Low-temperature curing high-resolution polyimide photoresist as well as patterning method and application thereof

Abstract

The invention discloses a low-temperature curing high-resolution polyimide photoresist and a patterning method and application thereof, and belongs to the technical field of photoresist, and 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 a diamine monomer with high reaction activity and a diamine monomer with low reaction activity; and (2) adding a photosensitizer and a chemical imidization catalyst into the polyamide acid solution, uniformly mixing, coating a base material with the mixture, removing the solvent, and performing ultraviolet curing development and gradient heating heat treatment to complete an imidization reaction, so that the photoresist is cured, and the high-resolution polyimide pattern is obtained. Through molecular design and process innovation, the photoresist provided by the invention has the advantages of low-temperature curing, high resolution, excellent thermal stability and low dielectric property, the polyimide photoresist can be prepared through low-temperature curing, and meanwhile, the requirements of flexible electronics and high-density packaging are met.

Description

Technical Field

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

[0002] Polyimide (PI), as a high-performance polymer, is widely used in insulating layers and passivation films for microelectronic packaging, flexible displays, and MEMS devices due to its excellent thermal stability (glass transition temperature > 300℃), low dielectric constant (2.5-3.5), and chemical resistance. However, the preparation of traditional polyimide photoresists requires high-temperature thermal imidization (typically > 300℃) to achieve the ring-closed conversion of polyamic acid (PAA) precursors to polyimide. This process can cause thermal damage to heat-sensitive substrates (such as flexible polyester films and organic light-emitting diode substrates), leading to warping, delamination, or device performance degradation. In addition, high-temperature curing also brings high energy consumption and process cost issues, limiting its further application in advanced packaging and flexible electronics.

[0003] To lower the curing temperature, existing technologies attempt to introduce chemical imidization catalysts (such as imidazole compounds) to promote low-temperature ring-closure reactions. However, this faces two bottlenecks: First, the high molecular weight of traditional polyamic acid precursors leads to excessively high solution viscosity, making it difficult to achieve high-resolution photolithography patterning, and residues after development can easily cause defects. Second, chemical imidization reactions are difficult to completely close the ring at low temperatures (<200℃), and residual polyamic acid segments reduce the mechanical strength and moisture resistance of the film. In addition, traditional photosensitizer systems (such as single diazonaphthoquinone) lack sufficient sensitivity at low exposure doses, making it difficult to meet the requirements of high-precision photolithography.

[0004] To address the aforementioned issues, the industry has proposed several improvement solutions, such as: reducing resin viscosity by adding diluents or branched monomers, but this method sacrifices the bulk thermal stability of polyimide; using low-temperature decomposable end-capping agents to control molecular weight, but this method is complex and costly; and developing novel photosensitizers (such as thioxanthone derivatives) to improve sensitivity, but the compatibility of current photosensitizers with polyamic acid and the synergistic effect of catalysts have not yet been fully optimized.

[0005] Therefore, how to provide a polyimide photoresist system that combines low-temperature curing, high resolution, and excellent material properties is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a low-temperature curing high-resolution polyimide photoresist and its patterning method and application.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A low-temperature curing high-resolution polyimide photoresist, the structure of which is shown in formula (I):

[0009]

[0010] (I);

[0011] Wherein, R1 is independently selected from , or One of them;

[0012] R2 is independently selected from , or One of them;

[0013] R3 is selected independently. , or One of them.

[0014] A method for patterning low-temperature curing high-resolution polyimide photoresist includes the following steps:

[0015] (1) Under the protection of an inert gas, an aromatic dianhydride monomer is added to a solution of diamine monomers and the reaction is stirred to obtain a polyamic acid solution; the diamine monomers include highly reactive diamine monomers and low reactive diamine monomers;

[0016] (2) Add photosensitizer and chemical imidization catalyst to the polyamic acid solution, mix evenly to obtain photoresist solution, coat it on substrate, remove solvent, and then complete imidization reaction by UV curing and development and gradient heating heat treatment to obtain high-resolution polyimide pattern.

