Modified phenolic resin, preparation method thereof and i-line chemical amplification photoresist composition

Abstract

The invention provides modified phenolic resin, a preparation method thereof and an i-line chemical amplification photoresist composition, and relates to the technical field of semiconductor manufacturing. The modified phenolic resin is formed by common protection of hydroxyl of phenolic resin by 1, 4-butanediol divinyl ether and ethyl vinyl ether. The modified phenolic resin is jointly modified by 1, 4-butanediol divinyl ether and ethyl vinyl ether, and a cross-linked network is constructed by utilizing bifunctional groups so as to remarkably improve the heat resistance and the etching resistance and solve the problems of pattern deformation and'edge cutting '; meanwhile, the reaction activity is regulated by utilizing a single functional group, and the crosslinking abrupt property is relieved to broaden an energy window. And through the synergistic effect of the two components, the material has excellent heat resistance and corrosion resistance, wide process window and high resolution, and meets the high-precision microelectronic manufacturing requirements.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor manufacturing, in particular to a modified phenolic resin, a preparation method thereof and an i-line chemical amplification photoresist composition. BACKGROUND

[0002] In the "front-end process" of semiconductor manufacturing, photoresist, as a key pattern transfer medium, needs to go through key links such as photoresist development, etching transfer and ion implantation doping, and its performance directly determines the precision of wafer patterns and the electrical performance of devices. Among them, i-line photoresist (exposure wavelength of 365 nm) has long supported the mass production of 8-inch wafer mature processes (such as power devices, CMOS image sensors, MEMS, etc.) due to its high process maturity, low equipment cost and other advantages, and is still an irreplaceable key material in fields such as automotive electronics and industrial control that have strict requirements for chip reliability. With the increasing demand for chip performance in downstream applications, chip structures are gradually upgrading to high-aspect-ratio patterns and multi-layer interconnection wiring, which puts higher technical requirements on photoresist materials.

[0003] However, traditional i-line photoresist usually uses linear phenolic resin as a film-forming resin. Such resins contain a large number of C-H bonds and hydroxyl groups in their molecular chains, which are extremely susceptible to oxidative decomposition in an oxygen plasma etching environment, and their etching rate often exceeds 50 nm / min. Since the etching selectivity ratio of photoresist to the underlying medium (such as SiO2) is usually low (less than 5:1), when etching medium patterns with a large depth is required, the film thickness of the photoresist must be significantly increased. An excessively thick photoresist film not only increases the difficulty of controlling coating uniformity, but also easily causes "edge cutting" phenomenon at the top of the pattern due to uneven plasma bombardment, thereby causing large line width deviation, making it difficult to meet the precise transfer requirements of fine patterns below 0.25 μm, and limiting its application in advanced processes.

[0004] In addition, in order to improve the heat resistance and etching resistance of the photoresist, the prior art attempts to modify the phenolic resin, for example, by introducing a bifunctional crosslinking agent (such as 1,4-butanediol divinyl ether). Although this bifunctional structure can enhance the network structure of the resin through crosslinking reaction and improve physical properties, due to its high reactivity and the burst nature of crosslinking reaction, it will cause the response interval of the photoresist to the exposure dose to be compressed, making the energy window (Exposure Latitude, EL) extremely narrow. In actual photoresist processes, an extremely narrow energy window means that the accuracy of the exposure equipment is extremely high, and even a slight deviation will cause pattern failure, greatly increasing the difficulty of process control and production cost.

[0005] In summary, the existing i-line photoresist technology faces multiple technical bottlenecks such as insufficient resolution, poor etching resistance, and narrow process window caused by single modification method when coping with high-precision and high-aspect-ratio chip manufacturing, and it is difficult to balance heat resistance, etching resistance and good photoetching process performance, so it is urgent to develop new material systems to solve the above problems.

[0006] In view of this, the present application is proposed. SUMMARY

[0007] The present application aims to provide a modified phenolic resin and a preparation method thereof, and an i-line chemical amplification photoresist composition. The modified phenolic resin is constructed with 1,4-butanediol divinyl ether to form a crosslinked network to improve heat resistance and etching resistance, and is combined with ethyl vinyl ether to adjust the reactivity to broaden the energy window, so as to have high resolution, excellent heat resistance and wide process adaptability.

[0008] In order to achieve the above-mentioned purpose of the present application, the following technical solutions are adopted: In a first aspect, the present application provides a modified phenolic resin, which is formed by the common protection of the hydroxyl group of the phenolic resin by 1,4-butanediol divinyl ether and ethyl vinyl ether.

[0009] In an optional embodiment, the modified phenolic resin comprises a first structural unit and a second structural unit. The structural formula of the first structural unit is: ; The structural formula of the second structural unit is: .

[0010] In an optional embodiment, the longitudinal average molecular weight of the modified phenolic resin is 28000-31000.

[0011] In a second aspect, the present application provides an i-line chemical amplification photoresist composition, which comprises the modified phenolic resin according to any one of the preceding embodiments, and a photoacid generator and an organic solvent.

