A method for preparing a negative photoresist patterned film layer

Abstract

The present invention discloses a method for preparing a negative photoresist patterned film layer, which relates to the technical field of photoresist materials. The preparation method includes the following steps: Step 1: The epitaxial wafer is successively subjected to pickling, hydrogen peroxide washing, and pure water washing to obtain a pretreated epitaxial wafer; Step 2: A negative photoresist is spin-coated on the surface of the pretreated epitaxial wafer; soft baking is carried out, and exposure treatment is carried out under the shielding of a mask plate to transfer the pattern onto the pretreated epitaxial wafer; development treatment, pure water washing, and nitrogen drying are carried out to obtain a negative photoresist patterned film layer. The raw materials of the negative photoresist include the following components: by mass, 22 to 26 parts of photosensitive polyimide, 4 to 6 parts of POSS-based branched polyimide, 10 to 12 parts of mercapto monomer, 3 to 4 parts of initiator, and 108 to 132 parts of organic solvent. In this application, by optimizing the components, soft baking, and exposure processes, the quality of the negative photoresist patterned film layer is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of photoresist materials, and specifically to a method for preparing a negative photoresist patterned film layer. Background Art

[0002] Lithography technology is one of the key technologies in semiconductor manufacturing; generally, the pattern on the mask plate is transferred to the substrate through a photoresist, realizing the basis for the manufacture of microelectronic devices and integrated circuits. Photoresists are generally divided into positive photoresists and negative photoresists. After being exposed, the negative photoresist cures and crosslinks in the exposed area, and the unexposed area is dissolved by the developer, complementary to the pattern on the mask plate.

[0003] In the prior art, polyimide is often used in negative photoresists due to its excellent mechanical properties and electrical insulation. In general processes, in order to improve the mechanical properties and metal adhesion of negative photoresists, additives such as nanoparticles and corrosion inhibitors are usually introduced; and due to the need for photocuring, photoinitiators are inevitably introduced; the introduction of these additives will cause problems such as dispersibility, compatibility with the main resin, and small molecule mobility, resulting in defects such as poor curing efficiency, uneven curing, large curing stress, and large curing shrinkage during the exposure process of negative photoresists, affecting the quality of patterning and performance such as pattern resolution. In addition, if the curing is uneven or incomplete, it will corrode the exposed area during development, resulting in a reduction in the quality of the negative photoresist patterned film layer.

[0004] In summary, to solve the above problems, it is of great significance to prepare a negative photoresist patterned film layer. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing a negative photoresist patterned film layer to solve the problems raised in the above background art.

[0006] To solve the above technical problems, the present invention provides the following technical solutions:

[0007] A method for preparing a negative photoresist patterned film layer, comprising the following steps:

[0008] Step 1: Sequentially subject the epitaxial wafer to pickling, hydrogen peroxide washing, and pure water washing to obtain a pretreated epitaxial wafer;

[0009] Step 2: Spin-coat a negative photoresist on the surface of the pretreated epitaxial wafer; perform soft baking, expose it under the shielding of a mask plate to transfer the pattern to the pretreated epitaxial wafer; perform development treatment, pure water washing, and nitrogen drying to obtain a negative photoresist patterned film layer.

[0010] Among them, during the pickling process, it is soaked in sulfuric acid at room temperature for 30 to 60 minutes; during the hydrogen peroxide washing process, it is soaked in hydrogen peroxide at a temperature of 50 to 60 °C for 8 to 10 minutes. The purpose of the pretreatment process is to remove the residual contaminants on the surface of the epitaxial wafer.

[0011] Preferably, the raw materials of the negative photoresist include the following components: by mass, 22 to 26 parts of photosensitive polyimide, 4 to 6 parts of POSS-based branched polyimide, 10 to 12 parts of mercapto monomer, 3 to 4 parts of initiator, and 108 to 132 parts of organic solvent.

[0012] Preferably, the preparation method of the POSS-based branched polyimide includes the following steps:

[0013] S1-1: Add diamine monomer and octa(aminophenyl) POSS to N-methylpyrrolidone and stir for 0.5 to 1 hour to obtain solution A; add pyromellitic dianhydride and 4-ethynylphthalic anhydride to N-methylpyrrolidone and stir for 0.5 to 1 hour to obtain solution B;

[0014] S1-2: Mix solution A and solution B and stir for 4 to 6 hours; heat up to 60 to 65 °C and stir for 2 to 4 hours; add toluene, heat up to 180 to 185 °C and stir to react for 10 to 12 hours, evaporate toluene, stop heating after the reaction system reaches 200 °C, and perform post-treatment to obtain POSS-based branched polyimide.