[0017] Beneficial Effects: This invention significantly improves the overall performance of photosensitive polyimide through multi-dimensional synergistic effects. The use of a combination of high- and low-reactivity diamine monomers achieves precise control and narrow distribution of the polyamic acid molecular weight, laying the foundation for high-resolution patterning. The introduction of a composite photosensitizer and a low-temperature chemical imidization catalyst synergistically ensures high sensitivity and high contrast in the photolithography process, while enabling the imidization ring-closing reaction to be completed at temperatures far lower than traditional thermal imidization. The final gradient heating heat treatment process effectively avoids film defects and internal stress caused by rapid volatilization at high temperatures, ensuring complete imidization while obtaining polyimide patterns with high pattern fidelity, strong adhesion, excellent mechanical properties, and good compatibility with heat-sensitive substrates.

[0018] Preferably, the highly reactive diamine monomer in step (1) is an aromatic diamine selected from one of 4,4'-diaminodiphenyl ether (ODA), p-phenylenediamine (PDA), and 3,3'-diaminodiphenyl sulfone (DDS).

[0019] Preferably, the low-reactivity diamine monomer in step (1) is an aliphatic diamine or a fluorinated aromatic diamine, selected from one of hexafluoromethylene diamine (6FDA), 1,6-hexanediamine (HDA) or 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB).

[0020] Beneficial effects: The present invention selects highly reactive diamine monomers to ensure the molecular weight of polyamic acid, while selecting low reactive diamine monomers can limit the molecular weight of polyamic acid precursors and reduce solution viscosity, which is beneficial to achieving high resolution.

[0021] More preferably, the molar ratio of the highly reactive diamine monomer to the low reactive diamine monomer is 1:(0.1-0.8).

[0022] Beneficial effects: This ratio allows for the introduction of different proportions of rigid and flexible units onto a single molecular chain, enabling fine-tuning of the material's overall properties while maintaining high strength, high heat resistance, and good processability. Insufficient use of highly reactive diamine monomers results in an inadequate amount of propagating monomer, preventing effective polymer chain elongation and ultimately leading to a very low molecular weight polymer with poor film-forming properties, mechanical strength, and thermal stability. Excessive use of highly reactive diamine monomers results in excessively large molecular weights, which is detrimental to achieving high resolution.

[0023] Preferably, the aromatic dianhydride monomer in step (1) is selected from one of pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) or 4,4'-oxobisphthalic anhydride (ODPA).

[0024] More preferably, the molar ratio of the diamine monomer to the aromatic dianhydride monomer is 1:(1-1.05).

[0025] Preferably, the temperature of the stirring reaction in step (1) is 0-20℃ and the time is 12-24h.

[0026] Preferably, the photosensitizer in step (2) is a compound of diazonaphthoquinone sulfonate (DNQ) or its derivatives and a thioxanthone compound (ITX or DETX) in a mass ratio of (50-80):(20-50).

[0027] More preferably, the amount of photosensitizer added is 1-15% of the mass of the polyamic acid solution.

[0028] Beneficial Effects: DNQ derivatives, as the primary photosensitizer, decompose under ultraviolet light, causing changes in solubility, which is fundamental to patterning. ITX / DETX, as highly efficient photosensitizing agents, effectively absorb longer wavelengths of ultraviolet light and transfer energy to DNQ, significantly improving the system's photosensitivity efficiency. This allows for lower exposure doses and higher resolution patterns. This composite ratio ensures extremely high solubility contrast between exposed and unexposed areas in the developer, resulting in sharp edges and clear lines, reducing defects such as etching or residual adhesive. The optimized addition range of 1-15% ensures excellent photosensitivity while avoiding the negative impact of excessive small molecules on the final properties of polyimide (such as heat resistance, mechanical strength, and dielectric properties), achieving a perfect balance between photolithography processability and material reliability.

[0029] Preferably, the chemical imidization catalyst in step (2) is selected from nitrogen-containing heterocyclic compounds, specifically one of imidazole, 2-ethyl-4-methylimidazolium (EMI), or 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU).

