Preparation method of negative photoresist patterned film layer

Abstract

The invention discloses a preparation method of a negative photoresist patterned film layer, and relates to the technical field of photoresist materials. The preparation method comprises the following steps: 1, sequentially carrying out acid pickling, hydrogen peroxide washing and pure water cleaning on an epitaxial wafer to obtain a pretreated epitaxial wafer; 2, spin-coating negative photoresist on the surface of the pretreated epitaxial wafer; carrying out soft baking, carrying out exposure treatment under the shielding of a mask, and transferring a pattern to the preprocessed epitaxial wafer; and carrying out developing treatment, pure water cleaning and nitrogen drying to obtain the negative photoresist patterned film layer. The negative photoresist is prepared from the following raw material components in parts by mass: 22 to 26 parts of photosensitive polyimide, 4 to 6 parts of POSS (Polyhedral Oligomeric Silsesquioxane)-based branched polyimide, 10 to 12 parts of sulfydryl monomer, 3 to 4 parts of initiator and 108 to 132 parts of organic solvent. According to the invention, the quality of the negative photoresist patterned film layer is effectively improved by optimizing the components and the soft baking and exposure process.

Description

Technical Field

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

[0002] Photolithography is one of the key technologies in semiconductor manufacturing. Generally, the pattern on the mask is transferred to the substrate through photoresist, which is the basis for the manufacture of microelectronic devices and integrated circuits. Photoresists are generally divided into positive photoresists and negative photoresists. After the negative photoresist is exposed, the exposed area is cured and cross-linked, and the non-exposed area is dissolved by the developer to complement the mask pattern.

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

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

[0005] The object 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 technology.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions: A method for preparing a negative photoresist patterned film layer comprises the following steps: 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-coat the surface of the pre-treated epitaxial wafer with negative photoresist; soft bake, expose under the cover of a mask, and transfer the pattern to the pre-treated epitaxial wafer; develop, clean with pure water, and dry with nitrogen to obtain a negative photoresist patterned film layer.

[0007] In the pickling process, the wafer is immersed in sulfuric acid at room temperature for 30 to 60 minutes; in the hydrogen peroxide washing process, the wafer is immersed 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 residual contaminants on the surface of the epitaxial wafer.

[0008] More optimally, 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 thiol monomer, 3 to 4 parts of initiator, and 108 to 132 parts of organic solvent.

[0009] More optimally, the preparation method of the POSS-based branched polyimide comprises the following steps: S1-1: Add diamine monomer and octa-p-aminophenyl POSS to N-methylpyrrolidone and stir for 0.5 to 1 hour to obtain solution A; add pyromellitic anhydride and 4-ethynylphthalic anhydride to N-methylpyrrolidone and stir for 0.5 to 1 hour to obtain solution B; S1-2: Mix solution A and solution B and stir for 4 to 6 hours; heat to 60 to 65°C and stir for 2 to 4 hours; add toluene, heat to 180 to 185°C and stir for 10 to 12 hours, evaporate toluene, stop heating after the reaction system reaches 200°C, and post-treat to obtain POSS-based branched polyimide.

[0010] More optimally, the raw materials of the POSS-based branched polyimide include the following substances: by mass, 10 parts of octa-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.

[0011] More optimally, the preparation method of the diamine monomer is as follows: (1) under inert gas, pyridine-2,6-dicarboxaldehyde and 4-vinylaniline in a molar ratio of 1:2 are added to ethanol in sequence, stirred at 58-60°C for 4-6 hours, and post-treated to obtain a divinyl monomer; (2) divinyl monomer and cysteamine in a mass ratio of 1:0.65-0.7 are added to tetrahydrofuran, and azobisisobutyronitrile is added; under ultraviolet light, the light irradiance is set to 100-150 mW / cm 2 , stirring and reacting for 2 to 4 hours, and post-processing to obtain a diamine monomer.

