A positive photoresist and a preparation method thereof

Abstract

The application belongs to the technical field of photoresist materials, and particularly relates to a positive photoresist and a preparation method thereof. The positive photoresist comprises the following components in parts by weight: phenolic resin 100 parts, diazonium naphthoquinone compound 30-45 parts, additive 3-5 parts, and solvent 250-350 parts; the phenolic resin is prepared by condensation polymerization of phenolic monomers and aldehyde monomers in a molar ratio of 1:(0.75-0.85); the phenolic monomers comprise 3-methylphenol, 4-methylphenol and 2,5-dimethylphenol in a molar ratio of (5-6):(5-7):(1-2). The positive photoresist has improved difference in dissolution rate between the exposed area and the unexposed area, can meet the comprehensive requirements of high resolution, wide process window and low defect rate for i-line photoetching process, and has good industrial application prospect.

Description

Technical Field

[0001] This application belongs to the field of photoresist materials technology, specifically relating to a positive photoresist and its preparation method. Background Technology

[0002] Positive photoresist is a key material for transferring fine patterns in the manufacturing of integrated circuits and discrete semiconductor devices. Its working principle is based on the difference in solubility between exposed and unexposed areas in an alkaline developer. After exposure, the exposed areas become soluble, while the unexposed areas remain insoluble. After development, a pattern identical to the photomask is obtained. Finished photoresist typically consists of film-forming resin, photosensitizer, solvent, and additives. These components collectively determine the core properties of the photoresist, such as coating uniformity, photosensitivity, development contrast, resolution, adhesion to the substrate, and residual film yield. Positive photoresist dominates semiconductor manufacturing, accounting for over 80% of total photoresist usage, and is widely used in micro / nano patterning in large-scale integrated circuits, power devices, MEMS sensors, flat panel displays, and advanced packaging.

[0003] Under traditional exposure light sources such as i-lines, the light intensity exhibits a longitudinal gradient distribution along the film thickness direction, and the photon concentration gradually decreases along the film depth direction. This leads to differences in the degree of photochemical reaction between the surface and the bottom layers of the film, thus limiting the improvement of resolution. Existing positive photoresists often face the problem of insufficient depth of focus when achieving high-resolution patterns. Slight fluctuations in exposure dosage and focusing conditions can cause significant changes in the linewidth of the pattern, severely restricting the stability of mass production processes and product yield. How to obtain a sufficiently wide depth of focus while ensuring high resolution, so as to achieve a good balance in terms of coating uniformity, photosensitivity, and development contrast, has become an urgent technical challenge to be solved in the field of positive photoresists. Summary of the Invention

[0004] To improve the problem of insufficient resolution of positive photoresist, this application provides a positive photoresist and its preparation method.

[0005] In a first aspect, this application provides a positive photoresist, employing the following technical solution: A positive photoresist comprises the following raw materials in parts by weight: 100 parts of phenolic resin, 30-45 parts of diazonium naphthoquinone compound, 3-5 parts of additives, and 250-350 parts of solvent; wherein the phenolic resin is prepared by polycondensation reaction of phenolic monomers and aldehyde monomers in a molar ratio of 1:(0.75-0.85); wherein the phenolic monomers comprise 3-methylphenol:4-methylphenol:2,5-dimethylphenol in a mass ratio of (5-6):(5-7):(1-2).

[0006] Preferably, the aldehyde monomer is one or more of formaldehyde, 2,4-dimethylbenzaldehyde, 2,5-dimethylbenzaldehyde, 4-isopropylbenzaldehyde, and 4-formylbenzaldehyde.

[0007] More preferably, the aldehyde monomer is formaldehyde.

[0008] This application utilizes a specific combination of phenolic monomers and aldehyde monomers to form a phenolic resin, which serves as the film-forming framework for a photoresist. Combined with a diazonaphthoquinone photosensitizer and polyphenol additives, this significantly enhances the contrast in dissolution rates between exposed and unexposed areas during development, thereby achieving higher resolution. The phenolic resin is copolymerized from 3-methylphenol, 4-methylphenol, and 2,5-dimethylphenol in a specific ratio. The ortho and para positions of the phenolic hydroxyl groups in 3-methylphenol can participate in the condensation reaction, forming trifunctional branch nodes in the molecular chain. In 4-methylphenol, after the para position is occupied by a methyl group, only the ortho position participates in the reaction, forming a linear linking unit in the molecular chain. In 2,5-dimethylphenol, both ortho positions are occupied by methyl groups, creating steric hindrance; only the para position participates in the reaction, primarily connecting to the end of the molecular chain as a chain termination unit. The differences in reactivity of the three monomers and their proportions result in a suitable degree of branching and end structure in the resin molecular chains, which ensures both the mechanical strength and thermal stability of the film and provides appropriate free volume between molecular chains for the penetration of the developer.