[0030] Beneficial effects: These nitrogen-containing heterocyclic compounds can efficiently catalyze the ring-closing reaction of polyamic acid (PAA), allowing the imidization process to be completed at temperatures far lower than thermal imidization (typically >300°C). This significantly reduces internal stress and film warping caused by the mismatch in thermal expansion coefficients between the substrate and the resin at high temperatures, improving the adhesion and smoothness of the film to the substrate. Furthermore, the low-temperature imidization process avoids the risk of pattern deformation or decreased precision due to polymer flow at high temperatures, ensuring that the fine patterns formed by photolithography maintain high fidelity and resolution after curing.

[0031] More preferably, the amount of the chemical imidization catalyst added is 0.1-5% of the mass of the polyamic acid solution.

[0032] Beneficial effects: This low addition level efficiently catalyzes the ring-closure imidization reaction of polyamic acid while avoiding excessive catalyst residue, thus ensuring the excellent electrical insulation and long-term reliability of the final polyimide film. In the low-temperature stage, the catalyst gently promotes most of the cyclization reaction, effectively releasing water molecules and greatly avoiding bubbles and film defects that may be caused by rapid dehydration at high temperatures. Subsequently, in a shorter high-temperature stage, residual imidization is completely completed and residual solvents are removed, ensuring complete polymer curing and obtaining a final product with high heat resistance, low internal stress, and excellent mechanical properties.

[0033] Preferably, the gradient heating heat treatment in step (2) is to heat-treat at 80-150°C for 10-60 minutes, during which the catalyst promotes the ring-closing reaction, and then heat-treat at 180-220°C for 10-30 minutes to complete the residual iminoization.

[0034] Application of a low-temperature curing high-resolution polyimide photoresist in advanced packaging or flexible electronics.

[0035] Compared with the prior art, the present invention has the following advantages and technical effects:

[0036] The photoresist provided by this invention, through molecular design and process innovation, combines low-temperature curing, high resolution, excellent thermal stability, and low dielectric properties. This invention introduces a copolymer of low-reactivity and high-reactivity diamines to limit the molecular weight of the polyamic acid precursor, reducing solution viscosity. Simultaneously, it incorporates an imidazole catalyst and chemical imidization triggered at 80-150℃, replacing traditional thermal cyclization above 300℃, thus reducing substrate thermal damage. Furthermore, the raw materials in this invention are combined with a DNQ-thioxanthone composite photosensitizer, enabling high resolution under ultraviolet light through an acid-catalyzed and free radical synergistic mechanism (DNQ produces acid to promote dissolution, while thioxanthone produces free radicals to enhance crosslinking). The low-temperature two-step curing ensures complete ring closure, enabling low-temperature curing of polyimide photoresist and its patterning processing, while simultaneously meeting the requirements of flexible electronics and high-density packaging. Detailed Implementation

[0037] 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.

[0038] 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.

[0039] Unless otherwise specified, all raw materials used in the embodiments of this invention were purchased through commercial channels;

[0040] Unless otherwise specified, room temperature or normal temperature in the embodiments of the present invention refers to 25±3℃.

[0041] Example 1

[0042] A method for patterning low-temperature curing high-resolution polyimide photoresist includes the following steps:

[0043] (1) Under the protection of an inert gas (such as nitrogen), 4,4'-diaminodiphenyl ether and 3,5-diaminobenzoic acid are dissolved in DMAC solvent at a molar ratio of 1:0.1, and then pyromellitic dianhydride is slowly added, wherein the molar mass of pyromellitic dianhydride is equal to the sum of the molar numbers of 4,4'-diaminodiphenyl ether and 3,5-diaminobenzoic acid. The reaction is then stirred at 20°C for 12 hours to obtain a polyamic acid solution with a solid content of 15%.

[0044] (2) Add 5% by mass of photosensitizer (diazonaphthoquinone sulfonate and 2,4-diethylthioxanthone mixed in a mass ratio of 3:2) to the polyamic acid solution obtained in step (1). Stir in the dark for 0.5 h until the solution is uniformly mixed. Then add 1% (mass ratio of 2-ethyl-4-methylimidazole to polyamic acid solution) of 2-ethyl-4-methylimidazole and stir in the dark for 3 min to obtain a photoresist solution. Degas the photoresist solution under vacuum, coat it onto the substrate, pre-bake it to remove some of the solvent, and then cure and develop it under ultraviolet light. Heat treat it at 90°C for 30 min to allow the catalyst to promote the closed-ring reaction. Then treat it at 220°C for 30 min to complete the residual imidization and cure the photoresist to obtain a high-resolution polyimide pattern.

