A photoresist, a method for preparing the same and a photolithography method

Abstract

This invention discloses a photoresist and its preparation and photolithography methods. The photoresist comprises phenolic resin, a photosensitizer, a solvent, and additives. The solvent includes propylene glycol methyl ether, propylene glycol methyl ether acetate, low-boiling-point alcohol solvents, and aliphatic alkane solvents. In this invention, the photoresist uses a quaternary solvent system (PGME / PGMEA / alcohol / alkane), which establishes a rapid evaporation channel through the alcohol and alkane, enabling rapid solvent evaporation and low residue control during low-temperature baking, thus ensuring photosensitivity stability. The introduction of volatile alcohol solvents significantly reduces solvent residue after low-temperature baking, eliminating the influence of residual solvent on the quantum efficiency of the photosensitizer, resulting in a more stable exposure energy window and an exposure latitude (EL) controlled above 25%.

Description

[0001] This invention claims priority to Chinese Patent Application No. CN2025120229789, filed on December 30, 2025, entitled "A photoresist and its preparation method and photolithography method", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention belongs to the field of photolithography technology, specifically relating to a low-temperature baking positive photoresist suitable for the manufacture of flexible OLED (organic light-emitting diode) display panels, a method for preparing the photoresist, and a corresponding method for photolithography using the photoresist. Background Technology

[0003] Currently, traditional phenolic resin-based photoresists face the following main technical challenges under low-temperature baking conditions (80±5℃): 1. Incomplete solvent evaporation (core and primary issue): Traditional high-boiling-point solvents such as PGMEA / PGME are difficult to fully evaporate during short baking times at 80℃, resulting in excessively high residual solvent content in the photoresist film (e.g., exceeding 6%). Excessive residual solvent alters the solubility characteristics of the photoresist, accelerates the photosensitizer reaction rate, causes severe instability in exposure dose (EL), and narrows the development process window, which is the main cause of yield loss.

[0004] 2. Insufficient heat curing: Solvent residue problems worsen the cross-linking and curing of the resin. Conventional phenolic resins have insufficient cross-linking density (gel content <65%) at 80℃, resulting in a residual film rate fluctuation of more than ±12% after development, which can easily cause short circuits in the circuit.

[0005] 3. Limited photosensitivity: Commercial naphthoquinone-based photosensitizers show significant decrease in quantum efficiency (ε<500L / mol·cm) in the 300-450nm wavelength range. Combined with solvent residue, this results in an exposure latitude (EL) of less than ±8%.

[0006] 4. Thermal expansion mismatch: The combination of high molecular weight resin and low polarity solvent leads to a difference in thermal shrinkage rate of more than 18%, causing a critical dimension (CD) offset of more than ±0.15μm for a fine linewidth of 3μm.

[0007] The aforementioned problems result in a yield loss of 15-20% for existing low-temperature photoresists during mass production. Therefore, it is urgent to improve the photoresist formulation, solve the problem of incomplete solvent evaporation under low-temperature baking, and thus comprehensively improve the overall performance of the photoresist.

[0008] The above background information is provided only to aid in understanding the inventive concept and technical solution of this invention. It does not necessarily belong to the prior art of this invention. In the absence of clear evidence that the above information was disclosed before the filing date of this invention, the above background information should not be used to evaluate the novelty and inventiveness of this invention. Summary of the Invention

[0009] In view of this, in order to overcome the shortcomings of the prior art, the purpose of this invention is to provide an improved photoresist that can solve the problems of insufficient curing and narrow process window of traditional photoresists under low temperature conditions.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: A photoresist includes a phenolic resin, a photosensitizer, a solvent, and additives, wherein the solvent includes propylene glycol methyl ether (PGME), propylene glycol methyl ether acetate (PGMEA), low-boiling-point alcohol solvents, and aliphatic alkane solvents.

[0011] According to some preferred embodiments of the present invention, the volume ratio of propylene glycol methyl ether, propylene glycol methyl ether acetate, low-boiling-point alcohol solvent and aliphatic alkane solvent is 2-3:1:0.3-1:0.2-1.

[0012] According to some preferred embodiments of the invention, the low-boiling-point alcohol solvent includes one or more of ethanol, benzyl alcohol, and isopropanol. Ethanol or a solvent containing ethanol is preferred.

