Low-temperature curing polyimide photoresist and patterning method and application thereof

Abstract

The invention discloses a low-temperature curing polyimide photoresist and a patterning method and application thereof, and belongs to the technical field of photoresist, the patterning method comprises the following steps: (1) under the protection of inert gas, adding an aromatic dianhydride monomer into a diamine monomer solution, and stirring for reaction to obtain a polyamide acid solution; the diamine monomer comprises an alkynyl-containing diamine monomer and an aromatic diamine monomer; and (2) adding a photobase generator into the polyamide acid solution, uniformly mixing, coating a substrate with the mixture, removing the solvent, and carrying out ultraviolet curing development and heat treatment to complete an imidization reaction, so that the photoresist is cured, and the polyimide pattern is obtained. The low-temperature curing polyimide photoresist provided by the invention is a'photobase generator + alkynyl crosslinking 'composite photosensitive system, the contradiction among low-temperature curing, sensitivity and material performance of a traditional system is broken through, and an innovative solution is provided for manufacturing of advanced electronics.

Description

Technical Field

[0001] This invention belongs to the field of photoresist technology, and particularly relates to a low-temperature curing polyimide photoresist and its patterning method and application. Background Technology

[0002] With the rapid development of flexible electronics, 5G communication, and high-density integrated circuits, there is an urgent need for polyimide photoresists that combine low-temperature processability, high sensitivity, and excellent thermal / electrical properties. Traditional polyimide photoresists rely on high-temperature thermal imidization (>350℃) to achieve polyamic acid ring closure, leading to thermal deformation of flexible substrates (such as PET and PI), device delamination failure, and high energy consumption hindering the progress of green manufacturing. Currently, negative photoresist systems exist (such as polyimides based on alkynyl groups for photocrosslinking), which can form crosslinked networks through ultraviolet irradiation, but suffer from low sensitivity (>300 mJ / cm). 2 Insufficient development contrast makes it difficult to meet the requirements of submicron patterning. In addition, conventional photosensitizers (such as diazonoquinone and free radical initiators) require high-temperature post-curing. During this process, residual acidic / free radical substances can easily degrade the dielectric properties of the material, limiting its application in high-frequency devices.

[0003] In recent years, the industry has attempted to improve the process window using photoacid generators (PAGs) or low-temperature decomposable end-capping agents. However, PAGs leave behind strong acid residues that can corrode metal circuits, while end-capping agents involve complex processes and are costly. Single photosensitivity mechanisms (such as relying solely on alkynyl crosslinking or photoalkali generator catalysis) are insufficient to synergistically improve sensitivity and resolution, and the insufficient ring-closure rate of polyimide under low-temperature curing leads to a decrease in the mechanical strength and moisture resistance of the film.

[0004] Therefore, how to provide a method that can cure at low temperatures and improve the sensitivity, resolution, and mechanical properties of photoresists is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a low-temperature curing polyimide photoresist and its patterning method and application.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A low-temperature curing polyimide photoresist, the structure of which is shown in formula (I):

[0008]

[0009] (I);

[0010] Among them, R1 is independently selected , , One of them;

[0011] R2 is independently selected from or ;

[0012] R3 is or .

[0013] A method for patterning low-temperature curing polyimide photoresist includes the following steps:

[0014] (1) Under the protection of an inert gas, an aromatic dianhydride monomer is added to a solution of a diamine monomer and the reaction is stirred to obtain a polyamic acid solution; the diamine monomer includes a diamine monomer containing an alkynyl group and an aromatic diamine monomer;

[0015] (2) Add a photoalkali-generating agent to the polyamic acid solution, mix evenly to obtain a photoresist solution, coat the photoresist solution onto the substrate, remove the solvent, and then complete the imidization reaction by ultraviolet light curing and heat treatment to solidify the photoresist and obtain a polyimide pattern.