[0045] Example 2

[0046] A method for patterning high-resolution polyimide photoresist with low-temperature curing, differing from Example 1 only in that the molar ratio of 4,4'-diaminodiphenyl ether to 3,5-diaminobenzoic acid is 1:0.4, specifically including the following steps:

[0047] (1) Under the protection of an inert gas (such as nitrogen), 4,4'-diaminodiphenyl ether and 3,5-diaminobenzoic acid are dissolved in DMAC solvent at a molar ratio of 1:0.4, and then pyromellitic dianhydride is slowly added, wherein the molar mass of pyromellitic dianhydride is equal to the sum of the molar numbers of 4,4'-diaminodiphenyl ether and 3,5-diaminobenzoic acid. The reaction is then stirred at 20°C for 12 hours to obtain a polyamic acid solution with a solid content of 15%.

[0048] (2) Add 5% (by mass) of photosensitizer (diazonaphthoquinone sulfonate and 2,4-diethylthioxanthone mixed in a mass ratio of 3:2) to the polyamic acid solution obtained in step (1). Stir in the dark for 0.5 h until the solution is uniformly mixed. Then add 1% (by mass ratio of 2-ethyl-4-methylimidazole to the polyamic acid solution) of 2-ethyl-4-methylimidazole and stir in the dark for 3 min to obtain a photoresist solution. Degas the photoresist solution under vacuum, coat it onto the substrate, pre-bake to remove some solvent, then cure and develop it under ultraviolet light. Heat treat it at 90°C for 30 min to allow the catalyst to promote the ring-closing reaction. Finally, treat it at 220°C for 30 min to complete the residual imidization, thereby curing the photoresist and obtaining a high-resolution polyimide pattern.

[0049] Example 3

[0050] A method for patterning high-resolution polyimide photoresist with low-temperature curing, differing from Example 1 only in that the molar ratio of 4,4'-diaminodiphenyl ether to 3,5-diaminobenzoic acid is 1:0.8, specifically including the following steps:

[0051] (1) Under the protection of an inert gas (such as nitrogen), 4,4'-diaminodiphenyl ether and 3,5-diaminobenzoic acid are dissolved in DMAC solvent at a molar ratio of 1:0.8, and then pyromellitic dianhydride is slowly added, wherein the molar mass of pyromellitic dianhydride is equal to the sum of the molar numbers of 4,4'-diaminodiphenyl ether and 3,5-diaminobenzoic acid. The reaction is then stirred at 20°C for 12 hours to obtain a polyamic acid solution with a solid content of 15%.

[0052] (2) Add 5% by mass of photosensitizer (diazonaphthoquinone sulfonate and 2,4-diethylthioxanthone mixed in a mass ratio of 3:2) to the polyamic acid solution obtained in step (1). Stir in the dark for 0.5 h until the solution is uniformly mixed. Then add 1% (mass ratio of 2-ethyl-4-methylimidazole to polyamic acid solution) of 2-ethyl-4-methylimidazole and stir in the dark for 3 min to obtain a photoresist solution. Degas the photoresist solution under vacuum, coat it onto the substrate, pre-bake it to remove some of the solvent, and then cure and develop it under ultraviolet light. Heat treat it at 90°C for 30 min to allow the catalyst to promote the closed-ring reaction. Then treat it at 220°C for 30 min to complete the residual imidization and cure the photoresist to obtain a high-resolution polyimide pattern.

[0053] Example 4

[0054] A method for patterning high-resolution polyimide photoresist with low-temperature curing, differing from Example 3 only in that the amount of photosensitizer added is 10% of the mass of the polyamic acid solution, specifically including the following steps:

[0055] (1) Under the protection of an inert gas (such as nitrogen), 4,4'-diaminodiphenyl ether and 3,5-diaminobenzoic acid are dissolved in DMAC solvent at a molar ratio of 1:0.8, and then pyromellitic dianhydride is slowly added, wherein the molar mass of pyromellitic dianhydride is equal to the sum of the molar numbers of 4,4'-diaminodiphenyl ether and 3,5-diaminobenzoic acid. The reaction is then stirred at 20°C for 12 hours to obtain a polyamic acid solution with a solid content of 15%.