[0012] In an optional embodiment, the photoacid generator comprises at least one of a sulfonyl fluoride photoacid generator, an oxime sulfonate photoacid generator and a triazine photoacid generator. Preferably, the photoacid generator is selected from at least one of the compounds with the structures shown in Formula 1, Formula 2 and Formula 3: Formula 1: ; Formula 2: ; Formula 3: .

[0013] In an optional embodiment, the organic solvent is propylene glycol monomethyl ether acetate; and / or, The i-line chemical amplification photoresist composition further comprises a leveling agent; the leveling agent is polymethylphenylsiloxane and / or polydimethylsiloxane; and / or, The i-line chemical amplification photoresist composition further comprises a sensitizer, and the sensitizer is TPPA; and / or, The i-line chemical amplification photoresist composition further comprises a base, and the base is selected from at least one of triisopropanolamine and triethylamine.

[0014] The i-line chemical amplification photoresist composition comprises the following components in parts by weight: modified phenolic resin 10-30 parts; photoacid generator 1-5 parts; photosensitizer 1-10 parts; base 1-5 parts; organic solvent 35-80 parts.

[0015] In a third aspect, the present application provides a preparation method of the modified phenolic resin according to any one of the preceding embodiments, comprising: dissolving phenolic resin, 1,4-butanediol divinyl ether and ethyl vinyl ether in a solvent, and adding an acid catalyst; reacting at a constant temperature of 75-85°C for 4-6 hours; After the reaction is completed, a precipitant is used for purification treatment to obtain the modified phenolic resin.

[0016] In some embodiments, the phenolic resin is obtained by condensation of m-cresol and p-cresol; Preferably, the molar ratio of the m-cresol and the p-cresol is 4:6.

[0017] In a fourth aspect, the present application provides a method for forming a photoresist pattern, comprising: coating the i-line chemical amplification photoresist composition according to any one of the preceding embodiments on a substrate to form a photoresist film; heating and baking the photoresist film; exposing the baked photoresist film to an i-line light source; developing the exposed photoresist film using a developing solution to form a photoresist pattern.

[0018] Compared with the prior art, the beneficial effects of the present application are: the modified phenolic resin realizes the synergistic optimization of the resin performance by introducing two specific groups of 1,4-butanediol divinyl ether and ethyl vinyl ether to protect the hydroxyl groups of the phenolic resin. Among them, 1,4-butanediol divinyl ether as a bifunctional compound has high reactivity and can form a cross-linked structure between resin molecules. This cross-linked network significantly enhances the rigidity and thermal stability of the resin skeleton, so that it is not easy to cause thermal deformation or oxidative decomposition in high-temperature baking and plasma etching environment, thereby greatly improving the heat resistance and etching resistance of the material, and solving the problems of pattern "edge cutting" and poor line width control caused by poor etching resistance of traditional linear phenolic resin.

[0019] At the same time, ethyl vinyl ether as a monofunctional compound plays a key regulating role in the system. Due to the multi-functional group characteristics of 1,4-butanediol divinyl ether, the cross-linking reaction presents burst and irreversible saturation characteristics, which is easy to cause the compression of the exposure energy response interval. Ethyl vinyl ether copolymerizes with the bifunctional group, dilutes the density of high-activity cross-linking sites, and alleviates the severity of cross-linking reaction, thereby effectively widening the energy window (EL) of the material. This dual-group synergistic modification strategy not only ensures that the material has excellent heat resistance and etching resistance, but also takes into account the wide process window and high resolution, meeting the stringent requirements of high-precision microelectronic manufacturing on the comprehensive performance of the material. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the specific embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0021] Figure 1 It is a flowchart of the preparation method of the modified phenolic resin in the embodiments of the present application. Figure 2 It is a resolution result column chart in the performance test of the present application. Figure 3 It is an energy window result column chart in the performance test of the present application. DETAILED DESCRIPTION

[0022] The embodiments of the present application will be described in detail below with reference to the examples, but those skilled in the art will understand that the following examples are only for illustrating the present application, and should not be regarded as limiting the scope of the present application. If the specific conditions are not specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are used. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be obtained by market purchase.

[0023] The modified phenolic resin provided in the embodiments of the present application is formed by co-protecting the hydroxyl groups of a phenolic resin with 1,4-butanediol divinyl ether and ethyl vinyl ether.

[0024] The molecular structure of the resin provided in the embodiments is formed by taking a basic phenolic resin as a skeleton and co-protecting the hydroxyl groups on the side chains thereof with two specific modifiers, 1,4-butanediol divinyl ether and ethyl vinyl ether.

[0025] The phenolic resin described above, as a basic polymer skeleton for modification reaction, is usually formed by polycondensation of a phenolic compound (such as phenol, cresol, etc.) with an aldehyde compound (such as formaldehyde), and has a large number of phenolic hydroxyl groups (-OH) distributed on the molecular chain. These hydroxyl groups are the reaction sites for chemical modification and are also the key groups determining the solubility of the resin (such as in an alkaline developer).