[0009] The density and distribution of phenolic hydroxyl groups and methyl substituents in the resin structure formed by the phenolic monomers in this application determine the solubility and resolution performance of the photoresist. Phenolic hydroxyl groups provide reactive sites in the alkaline developer, while methyl substituents regulate the acidity of the phenolic hydroxyl groups and the overall hydrophilic / hydrophobic balance of the resin through hydrophobic and electron-donating effects. The meta-methyl group introduced by 3-methylphenol and the para-methyl group introduced by 4-methylphenol provide the resin with a suitable methyl substitution density, while the two ortho-methyl groups introduced by 2,5-dimethylphenol further increase the hydrophobic volume at the ends of the molecular chains. This distribution pattern of methyl substituents allows the resin molecular chains to form a stable and dense hydrogen bond network with the diazonaphthoquinone photosensitizer in the unexposed area, effectively inhibiting developer penetration. In the exposed area, after the photosensitizer is photolyzed into hydrophilic indicalic acid, the deprotonation rate of the phenolic hydroxyl groups in the resin molecular chains is moderately regulated by the electron-donating effect of the methyl groups, ensuring rapid dissolution of the exposed area in the developer while avoiding excessive etching of the unexposed area. The molar ratio of phenolic monomers to aldehyde monomers is controlled within a range where phenol is in excess, ensuring that both ends of the resin molecular chain are phenolic hydroxyl groups. These terminal phenolic hydroxyl groups enhance the intermolecular forces between the resin and the photosensitizer. Simultaneously, the distribution of these end groups ensures preferential wetting of the film surface during development, with the dissolution process progressing layer by layer from the surface inwards, effectively inhibiting the lateral penetration of the developer into unexposed areas. Through the synergistic effect of the above-mentioned combination and ratio of phenolic monomers and the phenol-aldehyde feed ratio, the resin forms a stable and dense hydrogen bond network with the photosensitizer in the unexposed areas, thus inhibiting dissolution. In the exposed areas, dissolution is rapid due to photosensitizer conversion. The contrast in dissolution rates between the exposed and unexposed areas is significantly amplified, resulting in steeper sidewalls and effectively improved resolution. Furthermore, the film maintains a high residual film rate after development, enabling it to withstand the harsh conditions of subsequent etching or injection processes.

[0010] Therefore, when the relative amount of aldehyde monomers increases, the chain growth reaction tends to be excessive, the molecular weight of the resin increases and cross-linked structures may appear, the dissolution rate of the resin in the exposure area in the alkaline developer decreases, the sensitivity decreases, and at the same time, excessive cross-linking of molecular chains leads to increased film brittleness, making it easy to generate crack defects during development.

[0011] When the 3-methylphenol content is too high, the resin molecular chains are excessively branched, making the film too rigid, hindering developer penetration, and reducing sensitivity. Simultaneously, excessive branching reduces the free volume between molecular chains, restricting the movement of photosensitizer molecules. Undecomposed photosensitizer after exposure forms residual defects during development. When the 2,5-dimethylphenol content is too low, the hydrophobic blocking effect at the molecular chain ends weakens, accelerating the rate at which developer penetrates the unexposed film edges. This erodes the edges of lines in the unexposed areas, resulting in decreased resolution.

[0012] Formaldehyde molecules have no alkyl or aryl substituents, resulting in a high condensation reaction rate with phenolic monomers that is unaffected by steric hindrance. It can undergo effective condensation reactions with three phenolic monomers of different reactivity, achieving a balance between a moderately branched structure, end hydrophobic blocking, and chain segment flexibility. This balance maximizes the dissolution rate difference between the exposed and unexposed areas, improving resolution, while also balancing the depth-of-focus window, defects, and sensitivity.

[0013] Preferably, the preparation method of the diazonaquinone compound includes: dissolving a polyphenol compound in dioxane, adding triethylamine, cooling to 0-5°C under nitrogen protection, slowly adding a dioxane solution containing diazonaquinone-5-sulfonyl chloride, continuing the reaction at room temperature for 4-6 hours after the addition is complete, and quenching the reaction with dilute hydrochloric acid to obtain the diazonaquinone compound.

[0014] Preferably, the polyphenol compound is selected from one or more of 1,3-bis(2,4-dihydroxy-3,5-dimethylphenyl)benzene, 2,2'-methylenebis(4,6-dimethylphenol), 1,1-bis(4-alkoxyphenyl)-1-(4-alkoxyphenyl)ethane, 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrahydroxycalix[4]aromatics, and tris(4-hydroxy-3,5-dimethylphenyl)methane.

[0015] More preferably, the polyphenol compound is 5,11,17,23-tetratert-butyl-25,26,27,28-tetrahydroxycalix[4] aromatic hydrocarbon.

[0016] The inventors discovered that diazonaquinone compounds, prepared by esterification of diazonaquinone sulfonyl chloride and polyphenolic compounds, can create a difference in dissolution rate between exposed and unexposed areas during photolithography, providing a dissolution contrast before and after exposure for the photoresist, thereby obtaining steep pattern sidewalls and achieving high resolution. Simultaneously, it helps reduce photoresist development defects and avoids residual defects after development due to photosensitizer issues. It also increases the depth-of-focus window to a certain extent; the increased steepness of the pattern edges brought about by high resolution can indirectly enlarge the depth-of-focus window. Furthermore, it ensures a high residual film rate for the photoresist, as the diazonaquinone compound can inhibit dissolution in unexposed areas, thus ensuring sufficient film thickness retention after development.

[0017] Specifically, the polyphenol compound in this application is 5,11,17,23-tetratert-butyl-25,26,27,28-tetrahydroxycalix[4] aryl. The calix aryl molecule has a rigid cyclic cavity structure, with four phenolic hydroxyl groups located at the upper edge of the cup and their spatial positions relatively fixed. After esterification with diazonaquinone sulfonyl chloride, the diazonaquinone groups are evenly distributed around the cup. The rigidity of the calix aryl skeleton ensures that the diazonaquinone groups maintain a fixed spatial spacing after esterification. The indolecarboxylate anions generated by photodecomposition during exposure form a uniformly distributed negative charge layer in the exposed area, ensuring the uniformity of the dissolution rate and improving the resolution. It also enables the esterification product to form a uniform hydrophobic distribution in the resin matrix in the unexposed area, avoiding the residual defects caused by excessive local hydrophobicity or the erosion of the unexposed area due to insufficient local hydrophobicity. Meanwhile, the four tert-butyl groups located at the lower edge of the calixarene provide an additional hydrophobic shielding effect in the unexposed region, enhancing the photosensitizer's efficiency in inhibiting resin alkali dissolution, thus enabling good dissolution inhibition with fewer esterification sites.