[0056] (2) Add 10% of the photosensitizer (diazonaphthoquinone sulfonate and 2,4-diethylthioxanthone mixed in a mass ratio of 3:2) to the polyamic acid solution obtained in step (1). Stir in the dark for 0.5 h until the solution is uniformly mixed. Then add 1% (mass ratio of 2-ethyl-4-methylimidazole to polyamic acid solution) of 2-ethyl-4-methylimidazole and stir in the dark for 3 min to obtain a photoresist solution. Degas the photoresist solution under vacuum, coat it onto the substrate, pre-bake it to remove some of the solvent, and then cure and develop it under ultraviolet light. Heat treat it at 90°C for 30 min to allow the catalyst to promote the closed-ring reaction. Then treat it at 220°C for 30 min to complete the residual imidization and cure the photoresist to obtain a high-resolution polyimide pattern.

[0057] Comparative Example 1

[0058] The only difference from Example 1 is that 3,5-diaminobenzoic acid is not added, and the specific steps include:

[0059] (1) Under the protection of an inert gas (such as nitrogen), 4,4'-diaminodiphenyl ether is dissolved in DMAC solvent, and then pyromellitic dianhydride is slowly added, wherein the molar ratio of pyromellitic dianhydride to 4,4'-diaminodiphenyl ether is 1:1. The reaction is then stirred at 20°C for 12 hours to obtain a polyamic acid solution with a solid content of 15%.

[0060] (2) Add 5% by mass of photosensitizer (diazonaphthoquinone sulfonate and 2,4-diethylthioxanthone mixed in a mass ratio of 3:2) to the polyamic acid solution obtained in step (1), stir in the dark for 0.5 h until the solution is uniformly mixed, then add 1% (mass ratio of 2-ethyl-4-methylimidazole to polyamic acid solution) of 2-ethyl-4-methylimidazole, stir in the dark for 3 min to obtain photoresist solution, degas the photoresist solution under vacuum, coat it on the substrate, pre-bake to remove some solvent, then cure and develop by ultraviolet light, heat treat at 90℃ for 30 min to allow the catalyst to promote the ring-closing reaction; then treat at 220℃ for 30 min to complete the residual imidization and obtain patterned polyimide.

[0061] Comparative Example 2

[0062] The only difference from Example 1 is that diazonoquinone sulfonate is not added in step (2), which includes the following steps:

[0063] (1) Under the protection of an inert gas (such as nitrogen), 4,4'-diaminodiphenyl ether and 3,5-diaminobenzoic acid are dissolved in DMAC solvent at a molar ratio of 1:0.1, and then pyromellitic dianhydride is slowly added, wherein the molar mass of pyromellitic dianhydride is equal to the sum of the molar numbers of 4,4'-diaminodiphenyl ether and 3,5-diaminobenzoic acid. The reaction is then stirred at 20°C for 12 hours to obtain a polyamic acid solution with a solid content of 15%.

[0064] (2) Add 5% by mass of 2,4-diethylthioxanthone to the polyamic acid solution obtained in step (1), stir in the dark for 0.5 h until the solution is mixed evenly, then add 1% (mass ratio of 2-ethyl-4-methylimidazolium to polyamic acid solution) of 2-ethyl-4-methylimidazolium, stir in the dark for 3 min to obtain a photoresist solution, degas the photoresist solution under vacuum, coat it onto the substrate, pre-bake it to remove some of the solvent, then cure and develop it under ultraviolet light, heat treat it at 90°C for 30 min to allow the catalyst to promote the ring-closing reaction; then treat it at 220°C for 30 min to complete the residual imidization and obtain patterned polyimide.