[0026] The 1,4-butanediol divinyl ether described above is a bifunctional compound, each end of the molecule containing one vinyl ether group (-O-CH=CH2). In the modification reaction, it can play the role of a "crosslinking agent". Its two vinyl ether groups can respectively undergo addition reaction with the hydroxyl groups on different phenolic resin molecular chains, thereby forming chemical bond connection (i.e. crosslinking structure) between the resin molecular chains.

[0027] The ethyl vinyl ether described above is a monofunctional compound, containing only one vinyl ether group in the molecule. In the modification reaction, it plays the role of a "capping agent" or "solubility inhibiting group". After it reacts with the hydroxyl groups on the phenolic resin, the hydrophilic hydroxyl groups are converted into hydrophobic groups, but without causing crosslinking between the molecular chains.

[0028] The co-protection formation described above means that the two modifiers described above simultaneously participate in the modification reaction of the hydroxyl groups of the phenolic resin. This means that in the final modified phenolic resin product, there are both crosslinking structure units derived from 1,4-butanediol divinyl ether and capping structure units derived from ethyl vinyl ether in the same molecular chain network.

[0029] The formation of the modified phenolic resin is based on the principle of addition reaction under acid catalysis (usually referred to as acetalization reaction). The phenolic hydroxyl groups on the phenolic resin undergo addition with the double bond (C=C) in the vinyl ether to form an acetal bond (-O-CH(CH3)-O-).

[0030] The crosslinking mechanism can be that the 1,4-butanediol divinyl ether, due to having two reactive centers, can connect two or more independent phenolic resin molecular chains together to form a three-dimensional network or long-chain branched structure. The formation of this structure increases the rigidity of the molecular chain and limits the thermal motion of the chain segments.

[0031] The adjustment mechanism is that ethyl vinyl ether adjusts the protection rate of hydroxyl groups in the resin (i.e. hydrophobicity) by occupying part of the hydroxyl sites, and at the same time, its introduction dilutes the density of the bifunctional crosslinking agent, avoiding the crosslinking network being too tight or the reaction being too violent.

[0032] Thanks to the crosslinking network structure introduced by 1,4-butanediol divinyl ether, the resin skeleton is more stable. In a high-temperature baking or plasma etching environment, this crosslinking structure can effectively resist thermal deformation and chemical degradation, thereby ensuring the integrity of the lithographic pattern and preventing the pattern from collapsing or the edge from being excessively etched; through the joint action of ethyl vinyl ether and 1,4-butanediol divinyl ether, the suddenness and uncontrollability of the crosslinking reaction caused by the use of a high-activity bifunctional crosslinking agent alone are avoided. The introduction of ethyl vinyl ether smoothes the response curve of the resin to the exposure energy, so that the photoresist can obtain a size-accurate pattern within a wider exposure dose range, reducing the stringent requirements for process control accuracy; under the premise of ensuring heat resistance, this resin structure modified by two groups still maintains good film-forming property and development contrast, which is helpful to realize high-precision resolution of fine patterns.

[0033] In some embodiments, the modified phenolic resin includes first structural units and second structural units. Specifically, the first structural units and the second structural units can be as shown in Table 1: Table 1, structural units in the modified phenolic resin

[0034] The above first structural unit shows that the phenolic resin skeleton (the benzene ring part in the brackets) is connected to a specific side chain group through its original hydroxyl site. The side chain structure contains an acetal bond connection (-O-CH(CH3)-O-), and extends a chain containing four carbon atoms (derived from 1,4-butanediol), and the end of the chain retains an unreacted vinyl ether group (-O-CH=CH2).

[0035] This is the state after the "one-sided" reaction of 1,4-butanediol divinyl ether with the phenolic resin, or represents a node in the crosslinking network. The terminal vinyl double bond is a potential reactive site that can further undergo crosslinking reaction in subsequent processes (such as pre-baking or post-exposure baking) to build a three-dimensional network.

[0036] The above second structural unit shows that the phenolic resin skeleton is connected to a shorter side chain group through its hydroxyl site. The side chain structure also contains an acetal bond connection, but its end is a simple ethyl group (-CH2CH3).

[0037] This is the product of the reaction between ethyl vinyl ether and phenolic resin. It has a stable end-capped structure and does not have the ability to crosslink further, mainly serving to protect the hydroxyl groups (inhibiting alkali solubility).

[0038] By defining the chemical formulas of these two structural units, the material composition of the modified resin was precisely determined. This confirmed that the resin did indeed contain grafted long-chain double-bonded groups with cross-linking potential (first structural unit) and short-chain alkyl groups that only serve a protective function (second structural unit).

[0039] Furthermore, the presence of the first structural unit provides the resin with the ability to form a cross-linked network, thereby endowing the material with rigidity and stability (heat resistance and etching resistance) under high temperature and etching environments; the presence of the second structural unit adjusts the overall reactivity density of the resin, preventing the material from becoming brittle or overly sensitive to process conditions due to excessively dense cross-linking points, thereby broadening the process operation window and optimizing the resolution.