[0012] More optimally, the method for preparing the initiator comprises the following steps: S2-1: Divinyl monomer, acrylamide, allyl succinic anhydride and hydroxyethyl methacrylate are mixed evenly to obtain a mixed monomer; silica and methacryloxypropyltrimethoxysilane are added to a 5-10wt% ethanol aqueous solution, and ultrasonically dispersed evenly; the mixed monomer and azobisisobutyronitrile are added, reacted at 70-75°C for 3-5 hours, and post-treated to obtain composite silica; S2-2: In the dark, add the composite silica to tetrahydrofuran, add chlorothioxanthone and 4-chlorobenzophenone; under inert gas, stir at 50-55°C for 5-6 hours, add acryloyl chloride and hydroquinone and continue stirring for 10-12 hours; post-treat to obtain an initiator.

[0013] More optimally, 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 methacryloxypropyltrimethoxysilane, 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.

[0014] More optimally, during the soft baking process, the baking is carried out at 80-85° C. for 15-30 minutes under an inert gas.

[0015] Preferably, during the exposure process, a contact exposure machine is used with a power of 15-20 mW / cm 2 The exposure time is 15~20s, and the total exposure is 300~400mJ.

[0016] More optimally, during the development process, the developer is a 0.5-1.5 wt % tetramethylammonium hydroxide aqueous solution.

[0017] Compared with the prior art, the invention has the following beneficial effects: by introducing POSS-based branched polyimide, the subsequent metal adhesion is promoted on the basis of enhancing crosslinking and heat resistance; the composite modified initiator is coordinated to improve the uniformity of photocuring and the rate of photopolymerization; and the subsequent soft baking and exposure treatment processes are combined to effectively buffer the curing stress and reduce the curing shrinkage of the film layer. In this way, the quality of the negative photoresist patterned film layer is comprehensively improved.

[0018] In the scheme, the POSS-based branched polyimide is prepared with octa-aminophenyl POSS as the branchable center, diamine-containing monomers and pyromellitic anhydride as the basic reaction segments, and 4-ethynylphthalic anhydride as the end capping. Among them, due to the introduction of the Si-O bond contained in POSS and its special structure, 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 heat release, photopolymerization sensitivity, and can reduce the situation of incomplete curing.

[0019] 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 terminal unsaturated bonds effectively increase the cross-linking; at the same time, due to its branched structure, the toughness of the film layer is improved, which can effectively buffer the curing stress and reduce the curing shrinkage, thereby enhancing the patterning quality; and the branched structure also improves the interface adhesion and intermolecular cohesion, thereby effectively improving the interface bonding between the patterned film layer and the epitaxial wafer.

[0020] Among them, the diamine monomer is based on pyridine-2,6-dicarboxaldehyde. The aldehyde group reacts with the amino group to form a divinyl monomer, and then the alkenyl group reacts with the thiol group to graft cysteamine. The pyridine group not only improves the thermal stability, but also improves the adhesion to the subsequent metal because it can coordinate with metal ions. The grafted cysteamine contains sulfur-containing groups and short carbon chains, which can buffer the curing stress and thus reduce the curing shrinkage.

[0021] In the scheme, in order to suppress the mobility of common small molecule initiators and reduce the unevenness and incompleteness of curing. In the scheme, divinyl monomer, acrylamide, allyl succinic anhydride, and hydroxyethyl methacrylate are copolymerized as monomers, and silica modified with methacryloxypropyltrimethoxysilane is introduced therein to form a composite silica, and the amino groups on its surface are first grafted with chlorothioxanthone and 4-chlorobenzophenone; and then grafted with acryloyl chloride to obtain. Among them, chlorothioxanthone and 4-chlorobenzophenone are small molecule initiators, and the initiators have been modified in this way, which can effectively suppress the mobility of small molecules and improve the curing performance. On the other hand, the silicon dioxide contained can also produce Rayleigh scattering effect and promote photocuring. At the same time, the initiator can cross-link with the main material to produce reaction compatibility. The divinyl monomer contained has a similar chain segment to the diamine monomer in the POSS-based branched polyimide, producing similar compatibility. 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.