[0018] Preferably, the additive is selected from one or more of 1,1,1-tris(3-hydroxyphenyl)ethane, 1,1,1-tris(4-hydroxyphenyl)ethane, 1,1,1-tris(4-carboxymethoxyphenyl)ethane, 1,1,2,2-tetra(4-hydroxyphenyl)ethane, 1,1,2-tris(4-hydroxyphenyl)ethane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, 1,1-bis(4-hydroxyphenyl)butane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(4-hydroxyphenyl)ethane, 1,2,4-tris(4-hydroxyphenyl)benzene, and 1,3,5-tris(4-hydroxyphenyl)benzene.

[0019] Preferably, the additive is 2,6-bis[(2-hydroxy-3,5-dimethylphenyl)methyl]-4-methylphenol and 1,1,1-tris(4-carboxymethoxyphenyl)ethane in a mass ratio of 1:(0.4-0.8).

[0020] More preferably, the preparation method of 1,1,1-tris(4-carboxymethoxyphenyl)ethane includes: dissolving 1,1,1-tris(4-hydroxyphenyl)ethane in acetone, adding anhydrous potassium carbonate, stirring and adding chloroacetic acid-acetone solution dropwise, refluxing at 50-60°C for 5-8 hours to obtain 1,1,1-tris(4-carboxymethoxyphenyl)ethane.

[0021] The linear polyphenol 2,6-bis[(2-hydroxy-3,5-dimethylphenyl)methyl]-4-methylphenol bridges adjacent resin chains through its two phenolic hydroxyl groups, constructing a two-dimensional layered network. 1,1,1-tris(4-carboxymethoxyphenyl)ethane, through its three terminal carboxymethoxy groups, connects multiple resin chains, constructing a three-dimensional framework of nodes. These two elements interpenetrate and complement each other; the linear molecules fill the interlayer gaps, while the nonlinear molecules fix the relative positions of the interlayers, together forming a dense, three-dimensional cross-linked structure that effectively inhibits developer penetration. Simultaneously, the carboxymethoxy groups introduced by the nonlinear 1,1,1-tris(4-carboxymethoxyphenyl)ethane hydrolyze to generate carboxylate anions, allowing the nonlinear molecules to provide negative charge in the exposed region. This, combined with the neutral characteristics of the linear molecules, creates a chemical functional synergy, maintaining structural stability in the unexposed region and accelerating dissolution in the exposed region. This synergy further amplifies the dissolution rate difference between the exposed and unexposed regions. The increased dissolution rate difference makes the sidewalls of the pattern steeper, thus improving resolution. The increased steepness of the sidewalls reduces the variation in linewidth when the focus of the exposure unit shifts, and widens the depth-of-focus window. Unexposed areas are free of residue due to the effective suppression of the 3D network, reducing the number of defects in the exposed areas. In addition, the extra carboxylate anions provided by the modified star-shaped molecules increase the negative charge density in the exposed areas, and the hydration layer of tetramethylammonium cations in the developer carries water molecules to the exposed areas at a faster rate, increasing the amount of resin dissolved in the same exposure time and improving sensitivity.

[0022] Therefore, when the content of linear 2,6-bis[(2-hydroxy-3,5-dimethylphenyl)methyl]-4-methylphenol is too high, the resistance of the developer to penetrate along the interlayer direction is insufficient, and the unexposed area is eroded, leading to an increase in defects; when the content of 1,1,1-tris(4-carboxymethoxyphenyl)ethane is too high, the resin network obtains dense three-dimensional anchor points but the interlayer connection is insufficient, the overall integrity of the network is poor, and local network detachment during development is prone to producing floating resin defects.

[0023] Preferably, the solvent is selected from one or more of 1,2-butanediol, 1,2-propanediol diacetate, 2-heptanone, 1-methoxy-2-propanol, 2-methoxy-1-propanol, diethylene glycol monoethyl ether, 2-methoxy-1-methylethyl acetate, cyclohexyl acetate, methyl acetate, ethyl acetate, isopropyl acetate, ethyl 2-hydroxypropionate, 2-methoxy-1-methylethyl acetate, isobutyl acetate, γ-butyrolactone, and n-propanol.

[0024] Secondly, this application provides a method for preparing a positive photoresist, employing the following technical solution: A method for preparing a positive photoresist includes the following steps: adding phenolic resin to a solvent, stirring at room temperature, sequentially adding a diazonoquinone compound and an additive, stirring, filtering, and obtaining a positive photoresist.

[0025] In summary, this application includes at least one of the following beneficial technical effects: 1. Phenolic resin is prepared by polycondensation reaction of 3-methylphenol, 4-methylphenol and 2,5-dimethylphenol as phenolic monomers and formaldehyde as aldehyde monomer in the proportions of this application. This improves the uniformity of photoresist dissolution in alkaline developer, makes the sidewalls of the pattern steeper and the lines clearer, thereby improving the resolution of the photoresist, effectively reducing development defects and improving the quality of the photoresist.