[0013] According to some preferred embodiments of the invention, the aliphatic alkane solvent includes one or more of hexane, heptane, and cyclohexane. Preferably, it is n-heptane or contains n-heptane.

[0014] According to some preferred embodiments of the present invention, the additive includes an organosilicon substance and a plasticizer, wherein the content of the plasticizer is greater than that of the organosilicon substance.

[0015] According to some preferred embodiments of the invention, the organosilicon material includes silane coupling agents and / or perfluoropolyether silanes.

[0016] According to some preferred embodiments of the invention, the plasticizer comprises a styrene polymer.

[0017] According to some preferred embodiments of the invention, the styrene-based polymers include styrene-butadiene-styrene block copolymers and / or hydrogenated styrene-butadiene block copolymers.

[0018] According to some preferred embodiments of the present invention, the photosensitizer, solvent and additives are 16-18 parts, 100-500 parts and 0.1-5 parts respectively, based on 100 parts of phenolic resin.

[0019] According to some preferred embodiments of the present invention, the phenolic resin includes one or more phenolic resins with different molecular weights between 5,000 and 20,000.

[0020] According to some preferred embodiments of the present invention, the phenolic resin is obtained by mixing multiple phenolic resins with a molecular weight difference of more than 5,000.

[0021] According to some preferred embodiments of the invention, the photosensitizer comprises an azide naphthoquinone sulfonate compound capable of absorbing light at wavelengths of 300-430 nm.

[0022] According to some preferred embodiments of the invention, the photosensitizer comprises one or more of azide naphthoquinone esters with benzophenone, TPPA, or BIOC as the backbone.

[0023] The principle of this invention is roughly as follows: By introducing aliphatic alkanes (preferably n-heptane) and low-boiling-point alcohols (preferably ethanol) into the PGMEA / PGME (propylene glycol methyl ether acetate / propylene glycol methyl ether) solvent system, the overall vaporization pressure of the mixed solvent is significantly reduced by utilizing the positive azeotropy effect formed between the two. Synergistic deboiling principle: Although the monomeric boiling points of n-heptane (boiling point approximately 98°C) and ethanol (boiling point approximately 78°C) are not low, in the azeotropic state, the hydrogen bonds between molecules of different polarities are broken, allowing the mixed component to have a vapor pressure much higher than that of the individual components under low-temperature baking conditions of 80°C. This allows solvent molecules to rapidly detach from the photoresist film in the form of "molecular clusters," thereby achieving deep solvent desolventizing. Azeotropic ratio: Experimental studies have found that the mass ratio of n-heptane to ethanol forming an azeotrope at normal pressure is approximately 52:48, and the boiling point of this azeotropic component is only approximately 70.9°C.

[0024] Simultaneously, during the initial 80°C pre-bake stage after photoresist coating, the azeotropic system formed by n-heptane and ethanol undergoes flash evaporation first. Due to the extremely low surface tension of the aliphatic alkane solvent (n-heptane), it can drive high-boiling-point PGMEA and PGME molecules to migrate towards the film surface during evaporation, forming microscopic "solvent evaporation channels." This mechanism effectively solves the problem of skin formation on the film surface in traditional processes, which hinders internal solvent diffusion. By controlling the volume ratio of n-heptane to ethanol within the preferred range of 1:1 to 2:1, this invention successfully reduces the residual solvent rate within the film from the conventional 6%-8% to below 3.5%.

[0025] The lower solvent residue can greatly reduce the physical plasticizing effect in the film, so that the quantum efficiency of the photosensitizer is no longer affected by the fluctuation of the residual solvent concentration, thereby achieving a high degree of consistency of exposure energy (Eop) and improving the stability of photosensitivity.

[0026] Meanwhile, although the azeotropic system of the present invention evaporates very quickly, by introducing 0.1-5 parts of high-boiling-point styrene plasticizer, the volume shrinkage stress caused by the rapid escape of solvent can be compensated, achieving a synergistic plasticizing effect and ensuring that while obtaining extremely low residue, excellent surface smoothness Ra<0.4nm is maintained.

[0027] The present invention also provides a method for preparing the photoresist as described above, comprising the following steps: mixing phenolic resin, photosensitizer, solvent and additives evenly and then filtering to obtain the photoresist.