[0022] In the scheme, the negative photoresist after soft baking can be attached to the surface of the epitaxial wafer as a coating. The optimization of the exposure method can effectively increase the diffusion distance of free radicals, thereby increasing the degree of cross-linking and the film retention rate, thereby improving the quality of imaging. On the other hand, when developing in an alkaline solution, since the negative photoresist contains anhydride groups and has degradation ability, the cured photoresist is 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. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] It should be noted that the following parts are calculated by mass, and the purchase manufacturers of all raw materials involved in the present invention are exemplary without any special restrictions: In the following embodiments, the CAS number of 4,4-(butane-1,3-diyne-1,4-diyl)diphenylamine is 30405-78-8; the CAS number of 4,4-diaminodiphenyl ether is 101-80-4; the CAS number of pyridine-2,6-dicarboxaldehyde is 5431-44-7; the CAS number of 4-vinylaniline is 1520 -21-4; the CAS number of cysteamine is 60-23-1; the CAS number of pyromellitic anhydride is 89-32-7; the CAS number of octa-p-aminophenyl 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 allylsuccinic anhydride is 7539-12-0; the CAS number of 4-chlorobenzophenone is 134-85-0. The above and other raw materials are commercially available.

[0025] Preparation of chlorinated thioxanthone: (1) adding thiosalicylic acid and phenoxyacetic acid in a molar ratio of 1:1.1 to toluene in sequence, adding p-toluenesulfonic acid, stirring and reacting at 110°C for 10 hours; evaporating the solvent, post-treating, and obtaining carboxylated thioxanthone; (2) adding carboxylated thioxanthone to a mixed solvent of thionyl chloride and dimethylformamide, wherein the mass ratio of thionyl chloride to dimethylformamide is 20:1, stirring at 70°C for 18 hours, post-treating, and obtaining chlorinated thioxanthone; Preparation of diamine monomer: (1) under inert gas, pyridine-2,6-dicarboxaldehyde and 4-vinylaniline in a molar ratio of 1:2 were added to ethanol in sequence, stirred at 60°C for 5 hours, and post-treated to obtain divinyl monomer; (2) divinyl monomer and cysteamine in a mass ratio of 1:0.68 were added to tetrahydrofuran, and azobisisobutyronitrile (accounting for 0.5wt% of the divinyl monomer) was added; under ultraviolet light, the light irradiance was set to 120mW / cm 2 , stirring and reacting for 4 hours, and post-processing to obtain a diamine monomer.

[0026] Preparation of photosensitive polyimide: Under a nitrogen atmosphere, 14 parts of 4,4-diaminodiphenyl ether and 8 parts of 4,4-(butane-1,3-diyne-1,4-diyl)diphenylamine were added to 200 parts of N-methylpyrrolidone, and 22 parts of pyromellitic anhydride and 7 parts of 4-ethynylphthalic anhydride were added; the mixture was stirred in an ice-water bath for 12 hours, quinoline catalyst was added, the temperature was raised to 190°C, and the reaction was stirred for 5 hours. During the process, nitrogen was used to remove the water removed by imidization, and the mixture was cooled to room temperature, poured into anhydrous ethanol, washed, and dried to obtain a photosensitive polyimide.

[0027] Preparation of POSS-based branched polyimide: S1-1: Add 38 parts of diamine monomer and 10 parts of octa-p-aminophenyl POSS to 300 parts of N-methylpyrrolidone and stir for 1 hour to obtain solution A; add 19 parts of pyromellitic anhydride 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 solution A and solution B and stir for 5 hours; heat to 60°C and stir for 4 hours; add 15 parts of toluene, heat to 180°C and stir to react for 10 hours, evaporate to remove toluene, stop heating after the reaction system reaches 200°C, post-treat to obtain POSS-based branched polyimide.