[0016] Preferably, the diamine monomer (A) containing an alkynyl group in step (1) is selected from one of 4,4'-(but-1,3-diyne-1,4-diyl)diphenylamine, 1,4-bis(3-aminophenyl)butadiyne and bis(4-aminophenyl)acetylene.

[0017] Beneficial effects: After UV exposure, the alkynyl groups of the diamine monomer containing alkynyl groups in this invention undergo efficient click chemistry (without the need for photo-generated acids / alkalis), forming a robust covalent cross-linked network between polymer chains through inter-alkynyl cycloaddition. This significantly improves the dissolution contrast during development, resulting in ultra-high resolution patterns. Simultaneously, this alkynyl-based cross-linking mechanism endows the material with excellent thermal stability and mechanical strength, and the cross-linking process exhibits minimal shrinkage, effectively reducing internal stress and ensuring pattern fidelity and film integrity.

[0018] Preferably, the aromatic diamine monomer (B) in step (1) is selected from 4,4'-diaminodiphenyl ether (ODA) and 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB).

[0019] Preferably, the aromatic dianhydride monomer (C) in step (1) is selected from one of pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), and hexafluorodianhydride (6FDA).

[0020] Preferably, the molar ratio of the diamine monomer containing an alkynyl group to the aromatic diamine monomer in step (1) is (10-50):(50-90).

[0021] Beneficial Effects: This invention selects diamine monomers containing alkynyl groups and aromatic diamine monomers in a molar ratio of (10-50):(50-90) to copolymerize, precisely controlling the crosslinking density and overall performance of the polyimide. This ratio ensures that sufficient alkynyl groups (10-50%) are embedded in the polymer backbone, enabling the formation of a fully and stably crosslinked network through efficient alkyne cycloaddition reactions after UV exposure, thereby providing high development contrast and pattern resolution. If the alkynyl-containing diamine monomer content is too high, it will not be exposed, and the polymer chain itself will be very difficult to dissolve due to the aforementioned rigidity and pre-aggregation, making it undevelopable. The significantly retained aromatic diamine segments (50-90%) effectively guarantee the good solubility and film-forming properties of the polyimide precursor, as well as the excellent flexibility and heat resistance of the cured film, avoiding material embrittlement caused by excessively high crosslinking density, thus achieving a balance between high-resolution patterning and excellent bulk properties.

[0022] More preferably, the solvent in the solution of the diamine monomer in step (1) is one or more of N,N-dimethylacetamide, N-methylpyrrolidone, and N,N-dimethylformamide.

[0023] More preferably, the solid content of the polyamic acid solution in step (1) is 10-20%.

[0024] More preferably, the stirring reaction in step (1) is carried out under light-protected conditions for 12 hours.

[0025] Preferably, the photoalkali-generating agent in step (2) is selected from 2-nitrobenzyltrimethylammonium hydroxide or bis(4-tert-butylphenyl)iodonium trifluoromethanesulfonate.

[0026] Beneficial Effects: The photo-alkali-generating agent selected in this invention can efficiently and quantitatively release strong organic bases (such as trimethylamine) or strong base anions under ultraviolet light irradiation, thereby catalyzing the chemical imidization ring-closure reaction of polyamic acid in situ. This process achieves precise linkage between photolithography and curing, generating alkali catalysts only in the exposed area, allowing this area to preferentially and completely imidize during subsequent mild heat treatment, forming an insoluble network structure, thus significantly improving development resolution and pattern resolution. Simultaneously, it avoids the problems of poor storage stability and resolution degradation caused by adding additional hot alkali catalysts, achieving a balance with high pattern fidelity.

[0027] Preferably, the amount of photoalkali-generating agent added in step (2) is 0.5-3 wt% of the mass of the polyamic acid solution.

[0028] Beneficial effects: Within the above range, the photoresist maintains extremely high photosensitivity, generating a sufficient concentration of alkaline catalyst even with low exposure dosage, thus significantly improving processing efficiency. Simultaneously, this dosage achieves extremely high dissolution contrast between exposed and unexposed areas, ensuring high resolution and sharp edges in the developed pattern. More importantly, this low dosage avoids excessive small molecule residue, ensuring complete decomposition or volatilization during subsequent heat treatment, thereby not affecting the insulation, chemical resistance, and mechanical strength of the cured polyimide.