[0026] 2. In this application, 2,6-bis[(2-hydroxy-3,5-dimethylphenyl)methyl]-4-methylphenol and 1,1,1-tris(4-carboxymethoxyphenyl)ethane are used as additives. They are spatially coordinated in the resin network to form a denser dissolution inhibition network, effectively blocking the penetration of developer into the unexposed area and keeping the dissolution rate at an extremely low level. This significantly amplifies the contrast in dissolution rates between the exposed and unexposed areas, resulting in steeper sidewalls and improved resolution. The steep sidewalls reduce the change in linewidth when defocusing, widening the depth-of-focus window. At the same time, the unexposed area is fully protected without residue, and the exposed area is fully dissolved without double-layer peeling, thereby reducing the number of defects. Detailed Implementation

[0027] Some of the raw materials used in the preparation examples and embodiments: Diazonaphthoquinone-5-sulfonyl chloride is 2-diazo-1-naphthoquinone-5-sulfonyl chloride, 2,6-bis[(2-hydroxy-3,5-dimethylphenyl)methyl]-4-methylphenol CAS 35924-04-0. Unless otherwise specified, all raw materials used in the examples and comparative examples are commercially available products.

[0028] Preparation Example 1 Preparation of phenolic resin: 1.2 mol of phenolic monomers were added to a reaction vessel, followed by 37% formaldehyde aqueous solution to achieve a molar ratio of phenolic monomers to aldehyde monomers of 1:0.8. 0.15 mol of oxalic acid was added, and the mixture was stirred and heated to 100℃ for 4-6 h. The system was then heated to 150℃ for atmospheric distillation, followed by vacuum distillation at 180℃ and a vacuum of 10 mmHg for 1-2 h to obtain phenolic resin. The phenolic monomers were 3-methylphenol, 4-methylphenol, and 2,5-dimethylphenol in a molar ratio of 5:5:2.

[0029] Preparation Example 2 Preparation of phenolic resin: 1.2 mol of phenolic monomers were added to a reaction vessel, followed by 37% formaldehyde aqueous solution to achieve a molar ratio of phenolic monomers to aldehyde monomers of 1:0.8. 0.15 mol of oxalic acid was added, and the mixture was stirred and heated to 100℃ for 4-6 h. The system was then heated to 150℃ for atmospheric distillation, followed by vacuum distillation at 180℃ and a vacuum of 10 mmHg for 1-2 h to obtain phenolic resin. The phenolic monomers were 3-methylphenol, 4-methylphenol, and 2,5-dimethylphenol in a molar ratio of 4:6:2.

[0030] Preparation Example 3 Preparation of phenolic resin: 1.2 mol of phenolic monomers were added to a reaction vessel, followed by 37% formaldehyde aqueous solution to achieve a molar ratio of phenolic monomers to aldehyde monomers of 1:0.8. 0.15 mol of oxalic acid was added, and the mixture was stirred and heated to 100℃ for 4-6 h. The system was then heated to 150℃ for atmospheric distillation, followed by vacuum distillation at 180℃ and a vacuum of 10 mmHg for 1-2 h to obtain phenolic resin. The phenolic monomers were 3-methylphenol, 4-methylphenol, and 2,5-dimethylphenol in a molar ratio of 5:3:4.

[0031] Preparation Example 4 Preparation of phenolic resin: 1.2 mol of phenolic monomers were added to a reaction vessel, followed by 37% formaldehyde aqueous solution to achieve a molar ratio of phenolic monomers to aldehyde monomers of 1:0.8. 0.15 mol of oxalic acid was added, and the mixture was stirred and heated to 100℃ for 4-6 h. The system was then heated to 150℃ for atmospheric distillation, followed by vacuum distillation at 180℃ and a vacuum of 10 mmHg for 1-2 h to obtain phenolic resin. The phenolic monomers were 4-methylphenol and 2,5-dimethylphenol in a molar ratio of 10:2.

[0032] Preparation Example 5 Preparation of phenolic resin: 1.2 mol of phenolic monomers were added to a reaction vessel, followed by 37% formaldehyde aqueous solution to achieve a molar ratio of phenolic monomers to aldehyde monomers of 1:0.8. 0.15 mol of oxalic acid was added, and the mixture was stirred and heated to 100℃ for 4-6 h. The system was then heated to 150℃ for atmospheric distillation, followed by vacuum distillation at 180℃ and a vacuum of 10 mmHg for 1-2 h to obtain phenolic resin. The phenolic monomers were 3-methylphenol and 2,5-dimethylphenol in a molar ratio of 10:2.

[0033] Preparation Example 6 Preparation of phenolic resin: 1.2 mol of phenolic monomers were added to a reaction vessel, followed by 37% formaldehyde aqueous solution to achieve a molar ratio of phenolic monomers to aldehyde monomers of 1:0.8. 0.15 mol of oxalic acid was added, and the mixture was stirred and heated to 100℃ for 4-6 h. The system was then heated to 150℃ for atmospheric distillation, followed by vacuum distillation at 180℃ and a vacuum of 10 mmHg for 1-2 h to obtain phenolic resin. The phenolic monomers were 4-methylphenol and 2,5-dimethylphenol in a molar ratio of 6:6.