[0028] Preparation of initiator: S2-1: 15 parts of divinyl monomer, 12 parts of acrylamide, 5 parts of allyl succinic anhydride, and 5 parts of hydroxyethyl methacrylate are mixed uniformly to obtain a mixed monomer; 10 parts of silica and 1.5 parts of methacryloyloxypropyltrimethoxysilane are added to a 5wt% ethanol aqueous solution, and ultrasonically dispersed uniformly; the mixed monomer and 0.2 parts of azobisisobutyronitrile are added, reacted at 70°C for 4 hours, and post-treated to obtain composite silica; S2-2: Under light protection, 10 parts of composite silica are added to 50 parts of tetrahydrofuran, and 0.4 parts of chlorine-containing thioxanthone and 0.6 parts of 4-chlorobenzophenone are added; under nitrogen gas, stirred at 50°C for 6 hours, 1 part of acryloyl chloride and 0.05 parts of hydroquinone are added and stirring is continued for 12 hours; post-treated to obtain an initiator.

[0029] Embodiment 1: A method for preparing a negative photoresist patterned film layer, comprising the following steps: Step 1: Soak the epitaxial wafer in sulfuric acid at room temperature for 40 minutes; transfer to hydrogen peroxide and soak at 55°C for 8 minutes; rinse with pure water to obtain a pretreated epitaxial wafer; 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 are added to 120 parts of N-methylpyrrolidone in sequence and mixed evenly to obtain a negative photoresist; (2) The surface of the pretreated epitaxial wafer is spin-coated with negative photoresist; the wafer is soft-baked at 80°C for 20 minutes, and exposed under the mask. During the process: a contact exposure machine is used with a power of 18 mW / cm 2 The exposure time is 18s, the exposure amount is 350mJ, and the pattern is transferred to the pretreated epitaxial wafer; it is placed in a 0.5wt% tetramethylammonium hydroxide aqueous solution for development for 60 seconds, cleaned with pure water, and dried with nitrogen to obtain a negative photoresist patterned film layer.

[0030] Embodiment 2: A method for preparing a negative photoresist patterned film layer, comprising the following steps: Step 1: Soak the epitaxial wafer in sulfuric acid at room temperature for 40 minutes; transfer to hydrogen peroxide and soak at 55°C for 8 minutes; rinse with pure water to obtain a pretreated epitaxial wafer; Step 2: (1) 22 parts of photosensitive polyimide, 4 parts of POSS-based branched polyimide, 10 parts of pentaerythritol tetra-3-mercaptopropionate, and 3 parts of initiator are added to 108 parts of N-methylpyrrolidone and mixed evenly to obtain a negative photoresist; (2) The surface of the pretreated epitaxial wafer is spin-coated with negative photoresist; the wafer is soft-baked at 80°C for 20 minutes, and exposed under the mask. During the process: a contact exposure machine is used with a power of 15 mW / cm 2 , the exposure time is 20s, the exposure amount is 350mJ, and the pattern is transferred to the pretreated epitaxial wafer; it is placed in a 0.5wt% tetramethylammonium hydroxide aqueous solution for development for 60 seconds, cleaned with pure water, and dried with nitrogen to obtain a negative photoresist patterned film layer.

[0031] Embodiment 3: A method for preparing a negative photoresist patterned film layer, comprising the following steps: Step 1: Soak the epitaxial wafer in sulfuric acid at room temperature for 40 minutes; transfer to hydrogen peroxide and soak at 55°C for 8 minutes; rinse with pure water to obtain a pretreated epitaxial wafer; 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 are added to 132 parts of N-methylpyrrolidone in sequence and mixed evenly to obtain a negative photoresist; (2) The surface of the pretreated epitaxial wafer is spin-coated with negative photoresist; the wafer is soft-baked at 80°C for 20 minutes, and exposed under the mask. During the process: a contact exposure machine is used with a power of 20 mW / cm 2, the exposure time is 15s, the exposure amount is 350mJ, and the pattern is transferred to the pretreated epitaxial wafer; it is placed in a 0.5wt% tetramethylammonium hydroxide aqueous solution for development for 60 seconds, cleaned with pure water, and dried with nitrogen to obtain a negative photoresist patterned film layer.