[0028] The present invention also provides a photolithography method, comprising the following steps: spin-coating the photoresist as described above onto a substrate, drying it at 80±5℃ and then exposing it through a photomask; developing it with a developer and then cleaning it, etching the substrate and then washing it with water, immersing it in a photoresist remover solution to remove the photoresist, and finally washing and drying it with water to complete the photolithography.

[0029] In some embodiments of the present invention, the photolithography method includes the following steps: 1. Coating and pre-baking: Spin-coat the above photoresist onto the substrate, perform soft baking at 80±5℃ and control the film thickness.

[0030] 2. Exposure: Exposure is performed using a photomask, with an exposure energy gradient of 32.5-38 mJ / cm². 2 .

[0031] 3. Development and fixing: After development with developer, rinse with deionized water.

[0032] 4. Etching and resist removal: After etching the substrate, wash it with water, immerse it in a resist removal solution to remove the resist, and finally wash and dry it to complete the photolithography.

[0033] Compared to existing technologies, the advantages of this invention, due to the adoption of the above technical solutions, are as follows: The photoresist of this invention utilizes a quaternary solvent system (PGME / PGMEA / alcohols / aliphatic alkanes) to establish a rapid evaporation channel through alcohols and aliphatic alkanes. This enables rapid solvent evaporation and low residue control during low-temperature baking, ensuring photosensitivity stability. The introduction of volatile alcohol solvents significantly reduces solvent residue after low-temperature baking, eliminating the impact of residual solvent on the quantum efficiency of the photoresist, resulting in a more stable exposure energy window and an exposure latitude (EL) controlled above 25%. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 The graph shows the variation of 3µm Pattern CD of the photoresist prepared in Example 6 and Comparative Example 1 of this invention with exposure energy. Detailed Implementation

[0036] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0037] The low-temperature baking positive photoresist and its photolithography process provided by this invention solve the low-temperature baking problem by introducing the synergistic effect of low-boiling-point solvents and high-boiling-point styrene plasticizers, and mainly achieve the following objectives: By introducing volatile, low-boiling-point alcohols and aliphatic alkane solvents, the solvent system of the photoresist is optimized, solving the core problem of incomplete solvent evaporation under 80℃ low-temperature baking conditions, ensuring that the solvent residue rate in the film is less than 5%, thereby significantly improving the stability of the photoresist's photosensitivity.

[0038] To address the issue of decreased photoresist film flatness due to rapid evaporation after introducing low-boiling-point solvents, a high-boiling-point styrene-based plasticizer is introduced to optimize the film-forming properties of the photoresist, ensuring film flatness and precise linewidth control of fine patterns.

[0039] By solving the problems of solvent evaporation and film surface flatness, and combining the resin compounding system, the photoresist is fully cured, achieving a process window and dimensional stability comparable to conventional 110℃ baking, and ensuring precise control of linewidths of 3μm and below.

[0040] To achieve the above objectives, the photoresist of the present invention comprises phenolic resin, a photosensitizer, a solvent, and additives. Based on 100 parts by weight of phenolic resin, the photosensitizer, solvent, and additives are 16-18 parts, 100-500 parts, and 0.1-5 parts, respectively. In some embodiments, specifically preferably, when the phenolic resin is 100 parts by weight, the photosensitizer is 17.5 parts, the mixed solvent is 300 parts (PGME:PGMEA:ethanol:aliphatic alkanes, for example, 2:1:1:1), and the compounded additives are 1.8 parts (a combination of silane coupling agent, perfluoropolyether silane, and high-boiling-point styrene plasticizer).

[0041] The phenolic resin, based on 100 parts by weight, is used as the film-forming resin, preferably one or more cresol phenolic resins with different molecular weights between 5000 and 20000. Preferably, the phenolic resin is a mixture of multiple phenolic resins with a molecular weight difference of more than 5000. A compound system of high molecular weight resin (Mw=20,000) and low molecular weight resin (Mw=5,000) is preferred, for example, 75 parts of high molecular weight resin + 25 parts of low molecular weight resin, to balance curing speed and film-forming properties. Specifically, one or more combinations of NT40B20G, NT40B80G, and NT31B15G from Asahi Organic Materials Resin (Nantong) Co., Ltd. are preferred.