[0034] Preparation Example 7 Preparation of phenolic resin: 1.2 mol of phenolic monomer was added to a reaction vessel, followed by 37% formaldehyde aqueous solution to achieve a molar ratio of phenolic monomer to aldehyde monomer of 1:0.8. 0.15 mol of oxalic acid was added, and the mixture was stirred and heated to 100℃ for 4-6 h. The system was then heated to 150℃ for atmospheric distillation, followed by vacuum distillation at 180℃ and a vacuum of 10 mmHg for 1-2 h to obtain phenolic resin. The phenolic monomer was 3-methylphenol.

[0035] Preparation Example 8 Preparation of diazonaquinone compounds: 0.1 mol of 5,11,17,23-tetratert-butyl-25,26,27,28-tetrahydroxycalix[4] aromatic hydrocarbon was dissolved in dioxane (8 times the weight of the polyphenol compound), 0.15 mol of triethylamine was added, and the temperature was lowered to 5°C under nitrogen protection. 1 L of dioxane solution containing 0.2 mol of diazonaquinone-5-sulfonyl chloride was slowly added dropwise. After the addition was completed, the ice bath was removed, and the temperature was naturally raised to room temperature. The reaction continued for 6 h. When the degree of esterification reached 1.2, dilute hydrochloric acid was added to adjust the pH of the system to 4 to quench the reaction. The system was distilled under reduced pressure, and dichloromethane was added to extract the system 3 times. The organic phases were combined, washed with water, dried with anhydrous sodium sulfate, filtered, and evaporated under reduced pressure. The crude product was dissolved in a small amount of dichloromethane and then added dropwise to n-hexane to precipitate. The product was collected by filtration and dried under vacuum at 40°C to obtain diazonaquinone compounds.

[0036] Preparation Example 9 Preparation of 1,1,1-tris(4-carboxymethoxyphenyl)ethane: 0.1 mol of 1,1,1-tris(4-hydroxyphenyl)ethane was dissolved in 0.3 L of acetone, and 0.15 mol of anhydrous potassium carbonate was added. A 0.5 L acetone solution containing 0.1 mol of chloroacetic acid was added dropwise with stirring. After the addition was complete, the mixture was heated to 56 °C and reacted for 6 h. The mixture was then cooled to room temperature, filtered, and distilled under reduced pressure. The pH was adjusted to 3 with dilute hydrochloric acid to precipitate the precipitate. The precipitate was washed with water until neutral and dried under vacuum at 50 °C to obtain 1,1,1-tris(4-carboxymethoxyphenyl)ethane. Example 1

[0037] A positive photoresist comprises the following raw materials in parts by weight: 100 parts of phenolic resin prepared in Preparation Example 1, 30 parts of diazonoquinone compound prepared in Preparation Example 8, 5 parts of additives, and 280 parts of solvent; wherein the additives are 1,1,1-tris(4-carboxymethoxyphenyl)ethane prepared in Preparation Example 9 in a mass ratio of 1:0.6; and the solvent is 2-heptanone.

[0038] The preparation method includes the following steps: adding phenolic resin to a solvent in proportion, stirring at room temperature, adding diazonium naphthoquinone compound and additives in sequence and stirring, coarsely filtering the adhesive solution through a plate and frame filter, filtering the coarsely filtered adhesive solution using a filter membrane with a pore size of 0.2 μm, dispensing and sealing to obtain positive photoresist. Example 2

[0039] A positive photoresist comprises the following raw materials in parts by weight: 100 parts of phenolic resin prepared in Preparation Example 1, 30 parts of diazononaphthoquinone compound prepared in Preparation Example 8, 5 parts of additives, and 280 parts of solvent; wherein the additives are 2,6-bis[(2-hydroxy-3,5-dimethylphenyl)methyl]-4-methylphenol and 1,1,1-tris(4-hydroxyphenyl)ethane in a mass ratio of 1:0.6; and the solvent is 2-heptanone.

[0040] The preparation method includes the following steps: adding phenolic resin to a solvent in proportion, stirring at room temperature, adding diazonium naphthoquinone compound and additives in sequence and stirring, coarsely filtering the adhesive solution through a plate and frame filter, filtering the coarsely filtered adhesive solution using a filter membrane with a pore size of 0.2 μm, dispensing and sealing to obtain positive photoresist. Example 3

[0041] A positive photoresist comprises the following raw materials in parts by weight: 100 parts of phenolic resin prepared in Preparation Example 1, 30 parts of diazononaphthoquinone compound prepared in Preparation Example 8, 5 parts of additives, and 280 parts of solvent; wherein the additives are 2,6-bis[(2-hydroxy-3,5-dimethylphenyl)methyl]-4-methylphenol and 1,1,1-tris(4-carboxymethoxyphenyl)ethane prepared in a mass ratio of 1:1; and the solvent is 2-heptanone.

[0042] The preparation method includes the following steps: adding phenolic resin to a solvent in proportion, stirring at room temperature, adding diazonium naphthoquinone compound and additives in sequence and stirring, coarsely filtering the adhesive solution through a plate and frame filter, filtering the coarsely filtered adhesive solution using a filter membrane with a pore size of 0.2 μm, dispensing and sealing to obtain positive photoresist. Example 4

[0043] A positive photoresist comprises the following raw materials in parts by weight: 100 parts of phenolic resin prepared in Preparation Example 1, 30 parts of diazonaphthoquinone compound prepared in Preparation Example 8, 5 parts of additive, and 280 parts of solvent; wherein the additive is 2,6-bis[(2-hydroxy-3,5-dimethylphenyl)methyl]-4-methylphenol; and the solvent is 2-heptanone.