[0015] Preferably, the raw materials of the POSS-based branched polyimide include the following substances: by mass, 10 parts of octa(aminophenyl) POSS, 36 to 40 parts of diamine monomer, 15 to 20 parts of pyromellitic dianhydride, 12 to 18 parts of 4-ethynylphthalic anhydride, 10 to 15 parts of toluene, and 600 to 650 parts of N-methylpyrrolidone.

[0016] Preferably, the preparation method of the diamine monomer is: (1) Under an inert gas, add pyridine-2,6-dicarboxaldehyde and 4-vinyl aniline with a molar ratio of 1:2 to ethanol in sequence, stir and react at 58 to 60 °C for 4 to 6 hours, and perform post-treatment to obtain a divinyl monomer; (2) Add the divinyl monomer and cysteamine with a mass ratio of 1:0.65 to 0.7 to tetrahydrofuran, add azobisisobutyronitrile; under ultraviolet light irradiation, set the light irradiance to 100 to 150 mW / cm 2 , stir and react for 2 to 4 hours, and perform post-treatment to obtain the diamine monomer.

[0017] Preferably, the preparation method of the initiator includes the following steps:

[0018] S2-1: Mix the divinyl monomer, acrylamide, allyl succinic anhydride, and 2-hydroxyethyl methacrylate evenly to obtain a mixed monomer; add silica and 3-(Trimethoxysilyl)propyl methacrylate to an ethanol aqueous solution of 5-10 wt%, and disperse evenly by ultrasonic treatment; add the mixed monomer and azobisisobutyronitrile, and react at 70-75 °C for 3-5 hours, followed by post-treatment to obtain composite silica;

[0019] S2-2: Under light avoidance, add the composite silica to tetrahydrofuran, and add chlorothioxanthone and 4-chlorobenzophenone; under an inert gas, stir at 50-55 °C for 5-6 hours, add acryloyl chloride and hydroquinone and continue stirring for 10-12 hours; perform post-treatment to obtain an initiator.

[0020] Preferably, the raw materials of the composite silica include the following components: by mass, 10 parts of silica, 10-15 parts of divinyl monomer, 10-15 parts of acrylamide, 4-5 parts of allyl succinic anhydride, 4-5 parts of 2-hydroxyethyl methacrylate, 1-2 parts of 3-(Trimethoxysilyl)propyl methacrylate, and 0.1-0.5 parts of azobisisobutyronitrile;

[0021] The raw materials of the initiator include the following components: by mass, 10 parts of composite silica, 0.5-0.6 parts of chlorothioxanthone, 0.5-0.6 parts of 4-chlorobenzophenone, 0.8-1 part of acryloyl chloride, and 0.04-0.05 parts of hydroquinone.

[0022] Preferably, during the soft baking process, under an inert gas, bake at 80-85 °C for 15-30 minutes.

[0023] Preferably, during the exposure process, use a contact exposure machine with a power of 15-20 mW / cm 2 , an exposure time of 15-20 s, and a total exposure dose of 300-400 mJ.

[0024] Preferably, during the development process, the developer is an aqueous solution of tetramethylammonium hydroxide of 0.5-1.5 wt%.

[0025] Compared with the prior art, the beneficial effects of the present invention are: by introducing POSS-based branched polyimide, while enhancing crosslinking and heat resistance, promoting the adhesion of subsequent metals; synergistically compounding and modifying the initiator to improve the uniformity of photocuring and the photopolymerization rate; combining the subsequent soft baking and exposure processes to effectively buffer the curing stress and reduce the curing shrinkage of the film layer. Thus, comprehensively improving the quality of the negative photoresist patterned film layer.

[0026] In the solution, the POSS-based branched polyimide uses octa(aminophenyl) POSS as the branchable center, uses diamine monomers and pyromellitic dianhydride as the basic reaction segments, and is prepared by using 4-ethynylphthalic anhydride for end-capping. Among them, due to the introduction of the Si-O bond and its special structure in POSS, the mechanical properties, thermal stability, etching resistance and adhesion of the patterned film layer are effectively improved, and its reliability in the semiconductor manufacturing process is effectively improved. At the same time, the introduction of POSS can increase the photopolymerization rate and exotherm, and the photosensitivity, and can reduce the situation of incomplete curing.