[0042] Photosensitizer: 15-20 parts, which is an azide naphthoquinone sulfonate compound capable of absorbing light with a wavelength of 300-430 nm, preferably including one or more azide naphthoquinone esters with benzophenone, TPPA, or BIOC as the backbone. Specifically, it is preferably one or more combinations of JDP5435 ​​and JDT525 from Tianjin Jiuri New Material Co., Ltd., and BOA528 from Meiyuan Special Chemical Co., Ltd.

[0043] Solvent: 100-500 parts, selected from one or more of propylene glycol methyl ether (PGME), propylene glycol methyl ether acetate (PGMEA), ethanol, benzyl alcohol, isopropanol, hexane, heptane, cyclohexane, etc. More preferably, PGMEA, PGME, and a quaternary mixture of volatile low-boiling-point alcohol solvents and aliphatic alkane solvents are used. The low-boiling-point alcohol solvent is one or more of ethanol, benzyl alcohol, and isopropanol, preferably ethanol or containing ethanol. The aliphatic alkane solvent is one or more of hexane, heptane, and cyclohexane, preferably n-heptane or containing n-heptane. In some embodiments, the volume ratio of propylene glycol methyl ether, propylene glycol methyl ether acetate, low-boiling-point alcohol solvent, and aliphatic alkane solvent is preferably 2-3:1:0.3-1:0.2-1. The introduction of alcohol and aliphatic alkane solvents aims to accelerate the overall evaporation rate of the solvent at low temperature (80°C), effectively reducing the amount of solvent residue after baking, thereby ensuring the stability of the photoresist's photosensitivity.

[0044] Additives: 0.1-5 parts, including silicone-based additives that enhance adhesion (such as silane coupling agents and / or perfluoropolyether silanes) and plasticizers (such as high-boiling-point styrene polymers) comprising 1-5 parts of the total photoresist. The purpose of introducing high-boiling-point styrene plasticizers is to improve the flowability and smoothness of the photoresist film after coating, compensate for the decrease in film surface performance caused by the introduction of fast-drying solvents, and ensure the photolithographic accuracy of fine patterns. Silane coupling agents include KH-560, KH-570, silane A174, and Dow Corning. ® One or more of Z-6030; the perfluoropolyether silane is one or more of Fluorolink® S10, BYK-310, and FTX-218; The high-boiling-point styrene plasticizer is one or more of the styrene-butadiene-styrene block copolymer (SBS-792E) or hydrogenated styrene-butadiene block copolymer (SEBS-503T) from Hunan Petrochemical.

[0045] The above method for preparing photoresist includes the following steps: mixing phenolic resin, photosensitizer, solvent and additives evenly and then filtering to obtain photoresist.

[0046] In some embodiments, the method for preparing photoresist by mixing and filtration specifically includes: mixing the components of the photoresist in a certain proportion, and filtering the mixture using a 0.1 μm pore size filter membrane to obtain liquid photoresist. The filtration step is necessary to ensure that the colloid is free of impurities; solvent blending can optimize the evaporation rate and film uniformity.

[0047] The photolithography method of the present invention specifically includes the following steps: 1. Coating and Pre-baking: Spin-coat photoresist onto the treated substrate and soft bake at 80±5℃ for 120 seconds, controlling the film thickness to 2μm. The baking temperature must be controlled at 80±5℃ to avoid damaging the heat-sensitive substrate.

[0048] 2. Exposure: I-line exposure is performed using a photomask, with an exposure energy gradient of 32.5-38 mJ / cm². 2 .

[0049] 3. Development and fixing: Develop with 2.38wt% tetramethylammonium hydroxide (TMAH) solution for 60 seconds, then rinse with deionized water.

[0050] 4. Etching and Resin Removal: After etching the substrate, wash it with water, immerse it in a resist removal solution to remove the resist, and finally wash and dry it.

[0051] The present invention is described in detail below through six embodiments and six comparative examples. All embodiments are operated according to the above photolithography process steps, and the baking conditions are 80℃ / 120 seconds. The EL calculation method is as follows: the target CD is 3um, and the allowable fluctuation is + / -10%, that is, 3.3um-2.7um, EL = (acceptable maximum exposure (CD is 2.7um) - acceptable minimum exposure (CD is 3.3um)) / optimal exposure (CD is 3um).