[0044] The preparation method includes the following steps: adding phenolic resin to a solvent in proportion, stirring at room temperature, adding diazonium naphthoquinone compound and additives in sequence and stirring, coarsely filtering the adhesive solution through a plate and frame filter, filtering the coarsely filtered adhesive solution using a filter membrane with a pore size of 0.2 μm, dispensing and sealing to obtain positive photoresist. Example 5

[0045] A positive photoresist comprises the following raw materials in parts by weight: 100 parts of phenolic resin prepared in Preparation Example 1, 30 parts of diazonoquinone compound prepared in Preparation Example 8, 5 parts of additive, and 280 parts of solvent; wherein the additive is 1,1,1-tris(4-carboxymethoxyphenyl)ethane prepared in Preparation Example 9; and the solvent is 2-heptanone.

[0046] The preparation method includes the following steps: adding phenolic resin to a solvent in proportion, stirring at room temperature, adding diazonium naphthoquinone compound and additives in sequence and stirring, coarsely filtering the adhesive solution through a plate and frame filter, filtering the coarsely filtered adhesive solution using a filter membrane with a pore size of 0.2 μm, dispensing and sealing to obtain positive photoresist. Example 6

[0047] A positive photoresist comprises the following raw materials in parts by weight: 100 parts of phenolic resin prepared in Preparation Example 1, 30 parts of diazonoquinone compound prepared in Preparation Example 8, 5 parts of additive, and 280 parts of solvent; wherein the additive is 1,1,1-tris(4-hydroxyphenyl)ethane; and the solvent is 2-heptanone.

[0048] The preparation method includes the following steps: adding phenolic resin to a solvent in proportion, stirring at room temperature, adding diazonium naphthoquinone compound and additives in sequence and stirring, coarsely filtering the adhesive solution through a plate and frame filter, filtering the coarsely filtered adhesive solution using a filter membrane with a pore size of 0.2 μm, dispensing and sealing to obtain positive photoresist. Example 7

[0049] A positive photoresist comprises the following raw materials in parts by weight: 100 parts of phenolic resin prepared in Preparation Example 1, 30 parts of diazononaphthoquinone compound prepared in Preparation Example 8, 5 parts of additives, and 280 parts of solvent; wherein the additives are 2,6-bis[(2-hydroxy-3,5-dimethylphenyl)methyl]-4-methylphenol and 1,1,1-tris(4-carboxymethoxyphenyl)ethane prepared in a mass ratio of 1:0.6; and the solvent is 1-methoxy-2-propanol.

[0050] The preparation method includes the following steps: adding phenolic resin to a solvent in proportion, stirring at room temperature, adding diazonium naphthoquinone compound and additives in sequence and stirring, coarsely filtering the adhesive solution through a plate and frame filter, filtering the coarsely filtered adhesive solution using a filter membrane with a pore size of 0.2 μm, dispensing and sealing to obtain positive photoresist.

[0051] Comparative Example 1 A positive photoresist comprises the following raw materials in parts by weight: 100 parts of phenolic resin obtained in Preparation Example 2, 30 parts of diazononaphthoquinone compound obtained in Preparation Example 8, 5 parts of additives, and 280 parts of solvent; wherein the additives are 2,6-bis[(2-hydroxy-3,5-dimethylphenyl)methyl]-4-methylphenol and 1,1,1-tris(4-carboxymethoxyphenyl)ethane obtained in Preparation Example 9 in a mass ratio of 1:0.6; and the solvent is 2-heptanone.

[0052] The preparation method includes the following steps: adding phenolic resin to a solvent in proportion, stirring at room temperature, adding diazonium naphthoquinone compound and additives in sequence and stirring, coarsely filtering the adhesive solution through a plate and frame filter, filtering the coarsely filtered adhesive solution using a filter membrane with a pore size of 0.2 μm, dispensing and sealing to obtain positive photoresist.

[0053] Comparative Example 2 A positive photoresist comprises the following raw materials in parts by weight: 100 parts of phenolic resin obtained in Preparation Example 3, 30 parts of diazononaphthoquinone compound obtained in Preparation Example 8, 5 parts of additives, and 280 parts of solvent; wherein the additives are 2,6-bis[(2-hydroxy-3,5-dimethylphenyl)methyl]-4-methylphenol and 1,1,1-tris(4-carboxymethoxyphenyl)ethane obtained in Preparation Example 9 in a mass ratio of 1:0.6; and the solvent is 2-heptanone.

[0054] The preparation method includes the following steps: adding phenolic resin to a solvent in proportion, stirring at room temperature, adding diazonium naphthoquinone compound and additives in sequence and stirring, coarsely filtering the adhesive solution through a plate and frame filter, filtering the coarsely filtered adhesive solution using a filter membrane with a pore size of 0.2 μm, dispensing and sealing to obtain positive photoresist.

[0055] Comparative Example 3 A positive photoresist comprises the following raw materials in parts by weight: 100 parts of phenolic resin obtained in Preparation Example 4, 30 parts of diazononaphthoquinone compound obtained in Preparation Example 8, 5 parts of additives, and 280 parts of solvent; wherein the additives are 2,6-bis[(2-hydroxy-3,5-dimethylphenyl)methyl]-4-methylphenol and 1,1,1-tris(4-carboxymethoxyphenyl)ethane obtained in Preparation Example 9 in a mass ratio of 1:0.6; and the solvent is 2-heptanone.

[0056] The preparation method includes the following steps: adding phenolic resin to a solvent in proportion, stirring at room temperature, adding diazonium naphthoquinone compound and additives in sequence and stirring, coarsely filtering the adhesive solution through a plate and frame filter, filtering the coarsely filtered adhesive solution using a filter membrane with a pore size of 0.2 μm, dispensing and sealing to obtain positive photoresist.