[0027] Among them, in order to graft POSS to form a branched polyimide, not only the compatibility between POSS and the main photosensitive polyimide is improved; the end-capped unsaturated bonds effectively increase the crosslinking property; at the same time, due to its branched structure, the toughness of the film layer is improved, and the curing stress can be effectively buffered, and the curing shrinkage is reduced, thereby enhancing the patterning quality; and the branched structure also improves the interfacial adhesion and intermolecular cohesion, thereby effectively improving the interfacial bonding property between the patterned film layer and the epitaxial wafer.

[0028] Among them, the diamine monomer is based on pyridine-2,6-dicarboxaldehyde. First, the aldehyde group reacts with the amino group to form a divinyl monomer, and then cysteamine is grafted by the reaction of the alkenyl group with the mercapto group. Among them, the pyridine group not only improves the thermal stability, but also improves the adhesion to the subsequent metal due to its ability to coordinate with metal ions. The grafted cysteamine contains sulfur-containing groups and short carbon chains, which can buffer the curing stress, thereby reducing the curing shrinkage.

[0029] In the solution, in order to inhibit the migration of common small molecule initiators and reduce curing non-uniformity and incomplete curing. In the solution, divinyl monomers, acrylamide, allyl succinic anhydride, and 2-hydroxyethyl methacrylate are copolymerized as monomers, and silica modified with methacryloxypropyltrimethoxysilane is introduced therein to form composite silica, and the amino group contained on its surface is used to first graft chlorothioxanthone and 4-chlorobenzophenone; then acryloyl chloride is grafted to obtain. Among them, chlorothioxanthone and 4-chlorobenzophenone are small molecule initiators. The initiator modified in this way can effectively inhibit the migration of small molecules and improve the curing performance. On the other hand, the contained silica can also produce Rayleigh scattering effect; promote photocuring; at the same time, the initiator can crosslink with the main substance; generate reaction compatibility; and the contained divinyl monomer has a similar chain segment to the diamine monomer in the POSS-based branched polyimide, generating similar compatibility; in turn, the initiator can be evenly dispersed in the film layer, effectively improving the curing efficiency and curing uniformity, thereby improving the quality of the patterned film layer.

[0030] In the solution, after soft baking, the negative photoresist can be attached to the surface of the epitaxial wafer as the coating fastness. By optimizing the exposure method, the diffusion distance of free radicals can be effectively increased, thereby improving the crosslinking degree, increasing the film retention rate, and thus improving the patterning quality. On the other hand, when developing in an alkaline solution, since the negative photoresist contains acid anhydride groups and has a degradation ability, the cured photoresist can be completely dissolved in the alkaline developer, and the ring is opened in the molecular structure to compensate for the volume shrinkage, which can effectively increase the quality of the patterned film layer. Specific embodiments

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0032] It should be noted that the following parts are by mass. There are no special restrictions on the purchase manufacturers of all the raw materials involved in the present invention. Exemplarily, including: in the following embodiments, the CAS number of 4,4-(but-1,3-diyne-1,4-diyl)dianiline is 30405-78-8; the CAS number of 4,4-diaminodiphenyl ether is 101-80-4; the CAS number of pyridine-2,6-dicarbaldehyde is 5431-44-7; the CAS number of 4-ethenylaniline is 1520-21-4; the CAS number of cysteamine is 60-23-1; the CAS number of pyromellitic dianhydride is 89-32-7; the CAS number of octaphenylaminopropyl POSS is 518359-82-5; the CAS number of acrylamide is 79-06-1; the CAS number of methacryloxypropyltrimethoxysilane is 2530-85-0; the CAS number of allyl succinic anhydride is 7539-12-0; the CAS number of 4-chlorobenzophenone is 134-85-0. The above-mentioned and other raw materials involved are all commercially available.