[0040] In some embodiments, the longitudinal average molecular weight of the modified phenolic resin is 28,000 to 31,000. For example, it can be 28,000, 28,500, 29,000, 29,500, 29,800, 30,000, 30,200, 30,500, 30,800, 31,000, etc.

[0041] The longitudinal average molecular weight (28,000~31,000) mentioned above is a statistical indicator for measuring the average length and size of polymer molecular chains. Within this range, the degree of polymerization of resin molecules is moderate.

[0042] A molecular weight controlled above 28,000 ensures the resin has sufficient chain length to form a good film, avoiding defects or insufficient strength after film formation. A higher molecular weight also helps improve the material's heat distortion temperature (Tg). A molecular weight controlled below 31,000 prevents excessively large resin molecules from reducing solubility in the coating solvent or causing incomplete development (residue) during development, ensuring the photoresist has good process adaptability and resolution.

[0043] This application also provides an i-line chemical amplification photoresist composition, comprising: a modified phenolic resin as described in any of the foregoing embodiments, a photoacid generator, and an organic solvent.

[0044] The modified phenolic resin mentioned above serves as the main film-forming material for photoresist. Due to its special bifunctional modified structure, it not only determines the mechanical strength, heat resistance, and etching resistance of the photoresist film, but also forms the basis for generating photolithographic patterns (i.e., undergoing solubility changes through acid-catalyzed reactions).

[0045] The aforementioned photoacid-producing agent is the trigger for the "chemical amplification" mechanism. It is a photosensitive compound that decomposes upon exposure to i-rays (365 nm wavelength), releasing protonated acids. These acids act as catalysts, catalyzing the removal of protecting groups from the resin or the occurrence of cross-linking reactions during subsequent baking.

[0046] The aforementioned organic solvent serves as a carrier to dissolve the resin, PAG, and other additives, making the photoresist appear as a uniform liquid state, so as to form a film of uniform thickness on the substrate surface by spin coating or other methods.

[0047] This composition utilizes a chemical amplification mechanism. The trace amounts of acid generated during exposure catalyze a series of chain chemical reactions in the resin (such as deprotection or cross-linking), thereby significantly altering the resin's solubility in the exposed area. This mechanism greatly enhances the photoresist's light sensitivity (high sensitivity) and enables the acquisition of high-contrast patterns. By combining a specific modified phenolic resin (heat-resistant, wide window) with a suitable acid-generating agent, this composition addresses the shortcomings of traditional i-line photoresists—poor heat resistance and weak etching resistance—while ensuring high resolution and high sensitivity, making it suitable for high-precision chip manufacturing processes.

[0048] In some embodiments, the photoacid-producing agent includes at least one of sulfonyl fluoride photoacid-producing agents, oxime sulfonate photoacid-producing agents, and triazine photoacid-producing agents; Furthermore, the photoacid-producing agent is selected from at least one of the compounds with the structures shown in Formula 1, Formula 2 and Formula 3, as shown in Table 2: Table 2. Photoacid-producing agents and their corresponding structures

[0049] The above-mentioned sulfonyl fluorides (Formula 1) have special sulfonyl fluoride structural segments, which usually contain long fluorocarbon chains and aromatic ring structures (such as naphthalimide).

[0050] The above-mentioned oxime sulfonates (Formula 2) contain an oxime group (-C=NO-) and a sulfonyl group in their molecular structure, and are usually linked with heterocyclic structures such as thiophene.

[0051] The above-mentioned triazine class (Formula 3) has a triazine ring skeleton with trichloromethyl (-CCl3) and other groups attached to the ring.

[0052] Sulfonyl fluorides exhibit high acid production efficiency, releasing strong acids that effectively improve the efficiency of resin deprotection or crosslinking reactions, thereby enhancing sensitivity. Oxime sulfonates possess a wide spectral response range and high thermal stability, adaptable to various baking processes, and the generated acids are less prone to excessive diffusion, aiding in linewidth control. Triazine derivatives have extremely fast response speeds, typically producing strong protic acids, making them suitable for applications requiring rapid exposure.

[0053] By selecting or combining these photoacid generators with specific structures, the performance of photoresist can be flexibly adjusted to meet different chip manufacturing needs (such as pursuing speed or pursuing morphology).

[0054] In some embodiments, the i-line chemical amplification photoresist composition further includes a base selected from at least one of triisopropanolamine and triethylamine.

[0055] Among the above-mentioned bases (acid diffusion inhibitors), such as triisopropanolamine, its structural formula is: ; The triethylamine in the above-mentioned base has the following structural formula: .

[0056] Its function is to neutralize trace amounts of acid from unexposed areas or those that have diffused in, preventing excessive diffusion of acid in the resin that could lead to image blurring, thereby improving resolution and environmental stability.

[0057] In some embodiments, the organic solvent is propylene glycol monomethyl ether acetate.