[0032] Comparative Example 1: Based on Example 1, the diamine monomer is replaced with 4,4-diaminodiphenyl ether, and the preparation of the POSS-based branched polyimide is adjusted, specifically comprising the following steps: Pre-preparation: Preparation of POSS-based branched polyimide: S1-1: Add 35 parts of 4,4-diaminodiphenyl ether and 10 parts of octa-p-aminophenyl POSS to 300 parts of N-methylpyrrolidone and stir for 1 hour to obtain solution A; add 19 parts of pyromellitic anhydride 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 solution A and solution B and stir for 5 hours; heat to 60°C and stir for 4 hours; add 15 parts of toluene, heat to 180°C and stir for 10 hours, evaporate toluene, stop heating after the reaction system reaches 200°C, post-treat to obtain POSS-based branched polyimide; Step 1: Soak the epitaxial wafer in sulfuric acid at room temperature for 40 minutes; transfer to hydrogen peroxide and soak at 55°C for 8 minutes; rinse with pure water to obtain a pretreated epitaxial wafer; 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 are added to 120 parts of N-methylpyrrolidone in sequence and mixed evenly to obtain a negative photoresist; (2) The surface of the pretreated epitaxial wafer is spin-coated with negative photoresist; the wafer is soft-baked at 80°C for 20 minutes, and exposed under the mask. During the process: a contact exposure machine is used with a power of 18 mW / cm 2 The exposure time is 18s, the exposure amount is 350mJ, and the pattern is transferred to the pretreated epitaxial wafer; it is placed in a 0.5wt% tetramethylammonium hydroxide aqueous solution for development for 60 seconds, cleaned with pure water, and dried with nitrogen to obtain a negative photoresist patterned film layer.

[0033] Comparative Example 2: Based on Example 1, the eight-p-aminophenyl POSS was replaced with aminopropylheptyl POSS, and the preparation of the POSS-based branched polyimide was adjusted, specifically comprising the following steps: 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 anhydride 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 solution A and solution B and stir for 5 hours; heat to 60°C and stir for 4 hours; add 15 parts of toluene, heat to 180°C and stir for 10 hours, evaporate toluene, stop heating after the reaction system reaches 200°C, post-treat to obtain POSS-based branched polyimide; Step 1: Soak the epitaxial wafer in sulfuric acid at room temperature for 40 minutes; transfer to hydrogen peroxide and soak at 55°C for 8 minutes; rinse with pure water to obtain a pretreated epitaxial wafer; 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 are added to 120 parts of N-methylpyrrolidone in sequence and mixed evenly to obtain a negative photoresist; (2) The surface of the pretreated epitaxial wafer is spin-coated with negative photoresist; the wafer is soft-baked at 80°C for 20 minutes, and exposed under the mask. During the process: a contact exposure machine is used with a power of 18 mW / cm 2 The exposure time is 18s, the exposure amount is 350mJ, and the pattern is transferred to the pretreated epitaxial wafer; it is placed in a 0.5wt% tetramethylammonium hydroxide aqueous solution for development for 60 seconds, cleaned with pure water, and dried with nitrogen to obtain a negative photoresist patterned film layer.