[0029] Preferably, the heat treatment in step (2) is performed at a temperature of 80-220°C for 10-60 minutes.

[0030] More preferably, the heat treatment is performed at 80°C for 30 minutes, during which the catalyst promotes the ring-closing reaction, followed by heating to 180°C for 30 minutes to complete the residual imidization.

[0031] Application of a low-temperature curing polyimide photoresist in flexible OLED display substrates, 5G high-frequency packaging, or three-dimensional structures of microfluidic chips.

[0032] Compared with the prior art, the present invention has the following advantages and technical effects:

[0033] The low-temperature curing polyimide photoresist provided by this invention is a composite photosensitive system of "photoalkali-generating agent + alkynyl crosslinking". In this system, the photoalkali-generating agent releases an alkaline catalyst under ultraviolet light, which catalyzes the dehydration and imidization of polyamic acid at a low temperature of 80-180℃ on the one hand, and enhances the crosslinking density in the exposure area on the other hand. The alkynyl groups form a rigid network through cycloaddition, which synergistically improves the development contrast and pattern accuracy. This invention breaks through the contradiction between low-temperature curing, sensitivity and material performance in traditional systems, and provides an innovative solution for the manufacturing of advanced electronics. Detailed Implementation

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 are within the scope of protection of the present invention.

[0035] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to specific embodiments.

[0036] This invention discloses a low-temperature curing polyimide photoresist, the structure of which is shown in formula (I):

[0037]

[0038] (I);

[0039] Among them, R1 is independently selected , , One of them;

[0040] R2 is independently selected from or ;

[0041] R3 is or .

[0042] In this invention, the photoresist solution undergoes an intermolecular [2+2] cycloaddition crosslinking reaction under ultraviolet irradiation to form a negative pattern. Simultaneously, a photoalkali-producing agent is photolyzed to produce alkali, catalyzing the dehydration and imidization of polyamic acid. The alkaline catalyst generated by the decomposition of the photoalkali-producing agent promotes the ring-closing reaction at low temperature. Combined with curing at 180~220℃, this ensures that the film has a high glass transition temperature, low dielectric constant, and excellent mechanical strength.

[0043] This invention also discloses a method for patterning low-temperature curing polyimide photoresist, comprising the following steps:

[0044] (1) Under the protection of an inert gas, an aromatic dianhydride monomer is added to a solution of a diamine monomer and the reaction is stirred to obtain a polyamic acid solution; the diamine monomer includes a diamine monomer containing an alkynyl group and an aromatic diamine monomer;

[0045] (2) Add a photoalkali-generating agent to the polyamic acid solution, mix evenly to obtain a photoresist solution, coat the photoresist solution onto the substrate, remove the solvent, and then complete the imidization reaction by ultraviolet light curing and heat treatment to solidify the photoresist and obtain a polyimide pattern.

[0046] In a preferred embodiment, the diamine monomer (A) containing an alkynyl group in step (1) is selected from one of 4,4'-(but-1,3-diyne-1,4-diyl)diphenylamine, 1,4-bis(3-aminophenyl)butadiyne and bis(4-aminophenyl)acetylene.

[0047] In a preferred embodiment, the aromatic diamine monomer (B) in step (1) is selected from 4,4'-diaminodiphenyl ether (ODA) and 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB).

[0048] Preferably, the aromatic dianhydride monomer (C) in step (1) is selected from one of pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), and hexafluorodianhydride (6FDA).

[0049] In a preferred embodiment, the molar ratio of the diamine monomer containing an alkynyl group to the aromatic diamine monomer in step (1) is (10-50):(50-90).

[0050] In a more preferred embodiment, the solvent in the solution of the diamine monomer in step (1) is one or more of N,N-dimethylacetamide, N-methylpyrrolidone, and N,N-dimethylformamide.