[0033] Preparation of chlorothioxanthone: (1) Thiosalicylic acid and phenoxyacetic acid with a molar ratio of 1:1.1 are sequentially added to toluene, and p-toluenesulfonic acid is added, and the mixture is stirred and reacted at 110 °C for 10 hours; the solvent is distilled off, and post-treatment is carried out to obtain carboxythioxanthone; (2) Carboxythioxanthone is added to a mixed solvent of thionyl chloride and dimethylformamide, and the mass ratio of thionyl chloride to dimethylformamide is 20:1, and the mixture is stirred at 70 °C for 18 hours, and post-treatment is carried out to obtain chlorothioxanthone;

[0034] Preparation of diamine monomer: (1) Under an inert gas, pyridine-2,6-dicarboxaldehyde and 4-vinyl aniline with a molar ratio of 1:2 were successively added to ethanol, and the mixture was stirred at 60 °C for 5 hours. After post-treatment, a divinyl monomer was obtained; (2) The divinyl monomer and cysteamine with a mass ratio of 1:0.68 were added to tetrahydrofuran, and azobisisobutyronitrile (0.5 wt% of the divinyl monomer) was added. Under ultraviolet light irradiation, the light irradiance was set to 120 mW / cm 2 , and the mixture was stirred for 4 hours. After post-treatment, a diamine monomer was obtained.

[0035] Preparation of photosensitive polyimide: Under a nitrogen atmosphere, 14 parts of 4,4-diaminodiphenyl ether and 8 parts of 4,4-(but-1,3-diyne-1,4-diyl)dianiline were added to 200 parts of N-methylpyrrolidone, and 22 parts of pyromellitic dianhydride and 7 parts of 4-ethynylphthalic anhydride were added. The mixture was stirred in an ice-water bath for 12 hours, a quinoline catalyst was added, and the temperature was raised to 190 °C and stirred for 5 hours. During the process, water removed by imidization was carried out by nitrogen. After cooling to room temperature, it was poured into absolute ethanol, washed and dried to obtain a photosensitive polyimide.

[0036] Preparation of POSS-based branched polyimide: S1-1: 38 parts of diamine monomer and 10 parts of octaphenylamino POSS were added to 300 parts of N-methylpyrrolidone and stirred for 1 hour to obtain solution A; 19 parts of pyromellitic dianhydride and 15 parts of 4-ethynylphthalic anhydride were added to 350 parts of N-methylpyrrolidone and stirred for 1 hour to obtain solution B; S1-2: Solution A and solution B were mixed and stirred for 5 hours; the temperature was raised to 60 °C and stirred for 4 hours; 15 parts of toluene were added, and the temperature was raised to 180 °C and stirred for 10 hours. Toluene was distilled off, and heating was stopped after the reaction system reached 200 °C. After post-treatment, a POSS-based branched polyimide was obtained.

[0037] Preparation of initiator: S2-1: 15 parts of divinyl monomer, 12 parts of acrylamide, 5 parts of allyl succinic anhydride, and 5 parts of 2-hydroxyethyl methacrylate were mixed evenly to obtain a mixed monomer; 10 parts of silica and 1.5 parts of methacryloxypropyltrimethoxysilane were added to a 5 wt% ethanol aqueous solution and ultrasonically dispersed evenly; the mixed monomer and 0.2 parts of azobisisobutyronitrile were added, and the reaction was carried out at 70 °C for 4 hours. After post-treatment, a composite silica was obtained; S2-2: Under light protection, 10 parts of the composite silica were added to 50 parts of tetrahydrofuran, and 0.4 parts of chlorothioxanthone and 0.6 parts of 4-chlorobenzophenone were added. Under a nitrogen gas atmosphere, the mixture was stirred at 50 °C for 6 hours, 1 part of acryloyl chloride and 0.05 parts of hydroquinone were added and stirred for another 12 hours; after post-treatment, an initiator was obtained.

[0038] Example 1: A method for preparing a negative photoresist patterned film layer includes the following steps:

[0039] Step 1: Immerse the epitaxial wafer in sulfuric acid at room temperature for 40 minutes; transfer it to hydrogen peroxide and immerse it at 55 °C for 8 minutes; wash it clean with pure water to obtain a pretreated epitaxial wafer.

[0040] Step 2: (1) Add 24 parts of photosensitive polyimide, 5 parts of POSS-based branched polyimide, 11 parts of pentaerythritol tetra-3-mercaptopropionate, and 3 parts of initiator to 120 parts of N-methylpyrrolidone in sequence and mix evenly to obtain a negative photoresist; (2) Spin-coat the negative photoresist on the surface of the pretreated epitaxial wafer; bake it at 80 °C for 20 minutes, and perform exposure treatment under the shielding of a mask. During the process: Use a contact exposure machine with a power of 18 mW / cm 2 , an exposure time of 18 s, an exposure dose of 350 mJ, and transfer the pattern to the pretreated epitaxial wafer; place it in a 0.5 wt% aqueous solution of tetramethylammonium hydroxide for 60 seconds for development, wash it with pure water, and dry it with nitrogen to obtain a negatively photoresist patterned film layer.