[0058] The organic solvent mentioned above can be propylene glycol monomethyl ether acetate (PGMEA), which is a safe, environmentally friendly, and excellent solvent with strong dissolving power for phenolic resins, ensuring the uniformity of the coating film.

[0059] In some embodiments, the i-line chemical amplification photoresist composition further includes a leveling agent; the leveling agent is polymethylphenylsiloxane and / or polydimethylsiloxane.

[0060] The aforementioned leveling agents, such as polymethylphenylsiloxane, function to reduce the surface tension of the coating liquid, making the coating surface smoother and reducing defects such as pinholes.

[0061] In some embodiments, the i-line chemical amplification photoresist composition further includes a sensitizer, wherein the sensitizer is TPPA.

[0062] The aforementioned sensitizer (TPPA), namely 1,1,1-tris(4-hydroxyphenyl)ethane, has the following structural formula: Its function is to adjust the photosensitivity and solubility characteristics of the photoresist.

[0063] In some embodiments, the i-line chemical amplification photoresist composition comprises the following components in parts by weight: The modified phenolic resin is 10 to 30 parts; for example, it can be 10 parts, 12 parts, 15 parts, 18 parts, 20 parts, 22 parts, 25 parts, 28 parts, 30 parts, etc.

[0064] The photo-induced acid-producing agent is 1 to 5 parts; for example, it can be 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, etc.

[0065] The photosensitizer can be 1 to 10 parts; for example, it can be 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, etc.

[0066] The amount of alkali can be 1 to 5 parts; for example, it can be 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, etc.

[0067] Organic solvent: 35 to 80 parts. For example, it can be 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, 80 parts, etc.

[0068] refer to Figure 1 This application also provides a method for preparing modified phenolic resin as described in any of the foregoing embodiments, comprising: Step S1: Dissolve phenolic resin, 1,4-butanediol divinyl ether and ethyl vinyl ether in a solvent and add an acid catalyst.

[0069] In this step, the reaction raw materials—phenolic resin (basic framework), 1,4-butanediol divinyl ether (bifunctional modifier), and ethyl vinyl ether (monofunctional modifier)—are dissolved together in an appropriate amount of organic solvent to form a homogeneous liquid-phase reaction system, and then an acid catalyst is added.

[0070] This step aims to provide a homogeneous contact environment for reactants in solid-liquid or different liquid phases. The addition of an acid catalyst (such as a strong acid like p-toluenesulfonic acid) is to provide protons (H+). + This catalyzes the addition reaction between the double bond of the vinyl ether and the phenolic hydroxyl group.

[0071] Specifically, it can be carried out in a reactor equipped with a stirring device to ensure that all components are fully mixed.

[0072] Step S2: React at a constant temperature of 75℃~85℃ for 4~6 hours. The reaction temperature can be, for example, 75℃, 76℃, 78℃, 80℃, 82℃, 83℃, 84℃, 85℃, etc. The reaction time can be, for example, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, etc.

[0073] The temperature range of 75℃ to 85℃ is the suitable temperature range for this addition reaction. If the temperature is too low, the reaction rate will be slow and the conversion rate will be insufficient; if the temperature is too high, it may lead to an increase in side reactions or a darkening of the resin color.

[0074] The above time control of 4 to 6 hours ensures that the reaction reaches the expected equilibrium point or conversion rate, so that most of the hydroxyl groups are modified.

[0075] Under these conditions, the two vinyl ether modifiers competitively bind to the hydroxyl groups on the phenolic resin, generating a modified crude resin product with a cross-linked structure and a capped structure.

[0076] Step S3: After the reaction is complete, the resin is purified using a precipitant to obtain the modified phenolic resin.

[0077] After the above reaction is completed, the reaction solution is treated with a precipitant to precipitate the solid product, and then washed, dried and other operations are performed to finally obtain pure modified phenolic resin.

[0078] In addition to the target product, the reaction solution also contains unreacted raw materials, catalysts, and byproducts. By adding a poor solvent (a precipitant, such as n-hexane or n-heptane), the high-molecular-weight resin is precipitated out, while the small-molecule impurities remain in the solution, thereby achieving separation and purification.

[0079] The purification step removes acid catalysts and low molecular weight impurities that may affect the storage stability of the photoresist, ensuring the consistency of the resin's quality and performance.

[0080] This application also provides a method for preparing modified phenolic resin as described in the foregoing embodiments, wherein the phenolic resin is formed by the condensation polymerization of m-cresol and p-cresol.

[0081] The aforementioned phenolic resin is prepared by polycondensation of m-cresol and p-cresol. m-cresol, due to its three reactive sites (ortho- and para-positions) on its benzene ring, readily forms resins with high branching and large molecular weight after polycondensation, which is beneficial for improving photosensitivity. p-cresol, on the other hand, has only two reactive sites and primarily forms a linear structure, which is beneficial for improving film-forming properties and heat resistance.