[0051] In a more preferred embodiment, the solid content of the polyamic acid solution in step (1) is 10-20%.

[0052] In a more preferred embodiment, the stirring reaction in step (1) is a stirring reaction under light-protected conditions for 12 hours.

[0053] In a preferred embodiment, the photoalkali-generating agent in step (2) is selected from 2-nitrobenzyltrimethylammonium hydroxide or bis(4-tert-butylphenyl)iodonium trifluoromethanesulfonate.

[0054] In a preferred embodiment, the amount of photoalkali-generating agent added in step (2) is 0.5-3 wt% of the mass of the polyamic acid solution.

[0055] In a preferred embodiment, the heat treatment in step (2) is performed at a temperature of 80-220°C for a time of 10-60 minutes.

[0056] In a more preferred embodiment, the heat treatment is performed by heat treatment at 80°C for 30 minutes, during which the catalyst promotes the ring-closing reaction, followed by heat treatment at 180°C for 30 minutes to complete the residual imideation.

[0057] This invention also discloses the application of a low-temperature curing polyimide photoresist in flexible OLED display substrates, 5G high-frequency packaging, or the three-dimensional structure of microfluidic chips.

[0058] Unless otherwise specified, all raw materials used in the embodiments of this invention were purchased through commercial channels;

[0059] Unless otherwise specified, room temperature or normal temperature in the embodiments of the present invention refers to 25±3℃.

[0060] Example 1

[0061] A method for patterning low-temperature curing polyimide photoresist includes the following steps:

[0062] (1) Under the protection of an inert gas (such as nitrogen), 4,4'-(but-1,3-diyne-1,4-diyl)diphenylamine and 4,4'-diaminodiphenyl ether were weighed in a molar ratio of 3:7 and dissolved in N,N-dimethylacetamide solvent. Then, pyromellitic dianhydride was slowly added, wherein the molar ratio of pyromellitic dianhydride to diamine (4,4'-(but-1,3-diyne-1,4-diyl)diphenylamine and 4,4'-diaminodiphenyl ether) was 1:1. The reaction was stirred at room temperature in the dark for 12 hours to form a polyamic acid solution with a solid content of 15%.

[0063] (2) Add 1% by weight of 2-nitrobenzyltrimethylammonium hydroxide to the polyamic acid solution obtained in step (1), stir in the dark for 2 hours to obtain a photoresist solution, spin coat the photoresist solution onto a quartz substrate to form a film layer, place it on an 80°C hot plate to dry for 300 seconds to evaporate most of the solvent and obtain a dry film; expose the dry film with i-line, then develop it with TMAH aqueous solution (1% tetramethylammonium hydroxide aqueous solution), then clean it with deionized water, then heat treat it at 80°C for 30 minutes, and then heat treat it at 180°C for 30 minutes to cure the photoresist and obtain a polyimide pattern.

[0064] Example 2

[0065] A method for patterning low-temperature curing polyimide photoresist includes the following steps:

[0066] (1) Under the protection of an inert gas (such as nitrogen), 4,4'-(but-1,3-diyne-1,4-diyl)diphenylamine and 4,4'-diaminodiphenyl ether were weighed in a molar ratio of 1:9 and dissolved in N,N-dimethylacetamide solvent. Then, pyromellitic dianhydride was slowly added, wherein the molar ratio of pyromellitic dianhydride to diamine (4,4'-(but-1,3-diyne-1,4-diyl)diphenylamine and 4,4'-diaminodiphenyl ether) was 1:1. The reaction was stirred at room temperature in the dark for 12 hours to form a polyamic acid solution with a solid content of 15%.