[0065] Comparative Example 3

[0066] The only difference from Example 1 is that 2,4-diethylthioxanthonone is not added in step (2), and the specific steps include:

[0067] (1) Under the protection of an inert gas (such as nitrogen), 4,4'-diaminodiphenyl ether and 3,5-diaminobenzoic acid are dissolved in DMAC solvent at a molar ratio of 1:0.1, and then pyromellitic dianhydride is slowly added, wherein the molar mass of pyromellitic dianhydride is equal to the sum of the molar numbers of 4,4'-diaminodiphenyl ether and 3,5-diaminobenzoic acid. The reaction is then stirred at 20°C for 12 hours to obtain a polyamic acid solution with a solid content of 15%.

[0068] (2) Add 5% of the polyamic acid solution mass of diazonium naphthoquinone sulfonate to the polyamic acid solution obtained in step (1), stir in the dark for 0.5 h until the solution is mixed evenly, then add 1% (mass ratio of 2-ethyl-4-methylimidazolium to polyamic acid solution) of 2-ethyl-4-methylimidazolium, stir in the dark for 3 min to obtain a photoresist solution, degas the photoresist solution under vacuum, coat it onto the substrate, pre-bake it to remove some of the solvent, then cure and develop it under ultraviolet light, heat treat it at 90°C for 30 min to allow the catalyst to promote the ring-closing reaction; then treat it at 220°C for 30 min to complete the residual imidization and obtain patterned polyimide.

[0069] Comparative Example 4

[0070] The only difference from Example 1 is that diazonaphthoquinone sulfonate and 2,4-diethylthioxanthonone are not added in step (2), and the specific steps include:

[0071] (1) Under the protection of an inert gas (such as nitrogen), 4,4'-diaminodiphenyl ether and 3,5-diaminobenzoic acid are dissolved in DMAC solvent at a molar ratio of 1:0.1, and then pyromellitic dianhydride is slowly added, wherein the molar mass of pyromellitic dianhydride is equal to the sum of the molar numbers of 4,4'-diaminodiphenyl ether and 3,5-diaminobenzoic acid. The reaction is then stirred at 20°C for 12 hours to obtain a polyamic acid solution with a solid content of 15%.

[0072] (2) Add 1% (mass ratio of 2-ethyl-4-methylimidazole to polyamic acid solution) of 2-ethyl-4-methylimidazole to the polyamic acid solution obtained in step (1), stir for 3 min in the dark to obtain photoresist solution, degas the photoresist solution under vacuum, coat it on the substrate, pre-bake to remove some solvent, then cure and develop by ultraviolet light, heat treat at 90 °C for 30 min to allow the catalyst to promote the ring-closing reaction; then treat at 220 °C for 30 min to complete the residual imidization and obtain patterned polyimide.

[0073] Comparative Example 5

[0074] The only difference from Example 1 is that 2-ethyl-4-methylimidazole is not added in step (2), and the specific steps include:

[0075] (1) Under the protection of an inert gas (such as nitrogen), 4,4'-diaminodiphenyl ether and 3,5-diaminobenzoic acid are dissolved in DMAC solvent at a molar ratio of 1:0.1, and then pyromellitic dianhydride is slowly added, wherein the molar mass of pyromellitic dianhydride is equal to the sum of the molar numbers of 4,4'-diaminodiphenyl ether and 3,5-diaminobenzoic acid. The reaction is then stirred at 20°C for 12 hours to obtain a polyamic acid solution with a solid content of 15%.

[0076] (2) Add 5% by mass of photosensitizer (diazonaphthoquinone sulfonate and 2,4-diethylthioxanthone mixed in a mass ratio of 3:2) to the polyamic acid solution obtained in step (1), stir in the dark for 0.5 h until the solution is uniformly mixed to obtain a photoresist solution, degas the photoresist solution under vacuum, coat it onto the substrate, pre-bake it to remove some of the solvent, then cure and develop it under ultraviolet light, heat treat it at 90°C for 30 minutes to allow the catalyst to promote the ring-closing reaction; then treat it at 220°C for 30 minutes to complete the residual imidization and obtain patterned polyimide.