[0082] Polycondensation using a mixture of these two specific isomers can balance the resin's dissolution rate, sensitivity, and heat resistance, resulting in resins with superior performance compared to resins prepared using only phenol or a single type of cresol.

[0083] Furthermore, the molar ratio of m-cresol to p-cresol is 4:6.

[0084] This is a precise formulation parameter. The ratio of 40% m-cresol to 60% p-cresol has been verified to achieve the best overall performance. At this ratio, the resin dissolves at a moderate rate in alkaline developer (neither too quickly to cause film damage nor too slowly to cause incomplete development), and the modified resin exhibits good mechanical strength and etching resistance. The "4:6" here indicates that m-cresol accounts for 40% of the total cresol molars, and p-cresol accounts for 60%. This is a specific preferred value.

[0085] This application also provides a method for forming a photolithographic pattern, including: Step S100: The i-line chemical amplification photoresist composition as described in any of the foregoing embodiments is coated on the substrate to form a photoresist film.

[0086] In this step, the liquid photoresist composition is uniformly coated onto the surface of the substrate to be processed (such as a silicon wafer, glass substrate, etc.). Specifically, a spin coating method can be used, in which the photoresist is dropped onto the center of the substrate, and the centrifugal force generated by rotation causes the photoresist to spread outwards and form a film.

[0087] For example, depending on the process requirements, the pre-spin coating speed can be set to 1000-1500 rpm and the main speed to 800-3000 rpm to control the film thickness uniformity, thereby forming a uniform wet photoresist film on the substrate.

[0088] In this step, the excellent leveling properties of this specific composition (e.g., with the addition of a leveling agent) can be utilized to obtain a thin film with no pinholes and uniform thickness, laying the foundation for subsequent high-precision pattern transfer.

[0089] Step S200: Heat and bake the photoresist film.

[0090] The process performed in this step is pre-baking or softening, which means heating the coated wet film.

[0091] Specifically, the substrate coated with photoresist can be placed in a hot plate or oven and heated. For example, the baking temperature is typically set between 90°C and 130°C.

[0092] Heating evaporates the organic solvent in the film, causing it to change from a liquid to a solid state and enhancing its adhesion to the substrate. For the modified phenolic resin described in this application, during this baking process, the bifunctional groups (1,4-butanediol divinyl ether derivative) on the resin side chains undergo a chemical reaction, forming a cross-linked structure between resin molecules.

[0093] This thermal cross-linked network formed during the pre-baking stage significantly improves the heat resistance and etching resistance of the photoresist film, enabling it to withstand subsequent harsh processing environments without deformation.

[0094] Step S300: Expose the baked photoresist film using an i-line light source.

[0095] In this step, light of a specific wavelength is used to illuminate the photoresist film through a mask, transferring the designed latent image onto the film.

[0096] Specifically, irradiation can be performed using an i-line light source (wavelength 365nm) irradiation machine (such as a proximity lithography machine or a stepper projection lithography machine). Parameters, for example, can be configured such that the exposure dose is controlled between 30-150 mJ / cm². 2 Within the range.

[0097] In the exposed areas, photoacid generators (PAGs) in the photoresist absorb light energy and decompose to produce acids. These acids act as catalysts, attacking the acetal protecting groups on the resin (i.e., the crosslinking and sealing points formed by vinyl ethers), causing them to decompose (deprotection reaction). In the unexposed areas, the resin remains crosslinked and hydrophobic, and no reaction occurs.

[0098] In this step, due to the catalytic effect of acid, only a small number of photons are needed to trigger a chain reaction, thereby greatly improving the sensitivity (photosensitivity) of the photoresist.

[0099] Step S400: The exposed photoresist film is developed using a developer to form a photolithographic pattern.

[0100] In this step, the photoresist in the exposed area is dissolved using a developer, thereby revealing the final relief pattern.

[0101] Specifically, the exposed substrate can be immersed in or sprayed with developing solution.

[0102] For example, a 2.38% aqueous solution of tetramethylammonium hydroxide (TMAH) can be used as the developer, with a development time of 60-100 seconds.

[0103] The resin in the exposed areas undergoes acid-catalyzed decomposition, changing from a hydrophobic cross-linked state to a hydrophilic state (restoring phenolic hydroxyl groups), and is easily soluble in alkaline developer and thus washed away. The resin in the unexposed areas retains its hydrophobic groups and cross-linked structure, making it less soluble in developer and thus preserved.

[0104] The final result is a high-resolution lithographic pattern with steep sidewalls and excellent heat and corrosion resistance, which can be used as a high-performance mask for subsequent etching or ion implantation processes.

[0105] The present invention will be further illustrated below with specific embodiments. However, it should be understood that these embodiments are merely for the purpose of more detailed illustration and should not be construed as limiting the present invention in any way.