[0067] (2) Add 1% by weight of 2-nitrobenzyltrimethylammonium hydroxide to the polyamic acid solution obtained in step (1), stir in the dark for 2 hours to obtain a photoresist solution, spin coat the photoresist solution onto a quartz substrate to form a film layer, place it on an 80°C hot plate to dry for 300 seconds to evaporate most of the solvent and obtain a dry film; expose the dry film with i-line, then develop it with TMAH aqueous solution (1% tetramethylammonium hydroxide aqueous solution), then clean it with deionized water, then heat treat it at 80°C for 30 minutes, and then heat treat it at 180°C for 30 minutes to cure the photoresist and obtain a polyimide pattern.

[0068] Example 3

[0069] A method for patterning low-temperature curing polyimide photoresist includes the following steps:

[0070] (1) Under the protection of an inert gas (such as nitrogen), 4,4'-(but-1,3-diyne-1,4-diyl)diphenylamine and 4,4'-diaminodiphenyl ether were weighed in a molar ratio of 1:1 and dissolved in N,N-dimethylacetamide solvent. Then, pyromellitic dianhydride was slowly added, wherein the molar ratio of pyromellitic dianhydride to diamine (4,4'-(but-1,3-diyne-1,4-diyl)diphenylamine and 4,4'-diaminodiphenyl ether) was 1:1. The reaction was then stirred at room temperature in the dark for 12 hours to form a polyamic acid solution with a solid content of 15%.

[0071] (2) Add 1% by weight of 2-nitrobenzyltrimethylammonium hydroxide to the polyamic acid solution obtained in step (1), stir in the dark for 2 hours to obtain the required photoresist solution, spin coat the photoresist solution onto the quartz substrate to form a film layer, place it on an 80°C hot plate to dry for 300 seconds to evaporate most of the solvent and obtain a dry film; expose the dry film with i-line, then develop it with TMAH aqueous solution (1% tetramethylammonium hydroxide aqueous solution), then clean it with deionized water, then heat treat it at 80°C for 30 minutes, and then heat treat it at 180°C for 30 minutes to cure the photoresist and obtain a polyimide pattern.

[0072] Example 4

[0073] A method for patterning low-temperature curing polyimide photoresist includes the following steps:

[0074] (1) Under the protection of an inert gas (such as nitrogen), 4,4'-(but-1,3-diyne-1,4-diyl)diphenylamine and 4,4'-diaminodiphenyl ether were weighed in a molar ratio of 3:7 and dissolved in N,N-dimethylacetamide solvent. Then, pyromellitic dianhydride was slowly added, wherein the molar ratio of pyromellitic dianhydride to diamine (4,4'-(but-1,3-diyne-1,4-diyl)diphenylamine and 4,4'-diaminodiphenyl ether) was 1:1. The reaction was then stirred at room temperature in the dark for 12 hours to form a polyamic acid solution with a solid content of 15%.

[0075] (2) Add 2% by weight of 2-nitrobenzyltrimethylammonium hydroxide to the polyamic acid solution obtained in step (1), stir in the dark for 2 hours to obtain the required photoresist solution, spin coat the photoresist solution onto the quartz substrate to form a film layer, place it on an 80°C hot plate to dry for 300 seconds to evaporate most of the solvent and obtain a dry film; expose the dry film with i-line, then develop it with TMAH aqueous solution (1% tetramethylammonium hydroxide aqueous solution), then clean it with deionized water, then heat treat it at 80°C for 30 minutes, and then heat treat it at 180°C for 30 minutes to cure the photoresist and obtain a polyimide pattern.

[0076] Example 5

[0077] The only difference from Example 1 is that the alkynyl diamine monomer used is bis(4-aminophenyl)acetylene. All other process steps and parameters are the same as in Example 1.

[0078] Comparative Example 1

[0079] The only difference from Example 1 is that in step (1), 4,4'-(but-1,3-diyne-1,4-diyl)diphenylamine and 4,4'-diaminodiphenyl ether are weighed in a molar ratio of 5:95, that is, 4,4'-(but-1,3-diyne-1,4-diyl)diphenylamine accounts for 5% of the total amount of diamine, and finally the cured polyimide photoresist is obtained. The remaining process steps and parameters are the same as in Example 1.