[0041] Example 2: A method for preparing a negatively photoresist patterned film layer, comprising the following steps:

[0042] Step 1: Immerse the epitaxial wafer in sulfuric acid at room temperature for 40 minutes; transfer it to hydrogen peroxide and immerse it at 55 °C for 8 minutes; wash it clean with pure water to obtain a pretreated epitaxial wafer.

[0043] Step 2: (1) Add 22 parts of photosensitive polyimide, 4 parts of POSS-based branched polyimide, 10 parts of pentaerythritol tetra-3-mercaptopropionate, and 3 parts of initiator to 108 parts of N-methylpyrrolidone in sequence and mix evenly to obtain a negative photoresist; (2) Spin-coat the negative photoresist on the surface of the pretreated epitaxial wafer; bake it at 80 °C for 20 minutes, and perform exposure treatment under the shielding of a mask. During the process: Use a contact exposure machine with a power of 15 mW / cm 2 , an exposure time of 20 s, an exposure dose of 350 mJ, and transfer the pattern to the pretreated epitaxial wafer; place it in a 0.5 wt% aqueous solution of tetramethylammonium hydroxide for 60 seconds for development, wash it with pure water, and dry it with nitrogen to obtain a negatively photoresist patterned film layer.

[0044] Example 3: A method for preparing a negatively photoresist patterned film layer, comprising the following steps:

[0045] Step 1: Immerse the epitaxial wafer in sulfuric acid at room temperature for 40 minutes; transfer it to hydrogen peroxide and immerse it at 55 °C for 8 minutes; wash it clean with pure water to obtain a pretreated epitaxial wafer.

[0046] Step 2: (1) 26 parts of photosensitive polyimide, 6 parts of POSS-based branched polyimide, 12 parts of pentaerythritol tetra-3-mercaptopropionate, and 4 parts of initiator were successively added to 132 parts of N-methylpyrrolidone and mixed evenly to obtain a negative photoresist; (2) The surface of the pretreated epitaxial wafer was spin-coated with the negative photoresist; baked at 80 °C for 20 minutes in soft baking, and exposed under the shielding of a mask plate. During the process: a contact exposure machine was used with a power of 20 mW / cm 2 , the exposure time was 15 s, the exposure dose was 350 mJ, and the pattern was transferred onto the pretreated epitaxial wafer; it was developed in a 0.5 wt% aqueous solution of tetramethylammonium hydroxide for 60 seconds, washed with pure water, and dried with nitrogen to obtain a negative photoresist patterned film layer.

[0047] Comparative Example 1: Based on Example 1, the diamine monomer was replaced with 4,4-diaminodiphenyl ether, and the preparation of POSS-based branched polyimide was adjusted, which specifically included the following steps:

[0048] Pre-preparation: Preparation of POSS-based branched polyimide: S1-1: 35 parts of 4,4-diaminodiphenyl ether and 10 parts of octaphenylaminophenyl POSS were added to 300 parts of N-methylpyrrolidone and stirred for 1 hour to obtain solution A; 19 parts of pyromellitic dianhydride and 15 parts of 4-ethynylphthalic anhydride were added to 350 parts of N-methylpyrrolidone and stirred for 1 hour to obtain solution B; S1-2: Solution A and solution B were mixed and stirred for 5 hours; heated to 60 °C and stirred for 4 hours; 15 parts of toluene were added, heated to 180 °C and stirred and reacted for 10 hours, the toluene was distilled off, and the heating was stopped after the reaction system reached 200 °C, and post-treatment was carried out to obtain POSS-based branched polyimide;

[0049] Step 1: The epitaxial wafer was soaked in sulfuric acid at room temperature for 40 minutes; transferred to hydrogen peroxide and soaked at 55 °C for 8 minutes; washed clean with pure water to obtain a pretreated epitaxial wafer;