[0106] I. Preparation of modified phenolic resin: Synthesis Example 1: Modified phenolic resin A1 (the resin in this application) (1) Accurately weigh 100g of phenolic resin (formed by condensation polymerization of m-cresol and p-cresol in a molar ratio of 0.4:0.6, with a longitudinal average molecular weight of 6900). (2) Add the above phenolic resin to a reaction vessel equipped with a stirrer, thermometer and reflux condenser, and then add 6g of 1,4-butanediol divinyl ether and 4g of ethyl vinyl ether. (3) Add an appropriate amount of propylene glycol methyl ether acetate (PGMEA) to the reaction vessel and mix the resin and vinyl ether thoroughly under stirring to form a homogeneous reaction system; (4) Add 0.1% by weight of methylbenzenesulfonic acid as a catalyst to the phenolic resin, turn on the heating device, raise the temperature of the reaction system to 75℃-85℃, and keep the reaction at this temperature for 4-6 hours, stirring continuously during the process; (5) After the reaction is complete, add 500 mL of n-heptane and stir for 10 minutes to precipitate. Then filter, wash the filter cake with n-heptane, and dry to obtain modified phenolic resin A1.

[0107] The longitudinal average molecular weight of the modified phenolic resin A1 was tested to be 29,800.

[0108] Synthesis Example 1-A: Modified phenolic resin A1-L (the resin in this application, verified at the lower end of the molecular weight range) The raw material ratio and operation steps were exactly the same as in Synthesis Example 1, except for the reaction control in step (4): the reaction temperature was adjusted to 75℃ and the reaction was kept at a constant temperature for 4 hours to control the degree of reaction. The longitudinal average molecular weight of the modified phenolic resin A1-L was tested to be 28200.

[0109] Synthesis Example 1-B: Modified Phenolic Resin A1-H (Resin in this application, molecular weight high-end verification) The raw material ratio and operation steps were exactly the same as in Synthesis Example 1, except for the reaction control in step (4): the reaction temperature was adjusted to 85℃ and the reaction was kept at a constant temperature for 6 hours to increase the degree of reaction. The longitudinal average molecular weight of the modified phenolic resin A1-H was tested to be 30800.

[0110] Synthesis Example 2: Modified phenolic resin A2 (comparative resin, single-group modified) The only difference from Synthesis Example 1 is the type and amount of the modifier: In step (2), 8g of 1,4-butanediol divinyl ether is added, but ethyl vinyl ether is not added.

[0111] The remaining steps and conditions are exactly the same as in Synthesis Example 1.

[0112] The longitudinal average molecular weight of the modified phenolic resin A2 was found to be 30,500 after testing.

[0113] II. Preparation of photoresist composition: According to the formulation ratio (parts by mass) shown in Table 3, the resin, photoacid generator (or photosensitizer), alkali, and leveling agent were dissolved in an organic solvent, mixed evenly, and shaken on a shaker for 48 hours. Finally, the mixture was filtered three times using a 0.2 μm filter membrane to obtain the photoresist compositions of each embodiment and comparative example.

[0114] Table 3. Photoresist components of each embodiment and comparative example (unit: parts by mass)

[0115] In Table 1, ordinary phenolic resin is the unmodified raw material phenolic resin used in Synthesis Example 1; PAG-1 is a sulfonyl fluoride photoacid-generating agent (structure reference Table 2); PAG-2 is an oxime sulfonate photoacid-generating agent (structure reference Table 2); PAG-3 is a triazine photoacid-generating agent (structure reference Table 2); PAC-1 is a photosensitizer, DNQ type, with the following structure: ; where R is selected from H and Its degree of substitution is 2.6. All leveling agents are polymethylphenylsiloxane.

[0116] Examples 1-A and 1-B were used to verify the effects of resins with different molecular weights, and the other components of the formulation remained the same as in Example 1.

[0117] III. Performance Testing: The prepared photoresist composition was patterned and tested according to the following process: (1) Coating: Spin coating is performed on an 8-inch silicon wafer substrate to form a uniform film layer.

[0118] (2) Baking (PAB): Baking at 90-130℃ to form a photoresist film with a thickness of 2.6μm.

[0119] (3) Exposure: Exposure is performed using an I-line proximity irradiator, with an exposure dose range of 30-150 mJ / cm². 2 .

[0120] (4) Development: Develop with 2.38% TMAH developer for 60-100 seconds.

[0121] IV. Test Results: The performance test results of each embodiment and comparative example are shown in Table 4, and Figure 2 and Figure 3 As shown.

[0122] Table 4. Performance Test Results

[0123] V. Results Analysis: Refer to the experimental results in Table 4, and Figure 2 and Figure 3 .

[0124] (1) Synergistic effect of two groups (Example 1 vs. Comparative Example 1): Example 1 employed the "dual-group (1,4-butanediol divinyl ether + ethyl vinyl ether) co-protection" strategy of this invention, while Comparative Example 1 only employed "mono-group (1,4-butanediol divinyl ether) protection." The results showed that although both exhibited excellent etching resistance and heat resistance (thanks to their cross-linking structure), Example 1 had a higher energy window (EL) of 23%, significantly better than Comparative Example 1's 15.6%. This confirms that the present invention, by introducing ethyl vinyl ether, effectively modulates the reactivity, mitigates the abruptness of the bifunctional cross-linking reaction, and thus significantly broadens the process window.

