comonomers are filtered through neutral alumina particles, then added to the first dispersant, and then mixed with an organic photocatalyst and a chain transfer agent to obtain a mixed solution. The mixed solution is vacuumized and inert gas is introduced into the mixed solution to remove oxygen in the mixed solution, the mixed solution is irradiated under 4-40 mW / cm 2 of visible light, and reacts for 10-72 h at 25-60 °C to obtain a polymerization solution; The polymer solution is dropped into a first undesirable solvent to precipitate, dried, and then dispersed in an organic solvent. Ammonia or hydrazine hydrate solution is added and stirring is continued for 3-24 hours. After the reaction is completed, the precipitate is washed and dried again to obtain KrF photoresist film-forming resin with a molecular weight distribution <1.2 and a molecular weight of 3000-100000.

2. The method for preparing the KrF photoresist film-forming resin according to claim 1, wherein, The organic solvent is the second dispersant.

3. The method for preparing the KrF photoresist film-forming resin according to claim 2 further includes the steps of removing protective groups and removing residual metal ions.

4. The method for preparing the KrF photoresist film-forming resin according to claim 3, characterized in that, The steps of removing the protecting groups and removing residual metal ions include: The deacetylated poly(p-hydroxystyrene) resin obtained by adding ammonia or hydrazine hydrate solution and reacting is added to a first undesirable solvent to precipitate and filter. The filtered solid is then added to a second dispersant for dispersion, followed by the addition of ion exchange resin and stirring. After stirring, the filtrate is filtered. Subsequently, the filtrate is dripped into the second undesirable solvent to precipitate and dried to obtain the KrF photoresist film-forming resin with a molecular weight distribution <1.2 and a molecular weight of 3000-100000.

5. The method for preparing a KrF photoresist film-forming resin according to any one of claims 1 to 4, characterized by, After the polymer solution is dropped into a first undesirable solvent to precipitate, the process also includes filtration and washing steps.

6. The method for preparing a KrF photoresist film forming resin according to any one of claims 1 to 5, characterized by, The other comonomers are one or more of styrene, 2-acetoxystyrene, tert-butoxycarbonylstyrene, tert-butyl acrylate, tert-butyl methacrylate, and tert-butoxystyrene.

7. The method for preparing a KrF photoresist film forming resin according to any one of claims 1 to 6, characterized by, The molar ratio of the other comonomers to the 4-acetoxystyrene monomer is 0.1-1:

1.

8. The method for preparing a KrF photoresist film forming resin according to claims 1 to 7, wherein When the other comonomer is tert-butyl acrylate, the molar ratio of tert-butyl acrylate to 4-acetoxystyrene monomer is 0.3-1:

1.

9. The method for preparing the KrF photoresist film-forming resin according to any one of claims 1-8, characterized in that, The organic photocatalyst is one or more of eosin, fluorescein, phenothiazine, phenazine, cyanoaromatic hydrocarbons, 1,3-propanedithiol, 1,2-ethanedithiol, trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetramercaptoacetate, and pentaerythritol tetra-3-mercaptopropionate.

10. The method for preparing the KrF photoresist film-forming resin according to claim 9, characterized in that, The organic photocatalyst is eosin and 1,3-propanedithiol.

11. The method for preparing the KrF photoresist film-forming resin according to any one of claims 1-10, characterized in that, The chain transfer agent is one or more of 4-cyano-4-[(dodecylthiocarbonyl)-thio]valerate, 2-(dodecyltrithiocarbonyl)-2-methylpropionic acid, 4-cyano-4-(thiobenzoyl)valerate, O-phenyl S-(1-phenylethyl)dithiocarbonate, O-ethyl S-(1-phenylethyl)dithiocarbonate, and methyl(phenyl)aminodithiocarbamate.

12. The method for preparing the KrF photoresist film-forming resin according to claim 11, characterized in that, The chain transfer agent is 4-cyano-4-[(dodecylthiocarbonyl)-thio]valeric acid and 2-(dodecyltrithiocarbonate)-2-methylpropionic acid.

13. The method for preparing the KrF photoresist film-forming resin according to any one of claims 1-12, characterized in that, The molar ratio of the chain transfer agent to 4-acetoxystyrene monomer or 4-acetoxystyrene monomer and other comonomers is 1:20-600.

14. The method for preparing the KrF photoresist film-forming resin according to any one of claims 1-13, characterized in that, The first dispersant is one or more of tetrahydrofuran, toluene, xylene, ethylene diether, N,N-dimethylformamide, N,N-dimethylacetamide, ethyl acetate, anisole, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol methyl ether acetate, methyl ethyl ketone, methyl pentyl ketone, methyl isobutyl ketone, cyclohexanone, 1,4-dioxane, and dimethyl sulfoxide.

15. The method for preparing the KrF photoresist film-forming resin according to claim 4, characterized in that, The second dispersant is different from the first dispersant. The second dispersant is one or more of 2-methyltetrahydrofuran, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, ethyl acetate, ethylene glycol monomethyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol methyl ether acetate, methyl ethyl ketone, methyl pentyl ketone, cyclohexanone, 1,4-dioxane, dimethyl sulfoxide, acetonitrile, acetone, and methanol.

16. The method for preparing the KrF photoresist film-forming resin according to any one of claims 1-15, characterized in that, The first undesirable solvent is one of diethyl ether, petroleum ether, n-hexane, n-pentane, n-heptane, cyclohexane, methanol, ethanol, water, and isopropanol.

17. The method for preparing the KrF photoresist film-forming resin according to claim 4, characterized in that, The second undesirable solvent is different from the first undesirable solvent. The second undesirable solvent is one or more of petroleum ether, n-hexane, n-pentane, n-heptane, cyclohexane, methyl tert-butyl ether, toluene, xylene, dichloromethane, methanol, and isopropanol.

18. A KrF photoresist film-forming resin, characterized in that, It is prepared by the method of any one of claims 1-17 for preparing KrF photoresist film-forming resin.

19. An application of a KrF photoresist film-forming resin, characterized in that, This includes using the KrF photoresist film-forming resin of claim 18 to prepare KrF photoresist.

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