[0080] Comparative Example 2

[0081] The only difference from Example 1 is that in step (1), 4,4'-(but-1,3-diyne-1,4-diyl)diphenylamine and 4,4'-diaminodiphenyl ether are weighed in a molar ratio of 75:25, that is, 4,4'-(but-1,3-diyne-1,4-diyl)diphenylamine accounts for 75% of the total amount of diamine, and the cured polyimide photoresist is finally obtained. The remaining process steps and parameters are the same as in Example 1.

[0082] Comparative Example 3

[0083] The only difference from Example 1 is that 0.1% by weight of 2-nitrobenzyltrimethylammonium hydroxide is added to the polyamic acid solution in step (2), and the high-temperature curing temperature is 180°C. Specifically, the steps include:

[0084] (1) Same as Example 1.

[0085] (2) Add 0.3% by mass of 2-nitrobenzyltrimethylammonium hydroxide to the polyamic acid solution obtained in step (1), stir in the dark for 2 hours to obtain a photoresist solution, spin coat the photoresist solution onto a quartz substrate to form a film layer, place it on an 80°C hot plate to dry for 300 seconds to evaporate most of the solvent and obtain a dry film; expose the dry film with i-line, then develop it with TMAH aqueous solution (1% tetramethylammonium hydroxide aqueous solution), then clean it with deionized water, then heat treat it at 80°C for 30 minutes, and then heat treat it at 180°C for 30 minutes to cure the photoresist and obtain a polyimide pattern.

[0086] Comparative Example 4

[0087] The only difference from Example 1 is that in step (2), 4% by weight of 2-nitrobenzyltrimethylammonium hydroxide of polyamic acid solution is added, and the high-temperature curing temperature is 180°C. Specifically, the steps are as follows:

[0088] (1) Same as Example 1.

[0089] (2) Add 4% by weight of 2-nitrobenzyltrimethylammonium hydroxide to the polyamic acid solution obtained in step (1), stir in the dark for 2 hours to obtain a photoresist solution, spin coat the photoresist solution onto a quartz substrate to form a film layer, place it on an 80°C hot plate to dry for 300 seconds to evaporate most of the solvent and obtain a dry film; expose the dry film with i-line, then develop it with TMAH aqueous solution (1% tetramethylammonium hydroxide aqueous solution), then clean it with deionized water, then heat treat it at 80°C for 30 minutes, and then heat treat it at 180°C for 30 minutes to cure the photoresist and obtain a polyimide pattern.

[0090] Comparative Example 5

[0091] The only difference from Example 1 is that step (2) does not include the photo-alkali-generating agent 2-nitrobenzyltrimethylammonium hydroxide, and specifically includes the following steps:

[0092] (1) Same as Example 1.

[0093] (2) Spin-coat the polyamic acid solution obtained in step (1) onto a quartz substrate to form a film layer, place it on an 80°C hot plate and dry it for 300s to evaporate most of the solvent and obtain a dry film; expose the dry film with i-line, then develop it with TMAH aqueous solution (1% tetramethylammonium hydroxide aqueous solution), then clean it with deionized water, then heat it at 80°C for 30 minutes, and then heat it at 180°C for 30 minutes to cure the photoresist and obtain a polyimide pattern.

[0094] Comparative Example 6

[0095] The only difference from Example 1 is that step (1) does not include 4,4'-(but-1,3-diyne-1,4-diyl)diphenylamine, and specifically includes the following steps:

[0096] (1) Under the protection of an inert gas (such as nitrogen), weigh 4,4'-diaminodiphenyl ether and dissolve it in N,N-dimethylacetamide solvent. Then, slowly add pyromellitic dianhydride, wherein the molar ratio of pyromellitic dianhydride to 4,4'-diaminodiphenyl ether is 1:1. Stir the reaction at room temperature in the dark for 12 hours to form a polyamic acid solution with a solid content of 15%.