[0050] Step 2: (1) 24 parts of photosensitive polyimide, 5 parts of POSS-based branched polyimide, 11 parts of pentaerythritol tetra-3-mercaptopropionate, and 3 parts of initiator were successively added to 120 parts of N-methylpyrrolidone and mixed evenly to obtain a negative photoresist; (2) The surface of the pretreated epitaxial wafer was spin-coated with the negative photoresist; baked at 80 °C for 20 minutes in soft baking, and exposed under the shielding of a mask plate. During the process: a contact exposure machine was used with a power of 18 mW / cm 2 , the exposure time was 18 s, the exposure dose was 350 mJ, and the pattern was transferred onto the pretreated epitaxial wafer; it was developed in a 0.5 wt% aqueous solution of tetramethylammonium hydroxide for 60 seconds, washed with pure water, and dried with nitrogen to obtain a negative photoresist patterned film layer.

[0051] Comparative Example 2: Based on Example 1, octa(aminophenyl) POSS was replaced with aminopropylheptyl POSS, and the preparation of POSS-based branched polyimide was adjusted, which specifically included the following steps:

[0052] Pre-preparation: Preparation of POSS-based branched polyimide: S1-1: Add 38 parts of diamine monomer and 4 parts of aminopropylheptyl POSS to 300 parts of N-methylpyrrolidone and stir for 1 hour to obtain solution A; add 19 parts of pyromellitic dianhydride and 15 parts of 4-ethynylphthalic anhydride to 350 parts of N-methylpyrrolidone and stir for 1 hour to obtain solution B; S1-2: Mix and stir solution A and solution B for 5 hours; heat up to 60 °C and stir for 4 hours; add 15 parts of toluene, heat up to 180 °C and stir and react for 10 hours, evaporate toluene, stop heating after the reaction system reaches 200 °C, and perform post-treatment to obtain POSS-based branched polyimide;

[0053] Step 1: Immerse the epitaxial wafer in sulfuric acid at room temperature for 40 minutes; transfer it to hydrogen peroxide and immerse it at 55 °C for 8 minutes; wash it clean with pure water to obtain a pretreated epitaxial wafer;

[0054] Step 2: (1) Add 24 parts of photosensitive polyimide, 5 parts of POSS-based branched polyimide, 11 parts of pentaerythritol tetra(3-mercaptopropionate), and 3 parts of initiator to 120 parts of N-methylpyrrolidone in sequence and mix evenly to obtain a negative photoresist; (2) Spin-coat the negative photoresist on the surface of the pretreated epitaxial wafer; bake it at 80 °C for 20 minutes, and perform exposure treatment under the shielding of a mask. During the process: use a contact exposure machine with a power of 18 mW / cm 2 , the exposure time is 18 s, the exposure dose is 350 mJ, and transfer the pattern to the pretreated epitaxial wafer; place it in a 0.5 wt% aqueous solution of tetramethylammonium hydroxide for 60 seconds for development treatment, wash it with pure water, and dry it with nitrogen to obtain a negative photoresist patterned film layer.

[0055] Comparative Example 3: Based on Example 1, increase the introduction amount of POSS-based branched polyimide, which specifically includes the following steps:

[0056] Step 1: Immerse the epitaxial wafer in sulfuric acid at room temperature for 40 minutes; transfer it to hydrogen peroxide and immerse it at 55 °C for 8 minutes; wash it clean with pure water to obtain a pretreated epitaxial wafer;

[0057] Step 2: (1) Add 20 parts of photosensitive polyimide, 9 parts of POSS-based branched polyimide, 11 parts of pentaerythritol tetra-3-mercaptopropionate, and 3 parts of initiator into 120 parts of N-methylpyrrolidone in sequence and mix evenly to obtain a negative photoresist; (2) Spin-coat the negative photoresist on the surface of the pretreated epitaxial wafer; bake it at 80 °C for 20 minutes, and perform exposure treatment under the shielding of a mask. During the process: use a contact exposure machine with a power of 18 mW / cm 2 , the exposure time is 18 s, the exposure dose is 350 mJ, and transfer the pattern to the pretreated epitaxial wafer; place it in a 0.5 wt% aqueous solution of tetramethylammonium hydroxide for 60 seconds for development, wash with pure water, and dry with nitrogen to obtain a negatively photoresist patterned film layer.