[0125] (2) Effects of different acid-producing agents (Examples 1-3): Examples 1-3 all used the modified resin A1 of the present invention, combined with different types of acid-producing agents. The results show that the resin system of the present invention has good versatility, achieving high resolution (0.9-1.0 μm) and a wide energy window when combined with different PAGs. In particular, combining it with a triazine acid-producing agent (Example 3) resulted in better sidewall perpendicularity.

[0126] (3) Comparison between the present invention and the conventional system (Example vs. Comparative Examples 2 and 3): Comparative Example 2 used a traditional DNQ photosensitizer system, whose energy window (20.7%) was lower than that of Example 1 of this invention (23%), and its resolution (1.4 μm) and heat resistance were significantly inferior to those of this invention. This indicates that the traditional physical dissolution inhibition mechanism (DNQ system) is not only limited in resolution when dealing with high-precision pattern manufacturing, but its process window also cannot reach the level of the bi-group chemical amplification system of this invention. Comparative Example 3 used ordinary unmodified resin, which completely failed to meet the photolithography requirements. In summary, this invention achieves a comprehensive surpassing of existing technologies in core indicators such as resolution, energy window, and heat resistance.

[0127] (4) Effect of resin molecular weight (Example 1 vs Example 1-A vs Example 1-B): Comparative test results from Example 1 (Mw=29800), Example 1-A (Mw=28200), and Example 1-B (Mw=30800) show that, within the molecular weight range (28000~31000) defined in this invention, the modified phenolic resin maintains excellent resolution (0.9μm), energy window (>22%), and heat and corrosion resistance. This indicates that the resin within this molecular weight range has good film-forming properties and process adaptability, and can stably achieve the technical effects of this invention.

[0128] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A modified phenol-formaldehyde resin, characterized by, The modified phenolic resin is formed by co-protection of hydroxyl groups of a phenolic resin by 1,4-butanediol divinyl ether and ethyl vinyl ether.

2. The modified phenol-formaldehyde resin according to claim 1, wherein The modified phenolic resin comprises a first structural unit and a second structural unit. In the formula, the structural formula of the first structural unit is: ; The structural formula of the second structural unit is: .

3. The modified phenol-formaldehyde resin of claim 1, wherein the formaldehyde is present in an amount of 0.1 to 0.5 moles per mole of phenol. The modified phenolic resin has a longitudinal average molecular weight of 28000-31000.

4. A type of i-line chemical amplification photoresist composition, characterized in that, Comprising: The modified phenolic resin according to any one of claims 1-3, and a photoacid generator and an organic solvent.

5. The i-line chemical amplification photoresist composition as described in claim 4, characterized in that, The photoacid generator comprises at least one of a sulfonyl fluoride photoacid generator, an oxime sulfonate photoacid generator, and a triazine photoacid generator; Preferably, the photoacid generator is selected from at least one of compounds having structures shown in Formula 1, Formula 2, and Formula 3: Formula 1: ; Formula 2: ; Formula 3: .

6. The i-line chemically amplified photoresist composition of claim 4 wherein, The organic solvent is propylene glycol monomethyl ether acetate; and / or, The i-line chemical amplification photoresist composition further comprises a leveling agent; the leveling agent is polymethylphenylsiloxane and / or polydimethylsiloxane; and / or, The i-line chemical amplification photoresist composition further comprises a sensitizer, and the sensitizer is TPPA; and / or, The i-line chemical amplification photoresist composition further comprises a base, and the base is selected from at least one of triisopropanolamine and triethylamine.

7. The i-line chemical amplification photoresist composition as described in claim 4, characterized in that, The i-line chemical amplification photoresist composition comprises the following components in parts by weight: Modified phenolic resin 10-30 parts; Photoacid generator 1-5 parts; Photosensitizer 1-10 parts; Base 1-5 parts; Organic solvent 35-80 parts.

8. A method for producing a modified phenol-formaldehyde resin as claimed in any one of claims 1 to 3, characterized in that, Comprising: Dissolving phenolic resin, 1,4-butanediol divinyl ether, and ethyl vinyl ether in a solvent, and adding an acid catalyst; Constant temperature reaction at 75-85°C for 4-6 hours; After the reaction is completed, purification treatment is performed using a precipitant to obtain the modified phenolic resin.

9. The method for preparing the modified phenolic resin as described in claim 8, characterized in that, The phenolic resin is formed by condensation of m-cresol and p-cresol; Preferably, the molar ratio of the m-cresol and the p-cresol is 4:

6.

10. A method of forming a lithographic pattern, characterized by, Comprising: Coating the i-line chemical amplification photoresist composition according to any one of claims 4-7 on a substrate to form a photoresist film; Performing heat baking on the photoresist film; Exposing the baked photoresist film to an i-line light source; Developing the exposed photoresist film using a developing solution to form a photoetching pattern.

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