[0097] (2) Add 1% by weight of 2-nitrobenzyltrimethylammonium hydroxide to the polyamic acid solution obtained in step (1), stir in the dark for 2 hours to obtain a photoresist solution, spin coat the photoresist solution onto a quartz substrate to form a film layer, place it on an 80°C hot plate to dry for 300 seconds to evaporate most of the solvent and obtain a dry film; expose the dry film with i-line, then develop it with TMAH aqueous solution (1% tetramethylammonium hydroxide aqueous solution), then clean it with deionized water, then heat treat it at 80°C for 30 minutes, and then heat treat it at 180°C for 30 minutes to cure the photoresist and obtain a polyimide pattern.

[0098] Technical effects:

[0099] 1. The i-line photosensitivity and resolution of the polyimide patterns obtained in Examples 1-4 and Comparative Examples 1-5 were tested according to ASTM E1131 standard, and the results are shown in Table 1:

[0100] Table 1

[0101]

[0102] Alkyne diamine ratio (Examples 1-3 vs. Comparative Examples 1, 2, 6): Examples 1-3 (ratios of 30%, 10%, and 50%) were all successful, with Examples 1 and 3, at appropriate ratios, exhibiting the best sensitivity (150, 135 mJ / cm). 2 The results showed that there exists an optimal molar ratio range (approximately 10%-50%), with measured resolutions of 15 and 20 μm. The alkynyl diamine acts as a "switch" for photocrosslinking, and Comparative Example 6 (without alkynyl groups) was completely unpatternable, demonstrating its indispensability. Comparative Example 1 (5% concentration) exhibited extremely poor sensitivity (480 mJ / cm²). 2 The result indicates insufficient cross-linking points; Comparative Example 2 (75%) also failed to develop, indicating that excessive cross-linking caused the entire film layer to be insoluble in the developing solution.

[0103] Dosage of photo-alkali-generating agent (Examples 1, 4 vs. Comparative Examples 3, 4, 5): The photo-alkali-generating agent is a "catalyst" for low-temperature curing. Comparative Example 5 (without agent) could not be patterned, demonstrating its necessity. Comparative Example 3 (0.3%) showed extremely low sensitivity (1900 mJ / cm²). 2 The results indicate that the amount of alkali was insufficient to effectively catalyze curing. Comparative Example 4 (4%) showed a sharp deterioration in resolution (115 μm), possibly due to excessive alkali causing severe lateral etching of the pattern during development. Examples 1 and 4 (1% and 2%) achieved excellent resolution (15 μm) while maintaining high sensitivity.

[0104] Alkynyl diamine structure (Examples 1 vs. 5): Example 5 used a different alkynyl diamine (bis(4-aminophenyl)acetylene), whose sensitivity (240 mJ / cm) 2 (150 mJ / cm) worse than Example 1 2 This indicates that 4,4'-(but-1,3-diyne-1,4-diyl)diphenylamine has a better photocrosslinking efficiency.

[0105] 2. The dielectric properties of the polyimide patterns obtained in Examples 1-4 and Comparative Examples 1-5 were tested according to ASTM D150 standard;

[0106] The thermal stability of the polyimide patterns obtained in Examples 1-4 and Comparative Examples 1-5 was tested according to ASTM E1131 standard, and the results are shown in Table 2:

[0107] Table 2

[0108] Tg Dielectric properties Example 1 278 3.16 Example 2 246 3.35 Example 3 265 3.21 Example 4 264 3.17 Example 5 249 3.32 Comparative Example 1 235 3.50 Comparative Example 2 / / Comparative Example 3 245 3.49 Comparative Example 4 254 3.62 Comparative Example 5 200 3.90 Comparative Example 6 226 3.59

[0109] Effect of alkynyl diamine ratio (Examples 1-3 vs. Comparative Examples 1, 6): Thermal stability (Tg): As the alkynyl diamine ratio increased from 5% (Comparative Example 1) to 50% (Example 3), Tg significantly increased from 235°C to 278°C, and then decreased to 265°C. This is because the alkynyl units form a robust three-dimensional network between molecular chains through photocrosslinking, which greatly restricts chain segment movement and thus improves thermal stability. Excessive alkynyl unit content causes an imbalance in molecular chain rigidity and network structure inhomogeneity, leading to decreased thermal stability.