[0057] Comparative Example 4 A positive photoresist comprises the following raw materials in parts by weight: 100 parts of phenolic resin obtained in Preparation Example 5, 30 parts of diazonaphthoquinone compound obtained in Preparation Example 8, 5 parts of additives, and 280 parts of solvent; wherein the additives are 2,6-bis[(2-hydroxy-3,5-dimethylphenyl)methyl]-4-methylphenol and 1,1,1-tris(4-carboxymethoxyphenyl)ethane obtained in Preparation Example 9 in a mass ratio of 1:0.6; and the solvent is 2-heptanone.

[0058] The preparation method includes the following steps: adding phenolic resin to a solvent in proportion, stirring at room temperature, adding diazonium naphthoquinone compound and additives in sequence and stirring, coarsely filtering the adhesive solution through a plate and frame filter, filtering the coarsely filtered adhesive solution using a filter membrane with a pore size of 0.2 μm, dispensing and sealing to obtain positive photoresist.

[0059] Comparative Example 5 A positive photoresist comprises the following raw materials in parts by weight: 100 parts of phenolic resin obtained in Preparation Example 6, 30 parts of diazononaphthoquinone compound obtained in Preparation Example 8, 5 parts of additives, and 280 parts of solvent; wherein the additives are 2,6-bis[(2-hydroxy-3,5-dimethylphenyl)methyl]-4-methylphenol and 1,1,1-tris(4-carboxymethoxyphenyl)ethane obtained in Preparation Example 9 in a mass ratio of 1:0.6; and the solvent is 2-heptanone.

[0060] The preparation method includes the following steps: adding phenolic resin to a solvent in proportion, stirring at room temperature, adding diazonium naphthoquinone compound and additives in sequence and stirring, coarsely filtering the adhesive solution through a plate and frame filter, filtering the coarsely filtered adhesive solution using a filter membrane with a pore size of 0.2 μm, dispensing and sealing to obtain positive photoresist.

[0061] Comparative Example 6 A positive photoresist comprises the following raw materials in parts by weight: 100 parts of phenolic resin obtained in Preparation Example 7, 30 parts of diazononaphthoquinone compound obtained in Preparation Example 8, 5 parts of additives, and 280 parts of solvent; wherein the additives are 2,6-bis[(2-hydroxy-3,5-dimethylphenyl)methyl]-4-methylphenol and 1,1,1-tris(4-carboxymethoxyphenyl)ethane obtained in Preparation Example 9 in a mass ratio of 1:0.6; and the solvent is 2-heptanone.

[0062] The preparation method includes the following steps: adding phenolic resin to a solvent in proportion, stirring at room temperature, adding diazonium naphthoquinone compound and additives in sequence and stirring, coarsely filtering the adhesive solution through a plate and frame filter, filtering the coarsely filtered adhesive solution using a filter membrane with a pore size of 0.2 μm, dispensing and sealing to obtain positive photoresist.

[0063] The performance of the positive photoresists prepared in the examples and comparative examples was tested using the following methods: Positive photoresists from each embodiment and comparative example were spin-coated onto the surface of an 8-inch single-crystal silicon wafer using a TEL CleanTrack ACT8 coating and developing machine. The spin-coating speed was adjusted to achieve a dried photoresist film thickness of 0.6 μm. After coating, the photoresist-coated silicon wafer was placed on a hot plate and pre-baked at 100°C for 60 seconds to evaporate excess solvent and obtain a uniform photoresist layer. The prepared sample was placed under a high-pressure mercury lamp and exposed using a Nikon NSR2205I12D i-line stepper exposure machine. A single wavelength light source of 365 nm was used to expose the silicon wafer through a mask with a specific linewidth density pattern. After exposure, the silicon wafer was placed on a hot plate and post-baked at 115°C for 60 seconds. Subsequently, it was developed using a 2.38 wt% tetramethylammonium hydroxide aqueous solution by spraying for 60 seconds. Then, it was rinsed with deionized water to remove residual developer and spun dry to obtain the photoresist pattern.

[0064] The cross-sectional and top morphology of the graphic lines were observed at the same magnification using a Hitachi CD-SEM S-9220 scanning electron microscope, and the minimum line width of the dense lines was measured as the resolution. Under optimal exposure energy, the focusing position of the exposure unit was changed, and the change in linewidth under different focusing conditions was measured. The maximum focusing offset within ±10% of the target size was used as the depth of focus window. The test results are shown in Table 1. Table 1 Performance Test Results Example 1 0.30 0.90 Example 2 0.31 0.85 Example 3 0.32 0.88 Example 4 0.33 0.80 Example 5 0.35 0.65 Example 6 0.36 0.60 Example 7 0.32 0.85 Comparative Example 1 0.34 0.70 Comparative Example 2 0.36 0.65 Comparative Example 3 0.35 0.55 Comparative Example 4 0.38 0.55 Comparative Example 5 0.39 0.50 Comparative Example 6 0.40 0.45 The positive photoresists prepared in Examples 1-7 exhibit excellent performance. Through the distribution and density adjustment of methyl substituents in phenolic resin, the use of diazonaphthoquinone compounds, and the spatial complementarity and functional synergy of the two additives, the dissolution rate difference between the exposed and unexposed areas is increased. This meets the comprehensive requirements of i-line lithography for high resolution, wide process window, and low defect rate, and has good prospects for industrial application.