[0077] Comparative Example 6

[0078] The only difference from Example 1 is that step (2) involves a solidification step, which specifically includes the following steps:

[0079] (1) Under the protection of an inert gas (such as nitrogen), 4,4'-diaminodiphenyl ether and 3,5-diaminobenzoic acid are dissolved in DMAC solvent at a molar ratio of 1:0.1, and then pyromellitic dianhydride is slowly added, wherein the molar mass of pyromellitic dianhydride is equal to the sum of the molar numbers of 4,4'-diaminodiphenyl ether and 3,5-diaminobenzoic acid. The reaction is then stirred at 20°C for 12 hours to obtain a polyamic acid solution with a solid content of 15%.

[0080] (2) Add 5% by mass of photosensitizer (diazonaphthoquinone sulfonate and 2,4-diethylthioxanthone mixed in a mass ratio of 3:2) to the polyamic acid solution obtained in step (1), stir in the dark for 0.5 h until the solution is mixed evenly, then add 1% (mass ratio of 2-ethyl-4-methylimidazole to polyamic acid solution) of 2-ethyl-4-methylimidazole, stir in the dark for 3 min to obtain photoresist solution, degas the photoresist solution under vacuum, coat it on the substrate, pre-bake to remove some solvent, then cure and develop it under ultraviolet light, and treat it at 220℃ for 1 h to complete residual imidization and obtain patterned polyimide.

[0081] Technical effects:

[0082] 1. The sensitivity, resolution (line width), and resolution (line spacing) of the polyimide photoresists obtained in Examples 1-4 and Comparative Examples 1-3 were tested according to SEMI standards. The results are shown in Table 1:

[0083] Table 1

[0084] <![CDATA[Sensitivity (mJ•cm -2 ).]]> Resolution (line width) (um) Resolution (line spacing) (um) Example 1 430 33 10 Example 2 290 25 9 Example 3 180 19 7 Example 4 70 17 6 Comparative Example 1 960 65 34 Comparative Example 2 Unable to develop Unable to be patterned Unable to be patterned Comparative Example 3 Unable to develop Unable to be patterned Unable to be patterned Comparative Example 4 Unable to develop Unable to be patterned Unable to be patterned Comparative Example 5 430 45 20 Comparative Example 6 430 39 18

[0085] In this invention, the polyimide photoresist utilizes the energy provided by light to display patterns. The wider the lines and the larger the line spacing in the pattern, the blurrier the pattern and the worse the effect. That is, the smaller the resolution (line width) and resolution (line spacing) values ​​in Table 1, the higher the resolution and the clearer the pattern. As can be seen from Table 1, compared to Comparative Examples 1-4, the photoresist obtained in this invention has significantly improved sensitivity and resolution. In particular, the photoresist obtained in Example 4 has a sensitivity of only 70 mJ•cm. -2 The resolution (line width) is 17μm, and the resolution (line spacing) is 6μm.

[0086] 2. Thermal stability

[0087] The thermal stability of the polyimide photoresists obtained in Examples 1-4 and Comparative Examples 1-6 was tested according to ASTM E1131 standard, and the results are shown in Table 2.

[0088] Table 2

[0089] Thermal stability Tg (°C) Example 1 311 Example 2 314 Example 3 322 Example 4 323 Comparative Example 1 294 Comparative Example 2 310 Comparative Example 3 310 Comparative Example 4 310 Comparative Example 5 243 Comparative Example 6 282

[0090] Comparing Examples 1-3 with Comparative Example 1, it can be seen that as the proportion of carboxylated diamine monomer increases from 0 to 0.8, the temperature gradient (Tg) continuously rises from 294°C to 322°C. This is attributed to the dehydration condensation reaction of the carboxyl groups during high-temperature curing, forming additional ester bonds between the polyimide backbone, significantly enhancing the binding between molecular chains, thereby greatly increasing the Tg. Comparative Example 1 (without carboxyl groups) has the lowest Tg (294°C), confirming the importance of this cross-linking structure. The Tg of Comparative Example 5 (without catalyst 2-ethyl-4-methylimidazolium) drops sharply to 243°C, demonstrating that the catalyst can significantly reduce the activation energy of the imidization reaction, which is a necessary condition to ensure the efficient conversion of polyamic acid into thermally stable polyimide. The absence of photosensitizers (Comparative Examples 2-4) has little effect on the final Tg, indicating that they mainly affect the photolithography process and do not determine the final thermal properties.