[0034] Comparative Example 3: Based on Example 1, the amount of octa-p-aminophenyl POSS introduced was increased, specifically comprising the following steps: Step 1: Soak the epitaxial wafer in sulfuric acid at room temperature for 40 minutes; transfer to hydrogen peroxide and soak at 55°C for 8 minutes; rinse with pure water to obtain a pretreated epitaxial wafer; Step 2: (1) 20 parts of photosensitive polyimide, 9 parts of POSS-based branched polyimide, 11 parts of pentaerythritol tetra-3-mercaptopropionate, and 3 parts of initiator are added to 120 parts of N-methylpyrrolidone and mixed evenly to obtain a negative photoresist; (2) The surface of the pretreated epitaxial wafer is spin-coated with negative photoresist; the wafer is soft-baked at 80°C for 20 minutes, and exposed under the mask. During the process: a contact exposure machine is used with a power of 18 mW / cm 2 The exposure time is 18s, the exposure amount is 350mJ, and the pattern is transferred to the pretreated epitaxial wafer; it is placed in a 0.5wt% tetramethylammonium hydroxide aqueous solution for development for 60 seconds, cleaned with pure water, and dried with nitrogen to obtain a negative photoresist patterned film layer.

[0035] Comparative Example 4: Based on Example 1, a small molecule photoinitiator is directly introduced, specifically comprising the following steps: Step 1: Soak the epitaxial wafer in sulfuric acid at room temperature for 40 minutes; transfer to hydrogen peroxide and soak at 55°C for 8 minutes; rinse with pure water to obtain a pretreated epitaxial wafer; Step 2: (1) 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 are sequentially added to 120 parts of N-methylpyrrolidone and mixed evenly to obtain a negative photoresist; (2) the surface of the pretreated epitaxial wafer is spin-coated with the negative photoresist; the wafer is soft-baked at 80°C for 20 minutes, and exposed under the mask. During the process: a contact exposure machine is used with a power of 18 mW / cm 2 The exposure time is 18s, the exposure amount is 350mJ, and the pattern is transferred to the pretreated epitaxial wafer; it is placed in a 0.5wt% tetramethylammonium hydroxide aqueous solution for development for 60 seconds, cleaned with pure water, and dried with nitrogen to obtain a negative photoresist patterned film layer.

[0036] Comparative Example 5: Based on Example 1, the exposure method is changed, specifically comprising the following steps: Step 1: Soak the epitaxial wafer in sulfuric acid at room temperature for 40 minutes; transfer to hydrogen peroxide and soak at 55°C for 8 minutes; rinse with pure water to obtain a pretreated epitaxial wafer; 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 and mix well to obtain a negative photoresist; (2) Spin-coat the surface of the pretreated epitaxial wafer with the negative photoresist; soft bake at 80°C for 20 minutes, and expose under the mask. During the process: use a stepper exposure machine with a power of 1000mW / cm 2 , step scanning, exposure time of each point is 0.3s, exposure amount is 350mJ, and the pattern is transferred to the pretreated epitaxial wafer; it is placed in a 0.5wt% tetramethylammonium hydroxide aqueous solution for development for 60 seconds, cleaned with pure water, and dried with nitrogen to obtain a negative photoresist patterned film layer.

[0037] Performance test 1: The relevant materials of the embodiment and the comparative example were subjected to performance tests. The negative photoresist coating thickness in the embodiment is 10 μm. (1) The film thickness before and after development of the exposure area was measured, and the film retention rate was calculated; (2) A 2 μm copper layer was evaporated on the surface of the negative photoresist patterned film layer, and the adhesion was tested. The obtained data are shown in the following table:

[0038] Conclusion: From the data in the above table, it can be seen that the present application effectively improves the quality of the negative photoresist patterned film layer by optimizing the components and related processes, and prepares a patterned film layer with low curing shrinkage, high film retention rate, and excellent adhesion to metal. From the data of Comparative Examples 1 to 4, it can be seen that in Comparative Example 1, 4,4-diaminodiphenyl ether is used as a diamine to prepare POSS-based branched polyimide, which reduces its flexible chain break and pyridine group, resulting in a decrease in related performance; in Comparative Example 2, aminopropylheptyl POSS is used to replace octa-aminophenyl POSS, which reduces the branching toughness and the curing stress is high, resulting in cracks, thereby reducing the film retention rate after development; in Comparative Example 3, due to the increase in the amount of octa-aminophenyl POSS introduced, excessive crosslinking occurs, resulting in increased stress, which reduces related performance; in Comparative Examples 4 and 5, due to the use of small molecule photoinitiators and exposure methods, the photocuring performance is reduced, resulting in a decrease in the quality of the negative photoresist patterned film layer and a decrease in the film retention rate.