[0110] Dielectric constant: The dielectric constant decreased significantly from 3.50 in Comparative Example 1 to 3.21 in Example 3. The increased crosslinking density reduced the free volume within the polymer and may have suppressed the orientation of polar groups under an electric field, thereby reducing dielectric loss.

[0111] Effect of photoalkali-generating agent (PAG) dosage (Examples 1, 4 vs. Comparative Examples 3, 4): Comparative Example 3 (PAG 0.3%) showed worse Tg (245°C) and dielectric properties (3.49) than Example 1 (PAG 1%) due to incomplete curing. Comparative Example 4 (PAG 4%) may have experienced side reactions or structural defects due to excessive alkali, resulting in decreased material purity or density.

[0112] Key component omissions (Comparative Examples 2 and 5): Comparative Example 5 (without PAG) had the lowest degree of curing due to the inability to achieve low-temperature imidization, resulting in the worst Tg (200℃) and dielectric properties (3.90). Comparative Example 2 (excess alkynyl diamine) could not be patterned, so its properties could not be measured.

[0113] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A low-temperature curing polyimide photoresist, characterized in that, The structure of the polyimide photoresist is shown in formula (I): （I）； Among them, R1 is independently selected , , One of them; R2 is independently selected from or ; R3 is or .

2. The patterning method for low-temperature curing polyimide photoresist as described in claim 1, characterized in that, Includes the following steps: (1) Under the protection of an inert gas, an aromatic dianhydride monomer is added to a solution of a diamine monomer and the reaction is stirred to obtain a polyamic acid solution; the diamine monomer includes a diamine monomer containing an alkynyl group and an aromatic diamine monomer; (2) Add a photo-alkali-generating agent to the polyamic acid solution, mix evenly and then coat it onto the substrate. Remove the solvent, and then complete the imidization reaction by UV curing and heat treatment, so that the photoresist is cured and a polyimide pattern is obtained.

3. The patterning method for low-temperature curing polyimide photoresist according to claim 2, characterized in that, The diamine monomer containing an alkynyl group mentioned in step (1) is selected from one of 4,4'-(but-1,3-diyne-1,4-diyl)diphenylamine, 1,4-bis(3-aminophenyl)butadiyne and bis(4-aminophenyl)acetylene.

4. The patterning method for low-temperature curing polyimide photoresist according to claim 2, characterized in that, The aromatic diamine monomer mentioned in step (1) is selected from 4,4'-diaminodiphenyl ether and 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl.

5. The patterning method for low-temperature curing polyimide photoresist according to claim 2, characterized in that, The aromatic dianhydride monomer mentioned in step (1) is selected from one of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride and hexafluorodianhydride.

6. The patterning method for low-temperature curing polyimide photoresist according to claim 2, characterized in that, In step (1), the diamine monomer containing an alkynyl group accounts for 10-50% of the total amount of the diamine monomer.

7. The patterning method for low-temperature curing polyimide photoresist according to claim 2, characterized in that, The photoalkali-generating agent mentioned in step (2) is selected from 2-nitrobenzyltrimethylammonium hydroxide or bis(4-tert-butylphenyl)iodonium trifluoromethanesulfonate.

8. The patterning method for low-temperature curing polyimide photoresist according to claim 2, characterized in that, The amount of photoalkali-generating agent added in step (2) is 0.5-3 wt% of the mass of the polyamic acid solution.

9. The patterning method for low-temperature curing polyimide photoresist according to claim 2, characterized in that, The heat treatment in step (2) is performed at a temperature of 80-220℃ for 10-60 minutes.

10. The application of the low-temperature curing polyimide photoresist as described in claim 1 in the three-dimensional structure of flexible OLED display substrates, 5G high-frequency packaging, or microfluidic chips.

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