[0052] Example 1 (Optimal Quaternary Solvent System) Components: 100 parts of phenolic resin NT31B15G, 15 parts of photosensitizer JDP5435, 300 parts of solvent PGME:PGMEA:ethanol:n-heptane (volume ratio 2:1:1:1), and 0.5 parts of auxiliary agent silane coupling agent KH-560.

[0053] Results: The process window ΔCD = 0.82 μm. The residual solvent content in the film decreased to 3.2%. The addition of PGME further optimized the resin solubility and film uniformity, and the synergistic boiling-reducing effect of the quaternary solvent system was optimal.

[0054] Example 2 (Optimized photosensitizer dosage) Composition: Based on Example 1, the amount of photosensitizer JDP5435 ​​was increased to 17.5 parts.

[0055] Results: Process window ΔCD = 0.84 μm. Optimization of photosensitizer dosage improved the efficiency of the photosensitivity reaction and made the exposure energy window (Eop) more stable.

[0056] Example 3 (Introduction of a compound resin system) Components: Phenolic resin: NT31B15G 75 parts + NT40B80G 25 parts, photosensitizer JDP5435 ​​17.5 parts, solvent same as in Example 1 (quaternary system) 300 parts, auxiliary agent silane coupling agent KH-560 0.5 parts.

[0057] Results: Process window ΔCD = 0.86 μm. High molecular weight resin ensures mechanical strength, low molecular weight resin improves crosslinking density and leveling at low temperatures, and the compounded resin allows for more complete curing of the film and improved dimensional stability.

[0058] Example 4 (Introduction of high-boiling-point styrene plasticizer to improve film surface) Composition: Based on Example 1, an additional high-boiling-point styrene plasticizer, styrene-butadiene-styrene block copolymer SBS792E, is added to the additive system.

[0059] Results: Process window ΔCD = 0.88 μm. Film surface roughness improved from Ra≈0.6 nm to Ra<0.5 nm. High-boiling-point styrene plasticizers effectively compensated for the internal stress caused by rapid solvent evaporation, significantly improving film surface smoothness.

[0060] Example 5 (Optimized Plasticizer Ratio) Composition: Based on Example 1, the amount of styrene-butadiene-styrene block copolymer SBS792E was increased to 1.5 parts.

[0061] Results: Process window ΔCD = 0.90 μm. Film surface roughness was further optimized to Ra < 0.4 nm. The optimal balance between plasticizer improving smoothness and avoiding excessive softening of the film was found.

[0062] Example 6 (The optimal solution after comprehensive optimization) Components: Phenolic resin: NT31B15G 75 parts + NT40B80G 25 parts.

[0063] Photosensitive agent: (JDP5345:JDT525:BOA528=2:1:1) 17.5 parts.

[0064] Solvent: 300 parts of mixed solvent: PGME: PGMEA: ethanol: n-heptane (volume ratio 2:1:1:1).

[0065] Additives: 0.4 parts of silane coupling agent KH-560 + 0.4 parts of perfluoropolyether silane BYK-310 + 1.5 parts of plasticizer SBS792E.

[0066] result: Solvent residue: reduced to 3.0%.

[0067] Process window: ΔCD improved to 0.95μm, demonstrating an extremely wide process tolerance.

[0068] Film quality: Surface roughness Ra<0.35nm, with excellent flatness.

[0069] Linewidth control: 3μm linewidth at exposure energy of 32.5-38mJ / cm 2 The variation within the range is gradual, and the critical size (CD) offset is controlled within ±0.08μm.

[0070] Comparative Example 1 (Traditional High-Temperature Process) Conditions: Commercially available conventional phenolic resin positive photoresist AZ 1500 was used, and the standard recommended baking temperature of 110°C was adopted. Other process parameters were the same as those in the embodiments of the present invention.

[0071] Results: Process window ΔCD = 0.60 μm. This formulation is stable at high temperatures, but it is completely unsuitable for heat-sensitive substrates such as flexible OLEDs that require low-temperature processes, and it also consumes a lot of energy.

[0072] Comparative Example 2 (Traditional Formula for Low-Temperature Application) Composition: The same photoresist as Comparative Example 1, but forcibly baked at 80°C.