[0058] Comparative Example 4: Based on Example 1, directly introduce a small molecule photoinitiator, which specifically includes the following steps:

[0059] Step 1: Immerse the epitaxial wafer in sulfuric acid at room temperature for 40 minutes; transfer it to hydrogen peroxide and immerse it at 55 °C for 8 minutes; wash it clean with pure water to obtain a pretreated epitaxial wafer;

[0060] Step 2: (1) Add 24 parts of photosensitive polyimide, 5 parts of POSS-based branched polyimide, 11 parts of pentaerythritol tetra-3-mercaptopropionate, 0.3 parts of 4-chlorobenzophenone, and 0.2 parts of chlorothioxanthone into 120 parts of N-methylpyrrolidone in sequence and mix evenly to obtain a negative photoresist; (2) Spin-coat the negative photoresist on the surface of the pretreated epitaxial wafer; bake it at 80 °C for 20 minutes, and perform exposure treatment under the shielding of a mask. During the process: use a contact exposure machine with a power of 18 mW / cm 2 , the exposure time is 18 s, the exposure dose is 350 mJ, and transfer the pattern to the pretreated epitaxial wafer; place it in a 0.5 wt% aqueous solution of tetramethylammonium hydroxide for 60 seconds for development, wash with pure water, and dry with nitrogen to obtain a negatively photoresist patterned film layer.

[0061] Comparative Example 5: Based on Example 1, change the exposure method, which specifically includes the following steps:

[0062] Step 1: Immerse the epitaxial wafer in sulfuric acid at room temperature for 40 minutes; transfer it to hydrogen peroxide and immerse it at 55 °C for 8 minutes; wash it clean with pure water to obtain a pretreated epitaxial wafer;

[0063] Step 2: (1) 24 parts of photosensitive polyimide, 5 parts of POSS-based branched polyimide, 11 parts of pentaerythritol tetra-3-mercaptopropionate, and 3 parts of initiator were successively added to 120 parts of N-methylpyrrolidone and mixed evenly to obtain a negative photoresist; (2) The surface of the pretreated epitaxial wafer was spin-coated with the negative photoresist; baked at 80 °C for 20 minutes, and exposed under the shielding of a mask. During the process: a step-and-repeat exposure machine was used, with a power of 1000 mW / cm 2 , step scanning, the exposure time for each point was 0.3 s, the exposure dose was 350 mJ, and the pattern was transferred onto the pretreated epitaxial wafer; it was developed in a 0.5 wt% aqueous solution of tetramethylammonium hydroxide for 60 seconds, washed with pure water, and dried with nitrogen to obtain a negatively patterned photoresist film layer.

[0064] Performance Test 1: The relevant substances of the examples and comparative examples were subjected to performance tests. The coating thickness of the negative photoresist in the implementation was 10 μm. (1) The film thickness before and after development in the exposed area was measured, and the film retention rate was calculated; (2) A 2-μm copper layer was evaporated on the surface of the negatively patterned photoresist film layer to detect the adhesion between them. The obtained data are shown in the following table:

[0065]

[0066] Conclusion: From the data in the above table, it can be seen that: by optimizing the components and related processes in this application, the quality of the negatively patterned photoresist film layer was effectively improved, and a patterned film layer with low curing shrinkage, high film retention rate, and excellent adhesion to metals was prepared. From the data of Comparative Examples 1 to 4, it can be seen that in Comparative Example 1, 4,4-diaminodiphenyl ether was used as the diamine to prepare POSS-based branched polyimide, which reduced its flexible chain segments and pyridine groups, resulting in a decline in related properties; in Comparative Example 2, aminopropylheptyl POSS was used to replace octaphenylaminophenyl POSS, which reduced the branching toughness and had a high curing stress, resulting in cracks and a decrease in the film retention rate after development; in Comparative Example 3, due to an increase in the introduction amount of octaphenylaminophenyl POSS, crosslinking was excessive, resulting in an increase in stress and a decline in related properties; in Comparative Examples 4 and 5, due to the use of a small molecule photoinitiator and the exposure method, the photocuring performance decreased, resulting in a decline in the quality of the negatively patterned photoresist film layer and a decrease in the film retention rate.