[0065] Comparative Examples 1 and 1-6 show that phenolic resin is formed by the condensation polymerization of specific phenolic monomers and aldehyde monomers, and is used as the film-forming skeleton of photoresist. Combined with the diazonoquinone photosensitizer additive system, the photoresist achieves a significantly improved contrast in the dissolution rate between the exposed and unexposed areas during the development process. The phenolic resin is copolymerized from 3-methylphenol, 4-methylphenol and 2,5-dimethylphenol in a specific ratio. The difference in reactivity of the three monomers and their ratio combination make the resin molecular chain present with a suitable degree of branching and end structure, thereby achieving higher resolution. The diazonoquinone compound with a calix[4] aromatic skeleton is used as the photosensitizer. Its rigid cyclic cavity structure and the hydrophobic shielding effect of the four tert-butyl groups ensure the uniform dispersion of the photosensitizer in the resin matrix and the effective dissolution inhibition of the unexposed area. This ensures the full generation of indene carboxylic acid in the exposed area and avoids defects caused by excessive inhibition in the unexposed area.

[0066] Comparative examples 1-7 show that the linear polyphenol 2,6-bis[(2-hydroxy-3,5-dimethylphenyl)methyl]-4-methylphenol and the nonlinear polyphenol 1,1,1-tris(4-carboxymethoxyphenyl)ethane, through their interpenetration and complementarity, form a dense three-dimensional cross-linked structure that effectively inhibits developer penetration. Simultaneously, the introduced carboxymethoxy group hydrolyzes in the alkaline developer to generate carboxylate anions, which, along with the indenecarboxylate anions generated by the photolysis of the photosensitizer, significantly enhance the negative charge density and hydrophilicity of the exposed area. This accelerates the migration rate of tetramethylammonium cations and water molecules to the exposed area, maximizing the difference in dissolution rates between the exposed and unexposed areas. This, in turn, improves the photoresist resolution, depth of focus window, and reduces defects.

[0067] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A positive photoresist, characterized in that: The raw materials include the following parts by weight: 100 parts of phenolic resin, 30-45 parts of diazonoquinone compound, 3-5 parts of additives, and 250-350 parts of solvent; the phenolic resin is prepared by polycondensation reaction of phenolic monomers and aldehyde monomers in a molar ratio of 1:(0.75-0.85); the phenolic monomers include 3-methylphenol:4-methylphenol:2,5-dimethylphenol in a molar ratio of (5-6):(5-7):(1-2).

2. The positive photoresist according to claim 1, characterized in that: The aldehyde monomer is one or more of formaldehyde, 2,4-dimethylbenzaldehyde, 2,5-dimethylbenzaldehyde, 4-isopropylbenzaldehyde, and 4-formylbenzaldehyde.

3. The positive photoresist according to claim 1, characterized in that: The preparation method of the diazononaphthoquinone compound includes: dissolving a polyphenol compound in dioxane, adding triethylamine, cooling to 0-5°C under nitrogen protection, slowly adding a dioxane solution containing diazononaphthoquinone-5-sulfonyl chloride, continuing the reaction at room temperature for 4-6 hours after the addition is complete, and quenching the reaction with dilute hydrochloric acid to obtain the diazononaphthoquinone compound.

4. The positive photoresist according to claim 3, characterized in that: The polyphenolic compound is selected from one or more of 1,3-bis(2,4-dihydroxy-3,5-dimethylphenyl)benzene, 2,2'-methylenebis(4,6-dimethylphenol), 1,1-bis(4-alkoxyphenyl)-1-(4-alkoxyphenyl)ethane, 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrahydroxycalix[4]aromatics, and tris(4-hydroxy-3,5-dimethylphenyl)methane.

5. The positive photoresist according to claim 1, characterized in that: The additive is selected from one or more of 1,1,1-tris(3-hydroxyphenyl)ethane, 1,1,1-tris(4-hydroxyphenyl)ethane, 1,1,1-tris(4-carboxymethoxyphenyl)ethane, 1,1,2,2-tetra(4-hydroxyphenyl)ethane, 1,1,2-tris(4-hydroxyphenyl)ethane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, 1,1-bis(4-hydroxyphenyl)butane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(4-hydroxyphenyl)ethane, 1,2,4-tris(4-hydroxyphenyl)benzene, and 1,3,5-tris(4-hydroxyphenyl)benzene.

6. The positive photoresist according to claim 1, characterized in that: The additive is 2,6-bis[(2-hydroxy-3,5-dimethylphenyl)methyl]-4-methylphenol and 1,1,1-tris(4-carboxymethoxyphenyl)ethane in a mass ratio of 1:(0.4-0.8).

7. The positive photoresist according to claim 1, characterized in that: The solvent is selected from one or more of the following: 1,2-butanediol, 1,2-propanediol diacetate, 2-heptanone, 1-methoxy-2-propanol, 2-methoxy-1-propanol, diethylene glycol monoethyl ether, 2-methoxy-1-methylethyl acetate, cyclohexyl acetate, methyl acetate, ethyl acetate, isopropyl acetate, ethyl 2-hydroxypropionate, 2-methoxy-1-methylethyl acetate, isobutyl acetate, γ-butyrolactone, and n-propanol.

8. The method for preparing a positive photoresist according to claims 1-7, characterized in that: The process includes the following steps: adding phenolic resin to a solvent, stirring at room temperature, adding diazonoquinone compound and additives sequentially, stirring, filtering, and obtaining a positive photoresist.