[0073] Results: The process window ΔCD shrank drastically to 0.45 μm. The solvent residue rate inside the film was as high as 7.5%-8.0%, and severe residual film and linewidth distortion appeared after development, with a yield loss of more than 20%, proving that the traditional formulation cannot meet the requirements of low-temperature processes.

[0074] Comparative Example 3 (Base Solvent) Components: 100 parts of phenolic resin (Mw=20,000), JDP5435, 100 parts of solvent PGME:PGMEA (volume ratio 2:1), and 0.5 parts of auxiliary agent silane coupling agent.

[0075] Results: The process window ΔCD = 0.60 μm. The solvent evaporation was insufficient at 80 °C, and the performance of this formulation was comparable to Comparative Example 1 at 110 °C, but still superior to Comparative Example 2, demonstrating the basic feasibility of the low-temperature process.

[0076] Comparative Example 4 (Introducing low-boiling-point alcohol solvents) Components: 100 parts of phenolic resin NT31B15G, 15 parts of photosensitizer JDP5435, 200 parts of solvent PGME:PGMEA:ethanol (volume ratio 2:1:1), and 0.5 parts of auxiliary agent silane coupling agent KH-560.

[0077] Results: Process window ΔCD = 0.70 μm. Solvent residue in the membrane decreased to approximately 5.5%. The introduction of ethanol initially improved the evaporation rate and photosensitivity, but the membrane surface smoothness began to decrease.

[0078] Comparative Example 5 (Optimized alcohol solvent ratio) Components: 100 parts of phenolic resin NT31B15G, 15 parts of photosensitizer JDP5435, 200 parts of solvent PGME:PGMEA:ethanol (volume ratio 0.5:0.5:1), and 0.5 parts of auxiliary agent silane coupling agent KH-560.

[0079] Results: The process window ΔCD = 0.75 μm. The solvent residue in the film was further reduced to 5.0%. However, the film surface roughness increased to Ra≈0.7 nm, indicating that while the high proportion of alcohol improved the residue, it also caused film-forming problems.

[0080] Comparative Example 6 (Introducing alkane solvents to construct a ternary system) Components: 100 parts of phenolic resin NT31B15G, 15 parts of photosensitizer JDP5435, 300 parts of solvent PGMEA: ethanol: n-heptane (volume ratio 1:1:1), and 0.5 parts of auxiliary agent silane coupling agent KH-560.

[0081] Results: The process window ΔCD = 0.80 μm. The solvent residue rate within the film was significantly reduced to 3.8%. The introduction of n-heptane formed an azeotropic effect with ethanol, establishing a "rapid evaporation channel" and greatly improving solvent removal efficiency. However, it caused a sudden change in the solvent evaporation rate, resulting in "orange peel" defects on the film surface, affecting the smoothness and uniformity of the photoresist surface.

[0082] Conclusion: Through the comparison of the above embodiments and comparative examples, it is clear that the embodiments of the present invention effectively solve the core bottleneck of low-temperature baking—the problem of solvent residue—through a quaternary azeotropic solvent system; ensure the full curing and mechanical properties of the film through a compound resin system; and compensate for film surface defects caused by rapid evaporation by introducing a high-boiling-point styrene plasticizer. The synergistic effect of these three factors ultimately achieves superior overall performance compared to the traditional 110℃ baking process at a low temperature of 80℃, making it particularly suitable for the high-precision manufacturing of flexible display devices.

[0083] Results: The process window ΔCD was improved to at least 0.90 μm, the film surface roughness was restored to Ra < 0.35 nm, and solvent residue was well controlled, resulting in the best overall performance. After baking at 80 °C, the composite resin system in Example 6 achieved a process window ΔCD of 0.85 μm and an exposure latitude EL > 15.7%, while the control photoresist had a ΔCD of only 0.6-0.7 μm and a latitude of 10%.

[0084] Comparative Example 1 and Example 6 were used to verify the critical dimension (CD) and exposure amount: The above data indicates that at an exposure energy of 32.5-38 mJ / cm², 2 Within the range, the 3μm linewidth of the photoresist in Example 6 changes gradually (from 3.23μm to 2.72μm), while the linewidth of Comparative Example 1 changes drastically (from 3.58μm to 2.55μm), indicating that the present invention is not sensitive to fluctuations in exposure energy, proving that the product has a more stable process window.