[0067] Finally, it should be noted that: the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a negative photoresist patterned film layer, characterized in that: The following steps are involved: Step 1: washing the epitaxial wafer with acid, hydrogen peroxide and pure water in sequence to obtain a pre-treated epitaxial wafer; Step 2: Spin-coating a negative photoresist on the surface of the pretreated epitaxial wafer; Soft bake, exposure processing under the cover of the mask, transfer the pattern to the pre-processed epitaxial wafer; Development treatment, pure water cleaning, and nitrogen drying to obtain a negative photoresist patterned film layer; The raw materials of the negative photoresist include the following components: by mass, 22 to 26 parts of photosensitive polyimide, 4 to 6 parts of POSS-based branched polyimide, 10 to 12 parts of mercapto monomer, 3 to 4 parts of initiator, and 108 to 132 parts of organic solvent; The preparation method of the POSS-based branched polyimide comprises the following steps: S1-1: adding a diamine monomer and octa-p-aminophenyl POSS to N-methylpyrrolidone and stirring for 0.5-1 hour to obtain a solution A; adding pyromellitic anhydride and 4-ethynylphthalic anhydride to N-methylpyrrolidone and stirring for 0.5-1 hour to obtain a solution B; S1-2: mixing solution A and solution B and stirring for 4-6 hours; heating to 60-65° C. and stirring for 2-4 hours; adding toluene, heating to 180-185° C. and stirring for 10-12 hours, distilling off toluene, stopping heating after the reaction system reaches 200° C., post-processing, and obtaining the POSS-based branched polyimide; The preparation method of the diamine monomer is as follows: (1) Under an inert gas, pyridine-2,6-dicarbaldehyde and 4-vinylaniline with a molar ratio of 1:2 are successively added to ethanol, and the mixture is stirred and reacted at 58-60 °C for 4-6 hours, followed by post-treatment to obtain a divinyl monomer; (2) The divinyl monomer and cysteamine with a mass ratio of 1:0.65-0.7 are added to tetrahydrofuran, and azobisisobutyronitrile is added; under ultraviolet light irradiation, the light irradiance is set to 100-150 mW / cm 2 , and the mixture is stirred and reacted for 2-4 hours, followed by post-treatment to obtain the diamine monomer; The preparation method of the initiator comprises the following steps: S2-1: uniformly mixing divinyl monomer, acrylamide, allyl succinic anhydride and hydroxyethyl methacrylate to obtain a mixed monomer; adding silica and methacryloxypropyl trimethoxysilane to a 5-10wt% ethanol aqueous solution, and uniformly dispersing by ultrasonication; adding the mixed monomer and azobisisobutyronitrile, reacting at 70-75°C for 3-5 hours, and post-treating to obtain composite silica; S2-2: adding the composite silica to tetrahydrofuran under light protection, and adding chlorothioxanthone and 4-chlorobenzophenone; stirring at 50-55°C for 5-6 hours under inert gas, adding acryloyl chloride and hydroquinone and continuing stirring for 10-12 hours; post-treating to obtain an initiator; During the exposure process, a contact exposure machine is used with a power of 15 - 20 mW / cm 2 , an exposure time of 15 - 20 s, and a total exposure dose of 300 - 400 mJ.

2. The preparation method of a negative photoresist patterning film layer according to claim 1, characterized in that: The raw materials of the POSS-based branched polyimide include the following substances: by mass, 10 parts of octa-p-aminophenyl POSS, 36-40 parts of diamine monomers, 15-20 parts of pyromellitic anhydride, 12-18 parts of 4-ethynylphthalic anhydride, 10-15 parts of toluene, and 600-650 parts of N-methylpyrrolidone.

3. The method for preparing a negative photoresist patterned film layer according to claim 1, wherein: The raw materials of the composite silicon dioxide include the following components: by mass, 10 parts of silicon dioxide, 10-15 parts of divinyl monomer, 10-15 parts of acrylamide, 4-5 parts of allyl succinic anhydride, 4-5 parts of hydroxyethyl methacrylate, 1-2 parts of methacryloxypropyl trimethoxysilane, and 0.1-0.5 parts of azobisisobutyronitrile; The raw materials of the initiator include the following components: by mass, 10 parts of composite silicon dioxide, 0.5-0.6 parts of chlorine-containing thioxanthone, 0.5-0.6 parts of 4-chlorobenzophenone, 0.8-1 parts of acryloyl chloride, and 0.04-0.05 parts of hydroquinone.

4. The preparation method of a negative photoresist patterned film layer according to claim 1, wherein: During the soft baking process, it is baked at 80-85°C for 15-30 minutes under an inert gas.

5. The preparation method of a negative photoresist patterned film layer according to claim 1, wherein: During the development process, the developer is an aqueous solution of tetramethylammonium hydroxide at 0.5-1.5 wt%.

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