[0091] 3. Dielectric properties

[0092] The dielectric properties of the polyimide photoresists obtained in Examples 1-4 and Comparative Examples 1-6 were tested according to ASTM D150 standard, and the results are shown in Table 3.

[0093] Table 3

[0094] Dielectric properties Example 1 3.1 Example 2 3.1 Example 3 3.0 Example 4 3.0 Comparative Example 1 3.5 Comparative Example 2 3.0 Comparative Example 3 3.0 Comparative Example 4 3.0 Comparative Example 5 5.6 Comparative Example 6 3.7

[0095] The dielectric constant (Dk) of all carboxyl-containing monomers in Examples (1-4) and Comparative Examples (2-4) (3.0-3.1) was significantly lower than that of Comparative Example 1 (Dk=3.5) which did not contain carboxyl groups. This is because the ester crosslinking network formed by the high-temperature condensation of carboxyl groups enhances the packing density between molecular chains, reduces the degrees of freedom of movement of polar groups (such as uncyclized ammonium acids) and the free volume in the material, thereby effectively reducing the polarizability and causing a decrease in Dk. The Dk of Comparative Example 5 (without catalyst) was as high as 5.6, demonstrating that incomplete imidization led to a sharp increase in dielectric constant. This highlights the indispensability of the catalyst, which ensures the complete conversion to the polyimide structure.

[0096] 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 high-resolution polyimide photoresist, characterized in that, The structure of the high-resolution polyimide photoresist is shown in formula (I): ； Wherein, R1 is independently selected from , or One of them; R2 is independently selected from , or One of them; R3 is selected independently. , or One of them.

2. The patterning method for low-temperature curing high-resolution 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 diamine monomers and the reaction is stirred to obtain a polyamic acid solution; the diamine monomers include highly reactive diamine monomers and low reactive diamine monomers; (2) Add photosensitizer and chemical imidization catalyst 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 development and gradient heating heat treatment, so that the photoresist is cured and a high-resolution polyimide pattern is obtained.

3. The patterning method for low-temperature curing high-resolution polyimide photoresist according to claim 2, characterized in that, The highly reactive diamine monomer in step (1) is selected from one of 4,4'-diaminodiphenyl ether, p-phenylenediamine and 3,3'-diaminodiphenyl sulfone; and / or, the low-reactivity diamine monomer is selected from one of 3,5-diaminobenzoic acid, 2,4-diaminotoluene or 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl.

4. The patterning method for low-temperature curing high-resolution polyimide photoresist according to claim 2, characterized in that, The molar ratio of the highly reactive diamine monomer to the low reactive diamine monomer in step (1) is 1: (0.1~0.8).

5. The patterning method for low-temperature curing high-resolution 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 or 4,4'-oxobisphthalic anhydride.

6. The patterning method for low-temperature curing high-resolution polyimide photoresist according to claim 2, characterized in that, The temperature of the stirring reaction in step (1) is 0-20℃ and the time is 12-24h.

7. The patterning method for low-temperature curing high-resolution polyimide photoresist according to claim 2, characterized in that, The photosensitizer mentioned in step (2) is obtained by combining diazonaphthoquinone sulfonate or its derivative with a thioxanthone compound in a mass ratio of (50-80):(20-50).

8. The patterning method for low-temperature curing high-resolution polyimide photoresist according to claim 2, characterized in that, The chemical imidization catalyst mentioned in step (2) is selected from nitrogen-containing heterocyclic compounds, specifically one of imidazole, 2-ethyl-4-methylimidazolium, or 1,8-diazabicyclo[5.4.0]undec-7-ene.

9. The patterning method for low-temperature curing high-resolution polyimide photoresist according to claim 2, characterized in that, The gradient heating heat treatment in step (2) involves heat treatment at 80-150℃ for 10-60 minutes, followed by heating to 180-220℃ for 10-30 minutes.

10. The application of the low-temperature curing high-resolution polyimide photoresist as described in claim 1 in the fields of advanced packaging or flexible electronics.

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