[0085] This application relates to the field of photoresist materials technology, specifically a low-temperature baking positive photoresist and its photolithography process suitable for the manufacture of flexible OLED (organic light-emitting diode) display panels. This technology is mainly applied to the manufacturing process of touch electrodes for high-curvature flexible display devices (such as foldable screens and rollable screens), solving the problems of insufficient curing and narrow process windows of traditional photoresists under low-temperature conditions. It avoids damage to the light-emitting layer caused by high-temperature baking, achieving rapid low-temperature curing while ensuring photosensitivity stability and film quality, resulting in a 15-20% performance improvement. The photoresist of this invention can achieve high performance under low-temperature baking, with the following main advantages: 1. A quaternary solvent system (PGME / PGMEA / alcohols / alkanes) establishes a rapid evaporation channel through alcohols and alkanes, enabling rapid solvent evaporation and low residue control during low-temperature baking of the photoresist, thus ensuring photosensitivity stability. The introduction of volatile alcohol solvents significantly reduces solvent residue after low-temperature baking, eliminating the impact of residual solvent on the quantum efficiency of the photoresist, resulting in a more stable exposure energy window and an exposure latitude (EL) controlled above 15%.

[0086] 2. Synergistic optimization of high-boiling-point styrene plasticizers and silicone additives in the synergistic process addresses defects caused by fast-drying solvents, improving film surface smoothness and dimensional stability. The use of high-boiling-point styrene plasticizers effectively improves coating defects caused by fast-drying solvents, ensuring low surface roughness of the photoresist film (e.g., Ra < 0.5 μm), further guaranteeing the critical dimension (CD) control accuracy of 3 μm fine linewidth.

[0087] 3. A compound system of phenolic resins (combination of high molecular weight and low molecular weight) ensures crosslinking density and film-forming properties at low temperatures.

[0088] The above embodiments prepared by the method of the present invention are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A photoresist, characterized in that, It includes phenolic resin, photosensitizer, solvent and additives, wherein the solvent includes at least propylene glycol methyl ether, propylene glycol methyl ether acetate, low-boiling-point alcohol solvent and aliphatic alkane solvent; the volume ratio of propylene glycol methyl ether, propylene glycol methyl ether acetate, low-boiling-point alcohol solvent and aliphatic alkane solvent is 2-3:1:0.3-1:0.2-1.

2. The photoresist according to claim 1, characterized in that, The low-boiling-point alcohol solvents include one or more of ethanol, benzyl alcohol, and isopropanol; the aliphatic alkane solvents include one or more of hexane, heptane, and cyclohexane.

3. The photoresist according to claim 1, characterized in that, The additives include organosilicon substances and plasticizers; the organosilicon substances include silane coupling agents and / or perfluoropolyether silanes; the plasticizers include styrene polymers.

4. The photoresist according to claim 3, characterized in that, The styrene polymer includes hydrogenated styrene-butadiene block copolymers and / or styrene-butadiene-styrene block copolymers.

5. The photoresist according to claim 1, characterized in that, Based on 100 parts of phenolic resin, the photosensitizer, solvent, and additives are 16-18 parts, 100-500 parts, and 0.1-5 parts, respectively.

6. The photoresist according to claim 1 or 5, characterized in that, The phenolic resin includes one or more phenolic resins with different molecular weights between 5,000 and 20,000.

7. The photoresist according to claim 6, characterized in that, The phenolic resin is obtained by mixing multiple phenolic resins with a molecular weight difference of more than 5,000.

8. The photoresist according to claim 1, characterized in that, The photosensitizer includes an azide naphthoquinone sulfonate compound capable of absorbing light with wavelengths of 300-430 nm.

9. A method for preparing a photoresist as described in any one of claims 1-8, characterized in that, The process includes the following steps: mixing phenolic resin, photosensitizer, solvent and additives evenly and filtering to obtain the photoresist.

10. A photolithography method, characterized in that, The process includes the following steps: coating a substrate with the photoresist as described in any one of claims 1-8, drying it at 80±5°C, and then exposing it through a photomask; developing it with a developer and then cleaning it; etching the substrate and then washing it with water to remove the photoresist; finally cleaning and drying it to complete the photolithography.

Images