[0039] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in 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; The negative photoresist patterned film layer is obtained by developing, washing with pure water and drying with nitrogen.

2. The method for preparing a negative photoresist patterned film layer according to claim 1, characterized in that: The raw materials of the negative photoresist include the following components: by mass, 22-26 parts of photosensitive polyimide, 4-6 parts of POSS-based branched polyimide, 10-12 parts of mercapto monomer, 3-4 parts of initiator, and 108-132 parts of organic solvent.

3. The method for preparing a negative photoresist patterned film layer according to claim 2, characterized in that: The preparation method of the POSS-based branched polyimide comprises the following steps: S1-1: Add diamine monomer and octa-p-aminophenyl POSS to N-methylpyrrolidone and stir for 0.5 to 1 hour to obtain solution A; add pyromellitic anhydride and 4-ethynylphthalic anhydride to N-methylpyrrolidone and stir for 0.5 to 1 hour to obtain solution B; S1-2: Mix solution A and solution B and stir for 4 to 6 hours; heat to 60 to 65°C and stir for 2 to 4 hours; add toluene, heat to 180 to 185°C and stir for 10 to 12 hours, evaporate toluene, stop heating after the reaction system reaches 200°C, and post-treat to obtain POSS-based branched polyimide.

4. The method for preparing a negative photoresist patterned film layer according to claim 3, 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.

5. The method for preparing a negative photoresist patterned film layer according to claim 3, characterized in that: The preparation method of the diamine monomer is as follows: (1) under inert gas, pyridine-2,6-dicarboxaldehyde and 4-vinylaniline in a molar ratio of 1:2 are added to ethanol in sequence, stirred at 58-60° C. for reaction for 4-6 hours, and post-treated to obtain a divinyl monomer; (2) divinyl monomer and cysteamine in a mass ratio of 1:0.65-0.7 are added to tetrahydrofuran, and azobisisobutyronitrile is added; under ultraviolet light, the light irradiance is set to 100-150 mW / cm 2 , stirring and reacting for 2 to 4 hours, and post-processing to obtain a diamine monomer.

6. The method for preparing a negative photoresist patterned film layer according to claim 2, characterized in that: The preparation method of the initiator comprises the following steps: S2-1: Divinyl monomer, acrylamide, allyl succinic anhydride and hydroxyethyl methacrylate are mixed evenly to obtain a mixed monomer; silica and methacryloxypropyltrimethoxysilane are added to a 5-10wt% ethanol aqueous solution, and ultrasonically dispersed evenly; the mixed monomer and azobisisobutyronitrile are added, reacted at 70-75°C for 3-5 hours, and post-treated to obtain composite silica; S2-2: In the dark, add the composite silica to tetrahydrofuran, add chlorothioxanthone and 4-chlorobenzophenone; under inert gas, stir at 50-55°C for 5-6 hours, add acryloyl chloride and hydroquinone and continue stirring for 10-12 hours; post-treat to obtain an initiator.

7. The method for preparing a negative photoresist patterned film layer according to claim 6, characterized in that: 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.

8. The method for preparing a negative photoresist patterned film layer according to claim 1, characterized in that: During the soft baking process, the baking is carried out at 80-85° C. for 15-30 minutes under an inert gas.

9. The method for preparing a negative photoresist patterned film layer according to claim 1, characterized in that: During the exposure process, a contact exposure machine is used with a power of 15-20 mW / cm 2 , exposure time is 15~20s, and total exposure is 300~400mJ.

10. The method for preparing a negative photoresist patterned film layer according to claim 1, characterized in that: During the development process, the developer is a 0.5-1.5 wt % tetramethylammonium hydroxide aqueous solution.

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